VALUE OF MCL(1), MCL(6), AND SELECTED LEADS IN THE DIAGNOSIS OF WIDE QRS COMPLEX TACHYCARDIA (MCL, CORONARY CARE).
Contributors: University of California, San Francisco.
Published: 1990
Number of pages: 162
Subjects: Health Sciences, Nursing.
Description: Use of the conventional precordial leads V$\sb1$ and V$\sb6$ has been suggested for distinguishing supraventricular tachycardia with aberrant ventricular conduction from ventricular tachycardia. For two decades, MCL$\sb1$ MCL$\sb1$ and MCL$\sb6$ have been widely used as V$\sb1$ and V$\sb6$ substitutes for bedside monitoring, but their use has never been validated. To determine the value of these bedside leads compared to their conventional lead counterparts, 121 wide QRS complex tachycardias were recorded from 92 patients during cardiac electrophysiology study with simultaneous MCL$\sb1$, V$\sb1$, MCL$\sb6$, V$\sb6$, and His bundle electrogram recordings. In addition, a full 12-lead electrocardiogram was recorded to evaluate selected leads hypothesized to be a value in making the diagnosis.

As determined from the His bundle recording, 31 of the tachycardias were supraventricular with aberration; 86 were ventricular. A majority of both normal and wide QRS complexes had identical patterns in MCL$\sb6$ and V$\sb6$. Although QRS morphology clearly differed between MCL$\sb1$ and V$\sb1$ in about one third of wide QRS complex tachycardias, no difference in diagnostic accuracy resulted.

A dissociated P wave during tachycardia, which was diagnostic of VT, was more likely to be observed in V$\sb1$ or MCL$\sb1$. A width of greater than 160 ms discriminated best between aberrant supraventricular and ventricular tachycardia. Axis deviation was a more useful criteria to diagnose ventricular tachycardias with a right, rather than a left bundle branch block contour.

A new criterion, measurement of QRS onset to the predominant peak or nadir of the complex, proved to be valuable in diagnosing wide QRS complex tachycardia in MCL$\sb6$ and V$\sb6$. An interval of 50 ms or less was suggestive of abberant supraventricular tachycardia; an interval of 70 ms or more was virtually diagnostic of ventricular tachycardia.

Recommendations for clinical practice included the following. For single-channel monitors, leads MCL$\sb1$ and MCL$\sb6$ had the highest diagnostic accuracy; for dual-channel monitors, combined MCL$\sb1$/MCL$\sb6$ were superior to other two-lead sets. With the current inability to display two precordial leads simultaneously, there was no advantage in monitoring more than two leads.
Notes: Source: Dissertation Abstracts International, Volume: 51-11, Section: B, page: 5244.

Thesis (PH.D.)--UNIVERSITY OF CALIFORNIA, SAN FRANCISCO, 1990.

School code: 0034.