ECG quiz: Possible acute coronary syndrome and fast palpitations

As part of a series on Pulse, Dr Yassir Javaid, a GPwSI in cardiology and echocardiography, asks what these ECGs could signify. See bottom of the page for answers

Question 1

66 year old woman presents with chest tightness and nausea. She has a history of diabetes and is a smoker. The ECG is consistent with which ONE of the following diagnoses?

A Acute pericarditis
B Acute ST elevation inferior (and possibly posterior) MI
C Acute anterior ST depression MI with reciprocal inferior ST elevation
D Brugada pattern
E Benign early repolarization

Question 2

A middle-aged woman present with recent onset fast palpitations. This arrhythmia is most consistent with which endocrine disorder?

A Hyperthyroidism
B Hypothyroidism
C Hyperparathyroidism
D Addison’s disease
E Cushing’s disease

Question 3

85-year-old male is worried about a slow heart rate but is without symptoms and is not on cardiac medications. What is the rhythm here?

A Atrial tachycardia with AV block
B Sinus bradycardia (marked) consistent with sick sinus syndrome
C Sinus rhythm with 2:1 AV block
D Sinus rhythm with complete (third degree) AV block
E Sinus rhythm with 3:2 AV Wenckebach

Answers

Question 1 Acute ST elevation inferior (and possibly posterior) MI

Explanation

Any history suggestive of possible acute coronary syndrome should warrant a 999 admission to hospital irrespective of ECG findings. However it would be reasonable to do an ECG at the surgery whilst waiting for an ambulance and have a defibrillator on standby.

The ECG reveals significant ST changes in the inferior leads – ie ST elevation in leads II, III, aVF

TIP Be aware of the regions of the heart within an ECG ie anterior = V1-V4, lateral = I, aVL, V5 & V6, inferior = II, III and aVF. If you find similar abnormalities within the leads of a region that is highly suspicious of ischaemic pathology.

Question 2 Hyperthyroidism

Explanation

The ECG clearly shows a tachyacardia, the absence of p waves and an irregular QRS rhythm confirming fast atrial fibrillation. The other clue is the variation in amplitude of the QRS complexes. The single wave seen between the QRS complexes must be a T wave as every QRS complex must be accompanied by a T wave – you cant have ventricular depolarization without ventricular repolarization.

Hyperthyroidism has a strong association with AF and can also contribute to the tachycardia. Correction of the hyperthyroidism can lead to resolution of the atrial fibrillation.

Question 3 Sinus rhythm with 2:1 AV block

Explanation

A slow heart rate can be physiological or pathological.

Physiological causes are always asymptomatic (eg young fit athletes) but pathological causes can be asymptomatic or symptomatic. Exclude betablockers or rate limiting calcium channel blockers (eg diltiazem) as a cause and consider whether there may be underlying hypothyroidism.

An ECG should be undertaken if a suspected pathological cause.

This ECG reveals regular P waves but only every other p wave is followed by a QRS complex indicating a high degree heart block – in this case 2^nd degree type 2 with 2:1 AV conduction, This requires referral for assessment for a pacemaker