Optimizing Patient Selection for Physiological Pacing in Bradyarrhythmia: Factors Associated With High Ventricular Pacing Burden

Background

Right ventricular (RV) pacing is established as the most common ventricular pacing (VP) strategy for patients with symptomatic bradyarrhythmia. Some patients with high VP burden suffer deterioration of left ventricular (LV) function, termed pacing-induced cardiomyopathy (PICM). Patients who pace > 20% of the time from the RV apex are at increased risk of PICM, but independent predictors of increased RV pacing burden have not been elucidated in those who have a permanent pacemaker (PPM) inserted for bradyarrhythmia.

Methods

We aimed to identify factors that are associated with increased VP burden > 20%, hence determining those at risk for resultant PICM. In this retrospective cohort study, we identified the most recent 300 consecutive cardiac implantable electronic device (CIED) implants in our center and collected past medical history, electrocardiogram (ECG), echo, medication and pacemaker check data.

Results

A total of 236 individuals met inclusion criteria. Of the patients, 35% had RV pacing burden < 20%, while 65% had VP burden ≥ 20%; 96.2% of patients with complete heart block (CHB) paced > 20% (P = 0.002). Utilization of DDD or VVI (75.2% and 89.2% of patients, respectively) without mode switch algorithms was associated with VP > 20% (P < 0.001). Male or previous coronary artery bypass grafting (CABG) patients also statistically paced > 20%. Other factors trending towards significance included prolonged PR interval, atrial fibrillation or more advanced age.

Conclusion

High-grade atrioventricular (AV) block was associated with an RV pacing burden > 20% over 3 years but this was not consistent in patients with only transient episodes of high-grade AV block. We found a significant association between high VP% and male sex, previous CABG and the absence of mode switching algorithms.

Long-term effect of β-blocker in ST-segment elevation myocardial infarction in patients with preserved left ventricular systolic function: a propensity analysis

The current guidelines for acute myocardial infarction (AMI) recommended that β-blocker should be used in patients with decreased left ventricular (LV) systolic function for long-term period. However, the effect of β-blocker in AMI patients with preserved LV systolic function is uncertain. We sought to assess the long-term effect of β-blocker in AMI patients with preserved LV systolic function. During the follow-up period (1997-2011), total 3508 patients were performed percutaneous coronary intervention (PCI). Of these patients, 424 AMI patients with preserved LV systolic function [ejection fraction (EF) > 40 %] were analyzed. Median follow-up period was 4.7 years. Then, patients were divided into two groups (β-blocker group 197 patients and no-β-blocker group 227 patients). However, there are substantial differences in baseline characteristics between two groups. Therefore, we calculated propensity score to match the patients in β-blocker and no-β-blocker groups. After post-match patients (N = 206, 103 matched pair), β-blocker therapy significantly reduced cardiac death compared with no-β-blocker [hazard ratio (HR) 0.40, p = 0.04], whereas β-blocker therapy was not associated with major adverse cardiac events (MACE) and all-cause death. β-Blocker is an effective treatment for AMI patients who underwent PCI with preserved LV systolic function.