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ECG for Medical Student OSCE

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1. Recording the ECG

   1. ‘I have been asked to perform and ECG tracing of your heart. This is a device that records the rhythm and electrical activity of the heart, and involves attaching small patches on the arms, legs and chest, which are connected to the machine. It is a simple procedure that will not cause shocks or pain.’

   2. Consent + check ID. Pt onto couch + expose

   3. Attach limb leads to dorsal aspects of forearms and lateral lower limbs, above ankles. Leads are coloured; attach leads clockwise, starting with right arm, following the colours of traffic lights: red – right arm; yellow – left arm; green – left leg; black – right leg.

   4. Remaining leads = V1 – V6:

      1. V1: 4^th intercostal space, right sternal edge

      2. V2: 4^th intercostal space, left sternal edge

      3. V3

      4. V4: 5^th intercostal space, mid-clavicular line

      5. V5

      6. V6: 5^th intercostal space, mid-axillary line

   5. Turn on machine, press ‘filter’ then ‘start’ to print.

   6. Write on ECG patient’s name, DOB, hospital number and the time and date of the ECG

2. Evaluation of ECG

   1. Introduction

      1. Patient details

      2. Time and date of ECG recording

   2. Rate

      1. Calibration and print speed (25mm sec^-1)

      2. 300 / large squares between R waves

   3. Rhythm

      1. Sinus

      2. AF: no P wave, irregular QRS

      3. Atrial tachycardia: narrow QRS denotes problems is not in ventricles. >100 bpm. Abnormal P wave

      4. Atrial flutter: saw tooth pattern baseline, regular QRS

      5. AV nodal rhythm: narrow QRS complexes; P waves hidden

      6. Ventricular rhythm: broad complex QRS, >150 bpm

   4. Cardiac axis

      1. Lead I: 0?

      2. Lead II: +60?

      3. Lead VF: +90?

      4. Lead III: +120?

   5. Waves

      1. P wave: normally <0.12s, amplitude <2.5mm. absent in AF, SA block etc. Bifid P waves: left atrial hypertrophy. Peaked P waves: right atrial hypertrophy.

      2. QRS complex: 0.04-0.12s. Wide in bundle branch block (WiLLiaM MaRRoW: in Left BBB, W pattern seen in V1 and V2, and M in V3 and V6; in Right BBB, M seen in V1 and V2, and W in V3 and V6). Large QRS complex can be due to ectopic rhythms from ventricles, or ventricular hypertrophy. Deep Q waves mean acute MI in past few hours (>1 sq wide, >2mm deep). Tall R waves: left ventricular hypertrophy (in V6, >25 mm). Deep S waves: right ventricular hypertrophy (in V6).

      3. ST segment: elevation >1mm = acute MI or, if saddle-shaped, acute pericarditis. Depressed >0.5mm = angina, digoxin therapy, posterior infarct (V1 and V2). Depending on lead indicates location of infarction

      4. T wave: (can be normally inverted in V1-V3 in black or young people). Inverted: ischaemia, MI, ventricular hypertrophy, PE, BBB. Peaked in Hyperkalaemia. Flattened in hypokalaemia.

      5. J wave: hypothermia

   6. Intervals

      1. PR interval normally 0.12-0.2s. Short if there is faster conduction via an accessory pathway. Long PR interval: delayed AV conduction – 1^st degree heart block. Complete dissociation between P and QRS = 3^rd degree heart block.

      2. Secondary heart block: Mobitz type 1 (wenckebach: lengthening PR intervals until dropped beat). Mobitz type 2 (normal fixed PR intervals, with occasional non-conducted P waves. Can come in 2:1 and 3:1 formats, with e.g. only every 3 P waves being conducted)

      3. QT interval: 0.38-0.42s. Prolonged implies acute myocardial ischaemia, myocarditis, electrolyte abnormality (low K/Ca/Mg)

   7. Particular rhythms

      1. VF: pulseless arrhythmia. Immediate DC cardioversion

      2. AF: treatment is by treating the cause – thryotoxicosis, infection; chemical treatment; DC shock

      3. Atrial flutter: the atrial rate is commonly 300 min^-1, and there is usually a 2:1 block, resulting in a ventricular response rate of 120 min^-1. Characteristic ‘sawtooth’ flutter waves on the baseline

      4. Sinus bradycardia: normal in sleep. Otherwise, may reflect ischaemia to the sinus node, hypothermia, increased vagal tone, hypothyroidism, beta blockade, intracranial hypertension and jaundice

      5. Third degree heart block: no association between atrial and ventricular activity. Ventricular escape rhythm at 40 bpm.

      6. Ventricular tachycardia: defined by presence of 3 or more consecutive ventricular beats. Usually >120 bpm, broad QRS. (Trace looks like very deep saw teeth at ~120bpm, with no other features)

About the Author

by: Admin
Total views: 0
Word Count: 1085
Date: Fri, 22 Jan 2010 Time: 4:12 PM
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