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Table of Contents
Year : 2021  |  Volume : 10  |  Issue : 3  |  Page : 83-87

A novel electrocardiogram characteristic in patients with myocardial injury due to COVID-19

1 Rajaie Cardiovascular Medical and Research Center, Iran University of Medical Sciences, Tehran, Iran
2 Cardiovascular Research Center, Tabriz University of Medical Sciences, Tabriz, Iran

Date of Submission17-Apr-2021
Date of Acceptance17-Aug-2021
Date of Web Publication03-Nov-2021

Correspondence Address:
Dr. Maryam Chenaghlou
Cardiovascular Research Center, Tabriz University of Medical Sciences, Madani Heart Hospital, Daneshgah Street, Tabriz
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/rcm.rcm_21_21

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Background: Coronavirus disease of 2019 (COVID-19) is a respiratory disease which can lead to cardiovascular complications including myocarditis, myocardial infarction, and heart failure. Electrocardiogram (ECG) may change in patients with COVID-19 with or without heart involvement. In this study, the ECG changes were evaluated in myocardial injuries due to COVID-19. Methods: This study was done on 22 COVID-19 patients with ST segment elevation in ECG and high troponin level. COVID-19 was confirmed using reverse-transcription polymerase chain reaction test. The ECG variables were evaluated by an expert cardiologist. Statistical analyses were carried out on ECG variables where the significance level of 0.05 was assigned. Results: Of 22 patients, 17 cases (77.3%) were male and 6 cases (27.3%) had a history of coronary artery disease. The most common myocardial involvement was extensive anterior type (31.8%), followed by anterior type (22.7%). Sinus rhythm was observed in 95.5% of patients and 54.5% had low voltage ECG in limb leads. No significant correlation was found between low voltage ECG and demonstrable etiologies of low voltage. Conclusion: The prevalence of low voltage ECG was significantly high in limb leads of patients with myocardial injury due to COVID-19 which was considerably greater than that of myocarditis or myocardial infarction patients.

Keywords: COVID-19, electrocardiogram, low voltage, myocardial infarction, myocardial injury, myocarditis

How to cite this article:
Mirtajaddini M, Salehi R, Chenaghlou M. A novel electrocardiogram characteristic in patients with myocardial injury due to COVID-19. Res Cardiovasc Med 2021;10:83-7

How to cite this URL:
Mirtajaddini M, Salehi R, Chenaghlou M. A novel electrocardiogram characteristic in patients with myocardial injury due to COVID-19. Res Cardiovasc Med [serial online] 2021 [cited 2023 Feb 7];10:83-7. Available from: https://www.rcvmonline.com/text.asp?2021/10/3/83/329843

  Introduction Top

Coronavirus disease of 2019 (COVID-19) is a new infectious disease which is the cause of 2020 pandemic. The main system involved by COVID-19 is the respiratory system. However, other organs such as heart could be involved.[1],[2] The cardiovascular complications of COVID-19 include myocardial injury due to myocardial infarction or myocarditis, acute heart failure, cardiac arrhythmia, and sudden cardiac death.[3] Acute myocardial injury due to COVID-19 has multifactorial etiologies including direct virus invasion, autoimmune mechanism, vascular inflammation, coronary spasm, thrombus formation, plaque instability, and cytokine storm.[4],[5],[6],[7] In addition to common electrocardiogram (ECG) changes due to myocardial injury, such as ST segment and T wave changes, COVID-19 can lead to several ECG abnormalities.[8],[9],[10] In this study, the ECG changes were evaluated in patients with myocardial injury due to COVID-19.

  Methods Top

This study is an observational study in patients with myocardial injury due to COVID-19 admitted at Madani hospital, a tertiary center of cardiovascular diseases in northwest of Iran, from April to October, 2020. The COVID-19 diagnosis was confirmed using positive real-time reverse transcription polymerase chain reaction test from nasopharyngeal swab sample of patients. Chest computed tomography (CT) scan had been done before or during patients' hospitalization. ECG and laboratory tests were performed at admission, and transthoracic echocardiography (TTE) was done during hospitalization. In this study, the criteria of myocardial injury due to COVID-19 were ST elevation in at least two contiguous leads equal or more than 1 mm and high troponin level which occurred from 3 to 20 days after positive COVID-19.

The 12-lead ECG was recorded in supine and standard position (25 mm/s and 10 mV/mm) at admission time. All ECGs were analyzed by an expert cardiologist who had no information about patients' characteristics. QRS complex voltage, QRS rate, Cardiac rhythm, QRS axis, P wave morphology, PR interval duration, PR segment depression, ST segment elevation, and corrected QT interval duration based on Fridericia formula were evaluated in ECGs. Each variable was measured in three beats, and the mean of them was recorded.

Myocardial injury were categorized based on location of ST segment elevation, inferior myocardial injury (ST segment elevation in leads II, III and aVF), lateral myocardial injury (ST segment elevation in leads V5 and V6), inferolateral myocardial injury (ST segment elevation in leads II, III, aVF, V5 and V6), septal myocardial injury (ST segment elevation in leads V1-V3), anterior myocardial injury (ST segment elevation in leads V1-V6), and extensive myocardial injury (ST segment elevation in leads V1-V6, I and aVL). Low voltage ECG refers to peak to peak QRS complex <5 mm in limb leads and <10 mm in precordial leads.[11] Twenty-three patients were entered in the study. Left bundle branch block and left ventricular hypertrophy can affect QRS complex amplitude;[11] therefore, one of patients who had left bundle branch block was excluded. No patient had left ventricular hypertrophy. Finally, 22 patients were included in the study.

The statistical analysis was done using Excel and SPSS software. The numerical variables with normal distribution are presented as mean ± standard deviation, and the categorical variables are reported as percentage. Simple linear regression was used for the evaluation of relationship between low voltage ECG in limb leads and pleural effusion in chest CT scan, left ventricular ejection fraction by TTE, or QRS axis deviation. The relationship between low voltage ECG in limb leads and survival was evaluated using Pearson correlation. The P < 0.05 was considered statistically significant.

  Results Top

The mean age of patients was 69.36 ± 11.32 years. Most of patients were male (87.3%). About 27% of patients had a history of coronary artery disease and only one patient had a history of chronic obstructive pulmonary disease. No patient was under mechanical ventilation at the time of ECG recording. Three patients underwent primary percutaneous intervention and other patients received only medical treatment. The mean of left ventricular ejection fraction by echocardiography was 33% ±9%. Pericardial effusion was not seen in any of patients by echocardiography. Chest CT scan of patients showed pulmonary ground-glass opacity in all patients, and pleural effusion was seen in six patients (27.3%). Demographic, radiographic, and echocardiographic characteristic of patients are summarized in [Table 1].
Table 1: Demographic, radiographic, and echocardiographic characteristics of patients

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The blood group of most patients in this study was A+ (36.4%). The laboratory findings are presented in [Table 2].
Table 2: Laboratory findings of patients

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Extensive anterior myocardial injury was the most common type of cardiac involvement location (31%), followed by anterior, inferior, inferolateral, septal, and lateral regions. The mean QRS rate was 84 ± 23 beat/min. Twelve patients (54.5%) had low voltage ECG in limb leads, one of them had low voltage ECG in precordial leads and one had low voltage ECG in both limb and precordial leads [Figure 1]. The ECG characteristics are summarized in [Table 3].
Table 3: Electrocardiographic characteristics of patients

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Figure 1: Distribution of electrocardiogram voltage findings in patients

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No associations were found between low voltage ECG in limb leads and QRS axis deviation, left ventricular ejection fraction, or pleural effusion. The in-hospital mortality rate was 59.1%. The correlation between low voltage ECG in limb leads and mortality was rejected.

  Discussion Top

Various respiratory infections may lead to cardiovascular complications. Kwong et al. found that influenza can result in acute myocardial infarction during 1stt week of infection diagnosis.[12] In the other study, community-acquired pneumonia was recognized as a cause of cardiovascular diseases.[13] COVID-19 as a new respiratory virus can affect cardiovascular system as well.

COVID-19 with or without cardiac involvement may lead to several ECG changes. Angeli et al. showed that pericarditis changes such as PR depression and concave ST segment elevation are the most common COVID-19-induced ECG changes.[9] In several studies, the QT interval prolongation was observed, in spite the fact that some previously prescribed drugs in COVID-19 patients can prolong QT interval.[14],[15],[16] The other ECG changes due to COVID-19 include PR interval prolongation, right and left bundle branch blocks.[9],[16] Several ECG patterns have been identified in COVID-19 patients with cardiac involvement. ST segment elevation is commonly observed in COVID-19 patients due to acute myocardial infarction, myocarditis, and Takotsubo syndrome.[16],[17],[18],[19] In a case series, 14 cases of 18 COVID-19 patients with ST segment elevation myocardial infarction had focal ST segment elevation. Coronary angiography was done in only nine patients which showed obstructive coronary artery disease in 6 (67%) patients.[20]

In this study, ECG changes of acute myocardial injury due to COVID-19 were evaluated. Most of patients had sinus rhythm and normal QRS complex axis. The extensive anterior myocardial injury was the most common type of myocardial injury. No patient had PR segment depression as a sign of acute pericarditis.Furthermore, the PR interval was normal without prolongation. The prevalence of low voltage ECG in limb leads was significantly high in our study. Low voltage ECG may have various causes, which alter voltage generation, such as infiltrative cardiomyopathies or defect in voltage transmission to the electrodes in cases with anasarca, obesity, pulmonary hyperinflation, large pleural, and pericardial effusion.[21],[22],[23],[24],[25] The etiology of low voltage ECG only in limb leads is unknown. Goldberger described that the low amplitude ECG in limb leads and high amplitude in precordial leads can be signs of congestive heart failure.[26] Chinitz et al. showed that nearly 50% of their studied patients with low limb lead voltages had not any demonstrable etiology. More than 20% of these patients had small pericardial effusion and 11% of the patients had evidence of myocardial infarction in ECG.[27] Therefore, pericardial inflammation may lead to low voltage ECG regardless of the effusion size.[21] Acute myocardial infarction with alteration of QRS axis without impairment of voltage generation can result in QRS voltage reduction.[28] In our study, 54.5% of patients with myocardial injury due to COVID-19 had low amplitude QRS in limb leads which was not due to QRS axis deviation. In a study in 1971, 12% of patients with acute myocardial infarction had evidence of low amplitude ECG within 3 days of admission.[29] The incidence of low voltage ECG in myocardial infarction was estimated about 22% in Rotmensch study.[30] Kobayashi et al. showed that 19% of patients with anterior ST elevation myocardial infarction had low QRS voltage in limb and precordial leads and only 6% had low ECG voltage in limb leads.[31]

Pure myocarditis is the other cause of low voltage ECG through various mechanisms including myocardial and pulmonary edema.[32],[33] Nakashima et al. showed that 18% of patients with myocarditis had low amplitude QRS in limb and precordial leads.[32] The reduction of QRS amplitude due to COVID-19 has been reported in some studies. Angeli et al. showed that Cornell voltage (the sum of the R wave amplitudes in aVL and S wave amplitude in V3)[34] was significantly reduced in COVID-19 patients.[9] In Bertini study, low QRS amplitude in limb leads was observed in 5% of the COVID-19 patients due to mechanical ventilation, chronic pulmonary disease, and myocardial edema. Two cases of the Takotsubo syndrome have been reported due to COVID-19 where the ST elevation and low amplitude ECG in limb leads were detected in their ECGs. It should be noted that one of these cases had hemorrhagic tamponade.[17],[18] Low voltage ECG was reported in 3.4% of COVID-19 patients by Elias et al.[35] Bergamaschi et al. demonstrated the prevalence of low voltage ECG in limb leads as 5.6% due to COVID-19.[36]

In our study in addition to high incidence of low voltage ECG in limb leads, we showed that there is no association between low voltage ECG in limb leads and left ventricular ejection fraction, pleural, or pericardial effusion. Despite the high incidence of low voltage ECG in limb leads in this study. No correlation was found with in-hospital mortality of patients which is in contrast with the results of some previous studies.[30] Kobayashi showed that low voltage ECG may be correlated with multivessel disease and in-hospital CABG; while it was not confirmed in the Tan study.[37] In concordance with our study, Bergamaschi et al. and Elias et al. found that low voltage ECG at the admission time, is not a prognostic factor in patients with COVID-19.[35],[36]

  Conclusion Top

This study showed high prevalence of low voltage ECG in limb leads in patients with acute myocardial injury due to COVID-19. The prevalence is higher than low voltage ECG in patients with acute myocardial infarction or myocarditis in previous studies. This finding may be related to more myocardial edema in patient with COVID-19 in comparison with other etiologies.


The sample size is limited in our study. The absence of confirmatory modalities for defining the exact etiology of myocardial involvement including cardiac magnetic resonance imaging, myocardial biopsy, or autopsy are the other limitations of the current study.

Ethical clearance

The consent was obtained from the patients.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

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  [Figure 1]

  [Table 1], [Table 2], [Table 3]

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