Higher Cardiovascular Risks for South Asians With Coronary Heart Disease

November 02, 2010

November 2, 2010 (Montreal, Quebec City) — Prospective registry data from a single center provide some support that individuals of South Asian descent are at greater risk of cardiovascular events than individuals of European ancestry.

In the analysis, South Asian men and women with established coronary heart disease had numerically higher rates of cardiovascular death, nonfatal MI, and nonfatal stroke at five years than white individuals, although the difference in event rates did not reach statistical significance when adjusted for potential confounders. Investigators say the lack of statistical significance is likely due to small numbers and that the trend observed is supported by evidence from retrospective analyses and case-control studies.

"There is a evidence suggesting that South Asians are at a higher risk of developing coronary disease at a younger age and a fair amount of evidence to suggest that once they have coronary disease their outcomes are worse than white populations," lead investigator Dr Milan Gupta (McMaster University, Hamilton, ON) told heartwire .

Presenting the results of their work last week at the Canadian Cardiovascular Congress 2010, Gupta said the PRACTICE registry, from which the data are derived, was started as a way to prospectively assess whether or not South Asians with coronary artery disease fared worse than whites when treated with evidence-based therapies. In total, 514 consecutive patients were included in the registry, of whom 199 were South Asian and 315 were of European ancestry. Clinical management of their disease was left to the discretion of the cardiologist.

Overall, South Asians were more likely than white individuals to have diabetes mellitus and less likely to smoke. Rates of hypertension and dyslipidemia were similar between the populations, as were baseline blood pressure and waist circumference. Use of evidence-based medicine, including statins and antiplatelet therapies, were similar in both populations.

After a mean follow-up of five years, 25.1% of South Asians died of cardiovascular causes, had a nonfatal MI or nonfatal stroke, or underwent revascularization with PCI or CABG surgery, the study's primary end point, compared with 19.7% of individuals of European ancestry (p=0.15). The secondary end point, a composite of cardiovascular death, MI, or stroke, occurred in 15.6% of South Asians and 11.1% of the white individuals (p=0.14). The individual components of the primary end point trended higher in South Asians, but none achieved statistical significance.

"It's hard to know, but the message we're taking away from this is that event rates are probably higher in South Asians--one of our conclusions is that our study is small and exploratory--and this needs to be confirmed in larger, prospective studies," said Gupta.

Gupta and colleagues observed a significantly higher rate of cardiovascular death, MI, or stroke among South Asian women compared with white women. These results, Gupta told heartwire , are in line with an earlier analysis of South Asians undergoing coronary angiography, a study that showed a twofold higher rate of left main and triple-vessel disease in South Asians compared with white patients, a difference that was more pronounced in women.

Impaired Fibrinolysis in South Asians

In a second analysis of the PRACTICE registry, Dr Narendra Singh (Emory University, Atlanta, GA) measured plasma plasminogen activator inhibitor 1 (PAI-1), a marker of impaired fibrinolysis, and high-sensitivity C-reactive protein (CRP), a marker of inflammation, in 146 white individuals and 111 South Asians.

"We're now looking for some explanation as to why there is a difference between the South Asian population and the European patient population," Singh told heartwire . "PAI-1 is involved in the modulation of fibrinolysis, so it helps in terms of keeping the vessels patent, and it's one the factors that could explain the differences we're seeing between the two populations."

In the subset of PRACTICE patients, there was no observed difference in CRP levels, which might be a function of the fact that these patients are well treated with medical therapy, said Singh. When researchers examined the marker of fibrinolysis, on the other hand, PAI-1 levels were significantly higher among South Asian coronary heart disease patients. When investigators adjusted for the metabolic syndrome, which is more prevalent in the South Asian population in PRACTICE, the difference in PAI-1 levels between the two populations was attenuated.

"What this suggests is that either PAI-1 is contributing to the metabolic syndrome, which in turn is leading to the development of diabetes and the progression of heart disease in the South Asian population," said Singh, or metabolic syndrome leads to high PAI-1 levels, "and that might be the reason you see the progression of coronary disease. This is something that still needs to be worked out."


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