Griffith GJ; Northwestern University Feinberg School of Medicine, Department of Physical Therapy and Human Movement Sciences, USA

International journal of cardiology [Int J Cardiol] 2025 May 31; Vol. 437, pp. 133445.
Date of Electronic Publication: 2025 May 31.

Chronotropic incompetence (CI) is characterized by an inadequate or blunted heart rate (HR) response to exercise, [1] and the clinical and prognostic importance of CI is being increasingly recognized. Associations between CI and mortality [2,3] and exercise capacity [4] have been demonstrated in a variety of cardiovascular disease patient populations. In this issue of the International Journal of Cardiology, the original research article by Smarz and colleagues further established the importance of CI to a population of post-myocardial infarction (MI) patients with preserved or mildly reduced ejection fraction. [5] This compelling research article provides important insight into the prognostic benefit of identification of CI and importantly highlights that methodological considerations relating to the assessment of CI are of the utmost importance. Firstly, there exists a general lack of universal agreement regarding the mathematical and functional definition of CI. Secondly, implementation of cardiopulmonary exercise testing (CPET) is oftentimes underutilized, and the multitude of variables obtained from it are rarely optimized in the characterization of patient prognosis following maximal exercise testing. The aims of this article are to 1) provide insight into best methodological practices surrounding CI as identified via CPET, 2) contextualize the importance of CI in MI patients, and 3) provide recommendations for future avenues of research to continue to build the body of evidence surrounding the importance of CPET and CI.