Functional Muscle Characteristics and Cardio-respiratory Interaction in Patients With Fontan Palliation

Congenital heart disease (CHD) is the most common congenital defect, affecting about 1% of newborns. Among adults surviving complex CHD, the cohort of survivors after the Fontan palliation for univentricular physiology is the most rapidly growing. Given their unique physiology without a pumping chamber supporting the pulmonary circulation, their exercise capacity as adults is often severely reduced. Therefore, patients with grown-up CHD typically need long-term expert medical care causing constantly increasing healthcare- related costs. Specific exercise regimes might offer a safe, efficacious and cost-effective alternative to pharmacologic interventions and surgery. The underlying mechanisms of impaired exercise capacity in Fontan patients are, however, not fully understood and consequently, training regimes specifically tackling the limiting factors cannot be developed. In patients with CHD, studies have suggested that exercise limitations are secondary to the cardiac defects, factors related to cardiac surgery, chronotropic incompetence and underlying lung disease. Similar to heart failure patients, exercise limitations could be traced back to insufficient respiratory and leg muscle functions and impaired cardiovascular regeneration processes possibly due to an altered stem cell number and function in the peripheral blood.

The present study will investigate cardiac, respiratory and quadriceps muscle function at rest and during submaximal and maximal whole-body exercises. A special focus will be given on respiratory and quadriceps muscle strength, and proneness of these muscles to fatigue, which has not yet been objectively investigated. Moreover, different respiratory muscle training (RMT) protocols will be executed, to assess the safety of these interventions. Moreover, the current study will be the first to investigate the influence of exhaustive exercise protocols on the number and function of circulating stem and progenitor cells (CPCs) in Fontan patients. The number of these cell populations was shown to strongly correlate with long-term outcome and recovery in several diseases. This study aims to reveal whether Fontan patients show similarly alternated stem cell number and function in the peripheral blood, that likely result in impaired vascular regeneration processes and possibly also contribute to reduced exercise capacity.