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Prolonged PR Interval and Outcomes of CRT
Study Questions:
What is the relationship between PR interval and outcomes in patients undergoing cardiac resynchronization therapy (CRT) implantations?
Methods:
The investigators conducted inverse probability weighted analyses of 26,451 CRT-eligible patients from the National Cardiovascular Data Registry ICD Registry. Patients were stratified in terms of a prolonged PR interval (≥230 ms), and whether they received CRT with defibrillator (CRT-D) or just implantable cardioverter-defibrillator (ICD). Patients were followed up to 5 years for heart failure (HF) hospitalization or death.
Results:
Patients with a PR ≥230 ms were older and had more comorbidities including coronary artery disease, atrial arrhythmias, diabetes, and chronic kidney disease. After risk-adjustment, a prolonged PR was associated with increased risk of HF hospitalization or death among CRT-D (hazard ratio [HR], 1.23; confidence interval [CI], 1.14-1.31; p < 0.001), but not ICD recipients (HR, 1.08; CI, 0.97-1.20; p = 0.17) (p interaction = 0.043). CRT-D (vs. ICD) was associated with lower rates of HF hospitalization or death among patients with PR <230 ms (HR, 0.79; CI, 0.73-0.85; p < 0.001), but not PR ≥230 ms (p = 0.90) (p interaction = 0.0025).
Conclusions:
A PR ≥230 ms is associated with increased rates of HF hospitalization or death among CRT-D patients. The real-world comparative effectiveness of CRT-D (vs. ICD) is significantly less among patients with a PR ≥230 ms compared to patients with a PR <230 ms.
Perspective:
Prior studies have repeatedly demonstrated worse outcomes in patients with HF and long QRS interval, and CRT-D is associated with greater benefit in patients with very long QRS, especially left bundle branch block. The present study suggests that prolonged PR interval is also associated with increased risk of adverse outcomes, but only in patients with CRT-D, not ICD. It is not clear why that may be. A prolonged PR interval may be detrimental to diastolic filling because it leads to a decrease in diastolic filling time. Prior studies showed that AV optimization in CRT patients had limited usefulness, but as the authors suggest, patients with prolonged PR interval may be a subgroup, which might benefit from echo optimization. This hypothesis should be explored in future studies.
Keywords: Arrhythmias, Cardiac, Bundle-Branch Block, Cardiac Resynchronization Therapy, Coronary Artery Disease, Defibrillators, Defibrillators, Implantable, Diabetes Mellitus, Heart Conduction System, Heart Failure, Hospital Mortality, National Cardiovascular Data Registries, Renal Insufficiency, Chronic, Secondary Prevention
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