Ethnic variability in mortality from ischaemic heart disease/cardiomegaly in Malaysia

Abstract

The prevalence of ischaemic heart disease with associated cardiomegaly and other chronic diseases such as diabetes mellitus has increased in Malaysia in recent years. As the contribution to mortality from ischaemic heart disease/cardiomegaly in different ethnic populations is unclear, a three year (January 2013–December 2015) retrospective study of autopsy cases was undertaken at the Department of Forensic Pathology, University Malaya Medical Centre. There were 80 cases with lethal ischaemic heart diseases/cardiomegaly. The age range was 30–69 years (mean 50.19 years) with a male to female ratio of 39:01. The most vulnerable age was 50–59 years accounting for 38.75% of cases. Malays accounted for 15% of cases, Indians for 32.5% and Chinese for 36.25%. Although in 35 cases (43.75%) there was a history suggestive of ischaemic heart disease, the remaining 45 cases (56.25%) were apparently healthy until the terminal collapse. It appears that Indian males in the 50–59 year age range are most at risk for lethal cardiac events in this population, most often with no preceding symptoms or signs. The study demonstrates the value of studying subpopulations for disease risk rather than relying on accrued general population data.

Keywords

Ischaemic heart disease ethnic origin body mass index coronary artery disease left ventricular hypertrophy cardiomegaly

Introduction

Ischaemic heart disease (IHD) is a broad term encompassing several closely related syndromes caused by myocardial ischaemia whereby there is an imbalance between cardiac blood supply (perfusion) and myocardial oxygen and nutritional requirements.1 In more than 90% of cases, IHD is a consequence of reduced coronary artery blood flow secondary to obstructive atherosclerotic vascular disease.2,3 Less frequently, IHD can also result from increased demand as a result of increased heart rate or hypertension, increased heart size, diminished blood volume, reduced oxygenation or lowered oxygen-carrying capacity.4,5

Despite reduced mortality from IHD in many countries, including the United States, associated with smoking cessation programmes and the use of cholesterol lowering agents, mortality continues to increase in Malaysia.6,7 To determine whether there was a difference in ethnic predisposition to IHD in this population the following study was undertaken.

Materials and method

A retrospective review of autopsy cases was undertaken at the Department of Forensic Pathology, University Malaya Medical Centre (UMMC), Kuala Lumpur, Malaysia, over a three-year period from January 2013 to December 2015, looking for all cases where death had been attributed to IHD/cardiomegaly. All cases had been the subject of a full coronial investigation with an autopsy examination including histology and toxicology. Case details were summarised including age, sex, body mass index (BMI), cardiac findings and cause of death. Statistical analysis was performed using SPSS version 23.0. The results were later analysed by using chi-square test and Fisher’s exact test. The statistical significance is set at p < 0.05.

Results

There were 1163 autopsy cases, the majority of which involved trauma from motor vehicle crashes or falls (69.94%). In 242 cases death was related to a cardiac cause with 80 cases (33.06%) due to IHD/cardiomegaly. The age range of the deceased in the IHD subgroup was 30–69 years (mean 50.2 years) with a male to female ratio of 39:01. The most vulnerable age was 50–59 years accounting for 38.8% of cases. Malays accounted for 15% of cases, Indians 32.5%, Chinese for 36.25% and non-citizens 16.25% (Table 1).

Table 1.

Demographic data of 80 cases of ischaemic heart disease presenting to the Department of Forensic Pathology, University Malaya Medical Centre (UMMC), Kuala Lumpur, Malaysia, over a three-year period from January 2013 to December 2015.

No. of cases (n = 80)
Age group
30–39	13 (16.3%)
40–49	24 (30%)
50–59	31 (38.8%)
60–69	12 (15%)
Mean age (year)	50.19 (±9.5)
Range	30–69
Sex
Female	2 (2.5%)
Male	78 (97.5%)
Ethnicity
Malay	12 (15%)
Chinese	29 (36.25%)
Indian	26 (32.5%)
Non-citizen	13 (16.25%)

Calculation of the BMI showed that 5 cases (6.25%) were underweight, 27 cases (33.75%) were normal, 32 cases (40%) were overweight, 12 cases (15%) were obese in class 1 category and 4 cases (5%) were in the obese class 2 category WHO classification3 (Table 2). No significant association could be demonstrated between BMI and sex, age, ethnicity, smoking and alcohol use, left ventricular wall thickness or coronary artery disease.

Table 2.

Body mass index (BMI) of 80 cases of ischaemic heart disease presenting to the Department of Forensic Pathology, University Malaya Medical Centre (UMMC), Kuala Lumpur, Malaysia, over a three-year period from January 2013 to December 2015.

No. of cases (n = 80)
BMI (kg/m²)
Mean	25.98 ± 4.94
Range	(16.33–39)
BMI group (WHO classification)
Underweight	5 (7.2%)
Normal	27 (39.1%)
Overweight	22 (27.5%)
Class 1 Obese	12 (15%)
Class 2 Obese	3 (3.8%)

Although in 35 cases (43.75%) there was a history suggestive of IHD, the remaining 45 cases (56.25%) were apparently healthy until the terminal collapse (Figure 1).

Figure 1.

Percentage of cases with no presenting history in 80 cases of IHD presenting to the Department of Forensic Pathology, UMMC, Kuala Lumpur, Malaysia, over a three-year period from January 2013 to December 2015.

In 32 cases (40%) the left ventricular free wall was of normal thickness while 37 cases (46.25%) showed a thickened wall. In 11 (13.75%) cases no data were available. In 28.75% of cases the heart weighed more than 500 g. Significant stenosing coronary artery atherosclerosis was present in a single coronary artery in 32 cases (40%), two coronary arteries in 15 cases (18.75%) and all three major epicardial coronary arteries in 18 cases (22.5%). In 15 cases (18.75%) no coronary artery atherosclerosis was noted.

Discussion

This study demonstrated an increase in deaths from coronary artery disease with age; only 16.25% of deaths were in the 30–39 year group compared to 38.75% in the 50–59 year group. The mean age was 50.19 years old. The lower numbers, 12%, in the 60–69 year group may be a reflection of attrition over the years and also possibly the presence of other significant comorbidities. Our findings were comparable to observations made in Singapore, where the mean age at first infarction was less in Asians (50.2 years) than in Westerners (55.5 years).8,9 The usual male predilection was confirmed with a male to female ratio of 39:01.

The proportion of deaths due to IHD/cardiomegaly among Malays, Indians and Chinese was 15, 32.5 and 36.25%, respectively. According to the 2010 census, the population of Kuala Lumpur was composed of 44.2% Malays, 10.3% of Indians, 43.2% of Chinese and 1.8% others.7 Kuala Lumpur has an estimated population of 1.67 million people in an area of just 94 square kilometres, with a very high population density of 17,310 people per square mile or 6890 per square kilometre.7 Thus, it appears that Indian males are at particular risk for death from IHD in this population.10,11 This has also been reported in Singapore where the prevalence of coronary artery disease was seven times higher in Indians than in Chinese in an autopsy series.8 This ethnic predominance has also been noted in other studies from Uganda, Trinidad, South Africa and the United Kingdom.7,12 However, it is also possible that the low number of Malay cases has been skewed by a religious/cultural resistance to autopsy among Muslims.13

Of note, in more than half of the cases (56.25%) in this study the individuals were apparently healthy prior to their collapse with the diagnosis of cardiac disease only being made at autopsy. This demonstrates that the cohort of individuals presenting to forensic facilities with lethal IHD/cardiomegaly differs from hospital-based cohorts where symptoms and signs of cardiac disease have led to investigations.1,14,15

In conclusion, it appears that Indian males in the 50–59 year age range are most at risk for lethal cardiac events in this population, most often with no preceding symptoms or signs. Despite the known association between BMI and increased morbidity and mortality from cardiovascular disease¹⁷ this association could not be demonstrated.16 –18 The study demonstrates the value of studying subpopulations for disease risk rather than relying on accrued general population data.

Footnotes

Declaration of conflicting interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

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