Pacing-Induced Electromechanical Ventricular Dyssynchrony Does Not Acutely Influence Right Ventricular Function and Global Hemodynamics in Children with Normal Hearts

Longitudinal Myocardial Deformation Does Not Predict Single Ventricle Ejection Fraction Assessed by Cardiac Magnetic Resonance Imaging in Children with a Total Cavopulmonary Connection

Survival of children with single ventricle heart defects after the total cavopulmonary connection (TCPC) has improved, but impaired cardiac function remains a major cause of morbidity and mortality. Cardiac magnetic resonance imaging (cMRI) is the gold standard in assessing single ventricle volume and function, but high costs and limited availability hamper its routine use. A cheaper and more available alternative is echocardiography. Myocardial function can be studied in more detail using speckle tracking echocardiography (STE). The purpose of the study was to describe the association between myocardial deformation assessed by speckle tracking echocardiography (STE) and single ventricle function assessed by cMRI and to evaluate differences in myocardial deformation in children with single left and single right ventricular morphology. Cross-sectional, multicenter study in 77 children after TCPC was conducted. STE segmental and global longitudinal peak strain and systolic strain rate (SR) of the dominant ventricle were measured. Impaired SV function by cMRI was defined as ejection fraction (EF) < 45%. Mean age was 11.8 (range 9.7-14.3) years. Pearson R for cMRI EF versus global longitudinal strain and SR was - 0.25 (p = 0.06) and - 0.03 (p = 0.82), respectively. Global single ventricle longitudinal strain and SR was similar in patients after TCPC with single left and single right ventricular morphology (- 19.0 ± 3.1% vs 19.2 ± 3.2%, p = 0.94). STE myocardial deformation parameters do not correlate with single ventricle ejection fraction assessed by cMRI.

Effect of Right Ventricular Pacing on Right Ventricular Mechanics and Tricuspid Regurgitation in Patients With High-Grade Atrioventricular Block and Sinus Rhythm (from the Protection of Left Ventricular Function During Right Ventricular Pacing Study)

Right ventricular (RV) pacing has been linked with lead-induced tricuspid regurgitation (TR), left ventricular (LV) dysfunction, and dyssynchrony, but the effect of pacing on RV function is unclear. We sought to investigate the effect of pacing on RV synchrony, RV function, and TR, and their association with LV function. In this substudy of the PROTECT-PACE (Protection of left ventricular function during right ventricular pacing) study of the effects of RV pacing in patients with preserved ejection fraction, 145 patients (76 RV apex and 69 non-RV apex pacing) had measurable RV parameters. We assessed tricuspid annular plane systolic excursion (TAPSE), time difference between peak TAPSE and peak mitral annular plane systolic excursion (TM-APSE-dif), global LV longitudinal strain, E/e', TR vena contracta, and TR peak gradient. Echocardiography was performed just after implantation and at 2 years. TR parameters significantly worsened after 2 years, but pacing site was not associated with changes in RV and TR parameters. No temporal change in TAPSE and TM-APSE-dif was observed overall, but worsening of TM-APSE-dif was associated with worsening TAPSE. Global longitudinal strain and E/e' both deteriorated over 2 years; these changes were significantly associated. In a multivariate regression, worsening global longitudinal strain and worsening TM-APSE-dif were significantly associated with deterioration of TAPSE. Furthermore, increased E/e' and its deterioration were associated with worsening TR vena contracta and TR peak gradient, respectively. Decreased TAPSE was also associated with deterioration of TR vena contracta. In conclusion, RV pacing appears to worsen TR, an effect which might be caused by elevated LV filling pressure due to LV dysfunction. In this study, RV pacing did not affect RV function during 2-year follow-up, but such an effect might occur if RV dyssynchrony or LV dysfunction occurred after pacing. The effect of RV pacing site on RV and TR mechanics was minor.

Pacing of the interventricular septum versus the right ventricular apex: a prospective, randomized study

BACKGROUND

Left ventricular (LV) function may be impaired by right ventricular (RV) apical pacing. The interventricular septum is an alternative pacing site, but randomized data are limited. Our aim was to compare ejection fraction (EF) resulting from pacing the interventricular septum versus the RV apex.

METHODS

RV lead implantation was randomized to the apex or the mid-septum. LVEF and RVEF were determined at baseline and after 1 and 4 years by radionuclide angiography.

RESULTS

We enrolled 59 patients, of whom 28 were randomized to the apical group and 31 to the septal group, with follow-up available in 47 patients at 1 year and 33 patients at 4 years. LVEF in the apical and in the septal groups was 55 ± 8% vs. 46 ± 15% (p=0.021) at 1 year and 53 ± 12% vs. 47 ± 15% (p=0.20) at 4 years. Echocardiography confirmed a mid-septal lead position in only 54% of patients in the septal group, with an anterior position in the remaining patients. In the septal group, LVEF decreased significantly in patients with an anterior RV lead (-10.0 ± 7.7%, p=0.003 at 1 year and -8.0 ± 9.5%, p=0.035 at 4 years), but not in patients who had a mid-septal lead. Left intraventricular dyssynchrony was significantly increased in case of an anterior RV lead. RVEF was not significantly impaired by RV pacing, regardless of RV lead position.

CONCLUSIONS

Pacing at the RV septum confers no advantage in terms of ventricular function compared to the apex. Furthermore, inadvertent placement of the RV lead in an anterior position instead of the mid-septum results in reduced LV function.

Relation of right ventricular pacing site to left ventricular mechanical synchrony

Transvenous pacing leads are regularly placed in the right ventricular (RV) apex. Pediatric patients can develop myopathic changes after long-term RV apical pacing. Left ventricular (LV) mechanical dyssynchrony, estimated with echocardiography, may explain the acute decrease in LV function and long-term histopathologic changes. Ts-4w is an established echocardiographic measurement of LV synchrony, using tissue Doppler imaging (TDI). The purpose of this study was to determine whether TDI could identify acute changes in LV synchrony during pacing from different RV sites. We prospectively measured Ts-4w and Doppler-derived cardiac output after 5 minutes of pacing in 19 subjects undergoing catheter ablation. Each subject underwent pacing at 4 sites in random order: high right atrium, high RV septum (septal), RV outflow tract, and RV apex. Ts-4w was measured during sinus rhythm and each pacing protocol, with a value >65 ms defining mechanical dyssynchrony. Ts-4w during high right atrial (32.6 +/- 17.6 ms) and septal (28.9 +/- 10.9 ms) pacing were not different from sinus rhythm (39.5 +/- 15.5 ms). RV apex (85.7 +/- 18.4 ms) and RV outflow tract (84.2 +/- 20.4 ms) pacing induced mechanical dyssynchrony (p <0.0001). In conclusion, TDI demonstrated significant differences in LV synchrony related to pacing site. Ts-4w may be useful to determine ideal lead placement because it correlates with acutely improved hemodynamics.