The Prevalence and Short-Term Outcomes of Ventricular Dyssynchrony after Right Ventricular Pacing

Objective: Long-term right ventricular pacing has been associated with an increased risk of heart failure and cardiomyopathy. The pathophysiology of cardiomyopathy associated with right ventricular pacing remains unclear. We aim to evaluate the burden and short-term outcomes of ventricular dyssynchrony after immediate permanent pacemaker implantation. Materials and Methods: This prospective cohort study examined consecutive patients who had permanent pacemaker implantation at Vajira Hospital in 2019. Left ventricular systolic function, specifically left ventricular ejection fraction (LVEF) and echocardiographic ventricular dyssynchrony parameters were assessed. The endpoints included the prevalence of ventricular dyssynchrony, new-onset cardiomyopathy, heart failure, and death. The correlation between QRS complex duration, the burden of ventricular pacing, and echocardiographic ventricular dyssynchrony was measured. Results: Thirty-six consecutive patients underwent pacemaker implantation. The prevalence of mechanical ventricular dyssynchrony was 22.2% using the interventricular conduction delay method, 41.7% using LV pre-ejection period method, and 11.1% using the septal posterior wall motion abnormality method. Electrical ventricular dyssynchrony was 86.1% and new-onset cardiomyopathy was 17.1% after 3 months of permanent pacemaker implantation. The right ventricular pacing of more than 20% was significantly associated with cardiomyopathy (p < 0.022) and heart failure (log-rank, p = 0.049) within 3 months. But heart failure was not associated with mechanical ventricular dyssynchrony parameters (log-rank, p = 0.610;hazard ratio [HR], 1.53;95% confidence interval [CI], 0.29 - 7.96;p = 0.613 for IVMD and log-rank, p = 0.398;HR, 0.04;95% CI, 0.01 - 3316.7 for SPWMD). Conclusion: Mechanical and electrical ventricular dyssynchrony are common findings in right ventricular pacing. High-burden right ventricular pacing after 3 months of permanent pacemaker implantation is often associated with cardiomyopathy and heart failure, but mechanical and electrical ventricular dyssynchrony does not predict a short-term decline in left ventricular systolic function and heart failure.

Echocardiographic Evaluation of Cardiac Dyssynchrony in Patients with Congestive Heart Failure

The present study investigated the application of echocardiography to evaluation of cardiac dyssynchrony in patients with congestive heart failure（CHF）. A total of 348 consecutive CHF patients who were admitted for cardiac resynchronization（CRT） and presented with low ejection fraction（EF） and wide QRS duration were enrolled in this study, along with 388 healthy individuals. Dyssynchrony was assessed based on filling time ratio（FT/RR）, left ventricular pre-ejection delay（PED）, interventricular mechanical delay（IVMD）, longitudinal opposing wall delay（LOWD） and radial septal to posterior wall delay（RSPWD）. Response to CRT was defined as a ≥15% increase in EF. The results showed that FT/RR was decreased while PED, IVMD, LOWD and RSPWD were increased in the CHF group compared with the control group（P〈0.01）. In the CHF group, FT/RR was negatively correlated with the QRS duration, LV end-diastolic diameter（LVESd）, LV end-diastolic volume（LVEDV） and LV end-systolic volume（LVESV）（P〈0.01）, but positively with the LVEF（P〈0.01）. Additionally, PED, IVMD, LOWD and RSPWD were positively correlated with the QRS duration, LVESd, LVEDV and LVESV（P〈0.01）, but negatively with the LVEF（P〈0.01）. The CHF group was divided into three subgroups according to the varying degrees of LVEF. FT/RR decreased successively from the LVEF-1 group to the LVEF-2 group to the LVEF-3 group, while the PED, IVMD, LOWD and RSPWD successively increased in the same order（P〈0.01）. The CHF group was divided into three subgroups according to the varying degrees of QRS duration, and FT/RR decreased successively in a sequence from the QRS-1 group to the QRS-2 group to the QRS-3 group, while the PED, IVMD, LOWD and RSPWD successively increased in the same order（P〈0.01）. Speckle tracking radial dyssynchrony ≥130 ms was predictive of an EF response in patients in QRS-1 group（78% sensitivity, 83% specificity）, those in QRS-2 group（83% sensitivity, 77% specificity） and in QRS-3 group（89% sensitivity, 79% specificity）. In conclusion, echocardiography is a convenient and sensitive method for evaluating cardiac dyssynchrony in patients with CHF.