Several clinical and epidemiological studies have demonstrated a higher mortality and morbidity from coronary artery disease (CAD) and acute myocardial infarction (AMI) among blacks in United States compared to whites. This disparity is even wider among younger blacks and black women compared to whites. The higher mortality and morbidity among blacks following AMI has been attributed, in part, to lower socioeconomic conditions, limited access to medical care and to a higher prevalence of risk factors for CAD particularly systemic hypertension and diabetes mellitus. Despite these epidemiological findings, a direct biological factor accounting for this increased mortality and morbidity among blacks remains unknown. Several studies have shown a significantly higher incidence of hypertensive left ventricular hypertrophy (LVH) among blacks. LVH has been shown to be a powerful predictor of mortality in patients with CAD. The present proposal focuses on LVH as an important biological factor accounting for the poor prognosis of blacks after AMI. The rational is based upon the association of LVH with multiple pathophysiological maladaptations that are likely to aggrevate the hemodynamic and morphological consequences of AMI. Such maladaptations include abnormalities of the coronary circulation and impaired myocardial energy metabolism. Following AMI, the residual viable myocardium undergoes compensatory hypertrophy in response to a chronic increase in workload on the heart mediated by the loss of functional cardiac units. This hypertrophic response is considered a positive adaptation which permits reduced numbers of functional units to maintain global cardiac performance at near normal levels. In patients with LVH, the myocardium has already adapted to increased workload and may be operating at or near maximum functional capacity. Accordingly, when AMI occurs with pre-existing LVH, the compensatory response of the residual viable myocardium, if any, would be limited and, therefore, inadequate to maintain global cardiac performance. In the present proposal, we will test the hypothesis that under such a circumstance (AMI with pre-existing LVH), which is more prevalent among blacks, the propensity to develop LV dysfunction, dilation and pump failure increases significantly leading to higher mortality and morbidity.
| Obeidat, Omar; Alam, Mohsin; Divine, George W et al. (2004) Echocardiographic predictors of prognosis after first acute myocardial infarction. Am J Cardiol 94:1278-80 |
| Manhapra, A; Khaja, F; Syed, M et al. (2000) Electrocardiographic presentation of blacks with first myocardial infarction does not explain race differences in thrombolysis administration. Am Heart J 140:200-5 |
| Syed, M; Khaja, F; Rybicki, B A et al. (2000) Effect of delay on racial differences in thrombolysis for acute myocardial infarction. Am Heart J 140:643-50 |
| Ali, A S; Rybicki, B A; Alam, M et al. (1999) Clinical predictors of heart failure in patients with first acute myocardial infarction. Am Heart J 138:1133-9 |
