ECG OF THE MONTH
Vignettes in Electrocardiography: Exploring initial QRS forces –
A diagnostic clue to wide QRS tachycardia.
Sachin Nayyar, Mohan Nair
Department of Cardiology, St Stephens Hospital , Tis Hazari, Delhi.
| This is the electrocardiogram (ECG) of a 70-year old male presented with history of exertional dyspnea. On evaluation, he had moderate left ventricular dysfunction. What is your diagnosis? |
The ECG shows monomorphic wide QRS tachycardia with left bundle branch block (LBBB) and right axis morphology (+ 120 degree). There is cycle length variation especially in the first half of the recording hough subsequently it is apparently regular. P waves like deflection is present preceding each QRS (saw tooth like positive wave in inferior leads, negative in aVL, equiphasic in V1). Even though QRS is very wide, initial
component of QRS is sharp and follows the aberrancy pattern. A right axis rather than a normal / inferior axis is against aberrancy pattern, as QRS axis should remain normal with pure rate related aberrancy. However, in the presence of preexisting bundle branch block with structural heart disease related axis shift, the QRS axis during supra ventricular tachycardia with aberrancy will be the same as that of the
preexisting bundle branch block. The notching in the QRS suggests myocardial disease. First possibility should be atrial flutter with LBBB aberrancy.
The possibility of ventricular tachycardia (VT) should
also be discussed especially with structural heart
disease. Cycle length variation can occur in VT due to
various reasons such as at initiation of tachycardia,
capture beats, varying refractoriness of segment with
conduction delay in the reentrant tachycardia circuit,
varying exit blocks from a automatic / triggered
tachycardia, varying exits of the tachycardia, or a
polymorphic VT 1, 2.
This case was confirmed to be isthmus dependent atrial
flutter on electrophysiologic (EP) study, which was
successfully treated. The patient had LBBB with right
axis in sinus rhythm.
REFERENCES
1. Wellens HJ, Bär FW, Lie KI. The value of the electrocardiogram in the differential
diagnosis of a tachycardia with a widened QRS complex. Am J Cardiol. 1978;
64:27-33.
2. Fromer M, Cardinal R, Pagé P,et al. Variation in cycle length of induced
ventricular tachycardia episodes in humans: incidence and electrophysiologic
mechanisms. In: Shenasa M, Borggrefe M, Breithardt G, eds. Cardiac Mapping.
Mount Kisco,NY:Futura;1993:507-514.
Correspondence: Sachin Nayyar, Department of Cardiology, St Stephens Hospital , Tis Hazari, Delhi-110054.
E-mail: sachinnay@yahoo.co.in
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