Cardiac arrhythmia's are a known side effect of HQ overdoses.
And in Brazil they were using very high doses, something like 2000 mg a day not 500 mg which is the usual dose.
In the US HCQ is used for some diseases like Lupus. I took it 40 years ago when I worked in Africa but even then there was resistance and I got malaria.
In the 1990s one group supporting suicide recommended it as a painless way to kill oneself because there was no known treatment. Then some docs in Paris found an antidote and the death pushers stopped recommending it.
Back then,this group was telling people that if they couldn't find the pills to use fishtank cleaner, when that story came out I wondered if it was a case of murder.
In the paper cited below the authors studied 31 randomized controlled studies with HCQ (1996 - 2022), 9 studies using Chloroquine and 1 study using both HCQ and CQ. There were no reports on torsades de pointes or sudden cardiac death. Risk of severe cardiac events compared wit control (RR) was 0,90 (ie nominally less risk with HCQ/CQ) but no statistical significance.
Despite being listed as QT-prolonging meds, HCQ-CQ did not increase the risk of major adverse cardiac events.
Hydroxychloroquine-Chloroquine, QT-Prolongation, and Major Adverse Cardiac Events: A Meta-analysis and Scoping Review