Prognostic value of heart rate and oxygen pulse response in heart failure with left ventricular ejection fraction over 40

Backgrounds: Heart rate (HR) and stroke volume (SV)-the components of cardiac output-have a complementary relationship. Poor HR increase during exercise is associated with poor exercise tolerance in heart failure (HF) with preserved ejection fraction (HFpEF), but its prognostic impact remains unclear. Furthermore, whether the compensation for poor HR increase with SV during exercise is associated with prognosis remains unknown.

Methods: We evaluated 129 consecutive hospitalized HF patients with sinus rhythm and left ventricular ejection fractions > 40% who underwent cardiopulmonary exercise testing before discharge from the index hospitalization.

Results: Patients (age: 66 [55-74] years; 73% male) were divided into four groups by median HR reserve (HRR; peak-rest HR: 34 bpm) and O₂ pulse, a surrogate for SV, reserve (peak-rest O₂ pulse: 4.8 mL/beat). During a mean follow-up of 562 [294-961] days, cardiovascular events (cardiovascular death and/or HF rehospitalizations) occurred in 24 patients. Kaplan-Meier analysis identified significant differences in outcomes among the four groups (χ² = 27.3, p < 0.001). Using the preserved HRR/preserved O₂ pulse reserve group (n = 33) as a reference, the impaired HRR/impaired O₂ pulse reserve group (n = 37) was associated with poor outcomes (adjusted hazard ratio: 5.66, 95% CI 1.15-27.74, p = 0.033), whereas the impaired HRR/preserved O₂ pulse reserve group (n = 31) was not (adjusted hazard ratio: 0.38, 95% CI 0.03 to 4.76, p = 0.455).

Conclusion: The overlap of lower increases in HR and O₂ pulse, a surrogate for SV, during exercise was associated with an extremely poor prognosis in HFpEF.