Case‐control study of heart rate abnormalities across the breast cancer survivorship continuum

BACKGROUND: Mechanisms underlying impaired exercise capacity and increased cardiovascular mortality observed in breast cancer (BC) patients remain unclear. The prevalence, functional, and prognostic significance of elevated resting heart rate (HR) and abnormal heart rate recovery (HRR) in breast cancer (BC) requires evaluation. METHODS: In a single‐center, retrospective, case‐control study of women referred for exercise treadmill testing (ETT), 448 BC patients (62.6 ± 10.0 years) were compared to 448 cancer‐free, age‐matched controls. Elevated resting HR was defined as HR ≥80 bpm at rest. Abnormal HRR at 1‐minute following exercise was defined as ≤12 bpm if active recovery or ≤18 bpm if passive recovery. Association of these parameters with exercise capacity and all‐cause mortality was evaluated. RESULTS: Elevated resting HR (23.7% vs 17.0%, P = 0.013) and abnormal HRR (25.9% vs 20.3%, P = 0.048) were more prevalent in BC cohort than controls. In adjusted analyses, BC patients with elevated resting HR (−0.9 METs (SE 0.3); P = 0.0003) or abnormal HRR (−1.3 METs (SE 0.3); P < 0.0001) had significant reductions in metabolic equivalents (METs) achieved during exercise. Elevated resting HR was not associated with mortality. There was a trend toward increased mortality in BC cohort with abnormal HRR (adjusted hazard ratio 2.06 (95% CI 0.95‐4.44, P = 0.07)). CONCLUSIONS: Women across the BC survivorship continuum, referred for ETT, have an increased prevalence of elevated resting HR and abnormal HRR relative to cancer‐free, age‐matched female controls. These parameters were associated with decreased exercise capacity. Strategies to modulate these abnormalities may help improve functional capacity in this cohort.