Wide QRS tachycardia in the conscious adult: ventricular tachycardia is the most frequent cause

Ventricular tachycardia (VT), rapid heart rate produced by pathology of the ventricle, is a serious problem that is often associated with improper filling of the heart chambers and severely impaired hemodynamic (blood flow patterns) functioning. One irregularity that is seen clinically is wide QRS tachycardia, which may be associated with a stable hemodynamic situation. Wide QRS refers to a relatively increased length of electrical activity (greater than 0.14 seconds) in the phase identified on an electrocardiogram as the QRS complex, which reflects the muscular contraction of the ventricle. A generally held misconception, which in turn has led to misdiagnosis, is that VT must lead to circulatory collapse. To examine the association of hemodynamic stability in patients with wide QRS tachycardia, 20 consecutive patients were examined. Eighty-five percent of patients were found to have VT. As a result of this study, until proven otherwise, patients with wide QRS tachycardia should be regarded as being in VT and appropriate therapy for this condition should be instituted. Failure by physicians to understand that a wide QRS tachycardia is associated with ventricular difficulties may lead to improper treatment that can severely and adversely affect a patient's condition. Electrophysiologic testing has been shown to be of particular value in establishing this diagnosis.
ABSTRACT: Hemodynamic stability during wide QRS tachycardia is commonly, albeit erroneously, taken as evidence for a supraventricular mechanism. To determine the magnitude for potential misdiagnosis in applying this notion clinically, we analyzed 20 consecutive cases of regular wide QRS tachycardia in conscious adult patients (mean age, 64 years). The most common heart disease was atherosclerotic (75%), with an associated history of remote myocardial infarction in 73% of the cases. Tachycardia was sustained for a mean of 4.8 hours prior to medical evaluation, with a mean rate of 186 beats per minute and mean systolic blood pressure of 111 mm Hg. A diagnosis of ventricular tachycardia (VT) was established in 17 cases (85%). In the patients with VT, atrioventricular dissociation was recognized on the 12-lead electrocardiogram in 38%, with Wellens' morphological features favoring the diagnosis in 73%. Following conversion to sinus rhythm, electrophysiological testing in 17 patients reproduced the clinical arrhythmia in 94% (with a replication rate of 100% in 15 patients with VT), with at least one additional unsuspected VT morphology induced in 53% of patients with VT. Thus, VT should be considered the most likely cause of regular wide QRS tachycardia in the conscious adult patient, especially with a history of remote myocardial infarction. Recognition of this simple principle and careful examination of the 12-lead electrocardiogram may help to prevent the misapplication of pharmacotherapy in the vast majority of these patients.