Cardiac RehabilitationCV Imaging of Metabolic Interventions

Cardiovascular disease is the leading cause of death worldwide. It is becoming clearer that heart failure (HF) is closely associated with body's metabolism. Even before the heart becomes weaker, it responds to the stresses by changing the fuels it burns, which results in a reduction in the heart's metabolic efficiency that worsens the heart's condition. Since the heart burns so much fuel and consumes fats and carbohydrates along with other available substrates, any changes in its metabolic efficiency could impact metabolism throughout the body. Specifically, HF is characterized by limited flexibility in substrate utilization leading to an overall energetic deficit. Such energetic deficit is associated with progressive remodeling and alter cardiac hemodynamics. For example, obesity is a widely known risk factor for cardiovascular disease likely lie in how the heart handles energy (substrate utilization and energetics). One commonly recommended treatment for cardiovascular disease, especially coronary artery disease (CAD) or congestive heart failure (CHF), is cardiac rehabilitation. Cardiac rehabilitation for symptomatic cardiovascular disease has been shown to promote a healthy lifestyle, improve physical health and reduce cardiovascular death iii with an apparent dose-dependent response. Participation results in a reduced risk of hospitalization and revascularization procedures, and improved functional status in randomized controlled trials. Thus, cardiac rehabilitation is recommended for individuals with symptomatic CAD or CHF by the American College of Cardiology and American Heart Association. In addition, exercise training in preclinical animal models mirroring the exercise component of cardiac rehabilitation routines have shown increased myocardial regeneration and cardioprotective molecular effects ameliorating adverse myocardial remodeling. Despite these benefits, there is vast heterogeneity in the efficiency of cardiac rehabilitation on the individual level with large variances in improved exercise capacity and cardiac function recovery. Personalization of cardiac rehabilitation necessitates a non-invasive approach to monitor the direct beneficial effects on the heart and more ideally, predict efficacy at baseline. Taken together, understanding how metabolic interventions including bariatric surgery and cardiac rehabilitation change myocardial structure and function is critical for the prevention, diagnosis and prognosis for patients with cardiovascular diseases.

Advanced cardiovascular imaging using Magnetic Resonance Imaging (MRI) has proven to be effective in providing gold standard myocardial tissue characterization. Our team has developed novel cardiac MRI techniques that leverages endogenous tissue properties to reveal a milieu of deep tissue phenotypes including myocardial inflammation, fibrosis, metabolism, and microstructural defects. Among these phenotypes, myocardial microstructure has proven to be most sensitive to early myocardial tissue damage and is predictive of myocardial regeneration. In collaboration with cardiologists at Cleveland Clinic, the investigators aim to study how myocardial microstructure revealed by cardiac MRI changes cardiovascular disease patient population before and after metabolic interventions.