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ORIGINAL ARTICLE
Year : 2006  |  Volume : 7  |  Issue : 4  |  Page : 126-131 Table of Contents     

Racial variation in clinical characteristic and outcome in patients presenting with acute myocardial infarction: comparison between Qatari and South Asian patients in Qatar


1 Department of Cardiology and Cardiovascular Surgery, Hamad General Hospital - Hamad Medical Corporation, Doha, Qatar
2 Department of Biostatistics and Epidemiology, Hamad General Hospital - Hamad Medical Corporation, Doha, Qatar

Date of Web Publication17-Jun-2010

Correspondence Address:
J Al Suwaidi
Department of Cardiology and Cardiovascular Surgery, Hamad Medical Corporation, P.O.Box 3050, Doha
Qatar
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Source of Support: None, Conflict of Interest: None


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   Abstract 

Background: South Asians (SA) from the Indian Subcontinent are known to have coronary artery disease (CAD) at a very young age and also to have a more diffuse disease when compared to indigenous patients in the Western world.
Objective : The aim of the study was to compare clinical characteristics and outcome of South Asian patients to Qatari patients presenting with acute myocardial infarction (AMI) in Qatar. The majority of SA residing in Qatar are manual workers of lower socioeconomic status when compared to the Qatari population.
Methods: We conducted a retrospective analysis of a prospectively collected data of all patients diagnosed with acute myocardial infarction (AMI) in the State of Qatar during ten years (1991 -2001). Patients were divided into two groups: Qataris (1598 patients) and South Asians (2606 patients). Diagnostic classification of definite AMI was made in accordance with criteria based on the International Classification of Disease ninth revision [ICD-9]. The obtained information was based on the following parameters: age at the time of admission, gender, cardiovascular risk factor profiles (smoking, hypercholesterolemia, diabetes, and pre-existing coronary heart disease), and ECG. Data analyses were performed using univariate and stepwise logistic regression analysis.
Results: When compared to Qatari patients, SA patients were younger (47 yrs vs 61 yrs; p < 0.0001). SA were more likely to be smokers (50.5% vs 23.4%; p < 0.0001) and male (96.9 % vs 71.8% p < 0.0001). SA were less likely to have: diabetes mellitus (24.8% vs 54.0%; p < 0.0001); hypertension (19.9% vs 37.6%; p < 0.0001); previous MI (8.1% vs 15.8%; p < 0.0001); CABG (2.2% vs 3.9%; p = 0.002). The number of patients who received thrombolytic therapy was significantly higher among SA when compared to Qatari (54.6% vs 25.9%; p < 0.0001), and this was significantly associated with lower in-hospital mortality rate (6.7% vs 16.8%; p < 0.0001).
Conclusion: SA patients who had AMI in Qatar had better outcome than Qataris. This may be explained by the patients' favorable baseline clinical characteristics such as younger age and less prevalence of diabetes and hypertension.

Keywords: myocardial infarction, coronary heart disease, ischemic heart disease, South


How to cite this article:
Hanifah M, Hadi H, Bener A, AlBinali HH, Al Suwaidi J. Racial variation in clinical characteristic and outcome in patients presenting with acute myocardial infarction: comparison between Qatari and South Asian patients in Qatar. Heart Views 2006;7:126-31

How to cite this URL:
Hanifah M, Hadi H, Bener A, AlBinali HH, Al Suwaidi J. Racial variation in clinical characteristic and outcome in patients presenting with acute myocardial infarction: comparison between Qatari and South Asian patients in Qatar. Heart Views [serial online] 2006 [cited 2021 May 11];7:126-31. Available from: https://www.heartviews.org/text.asp?2006/7/4/126/63892


   Introduction Top


Coronary artery disease (CAD) in South Asians i.e., those from the Indian subcontinent, has recently attracted great interest worldwide. During the past three decades, although the rates of CAD considerably decreased in the USA, Australia, Canada, France, Japan and Finland, it doubled in India during the same period [1],[2] . The risk of CAD in South Asians is 3-4 times higher than White Americans, 6 times higher than the Chinese and 20 times higher than the Japanese. Moreover, they tend to get the disease at a much younger age, more severe and diffuse. They have higher morbidity and mortality than the other ethnic groups. For instance in Great Britain, the first AMI among South Asians of age less than 40 years is reportedly 10 times higher than the local Whites. In Singapore, mortality from CAD below 30 years of age is 10 times more in South Asians than the local Chinese population of the same age group. This trend is reflected elsewhere, wherever there is a substantial South Asian population.

In addition to the traditional risk factors like diabetes mellitus, hypertension, hyperlipidemia and smoking, there appears to be a strong role of insulin resistance, central obesity, and elevation in Lipoprotein (a) in the pathogenesis of CAD among SA [3],[4],[5],[6],[7] . Qatar has a large population of South Asians and therefore, we compared the clinical characteristics and outcome of South Asian patients to Qatari patients presenting with acute myocardial Infarction (AMI) in Qatar.


   Materials and Methods Top


Study Setting

Qatar is a small country with a population of around 600,000 (2001 census) consisting of Qataris (less than 30%) and non-Qataris (more than 70%). 30% of non-Qataris are from South Asia, mainly India, Pakistan, and Bangladesh. Unlike other Western countries, the South Asian population in Qatar, like the rest of the Arabian Gulf, comprises mainly males. As a group, they generally belong to the lower socio-economic strata. Another objective of the study was to try to find out whether there are any newer contributing factors in SA in addition to the traditional risk factors for CAD.

At the time of the study, health care in Qatar was free for everyone, citizens or expatriates. This study was based at Hamad General Hospital, Doha. This hospital provides in-patient and outpatient medical and surgical care for all residents of Qatar; citizens and expatriates. It is the only tertiary-care center in the country, thus making it an ideal center for population-based studies. In Qatar thrombolysis constitutes the corner stone of treatment for acute STEMI. Primary angioplasty was not routinely available during the study period but rescue angioplasty was available for patients who failed to respond to thrombolytic therapy [8],[9],[10] .

Definition and treatment

The diagnosis of acute myocardial infarction was made according to the revised World Health Organization definition based upon symptoms, ECG, and cardiac enzymes abnormalities. Acute myocardial infarction was made if the patient presented with typical ischemic chest pain of myocardial injury.

Thrombolytic reperfusion therapy with either Streptokinase or Alteplase was instituted in patients with ST segment elevation-MI whose onset of chest pain was less than 12 hours prior to admission to our Coronary Care Unit. Exclusion from thrombolytic therapy were the following: late presentation, recent gastro-intestinal bleeding, recent cerebrovascular accident, severe or malignant hypertension, and estimated door to needle time is 35 minutes [9],[10],[11] .

Database

The database of the Coronary Care Unit (C.C.U.) of Hamad Medical Corpopration (HMC) was used for this study. The unit prospectively collected data for all patients admitted to the cardiology department at HMC. The Review board of HMC approved the study prior to the data analysis. Physicians collected data from the clinical records at the time of the patients' hospital discharge. Data was collected according to predefined criteria for each data point. These records were coded and registered at the Cardiology Department from January 1991 to December 2001 [8],[9],[10] .

Statistical Methods

The data was coded and entered into a computer using the Statistical packages for Social Sciences (SPSC) Nousis [12] . Data is expressed as mean standard deviation (SD) unless otherwise stated. Student-t-test was used to ascertain the significance of differences between mean values of two continuous variables and Mann-Whitney test was used for non-parametric distribution. Chi-Square analysis was performed to test for differences in proportions of categorical variables between two or more groups. Logistic regression results were reported as odds ratios and 95% confidence intervals along with p-values (derived from likelihood ratios statistics which have a Chi-Square distribution). The level p < 0.05 was considered the cut-off value for significance.


   Results Top


Between Jan 1991 and Dec 2001, the total number of AMI patients admitted to the CCU was 5390, of which 1598 were Qataris and 2606 were South Asians.

Baseline clinical characteristics [Table 1]

South Asian patients were younger. The mean age for Qataris was 61 years and that of the South Asians 47 years (p < 0.0001). SA were more likely to be smokers (50.5% vs 23.4%; p < 0.0001) and predominantly male (96.9% vs 71.8%; p < 0.0001).

South Asians were less likely to have diabetes mellitus (24.8% vs 54.0%; p < 0.0001) and hypertension (19.9% vs 37.6%; p < 0.0001). SA were also less likely to have previous MI (8.1% vs 15.8%; p < 0.0001) and previous CABG (2.2% vs 3.9%; p = 0.002). The prevalence of hyperlipidemia was almost equal between the two groups, 26.4% for Qataris and 24.7% for South Asians. Genetics appear to play a significant role in both groups, 72% having a family history of CAD. The number of post-menopausal women with AMI was very low in the South Asian group (2.2%) as compared to the Qatar's (25.6%), reflecting the fact that the South Asian population mainly constitutes bachelors or those living without their spouses.

Mode of therapy [Table 2]

South Asians were more likely to be treated with aspirin and thrombolytic therapy than Qataris. There were no differences in the use of angiotensin-converting enzyme inhibitors, beta-blockers, lipid-lowering agents or calcium-channel blockers.

Mortality and Morbidity rates

The number of patients who received thrombolytic therapy was significantly higher among SA when compared to Qataris (54.6% vs 25.9%; p < 0.0001) and this was associated with significantly lower in-hospital mortality rate(6.7% vs 16.8%; p < 0.0001) . This significant reduction in mortality remained significant even after adjustment for age and gender (p < 0.001).

Multiple logistic regression analysis [Table 3] showed that arrhythmias, heart block, diabetes mellitus, cardiogenic shock and stroke are considered as predictors for mortality among STEMI patient treated with thrombolytic therapy.


   Discussion Top


In our study, South Asians develop coronary artery disease at a much younger age, presenting with symptoms 5-10 years earlier than Qataris [Table 4]. This finding is similar to other studies [13],[14],[15],[16],[17],[18],[19] in this group.

South Asians in Qatar are mainly of the younger age group and the incidence of CAD in this group is higher than the Qataris. South Asians come to earn a living to support their families back home. World trend in smoking appears to be on the decline and this is also evident among educated Qataris. In our study, South Asians tended to be smokers and the prevalence appears to be increasing. They are probably are influenced by their peer groups, as they live in groups in Labor Camps. They are most likely lonely since they are far from their families, and hence, they find solace in smoking.

Both groups had a high incidence of family history for CAD and there was no statistically significant difference in the incidence of hyperlipidemia. However, the prevalence of diabetes and hypertension among South Asians was much lower as compared to Qataris.

In contrast to previous studies [20],[21],[22] , socioeconomic class was not a factor in type of therapy administration or outcome in our study. The majority of South Asians in Qatar are manual laborers but they received thrombolytic therapy in the South Asians more than in the Qatari group. This is because the Qataris were much older and presented with a significantly higher rate of non-ST-segment elevation MI, which did not warrant thrombolysis. In addition, the Qataris had more co-morbidities such as renal failure, strokes, etc.

Macenach et al [20] reported a higher cardiovascular mortality in patients belonging to a lower socioeconomic group in the United States of America and 11 western European countries, while Kunst et al [21] reported the variable nature of socioeconomic inequalities in ischemic heart disease mortality in different European countries. In England, Ireland and Nordic countries, patients belonging to manual classes had a higher mortality rates compared to non-manual classes. In France, Switzerland and Mediterranean countries, the manual class had mortality rates as low as, or lower than, those among nonmanual classes. These differences in conclusion may in fact be related to different patient populations studied.

In addition to the traditional risk factors like smoking, diabetes, hypertension and hyperlipidemias, South Asians had higher lipoprotein-a (Lp-a), which is a genetic risk factor and which is not modified by diet, exercise, lifestyle modification or even drugs. Lp-a is 10 times more atherogenic than LDL. Lipoprotein-a also appears to be a risk factor for the rapid progression of CAD, which is thought to be due to an interference with thrombolysis through the partial structural homology of Lp (a) with plasminogen [16],[17] . Unfortunately, we were not able to assess the Lp-a level in our study group due to the non-availability of the test in our hospital during the study period. Although some studies have demonstrated that in South Asians the extent of atheroma correlated with total cholesterol concentration and the relative risk of infarction increased with rate of total to HDL cholesterol, we were not able to establish this. It's probable that at a given level of cholesterol, different ethnic groups may be at differing levels of cardiac risk [18] . Homocysteine has been implicated in some studies for the high rate of CAD among South Asians but this has been contested by some other studies done in India [23],[24] .

The South Asian patients had higher triglyceride levels than the Qataris. Other newer risk factors like insulin resistance syndrome, serum fibrinogen and infections were not studied. The incidence of diabetes and hypertension was not as high as expected, and was only half of that of the Qataris.


   Limitations of the Study Top


The major limitation of our study is its retrospective analysis of a prospective registry. Other study limitations could include: possible bias due to exclusion of cases; missing data or measurement error; possible confounding by variables not controlled as this was an observational study. For example, the time interval between symptom onset and arrival to the emergency department is not known. Furthermore reasons for not administering thrombolytic therapy was also not known, nevertheless to-date it is the largest study reported from the Arab world. Finally, our data is limited to 7-day mortality and data of long-term mortality rate is unavailable.


   Conclusion Top


Acute myocardial infarction occurs in South Asians at a much younger age; they are 5-10 years younger than the Qataris and prevalence rate is two times more than Qataris. The disease is more severe and diffuse. Despite the lower prevalence of the conventional risk factors like diabetes and hypertension, the excessive prevalence of smoking combined with possible genetic predisposition most likely play major roles.

SA patients who had AMI in Qatar had a better outcome than the Qataris. This is probably due to the fact that the SA were predominantly younger, males, and had less risk factors other than smoking. In addition, a higher number of them received thrombolytic therapy when compared with the indigenous Qatari population. Our study suggests that in Qatar where health care is practically free, lower socioeconomic status does not affect cardiovascular mortality.

 
   References Top

1.Enas EA, Mehta J. Malignant coronary artery disease in young Asian Indians: thoughts on pathogenesis, prevention, and therapy. Coronary Artery Disease in Asian Indians (CADI) Study. Clin Cardiol 1995 Mar; 18(3): 131-5.  Back to cited text no. 1      
2.Ascherio A, Cho E, Walsh K, Sacks FM, Willett WC, Faruqui A. Premature coronary deaths in Asians. BMJ 1996 312:508.   Back to cited text no. 2      
3.Terres WT E,Pfalzer B,Beil FU,Beisiegel U, Hamm CW. Rapid angiographic progression of CAD patients with elevated Lp(a). Circulation 1995 Feb 15; 91(4): 948-50.  Back to cited text no. 3      
4.Stoney CM, Hughes JW, Kuntz KK, West SG, Thornton LM. Cardiovascular stress responses among Asian Indian and European American women and men. Ann Behav Med 2002; 24:113-21.  Back to cited text no. 4      
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6.Mohan V, Deepa R, Haranath SP, Premalatha G, Rema M. Lipoprotein(a) is an independent risk factor for coronary artery disease in NIDDM patients in South India. Diabetes Care 1998; 21: 1819-23.  Back to cited text no. 6      
7.Singh RB, Niaz MA, Ghosh S, et al. Low fat intake and CAD in a population with higher prevalence of CAD;the Indian paradox. J Am Coll Nutr 1998; 17:342-50.  Back to cited text no. 7      
8.Hadi AR, Al Suwaidi J, Bener A, Khinji A Al Binali HA. Thrombolytic therapy use for acute myocardial infarction and outcome in Qatar. Int J Cardiol 2005; 102: 249-54.  Back to cited text no. 8      
9.Al Suwaidi J, Bener A, Behair S, Al Binali HA. Mortality due to acute myocardial infarction in Qatari Women. Heart 2004; 90: 693-4.  Back to cited text no. 9      
10.Al Suwaidi J, Wright RS, Grill JP, et al. Obesity is associated with premature occurrence of acute myocardial infarction. Clin Cardiol 2001; 24:542-547.  Back to cited text no. 10      
11.Al Suwaidi J, Reddan DN, Williams K, Pet al. Prognostic implications of abnormalities in renal function in patients with acute coronary syndromes. Circulation 2002; 106:974-980.  Back to cited text no. 11      
12. Nousis MJ SPSS Inc. SPSS/PC for windows, windows version 11.0, Chicago, Illinois, 1998.  Back to cited text no. 12      
13.Suresh CG, Zubiad M Thlib L et al. Racial variation in risk factors and occurrence of acute myocardial infarction: comparison between Arab and South Asian men in Kuwait. Indian Heart J. 2002; 54: 266-70.  Back to cited text no. 13      
14.Wilkinson P,Sayer J ,Laji K et al . Comparison of case fatality in south Asian and white patients after acute myocardial infarction: observational study. BMJ. 1996 ; 312: 1330-3.  Back to cited text no. 14      
15.Mukhtar HT, Littler WA. Survival after acute myocardial infarction in Asian and white patients in Birmingham. Br Heart J. 1995 Feb; 73: 122-4.  Back to cited text no. 15      
16.Gupta M, Doobay AV,Singh N AnandSS, Raja F et al. Risk factors, hospital management and outcomes after acute myocardial infarction in South Asian Canadians and matched control subjects. CMAJ. 2002;166: 717-22.  Back to cited text no. 16      
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18.Gupta R, Vasisht S, Bahl VK, et al. Correlation of lipoprotein (a) to angiographically defined coronary artery disease in Indians. Int J Cardiol 1996; 57: 265-70.  Back to cited text no. 18      
19.Thomas CS,Krishnaswami S. Distribution of Body Mass Index in Indian patients with CAD. Indian Heart J 1995; 47:134-7.  Back to cited text no. 19      
20.Mackenbach JP, Kunst AE, Cavelaars AE, Groenhof F, Geurts JJ.Socioeconomic inequalities in morbidity and mortality in western Europe. The EU Working Group on Socioeconomic Inequalities in Health. Lancet. 1997; 349: 1655-9.  Back to cited text no. 20      
21.Mackenbach JP, Cavelaars AE, Kunst AE, Groenhof F. Socioeconomic inequalities in cardiovascular disease mortality; an international study. Eur Heart J. 2000 ; 21: 1141-51.  Back to cited text no. 21      
22.Kunst AE, Groenhof F, Andersen O, et al .Occupational class and ischemic heart disease mortality in the United States and 11 European countries. Am J Public Health. 1999; 89: 47-53.  Back to cited text no. 22      
23.Jha P, Enas E, Yusuf S. Coronary Artery Disease in Asian Indians: Prevalence and Risk Factors. Asian Am Pac Isl J Health 1993;1:163-175.   Back to cited text no. 23      
24.Snehalatha C, Ramachandran A, Satyavani K, et al. Plasma homocysteine concentration and coronary artery disease in Asian Indians. J Assoc Physicians India 2002; 50:1229-31.  Back to cited text no. 24      



 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4]



 

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