Baylor Health Care System: Recurrent wide-QRS tachycardias

	Past Issue: Volume 13, Number 1 • January 2000
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BUMC Proceedings 2000;13:80-81

Recurrent wide-QRS tachycardias

D. LUKE GLANCY, MD, AND C. W. TAN, MD

From Section of Cardiology, Department of Medicine, Louisiana State University Medical Center, New Orleans.

Corresponding author: D. Luke Glancy, MD, Section of Cardiology, Department of Medicine, Louisiana State University Medical Center, 1542 Tulane Avenue, New Orleans, Louisiana, 70112-2822.

I asked Dr. Luke Glancy recently if he would be willing to prepare an electrocardiographic lesson periodically for the BUMC Proceedings, and he agreed to do so. Dr. Glancy, a good friend, is one of the best electrocardiographers in the USA. He was born in Atlanta. He received his college degree from Emory University and his medical degree in 1961 from John Hopkins University. He trained in internal medicine at The John Hopkins Hospital for 3 years and had an additional year as chief resident in medicine at Grady Memorial Hospital in Atlanta under Dr. J. Willis Hurst. He then came to the National Institutes of Health (NIH) and within 2 years was chief of the cardiac catheterization laboratory of the cardiology branch of the National Heart Institute. In 1972, he left NIH to become a professor of medicine and the chief of the Section of Cardiology of the Department of Medicine at Louisiana State University School of Medicine in New Orleans. He has remained in New Orleans since that time. He stepped down as medical director of cardiology at the University Hospital of Louisiana State University in 1999 but continues to be in charge of the fellowship program there. I am delighted that he will provide these periodic electrocardiographic lessons.

--WILLIAM C. ROBERTS, EDITOR IN CHIEF

he electrocardiogram in Figure 1 shows a regular wide-QRS tachycardia (rate, 149 beats per minute). The QRS complex superficially resembles right bundle branch block, but 3 features are different. First, the QRS axis is markedly to the left in the frontal plane, and no pattern of left anterior fascicular block is present. Second, the QRS complex in V1 does not have the typical rSR_ configuration of right bundle branch block but is instead a monophasic R wave. Finally, the S wave in V6 is deep, and the R/S ratio in that lead is <1. In contrast to this rS pattern, right bundle branch block typically has a qRs or qRS pattern in V6. These features strongly suggest that the arrhythmia is ventricular tachycardia and not supraventricular tachycardia with a right bundle branch block aberration. This diagnosis is confirmed by independent sinus P waves occurring regularly at a rate of 92 beats per minute and fusion beats. The 12th, 15th, 18th, and 21st QRS complexes in Figure 1 are fusions between ventricular tachycardia complexes and conducted complexes. The 12th QRS complex more closely resembles a ventricular complex, whereas the 21st QRS complex more closely resembles a conducted complex.

The patient, who was 46 years old when this electrocardiogram was recorded, had cardiomyopathy with 4-chamber dilatation and left ventricular ejection fraction of 18% and decreased right ventricular function. His electrocardiogram in sinus rhythm was grossly abnormal, showing a slightly long P-R interval, right atrial enlargement, right axis deviation, and right ventricular enlargement (Figure 2). Because of the patient's recurrent episodes of ventricular tachycardia, an automatic implantable cardioverter-defibrillator (AICD) was placed within months of these electrocardiograms, and he was given amiodarone.

Although amiodarone did not prevent additional episodes of ventricular tachycardia, the drug slowed the rate of the arrhythmia, often below the rate threshold of the AICD. The electrocardiogram in Figure 3 was recorded 3 years after the one in Figure 1. The QRS morphology is similar, but instead of independently occurring sinus P waves, the P waves now arise from impulses conducted retrogradely from the ventricles; are negative in 2, 3, and aVF; and are peaked positively in V1. The pattern is that of 3:2 Wenckebach-type ventricular-atrial block.

As illustrated in Figures 1 and 3, the relationship between P waves and QRS complexes is often the most helpful in correctly diagnosing wide-QRS tachycardias. Unfortunately, when the ventricular rate is considerably more rapid than those shown in these 2 examples, P waves may be impossible to find. Under those circumstances, one must rely on the differences in QRS morphology that distinguish ventricular tachycardia from aberrantly conducted supraventricular tachycardia.

General references

Josephson ME, Callans DJ. Sustained ventricular tachycardia. In Kaster JA, ed. Arrhythmias. Philadelphia: WB Saunders Co, 1994:336–362.

Marriott HJL. Emergency Electrocardiography. Naples, Fla: Trinity Press, 1997: 57–78.

Wellens HJJ, Conover MB. The ECG in Emergency Decision Making. Philadelphia: WB Saunders Co, 1992:37–72.