Key result
Fusing right ventricular septal-only pacing with intrinsic conduction via the left anterior fascicle reduced QRS duration from 153 to 106 ms and improved ejection fraction from 14% to 32%.
Why the study?
Response to conventional CRT is lower in non-LBBB patients, and alternative approaches tailoring CRT to non-LBBB dyssynchrony patterns have yet to be developed.
Does fusing RV septal pacing with intrinsic conduction improve CRT response indices in a patient with heart failure and RBBB with LPFB?
Case Report (n=1)
No
Does fusing RV septal pacing with intrinsic conduction improve CRT response indices in a patient with heart failure and RBBB with LPFB?
Absolute Event Rate: 106% vs 153%
Fusing RV septal pacing with intrinsic conduction using a negative AV hysteresis algorithm successfully achieved cardiac resynchronization in a patient with RBBB and LPFB without requiring an LV lead.
Despite advances, cardiac resynchronisation therapy (CRT) remains fundamentally orientated to the dyssynchrony of left bundle branch block (LBBB), in which septo-lateral electrical and mechanical delays predominate. For non-LBBB patients response rates to conventional CRT are lower and mortality and rehospitalisation rates are not reduced. Despite this, alternative approaches which tailor CRT to the differing dyssynchrony patterns of non-LBBB have yet to be developed. In the specific non-LBBB subgroup of right bundle branch block (RBBB) with left posterior fascicular block (LPFB), ventricular conduction via the left anterior fascicle results in a unique early lateral, and late septal depolarisation, or lateral to septal left ventricular (LV) delay, an electrical sequence which is followed mechanically. This latero-septal delay is somewhat the reverse of LBBB and was overcome by fusing right ventricular (RV) septal pacing with intrinsic conduction via the left anterior fascicle, achieving successful resynchronisation without implantation of a left ventricular lead. A stable fusion pattern was achieved via the 'Negative AV Hysteresis with Search' algorithm (Abbott, St Paul, Minnesota). Improvement in all standard CRT response indices was achieved at 3 months: QRS duration was reduced from 153 to 106 ms, ejection fraction increased from 14 to 32%, and LV end-systolic and end-diastolic diameters reduced by 19% and 12.5% respectively. NYHA class improved from III-IV to class II. Cardiac resynchronisation for RBBB with LPFB can be successfully achieved with a standard pacemaker or defibrillator without left ventricular lead implantation by fusing RV septal-only pacing with intrinsic conduction.
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Dennis et al. (2022) conducted a case report in Heart failure with right bundle branch block (RBBB) and left posterior fascicular block (LPFB) (n=1). Right ventricular septal-only pacing fused with intrinsic conduction (Negative AV Hysteresis with Search algorithm) vs. Baseline (pre-intervention) was evaluated on QRS duration (ms). Fusing right ventricular septal-only pacing with intrinsic conduction via the left anterior fascicle reduced QRS duration from 153 to 106 ms and improved ejection fraction from 14% to 32%.
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