Latency During Left Ventricular Pacing From the Lateral Cardiac Veins: A Cause of Ineffectual Biventricular Pacing

Abstract

We report three patients with cardiomyopathy and pronounced stimulus to QRS latency during left ventricular (LV) pacing from an epicardial cardiac vein. Delayed LV activation during simultaneous biventricular pacing produced an electrocardiographic pattern dominated by right ventricular stimulation. Hemodynamic parameters improved immediately after advancing LV stimulation (in one patient) or pacing the LV only (in two patients) coupled with dramatic improvement of heart failure symptoms.

Site-Specific Differences in Latency Intervals during Biventricular Pacing: Impact on Paced QRS Morphology and Echo-Optimized V-V Interval

“…The RV latency interval was much shorter than the traditional normal value of <40 ms that was never based on firm data 8 . Our findings suggest that the LV latency interval in CRT patients usually measures <40 ms and uncommonly ≥40 ms 1 . Accordingly, precise measurement of paced QRS‐related ECG intervals requires omitting the latency interval.…”

“…Cardiac resynchronization therapy (CRT) is ineffective in approximately 30% of patients. The lack of hemodynamic improvement may be due to regional differences in electrical excitability and impulse propagation such as electrical latency, 1 slow impulse propagation in proximity of the lead (due to scar), 2–4 and globally delayed intra‐ and interventricular (V‐V) conduction 5 . All these conditions may affect left ventricular (LV) performance during biventricular stimulation by changing balance between right ventricular (RV) and LV activation.…”

Patient Specific Simulation of Body Surface ECG using the Finite Element Method

“…Although a simultaneous bi‐ventricular pacing protocol (no inter‐ventricular delay) was programmed for this patient, we needed to advance the right ventricular (RV) stimulation by 70 ms to achieve reasonable agreement in the ECGs. In our opinion, this delay can be accounted for by the electrical latency during left ventricular (LV) stimulation from the coronary veins and in fact, a comparison of the ECGs for RV and LV pacing alone supports this idea (Fig. C inset).…”

RV‐Only Pacing Can Produce a Q Wave in Lead 1 and an R Wave in V1: Implications for Biventricular Pacing

“…The surface ECG allows one to compare the activation patterns during native conduction, RV pacing, and LV pacing, and thereby rapidly demonstrate which elements are contributing to ventricular activation during bi‐v pacing. This information is not available from a device interrogation, and so without the addition of surface ECG analysis, scenarios of QRS pseudofusion or a dominant RV‐paced QRS morphology would be missed, potentially resulting in CRT nonresponse or even a worsening of LV function and clinical outcomes . Because the specificity of using only leads 1 and V1 to verify LV pacing is less than 50%, this study reinforces the need to use additional ECG leads for improved accuracy of bi‐v pacing analysis …”