Paroxysmal supraventricular tachycardia is a common and generally benign arrhythmia. It rarely results in any adverse clinical outcomes. But it was reported that 30% of patients presenting with PSVT had significant troponin elevations . Because these patients had symptoms of chest pain and chest discomfort they were often misdiagnosed as ACS and given inappropriate treatments such as antiplatelet and antithrombotic therapy. Coronary angiography however revealed that most of them had normal coronary arteries. The mechanism of tachycardia-induced troponin elevation is not fully understood . Most authors are in agreement with the mechanism that tachycardia increases myocardial oxygen demand, while it decreases myocardial oxygen delivery because of short diastole during which myocardial perfusion occurs. So tachycardia ultimately leads to reduced myocardial perfusion which results in the release of cTnI into the circulation .
What are the characteristics of patients with elevated troponins due to PSVT? We reviewed the English-language scientific literature from the MEDLINE and ELSEVIER databases using the keywords “troponin” and“PSVT”. Most authors found that patients with elevated troponins after acute attack of PSVT were not at increased cardiovascular risk such as hypertension, diabetes or dyslipidemia . This agrees with our cases. They also believed that the duration of arrhythmia was not associated with troponin elevation . However, the maximal PSVT heart rate, ST-segment depression ≥1 mm during the episode of PSVT and the presence of impaired left ventricular systolic function were correlated with troponin elevation [6, 8].
Is coronary angiography necessary to be carried out in these patients with PSVT which resulted in elevated troponins? Dorenkamp’s study replied this question . In their retrospective analysis troponin levels were increased in 14 of 114 patients. Thirteen of the 14 patients were subjected to coronary angiography. The result was that no one had significant coronary stenosis. They found a positive exercise test was the best predictor of significant coronary artery disease and subsequent revascularization. A history of hypertension and age 60 years or more ranked secondly. So when we confronted a patient with PSVT and elevated troponin, we should pay attention to his medical history including cardiac risk factors and age. Then a noninvasive assessment for coronary stenosis such as the exercise test can be chosen before coronary angiography. This was not implemented well in clinical practice according to our cases and other reports.
What is prognostic significance of elevated troponins in these patients with PSVT? This question has different answers. Calberg and his colleagues made a retrospective review of 51 patients with PSVT, 38 of whom had cTnI value meassured at least one time . Eleven patients having elevated cTnI were followed up for thirty days. They found that none of patients had adverse cardiovascular outcomes. On the contrary, Chow and his colleagues’ research drew the conclusion that mild cTnI elevation in patients with PSVT was associated with increased risk of future cardiovascular events such as death, myocardial infarction or cardiovascular rehospitalization . They studied 78 patients including 29 patients with elevated cTnI. The mean follow-up period was 2.2 ± 1.7 years. These two retrospective studies had a common limitation that the numbers of patients were too small for analysis. Both prospective observational studies and larger retrospective studies are recommended to answer this question.