Results
The cohort consisted of 91 patients (age 62.7±15.1 years, 44% females,). Excessive QTc prolongation occurred in 23% of patients receiving hydroxychloroquine/azithromycin, increasing from 437±37 to 504±41 ms. In 14% of the cohort, the QTc exceeded 500 ms. The baseline characteristics of those with and without significant prolongation are shown in Table 1. Patients with excessive prolongation were generally older (age 70.0±15.1 vs 60.5±14.5, p=0.016), with more hypertension (58% vs 40%, p=0.045), renal insufficiency(52% vs 20%, p=0.006), coronary artery (33% vs 8%, p=0.01) and cerebrovascular disease (24% vs 3%, p=0.01). In addition they appeared to develop greater severity of disease with 10/21 (48%) requiring mechanical ventilation compared to 15/70 (21%) without significant QT prolongation (p = 0.03). 9/21 (43%) patients with excessive QT prolongation had baseline renal insufficiency or developed acute renal failure. An additional concurrent QT-prolonging medication was administered in 42% of patients. Among patients with excessive QT prolongation, a concurrent QT prolonging drug was used in 67% of patients versus only 34% in patients without excessive QT prolongation (p=0.01). Most was due to intravenous propofol, which was used in 48% of patients with excessive QT prolongation compared to only 19% of patients without (p=0.01).
Significant ventricular arrhythmias occurred in 2 patients. One patient had classic TdP (Figure 1) and the second patient developed polymorphic VT that degenerated into VF in the setting of severe multisystem disease. Table 2 shows the results of the univariable and multiple logistic regression analysis. Older age (> 75 years), prolonged baseline QTc (> 460 ms), impaired renal function (GFR < 60 ml/min), and concurrent use of a high risk QTc-prolonging drug were each associated with excessive QTc prolongation. Multiple regression demonstrated the use of additional QT prolonging agents (especially propofol) to be independently associated with QTc prolongation [any drug: adjusted OR 3.69, CI (1.22, 11.20), p=0.02; propofol: adjusted OR 3.28, CI (1.06, 10.17), p=0.04].