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).
Figure 1. ECG = electrocardiogram.
Algorithm to identify biventricular pacing in patients with an implanted cardiac resynchronization device.Grahic Jump Location
Figure 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.
Electrocardiographic tracings from lead V1 and I in 1 patient with an implanted cardiac resynchronization device.top2nd from top2nd from bottombottomGrahic Jump Location
Figure 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.
Coronary sinus electrode placement in the lateral cardiac vein (A and B) and the posterior cardiac vein (C and D) of 2 different patients with an implanted cardiac resynchronization device.A.B.C.D.Grahic Jump Location
Figure 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.
Main QRS axis during biventricular pacing, relative to electrocardiograph leads I and V1.Grahic Jump Location
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