In sub-Saharan Africa, heart failure has become a major clinical and public health issue in recent decades owing to its morbidity, mortality, and cost to society. In a systematic review and meta-analysis of studies of patients admitted in primary to tertiary care facilities published between January 1, 1996, and June 23, 2017, 9.4% to 42.5% of patients admitted for medical heart diseases in Cameroon, Nigeria, and Togo had heart failure [1][2]. The etiologies of heart failure in sub-Saharan Africa varied widely across studies, of which hypertensive heart disease was the most frequent, with a pooled prevalence of 39.2% (95% confidence interval [CI]: 32.6% - 45.9%) [1][2]. Studies from Central Africa are sparse. Only 2 studies conducted at the Yaounde General Hospital in Cameroon were included in this systematic review and meta-analysis for the Central African region. With 167 patients in the 1998-2001 study [3] and 148 patients in the 2013-2016 study [4], the most frequent etiology of heart failure in this combined study population of 315 patients was hypertensive heart disease (42.3%; 95% CI: 20.2% - 66.1%) [1][2]. For more than 5 decades, hypertension has been identified as the most frequent precursor of heart failure in males and females [5]-[8].

Kinshasa, the capital city of the Democratic Republic of the Congo (DRC), with its population currently estimated at more than 16 million, is the largest city in Central Africa. The prevalence of hypertension in Kinshasa was 13% in 1984 [9], which increased to 31% in 2008 [10]. Among 298 patients prescribed anti-hypertensive medication in a network of primary care facilities in the city in 2012, 42% did not adhere to treatment, and 77% had uncontrolled hypertension [11]. From December 2015 to January 2016, the same proportion of uncontrolled hypertension (77%) was found in another study of 260 hypertensive patients in the network [12]. Despite this documented high and increasing prevalence of hypertension, the high prevalence of non-adherence to anti-hypertensive treatment and the associated high prevalence of uncontrolled disease, the risks of heart failure associated with hypertension in Kinshasa have not been characterized [5]-[7]. There is no cardiovascular disease registry in the DRC, and the in-hospital prevalence of heart failure in Kinshasa is currently unknown. In a recent cross-sectional study of physicians practicing in cardiology health services in Kinshasa, 52% indicated that they did not know the in-hospital prevalence of heart failure in the city, but 95% thought that this unknown prevalence tended to increase [13].

We conducted a retrospective study of medical admissions at Monkole Hospital, a public tertiary care hospital that maintained computerized files of all hospital admissions from January 1, 2019, to December 31, 2019, to determine the in-hospital prevalence of heart failure among adult patients diagnosed with a cardiovascular disease in Kinshasa.

The involvement of the heart in infectious diseases was extensively studied in Kinshasa at the peak of the human immunodeficiency virus/acquired immune deficiency syndrome epidemic [14][15], but not as much research has been conducted on noncommunicable, chronic heart diseases [16]. To our knowledge, this is the first study assessing the in-hospital prevalence of heart failure diagnoses and their putative causes in Kinshasa. We found that heart failure was the most frequent diagnosis among all adult patients diagnosed with a cardiovascular disease at Monkole Hospital in 2019. The one-year in-hospital prevalence of a heart failure diagnosis of 32.8% we report is higher than the 42.5% in-hospital heart failure prevalence observed during 4 years in a tertiary care facility in Nigeria [17], the 28.6%, 30.0%, and 33.3% in-hospital heart failure prevalences observed during 3 years in tertiary care facilities in Cameroon and Togo [3][4][18], and the 25.6% in-hospital heart failure prevalence observed during 2 years in another study conducted in a tertiary care facility in Togo [19].

In our study, the outcome and the predictor variables were recorded at the same time. Whether causation should be inferred from the associations we report should be based on the known biological plausibility of the processes involved, the demonstrated temporal sequence of causes preceding the disease from longitudinal studies, and their consistency with other studies [1][2][5]-[7][20]. Because heart failure is a clinical syndrome resulting from different etiologies and pathophysiology and not a specific disease [8], we can report with a high degree of confidence that hypertensive heart disease is the leading cause of heart failure in the adult population of Kinshasa, and that age ≥ 65, ischemic heart disease, pulmonary embolism, arrhythmia, and hypertension at least double the odds of an adult “kinois” (an inhabitant of Kinshasa) of developing heart failure. This study provides documentation of morbidities that are leading to in-hospital heart failure diagnosis in the city [13], and it adds to the literature on causal associations of heart failure for Central Africa, a region of the continent where fewer studies are conducted in this area [1][2].

There is one study of heart failure etiologies from the eastern DRC city of Lubumbashi that was published in 2018 [21] and was not included in the systematic review and meta-analysis of studies published up to June 23, 2017 [1][2], nor was it included in a narrative review of studies published between 2010 and 2021 [22]. In this study of 231 patients diagnosed with heart failure at a university hospital (n = 159) and at a private hospital (n = 72) between November 2014 and September 2016, dilated cardiomyopathy was the most frequent heart failure etiology (48%). This was similar to the findings of 2 studies from the neighboring eastern African country of Rwanda, where the leading cause of heart failure was dilated cardiomyopathy, found in 40% to 54% of cases [1][2][23][24]. Our finding in the western DRC city of Kinshasa that hypertensive heart disease was the putative cause of 22% of heart failure cases was also similar to 20% to 66% of heart failure cases attributed to hypertensive heart disease in Yaounde, a Central African city in Cameroon, northwest of the DRC [3][4]. These geographic distributions suggest a regional clustering of environmental, dietary, and behavioral risk factors that are leading to the development of cardiovascular diseases and ultimate heart failure in sub-Saharan African populations, including within the DRC [25]-[27].

Mortality data that are routinely collected and widely available in developed countries [28], are either unavailable or unusable for the DRC due to data quality issues. Statistics compiled by the World Health Organization for the DRC, which the organization advised to interpret with caution, ranked stroke, ischemic heart disease, and hypertensive heart disease among the 10 leading causes of death in 2021, having caused 49.1 deaths per 100,000, 40.2 deaths per 100,000, and 31.4 female deaths per 100,000 populations, respectively [29]. The high prevalence of life-threatening cardiovascular diagnoses in our study raises concerns about patients’ outcomes at the hospital, particularly in-hospital heart failure mortality. In the study conducted by Malamba-Lez et al. in Lubumbashi [21], heart failure was the cause of 19% of in-hospital deaths and of 35% of deaths within one-year of diagnosis. The in-hospital heart failure mortality in Lubumbashi was within the range of 16.4% reported in Yaounde, Cameroon [30], 18.3% reported in Libreville, Gabon [31], and 19% reported at Moi Teaching and Referral Hospital in Western Kenya [32].

There are several limitations to this study. The retrospective review of pre-recorded data limited access to additional information on the criteria used to diagnose heart failure and all associated comorbidities among hospitalized patients. Reliance on data recorded on Excel spreadsheets without validation of diagnostic criteria against patients’ charts affects the reliability of data we reported on. Only one patient was diagnosed with heart failure among 32 patients who were diagnosed with arrythmia. The extremely wide confidence intervals for arrhythmia in logistic regression analyses likely reflect the small sample size. The 52 patients diagnosed with what we labeled “uncharacterized heart disease” (11.8%) had a diagnosis recorded on the spreadsheets as a “cardiopathy to be determined”, which represented diagnostic uncertainties. Had we accessed the clinicians’ notes in the patients’ charts, we would have collected more information to better characterize these conditions. The diagnoses we report are based on standard practices both at the hospital and in the city. However, they were made by physicians who recently demonstrated a very good knowledge of the guidelines of the European Society of Cardiology for the diagnostic of acute and chronic heart failure [13].

Although this study was not designed to change practice, it underscores the urgent need for a cardiovascular disease registry for the DRC to ensure research in cardiovascular diseases is conducted and practice of heart failure management is improved in Kinshasa, a city of 16 million in constant demographic growth, with a high and increasing prevalence of hypertension, the most frequent comorbidity associated with heart failure in sub-Saharan Africa [1][2][9][10][13]. The study additionally highlights the many opportunities for research at Monkole Health Center, particularly with the strength that the health center’s infrastructure and organizational structure offer. For example, general services manage medical ambulances for the transport of patients and emergencies. The 24/7 emergency service of the Monkole Health Center (SAMU Monkole) is equipped with medical vehicles with resuscitation capacity and trained teams, which allows both the care of patients on the ground until transport to the hospital, increasing the chance of survival of patients with conditions such as stroke or cardiac decompensation (https://monkole.cd/en/). A study of 202 patients with confirmed diagnosis of stroke between May and October 2022 at 12 hospitals in Kinshasa showed that 89% of patients arrived at the hospital more than 4.5 hours after stroke onset [33]. The study highlighted the need to expeditiously coordinate transportation and admission of patients to a hospital where diagnostic resources and expert health care professionals for stroke management are available. Monkole Hospital is such a place. Future studies should seek to determine the in-hospital heart failure mortality among patients admitted at Monkole Hospital.