Long term outcomes in patients with chronic right ventricular pacing upgraded to cardiac resynchronization therapy

Concepts of Cardiac Dyssynchrony and Dynamic Approach

Cardiac conduction involves electrical activity from one myocyte to another, creating coordinated contractions in each. Disruptions in the conducting system, such as left bundle branch block (LBBB), can result in premature activation of specific regions of the heart, leading to heart failure and increased morbidity and mortality. Structural alterations in T-tubules and the sarcoplasmic reticulum can lead to dyssynchrony, a condition that can be treated by cardiac resynchronization therapy (CRT), which stands as a cornerstone in this pathology. The heterogeneity in patient responses underscored the necessity of improving the diagnostic approach. Vectocardiography, ultra-high-frequency ECG, 3D echocardiography, and electrocardiographic imaging seem to offer advanced precision in identifying optimal candidates for CRT in addition to the classic diagnostic methods. The advent of His bundle pacing and left bundle branch pacing further refined the approach in the treatment of dyssynchrony, offering more physiological pacing modalities that promise enhanced outcomes by maintaining or restoring the natural sequence of ventricular activation. HOT-CRT emerges as a pivotal innovation combining the benefits of CRT with the precision of His bundle or left bundle branch area pacing to optimize cardiac function in a subset of patients where traditional CRT might fall short.

Upgrading right ventricular pacemakers to biventricular pacing or conduction system pacing: a systematic review and meta-analysis

Guidelines recommend patients undergoing a first pacemaker implant who have even mild left ventricular (LV) impairment should receive biventricular or conduction system pacing (CSP). There is no corresponding recommendation for patients who already have a pacemaker. We conducted a meta-analysis of randomized controlled trials (RCTs) and observational studies assessing device upgrades. The primary outcome was the echocardiographic change in LV ejection fraction (LVEF). Six RCTs (randomizing 161 patients) and 47 observational studies (2644 patients) assessing the efficacy of upgrade to biventricular pacing were eligible for analysis. Eight observational studies recruiting 217 patients of CSP upgrade were also eligible. Fourteen additional studies contributed data on complications (25 412 patients). Randomized controlled trials of biventricular pacing upgrade showed LVEF improvement of +8.4% from 35.5% and observational studies: +8.4% from 25.7%. Observational studies of left bundle branch area pacing upgrade showed +11.1% improvement from 39.0% and observational studies of His bundle pacing upgrade showed +12.7% improvement from 36.0%. New York Heart Association class decreased by -0.4, -0.8, -1.0, and -1.2, respectively. Randomized controlled trials of biventricular upgrade found improvement in Minnesota Heart Failure Score (-6.9 points) and peak oxygen uptake (+1.1 mL/kg/min). This was also seen in observational studies of biventricular upgrades (-19.67 points and +2.63 mL/kg/min, respectively). In studies of the biventricular upgrade, complication rates averaged 2% for pneumothorax, 1.4% for tamponade, and 3.7% for infection over 24 months of mean follow-up. Lead-related complications occurred in 3.3% of biventricular upgrades and 1.8% of CSP upgrades. Randomized controlled trials show significant physiological and symptomatic benefits of upgrading pacemakers to biventricular pacing. Observational studies show similar effects between biventricular pacing upgrade and CSP upgrade.

The therapeutic effects of upgrade to cardiac resynchronization therapy in pacing-induced cardiomyopathy or chronic right ventricular pacing patients: a meta-analysis

Pacing-induced cardiomyopathy (PICM) or heart failure accompanied with chronic right ventricular pacing (CRVP-HF) has no established treatments. We aimed to carry out a meta-analysis of published studies about the therapeutic effects of the upgrade to cardiac resynchronization therapy (CRT) in patients of PICM/CRVP-HF. The PUBMED, EMBASE, MEDLINE, OVID databases, and Cochrane Library were systemically searched for relevant publications. Data about the improvements of left ventricular ejection fraction (LVEF), NYHA functional class (NYHA-FC), and the CRT response rate was extracted and synthesized. Mean difference (MD), odds ratio, and standard mean difference (SMD) with 95% confidence interval (CI) were calculated as the effect size by both fixed and random effect models. We included sixteen studies (four about PICM and twelve about CRVP-HF). The total sample size of PICM/CRVP-HF patients was 924. Upgrade to CRT improved the LVEF by 10.87% (95%CI, 8.90 to 12.84%) and reduce the NYHA-FC by around one class (MD, -1.25; 95%CI, -1.43 to -1.06) in PICM/CRVP-HF patients overall. Upgrade to CRT seemed to improve LVEF no less than de-novo CRT (SMD 0.24; 95%CI 0.05 to 0.43; P < 0.05). This meta-analysis suggested that upgrade CRT could improve the cardiac function in PICM/CRVP-HF patients. This strategy may be considered in these patients but require more evidence about the efficacy and procedure-related complications from prospective studies or randomized controlled trials.