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.