In the past, a mosquito bite used to be nothing more just another annoying itch. With dengue fever cases on an all-time high1 in 2020, getting a mosquito bite has now become an alarming call; especially if there are also symptoms such as high fever, rashes, muscle and joint pains. Among these patients, a small proportion of them can experience various complications resulting in deaths. Myocarditis is one of them.
In this article, Senior Cardiology Consultant Dr. Eric Chong will walk us through myocarditis, a deadly complication behind dengue fever.
Myocarditis is the acute inflammation of myocardium, the heart muscle responsible for contracting and relaxing to pump blood in and out of the heart. It is a common complication of dengue infection. During the worst dengue outbreak in China in 20142, 201 out of 1782 infected patients who were part of a research study, were found to have myocarditis. It is also found that the incidence of myocarditis increased with the severity of their dengue infection.
Another fatal case involving a 41-year-old Chinese man brought up in 2013 study3 showed that the patient experienced a complicated dengue viral infection with acute myocarditis. As it involved a major organ (heart), the case was later classified as severe dengue according to the World Health Organization (WHO)’s dengue classification.
Based on his experience, Dr. Chong shared that dengue fever-induced myocarditis can be fatal if diagnosed and treated late. In fact, it is a common cause of dengue deaths.
When asked how myocarditis is diagnosed, Dr. Chong said: “It can be diagnosed via echocardiogram and cardiac enzymes tests such as troponin and electrocardiogram (ECG). Based on the patient’s medical history, we can also deduce if the patient is likely to be suffering from myocarditis as well.”
“Dengue fever patients with myocarditis would usually also experience chest pain, breathlessness, excessive sweating, palpitation and exhibit ‘rubbing’ heart sounds during clinical examination,” Dr. Chong added.
In the same study2 conducted in 2014, it was found that most dengue patients with myocarditis were ECG-positive, this suggests that suspect patients should undergo an ECG examination first due to its high sensitivity.
Asked for his thoughts on this finding, Dr. Chong shared:
“For patients with severe dengue haemorrhagic fever, the critical phase of potential myocardial injury and organ failure tend to develop when fever subsides. This usually occurs in day four to seven of dengue fever. Cardiac examination and ECG are therefore crucial during this period for patients demonstrating cardiac symptoms as early detection and intervention can save lives.”
Treatment for dengue fever is largely supportive. However, in the case where myocarditis is present, additional medication could be used to reduce the risk of severe heart failure, shock and fatal arrhythmia.
In more severe cases, doctors may improve the heart pumping function better with intravenous (IV) diuretics and inotropic BP supporting medications. Additional medications for heart failure and anti-inflammatory medications can also be used to save the heart and patient’s life, when administered early.
There is no known prevention measures for myocarditis but it is advisable to avoid any forms of viral infection because when an infection takes place, our body produces additional white blood killer cells - which in turn release chemicals such as cytokines - to fight against it. When these chemicals enter our heart, it can inflame our heart muscle hence causing myocarditis.
Bringing up Dengvaxia, a dengue vaccine approved by WHO and Ministry of Health, Dr. Chong advised: “Those aged 12 to 45 with a history of dengue fever can get themselves vaccinated against the disease with Dengvaxia. This helps to minimize the risks of complications like myocarditis during subsequent dengue exposures, as repeated dengue infection posts the highest risk of severe complications.”
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1 Liu, V. 2020. 2020 dengue outbreak set to be worst on record. The Straits Times. Retrieved from: https://www.straitstimes.com/singapore/2020-dengue-outbreak-set-to-be-worst-on-record
2 Li, Y. Y., Hu, Z.W., Huang, Y.L., Li, J.P., Hong, W.X., Qin, Z.H., Tong, Y. W., Li, J. L., Lv, M.F., Li, M. Y., Zheng, X. K., Hu, J., Hua, J. H., Zhang, F.C., Xu, D. 2016. Characterization of Myocarditis during the worst outbreak of dengue infection in China. Medicine (Baltimore). doi: 10.1097/MD.0000000000004051
3 Gan, V. C., Leo, Y. S., Marques, N. 2013. Dengue myocarditis in Singapore: two case reports. Infection (New York) Vol. 41, Iss. 3. (Jun 2013): 709-14. Doi: 10.1007/s15010-012-0392-9