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DIAGNOSIS: Ventricular tachycardia, atrial flutter/fibrillation, A-V dissociation, ventricular capture beats. EXPLANATION: The patient was a 75 year-old-male who presented with dyspnea. His vital signs were stable with a BP 150/80. A wide complex [QRS duration 140 msec] tachycardia at a rate of 140 bpm may be noted throughout most of this tracing with the presence of a marked left axis deviation. Although there is no concordance in the precordial leads, the morphology in V1 and V6 is certainly suggestive of a ventricular origin of this arrhythmia. [There is a monophasic R wave in V1, not an rsR', and the R/S ratio in V6 is less than one]. One should not be fooled by the stability of the patient, which is more related to heart rate and underlying myocardial function than to ventricular verses supraventricular origin of such tachycardias. A careful look at V1 reveals P waves at an almost regular rate of 350 which are indicative of flutter/fib. These bear no relationship to the surrounding ventricular complexes; they are dissociated. More importantly, in the last 3 beats of this tracing, they capture the ventricles leading to a short run of atrial fib; this virtually proves the ventricular origin of the prior tachycardia. In fact, this patient had multiple episodes of such capture noted on his rhythm strip. A-V dissociation, fusion beats, and capture beats, when they occur, are definitive evidence of ventricular tachycardia. Unfortunately, A-V dissociation is rarely seen as clearly as this on an ECG tracing. P waves are usually difficult to find amidst all the QRST activity. Furthermore, A-V dissociation occurs only 50% of the time; in the remainder, the ventricles capture the atria via retrograde conduction. Finally, this patient proved to have an acute myocardial infarction documented by cardiac enzyme elevations. There is little evidence for this on the tracing however; perhaps a bit of ST depression in V3. Thanks to Greg Garra, DO for this ECG. Editor: Sol Nevins MD FACEP. Faculty, Emergency Medicine Residency, Morristown Memorial Hospital, Morristown, N.J. |
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