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


This is a statement from the Indian Heart Rhythm Society (IHRS) summarizing the cardiovascular effects of hydroxychloroquine. The primary effects discussed are QT interval prolongation (heart taking too long for electrical recharge) and potentially fatal arrhythmia (irregular heartbeat). This paper also addresses methods of identifying high risk groups and the monitoring necessary to prevent cardiac related death. 



Hydroxychloroquine is often used for “autoimmune disorders, and related inflammatory and dermatological conditions.” The drug is a safer (according to clinical studies) version of chloroquine, the difference being an additional hydroxyl (-OH) group. It effectively inhibits SARS-CoV2 binding by raising intravesicular pH, inhibiting lysosomal activity, and changing antigen processing. Despite its potential for fighting SARS-CoV2, the medication can cause QT prolongation in certain patients (especially when combined with other medications such as azithromycin). This paper aims to address and help prevent such risks. 

Risks and Prevention

Using a 12-lead ECG, or using a rhythm strip and comparing to RR interval (comparison of spikes on an electrocardiogram reading), patients should have baseline measurements taken for their QT interval. Due to personal protective equipment shortages and other logistical issues of taking COVID patient ECG readings repeatedly, some alternatives are available. These include continuous rhythm monitoring systems or apps and devices available to the public (such as Kardia Mobile). 

Based on the above measurements, potential hydroxychloroquine recipients should be categorized into risk groups. Low-risk: normal QT interval, moderate-risk: QT prolongation of up to 500ms, and high-risk: QT prolongation greater than 500ms. Low-risk groups can be given hydroxychloroquine without further risk analysis. Moderate-risk individuals can be given hydroxychloroquine with caution and with attention being paid to removable risks like improper electrolyte levels in the blood. High-risk patients should not be given hydroxychloroquine or should be monitored extremely closely if they are taking it. ECG readings should be taken 2-4 hours after the first dose in high risk patients and then again in two to four days. 

Dosage for prophylactic use of hydroxychloroquine should be: 

-400mg twice a day on day one and 400mg once a week for the next seven weeks for asymptomatic healthcare workers

-400mg twice a day on day one and 400mg once a week for the next three weeks for asymptomatic household contacts of lab confirmed COVID patients

The drug is not recommended for children under 15 years of age. 


The Indian Heart Rhythm Society “strongly discourages it’s [hydroxychloroquine] use for the general public without medical supervision…” With this being said, shortage of equipment and logistical issues in preventing transmission to healthcare workers are acknowledged in the paper. Mobile applications and other self-monitoring tools are strongly encouraged to overcome resource limitations.