"But its caused heart failure already ? I'd suspect those people were already failing heart."

 Our cardiology team suggests otherwise.  It has been known that people without indications of heart disease have side-effects that effect the heart after taking a medication.  HCQ is one of those drugs.

 It's like saying people have amnesia type symptoms because they already had failing memory.  This may be true, but the percentage increases at an accelerated rate if HCQ is taken.

 So yes maybe the heart was already failing, which when we think about it is true for every human at some scale, so in theory all heart related deaths are attributed to a failing heart.  The question is at what point is a medication causing it to be faster than normal.

HCQ as with any drug may be dangerous when other parameters are placed into the treatment scope.  

 Drug A is used to treat arthritis and has side effects, one is nausea, one is heart failure. 1% of people prescribed have heart failure.

 Drug A is now used as a treatment for SARS and has side effects, one is nausea, one is heart failure.  10% of people prescribed have heart failure.

 Drug A is dangerous to people that have SARS, but safe for people who do not.  This is no different than drugs that are safe to take, unless pregnant, or have hypoglycemia, etc. which is why those warnings exist.

 This is why we should be thankful for people that volunteer for clinical trials.

 Depends on the pay.