We devised an algorithm that reliably detects loss of left ventricular capture in patients with a cardiac resynchronization device and left bundle-branch block. The sensitivity and specificity of the algorithm are high (94% [CI, 88.2% to 97.7%] and 93% [CI, 86.3% to 95.8], respectively).
Grahic Jump LocationFigure 2. In the upper tracing, the device is programmed in right ventricular pacing mode. In the first tracing ( ), the cardiac resynchronization device is programmed to the right ventricular pacing mode. The remaining 3 tracings show the shift of the V1 and I axes with continuous electrocardiographic resynchronization between the right and left ventricle at 0 ms ( ), −40 ms ( ), and −80 ms ( ) of left ventricular offset.
Grahic Jump Location
Grahic Jump LocationFigure 3. Biventricular pacing, which the algorithm identified. Right ventricular pacing only, which the algorithm identified. Biventricular pacing, which the algorithm failed to identify. Right ventricular pacing only, which the algorithm identified.
Grahic Jump Location
Grahic Jump LocationFigure 4. The algorithm assesses electrograms obtained through lead V1, the only chest lead overlying the right ventricle, and lead I. Whenever the left ventricle is activated, the main electrical vector is directed towards lead V1. Since there is always fusion with the concurrent right ventricular apical stimulation, a complete right bundle-branch block pattern in V1 is rare. However, an R–S spike ratio of 1 or greater can reliably detect left ventricular capture. Lead I needs to be assessed only if fusion with right ventricular stimulation is causing a mainly negative deflection in lead V1. In this example, left ventricular stimulation will cause a negative deflection because the main vector is now directed from the left to the right side, pointing away from lead I.
Grahic Jump Location
Terms of Use
The In the Clinic® slide sets are owned and copyrighted by the American College
of Physicians (ACP). All text, graphics, trademarks, and other intellectual property
incorporated into the slide sets remain the sole and exclusive property of the ACP.
The slide sets may be used only by the person who downloads or purchases them and
only for the purpose of presenting them during not-for-profit educational activities.
Users may incorporate the entire slide set or selected individual slides into their
own teaching presentations but may not alter the content of the slides in any way
or remove the ACP copyright notice. Users may make print copies for use as hand-outs
for the audience the user is personally addressing but may not otherwise reproduce
or distribute the slides by any means or media, including but not limited to sending
them as e-mail attachments, posting them on Internet or Intranet sites, publishing
them in meeting proceedings, or making them available for sale or distribution in
any unauthorized form, without the express written permission of the ACP. Unauthorized
use of the In the Clinic slide sets will constitute copyright infringement.