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A question I often get. Why Lupus patients that have taken Hydroxychloroquine for years have no side effects whereas severe adverse cardiac side effects are described #COVID19 patients under hydroxychloroquine treatment? Let's have a closer look
Let's start with #COVID19. Does #COVID19 causes cardiac effects? The answer is yes from 2 published surveys from Wuhan hospitals. First one reports on 416 hospitalized patients -> 19.7% with myocardial injury + ⬆️cardiac troponin & high mortality rate 51% jamanetwork.com/journals/jamac…
The second paper shows similar observation on 187 hospitalized patients -> 27% had cardiac injury with again elevation of cardiac troponin and increase mortality rate at 59%. In short #COVID19 leads to significant cardiac injury but these are severe cases jamanetwork.com/journals/jamac…
More relevant to milder #COVID19 cases, A recent cohort study describes the incidence of ECG abnormalities and myocarditis (heart inflammation) on 84 patients -> 16% had ECG abnormalities and 5% with clinical diagnosis of myocarditis. medrxiv.org/content/10.110…
In short, #COVID19 gives either myocarditis or cardiac injuries at a prevalence of 4 to 15% dependent on the severity of the infection.. Of course we do need large scale studies to have a better idea of the prevalence of #COVID19 cardiac effects.

What about Hydroxychloroquine?
It is known for decade that Hydroxychloroquine (HCQ) gives cardiac side effects such as prolonged QT or torsades de pointes. Many lupus patients have takeen HCQ (usually 200 mg/day) for years and very few cardiac side effects have been reported. There are 2 explanations for this
Firstly HCQ cardiac toxicity is dose dependent. Lupus patients take usually a low dose (200 mg/day) whereas the protocols for #COVID19 oscillate between 400 mg to 800 mg/day for 7 days. increase dose significantly logically increases the risk of cardiac toxicity
Secondly Cardia side effects from auto immune patients taking long term HCQ are often under reported. A recent systematic review concluded that of cardiac side effects are rare but non reversible. However, caution, large scale studies are warranted
link.springer.com/article/10.100…
What about now the association #COVID19 and Hydroxychloroquine? While we have no large scale studies yet, one study to date showed that in this cohort of 84 hospitalized patients, 11% #COVID19 treated patients with HCQ developed severe arrhythmia
Additionally, HCQ is associated with Azithromycin to treat #COVID19 infection. To complicate more the matter, Azithromycin gives also cardiac side effects such as QT prolongation ncbi.nlm.nih.gov/pmc/articles/P…
Therefore the cocktail Hydroxychloroquine in high dose + Azithromycin on #COVID19 patient is explosive for the heart and it is therefore not surprising to see increase reporting of severe adverse events due to HCQ treatment in #COVID19 patients

As always in medicine, there is a balance benefit/risk analysis providing a specific treatment for a disease. This is valid for Hydroxychloroquine, Azithromycin or all others potential treatments or repurposed drugs against #COVID19
Final words on this. 1/ There is currently no miracle drugs against #COVID19 2/ Most importantly preventive measure such as #Social_Distancing, #WashYourHands and a lot of tests will be by large the most effective treatment against #COVID19
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