CVD, AMI, and CABG in South Asians
January 16, 2007 (Chicago, IL) - A new analysis of the INTERHEART study suggests that the earlier age of AMI in South Asians is explained by the fact that people of South Asian origins tend to develop higher risk-factor levels earlier in life and not that they have some special susceptibility to AMI [1]. In a separate study, a team of Canadian surgeons reports that South Asians face higher morbidity and mortality from CABG surgery [2].
In the first study, Dr Prashant Joshi (Government Medical College, Nagpur, India) and colleagues report that the major modifiable AMI risk factors known to determine CVD risk globally have the same collective impact in South Asians, but at an earlier age. Their study appears in the January 17, 2007 issue of the Journal of the American Medical Association.
"Prior to our paper, the general belief was that some unexplained or novel risk factor needed to be the key to understanding why South Asians get heart disease six years earlier than other ethnic groups," senior author Dr Salim Yusuf (McMaster University, Hamilton, ON) told heartwire. "But nobody had done a large study to find out whether they had higher risk factors at a younger age. Our study indicates that there is no need to invoke new risk factors."
Previous studies have shown that deaths related to CVD occur five to 10 years earlier in the South Asian countries of India, Pakistan, Nepal, Sri Lanka, and Bangladesh than in Western countries. South Asian immigrants in Western countries also appear to have higher CVD death rates at younger ages than does the local population.
Age of first AMI lower in South Asians
To better understand the phenomenon, Joshi et al conducted a case-controlled analysis of first AMIs among 1732 AMI patients and 2204 controls from South Asian countries and 10 728 patients and 12 431 controls from elsewhere in the world.
They found that age of first AMI was lower in South Asians than in participants from other countries (53 vs 58.8 years). CVD protective factors, such as regular physical exercise and fruit and vegetable consumption, were lower among South Asians, whereas risk factors were more common: elevated apolipoprotein B100/apolipoprotein A-1 ratio, diabetes, and higher waist-to-hip ratio. Regular alcohol consumption was protective in non-South Asians, but not in South Asians, possibly because of different drinking patterns in the two populations.
Cultural differences likely pose barriers to lower CVD risk in a number of areas, the authors note. Traditional cuisine might not include a lot of fruits and vegetables in some regions, whereas cooking practices can lead to reduced nutrient levels in vegetables cooked, they note. Leisure physical activity is also less common in many South Asian countries and is "culturally unacceptable for most Muslim women," Joshi et al write. Increased urbanization in many South Asian countries might also play a role, leading to higher obesity rates, which potentially interact with a genetic predisposition that leads to abdominal obesity, dysglycemia, and dyslipidemia. Yusuf pointed out to heartwire that no previous study has examined apolipoproteins in South Asians and that these are twice as predictive of MI as lipoproteins. "Apolipoproteins, diabetes, and central obesity are mediated both by lifestyles and genes, so we need to understand what causes elevation of these risk factors," he commented.
Younger age of first AMI among the South Asian cases is largely explained by the higher prevalence of risk factors in native South Asians, Joshi et al conclude. "These data suggest that lifestyle changes implemented early in life have the potential to substantially reduce the risk of AMI in South Asians."
To heartwire, Yusuf also emphasized that their study is one of very few to compare, in detail, the lifestyles of South Asians with those of other ethnic groups living in different countries. "Given that the largest burden of MI in the world is in South Asia, these findings have important implications for preventing the looming epidemic in these countries," Yusuf explained.
South Asians face higher risks with CABG surgery
Also intrigued by the unique nature of cardiovascular risk in South Asians, a team of Canadian surgeons has examined the increased morbidity/mortality of South Asians undergoing CABG surgery. "It's certainly been thought, just by word of mouth, that South Asians have a higher risk of morbidity at operation, and we wanted to determine whether that was true or not," lead author Dr Stephanie Brister (Toronto General Hospital, ON) told heartwire.
Their findings are reported in the January 2007 issue of the Journal of Thoracic and Cardiovascular Surgery.
Brister et al reviewed prospectively collected data from 1163 South Asian and 5028 white patients who had undergone CABG at Toronto General Hospital between January 1994 and June 2003. Compared with white patients, South Asian patients were younger and less likely to have a family history of coronary heart disease but more likely to have triple vessel disease or prior CABG surgery. When preoperative characteristics of South Asian and white patients were matched by propensity score, researchers found significant outcome differences between the two groups. Perioperatively, South Asians were ventilated longer and remained longer in the ICU and hospital. Postoperatively, South Asians more commonly had sternal-wound infections, low-output syndrome, and MI. Overall, South Asian ethnicity was an independent predictor of perioperative mortality in this study.
Recording ethnicity in medical records
"The increasing evidence that ethnicity (ie, genetic make-up) also might influence atherosclerosis and CHD in general suggests that ethnicity itself should be factored in when assessing potential risks associated with assorted medical and surgical intervention procedures," the authors write. They add that, until recently, recording race or ethnicity in patients' medical files had been "frowned upon" within the Canadian medical community. To heartwire, however, Brister said that although the ethics committee at her institution had previously "been reluctant to allow us to do that," recording a patient's race has increasingly become more acceptable. "There's a rationale for doing it, and it's more widely accepted because it has an impact on research that we're doing and on how we address issues with patients," she said.
Brister also pointed out that although South Asians have the same kinds of risk factors that whites have, "there may be a differential impact on morbidity and mortality of those risk factors that would tailor what we're doing both preoperatively and postoperatively." Interestingly, in a finding that corroborates that of Joshi et al, Brister and colleagues found that the South Asians undergoing CABG in their study were significantly younger than the white patients.
A key message, Brister stressed, is that South Asians are still candidates for CABG. "South Asians can undergo CABG with excellent results. People should not be concerned that [South Asians] are a very high-risk population to operate on and deny them an operation that is in fact beneficial to them. This is a good operation; they have good results."
That said, Brister also emphasized that their study underscores the need to aggressively improve risk-factor profile, where possible, before CABG. "Particularly for things like diabetes, we now know that very tight control of glucose in and around the time of operation influences the incidence of sternal-wound infections and ultimate mortality. So knowing that South Asians have a higher incidence of diabetes, a greater risk of problems associated with metabolic syndrome, then you focus on that and make sure you have meticulous postoperative care," she said.
The complete contents of Heartwire, a professional news service of WebMD, can be found at www.theheart.org, a Web site for cardiovascular healthcare professionals.
January 16, 2007 (Chicago, IL) - A new analysis of the INTERHEART study suggests that the earlier age of AMI in South Asians is explained by the fact that people of South Asian origins tend to develop higher risk-factor levels earlier in life and not that they have some special susceptibility to AMI [1]. In a separate study, a team of Canadian surgeons reports that South Asians face higher morbidity and mortality from CABG surgery [2].
In the first study, Dr Prashant Joshi (Government Medical College, Nagpur, India) and colleagues report that the major modifiable AMI risk factors known to determine CVD risk globally have the same collective impact in South Asians, but at an earlier age. Their study appears in the January 17, 2007 issue of the Journal of the American Medical Association.
"Prior to our paper, the general belief was that some unexplained or novel risk factor needed to be the key to understanding why South Asians get heart disease six years earlier than other ethnic groups," senior author Dr Salim Yusuf (McMaster University, Hamilton, ON) told heartwire. "But nobody had done a large study to find out whether they had higher risk factors at a younger age. Our study indicates that there is no need to invoke new risk factors."
Previous studies have shown that deaths related to CVD occur five to 10 years earlier in the South Asian countries of India, Pakistan, Nepal, Sri Lanka, and Bangladesh than in Western countries. South Asian immigrants in Western countries also appear to have higher CVD death rates at younger ages than does the local population.
Age of first AMI lower in South Asians
To better understand the phenomenon, Joshi et al conducted a case-controlled analysis of first AMIs among 1732 AMI patients and 2204 controls from South Asian countries and 10 728 patients and 12 431 controls from elsewhere in the world.
They found that age of first AMI was lower in South Asians than in participants from other countries (53 vs 58.8 years). CVD protective factors, such as regular physical exercise and fruit and vegetable consumption, were lower among South Asians, whereas risk factors were more common: elevated apolipoprotein B100/apolipoprotein A-1 ratio, diabetes, and higher waist-to-hip ratio. Regular alcohol consumption was protective in non-South Asians, but not in South Asians, possibly because of different drinking patterns in the two populations.
Cultural differences likely pose barriers to lower CVD risk in a number of areas, the authors note. Traditional cuisine might not include a lot of fruits and vegetables in some regions, whereas cooking practices can lead to reduced nutrient levels in vegetables cooked, they note. Leisure physical activity is also less common in many South Asian countries and is "culturally unacceptable for most Muslim women," Joshi et al write. Increased urbanization in many South Asian countries might also play a role, leading to higher obesity rates, which potentially interact with a genetic predisposition that leads to abdominal obesity, dysglycemia, and dyslipidemia. Yusuf pointed out to heartwire that no previous study has examined apolipoproteins in South Asians and that these are twice as predictive of MI as lipoproteins. "Apolipoproteins, diabetes, and central obesity are mediated both by lifestyles and genes, so we need to understand what causes elevation of these risk factors," he commented.
Younger age of first AMI among the South Asian cases is largely explained by the higher prevalence of risk factors in native South Asians, Joshi et al conclude. "These data suggest that lifestyle changes implemented early in life have the potential to substantially reduce the risk of AMI in South Asians."
To heartwire, Yusuf also emphasized that their study is one of very few to compare, in detail, the lifestyles of South Asians with those of other ethnic groups living in different countries. "Given that the largest burden of MI in the world is in South Asia, these findings have important implications for preventing the looming epidemic in these countries," Yusuf explained.
South Asians face higher risks with CABG surgery
Also intrigued by the unique nature of cardiovascular risk in South Asians, a team of Canadian surgeons has examined the increased morbidity/mortality of South Asians undergoing CABG surgery. "It's certainly been thought, just by word of mouth, that South Asians have a higher risk of morbidity at operation, and we wanted to determine whether that was true or not," lead author Dr Stephanie Brister (Toronto General Hospital, ON) told heartwire.
Their findings are reported in the January 2007 issue of the Journal of Thoracic and Cardiovascular Surgery.
Brister et al reviewed prospectively collected data from 1163 South Asian and 5028 white patients who had undergone CABG at Toronto General Hospital between January 1994 and June 2003. Compared with white patients, South Asian patients were younger and less likely to have a family history of coronary heart disease but more likely to have triple vessel disease or prior CABG surgery. When preoperative characteristics of South Asian and white patients were matched by propensity score, researchers found significant outcome differences between the two groups. Perioperatively, South Asians were ventilated longer and remained longer in the ICU and hospital. Postoperatively, South Asians more commonly had sternal-wound infections, low-output syndrome, and MI. Overall, South Asian ethnicity was an independent predictor of perioperative mortality in this study.
Recording ethnicity in medical records
"The increasing evidence that ethnicity (ie, genetic make-up) also might influence atherosclerosis and CHD in general suggests that ethnicity itself should be factored in when assessing potential risks associated with assorted medical and surgical intervention procedures," the authors write. They add that, until recently, recording race or ethnicity in patients' medical files had been "frowned upon" within the Canadian medical community. To heartwire, however, Brister said that although the ethics committee at her institution had previously "been reluctant to allow us to do that," recording a patient's race has increasingly become more acceptable. "There's a rationale for doing it, and it's more widely accepted because it has an impact on research that we're doing and on how we address issues with patients," she said.
Brister also pointed out that although South Asians have the same kinds of risk factors that whites have, "there may be a differential impact on morbidity and mortality of those risk factors that would tailor what we're doing both preoperatively and postoperatively." Interestingly, in a finding that corroborates that of Joshi et al, Brister and colleagues found that the South Asians undergoing CABG in their study were significantly younger than the white patients.
A key message, Brister stressed, is that South Asians are still candidates for CABG. "South Asians can undergo CABG with excellent results. People should not be concerned that [South Asians] are a very high-risk population to operate on and deny them an operation that is in fact beneficial to them. This is a good operation; they have good results."
That said, Brister also emphasized that their study underscores the need to aggressively improve risk-factor profile, where possible, before CABG. "Particularly for things like diabetes, we now know that very tight control of glucose in and around the time of operation influences the incidence of sternal-wound infections and ultimate mortality. So knowing that South Asians have a higher incidence of diabetes, a greater risk of problems associated with metabolic syndrome, then you focus on that and make sure you have meticulous postoperative care," she said.
Joshi P, Islam S, Pais P, et al. Risk factors for early myocardial infarction in South Asians compared with individuals in other countries. JAMA 2007; 297: 286-294.
2. Brister SJ, Hamdulay Z, Verma S et al. Ethnic diversity: South Asian ethnicity is associated with increased coronary artery bypass grafting mortality. J Thorac Cardiovasc Surg 2007; 133:150-154.
The complete contents of Heartwire, a professional news service of WebMD, can be found at www.theheart.org, a Web site for cardiovascular healthcare professionals.
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