Cardiopulmonary Exercise Testing in the Differential Diagnosis Between Athlete's Heart and Cardiac Pathology: Current Evidence and Diagnostic Challenges.

Sports cardiologists frequently face the challenge of distinguishing physiological cardiac adaptation to intensive training ("athlete's heart") from early or mild cardiac pathology, a dilemma in which both false-positive and false-negative assessments carry meaningful consequences for the athlete. Cardiopulmonary exercise testing (CPET) provides a dynamic, functional complement to structural and electrical assessment, but its value in this specific differential-diagnosis context has not been comprehensively synthesized. This narrative review examines current evidence on CPET in distinguishing athlete's heart from hypertrophic cardiomyopathy, dilated cardiomyopathy, arrhythmogenic cardiomyopathy, and thoracic wall deformities such as pectus excavatum, alongside the physiological basis of high exercise capacity in athletes and the athlete-specific reference values now becoming available. Across conditions, peak oxygen uptake alone proved an unreliable discriminator. Ventilatory efficiency, oxygen-pulse kinetics, and the exercise arrhythmic and blood-pressure response appear to carry additional information when interpreted within a multiparametric framework, although the supporting studies are observational, mostly single-centre, and were not designed to compare these variables against one another. Special populations, including veteran athletes, women, and those with congenital heart disease, require dedicated reference data that remain incomplete, and emerging artificial-intelligence-based interpretive tools require athlete-specific validation before clinical adoption. A practical, stepwise diagnostic framework integrating CPET with imaging and shared decision-making is proposed. It reflects the authors' synthesis of the reviewed evidence rather than a prospectively validated or society-endorsed pathway. Closing the evidence gaps identified here, particularly for underrepresented athlete populations and prospective outcomes data, should be a priority for future research in sports cardiology.