The phenomenon of epidemiological transition schematically consists of a decline in infectious diseases and malnutrition in favor of non-communicable diseases, primarily cardiovascular diseases and cancers. In developed countries, the control of most infectious diseases has gradually allowed this shift towards chronic and degenerative diseases, while simultaneously, life expectancy lengthened over the past century. This same phenomenon is now widely underway in developing countries, currently at different stages of progress depending on the respective levels of development of these countries [1] .

Epidemiological studies show that cardiovascular diseases are at the heart of these changes. It is estimated that at the beginning of the 20th century, they were responsible for less than 10% of global mortality. Currently, the number of deaths attributable to cardiovascular diseases is estimated at 17.7 million, accounting for 31% of total global mortality. Among these deaths, it is estimated that 7.4 million are due to coronary heart disease and 6.7 million to stroke [2] . Of the 17 million deaths occurring before the age of 70 due to non-communicable diseases, 82% occur in low- or middle-income countries, and 37% are attributable to cardiovascular diseases [2] . Projections indicate that the annual number of deaths attributable to cardiovascular diseases, for example, is expected to rise from 17 million in 2008 to 25 million in 2030 [3] . The explanations are multiple, mainly related to population aging and lifestyle changes accompanying socio-economic development and intensive urbanization; behavioral risk factors such as smoking, physical inactivity, poor diet, and excessive alcohol consumption.

These diseases generate significant direct costs (years of life lost, disabilities, use of healthcare) and indirect costs (loss of productivity due to mortality and morbidity) that are likely to increase; all age groups are affected, and more than 90% of premature deaths due to non-communicable diseases occur in low- or middle-income countries [4] - [7] . Today, one of the main sustainable development goals is to reduce by one-third, by 2030, the rate of premature mortality due to non-communicable diseases [8] .

In Africa, too much emphasis is still placed on infectious diseases. Yet, these silent killers, cardiovascular diseases (CVDs) and chronic non-communicable diseases (CNCDs) in general, deserve more sustained attention. In Senegal, WHO estimated that non-communicable diseases accounted for 42% of all deaths in 2018; and cardiovascular diseases (17%) represented the largest proportion [9] - [11] . Premature mortality due to CVDs is a real public health issue; in Sub-Saharan Africa (SSA) and Senegal in particular, we have little epidemiological data in this regard. This is what motivates our study, which focuses on the epidemiology of cardiovascular mortality among individuals of working age, considering that the legal retirement age in Senegal is 60 years.

The objectives of the study were to determine cardiovascular mortality in the population aged up to 60 years, analyze the epidemiological, clinical, and paraclinical aspects, and determine the etiological aspects and associated prognostic factors.

During the study, 188 deaths were recorded among 1752 hospitalized patients of all ages. Among these patients, 73 deaths concerned adults aged 60 years or less, representing a specific mortality rate of 8.8% for this population, or 39% of the observed proportional mortality.

The highest number of deaths was observed in 2021, in the specific context of the SARS-CoV-19 pandemic ( Figure 1 ). On the socio-epidemiological level, the average age was 44 years. The most affected age groups were those of 51 to 60 years and 31 to 40 years ( Figure 2 ). Men were slightly more represented with a male-to-female ratio of 1.2. In this study population, 43.8% were unemployed and 56% had a low socio-economic status. The majority resided in the suburbs of Dakar.

Clinically, the history of cardiovascular diseases was frequent (20.5%), with a predominance of rheumatic valvulopathies, cardiomyopathies, and unexplained cardiopathies. Cardiovascular risk factors included physical inactivity (76.7%), hypertension (28.8%), smoking (21.9%), and diabetes (15.1%) ( Figure 3 ). Stratified cardiovascular risk showed very high (20.5%), high (12.4%) to low (45.2%) risks according to ESH classifications. Venous thromboembolic events were also common, often related to gyneco-obstetric conditions (24%) or prolonged bed rest (24%).

The main symptoms at admission included dyspnea (72.6%), lower limb edema (38.4%), chest pain (28.8%), and cough (24.7%) ( Table 1 ). Physical signs often revealed heart failure (63%), heart murmurs (23%), and arrhythmias (18%).

Paraclinical examinations showed dyslipidemia in 39.3% of patients with 36% having elevated LDL-c, rhythm disorders in 46.6% with a predominance of atrial fibrillation (21.9%), and chest X-ray abnormalities with 49.3% showing cardiomegaly and 33% showing signs related to pleuropneumonia. Cardiac ultrasound revealed significant alterations in the left ventricular ejection fraction in 81% of cases, pulmonary hypertension (60.4%), and dilation of the inferior vena cava (69.1%). It also allowed the diagnosis of ischemic heart disease in 48% of cases, followed by rheumatic valvular disease in 28% of cases ( Figure 4 ). Coronary angiography and CT angiography confirmed diagnoses in some patients, despite their high cost.

The most frequent diagnoses were ischemic heart diseases (40%), including 44.8% of acute coronary syndromes (ACS) and 55.2% of chronic ischemic heart diseases, rheumatic valvulopathies (18%), pulmonary embolism (15%), and strokes (4.1%).

Treatments mainly involved diuretics (63%), anticoagulants with LMWH (52%) and VKAs (42%), inotropic agents (47.9%). Other medications used included beta-blockers (36%), ACE inhibitors or ARBs (31%). Thrombolysis was performed in 38.5% of ACS cases and 35.4% of pulmonary embolism cases. Angioplasty was performed in 30.8% of ACS patients.

Immediate causes of death included cardiogenic shock (45.2%), acute respiratory failure (38.5%), septic shock (37%), heart failure (31.5%), and rhythm disorders (19.2%) ( Table 2 ). However, 67% of patients died during on-call hours.

Our analysis revealed a significant link between mortality from ischemic heart disease and cardiovascular risk factors ( Table 3 ), as well as between mortality from pulmonary embolism and risk factors for venous thromboembolic disease ( Table 4 ).

The factors significantly associated with death were age over 50 years, low socio-economic status, ischemic heart disease (p = 0.034), rheumatic valvulopathies, pulmonary embolism (p = 0.034), hypertension (p = 0.009), smoking (p = 0.011), diabetes (p = 0.011), dyslipidemia, bed rest (p = 0.001), morbid obesity (p = 0.001), and COVID-19 infection (p = 0.017).

Cardiovascular mortality rate in this tertiary setting among patients aged ≤ 60

years old was 39%, with a male predominance and a mean age of 43.5 years old. Ischemic heart disease was the leading cause of deaths followed by rheumatic heart disaese. Hypertension was the most frequent preventable cardiovascular risk factor. We also noted a prevalence of cardiogenic shock of 50%. Deaths were more frequent during on-call hours, probably due to medical team fatigue and increased workload Before interpreting these findings, it is important to aknowledge the limitations of our study. The retrospective data collection and lack of electronic records make it challenging to retrieve some data from patients

records such as ECGs. Incomplete or unreadable records led to substansial loss of data. The lack of resources also prevented the completion of certain necessary investigations such as echocardiography, leading to an information bias regarding the cause of death.

Notwithstanding these limitations, our study offers valuable insights regarding cardiovascular mortality and its determinants in our Sub-Saharan setting. Our findings emphasize that there is a crucial requirement to allocate resources towards developing a strong surveillance system with centralized electronic records. This will enable efficient monitoring of cardiovascular morbidity and mortality, ultimately leading to better management and prevention of related health issues.

Our findings appears to be similar to the literature [12] - [15] . The Pan American Health Organization reported a CVD mortality rate of 32.4% in 2012. In France, Santos et al. reported in 2015 that 8.9% of CVD deaths occurred prematurely [12] [16] . In Madagascar, a study by Rafamatanantsoa showed that more than half of CVD deaths occurred before the age of 60 [17] . According to Murray and Lopez, CVD mortality in sub-Saharan Africa among adults under 60 years old was 26.3% in 1990 [18] . These data suggest an increase in premature CVD mortality, especially in developing countries. Low and middle-income countries are experiencing a shift towards noncommunicable diseases while continuing to struggle with infectious diseases. The fact that rheumatic heart disease was the second most frequent cause of cardiovascular death corroborates it perfectly. In sub-Saharan Africa, the share of disability-adjusted life years linked to cardiovascular diseases (CVDs) has risen from 19% to 30% of the total burden [19] . Moreover, the number of CVD deaths in Sub-Saharan Africa (including Senegal) has increased by over 50% in the last thirty years. CVD-related deaths in SSA tend to happen at younger ages, leading to a high number of disability-adjusted life years (DALYs) [20] . Socioeconomic determinants of health have a great impact on health inequity. Rapid urbanization, growing population and lifestyle modifications with fatty diet and lack of physical activity lead to the rise of atherosclerotic risk factors such as hypertension and diabetes [21] - [23] . This highlights the need to inform proper preventive strategies to tackle this growing burden.

Our study points out several future directions. We need to conduct a nationwide cohort study to monitor the incidence of cardiovascular diseases, its risk factors and lethality. Also, investing in good linkage systems and electronic health records will facilitate cardiovascular disease surveillance in our country. This is now mandatory to overcome the double burden we are currently facing.

The study highlights the complexity of managing cardiovascular diseases in a resource-limited context. It also underscores the importance of ischemic heart diseases and rheumatic valvulopathies in cardiovascular mortality in Senegal. The high rates of complications and premature mortality emphasize the need to improve access to care and early screening for cardiovascular risk factors and rheumatic heart disease. This study underscores the necessity for an integrated approach to address the challenges of cardiovascular diseases, focusing on prevention, early diagnosis, and improvement of healthcare system.

Sincere thanks to Professor Abdoul Kane for his unwavering support, his foresight, and his exemplary management.

This study was approved by the ethics committee of the Cheikh Anta Diop University of Dakar.

The data and materials of this study are available upon request and ready to be shared. For further information, please contact the corresponding author, Aliou Alassane NGAIDE.

Aliou Alassane NGAIDE, and Abdoul KANE designed the study protocol, participated in the data collection and writing of the draft manuscript.

Ngone Diaba GAYE and Momar DIOUM oversaw the execution of the study, participated in data analysis and critically revised the manuscript for important intellectual content.

Mame Diarra SENE and Mouhamadou Bamba NDIAYE participated in study design and in data analysis.

Joseph Salvador MINGOU and Alassane MBAYE participated in statistical analysis and interpretation of results.