Introduction

Sudden death (SD) has become a global health problem. It has a great public impact because it occurs unexpectedly, without apparent cause, and it may affect individuals of any age¹.

In general, SD is divided into (1) instantaneous or fulminant SD (ISD), which occurs seconds or minutes or up to an hour after the collapse and in which the individual literally falls dead, usually in the presence of witnesses and generally associated with cardiac pathology including arrhythmias and (2) not instantaneous SD (24 h SD) that occurs up to 24 h after the onset of symptoms².

SD, in general, is responsible for 4-5 million annual deaths worldwide, the majority due to ischemic heart disease (IHD)³.

Within the classification of ISD, sudden cardiac death (SCD) refers to death of cardiac origin that occurs within 1 h from the start of symptoms when death is witnessed.

In the United States of America, the SCD-adjusted rate by age and sex was 69/100,000 inhabitants, with an estimate of 212,910 cases in 2009¹. In Latin American countries, such as Cuba, the calculated rate for SCD was 90.9-101/100,000 inhabitants representing 11-12.3% of natural deaths⁴. In China, the rate was 41.3 cases/100,000 inhabitantsb/year⁵.

The most frequent causes of SCD include ischemic heart disease (60-70%), cardiomyopathies (20-30%), and primary arrhythmias (5-10%)⁶.

In Mexico, the estimated annual incidence of acute myocardial infarction cases is around 140,000, of which the fourth part dies in the event⁷.

Some authors in Mexico, considering the number of deaths due to acute myocardial infarction, have calculated approximately 33-53,000 SCD/year⁸.

SD is not only a health problem, but by the fact of being unexpected, it may be suspicious of criminality. After discarding a criminal act, SD continues to have great importance, especially when it occurs in young people, because it is often necessary, in addition to a SD protocol of autopsy, a molecular autopsy to detect certain pathologies such as hereditary arrhythmogenic diseases or channelopathies⁹.

The aims of the study were as follows: (i) to analyze the incidence of deaths from ischemic heart disease in two successive periods (1998-2006 and 2007-2015) to visualize the magnitude of the problem and (ii) to review the official reports of SD in the same lapse of time and to compare these data with those calculated for annual SCD according to literature.

Materials and methods

It was a cross-sectional, descriptive, and retrospective study. The national epidemiological files of SD (ISD, 24 h SD) stored in the National Health Information System (SINAIS)¹⁰, and the information about the number of inhabitants in Mexico and main causes of death, at the files of the National Institute of Statistics and Geography (INEGI)¹¹ were meticulously reviewed.

The cumulative incidence of deaths from ischemic heart disease in the periods of 1998-2006 and 2007-2015/10,000 inhabitants was calculated in the global population and in those less than 45 years of age. The same calculation stratified by sex was also performed. The population data for the first and second periods were obtained from the 2000 and 2010 population censuses, respectively¹¹.

The information issued by SINAIS in relation to SD was analyzed and it was contrasted with the number of SCD calculated for Mexico according to literature.

Results

During the period of 1998-2006, there wer incidence of 69.0 deaths/10,000 inhabitants in a population of 15 years or older; while in the population of 15-45 years of age, there were 19,100 cases with an incidence of 4.1/10,000 inhabitants (Table 1).

For the second period, the incidence increased, especially at the expense of mortality in men. This was remarkable even in young subjects because while the incidence of IHD in women between 15 and 45 years of age remained similar (1.6 and 1.7 for the first and second periods, respectively), in men, the increase was evident (Table 1).

The database with a record of SD in the general population in Mexico is the SINAIS. Two categories were found: ISD and 24 h sudden death (24 hSD). For 24 hSD, official record was found only from 1998 to 2005. As of the year 2006, this type of SD was no longer codified.

Table 2 shows the registered cases of ISD and 24 hSD at a national level in the general population ≥ 15 years of age according to SINAIS. In a period of 17 years, a total of 1394 cases of ISD were documented (an average of 82 cases/year). In the same period, in the group of ≤ 45 years, only 319 cases were reported nationwide (19 deaths/year in average), of which 192 were men and 127 were women. ISD in ≤ 45 years old was 22.8% of all cases.

When the population between 15 and 45 years was analyzed in the same period of time, 8687 deaths in women and 37,837 deaths in men were attributed to acute myocardial infarction. If it is known that in ischemic heart disease, SD is the first form of presentation in 19-26 % of patients¹², then in the group of 15 to 45 years old, calculating 20% of SD as the first manifestation of the disease, at least 9304 deaths (1737 women and 7567 men) could have presented as SD. This contrasts with the official report of 319 cases in total, for this same age group in the same lapse of time.

Table 2 shows also the number of 24 hSD cases from 1998 to 2005; there were 175 cases with an average of 22 cases/year. In individuals ≤45 years old, 38 cases were reported, 23 cases in men and 15 in women, with an annual average of five cases. All reports of 24 hSD were as mentioned, suspended without explanation since the year 2006.

Discussion

From the analysis carried out, it is evident that there is an under-registration of cases of SD in Mexico. The official figures are very low even when compared exclusively with the calculated SD of cardiac origin.

In the studied period of 17 years (1998-2014), only 1394 cases of ISD were registered, with an average of 82 cases/year. It is interesting to compare the official reports in Mexico with other countries. In Spain, in 1999, 9000 SD cases were calculated, with a population of around 40 million people at that time (22.5/100,000/year)¹³. In China, in 2015, approximately 544,000 cases of SCD were reported in a population of 1376 million (39.5/100,000/year)¹⁴. In 2014, there was a report in Germany of SCD rate of 81/100,000/year¹⁵; in Ireland, in 2008, it was 55.5/100,000/year¹⁶, and in Thailand, in 1993, 38/100,000/year¹⁷.

As showed in Table 1, mortality from ischemic cardiovascular disease in Mexico is increasing, especially in men; however, one of its consequences, the SD has a very low official register. The poor record of these health problems can have a negative impact on the establishment of prevention measures at the public policy level since there is no official epidemiological support to show the reality of the problem.

Given that, the highest percentage of SD occurs in subjects > 45 years old due to ischemic heart disease; it is advisable to control the risk factors such as atherosclerosis, obesity, diabetes mellitus, arterial hypertension, dyslipidemia, sedentary lifestyle, and smoking⁶. Furthermore, in the SCD in young people, it is necessary to implement preventive measures and detection of structural heart diseases and channelopathies¹⁸. Officially, 22.8% of all SD cases occurred in individuals between 15 and 45 years of age, and this is a worrisome situation. Preventive measures must be established, especially in high-performance athletes or in those children and young people in whom “innocent” clinical data (dyspnea, palpitations, and/or syncope) are not taken into consideration until it is done retrospectively after the SD of these subjects¹⁹.

Education of parents, teachers, coaches, and doctors is fundamental, as well as the participation of the government to control this health problem, in the Mexican population²⁰.

Conclusion

The record of cases of SD in Mexico is far below the reality. Even so, 22.8% of SD cases occur in individuals 45 years of age or younger. From the framework of public policy, the implementation of preventive measures is urgent; besides, the education of the population is a priority.