New information regarding COVID-19 continues to emerge daily. This content was based on the sources available at the time of writing.
After SARS-CoV-2 first emerged in China more than a year ago, it quickly became clear that the virus had broad effects beyond the respiratory system, with the potential to harm the heart and other organs. For that reason, ECG became a key tool in managing patients with COVID-19, as it could reveal signs of cardiovascular involvement, such as prolonged QT interval, and help physicians monitor the effects of drugs used to treat the disease.
As the medical community around the world scrambled to address the threat of the virus, medications for other conditions were repurposed, and some—including hydroxychloroquine, azithromycin, and certain antivirals—have known effects on the heart's conduction system, such as prolonging QT interval and even sparking life-threatening arrhythmias in some cases. A research letter in Nature Medicine showed that QT interval was severely prolonged to more than 500 ms in 11% of patients with COVID-19 who were treated with a combination of hydroxychloroquine and azithromycin.
Prevalence of Prolonged QT in Hospitalized COVID-19 Patients
While some of the treatments used in the early days of the pandemic have since fallen out of favor as more robust studies have been completed, data about their effects in patients with COVID-19 continues to accumulate.
A recent study in Clinical Infectious Diseases (CID) provides fresh insight into QT interval prolongation and life-threatening arrhythmias among patients hospitalized for COVID-19 at three hospitals in Italy and one in Germany. After a week, 14% of patients who had a normal QT interval corrected for heart rate (QTc) at admission and who initiated treatment during the hospital stay developed a prolonged QTc interval on standard 12-lead ECG. The average increase was 66 ms, or 16%. Factors that predicted a prolonged QTc were older age, a higher baseline heart rate, and use of dual antiviral therapy.
Life-threatening arrhythmias were infrequent, occurring in four patients (3.6%), although they were associated with a much higher in-hospital mortality rate (50% versus 9% overall). These findings are consistent with other studies of hospitalized patients that have been conducted over the course of the pandemic.
QT Prolongation and Less Severe COVID-19 Cases
QT prolongation, however, may not be as much of a concern for patients with COVID-19 who are not critically ill. A study in Scientific Reports examined patients who presented to the emergency department, initiated treatment after being admitted or as outpatients, and received a 12-lead ECG 48 hours later. Although a similar proportion of patients had a prolonged QTc interval compared to the sicker patients in the CID study (14.1%), the average increase in QTc was much lower, at just 1.8%. No patients developed torsades de pointes or experienced arrhythmic death. A prolonged QTc was associated with older age, a longer baseline QTc, and lower potassium levels.
"Ambulatory and not critically ill patients with COVID-19 treated with hydroxychloroquine, azithromycin, and/or antiretrovirals develop a significant, but not relevant, QT interval prolongation," the researchers conclude.
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The Importance of ECG Screening
The risk of QTc prolongation in patients with COVID-19 has practical implications for managing therapies and the use of ECG, several groups have said. The authors of the CID paper advise that when the QTc is longer than 500 ms, the drugs causing the prolongation should be stopped, or continuous ECG monitoring should be started. Moreover, they recommend a baseline ECG for all patients before initiating treatment to exclude inherited long QT syndrome and conduction disturbances.
But ECG can be more broadly useful in the setting of COVID-19, complementing the use of other screening tools, such as cardiac troponin testing, to provide information about cardiovascular involvement and prognosis.
"Indeed, compared to troponin, ECG can provide not only a generic diagnosis of myocardial injury or damage but can also orient to the specific pathophysiological mechanism and foster suspicion of pulmonary thromboembolic or in situ thrombosis of the pulmonary circulation, which are being described with increasing frequency," according to research published in the Journal of the American College of Cardiology.
A study in the Journal of the American Heart Association bolsters the idea that a combination of high-sensitivity troponin testing and ECG can predict 30-day mortality in patients hospitalized with COVID-19 better than either modality alone.
Checklist of ECG Abnormalities Associated with COVID-19
In a recent paper in Open Heart, researchers review what has been learned about the relationship between COVID-19 and cardiovascular issues over the course of the pandemic, with a focus on cardiovascular surveillance. A wide range of ECG abnormalities have been observed in COVID-19 patients, including:
- Ventricular tachycardia
- Torsades de pointes
- Supraventricular tachycardia
- ST elevation
- Sinus tachycardia in patients with cardiogenic shock and severe LV dysfunction
- Premature atrial and ventricular complexes
- Lateral T-wave inversion and prolonged QT
- Sinus rhythm with nonspecific ST and T-wave changes
In addition, a study in the Journal of Cardiac Failure showed that COVID-19 patients were more likely to die if they had ECG findings indicative of left-sided heart disease (atrial premature contractions, intraventricular block, and repolarization abnormalities) or right-sided disease (right bundle branch block).
As such, ECG plays a crucial role in COVID-19 management. The authors of the Open Heart paper call for "a strategic tier-based approach for initial assessment and management of COVID-19" and highlight the role of electrocardiography in patient care during the pandemic.