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Selasa, 23 Oktober 2012

perawatan paska infark (IMA)


PERAWATAN PASKA INFARK MIOCARD




PENDAHULUAN
            Infark Miokard Akut ( IMA ) merupakan salah satu kegawatan kardiovaskuler yang dapat menyebabkan resiko kematian tinggi pada penderitanya. Kira – kira setengah dari kematian mereka terjadi dalam waktu 1 – 2 jam dari gejala awitan sebelum mencapai rumah sakit.
            IMA menempati peringkat pertama sebagai penyebab kematian di Amerika Serikat dilaporkan setiap tahunnya terdapat sekitar 1,5 juta pasien terkena serangan jantung. Melihat besarnya statistic morbiditas dan mortalitas yang terjadi maka banyak usaha yang dilakukan untuk kemajuan dalam mendiagnosis, penatalaksanaan dan terapi pada kegawatan kardiovaskuler ini. Dalam hal ini perawat unit kritis perlu memainkan peran utama dalam menurunkan mortalitas penyakit jantung dengan meningkatkan ketrampilan mengkaji, intervensi secara cepat dan tepat serta mengevaluasi ulang hasil intervensi.
            Pemantauan jantung secara kontinue diharapkan dapat menurunkan jumlah kematian yang disebabkan oleh disritmia jantung. Setelah serangan IMA, penderita harus dipantau baik keluhan maupun gambaran tanda – tanda vital yang terjadi. Adapun komplikasi yang terjadi dari IMA yang mampu menyebabkan kematian adalah gagal jantung Ventrikel kiri. Untuk itu ada 3 tiga faktor ( kriteria ) bagi pasien diijinkan keluar dari ruang perawatan kritis dan dirawat diruang perawatan yaitu Derajat fungsi ventrikel kiri, frekuensi denyut ventrikel premature ( PVC ) dan Iskemia spontan atau karena aktifitas. Apabila keluhan penderita dan gejala disritmia dapat diminimalkan atau hilang maka klien boleh dipindahkan diruangan dan disiapkan untuk pulang.
              Keberhasilan dari penangganan IMA ini dengan kerjasama keluarga dan klien dalam beradaptasi secara bertahap baik dari segi fisiologis jantung, psikologis social dan vocasional. Hal tersebut dapat diberikan dengan pemberian asuhan perawatan dan program rehabilitasi jantung yang komprehensif. Dengan harapan pada tujuan akhirnya klien dapat kembali ke kehidupan aktif dan produktif.



PENGERTIAN INFARK MIOKARD AKUT
            IMA didefiniskan sebagai nekrosis miocard yang disebabkan oleh oklusi arteri koroner akut dengan iskemia berkepanjangan yang pada akhirnya menimbulkan tidak adekuatnya pasokan darah yang mengakibatkan kerusakan sel dan kematian jaringan (infark) miokard (Perki, 2004)
            Terjadinya sumbatan arteri koroner pada IMA sebagian besar disebabkan oleh rupture plak ateroma pada arteri koroner yang diikuti terjadinya trombosis, vasokontriksi, reaksi inflamasi dan mikroembolisasi distal. Kadang –kadang sumbatan akut ini dapat pula disebabkan oleh spasme arteri koroner, emboli atau vaskulitis.

PATOFISIOLOGI INFARK MIOKARD AKUT
            Oklusi arteri koroner dengan iskemia yang berkepanjangan menyebabkan ketidakseimbangan antara suplay dan demand miokard sehingga mengakibatkan hipoksia miokard. Keadaan ini menyebabkan metabolisme anaerob yang mengganggu fungsi utama jantung dalam mekanis, biokimiawi, dan listrik sehingga jantung tidak mampu lagi memompa darah secara adekuat dan selanjutnya menyebabkan kerusakan sel dan kematian (infark) miokard.

Pengkajian perawatan PASKA IMA
1.      Anamnesa
Keluhan  : Nyeri dada saat aktifitas / istirahat, rasa berdebar – debar, sesak napas , keringat dingin saat mobilisasi atau takut saat mobilisasi
2.      Pemeriksaan fisik
a.       Tanda – tanda vital ( tekanan darah menurun, atau naik , keteraturan nadi dan pernapasan)
b.      Perfusi jaringan : ada tidaknya sianotik, akral dingin, pulsasi arteri, produksi urine
c.       Bunyi jantung  ada tidaknya gallop S3 / S4 dan murmur
d.      Bunyi paru tambahan : ronchi, whezing
3.      Respon psikologis
a.       Ekpresi depresi
b.      Ekpresi penolakkan, cemas atau gelisah
Selain itu juga perlu dikaji faktor resiko berdasarkan Stratifikasi risiko paska IMAyang  merupakan  pegangan untuk menentukan prognosis dan untuk memberikan terapi yang tepat. Adapun faktor  - faktor yang merupakan penanda prognosis buruk adalah :
1.      Usia lanjut ( > 65 tahun )
2.      Wanita
3.      Pernah mengalami IMA sebelumnya
4.      IMA Anterior
5.      IMA Inferior yang disertai infark ventrikel kanan
6.      DM
7.      Perubahan ECG dibanyak lead
8.      Iskemia yang menetap atau berulang yang ditandai dengan angina pasca infark atau ST depresi saat istirahat.
9.      Hipotensi
10.  Gagal jantung
11.  Fibrilasi atrium dan aritmia ventrikel yang timbul > 48 jam pasca IMA.

KOMPLIKASI PASKA IMA
  1. Aritmia (Takiaritmia atau bradiaritmia)
  2. Disfungsi ventrikel kiri
  3. Hipotensi yang disebabkan oleh kerusakan miokard yang luas,defek mekanik, infark ventrikel kanan, aritmia, hipovolemia dan obat – obatan
  4. Nyeri dada rekuren yang disebabkan oleh reinfark, iskemia atau perikarditis
  5. Syok Kardiogenik disebabkan oleh komplikasi mekanik IMA ditandai dengan tenkanan darah sistolik , 90 mmHg disertai tanda – tanda hipoperfusi ( berkeringat, produksi urine menurun dan penurunan kesadaran)
  6. Gagal Jantung
  7. Trombus ventrkel kiri dan emboli arterial
  8. trombosis vena dalam (Deep Vena Thrombosis / DVT)

KRITERIA PASIEN DIRAWAT DI RUANG PERAWATAN JANTUNG
  1. Nyeri dada berkurang atau hilang
  2. Tidak timbul aritmia > 48 jam selama perawatan di ICCU
  3. Gambaran ST elevasi kembali kegaris isoelektrik atau menurunnya ST elevasi > 50 %
  4. Hemodinamik stabil
  5. Mampu mobilisasi tanpa keluhan
  6. Mampu BAB lancar tanpa mengejan

MASALAH PERAWATAN PASKA IMA DI RUANG PERAWATAN        
  1. Resiko tinggi ansietas / ketakutan (kematian, disfungsi seksual, efek gaya hidup)
  2. Kurang pengetahuan perawatan paska IMA
  3. Resiko tinggi perubahan perfusi
  4. Resiko tinggi penurunan curah jantung
  5. Perubahan rasa nyaman nyeri
  6. Intoleran aktifitas
  7. Resiko tinggi konstipasi
  8. Resiko inefektif regimen terapi
  9. Resiko trauma (perfusi otak menurun menyebabkan pusing / sinkope)

PENATALAKSANAAN
            Tugas dari tenaga medis dan para medis pada pasien paska IMA adalah mempersiapkan pasien dan keluarga untuk mencegah terjadi keluhan infark berulang selama perawatan di rumah sakit dan saat pulang.
Penanganan di Rumah Sakit
Tujuan :
1.      Menyesuaikan diri dengan perawatan jantung (average care)
2.      Mengurangi ansietas dan gangguan psikologis pasien dan keluarga
3.      Mobilisasi dini
4.      Memperkenalkan cara hidup sehat dan modifikasi faktor resiko

Tindakan perawatan
1.      Menjelaskan pada pasien dan keluarga tentang tiap tindakan yang perlu dilakukan
2.      Membantu pasien mengungkapkan semua masalah atau ketakutan yang berhubungan dengan IM dan pengobatannya
3.      Membantu klien melakukan teknik relaksasi dan menjaga lingkungan tetap tenang
4.      Mendampingi pasien saat melakukan aktifitas bertahap tiap shift
5.      Observasi keluhan dan tanda – tanda vital sebelum, saat , dan sesudah aktifitas
6.      Waspadai respon abnormal saat aktifitas (Nadi >120x/menit, Tensi sistolik menurun atau meningkat, sesak napas, pusing, nyeri dada dan sinkope)
7.      Mengajarkan teknik menghemat energi saat aktifitas yaitu perlu istirahat sebelum dan sesudah aktifitas, hentikan aktifitas bila letih atau sesak
8.      Membantu dan mengatur cara diet seimbang yang sehat dengan makan sayur dan buah ± 800 gram/hari, minum air 8 -10 gelas / hari, mengurangi makanan yang berlemak
9.      Memberikan privasi pada pasien saat buang air besar, intruksikan pasien gunakan bel jika ada keluhan nyeri dada, sarankan tidak mengejan.
10.  Kolaborasi dalam pemberian terapi Aspirin  (ticlopidin), penyekat beta, ACE inhibitor, penurun Lipid, Antagonis kalsium dan Nitrat, Antikoagulan serta pelunak feses
11.  Sarankan pasien eliminasi secara teratur
12.  Menjelaskan pada pasien dan keluarga patofisiologi IM dan faktor resiko
13.  Menjelaskan faktor resiko IM yang dapat diubah yaitu :
a.       Obesitas dapat meningkatkan tahanan perifer dan meningkatkan kerentanan lain
b.      Merokok dapat merusak transportasi oksigen dan menyebabkan terjadinya plague pada arteri
c.       Makanan berlemak menungjang terjadinya plague arteri
d.      Natrium berlebihan dapat meningkatkan retensi garam
e.       Gaya hidup monoton dapat menyebabkan gangguan sirkulasi kolateral
f.       Alkohol merupakan vasodilator potensial yang mengakibatkan vasokontriksi sehingga meningkatkan beban jantung
g.      Hipertensi dapat meningkatkan tahanan perifer , merusak intima arteri dan menunjang arteosklerosis
h.      Kontrasepsi oral dapat mengganggu koagulasi darah, fungsi tombosis, aktifitas fibrinolisis yang mempengaruhi aktifitas endothelium.

Penyuluhan persiapan pasien pulang
Tujuan :
1.      Mempertahankan gaya hidup sehat
2.      Meyakinkan kepatuhan pasien berobat
3.      Mendidik pasien dan keluarga tentang Penyakit jantung korone
4.      Memotivasi pasien dan keluarga melakukan aktifitas secara bertahap hingga mencapai aktifitas sebelumnya.

Pendidikan Kesehatan
Pendidikan kesehatan yang diberikan adalah  mengajak pasien dan keluarga untuk mengubah gaya hidup yang sehat agar tidak terjadi infark berulang. 
a.       Gaya hidup
Pasien yang pernah mengalami IM secara khusus diberikan pemahaman untuk memperbaiki kualitas hidupnya dan untuk mencegah terjadinya IM berulang dengan berhenti merokok, memilih makanan sehat, melakukan aktifitas fisik sesuai kemampuan. Menurunkan atau menghindari obesitas penting untuk pencegahan primer. Dengan perubahan gaya hidup seperti ini keperluan untuk penggunaan terapi seumur hidup dapat dihindari.
b.      Berhenti merokok
Merokok dapat merusak transportasi oksigen sedangkan pada pasien paska IM perlu sediaan oksigen yang baik. Dengan berhenti merokok dan menghindakan didi sebagai perokok pasif diharapkan dapat memelihara dan mmemenuhi kebutuhan oksigen dengan baik
c.       Melakukan pemilihan makanan sehat
Peran keluarga penting dalam tanggung jawab untuk membeli dan menyiapkan makanan. Anjuran diet yan diperlukan pasien adalah mengurangi konsusmsi lemak jenuh atau konsumsi kolesterol kurang dari 300 mg/hari, meningkatkan konsumsi sayur , gandum atau buah segar ± 800 gr/hari, mengurangi asupan kalori bila perlu menurunkan berat badan, mengurangi konsumsi garam dan alcohol bila ada tekanan darah tinggi.
d.      Meningkatkan aktifitas pasien dengan memulai rehabilitasi dini paska IM
Memberikan pemahan pada pasien dan keluarga pentingnya aktifitas fisik secara bertahap. Aktifitas yang dilakukan dapat memperlancar aliran darah sehingga tmencegah terjadinya aliran gangguan kolateral. Selain itu dengan aktifitas fisik energi terbakar sehingga membantu menurunkan berat badan dengan aktifitas pula dapat mempengaruhi tonus otot abdomen sehingga dapat merangsang peristaltik dan konstipasi dapat dihindari.


e.       Menurunkan berat badan
Obesitas dapat meningkatkan tahanan perifer dan beban jantung serta meningkatkan kerentaran faktor – faktor lain seperti infeksi. Untuk itu penting bagi pasien paska IM menurunkan berat badan dengan melakukan aktifitas fisik sehingga lemak yang ada dalam tubuh dapat berkurang sehingga menurunkan resiko terjadinya plague arteri.
f.       Mengontrol Tekanan Darah
Hipertensi menyebabkan peningkatan tahanan perifer yang merusak intima arteri dan menyebabkan arterosklerosis. Dengan mengontrol tekanan darah diharapkan dapat menurunkan resiko terjadi infark ulang.
g.      Mengontrol gula darah
Mengotrol gula darah memiliki efek positif pada penyakit mikrovaskuler diabetes dan komplikasi lainnya. Dalam hal ini derajat hiperglikemia berkaitan dengan peningkatan resiko aterosklerosis. Penderita diabetes mempunyai resiko lebih tinggi infark ulang dibanding yang nondiabetes.
h.      Terapi farmakologi
Pasien dan keluarga perlu diberikan pemahaman tentang pentingnya disiplin dalam pengobatan untuk menurunkan angka kesakitan dan kematian. Adapun obat – obat yang perlu dikonsumsi adalah :
F Aspirin (75 - 300 mg/ hari), atau ticlopidin bila tidak dapat mentolerir aspirin
F Penyekat Beta yang dapat menurunkan resiko terjadi infark berulang
F ACE pada penderita dengan gejala gagal jantung pada saat terjadi infark akut atau disfungsi sistolik ventrikel kiri yang persisten (fraksi ejeksi < 40%)
F Antikoagulan paska Infark Miokard untuk pasien – pasien dengan resiko tromboemboli, termasuk mereka yang mengalami infark miokard luas, anurisma atau thrombus ventrikel kiri, takiaritmia paroksismal, gagal jantung kronis dan yang memiliki riwayat tromboemboli.
F Penurun Lipid. Pada pasien dengan kadar kolesterol tinggi sebaiknya diberikan golongan statin sedang pada kadar LDL normal dan LDL rendah diberikan golongan fibrat.

BASIC ECG INTREPRETATION


BASIC ECG INTERPRETATION


The following is a basic primer in interpretation of the ECG (EKG). It is intended solely for teaching purposes, and should not be relied upon in clinical decision making. As an aside, here's a note on Brugada's algorithm, and we also have a note on antiarrhythmic drugs (and mechanisms of arrhythmia).
An Approach
ECGs can be very confusing, and there are dozens of different methods of interpretation. It's perhaps best if everyone works out their own individual approach, but here's just one approach you can build upon:
  1. Sit back and look - identify the patterns, and write down what you see!
  2. Go through the ECG systematically;
  3. Correlate ECG and clinical findings, and if necessary, go back and do a complete rethink;
  4. Try and invalidate your assessment --- look for holes!
Of the above steps, the fourth seems counter-intuitive and unnecessary. In fact, it's the most important. As in all medicine, complacence is dangerous. Avoid it!
Now, let's sketch out a systematic approach. Ours is:
  1. Check the patient details - is the ECG correctly labelled?
  2. What is the rate?
  3. Is this sinus rhythm? If not, what is going on?
  4. What is the mean frontal plane QRS axis (You may wish at this stage to glance at the P and T wave axes too)
  5. Are the P waves normal (Good places to look are II and V1)
  6. What is the PR interval?
  7. Are the QRS complexes normal? Specifically, are there:
  8. Are the ST segments normal, depressed or elevated? Quantify abnormalities.
  9. Are the T waves normal? What is the QT interval?
  10. Are there abnormal U waves?
Before we move through the systematic approach outlined above, we will outline a few basics. More advanced readers may wish to skip these basics, and move on to the systematic part of the tutorial.


How the ECG works
When cell membranes in the heart depolarise, voltages change and currents flow. Because a human can be regarded as a bag of salt water (with baad attitude), in other words, a volume conductor, changes in potential are transmitted throughout the body, and can be measured. When the heart depolarises, it's convenient (and fairly accurate) to represent the electrical activity as a dipole --- a vector between two point charges. Remember that a vector has both a size (magnitude), and a direction. By looking at how the potential varies around the volume conductor, one can get an idea of the direction of the vector. This applies to all intra-cardiac events, so we can talk about a vector (or axis) for P waves, the QRS complex, T waves, and so on.
ecg lead sees a vector moving towards it
In the above picture, the schematic ECG lead on the right `sees' the (red) vector moving towards it, shown as a positive deflection in the ECG trace; the lead at 90 degrees to this sees nothing!
Various events
We assume some knowledge of heart anatomy. Note that the normal heart has, electrically speaking, only two chambers, an atrial and a ventricular `chamber'. Propagation of electrical activity spreads freely between atria and ventricles, but communication between these two chambers is limited to the AV node. Everyone knows that the P wave corresponds to atrial depolarisation, the QRS complex to ventricular depolarisation, and the T wave to repolarisation of the ventricle.
The ECG (EKG)
In order to be able to record myocardial activity, the electrocardiograph needs to be able to detect tiny changes in potential on the body surface. We are talking about signals that are often around 1mV, and may be smaller. In addition, we need some reference point to which we relate the potential changes.
The 12-lead ECG
Over the years, we have evolved several systems that go to make up the 12-lead ECG. These are:
  • Bipolar leads: the reference point is on one limb, the `sensing' electrode (if you wish) is on another limb. The leads are termed I, II, and III.
standard leads I,II,III
  • Unipolar leads: The reference point is several leads joined together, and the sensing lead is on one limb. These leads are conventionally augmented, in that the reference lead on the limb being sensed is disconnected from the other two.
AVR, AVL, AVF
  • The V leads, which extend across the precordium, V1 in the fourth right interspace, V2 4th left, V4 at the apex (5th interspace, midclavicular line), V3 halfway in between V2 and V4, and V5 & V6 in the 5th interspace at the anterior and mid axillary lines respectively.
V1 to V6
We can visualise the directions of the various leads --- I points left, and aVF points directly down (in a 'Southward' direction). The other leads are arranged around the points of the compass --- aVL about 30o more north of I, II down towards the left foot, about 60o south of I, and III off to the right of aVF. aVR `looks' at the heart from up and right, so effectively it's seeing the chambers of the heart, and most deflections in that lead are negative.
(a net positive vector in AVR is unusual, and suggests that lead placement was incorrect. If the leads were correctly sited, then think dextrocardia, or some other strange congenital abnormality).
It's usual to group the leads according to which part of the left ventricle (LV) they look at. AVL and I, as well as V5 and V6 are lateral, while II, III and AVF are inferior. V1 through V4 tend to look at the anterior aspect of the LV (some refer to V1 and V2 `septal', but a better name is perhaps the `right orientated leads'). Changes in depolarisation in the posterior aspect of the heart are not directly seen in any of the conventional leads, although "mirror image" changes will tend to be picked up in V1 and V2.
groups of ECG leads
Paper
ECG paper is traditionally divided into 1mm squares. Vertically, ten blocks usually correspond to 1 mV, and on the horizontal axis, the paper speed is usually 25mm/s, so one block is 0.04s (or 40ms). Note that we also have "big blocks" which are 5mm on their side.
ECG voltage and timing
Always check the calibration voltage on the right of the ECG, and paper speed. The following image shows the normal 1mV calibration spike:
ECG calibration spike on right
Damping
Note that if the calibration signal is not "squared off" then the ECG tracing is either over or under-damped, and should not be trusted.


Heart rate
Knowing the paper speed, it's easy to work out heart rate. It's also very convenient to have a quick way of eyeballing the rate, and one method is as follows:
  1. Remember the sequence: 300, 150, 100, 75, 60, 50
  2. Identify an R wave that falls on the marker of a `big block'
  3. Count the number of big blocks to the next R wave.
If the number of big blocks is 1, the rate is 300, if it's two, then the rate is 150, and so on. Rates in between these numbers are easy to `interpolate'.
But always remember that in the heart, because we have two electrically `isolated' chambers, the atria and ventricles, that we are really looking at two rates --- the atrial and ventricular rates! It just so happens that in the normal heart, the two are linked in a convenient 1:1 ratio, via normal conduction down the AV node. In disease states, this may not be the case.
Conventionally, a normal heart rate has been regarded as being between 60 and 100, but it's probably more appropriate to re-adjust these limits to 50 -- 90/min. A sinus tachycardia then becomes any heart rate under 90, and bradycardia, less than 50. Note that you have to look at the clinical context -- a rate of 85 in a highly trained athlete may represent a substantial tachycardia, especially if their resting rate is 32/minute! One should also beware of agressively trying to manage low rates in the presence of good perfusion and excellent organ function.
Sinus bradycardia
Apart from fit, but otherwise normal individuals, there's a long list of situations where sinus bradycardia occurs, including:
  • hypothermia;
  • increased vagal tone (due to vagal stimulation or e.g. drugs);
  • hypothyroidism;
  • beta blockade;
  • marked intracranial hypertension;
  • obstructive jaundice, and even in uraemia;
  • structural SA node disease, or ischaemia.
Sinus tachycardia
Always consider pain as a possible cause of tachycardia. There's a long list, however:
  • Any cause of adrenergic stimulation (including pain);
  • thyrotoxicosis;
  • hypovolaemia;
  • vagolytic drugs (e.g. atropine)
  • anaemia, pregnancy;
  • vasodilator drugs, including many hypotensive agents;
  • FEVER
  • myocarditis
If the rate is almost exactly 150, always make sure that you are not mistaking atrial flutter with a 2:1 block for sinus tachycardia. A common error.


Rhythm
Sinus arrhythmia and heart rate variability
sinus arrhythmia
There is normally a slight degree of chaotic variation in heart rate, called sinus arrhythmia. Sinus arrhythmia is generally a good thing, and loss of this chaotic variation is of ominous prognostic significance. Post myocardial infarction, a metronome-like regularity of the heartbeat is associated with an increased likelihood of sudden death, and just before the onset of ventricular tachycardia (or fibrillation), variability is lost! Absence of any sinus arrhythmia suggests an autonomic neuropathy.
Atrial extrasystoles
These arise from ectopic atrial foci. Commonly, the ectopic beat always arises at about the same time after the sinus beat!
atrial extrasystole
The ectopic beat usually discharges the SA node, so subsequent beats of SA origin are not in synchrony with the previous sinus rhythm.
If the extrasystole occurs early on, it may find the His-Purkinje system not quite ready to receive an impulse, and a degree of block may be seen. This is termed `aberration'.
Distinguish between an atrial extrasystole, and an atrial escape beat, where the SA node falters, and a subsidiary pacemaker takes over:
atrial escape beat
(Parenthetically, we didn't draw the P waves very well in the above strip. Don't let this put you off from indentifying the underlying rhythm).
Supraventricular tachyarrhythmias (SVT)
Irregular SVT
By far the commonest cause of irregular SVT is atrial fibrillation, where the atrial rate is in the region of 450 to 600/min, and the atria really do not contract rhythmically at all. The atrium "fibrillates", writhing like a bag of worms. The conventional view of the pathogenesis of AF is that there are multiple re-entrant `wavelets' moving through the atrial muscle, but recent evidence suggests that much AF actually arises from ectopic activity in the muscular cuff surrounding the pulmonary veins where they enter the left atrium. AF is thought to beget further AF through "electrical remodelling" --- electrophysiological changes that are induced in atrial myocytes due to fast rates and the consequent calcium loading.
atrial fibrillation
Note that in the above tracing of AF, the ventricular response rate seems rather slow, so we suspect that AV block has been increased using pharmacological manipulation. In uncontrolled AF, rates of about 130 or more are common.
Other causes of irregular SVT are:
  • Frequent atrial extrasystoles;
  • Multifocal atrial tachycardia, where there are three or more distinct atrial foci, combined with tachycardia. There is often severe underlying disease (e.g. chronic obstructive airways disease), and in the ICU setting, MAT has a poor prognosis.
  • "Atrial flutter with variable block".
multifocal atrial tachycadia
Although it looks like atrial fibrillation, the above image actually shows multifocal atrial tachycardia. Note how there are at least three different P wave configurations!
Regular SVT
Atrial flutter is common. The atrial rate is commonly 300/min, and there is usually a 2:1 block, resulting in a ventricular response rate of 150/min. Other ratios are possible, and sometimes the ratio varies. This rhythm is often unstable, and the heart may flip in and out of sinus rhythm, or there may be runs of atrial fibrillation.
atrial flutter with 2:1 block
In the above ECG the clue is the rate. A rate of 150 should always engender the suspicion of atrial flutter with 2:1 block.
Probably the commonest cause of regular SVT is AV nodal re-entrant tachycardia. Here, there are generally two ways that electrical depolarisation can enter the AV node from the atrium, a slow and fast `pathway'. A re-entrant circuit can be set up, with impulses moving in a circular fashion, and causing depolarisation of the ventricles at fast rates (up to 200/min or even more).
Other causes of regular SVT include:
  1. ectopic atrial tachycardia, due to repetitive discharges from an ectopic atrial focus;
  2. AV re-entrant tachycardia, via an accessory pathway, discussed next.
Accessory pathways
Abnormal, congenital extra pathways between the atria and ventricles are common, and can perforate the electrically insulating fibrous ring that normally separates the atrial `chamber' and the ventricular one. The most well-characterised is the Wolff-Parkinson-White syndrome. Reasonable (WHO) criteria for the WPW pattern on ECG are:
  1. PR interval under 0.12s
  2. A delta wave
  3. QRS duration of 0.12s (or more)
  4. A normal P-wave axis
Because depolarisation moves `antegrade' from atria to ventricles, part of the ventricle depolarises prematurely, and this is responsible for the slurred, initial delta wave. It should be clear that the PR interval will therefore be short, and the QRS duration should be prolonged. Note however that not everyone with an accessory pathway will conduct all of the time down that pathway. Accessory pathways are common, estimated to occur in one to three individuals in every thousand. Symptomatic pathways are far less common.
Wolff-Parkinson-White pattern
The WPW syndrome is a combination of the WPW pattern, and tachycardias. The tachycardias may be due to impulse conduction down via the AV node and back up the accessory pathway (commonest, called orthodromic tachycardia), the other way around (down accessory pathway, up AV node, termed antidromic tachycardia), or even related to atrial fibrillation. This last cause is ominous, as if the accessory pathway is able to conduct impulses at fast rates, the ventricle may be driven at rates in excess of 200/min, causing collapse or even death.
Distinguishing causes of SVT
A few pointers are in order. The important thing to look for is the P wave:
  1. If the P is inscribed before the QRS, it's probably an ectopic atrial tachycardia;
  2. If the P is after the QRS, consider orthodromic AV re-entrant tachycardia;
  3. If the P is not seen (and probably lost within the QRS) it's likely to be AV nodal re-entrant tachycardia.
A few other hints:
  • The baseline ECG is invaluable (may show WPW, for example);
  • It's useful if you can capture onset or termination of the arrhythmia.
Ventricular extrasystoles
Because these arise within an ectopic focus within the ventricular muscle, the QRS complex is wide, bizarre, and unrelated to a preceding P wave. There is usually a constant relationship (timing) between the preceding sinus beat and a subsequent ventricular beat, because the preceding beat influences the ectopic focus.
ventricular extrasystole
The ventricular beat is not usually conducted back into the atria. What happens to the atrial beat that occurred, or was about to occur when the VE happened? Usually, this is blocked, but the subsequent atrial beat will occur on time, and be conducted normally.
Rarely, the ventricular beat may be conducted retrogradely and capture the atrium (resulting in a P wave after the QRS, with an abnormal morphology as conduction through the atrium is retrograde). The atrial pacemaker is now reset! In the following rather complex tracing, we have a ventricular rhythm (a bit faster than one might expect, perhaps an accelerated idioventricular rhythm) with retrograde P waves, and something else --- some of the P waves are followed by a normal looking `echo' beat as the impulse is conducted down back into the normal pathways).
retrograde P waves
Because the intrinsic rate of an ectopic focus often tends to be slow-ish, extrasystoles will tend to arise more commonly with slower rates. In addition, if the rate is varying, extrasystoles will tend to `squeeze in' during long RR intervals. Some have called this the "rule of bigeminy".
Couplet
Two VE's are termed a couplet.
Fusion beat
Occasionally, a VE occurs just after a sinus beat has started to propagate into the His-Purkinje system. This results in a `fusion beat', which combines the morphology of a normal sinus beat and that of the extrasystole.
Parasystole
Rarely, the ectopic focus is protected from other influences, and does its own merry thing. This is termed `parasystole', and is detected by noting the unvarying coupling between extrasystoles, and the lack of coupling between the extrasystole and sinus beats! In the following trace, note the fusion beats as the normal rhythm and parasystolic rhythm transiently coincide...
Parasystole
We've put in the above unusual ECG more as a mnemonic than for any other reason. We want you to remember that even with extrasystoles, there is flow of information from the normal rhythm to the ectopic focus. The ectopic focus is therefore modulated by the normal rhythm, and usually occurs at about the same interval from the normal events. Parasystole is unusual.
Ventricular tachycardia
Three or more ventricular extrasystoles are a bad sign, and are termed ventricular tachycardia (VT). There is usually severe underlying myocardial disease. Sustained VT (more than about 30 beats) often degenerates into ventricular fibrillation, resulting in death.
The above strip shows several `characteristic' features of VT. Apart from the regular fast rate and wide complexes, we have a few more clues ... clearly, the atrial rate is different from the ventricular rate, and there is dissociation between atria and ventricles --- the P waves occur at any time in relation to the QRS complexes. Even more characteristic of VT is the presence of a fusion beat at the start of the trace --- a QRS complex which is something in between the VT morphology and normal morphology. There is also a capture beat later on, where the P wave has managed to sneak through and transiently take over, resulting in a normally-shaped QRS complex and T wave.
VT vs SVT+aberration
Distinguishing between VT, and SVT with aberration is tricky. When in doubt, one should apply synchronised DC countershock, and agonize later. This is especially the case if the patient is haemodynamically unstable. If the patient is haemostable, the rate is slowish (under about 150), then one may have more time. A variety of algorithms have been proposed - Brugada's approach may have merit --- you can explore a web-based version of his algorithm here.
Ventricular fibrillation
This is a chaotic ventricular rhythm that rapidly results in death. It is often precipitated by a critically timed extrasystole, that occurs during the relative refractory period of the myocardial fibres. Conventional wisdom has it that this results in chaotic, unco-ordinated wavelets of depolarisation moving through the ventricular mass.
ventricular fibrillation
VF is a dire emergency. If unsynchronised DC countershock is applied within 30s of the onset of VF, there is an approximately 97% chance that sinus rhythm will be restored, and the person will survive. Survival decreases exponentially thereafter, with every minute of delay.
Ventricular flutter
Ventricular 'flutter' is a bizarre sine-wave like rhythm, and usually degerates into ventricular fibrillation. You won't see it often (or for long).
ventricular flutter




Axis
The peculiar system we use in electrocardiography is non-Cartesian, and rather arbitrary! We measure the direction of vectors in degrees, and zero is indeed facing `East', but +90o is South, instead of North as it would be in a Cartesian system. You can work out that ± 180o is 'West', and that minus 90o is 'North'.
We can talk about the `axis' of any ECG depolarisation, but most people when they are talking 'axis' are referring to the mean frontal plane QRS axis. There is a number of ways of determining this, but the following method has the merit of simplicity:
  1. Estimate the overall deflection (positive or negative, and how much) of the QRS in standard lead I;
  2. Do the same for AVF;
  3. Plot the vector on a system of axes, and estimate the angle, thus:
Determining the axis
Note in the above picture that the (abnormal) axis illustrated is negative ("towards the left") because AVF is negative.
People tend to faff quite a lot about QRS axis deviations, but they are a fairly blunt-edged tool. Marked right axis deviation (e.g. +150o) may signify significant `right-sided' heart disease. Left axis deviation is not uncommon in inferior myocardial infarction, and if this is absent, the most likely `diagnosis' is left anterior hemiblock. (There are several other cause of left or right axis deviation, for example depolarisation via accessory pathways).
Where the axis is up and to the left (eg. -135o), this is termed a "north west axis". It is commonly seen in congenital heart disease, dextrocardia, and sometimes in severe chronic obstructive airway disease.
The T wave axis is much neglected, and may be of value. If the T wave axis is more than about 45 to 60o different from the QRS axis, this is abnormal. Schamroth gives a super mnemonic --- "the T-wave axis moves away from the `region of mischief'".
Even the P-wave axis is of use. The normal axis is about +40 to +60o, moving right with chronic obstructive disease. The axis may move left with congenital heart disease, even up to -30o (especially Ebstein's anomaly). One can also spot an ectopic atrial focus low down in the atrium (`coronary sinus rhythm') due to the `northern' shift in axis.
The P wave
Normal atrial activation is over in about 0.10s, starting in the right atrium. A good place to look at P waves is in II, where the P shouldn't be more than 2.5mm tall, and 0.11 seconds in duration.
A tall P wave (3 blocks or more) signifies right atrial enlargement, a widened bifid one, left atrial enlargement:
Std lead II: enlarged left atrium
Std lead II: P pulmonale of RA enlargement
In V1, another good place to look, depolarisation of the right atrium results in an initial positive deflection, followed by a vector away from V1 into the left atrium, causing a negative deflection. The normal P wave in V1 is thus biphasic. It's easy to work out the corresponding abnormalities with left or right atrial enlargement:
There are a few other tips:
  • A qR in V1 suggests right atrial enlargement, often due to tricuspid regurgitation! (Observed by Sodi-Pallares). [qv]
  • If the overall QRS amplitude in V1 is under a third of the overall QRS amplitude in V2, there is probably RA enlargement! (Tranchesi).
  • A P wave originating in the left atrium often has a `dome and dart' configuration.


The PR interval (and PR segment)
The PR interval extends from the start of the P wave to the very start of the QRS complex (that is, to the start of the very first r or q wave). A normal value is 3 to 5 `little blocks' (0.12 to 0.20 seconds). It's convenient at this point to discuss blocks...
SA node block
This is a diagnosis of deduction, as no electrical activity is seen. An impulse that was expected to arise in the SA node is delayed in its exit from the node, or blocked completely. A second degree SA block can be `diagnosed' if the heart rate suddenly doubles in response to, say, administration of atropine. If the SA node is blocked, a subsidiary pacemaker will (we hope) take over, in the atrium, AV node, or ventricle!
AV nodal blocks
There are three "degrees" of AV nodal block:
  1. First degree block:
simply slowed conduction. This is manifest by a prolonged PR interval;
prolonged PR interval: first degree heart block

  1. Second degree block:
Conduction intermittently fails completely. This may be in a constant ratio (more ominous, Type II second degree block), or progressive (The Wenckebach phenomenon, characterised by progressively increasing PR interval culminating in a dropped beat --- this is otherwise known as Mobitz Type II second degree heart block).
Wenckebach phenomenon
Mobitz type II block

  1. Third degree block:
There is complete dissociation of atria and ventricles.
complete heart block
Clearly a bad thing, requiring temporary or even permanent pacing.




The QRS complex
The nomenclature is mildly arcane --- small deflections are reflected using lower case, and larger deflections UPPER CASE. An initial downwards deflection is a Q (or q), any negative deflection after this is an S. An upward deflection is an R. Note that we refer to a second deflection in the same direction by adding a prime, so we have R', R'', S' and so on. We might thus refer to an rSR' morphology, or whatever.
Normally, the septum depolarises before other parts of the left ventricle. This is seen as a small initial vector, which in the `septal leads' (V1 and V2) is a positive deflection, and in lateral leads (e.g. V6) is seen as a small q. This observation is of relevance, as in conditions such as left bundle branch block, where the septum cannot depolarise normally, the lateral (septal) q is conspicuously missing.
Something of some importance is the time it takes the ventricle to depolarise, often termed the ventricular activation time. We can estimate this from the surface ECG by looking at the time from the onset of the QRS to the sudden downstroke of the QRS. (The fancy name for this sudden downstroke is the `intrinsicoid deflection'). In right orientated leads, a normal VAT is 0.02s, and on the left (e.g. V6) the duration should not exceed 0.04s.
Q waves - myocardial infarction
Q wave in inferior lead in old IMI
   
Many people who have had a prior MI will have an ECG that appears normal. There may however be typical features of previous MI, and the most conspicuous of these is Q waves. A simplistic explanation of these prominent Q waves is that an appropriately placed lead "sees through" the dead tissue, and visualises the normal depolarisation of the viable myocardial wall directly opposite the infarcted area. Because, in the normal myocardium, depolarisation moves from the chamber outwards, this normal depolarisation is seen as a Q wave!
Another feature of previous MI is loss of R wave amplitude. It's easy to imagine that if muscle is lost, amplitude must be diminished. (Having a pre-infarction ECG for comparison is invaluable).
One can get some idea of the site of infarction from the lead in which abnormalities are seen - inferior, lateral, or anterior.
Hypertrophy and chamber enlargement
Because of the thin-walled nature of the atria, from an ECG point of view, one cannot talk about "atrial hypertrophy" but only about enlargement. Conversely, thickening of the ventricle may result in increased voltages seen on the surface ECG, and we can then discuss "ventricular hypertrophy".







Left ventricular systolic overload/hypertrophy (LVH)
The absence of LVH on ECG means nothing, as the features are insensitive. If however they are present, LVH is very likely. Because the criteria were formulated on white males, they are very insensitive in e.g. black women.
Systolic overload results in increased QRS deflections, with the sum of the S in V1 and the R in V5 or V6 over 35mm indicating hypertrophy. (In the above picture, also note the predominantly negative deflection of the P wave in V1, suggesting left atrial enlargement). A host of other criteria have been proposed. Useful are:
  • R in I over 15mm
  • R in AVL over 11mm
  • Sum of all QRS voltages under 175mm (!)
T wave axis changes can be predicted knowing Schamroth's rule .
LV diastolic overload
Features of LVH may be present (as above). Enormous R waves may be seen in left-sided leads, especially with aortic or mitral regurgitation. In contrast to systolic overload, where septal q waves in the lateral leads are often diminished or absent, in diastolic overload, prominent lateral Qs are noted. Unlike systolic overload (where the T waves are often inverted), T waves are usually upright, very symmetrical, and somewhat pointed.
Inverted U waves in V4-6 suggest either systolic or diastolic LV overload.
RV hypertrophy
A number of ECG abnormalities have been associated with right ventricular hypertrophy. These include:
  • right axis deviation;
  • A tall R wave (bigger than the S) in V1;
  • A `little something' in V1 (an initial slur of the QRS, a small r, or a tiny q).
  • Increased VAT in V1
  • left-sided RS or rS complexes, partial or complete RBBB, or RS complexes in the mid-precordial leads.
RV hypertrophy - tall R in V1
Whenever you see a tall R in V1, consider the following differential:
  • posterior myocardial infarction
  • RV hypertrophy
  • Right bundle branch block
  • Wolff-Parkinson-White syndrome (with an appropriately placed accessory pathway)
  • Other rare causes such as dextrocardia, Duchenne muscular dystrophy, and so on
  • and, of course, incorrect lead placement!
Bundle branch blocks
A broadened QRS complex suggests a bundle branch block, although there are other causes:
RBBB
Diagnostic criteria for right bundle branch block are somewhat empiric, but useful. Here they are:
  1. Tall R' in V1;
  2. QRS duration 0.12s or greater (some would say, >= 0.14);
In addition, there is usually a prominent S in the lateral leads (I, V5, V6).
RBBB seen in V1
RBBB is sometimes seen in normal people, or may reflect congenital heart disease (e.g. ASD), ischaemic heart disease, cardiomyopathy, or even acute right heart strain.
LBBB
Diagnose this as follows:
  1. No RBBB can be present;
  2. QRS duration is 0.12s or more;
  3. There must be evidence of abnormal septal depolarization. The tiny q waves normally seen in the left-sided leads are absent. (And likewise for the normal tiny r in V1).
In addition, the VAT is prolonged, and tall, notched R waves are seen in the lateral leads (RR' waves). There is usually a notched QS complex in V1 and V2.
LBBB
Fascicular blocks
Left anterior hemiblock (LAHB) is interruption of the thin anterosuperior division of the left bundle. Suspect it if there is left axis deviation (past -45o) without another cause (such as inferior myocardial infarction, or some types of congenital heart disease or accessory pathways).
Other features of LAHB include an initial QRS vector which is down and to the right, a long VAT, and several other minor changes.
LAHB may indicate underlying heart disease, but is much more worrying when associated with other abnormalities (such as PR interval prolongation or RBBB).
The diagnosis of left posterior hemiblock is mentioned only to be avoided!


The ST segment
The junction between QRS and ST
Hypothermia
Besides sinus bradycardia, the most common finding is a prominent J wave.
very prominent J waves
In addition, there may be delayed VAT , QRS prolongation, and nonspecific T wave abnormalities, with QT prolongation. Eventually, blocks, ventricular extrasystoles, and finally ventricular fibrillation occurs, below 30oC.
Ischaemic heart disease - ST changes
One should always remember that more than a quarter of people presenting with an acute myocardial infarction will have no ECG evidence of ischaemia or infarction! The ECG on its own is a blunt-edged tool in the detection of coronary artery disease. Exercise testing to elicit ischaemia is also not very sensitive in detecting this common disease.
Acute myocardial infarction --- the `hyperacute phase'
There are four main features of early myocardial infarction (as per Schamroth): [qv etc]
  1. increased VAT
  2. increased R wave amplitude (!)
  3. ST elevation which is sloped upwards!
  4. Tall, widened T waves (The ST segment often merges with these)
Acute myocardial infarction
Note that Q waves are not seen early on.
Established acute myocardial infarction
Q wave, with ST elevation and inverted T, in acute MI
   
We now lay great emphasis on ST segment elevation in diagnosing acute MI (In the past, Q waves were remarked on, but as noted above, these are often absent, early on). The features of `full blown' MI may be:
  1. prominent Q waves;
  2. elevated ST segments;
  3. Inverted `arrowhead' T waves.
Remember our previous warning, that a significant proportion of people having an acute MI will have a normal ECG, so do not rely on any of these features to exclude MI.
Posterior MI
The trick in diagnosing this is to realise that posterior wall changes will be mirrored in the leads opposite to the lesion --- V1 and V2. S we'll see a tall R (corresponding to a Q), ST depression, and upright arrowhead T waves:
Right ventricular infarction
This occurs in about 1/3 of patients with inferior MI, but is often missed. It would be distinctly unusual in the absence of inferior MI. Sensitivity can be improved by looking at V4R --- V4, but put the lead on the right side of the chest! Look for ST elevation which is higher than that in V1 -- V3. Another suggestive feature is lack of ST depression in V1 with evidence of MI in the inferior leads (look for ST depression in V2 under 50% of the ST elevation in AVF).
Non-ST elevation MI
There are no reliable correlates of "subendocardial" or non-ST elevation MI, and the diagnosis is based on the combination of clinical and laboratory criteria (troponin elevation being important). There may be no ECG changes, or even ST segment depression and/or T wave abnormalities.
Angina and stress testing
The most important component of an effort ECG that indicates the presence of coronary artery disease is where exercise reproduces the patient's chest discomfort or pain. Other findings may be:
  • ST segment depression (It is customary to apply the Sheffield criteria, that is, 1mm (0.1mV) ST depression 0.08s after the J point;
  • failure of suppression of ventricular ectopy, or (especially) development of ectopy in the recovery period;
  • Failure of the blood pressure to rise with exercise (an ominous finding);
  • ST segment elevation
  • T-wave changes (which may be rather nonspecific)
  • Development of inverted U waves, which, although subtle, is said to be specific for the presence of ischaemia!
Did you notice the ST segment depression in our section on voltage and timing, above?
ECG voltage and timing
Prinzmetal's angina
The simple (and possibly even correct) explanation of why you see ST segment elevation with this variant form of angina is that the predominant area of ischaemia is epicardial. This disorder is thought to be related to vascular spasm, and angiography shows coronaries without a significant burden of atheroma. Many other morphological abnormalities have been described with this disorder.
Other morphological abnormalities
'Early repolarisation'
This is common --- ST segment elevation is conspicuous, often with a prominent J wave. It has been remarked upon in athletes, particularly. It's important to relate the ECG to the clinical context, as always, as otherwise one might inappropriately suspect serious underlying heart disease.
[pics]


T waves
T wave abnormalities are common and often rather nonspecific. T-wave changes that suggest ischaemia are a very sudden junction between the ST segment and the T wave, and very symmetrical T waves. A variety of changes may be seen with cardiomyopathies, intracranial haemorrhage and so on. Symmetrical deep T-wave changes most prominent in V3 and V4 suggest ischaemia in the territory of the left anterior descending artery (LAD T0-waves). We should all know the features of hypo- and hyper-kalaemia.
Hyperkalaemia
Initial features are tall "tented" T waves. Later, despite the continuation of sinus rhythm, the P waves disappear, and finally, the QRS complexes broaden and become bizarre, the ST segment almost vanishes, and the patient dies from ventricular arrhythmia or cardiac standstill.
For features of hypokalaemia, see below .
Measures - QT
This is the time from onset of QRS to end of T wave. Because QT varies with rate, it is common to apply a correction, usually using Bazett's formula:
        QTc =       QTmeasured
              ---------------------
                SQRT (RR interval)
SQRT refers to the square root. A normal value is about 0.39s ±0.04s (slightly larger values are acceptable in women). Be particularly concerned if the value is over 0.5, as may be seen in poisoning with tricyclic antidepressants, congenital QT syndromes, hypocalcaemia, and toxicity from a variety of other drugs (quinidine, procainamide, amiodarone, sotalol, erythromycin, etc). Other cause have been reported, including hypothermia, head injury, acute myocardial infarction (!), and hypertrophic cardiomyopathy.








U waves
Hypokalaemia
The T waves flatten, U waves become prominent (this may be falsely interpreted as QT prolongation), and there may even be first or second degree AV block.
Several syndromes
Myocarditis
Common findings are tachycardia, heart blocks (first degree, LAHB), and increased VAT . A variety of ST changes may be seen, including those of myopericarditis. Atrial and ventricular extrasystoles are common.
Myopericarditis
Pericarditis is usually associated with a degree of contiguous myocarditis. The major manifestation is widespread ST segment elevation.
There is also usually sinus tachycardia, and T wave abnormalities are common.
Pericardial effusion
The most common finding here is simply diminished amplitude of the ECG deflections. There may also be T wave inversion, and sometimes one sees electrical alternans .
Pulmonary thromboembolism
Apart from sinus tachycardia, ECG abnormalities are not common. The `classical' S1Q3T3 syndrome occurs in under 10%. Other features may be those of right atrial enlargement, RV hypertrophy or ischaemia, RBBB and atrial tachyarrhythmias.
Digoxin effect
ST segment changes are pretty characteristic, with their "reverse tick" conformation. These changes are not indicative of toxicity, but merely the presence of digitalis. With toxicity, practically any arrhythmia can be seen, although certain arrhythmias are highly suggestive, for example, the presence of both increased irritability and AV nodal block (such as paroxysmal atrial tachycardia with a 2:1 AV nodal block).
Electrical alternans
Here, there is no rhythm disturbance, but the QRS amplitude alternates --- tall one beat, shorter the next (and so on...). At fast rates, this is said to be of little significance, but at slower rates usually signifies severe heart disease, or pericardial effusion.
Bibliography and sources
A good general reference is Leo Schamroth's An Introduction to Electrocardiography, published by Blackwell Scientific. (7th Ed., 1990, ISBN 0-632-02411-9). It has the merits of both clarity, accuracy and depth). Leo was one of the truly great men of electrocardiography, and a brilliant physician, to boot.
This primer is still a work in progress, and we anticipate adding a lot of information, and images, over the next few years. Most of the above images were painstakingly redrawn (mainly from a variety of mediocre- or worse-quality Web images), vectorised using the demonstration version of the excellent R2V program, screen captured into PaintShop Pro, and then further processed. They are far from perfect!

Date of First Publication: 2003/7/4
Date of Last Update: 2003/7/4
Web page author: jo@anaesthetist.com