Clinical Features and Short-Term Outcomes in Virus-Induced Bradycardia: Comparison Between Covid and non-Covid Infected Patients (preprint)

Covid-19 outbreak has drawn attention to the fact that viral infections might present with clinical bradycardia. Seeking its clinical significance, not yet unveiled by the literature, we come across other viral infections that also show clinical bradycardia during its clinical course, such as dengue fever and viral diarrhea. The clinical presentation of the latest seems to be severe, often presenting with orthostatic intolerance and fatigue symptoms, requiring expert consultation irrespective of the infection stage, and in case of dengue fever, frequently during the recovery phase. Meanwhile, in Covid-19 infected patients, the bradycardia observed is mild, frugal, and usually asymptomatic. Thus, we conducted a comparison between two different groups of patients with viral infection displaying clinical bradycardia during hospital stay: Covid and non-Covid patients regarding clinical and Holter monitoring parameters. All patients had other causes of bradycardia excluded and echocardiography and cardiac biomarkers ruled out acute myocarditis. The results showed that non-Covid patients presented with significantly lower mean and minimum heart rates (HR) on Holter monitoring, as well as longer times in with HR < 50 beats per minute (bpm).  SDNN and pNN>50% were also significantly higher in non-Covid patients. The minimum systolic BP was significantly lower in non-Covid patients. The study shows that Covid-19 is not the only viral infection that may display with clinical bradycardia, but it’s much milder than other viral infections such as dengue fever and viral diarrhea. It remains unclear the mechanism throughout Covid-related bradycardia comes about.

Predictors of QT Interval Prolongation in Critically-ill Patients with SARS-CoV-2 Infection Treated with Hydroxychloroquine (preprint)

Background: Hydroxychloroquine (HCQ) has been described as a potential treatment for SARS-CoV-2 infection. However, there are safety concerns regarding its QT interval and pro-arrhythmic effects. Objective: This trial aimed to determine the predictors of QT interval prolongation and pro-arrhythmic effects in patients hospitalized for SARS-CoV-2 infection and receiving HCQ. Methods: We performed a retrospective observational study of 45 critically-ill patients hospitalized because of SARS-CoV-2 infection and treated with 800 mg of HCQ at day 1 and 400 mg on days 2-5. Clinical aspects and outcomes, basal and final corrected QT (QTc) interval, and the incidence of arrhythmias and arrhythmogenic death were observed. Independent predictors of QTc prolongation were identified using multivariable logistic regression analysis. QT interval prolongation was considered substantial at final QTc [≥] 480 ms. Results: The mean age was 60.9 {+/-} 16.67 years and 28 (62.2%) patients were men. Basal QTc was 442 {+/-} 28 ms, and the final QTc interval was 458 {+/-} 34 ms, for a mean QTc interval variation of 15 {+/-} 11 ms. There was no arrhythmogenic death. The need for hemodialysis remained a statistically significant predictor of QT interval enlargement (odds ratio, 10.34; 95% confidence interval, 1.04-102.18; p = 0.045). Conclusions: HCQ promotes mild to moderate QT interval prolongation. The risk of QT interval prolongation is higher among patients with acute renal failure requiring hemodialysis.