Diagnosing chronotropic incompetence: a scoping review of current approaches and their application in a cardiac rehabilitation cohort

AIMS: Chronotropic incompetence (CI), defined as the inability of the heart to appropriately increase its rate in response to exercise, is associated with exercise intolerance and adverse events. However, the diagnostic criteria for CI vary widely, limiting their clinical applicability and comparability across studies. Here we aim to systematically map the current definitions of CI and the prediction models used to estimate age-predicted maximal heart rate (APMHR). We illustrate how this diagnostic variability affects the identification of CI in patients enrolled in a cardiac rehabilitation program. METHODS: A scoping review systematically identified all published definitions of CI and prediction models for APMHR. A retrospective study evaluated the agreement between definitions in patients participating in cardiac rehabilitation. RESULTS: A total of 86 studies were included. Seventeen distinct methods to define CI were identified, ranging from absolute or relative peak heart rate parameters to approaches incorporating workload. In many cases, the applied cut-off values lacked a rationale. In parallel, numerous APMHR formulas were identified, differing by sex, age category, fitness level, clinical status, and the use of beta-blocker therapy, showing limited accuracy. In the clinical setting agreement between four major definitions was poor and pairwise comparisons between them showed significant differences in classification. CONCLUSION: Current methods to define CI and predict APMHR are inconsistent and problematic. This review provides a practical framework for selecting a context-appropriate definition and formula. It identifies current methodological gaps and highlights the need for future research to establish a consensus definition of CI.