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].