A Case of VT

This healthy 23 year old woman presented with palpitations and a systolic blood pressure of 95 mm Hg.

ECG_0009_A taken at 1900

ECG_0009_A taken at 1900

+ Describe the changes in this ECG, and the most likely cause of this rhythm.

There is a wide QRS complex tachycardia with a ventricular rate of about 188 beats per minute. The rhythm is regular. The QRS morphology shows a right bundle branch block and left axis deviation. The QRS duration is 120-140 msec. There are no visible P waves.

There is slight variability in the amplitude of the QRS complexes, well seen in the frontal leads (Lead II and Lead aVF) and in the rhythm strip. The alteration in amplitude does not follow the regular electrical alternans pattern that occurs in some cases of supraventricular tachycardia. These changes in QRS amplitude are a sign of atrioventricular dissociation (Alzand et al. Europace. 2011), and thus favour the diagnosis of ventricular tachycardia.

Some of the QRS complexes are narrower than the preceding or following complexes e.g. second complex in Lead II, seventh complex in Lead aVF, fourth complex in Lead V2. This suggests capture beats.

The QRS complexes in Lead V1 have a rsR1 shape, which favours aberrant conduction rather than ventricular tachycardia. The QRS complexes in Lead V2 have a Rsr1 shape, with a left “rabbit” ear that is taller than the right “rabbit” ear. The changes in Lead V2 favour the presence of ventricular tachycardia.

The QRS complexes in Lead V6 have a RS ratio that is less than one i.e. the S wave amplitude is greater than the R wave amplitude. This favours the presence of ventricular tachycardia.

The underlying rhythm is ventricular tachycardia; the combination of right bundle branch block andleft axis deviation indicates a left ventricular outflow tract origin of the ventricular tachycardia.

ECG_0009_B taken at 1930 after treatment with verapamil

ECG_0009_B taken at 1930 after treatment with verapamil

+ Describe the changes in this ECG.

Sinus rhythm is present with a prolonged PR interval of about 0.24 seconds. There is 1 mm ST elevation in Leads V2 to V6, associated with elevation of the J point in these leads. The changes in the precordial leads are characteristic of the so-called early repolarization syndrome.

There is slight slurring of the initial upstroke of the R wave in Leads V2 to V6 that hints at the presence of an accessory pathway. The presence of features of ventricular tachycardia in the wide QRS tachycardia seen in ECG0009A should take diagnostic preference over the possible presence of a delta wave.