|Year : 1982 | Volume
| Issue : 2 | Page : 78-83
Considerations on the interrelation between some meteriological conditions and the development of acute myocardial infarction in Bombay (a preliminary communication).
BC Rodrigues, IJ Pinto
B C Rodrigues
|How to cite this article:|
Rodrigues B C, Pinto I J. Considerations on the interrelation between some meteriological conditions and the development of acute myocardial infarction in Bombay (a preliminary communication). J Postgrad Med 1982;28:78-83
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Rodrigues B C, Pinto I J. Considerations on the interrelation between some meteriological conditions and the development of acute myocardial infarction in Bombay (a preliminary communication). J Postgrad Med [serial online] 1982 [cited 2021 Jan 22 ];28:78-83
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Herberden was the first to point out that attacks of angina pectoris were more frequent in winter and that cold precipitates attacks of angina pectoris.
The Bureau of the census in Washington DC reported the peak incidence of ischaemic heart disease in winter and autumn and the statistical department of the W. G. Kerckhoff-Herzforschungs Institute of Bad Nauhein (Germany) using data from 1,600,000 deaths occurred in United Kingdom has found that there was a clear maximum number of deaths due to arteriosclerotic heart diseases in January-February. In temperate climates these observations have been confirmed by numerous investigators., , , , , , 
Burch has made special mention of the effect of temperature and humidity but little mention has been made of the effect of atmospheric pressure changes in precipitating acute myocardial infarction (AMI).,,, The present paper discusses the role of meteorological conditions including atmospheric pressure changes in the development of myocardial infarction in Bombay which has a tropical climate and compares these findings with those of Lisbon which has a mediterranean type of climate.
MATERIAL AND METHODS
Four thousand seven hundred and seventy nine cases of acute myocardial infarction (AMI) using the WHO diagnostic criteria were admitted in the Intensive Cardiac Care Unit, K.E.M. Hospital, Bombay between the years 1974 and 1979; using similar criteria, 2445 patients of AMI were admitted to the Hospital de Santa Maria, Lisbon from 1973 to 1977. Weather data in Bombay during these periods was supplied by the Director of Regional Meteorological Centre, Bombay. Monthly admissions of AMI and monthly mean of several meteorological variables, for the same period, namely air temperature and atmospheric pressure were considered [Table 1] and [Figs. 1],[FIG. 2]. In an attempt to study the special role of atmospheric pressure in the development of acute myocardial infarction, the admissions of AMI were plotted against the variations of that meteorological element [Fig. 1]. In case of Bombay, where those variations of atmospheric pressure are not so sudden as they are in Lisbon due to the passage of frontal systems and troughs, we plotted the admissions of AMI against the absolute values of monthly mean atmospheric pressure variation from one month to the next [Fig. 2].
Lisbon which is situated in the temperate zone has a comfortable cool mediterranean climate with a maximum incidence of AMI in the winter (January, December).,  Troughs and frontal systems pass over Lisbon causing sudden changes in the atmospheric pressure in spring, especially between March and May, and autumn resulting in secondary peaks in the incidence of AMI. These peaks correspond to troughs of the mean atmospheric pressure [Fig. 1].
Bombay is located in the northern hemisphere in the northern part of the intertropical zone surrounding the earth and for more than ten months of the year has an uncomfortably warm humid climate according to the classification of Brazol, Gregorczuk and Lansberg, with maximum temperature over 250C. It is affected by the migration of the intertropical convergence zone (ITCZ). Most cases of myocardial infarction occur in January and the number keep falling till July when the ITCZ migrations start northward. Thereafter it generally rises from August to December as the ITCZ migration moves southwards. However, in these periods the monthly mean pressure rises or falls, although the atmospheric pressure in Bombay has no sudden variations as those observed in Lisbon.
[Table 1] and [Fig. 2] show absolute values of these variations. It is further found that in spring and autumn equinox secondary peak incidence of AMI occurs which corresponds to small but significant atmospheric pressure fluctuations. In the first period when the ITCZ moves northwards there is a phase difference of one month between the 2 curves i.e. case number and mean atmospheric pressure variation. In the second period from August to December when the ITCZ moves southwards the curves are in phase.
According to Claude Bernard, the maintenance of a fixed milliu interne is an essential condition for free and independent life. Homo sapiens maintains a fixed body temperature at 370C mainly by means of mechanisms involving the cardio-vascular system. To maintain the constant temperature, the calorific energy provided in these conditions has to equal the energy lost, thus keeping a thermal balance with the environment., 
In Bombay where the temperature is above 250C for more than ten months of the year, considerable physical stress is placed on the heart. The work of the heart will therefore increase in order to supply additional amounts of blood to the skin surface to ensure against the loss of energy to maintain body temperature. The stroke volume, work, power and tension of the myocardium will also increase. In case of patients with overt or latent coronary heart disease, this physical stress may lead to a breakdown of the homeostasis resulting in acute myocardial infarction.
We have found that the changes in the atmospheric pressure are also important as a factor which influences the development of AMI, and a study of our data of Lisbon and Bombay also supports this contention.
In temperate zones with comfortable climates as experienced in Lisbon, Kiev and Paris, there is a peak incidence of AMI in winter and additional peaks in spring and autumn coinciding with sudden variations of atmospheric pressure generally caused by the approaching passage of the polar throughs and frontal system. Zhurenko in Kiev, Julian in Paris and Rodrigues,  in Lisbon have reported similar findings. Further, Tromp et al,  have reported that lipid levels, blood volume, fibrinogen level, ESR and capillary resistance and blood clotting are changed by the sudden variations in atmospheric pressure and temperature changes which facilitate intravascular thrombosis. These changes are graphically reproduced in [Fig. 1]. The graphs indicate that sudden variations of atmospheric pressure in autumn and spring cause a secondary rise of AMI and these correspond to troughs and cold branches of polar frontal waves that pass over Lisbon.
In Bombay the highest incidence of AMI occurs during the transition period -January and February when the curves for case numbers and atmospheric pressure are divergent. During the spring and autumn equinox, the curve for case numbers and atmospheric pressures are concordant. In the first period of April-July when ITCZ moves northwards, there is a phase difference of one month between the two curves. In the second period when the ITCZ moves southwards they are in phase.
It is observed that the maximum number of cases of AMI in Bombay occurred in January when the temperature was most comfortable and least in July when the temperature was > 250C and the climate warm and humid. These results differ from those of most workers in other hot humid environments in the northern hemisphere. We have noticed that in Bombay during these periods, changes and variations of atmospheric pressure occur which correspond to the peaks of AMI attacks. It appears therefore the atmospheric pressure variation plays a role of great importance in precipitating AMI in Bombay. More work in different hospitals in Bombay and other parts of India is required to confirm these preliminary observations.
We wish to thank the Dean, K.E.M. Hospital, Bombay for permission to publish this paper and Mr. Daniel, Director of Regional Meteorological Centre, Bombay for weather data.
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