Acute myocardial infarction in a hospital cohort of malaria

Heart failure associated with imported malaria: a nationwide Danish cohort study

AIMS

Despite adequate treatment, recent studies have hypothesized that malaria may affect long-term cardiovascular function. We aimed to investigate the long-term risk of cardiovascular events and death in individuals with a history of imported malaria in Denmark.

METHODS

Using nationwide Danish registries, we followed individuals with a history of malaria for the risk of incident heart failure (HF), myocardial infarction (MI), cardiovascular death and all-cause death (1 January 1994 to 1 January 2017). The population was age- and sex-matched with individuals without a history of malaria from the Danish population (ratio 1:9). We excluded patients with known HF and ischaemic heart disease at inclusion.

RESULTS

We identified 3912 cases with a history of malaria (mean age 33 ± 17 years, 57% male, 41% Plasmodium falciparum infections). The median follow-up was 9.8 years (interquartile range 3.9-16.4 years). Event rates per 1000 person-years for individuals with a history vs. no history of malaria were HF: 1.84 vs. 1.32; MI: 1.28 vs. 1.30; cardiovascular death: 1.40 vs. 1.77; and all-cause death: 5.04 vs. 5.28. In Cox proportional hazards models adjusted for cardiovascular risk factors, concomitant pharmacotherapy, region of origin, household income and educational level, malaria was associated with HF (HR: 1.59 [1.21-2.09], P = 0.001), but not MI (HR: 1.00 [0.72-1.39], P = 1.00), cardiovascular death (HR: 1.00 [0.74-1.35], P = 0.98) or all-cause death (HR 1.11 [0.94-1.30], P = 0.21). Specifically, P. falciparum infection was associated with increased risk of HF (HR: 1.64 [1.14-2.36], P = 0.008).

CONCLUSION

Individuals with a history of imported malaria, specifically P. falciparum, may have an increased risk of incident HF.

Prevalence of Cardiovascular Complications in Malaria: A Systematic Review and Meta-Analysis

Recent studies have suggested that malaria may affect the cardiovascular system. The aim of this systematic review and meta-analysis was to determine the prevalence of cardiovascular complications in symptomatic malaria patients. We searched databases such as Pubmed, Embase, Cochrane, and Web of Science (January 1950-April 2020) for studies reporting on cardiovascular complications in adults and children with malaria. Cardiovascular complications were defined as abnormalities in electrocardiogram (ECG), cardiac biomarkers, and echocardiography on admission or during outpatient examination. Studies of patients with known heart disease or cardiovascular evaluation performed after the start of intravenous antimalarial medication were excluded. The study was registered in International Prospective Register of Systematic Reviews (PROSPERO) (No.: CRD42020167672). The literature search yielded 1,243 studies, and a total of 43 studies with symptomatic malaria patients were included. Clinical studies (n = 12 adults; n = 5 children) comprised 3,117 patients, of which a majority had Plasmodium falciparum (n = 15) and were diagnosed with severe malaria (n = 13). In random-effects models of adults, the pooled prevalence estimate for any cardiovascular complication was 7% (95% CI: 5-9). No meta-analysis was conducted in children, but the range of abnormal ECG was 0-8%, cardiac biomarkers 0-57%, and echocardiography 4-9%. We analyzed 33 cases (n = 10 postmortem), in which the most common cardiovascular pathologies were myocarditis and acute coronary syndrome. All histopathological studies found evidence of parasitized red blood cells in the myocardium. Cardiovascular complications are not uncommon in symptomatic adults and children with malaria. Additional studies investigating malaria and cardiovascular disease are encouraged.

The Role of Blood Viscosity in Infectious Diseases

Blood viscosity is increased by elevated concentrations of acute phase reactants and hypergammaglobulinemia in inflammation. These increase blood viscosity by increasing plasma viscosity and fostering erythrocyte aggregation. Blood viscosity is also increased by decreased erythrocyte deformability, as occurs in malaria. Increased blood viscosity contributes to the association of acute infections with myocardial infarction (MI), venous thrombosis, and venous thromboembolism. It also increases vascular resistance, which decreases tissue perfusion and activates stretch receptors in the left ventricle, thereby initiating the systemic vascular resistance response. This compensates for the increased vascular resistance by vasodilation, lowering hematocrit, and decreasing intravascular volume. This physiological response causes the anemias associated with malaria, chronic inflammation, and other chronic diseases. Since tissue perfusion is inversely proportional to blood viscosity, anemia may be beneficial as it increases tissue perfusion when erythrocyte aggregating factors or erythrocytes with decreased deformability are present in the blood.

Malaria and the heart

A 40-year-old healthy manual labourer from a malaria endemic area with no known risk factors for atherosclerotic coronary vascular disease was admitted to our hospital with a history of fever with chills and rigours. Physical examination revealed tachypnoea and icterus. Peripheral smear showed trophozoites of Plasmodium vivax and thrombocytopaenia. The patient was administered artesunate. Six hours after admission, he complained of severe substernal chest pain. A 12-lead ECG revealed ST elevations in leads I, II and aVL. Troponin T and creatine kinase MB were elevated and the random blood sugar was 49 mg%. Echocardiogram revealed left ventricle lateral wall hypokinesia. Hypoglycaemia was corrected. A provisional diagnosis of acute coronary syndrome as a complication of malaria or its treatment was made. He was treated with low molecular weight heparin and nitrates. The patient improved symptomatically. A repeat ECG was normal.