Dizzy

A 71-year-old man is brought to the emergency department after feeling persistently light-headed and unwell at home for the past hour.

Stage 1 of 2

He is alert and conversant, with no chest pain or breathlessness at rest. An ECG is recorded on arrival.

Tracing 1 of 2 for the quiz “Dizzy”. — 12-lead, 25 mm/s, 10 mm/mV Open this tracing in the studio

What is the most likely diagnosis?

AVentricular tachycardia Correct answer Your answer
BSVT with aberrant conduction Your answer
CAntidromic AV re-entrant tachycardia Your answer
DSinus tachycardia with bundle branch block Your answer

This is a regular broad-complex tachycardia at 143 beats per minute with a QRS duration of about 170 ms. In a 71-year-old man, a regular broad-complex tachycardia is ventricular tachycardia until proven otherwise. The rhythm strip contains capture and fusion beats, proving atrioventricular dissociation, which in a broad-complex tachycardia establishes VT. SVT with aberrancy can produce a broad QRS but cannot produce AV dissociation.

Which feature on this tracing confirms the diagnosis?

ACapture and fusion beats in the rhythm strip Correct answer Your answer
BQRS duration greater than 140 ms Your answer
CDeeply negative complexes in V1 to V3 Your answer
DVentricular rate above 120 beats per minute Your answer

Capture beats are narrow complexes that appear when a sinus impulse conducts to the ventricles between tachycardia beats. A fusion beat has an intermediate morphology produced by simultaneous activation from both the sinus impulse and the ventricular focus. Together they prove that the atria and ventricles are operating independently, which in a broad-complex tachycardia effectively proves ventricular tachycardia. A wide QRS alone does not exclude aberrant conduction.

How should this haemodynamically stable VT be treated?

ASynchronised DC cardioversion under sedation Correct answer Your answer
BIntravenous amiodarone Your answer
CIntravenous adenosine Your answer
DIntravenous verapamil Your answer

The 2022 ESC ventricular arrhythmia guideline recommends synchronised electrical cardioversion as first-line treatment for haemodynamically tolerated sustained monomorphic VT with known or suspected structural heart disease, provided the sedation risk is acceptable (Class I). Intravenous procainamide should be considered (Class IIa) and intravenous amiodarone may be considered (Class IIb). The reflex to reach for amiodarone because the patient is stable is common but is a weaker recommendation than cardioversion. The Resuscitation Council UK adult tachycardia algorithm still names amiodarone for stable broad-complex tachycardia, so practice varies between guidelines.

Stage 2 of 2

Synchronised DC cardioversion is performed under procedural sedation in the resuscitation room and sinus rhythm is restored. A repeat ECG is recorded.

Tracing 2 of 2 for the quiz “Dizzy”. — 12-lead, 25 mm/s, 10 mm/mV Open this tracing in the studio

Observations

Heart rate: 74

What does this post-cardioversion ECG show?

AOld anterior myocardial infarction Correct answer Your answer
BAcute anterior ST-elevation myocardial infarction Your answer
CLeft bundle branch block Your answer
DNormal ECG Your answer

There are QS complexes across V1 to V4 with no R-wave progression through the anterior chest leads, indicating a previous anterior myocardial infarction. The T waves are upright in V3 to V6 and there is no acute ST elevation, distinguishing this from an acute event. The QRS is narrow at 74 ms, excluding a bundle branch block.

Why is this finding important in this patient?

AInfarct scar is the likely substrate for the VT Correct answer Your answer
BIt indicates an acute coronary syndrome needing urgent angiography Your answer
CIt suggests a cardiomyopathy unrelated to the arrhythmia Your answer
DIt is incidental and has no bearing on the tachycardia Your answer

Monomorphic ventricular tachycardia in the setting of a healed myocardial infarction is typically scar-mediated re-entry. The infarct scar provides the slow conduction zone that sustains the tachycardia circuit. This patient requires cardiology assessment, echocardiography to assess left ventricular function, and consideration of an implantable cardioverter-defibrillator for secondary prevention of sustained VT.

Diagnosis

Monomorphic ventricular tachycardia with old anterior myocardial infarction

The presence of capture and fusion beats in the rhythm strip proves atrioventricular dissociation and confirms ventricular tachycardia. Haemodynamic stability does not distinguish VT from supraventricular tachycardia with aberrant conduction, and treating a stable broad-complex tachycardia as SVT is a well-recognised and dangerous error.

For haemodynamically tolerated monomorphic VT with suspected structural heart disease, the 2022 ESC guideline recommends synchronised electrical cardioversion as first-line treatment. After cardioversion, the resting ECG reveals QS complexes across the anterior chest leads, indicating a previous anterior myocardial infarction. The infarct scar is the substrate for re-entrant VT. This patient needs cardiology assessment, echocardiography and consideration of an implantable cardioverter-defibrillator for secondary prevention.

References

Brugada P, Brugada J, Mont L, Smeets J, Andries EW. A new approach to the differential diagnosis of a regular tachycardia with a wide QRS complex. Circulation. 1991;83(5):1649-1659.
Wellens HJJ. Ventricular tachycardia: diagnosis of broad QRS complex tachycardia. Heart. 2001;86(5):579-585.
Zeppenfeld K, Tfelt-Hansen J, de Riva M, et al. 2022 ESC Guidelines for the management of patients with ventricular arrhythmias and the prevention of sudden cardiac death. Eur Heart J. 2022;43(40):3997-4126.

The case

On arrival

Observations

Diagnosis

References

Discussion