I just read up about heart attacks caused by cholesterol. But what happens in the cases where a heart attack is caused by something else? Like drugs or chemicals? Symptoms, damage, how do these differ from 'regular' heart attacks?
Symptoms and damage vary in general, no matter what the actual cause of the heart attack is. In some cases, heart attacks can even be silent (goes unnoticed). Noteworthy, if one has a second heart attack the symptom(s) may not be the same as the first one.
During a heart attack (myocardial infarction, MI, actual death or necrosis of heart muscle cells/tissue), the heart's electrical conduction goes through a series of changes/abnormalities (as seen with an electrocardiogram, ECG/EKG).
Elevation of the ST segment is the hallmark abnormality of an acute MI. It occurs when the heart muscle (myocardium) is being injured by a lack of blood flow and oxygen and is also called "current of injury".
STEMI is an ST-elevation myocardial infarction, also referred to as a Q wave myocardial infarction and NSTEMI is a non-ST-elevation myocardial infarction, also referred to as a non-Q wave myocardial infarction.
STEMI or Q wave MI usually corresponds to a transmural MI, affecting the entire/full thickness of the heart muscle, the worst type (has a substantially higher mortality rate.
A NSTEMI usually corresponds to non-transmural or a subendocardial MI, less damaging than a Q wave/STEMI, as the heart muscle just under the sensitive inner lining of the heart is affected (lower mortality rate, though this type of incomplete MI poses a high risk for reinfarction, or completing the infarction).
WHAT HAPPENS AFTER A HEART ATTACK (and down the road) mainly depends on what specific area(s) of the heart muscle (myocardium) were damaged (infarcted), size and depth of the damage, and if there has been any previous damage or other serious/severe heart condition(s) exist.
Cell/tissue death does not occur immediately (once the artery is 100% blocked, with no, or insufficient coronary artery collateral circulation). It takes several minutes to start the injury process, which then continues on (evolves, in phases) for several hours, unless the artery is opened up. restoring blood flow. Prompt treatment can limit the damage, but the damage that has been already done is permanent/irreversible (though some ongoing clinical trials are showing promise for making heart damage reversible).
After a completed heart attack, the body heals the heart damage caused by it by forming scar tissue. This healing process is usually complete in 4-8 weeks.
Looking at the most known causes of a heart attack (myocardial infarction, MI) the most common is now recognized worldwide as vulnerable plaque (VP), a soft and potentially deadly type of plaque.
VP is essentially hidden (can't be seen with invasive X-ray angiography, heart catheterization) arterial landmines/time bombs, 0% blockages (though unequivocal atherosclerosis) with the potential to kill, when rupturing and triggering off a blood clot (thrombus).
Following VP is the tight (stenotic) atherosclerotic plaque blockage (which typically but not always causes symptoms such as angina pectoris, and dyspnea, seemingly increasing in those in their late 30s to early 40s) eventually going to 100% occlusion with or without a blood clot.
Other causes (some less common/uncommon to rare to very/extremely rare) of heart attack may/can include coronary artery spasm (CAS), a transient or brief constriction or transient or brief closure of a coronary artery, occurring typically, but not 100% always at rest, and has various causes which includes cigarette smoking, prescription and illegal drugs (e.g., cocaine).
Spontaneous coronary artery dissection (SCAD, a tear or rip), coronary artery aneurysm (CAA, an area of ballooning out), coronary artery ectasia (CAE, an abnormal enlargement of the coronary artery), myocardial bridging (a part of a coronary artery tunneling under heart muscle), pathogen-induced (PI), and penetrating injury to the heart, e.g., a projectile such as a nail from a nail gun, which made the national news several times way back in 2003.