Abstract 839: The Effects of Catecholamine Stress and Weight Loss on Myocardial Relaxation and High Energy Phosphate Metabolism in Obesity
Obesity may lead to altered cardiac energetics, exacerbating diastolic dysfunction. Thus, we investigated
whether diastolic dysfunction in obesity is worsened by inotropic stress,
whether catecholamine stress further exacerbates the energetic deficit seen in obesity and
whether weight loss reverses the diastolic dysfunction and energy deficit observed in obesity.
Method: 17 normal weight (BMI 21.6±1.6) and 30 obese subjects (BMI 39.8±8.0) were studied with cardiac magnetic resonance imaging and 31P Magnetic Resonance Spectroscopy (MRS). Diastolic function was assessed using volume time curve analysis, before and after weight loss (1 year). In addition to this, normal weight (n=7–11) and obese subjects (n=13–20) underwent assessment of diastolic function and cardiac energetics (31P-MRS to evaluate PCr/ATP ratio at rest and during stress) during dobutamine infusion (average 62% heart rate increase), and again (at rest) after weight loss intervention.
Results: At rest, obesity was associated with both diastolic dysfunction with a reduced peak filling rate (3.6±0.8ml/s vs 4.6±1.0 p<0.05) and with a 24% lower PCr/ATP ratio (1.67±0.48 vs 2.20±0.45, p=0.02). Catecholamine stress resulted in a further 10% reduction in PCr/ATP ratio in the obese group (1.77±0.47 vs 1.59±0.50, p=0.05), which was not significant in the normal weight group (2.05±0.37 vs 1.92±0.43, p=0.13). Similar levels of inotropic stress resulted in smaller increases in diastolic peak filling rate in obese subjects (37% vs 66%, p=0.05). After weight loss (21±9kg) there was a significant improvement in diastolic filling rate (3.6±0.8ml/s vs 4.3±0.8 p<0.05). This was accompanied by an 18% improvement in PCr/ATP ratio (1.68±0.48 vs 1.96±0.47, p=0.04).
Conclusions. Obesity is associated with diastolic dysfunction and reduced myocardial energetics. Catecholamine stress resulted in further reductions in PCr/ATP ratio and exacerbated diastolic dysfunction. Weight loss partially reversed both the diastolic and energetic derangements seen in obesity.