Key result
RV pacing with wide QRS increases RVOT VTI by ~3 cm versus baseline narrow QRS.
Why the study?
Right ventricular pacing is traditionally considered deleterious, but paradoxical movement of the interventricular septum toward the RV free wall may functionally assist RV performance. Whether RV pacing enhances RV systolic output compared to indigenous rhythm in patients with mild to moderate pulmonary hypertension and preserved LV function was unclear.
Does right ventricular pacing with a wide QRS improve right ventricular outflow tract velocity time integral (stroke volume) compared to indigenous narrow QRS rhythm in patients with permanent pacemakers, mild to moderate pulmonary hypertension, and preserved LV systolic function?
Does right ventricular pacing with a wide QRS improve right ventricular outflow tract velocity time integral (stroke volume) compared to indigenous narrow QRS rhythm in patients with permanent pacemakers, mild to moderate pulmonary hypertension, and preserved LV systolic function?
In patients with mild-to-moderate pulmonary hypertension and preserved LV function, wide QRS right ventricular pacing acutely increases RV stroke volume (RVOT VTI) compared to native narrow QRS rhythm via paradoxical septal motion.
May suggest acute RV stroke volume benefit from wide QRS pacing in mild PH; challenges dyssynchrony consensus yet leaves open for prospective trials.
Background Right heart failure remains a clinical challenge with high mortality and limited therapeutic options. Traditionally, right ventricular (RV) pacing is considered deleterious due to induced dyssynchrony. However, the interventricular septum (IVS) possesses an oblique fiber orientation optimized for the left ventricle (LV). In conditions such as idiopathic pulmonary hypertension or left bundle branch block, the IVS exhibits a "paradoxical" movement toward the RV free wall. This shift may functionally assist the RV by "wringing" blood out of the chamber, suggesting that induced dyssynchrony could potentially benefit RV performance. Purpose This study aimed to investigate whether RV pacing, by altering the mechanical activation of the IVS, enhances RV systolic output compared to indigenous rhythm in patients with augmented RV systolic pressure (mild to moderate pulmanoary hypertension) and preserved LV function. Methods We studied 25 consecutive patients (mean age 72±8 years; 60% male) with permanent pacemakers implanted for sick sinus disease and RV systolic pressure of 40-50mmHg and preserved LV systolic function (LVEF >50%). Hemodynamic performance was evaluated using transthoracic echocardiography. Two distinct electrical states were compared in each patient: 1) Indigenous rhythm with a narrow QRS (achieved by extending AV delays or lowering the pacing rate) and 2) Right ventricular pacing with a wide QRS (achieved by shortening AV delays or increasing the pacing rate). The primary endpoint was the RV outflow tract velocity time integral (RVOT VTI), representing stroke volume. Results The study population was verified for demonstrating mild to moderate pulmanoary hypertension and preserved left ventricular systolic function . Statistical analysis revealed a significant trend toward greater RV output during wide QRS pacing compared to native rhythm. The mean RVOT VTI in indigenous narrow QRS rhythm was 21±0.8 cm. In contrast, during wide QRS RV pacing, the RVOT VTI significantly increased to 24±1.2 cm (p < 0.05). These findings suggest that the mechanical shift of the IVS toward the RV free wall during pacing-induced dyssynchrony acts as a compensatory mechanism that improves RV ejection fraction in the setting of mildly elevated RV systolic pressure. Conclusion(s) Right ventricular pacing might not be universally deleterious. In specific clinical contexts, the paradoxical motion of the IVS induced by apical RV pacing can significantly enhance RV stroke volume. This mechanism provides a potential therapeutic pathway for managing isolated right heart failure. Future pacing strategies, perhaps utilizing multiple wireless electrodes to precisely control septal "wringing," may allow clinicians to titrate septal contribution to either the left or right ventricle, optimizing performance based on the patient's specific heart failure phenotype.
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Skiadas et al. (2026) studied Mild to moderate pulmonary hypertension with preserved left ventricular systolic function and permanent pacemakers for sick sinus disease (n=25). Right ventricular pacing with a wide QRS vs. Indigenous rhythm with a narrow QRS was evaluated on Right ventricular outflow tract velocity time integral (RVOT VTI) (p=<0.05). Right ventricular pacing with a wide QRS significantly increased RVOT VTI compared to indigenous narrow QRS rhythm (24±1.2 cm vs 21±0.8 cm; p<0.05).
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