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Incidence of atherosclerosis in different coronary arteries and its relation with myocardial infarction: a randomized study in 300 autopsy hearts in a tertiary care hospital.

Introduction

Cardiovascular disease is one of the leading cause of death in the south Asian countries especially India. Cardiovascular disease accounts for 24% of death in India out of the total 53% noncommunicable deaths. [1,2] Coronary atherosclerosis is known to be one of the major culprits behind myocardial infarction and subsequent mortality. Detailed demographic study to find the incidence of coronary atherosclerosis in deaths in different sexes and age groups in western India especially Surat has not been carried out. Similar studies in other parts of India have shown that the incidence of coronary artery atherosclerosis increases with age and there is an increased incidence in males. [2-5] The purpose of this study is to find the incidence of coronary atherosclerosis in different age groups and sex in the district of Surat, South Gujarat (India) and determine the correlation between atherosclerosis and myocardial infarction and ischemia.

Materials and Methods

The study was carried out on 371 medico legal cases in autopsy section of pathology department, Government Medical College, Surat. Heart was not received in 18 cases and was completely autolysed in 47 cases. So these 71 cases were excluded from the study. All the hearts received were dissected by short-axis method. [6-8] The heart was cut from the apex horizontally upto 2.5 cm from the atrioventricular junction with every 1 cm interval. The was looked for any pale or white areas. One section each from apex, left ventricular wall, right ventricular wall & interventricular septum was given. After that, the heart was cut in the direction of blood flow i.e. superior & inferior vena cava [??] right atrium [??] right ventricle [??] pulmonary artery & pulmonary vein [??] left atrium [??] left ventricle [??] aorta.

The coronaries were looked and palpated for thickened or calcified areas and one section each from left coronary artery, right coronary artery, left circumflex artery & aorta was given. The section from aorta was from root of aorta. All the sections were then processed routinely in an automatic tissue processor and stained by haematoxylin and eosin stain. Myocardium was looked for presence of ischaemia or infarction. Coronaries & aorta were looked for presence of atherosclerosis. The grading of atherosclerosis has been done according to American Heart Association. Those arteries having more than 60% occlusion of lumen were mentioned in the study.

Results

300 post-mortem hearts were studied for CHD. Heart was examined grossly as well microscopically for chronic ischemic changes, healed infarct & acute myocardial infarction. Coronaries and aorta were examined for presence of atherosclerosis and then graded for morphological type according to the American Heart Association. The study comprised of cases spanning 14-90 years. Out of 300 cases, 262 (87%) were males and 38 (13%) were females (Table 1). Majority of the cases belonged to the 5th decade of life (27%), followed by the 3rd and 4th decade of life (each 22%) (Table 1). 50% (151) of the cases were young individuals (aged < 40yrs) of which 84% (126) were males and 16% (25) were females.

Atherosclerosis

Regarding involvement of coronary arteries by atherosclerotic lesions, the LAD was the most commonly involved (33%) and the RCA the least (29%). The aorta was involved to a lesser extent (15%) than the coronaries. Left anterior ascending (LAD) was more associated with Type V and Type VI atherosclerosis (table 2).

The percentage of atherosclerotic lesions in the arteries increased with age of the persons, with persons above 70 yrs having the highest involvement (52%) (Table 3, figure 1). The incidence of type III atherosclerosis decreases with age while that of type V increases (Table 4, figure 1). A total of 74 coronaries showed occluded atherosclerosis, out of which LAD was the most commonly involved (31%) and LCX the least (11%). Type VI atherosclerosis was more (71%) associated with a complete occlusion and type III the least (table 5).

Myocardial Ischemia

Only 12.3% (37) showed changes of myocardial ischaemia or infarction, of which 92% were male and 8% female (figure 2). Maximum number of ischemia/infarction occurred in the 6th decade (31.5%) (Figure 3). Out of the 37 cases that showed changes of myocardial ischaemia/ infarction, only 25 cases (67.5%) had a triple vessel disease, 5 cases (13.5%) had involvement of 2 coronary artery, 6 (16%) cases had involvement of 1 coronary artery and only 1 (3%) case had involvement of none (table 6). LAD occlusion was found in more number of cases of ischaemia/infarction and RCA the least (Table 7). While the numbers of vessels with type V atherosclerosis with occlusion in myocardial ischaemia cases were more, type VI was more associated with occlusion (78%) (table 8). Table 9 shows incidence of occlusive atherosclerosis in all 300 cases and 37 cases showing changes of ischemia/ infarction. In 300 cases occlusive atherosclerosis was present in 74 (26%) coronaries, while in cases showing ischemia/ infarction it was present in 32 (86%) coronaries.

Discussion

The purpose of this study is to find the incidence of coronary atherosclerosis in different age groups and sex in the district of Surat, Gujarat (India) and determine the correlation between atherosclerosis and myocardial infarction and ischemia. The present study shows that the incidence of atherosclerosis increases with age, the highest being the 7th decade. Also, the type of atherosclerosis changes from type 3 to type 5 as age increases. The finding collaborated with that of other studies. [9,10] This may be due to increased incidence of comorbid factors like diabetes, hypertension, chronic smoking and other lifestyle risk factors that increases with age. Regarding the involvement of individual arteries by atherosclerotic lesions, left anterior descending (LAD) was the most commonly involved with the type of atherosclerosis being type 4 or type 5. This can be explained with the help of the fact that LAD supplies the major part of left ventricle and any occlusive atherosclerosis (type 5) leads to decrease blood supply to major part of the left ventricle and also the conducting systems leading to arrhythmias and left ventricular failure and ultimately death.

Regarding incidence of ischemia and myocardial infarction, maximum number of cases occurred in the 6th decade. The finding is in sync with the previous finding that incidence of atherosclerosis is more in the 7th decade of life, suggesting that both atherosclerosis and ageing may play an important role in causing death due to myocardial ischaemia in later age groups. Only 12.3% showed changes of myocardial ischaemia or infarction, of which 92% were male and 8% female. Myocardial infarction may have a sex predilection, but it is not possible to infer this point from this study as various comorbid factors like lifestyles, smoking, alcohol, diabetes, hypertension etc. can act as compounding factors in the causation of myocardial ischaemia. Further cohort studies with a larger group are required to find out the role of individual factors behind myocardial ischemia.

When it comes to the involvement of coronary arteries in myocardial ischemia, triple vessel disease was more associated with infarction than double or single vessel involvement. [9,10]

One case of myocardial infarction had no coronary artery involvement, pointing to the fact that there may be other factors other than atherosclerosis behind the causation of infarction.

Conclusion

From this study it can be concluded that atherosclerosis is one of the most important factors for myocardial infarction and its incidence and severity increases with age. The LAD is one of the most common sites of atherosclerosis and its involvement along with the other two coronaries is one of the major causes behind myocardial ischemia. Further studies are advised to find out the role of individual factors behind myocardial infarction.

References

[1.] World Health Organization. Noncommunicable diseases country profiles 2011: WHO global report. WHO. Available from URL: http://www.who.int/nmh/publications/ncd_profiles20 11/en/

[2.] World Health Organization Report: Technical report series, World Health Organization, Geneva. 1997.

[3.] Dwidedi S. Evaluation of coronary risk factors. MD (Medicine) Thesis. Banaras Hindu University, Varanasi. 1971.

[4.] Bansal RD, Chablani TD, Gulati PV. An epidemiological study of IHD in patients attending the cardiology clinic at AIIMS, New Delhi. Indian Med J 1970; 84-92.

[5.] Dwiwedi S, Dwiwedi G, Chaturvedi A, Sharma S. Coronary artery disease in the young : Heredofamilial or faulty life style or both. Journal Indian Academy of Clinical Medicine, 2000;1(3):222-229.

[6.] Virmani R, Ursell PC, Fenoglio JJ. Examination of the heart. Major Probl Pathol (Cardiovasc Pathol) 1991;23:1-20.

[7.] Ludwig J, Lie JT. Heart and vascular system. In : Ludwig J. ed. Current Methods of Autopsy Practice, 2nd ed. Philadelphia:W.B. Saunders. 1979. pp. 21-50.

[8.] Reiner L. Gross examination of the heart. In: Gould SE, ed. Pathology of the heart and Great vessels, 3rd ed. Springfiled, IL, 1968, pp.1111-1149.

[9.] Singh V, Pai MR, Coimbatore RV, Naik R. Coronary atherosclerosis in Mangalore--a random post mortem study. Indian J Pathol. Microbiol. 44(3):265-269.

[10.] Maru M. Coronary atherosclerosis and myocardial infarction in autopsied patients in Gondar, Ethiopia. J R Soc Med 1989;82(7):399-401.

Source of Support: Nil

Conflict of interest: None declared

DOI: 10.5455/ijmsph.2013.200620131

Received Date: 22.04.2013

Accepted Date: 20.06.2013

Bharati Jha, Divya Naik, Anshul Agarwal, Sayantan Jana, Mubin Patel

Department of Pathology, Government Medical College, Surat, Gujarat, India

Correspondence to: Sayantan Jana (janapath84@gmail.com)

Table-1: Age & Sex wise Distribution of Cases (n=300)

Age (years)   Male    %     Female    %    Total    %

    <19        11     4       04      1     15      19
   20-29       55     18      13      4     68      22
   30-39       60     20      08      3     68      23
   40-49       72     24      09      3     81      27
   50-59       38    12.5     00      0     38     12.5
   60-69       17    5.5      02      1     19     6.5
    >70        09     3       02      1     11      4
   Total      262     87      38     13     300    100

Table-2: Incidence and Type of Atherosclerosis in
Different Coronary Arteries and Root of Aorta (n=300)

   Type of        LAD    LCX    RCA    Aorta
Atherosclerosis

   Type III        29     37     29     29
    Type IV        33     26     35     16
    Type V         33     20     20     05
    Type VI        06     03     05      0
     Total        101     86     89     50
  Total in %       33     28     29     16

Table-3: Incidence of Atherosclerosis in Different Age
Groups

Age     No. of   No. of Arteries   No. of Arteries    %
        Cases       Examined           Showing
                                   Atherosclerosis

20-29     68           272               28          10
30-39     68           272               52          19
40-49     81           324               112         34
50-59     38           152               75          49
60-69     19           76                37          48
>70       11           44                24          54

Table-4: Involvement by Different Grades of
Atherosclerosis in Different Age Groups

Age     Type III (%)   Type IV (%)   Type V (%)   Type VI (%)

20-29        7              2           0.3            1
30-39       8.5            6.5          2.5           1.5
40-49       13.5           12            8             1
50-59       14.5           19            14            2
60-69       14.5           20           14.5           0
 >70        11.5            9           29.5           2

Table-5: Incidence and Type of Atherosclerosis
Associated with Occlusion in Coronaries

Types           LAD (101)   LCX (86)   RCA (89)   Total    %

Type III (95)      --          1          --        1
Type IV (94)        9          3          9        21     22
Type V (73)        19          13         10       42     57
Type VI (14)        4          2          4        10     71
Total              32          19         23       74
%                  31          11         25

Figure in bracket indicates the total number of coronaries
involved by atherosclerotic changes

Table-6: Involvement of No. Coronaries in Myocardial
Infarction

3 Coronaries   2 Coronaries   1 Coronary   No Coronary
     25             5             6             1

Table-7: Atherosclerosis associated with Occlusion
in Individual Coronary Artery in Cases of
Ischemia/Infarction

Coronary   Atherosclerosis + Occlusion
  LAD                  14
  LCX                  10
  RCA                  08
 Total                 32

Table-8: Incidence of Type of Atherosclerosis
associated with Occlusion in cases of Ischemia/
Infarction

Type       Ischaemia/    Atherosclerosis     %
           Infarction     with Occlusion

Type III       26               01           4
Type IV        35               07          20
Type V         31               17          55
Type VI         9               07          78

Table-9: Comparison of Incidence of Atherosclerosis
with Occlusion in All Cases with Cases of Ischemia and
Infarction

Arteries   All cases   Cases of Ischaemia or Infarction

LAD           32                      14
LCX           19                      10
RCA           23                       8

Figure-2: Incidence of Ischemia/Infarction in Different
Sexes

Males       92%

Females      8%

Note: Table made from pie chart.

Figure-3: Age Wise Distribution of MI Cases

          total cases   MI   %

<19 yrs       15        0    0

20-29         68        3    2

30-39         68        9    6

40-49         81        11   9

50-59         38        12   31.5

60-69         19        5    26

>70           11        3    27

X axis: age groups in years, Y-axis: percentage

Note: Table made from bar graph.
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Title Annotation:RESEARCH ARTICLE
Author:Jha, Bharati; Naik, Divya; Agarwal, Anshul; Jana, Sayantan; Patel, Mubin
Publication:International Journal of Medical Science and Public Health
Article Type:Clinical report
Geographic Code:9INDI
Date:Oct 1, 2013
Words:2048
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