Background: Prolonged QT interval is a risk factor for arrhythmias. We have previously reported that macrolides are often (23%) prescribed in patients admitted with chest symptoms, despite ECGs are not performed in every individual. The aim of this ongoing audit was to assess the impact of comorbidities and COVID-19 on QT interval.

Methods: Medical records and ECGs were analysed in 129 patients who were admitted to a large, tertiary respiratory centre in the United Kingdom. QTc was calculated following correction according to Fridericia. Prolonged QTc was defined as >450ms.

Results: Fourteen patients (11%) had QTc prolongation at admission. Twenty-six patients (20%) were already on QT prolonging medications and macrolides as well as fluoroquinolones were prescribed in 32 cases (25%), including six patients who were already on QT prolonging medications. Patients with diabetes had significantly longer QTc (432±12ms vs. 414±27ms, p=0.03) and patients with COVID-19 infection had a trend for a longer QTc (430±93ms ± 415±28ms, p=0.08). Most importantly, the prevalence of prolonged QTc was significantly higher in patients with COVID-19 (22 vs. 8%). There was an inverse correlation between white blood cell count and QTc (?=-0.21, p=0.02). There was no relationship between QTc and gender, age, chronic cardiac, respiratory, or mental health disease.

Conclusions: ECGs should be performed in patients who are prescribed with macrolides and fluoroquinolones, especially those who have underlying diabetes and COVID-19 infection.