The echocardiographic manifestations of an urban, working class community with a high cardiovascular risk profile.

Abstract

The metabolic syndrome (MS), consequent upon the pandemic of obesity and diabetes, is associated with an increased risk for cardiovascular (CV) disease. Development of sub-clinical cardiac structural and functional changes associated with CV disease risk factors may be detected on echocardiography. The extent to which these structural changes and CV risk factors are dependent on genetic factors is not clearly established. This project was designed to investigate the relationship between CV disease risk factors, cardiac structural and functional changes and underlying genetic abnormalities. Specifically, the risk factor profile and the presence of the MS were determined. This was then correlated with the echocardiographic findings and gene polymorphisms. Method: A randomly selected cohort of 1428 subjects from the Phoenix community was studied. Demographic data was collected using the WHO STEPS instrument. Blood samples for biochemistry and genetic analysis, together with anthropometric measurements, were collected. Blood pressure and echocardiography was performed on all subjects. The metabolic syndrome was classified according to the National Cholesterol Education Panel (NECP) Adult Treatment Panel III (ATP III) and International Diabetes Federation (IDF) criteria. The Lipoprotein Lipase and Human Paraoxonase-1 genes were genotyped on a Light Cycler 480 Real-Time PCR instrument, using allele-specific probes and sequencing. Results: There was a high prevalence of CV risk factors in this sample; particularly increased waist circumference (79%), obesity (64%) insulin resistance (58%) and hypertension (50%) across the age groups. This translated into a high prevalence of MS (38% using NCEP ATPIII and 46% using IDF criteria). There were significant echocardiographic differences between subjects with and without MS for chamber dimensions (p<0.001), left ventricular wall thickness (p<0.001) and mass (p<0.001), diastolic indices (E-wave {p<0.001}, trans-mitral ratio {p=0.017}) and sub-epicardial adipose tissue (SEAT) thickness (p<0.001). Stepwise multivariate analysis identified age (95% CI 0.975; 0.998), gender (95%CI 0.48; 0.9) and hypertension (95% CI 0.53; 0.99) as independent risk factors for diastolic abnormalities. Logistic regression identified age as the most significant contributor to diastolic abnormalities (OR=1.02; 95%CI 1.009; 1.03; Wald=13.4), followed by the waist circumference (OR=1.025; 95%CI 1.014; 1.037) and BMI (OR=1.075; 95% CI 1.035; 1.117). Genetic analysis showed significant associations between the heterozygous variant of Q192R genotype (PON-1 gene) and elevated HDL levels and also between this variant and obese women (p= <0.05). Conclusion: The high prevalence of CV risk factors and MS in this community has reached epidemic proportions. Although the MS was associated with significant remodelling of cardiac structure, alteration of diastolic indices and increased sub-epicardial adipose tissue thickness, BMI and waist circumference were stronger promoters of altered cardiac physiology. This augurs poorly for this population group unless intervention is introduced to address the markedly high prevalence of these culprit drivers.