Fatty Heart and Subclinical Left Ventricular Dysfunction Rediscovery of a Pathological Metabolic Process : With a Twist

Fatty degeneration of the human heart was first reported by the French cardiologist Corvisart more 200 years ago in 1806, while the first distinction of epicardial/pericardial fat from intramyocardial fat was made by the German physician scientist Virchow in 1858. Interest in these observations and their cardiovascular consequences continue to grow as techniques for noninvasive assessment of pericardial and intramyocardial fat improve. The amount of fat stored in nonadipocyte tissue (liver and muscle) is usually minimal and tightly regulated; however, recent studies have reported cardiac steatosis in human metabolic diseases such as obesity, diabetes mellitus, and metabolic syndrome. Mahmod et al, in this issue of Circulation: Cardiovascular Imaging, compared 39 subjects with symptomatic (64%) and asymptomatic severe aortic stenosis (AS) to 20 healthy controls and found increased myocardial fat in patients with AS. Using H-magnetic resonance (MR) spectroscopy, the authors measured myocardial triglyceride content (MTC) and reported that patients with symptomatic AS had the highest level of MTC as compared with asymptomatic patients and healthy control subjects. MTC values correlated inversely with regional myocardial function using circumferential and longitudinal strain obtained by myocardial tagging methods, with a gradation between the control, asymptomatic AS, and symptomatic AS groups. The authors were able to show a modest correlation of MTC with myocyte lipid content on biopsy samples of a subgroup of patients who underwent surgery (r s =0.66; P=0.036). Most importantly, the authors demonstrated near complete reversal of myocardial steatosis and circumferential (but not longitudinal) myocardial systolic dysfunction in the first year after aortic valve replacement (AVR) surgery. These findings were not significantly correlated to the patients’ metabolic status and seem to be specific to the degree of hypertrophic state as they are dose dependent; increasing with symptomatic AS, and reversible when treated with AVR.