From the Journals

‘Doubling down’ on hydroxychloroquine QT prolongation in COVID-19


A new analysis from Michigan’s largest health system provides sobering verification of the risks for QT interval prolongation in COVID-19 patients treated with hydroxychloroquine and azithromycin (HCQ/AZM).

One in five patients (21%) had a corrected QT (QTc) interval of at least 500 msec, a value that increases the risk for torsade de pointes in the general population and at which cardiovascular leaders have suggested withholding HCQ/AZM in COVID-19 patients.

“One of the most striking findings was when we looked at the other drugs being administered to these patients; 61% were being administered drugs that had QT-prolonging effects concomitantly with the HCQ and AZM therapy. So they were inadvertently doubling down on the QT-prolonging effects of these drugs,” senior author David E. Haines, MD, director of the Heart Rhythm Center at William Beaumont Hospital, Royal Oak, Mich., said in an interview.

A total of 34 medications overlapped with HCQ/AZM therapy are known or suspected to increase the risk for torsade de pointes, a potentially life-threatening ventricular tachycardia. The most common of these were propofol coadministered in 123 patients, ondansetron in 114, dexmedetomidine in 54, haloperidol in 44, amiodarone in 43, and tramadol in 26.

“This speaks to the medical complexity of this patient population, but also suggests inadequate awareness of the QT-prolonging effects of many common medications,” the researchers say.

The study was published Aug. 5 in JACC Clinical Electrophysiology.

Both hydroxychloroquine and azithromycin increase the risk for QTc-interval prolongation by blocking the KCHN2-encoded hERG potassium channel. Several reports have linked the drugs to a triggering of QT prolongation in patients with COVID-19.

For the present study, Dr. Haines and colleagues examined data from 586 consecutive patients admitted with COVID-19 to the Beaumont Hospitals in Royal Oak and Troy, Mich., between March 13 and April 6. A baseline QTc interval was measured with 12-lead ECG prior to treatment initiation with hydroxychloroquine 400 mg twice daily for two doses, then 200 mg twice daily for 4 days, and azithromycin 500 mg once followed by 250 mg daily for 4 days.

Because of limited availability at the time, lead II ECG telemetry monitoring over the 5-day course of HCQ/AZM was recommended only in patients with baseline QTc intervals of at least 440 msec.

Patients without an interpretable baseline ECG or available telemetry/ECG monitoring for at least 1 day were also excluded, leaving 415 patients (mean age, 64 years; 45% female) in the study population. More than half (52%) were Black, 52% had hypertension, 30% had diabetes, and 14% had cancer.

As seen in previous studies, the QTc interval increased progressively and significantly after the administration of HCQ/AZM, from 443 msec to 473 msec.

The average time to maximum QTc was 2.9 days in a subset of 135 patients with QTc measurements prior to starting therapy and on days 1 through 5.

In multivariate analysis, independent predictors of a potentially hazardous QTc interval of at least 500 msec were:

  • Age older than 65 years (odds ratio, 3.0; 95% confidence interval, 1.62-5.54).
  • History of (OR, 4.65; 95% CI, 2.01-10.74).
  • Admission of at least 1.5 mg/dL (OR, 2.22; 95% CI, 1.28-3.84).
  • Peak troponin I level above 0.04 mg/mL (OR, 3.89; 95% CI, 2.22-6.83).
  • Body mass index below 30 kg/m2 (OR for a BMI of 30 kg/m2 or higher, 0.45; 95% CI, 0.26-0.78).


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