Cardiovascular Journal of Africa: Vol 32 No 5 (SEPTEMBER/OCTOBER 2021)

CARDIOVASCULAR JOURNAL OF AFRICA • Volume 32, No 5, September/October 2021 AFRICA 281 include T-wave abnormalities, ST-segment depressions and elevation, sinus pauses, atrial or ventricular ectopic rhythms, ventricular trigeminy and atrial fibrillation. 24 Diagnosis: an original algorithm to detect CV involvement in dengue The gold standard for thediagnosis of dengue is thedemonstration of viral fragments by real-time polymerase chain reaction (RT-PCR). This test is limited to the acute viraemic phase, which is usually restricted to a few days (one to five days after the onset of fever). In the convalescent phase or in the case of a negative RT-PCR result with high clinical suspicion, immunoglobulin M is diagnostic. 1,2 The identification of CV involvement due to dengue can be complex due to: (1) the absence of universal diagnostic criteria; (2) different forms of presentation; and (3) other diseases that that can alter the diagnostic findings such as the presence of pre-existent ECG abnormalities. The appearance of arrhythmias has been reported to be in the range of 34 to 75% of severe dengue cases, which can be identified through 12-lead ECG and 24-hour Holter monitoring. 3,4,22,29 The severity of heart rhythm disorders is not related to the severity or phase of dengue. 3,4 In addition to ECG abnormalities, elevation of cardiac biomarkers may indicate the presence of dengue CV involvement. A prospective study in Sri Lanka evaluated several cardiac biomarkers (myoglobin, creatine kinase-muscle brain-type, N-terminal pro-brain natriuretic peptide, heart-type fatty acid- binding protein, troponin T) in patients with dengue; 25% of patients had abnormal results in one or more biomarkers. Conversely, the correlation between biomarkers and cardiac function has not been clearly demonstrated in dengue. 14 ECG and cardiac biomarkers are particularly helpful in cases of myocarditis and left ventricular dysfunction. Transthoracic echocardiography is a non-invasive imaging method through which ventricular anatomy and function and some haemodynamic variables can be evaluated. The frequency of appearance of myocardial damage due to dengue seems to be directly related to the severity of the disease. Up to 36% of children with severe dengue have a left ventricular ejection fraction (LVEF) less than 50% compared to only 6.7% of cases with mild dengue. Up to 21% of patients may have dilated cardiac cavities and valve regurgitation, believed to be due to myocarditis. 14 In children hospitalised with severe dengue and depressed LVEF (< 50%), tachycardia and respiratory symptoms, pleural effusions, lower cardiac outputs and the need for greater fluid requirements were more likely to occur in patients with low LVEF. 14 Myocardial injury secondary to dengue can be fatal, therefore it is vital to asses ventricular function during infection. Echocardiography is also an important tool to assess and rule out other causes of heart failure, such as valve or ischaemic heart disease. 3,7,14,16 Cardiac magnetic resonance (CMR) is a useful tool for confirming suspected myocarditis, however its application in cases of dengue is limited. The main associated findings are hyperintensity in T2-weighted signals with late gadolinium enhancement. CMR is considered the gold standard for evaluation of the function of both ventricles. 6 Histological findings of the CV involvement of dengue include the appearance of petechial haemorrhage, interstitial oedema and infiltration of inflammatory cells such as neutrophils and lymphocytes in the myocardial tissue. 7 Although the number of deaths associated with severe forms of dengue is elevated, reports of post mortem findings are scarce. The prevalence of CV disease due to dengue is low, so the indiscriminate application of diagnostic tests can lead to erroneous conclusions. Patients with ECG alterations and those with clinical characteristics of heart failure should have an echocardiogram done. Additionally, if myocarditis is suspected, echocardiography should be conducted if available. 14 In Fig. 5, we propose an algorithm to guide the decision to use diagnostic tests in patients with suspected or confirmed dengue and possible CV involvement. Treatment No specific treatment exists for dengue. During the febrile phase, liberal oral fluid administration and antipyretic treatment with paracetamol is recommended. As for the severe forms, the mainstay of treatment is intravenous fluid management. Episodes of myocardial damage, associated or not with myocarditis, may be asymptomatic and treatment is unnecessary in most cases. 6,14 Dengue prevention using vaccines could be associated with a decrease in symptomatic cases, thus preventing CV manifestations. However, its use has not been authorised worldwide and remains controversial and limited to seropositive patients. 31 Supportive treatment is based on maintaining an adequate intravascular volume status through the administration of intravenous fluids, avoiding volume overload. Judicious use of diuretics should be considered where indicated, although they are associated with worse outcomes in patients with severe dengue. 14 Cases of severe dengue, if untreated, can cause a mortality rate as high as 20%. Appropriate case management and intravenous rehydration can reduce the mortality rate to less than 1%. 6 Dengue confirmed or suspected Clinical follow up Normal If available: perform CMR ECG TTE positive or inconclusive Abnormal TTE and cardiac biomarkers Abnormal: dengue cardiac involvement confirmed Cardiac symptoms? Chest pain, palpitations, irregularities of pulse, hypotension, pulmonary oedema, and/or features of shock Fig. 5. Diagnosis of dengue and its cardiac involvement. ECG: electrocardiogram, TTE: transthoracic echocar- diogram, CMR: cardiac magnetic resonance.