Discussion

The myocardial involvement during COVID-19 disease has been frequently reported in children with multisystem inflammatory syndrome. ^{Reference Feldstein, Rose and Horwitz4} However, there are a few reports concerning children with pre-existing dilated cardiomyopathy and experienced acute myocarditis during the acute phase of COVID-19 disease. ^{Reference Kristoffersen, Knudsen and Møller5}

Adult patients with cardiovascular disease have a higher risk of myocardial injury and mortality during COVID-19 disease. ^{Reference Guo, Fan and Chen6} However, there are no sufficient data to support the association between heart disease and severe COVID-19 in children. The frequency of comorbid disease in paediatric COVID-19 studies was between 25 and 35.6% ^{Reference Hoang, Chorath and Moreira7,Reference Götzinger, Santiago-García and Noguera-Julián8} and was shown to be an independent risk factor for admission to the paediatric ICU.

The most common electrocardiography findings in COVID-19 infection are QTc prolongation, low QRS amplitudes, transient T-wave inversion, and non-specific ST segment elevation in paediatric series. ^{Reference Regan, O’Byrne and Stewart1,Reference Ramcharan, Nolan and Lai2} Arrhythmias including ventricular, supraventricular tachycardia ^{Reference Regan, O’Byrne and Stewart1} , or high-grade atrioventricular block have been reported in paediatric children with multisystem inflammatory syndrome cases.

Triangular QRS-ST-T waveform electrocardiography pattern, so-called “shark fin sign,” is defined as a unique, giant wave (amplitude ≥ 1 mV) resulting from the fusion of the QRS complex and the ST segment. In this electrocardiography pattern, QRS complexes show “triangular” morphology with the positive polarity in the leads. ^{Reference Cipriani, D’Amico and Brunello3}

Cipriani et al observed the triangular waveform electrocardiography pattern in 1.4% of adult cases with ST elevated myocardial infarction. ^{Reference Cipriani, D’Amico and Brunello3} This electrocardiography pattern is usually associated with a large area of transmural myocardial ischemia and predicts ventricular fibrillation, cardiogenic shock, and mortality.

Triangular waveform electrocardiography pattern is very rarely occurs in pericarditis ^{Reference Hasibuan, Intan and Wilujeng9} , ibuprofen intoxication and hyperkalemia. ^{Reference Cipriani, D’Amico and Brunello3} Symanski et al speculated that the triangular waveform pattern is a result of the dramatic slowing of transmural electrical conduction, due to biochemical and ion concentration changes (potassium loss, fall in pH, calcium overload, and sodium channels inactivation) during acute myocardial ischemia. Our case had mild hypokalemia and metabolic alkalosis when her electrocardiography pattern occurred. However, the elevated cardiac biomarker levels and remarkably ST elevation persisted, even after correction of her electrolyte disturbance.

In our case, coronary angiography excluded the coronary occlusion due to thrombosis or any other cause (air or lipid embolisation) and congenital or acquired coronary abnormalities or CHD (including patent foramen ovale). There was no laboratory evidence of atherosclerotic heart disease. There was a possibility of myocardial injury or ischemia during surgery. However, she had no myocardial ischemia findings in electrocardiography or increased cardiac enzyme levels post-operative on the first day. Abnormal electrocardiography findings and increased cardiac biomarkers levels occurred on day 2 after surgery, so we excluded myocardial ischemia during surgery. Except sepsis and possible COVID-19 myocarditis, there was no reason to explain electrocardiography abnormalities and increased cardiac biomarker levels.

Distinctive echocardiographic features of Takotsubo syndrome have been described in adult cases with COVID-19 infection and one paediatric case with children with multisystem inflammatory syndrome in literature; ^{Reference Ludwikowska, Tracewski and Kusa10} however, echocardiographic findings were not compatible with Takotsubo cardiomyopathy in our case.