Four established definitions of chronotropic incompetence yielded widely varying prevalence rates in cardiac rehabilitation patients, ranging from 5.7% to 72.4% (all pairwise comparisons p<0.001).
Observational (n=2,869)
How do different diagnostic criteria for chronotropic incompetence affect its identification and agreement in patients undergoing cardiac rehabilitation?
The diagnosis of chronotropic incompetence varies drastically depending on the criteria used, emphasizing the urgent need for a standardized universal definition.
p-value: p=<0.001
Abstract Background/Introduction 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. Yet, there is no consensus on the definition of CI and its diagnostic criteria vary widely, causing confusion among healthcare providers and limiting comparability across studies. Purpose This study aimed to compare multiple definitions of CI to explore how these differences in diagnostic criteria affect the identification of CI in patients enrolled in a cardiac rehabilitation program and to evaluate the level of agreement among them. Methods In this retrospective study, we assessed CI in 2,869 patients enrolling in a cardiac rehabilitation program. Cardiopulmonary exercise testing was performed on a cycle ergometer until volitional exhaustion. CI was defined using four established methods: 85% of age-predicted maximal heart rate (APMHR); heart rate reserve (HRR) 80%, calculated as (HRpeak − HRrest) / (APMHR − HRrest); chronotropic index (CIx) 0.8 at the first ventilatory threshold (VT1), where CIx = (HRVT1 − HRrest) / (HRpeak − HRrest) / (VO2VT1 − VO2rest) / (VO2peak − VO2rest); and peak HR slope method, where CI is present if the slope of HR versus VO2 is below the reference - 1.96 x SE and VO2peak 70% of predicted. APMHR was calculated using drug-adjusted formulas (183 − 0.76 ×age for patients on negative chronotropic drugs; 210 − 0.91×age otherwise). Predicted VO2peak was calculated using the Gläser formula. Agreement between definitions was assessed using McNemar tests (p0.05). In a sensitivity analysis, all calculations were repeated in patients who achieved a maximal effort as defined by a respiratory exchange ratio 1.1 (n=2,233). Results The proportion of patients classified as having CI varied considerably across definitions: 33.6% with APMHR, 46.8% with HRR, 72.4% with CIx at VT1, and 5.7% with the peak HR slope (Figure 1). Agreement between definitions was poor and all pairwise comparisons showed significant differences in classification (all p0.001). Similar discrepancies were observed in the subgroup achieving maximal effort, with corresponding proportions of 28.0%, 40.9%, 69.9%, and 3.5%. Notably, the peak HR slope definition consistently identified a markedly smaller subset of patients with CI. Conclusion Depending on the chosen definition, the proportion of patients classified as having CI ranged from as low as 5.7% (peak HR slope) to over 70% (CIx at VT1). Therefore, patient classification is highly dependent on the definition applied. A universal definition of CI is needed to enhance consistency in diagnosis, risk stratification, and therapeutic decision-making.Overlap in CI definitionsFor image description, please refer to the figure legend and surrounding text.
Vermeiren et al. (Mon,) conducted a observational in Chronotropic incompetence (n=2,869). Chronotropic incompetence definitions was evaluated on Agreement between four definitions of chronotropic incompetence (p=<0.001). Four established definitions of chronotropic incompetence yielded widely varying prevalence rates in cardiac rehabilitation patients, ranging from 5.7% to 72.4% (all pairwise comparisons p<0.001).