key: cord-1048714-n6zq8jrn
authors: Kapoor, Aditya; Pandurangi, Ulhas; Arora, Vanita; Gupta, Anoop; Jaswal, Aparna; Nabar, Ashish; Naik, Ajay; Naik, Nitish; Namboodiri KK, Narayanan; Vora, Amit; Yadav, Rakesh; Saxena, Anil
title: Reply to letters vide manuscript ID IPEJ-D-20-00072, and IPEJ-D-20-00073 regarding our paper “Cardiovascular risks of hydroxychloroquine in treatment and prophylaxis of COVID-19 patients: A scientific statement from the Indian Heart Rhythm Societyˮ
date: 2020-07-10
journal: Indian Pacing Electrophysiol J
DOI: 10.1016/j.ipej.2020.06.007
sha: d6b6c8d3d7b823b6de6ded6a3c142a8532e54e9f
doc_id: 1048714
cord_uid: n6zq8jrn

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there are numerous formulae that attempt to correct QT for heart rate using exponential methods (4, 5, 12) , linear correlation (6, 7, 8, 9) , logarithmic correction (10), and others (11) . There is considerable disagreement on which method is best for this purpose. As such, QTc is a derived value computed by one of these formulae. Therefore, in absence of a direct measurement of QTc, or a gold standard for reference, it is nearly impossible to prove superiority of any method for accuracy. There are no large studies confirming superiority of one method over others in a consistent manner. Most clinical studies have used the Bazett's formula for QTc correction and most outcome data that have associated risk of arrhythmic events based on QTc values in a LQT population are based on this formula. Bazett's formula was the first and remains most widely recognized and used method. It is mentioned in all current Cardiology and ECG textbooks, and also specifically recommended to calculate Schwartz score for diagnosis of long QT syndrome (13) . It is also the default formula for most QT interval correction apps.

Since the guidelines are meant for a wider audience including general physicians, the emphasis was on simplicity. Also, the paper is not primarily about QT interval, but on how to risk stratify and monitor COVID-19 suspects or patients who are to receive hydroxychloroquine for their treatment or prophylaxis. A detailed exposition of merits and demerits of different methods to compute QTc interval would have been a digression from the primary focus of the guidelines.

Cardiovascular risks of hydroxychloroquine in treatment and prophylaxis of COVID-19 patients: A scientific statement from the Indian Heart Rhythm Society

An analysis of the time relations of electrocardiograms

Die Systolendauer im Elektrokardiogramm bei normalen Menschen und bei Herzkranken

Bazett's QT correction reviewed. Evidence that a linear QT correction for heart is better

An improved method for adjusting the QT interval for heart rate (the Framingham Heart Study) The American journal of cardiology

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Assessment of prolonged QT and JT intervals in ventricular conduction defects

The normal duilration of the Q-T interval

Jr The duration of the QT interval as a function of heart rate: a derivation based on physical principles and a comparison to measured values

The duration of systole in an electrocardiogram in normal humans and in patients with heart disease

Diagnostic Criteria for the Long QT Syndrome An Update