Chronic Effect of Right Ventricular Pacing on Left Ventricular Rotational Synchrony in Patients with Complete Atrioventricular Block

Acute impact of pacing at different cardiac sites on left ventricular rotation and twist in dogs

Objectives

We evaluated the acute impact of different cardiac pacing sites on two-dimensional speckle-tracking echocardiography (STE) derived left ventricular (LV) rotation and twist in healthy dogs.

Methods

Twelve dogs were used in this study. The steerable pacing electrodes were positioned into right heart through the superior or inferior vena cava, into LV through aorta across the aortic valve. The steerable pacing electrodes were positioned individually in the right atrium (RA), right ventricular apex (RVA), RV outflow tract (RVOT), His bundle (HB), LV apex (LVA) and LV high septum (LVS), individual pacing mode was applied at 10 minutes interval for at least 5 minutes from each position under fluoroscopy and ultrasound guidance and at stabilized hemodynamic conditions. LV short-axis images at the apical and basal levels were obtained during sinus rhythm and pacing. Offline STE analysis was performed. Rotation, twist, time to peak rotation (TPR), time to peak twist (TPT), and apical-basal rotation delay (rotational synchronization index, RSI) values were compared at various conditions. LV pressure was monitored simultaneously.

Results

Anesthetic death occurred in 1 dog, and another dog was excluded because of bad imaging quality. Data from 10 dogs were analyzed. RVA, RVOT, HB, LVA, LVS, RARV (RA+RVA) pacing resulted in significantly reduced apical and basal rotation and twist, significantly prolonged apical TPR, TPT and RSI compared to pre-pacing and RA pacing (all P<0.05). The apical and basal rotation and twist values were significantly higher during HB pacing than during pacing at ventricular sites (all P<0.05, except basal rotation at RVA pacing). The apical TPR during HB pacing was significantly shorter than during RVOT and RVA pacing (both P<0.05). The LV end systolic pressure (LVESP) was significantly lower during ventricular pacing than during pre-pacing and RA pacing.

Conclusions

Our results show that RA and HB pacing results in less acute reduction on LV twist, rotation and LVESP compared to ventricular pacing.

New approach for rotational dyssynchrony using three-dimensional speckle tracking echocardiography

Left ventricular (LV) twist can be evaluated using two-dimensional speckle tracking echocardiography (2DSTE) by analyzing difference between apical and basal rotation. However, it is unable to evaluate global rotational dyssynchrony because it cannot assess mid-wall rotation. Recently developed three-dimensional STE (3DSTE) can investigate LV global rotational dyssynchrony. In this study, we investigated the role of torsion on the long-term effects of cardiac resynchronization therapy (CRT) using 3DSTE. We evaluated 43 patients by 3DSTE: 12 CRT responders, 14 CRT nonresponders, and 17 healthy normal controls. Regional torsion and rotation were assessed using 3DSTE across 16 segments during CRT-off (native conduction) and CRT-on. The following parameters were calculated: global peak twist, Δ global peak twist (difference between CRT-on and CRT-off), and torsion delay index. The torsion delay index was considered to be the rotational energy lost by rotational dyssynchrony. Global peak twist did not show significant differences between the responders and nonresponders during CRT-off (4.0 ± 3.4° vs. 2.8 ± 2.3°, P = 0.295), but it significantly improved in responders compared to nonresponders after CRT-on (5.4 ± 3.5° vs. 2.6 ± 2.6°, P = 0.029). The torsion delay index during CRT-off was significantly higher in responders compared to nonresponders and normal controls (18.5 ± 11.3 vs. 8.6 ± 3.8 and 7.8 ± 5.5, P = 0.010 and P = 0.004, respectively). The torsion delay index during CRT-off significantly correlated with the Δ global peak twist (r = 0.503, P = 0.009). Improvement in LV global peak twist, which is one of the mechanisms for the long-term effects of CRT correlated with the torsion delay index during native conduction that can only be calculated by 3DSTE.

Global and regional right ventricular dysfunction in pulmonary hypertension

BACKGROUND

Pulmonary hypertension (PH) is known to affect the right ventricular (RV) function.

AIMS

To assess the extent of global and regional RV dysfunction in PH patients.

METHODS

We performed a cross-sectional study on 20 controls (age 62 ± 15 years, 7 males) and 35 patients (age 67 ± 12 years, 13 males) with PH of mixed etiologies and assessed RV inflow and outflow tracts (OTs) function, using speckle tracking echocardiography (STE) based myocardial deformation and its time relations. RV inlet and OT dimensions (2D), inlet myocardial velocities (TDI), myocardial strain and strain rate (SR), TAPSE (M-mode), ejection and filling times (pulsed-wave [PW] Doppler), and pulmonary artery acceleration (PAc) were measured.

RESULTS

RV inlet and OT were dilated (P < 0.001 for both) and TAPSE (P < 0.001), inlet velocities (P < 0.001), basal and mid-cavity strain, SR and longitudinal displacement reduced (P < 0.001 for all). The time to peak systolic SR at basal, mid-cavity (P < 0.001 for both), and RVOT (P = 0.007) was short as was that to peak displacement (P < 0.001 for all). The time to peak pulmonary ejection correlated with time to peak SR at RVOT (r = 0.7, P < 0.001) in controls, but with that of the mid-cavity in patients (r = 0.71, P < 0.001). PAc was faster (P = 0.001) and RV filling time shorter in patients (P = 0.03) with respect to controls.

CONCLUSIONS

PH has drastic effects on RV structure and intrinsic myocardial function, significantly disturbing its ejection time relations and overall pump performance. Increased RV afterload results in RV configuration changes with the inflow tract determining peak ejection rather than OT.