Energy loss by right ventricular pacing: Patients with versus without hypertrophic cardiomyopathy

Abstract

Background: Right ventricular (RV) pacing causes left ventricular (LV) dyssynchrony sometimes resulting in pacing-induced cardiomyopathy. However, RV pacing for hypertrophic obstructive cardiomyopathy is one of the treatment options. LV flow energy loss (EL) using vector flow mapping (VFM) is a novel hemodynamic index for assessing cardiac function. Our study aimed to elucidate the impact of RV pacing on EL in normal LV function and hypertrophic cardiomyopathy (HCM) patients.

Methods: A total of 36 patients with dual-chamber pacemakers for sick sinus syndrome or implantable cardioverter defibrillators for fatal ventricular tachyarrhythmias were enrolled. All patients were divided into two groups: 16 patients with HCM (HCM group) and others (non-HCM group). The absolute changes in EL under AAI (without RV pacing) and DDD (with RV pacing) modes were assessed using VFM on color Doppler echocardiography.

Results: In the non-HCM group, the mean systolic EL significantly increased from the AAI to DDD modes (14.0 ± 7.7 to 17.0 ± 8.6 mW/m, P = .003), whereas the mean diastolic EL did not change (19.0 ± 12.3 to 17.0 ± 14.8 mW/m, P = .231). In the HCM group, the mean systolic EL significantly decreased from the AAI to DDD modes (26.7 ± 14.2 to 21.6 ± 11.9 mW/m, P < .001), whereas the mean diastolic EL did not change (28.7 ± 16.4 to 23.9 ± 19.7 mW/m, P = .130).

Conclusions: RV pacing increased the mean systolic EL in patients without HCM. Conversely, RV pacing decreased the mean systolic EL in patients with HCM.

Keywords: echocardiography; energy loss; hypertrophic cardiomyopathy; right ventricular pacing; vector flow mapping.

FIGURE 1

Study protocol. PM, pacemaker; ICD, implantable cardioverter defibrillator; HCM, hypertrophic cardiomyopathy; LVEF, left ventricular ejection fraction; AV block, atrioventricular block

FIGURE 2

Representative images of the vortex during the IVC period and changes in the EL by RVa pacing in the non‐HCM and HCM groups. Representative changes in the vortex during the IVC period (panel A) and EL (panel B) by RVa pacing in the non‐HCM and HCM groups. The dotted lines show the ELcycle during the AAI mode, and the solid lines show that in the DDD mode (panel B). In the non‐HCM group, RVa pacing reduced the vortex area and circulation during the IVC period (panels A‐a and c), and increased the ELsys (panel B‐a). Conversely, in the HCM group, RV pacing enlarged the vortex area and circulation during the IVC period (panels A‐b and d), and decreased the ELsys (panel B‐b). IVC, isovolumetric contraction; EL, energy loss; ELcycle, EL over one cardiac cycle; ELsys, systolic EL; ELdia, diastolic EL; RVa pacing, right ventricular apical pacing; HCM, hypertrophic cardiomyopathy; AAI, single‐chamber pacing; DDD, dual‐chamber pacing; RVa pacing, right ventricular apical pacing

FIGURE 3

Changes in the EL by RVa pacing in the non‐HCM and HCM groups. In the non‐HCM group, the ELsys significantly increased from the AAI to DDD modes. The ELcycle and ELdia did not change from the AAI to DDD modes (upper panels). In the HCM group, the ELcycle and ELsys significantly decreased from the AAI to DDD modes. The ELdia did not change from the AAI to DDD modes (lower panels). EL, energy loss; ELcycle, EL over one cardiac cycle; ELsys, systolic EL; ELdia, diastolic EL; RVa pacing, right ventricular apical pacing; HCM, hypertrophic cardiomyopathy; AAI, single‐chamber atrial pacing; DDD, dual‐chamber pacing

FIGURE 4

Percent change in the vortex area and circulation by RVa pacing in the IVC period between the non‐HCM and HCM groups. The percent changes in the vortex area (panel A) and circulation (panel B) by RVa pacing between the non‐HCM and HCM groups. Compared with the non‐HCM group, the HCM group had a significantly increased percent change in the vortex area and circulation during the IVC period. RVa pacing, right ventricular apical pacing; IVC, isovolumetric contraction; HCM, hypertrophic cardiomyopathy