HCQ induced QT prolongation- Primum non nocere.

To the Editor,

The article ‘Cardiovascular risks of hydroxychloroquine in treatment and prophylaxis of COVID-19 patients: A scientific statement from the Indian Heart Rhythm Society’ by Kapoor et al. [1] is a much-needed guideline for use of hydroxychloroquine (HCQ) in the current COVID-19 pandemic. It recommends performing a baseline electrocardiograph (ECG) and calculation QTc prior to starting HCQ.

Based on the existing evidences, though not conclusive, HCQ has been recommended for use as prophylaxis and treatment of COVID-19 in many guidelines. Although it is a safe drug, a serious adverse effect is QT prolongation, culminating in Torsades des Pointes or polymorphic ventricular tachycardia, leading to sudden cardiac death. Unfortunately, only few published literatures speak about the adverse reaction and precautions to be taken before using the drug (Table 1).

Table 1

The available literature on hydroxychloroquine induced electrocardiographic changes and current recommendations.

No.	Study/Recommendation/Guideline	Updated/Published	Recommendation
1	Indian pacing and electrophysiology journal [1]	April, 2020	Recommends baseline ECG in all and Bazett formula
2	CDC [3]	April 7, 2020	Follow FDA approval recommendation
3	FDA [4]	March 28, 2020	No recommendation
4	European medicine agencies	April 7, 2020	No recommendation (against use)
5	The centre for evidence-based medicine	March 25, 2020	No recommendation
6	American College of Cardiology [5]	March 29, 2020	Fridericia/Framingham formula for QTc
7	ICMR	March 21, 2020	No recommendation
8	BMJ- best practise [3]	April 7, 2020	No recommendation
9	WHO- Landscape analysis of therapeutics [3]	March 21, 2020	No recommendation

CDC- Centre for disease control, FDA- Food and Drug Administration, ICMR- Indian council of medical research, BMJ- British medical journal, WHO- World health organisation.

It is well known fact that QTc is calculated using various formulae viz., Bazett, Fridericia, Framingham, Hodges and Rautaharju. For drug induced QTc prolongation, the study by Vanderberk et al. advocated to use Fridericia or Framingham formula instead of Bazett formula, which may under correct QTc prolongation at low heart rate and overcorrect at high heart rate [2]. However, the Indian heart rhythm society [1] has recommended use of Bazett formula. In view of lack of studies comparing various formulae on a head-to-head basis and ease of using online calculators, the reason for choosing the particular formula is unclear. There is an urgent need to carry out further studies to look into the occurrence of Torsades de pointes and QTc prolongation with HCQ using various formulae and develop international guidelines for the same.

Funding

Financial support and sponsorship- Nil.

Contributions

All the 3 authors contributed to –Substantial contributions to the conception or design of the work; or the acquisition, analysis, or interpretation of data for the work; & Drafting the work or revising it critically for important intellectual content; & Final approval of the version to be published; & Agreement to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.