Heart Rate Recovery Index as a Novel Marker in Heart Failure Assessment: A Comparative Analysis of Heart Rate Deceleration During Exercise Testing

Purpose: Heart rate recovery, measured during exercise testing, is an important marker of cardiovascular function. The Heart Rate Recovery Index, a recently proposed parameter derived from heart rate recovery, has shown predictive outcomes in patients undergoing cardiac resynchronization therapy. However, its role in heart failure identification remains unexplored. This study aimed to assess differences in the heart rate recovery index between patients with heart failure and individuals without heart failure undergoing exercise testing. Patients and Methods: 194 patients (mean age 58.3 ± 11.7 years; 57.7% men) with heart failure or other cardiovascular conditions requiring exercise testing were prospectively enrolled and underwent cycle ergometer testing. The index was calculated as the ratio between heart rate acceleration and deceleration time during exercise testing. Differentiation ability was assessed using receiver operating characteristic curve analysis. Subgroup and two-step cluster analyses examined heart rate recovery index differences across heart failure phenotypes and severity. Results: < 0.01). Cluster analysis identified four phenotypic groups, with the index helping to differentiate early or less severe from advanced heart failure, according to the ejection fraction. Conclusion: HRRI is a simple parameter that distinguishes the heart failure status and provides discrimination across its phenotypes. Its strong correlation with echocardiographic and functional markers supports its potential role in the assessment and characterization of heart failure.