Chronotropic Incompetence During Exercise in Obese Adolescents: Clinical Implications and Pathophysiology

A reduction in peak heart rate (HR) and suppressed HR response during exercise is highly prevalent in obese populations. This phenomenon is also known as chronotropic incompetence (CI). In adult obese individuals, CI is independently related to elevated risk for major adverse cardiovascular events and premature death. Despite the established association between CI and prognosis in adult populations, the prognostic relevance of CI in adolescents with obesity has however deserved no attention, but is important. CI during exercise testing may indicate various, yet undetected anomalies, such as altered blood catecholamine and/or potassium concentrations during exercise, structural myocardial abnormalities or ventricular stiffness, impaired baroreflex sensitivity and cardiovascular autonomic dysfunction, atherosclerosis, or cardiac electrophysiological anomalies, which all have been detected in obese children and adolescents. However, whether CI during exercise testing may be a sensitive and specific indicator for these anomalies in obese adolescents has not been studied yet. In addition, the exact physiology behind obesity and development of heart disease remains to be studied in greater detail in obese adolescents. In this project, we examine the prevalence of CI (during maximal cardiopulmonary exercise testing, CPET) in 60 obese adolescents (aged 12-16 years) vs. 60 lean adolescents, and study the association between CI and changes in CPET parameters, lactate, catecholamine and potassium concentrations during CPET, biochemical variables, and cardiac electrophysiology (by ECG recording). In addition, the relation between CI and cardiac function (echocardiography) will be examined in a subgroup (29 lean and 29 obese) of these adolescents. In this regard, the diagnostic value of HR (responses) during maximal exercise testing will be clarified in obese adolescents, and the physiology behind the elevated risk for heart disease in obese adolescents can be explored.