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Biventricular Pacing Is Superior to Right Ventricular Pacing in Bradycardia Patients With Preserved Systolic Function: 2-Year Results of the PACE Trial
Study Questions:
Does biventricular (BiV) pacing remain superior to right ventricular apical (RVA) pacing after longer-term follow-up of patients with preserved systolic function and bradycardia?
Methods:
Patients (n = 177) enrolled in the Pacing to Avoid Cardiac Enlargement (PACE) trial underwent double-blind randomization to BiV (n = 89) pacing versus RVA (n = 88) pacing. At baseline, all patients had preserved systolic function (left ventricular ejection fraction [LVEF] ≥45%) and a standard indication for pacing. Patients were followed up at 18 and 24 months. The coprimary endpoints of interest were LVEF and LV systolic volume (LVSV) measured by echocardiogram. Secondary endpoints included 6-minute hall walk distance and Short Form (SF)-36 quality of life measurements.
Results:
Complete follow-up occurred in 92% (n = 81) of RVA paced patients and 92% (n = 82) of BiV paced patients at 24 months. Pacing burden averaged (mean ± standard deviation) 97.9 ± 11.8% in the RVA group and 92.9 ± 22.6% in the BiV pacing group (p = 0.95). While there were no LVEF differences at baseline, patients in the BiV pacing group had a higher LVEF (by 9.9% points) and a lower LVSV (by -13 ml) at 24 months compared with those receiving isolated RVA pacing (both p < 0.001). LVEF did not change over time in the BiV pacing group (p = 0.68). In the RVA pacing group, there was a significant decrement in LVEF between baseline (62 ± 4%), 18 months (56.2 ± 9.4%), and 24 months (53.5 ± 10.1%) of follow-up (p < 0.001). An LVEF reduction of ≥5% was encountered in 20% of BiV paced patients compared with 63% of RVA patients (p = 0.006). Similarly, LVSV increased significantly from baseline (27.6 ± 9.1 ml) at 18 months (33.3 ± 13.3 ml) and 24 months (35.6 ± 16.7 ml) in the RVA pacing group (p < 0.001). No significant change was noted in LVSV in BiV paced patients between baseline (27.6 ± 9.2 ml) and 18 months (26.5 ± 10.4 ml) and 24 months (25.5 ± 10.7 ml, p = 0.19). No significant difference or strong trend was noted between pacing modalities in SF-36 scores or 6-minute walk distances at follow-up.
Conclusions:
The authors concluded that BiV pacing prevents LV remodeling and EF decline in patients requiring pacemaker support.
Perspective:
In this extension of the PACE study, the authors have again shown that the application of BiV pacing is less likely to lead to a decline in LV systolic function in patients with conventional pacemaker indications. Compared with the first 12 months of follow-up, the adverse changes in LVEF and LVSV with RVA pacing were of smaller magnitude between 12 and 24 months after implant. The rate of decrement over the long-term is of particular interest since most patients requiring conventional pacing are older (mean age of 69 years in this study) and the clinical impact (6-minute walk distance, hospitalization, survival, quality of life) of BiV versus RVA pacing has not yet been demonstrated in this patient population.
Keywords: Follow-Up Studies, Azepines, Cardiac Resynchronization Therapy, Heart Diseases, Cardiomegaly, Cardiac Pacing, Artificial, Cardiology, Heart Failure, Naphthalenes, Pacemaker, Artificial, Bradycardia, Heart Ventricles
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