DISCUSSION
Our study is the first study to examine the findings of lead aVR on superficial ECG in patients with Sars-Cov-2 infection. The primary result found in this study is that the positive T wave in lead aVR is an independent risk factor for mortality. The secondary result is that D-dimer and LDH values are independent risk factors, which has also been shown in previous studies.
The Sars-Cov-2 virus, which first emerged in December 2019, has spread all over the world in a short time and caused a pandemic. There is currently no prophylactic treatment for this disease. Although Sars-Cov-2 infection primarily affects the lungs and causes pneumonia and/or acute respiratory distress syndrome, it leads to complications such as myocarditis, cardiac tamponade, transit ST elevation, acute heart failure, arrhythmia (tachycardia or bradycardia), and sudden cardiac death. (17) Cardiac damage can occur through a diverse range of pathways. While it may be directly related to cardiac damage, it may cause myocardial inflammation and edema by inhibiting ACE-2 receptors and impairing the cellular defense mechanism. Another mechanism of action is the cytokine storm, which results from excessive cytokine release from type1-2 T helper cells and leads to immunopathological events. These factors may cause direct myocyte damage as well as coronary spasm, plaque rupture, microthromboembolism by leading to vascular inflammation and hypercoagulopathy. (18-19-20) A recently published study showed that the SARS-CoV-2 virus causes cell necrosis by activating CD40, caspase recruitment domain family member 8 (CARD8), and serine/threonine kinase 4 (STK4) in human bile duct epithelial cells. A similar mechanism is thought to occur within the myocardial tissue. As a result, irregular cell death and fibrosis may occur in the myocardial tissue. (21) In the clinical study of WANG et al., acute heart damage, shock, and arrhythmia complications were observed in 7.2% and 8.7%, 16.7% of the patients, respectively. (22)
Although the lead aVR is often neglected on a superficial 12-lead ECG, it provides diagnostic and prognostic information for many cardiovascular diseases. Since the lead aVR is a unipolar right extremity lead, represents the cavity of the heart, and is the opposite of the main cardiac vector, all positive deflection waves are negative in the lead aVR. (23) A positive T wave in the lead aVR is usually an uncommon finding. Although the exact mechanism is unknown, there are various hypotheses. According to the most common and valid hypothesis, the T wave is thought to be positive after vectorial deviation caused by damage to the left ventricular apical, inferior and inferior lateral wall due to various reasons. (24-25) Recent studies have shown that the T wave positivity in the lead aVR is a marker of ventricular repolarization abnormality and provides information on short and long-term cardiovascular mortality in patients who have heart failure, anterior myocardial infarction, and receive hemodialysis for various reasons .(15-16) In their long-term follow-up study of male individuals, Tan et al. showed the T wave positivity as an independent risk factor for cardiovascular events.(26) The 33-month follow-up study of 93 patients with heart failure and narrow QRS ECG by Okuda et al. showed that the T wave positivity provided long-term prognostic information independent of other causes. (27) The 31-month follow-up study of 93 patients with ICD (implantable cardioverter defibrillation) and ischemic and non-ischemic cardiomyopathy by Tanaka et al. showed that a positive T wave in the lead aVR was an independent risk factor for long-term mortality. (28) The study of 86 cases by Donmez et al. showed that the occurrence of the T wave positivity in the lead aVR after transaortic valve implantation (TAVI) procedure was an independent risk factor for postoperative short and long-term mortality. (29) The NHAES (National Health And Nutrition Examination Survey) study of 7,928 cases showed that the T wave positivity in the lead aVR was an independent risk factor for cardiovascular events. Moreover, the addition of this factor to the Framingham risk score may improve the distinction of patients with moderate risk factors. (30) Ekizler et al. showed that positive TAVR was an independent risk factor for cardiovascular events in patients with peripartum cardiomyopathy. In our study, the examination of the electrocardiographic findings of the lead aVR in patients with COVID-19 infection revealed that positive TAVR alone was an independent indicator for mortality. (31) This suggests that a positive TAVR wave provides information on the entire myocardial tissue rather than the apical, inferior, and inferior lateral wall.