Heart & Cardiology/Heart Attack Question

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QUESTION: Hi Dr Ahmed,

If i understand correctly, a heart attack occurs when arteries get blocked or when plaque becomes dislodged and breaks free...Which event happens more - blocked arteries or ruptured plaque?...Also, is it common for people who have say 130-150 total chlosterol and 75 LDL to have a ruptured plaque event?.....Thanks

ANSWER: Hi, http://blog.myheart.net/2014/06/08/heart-blockage-explained-with-pictures/, http://blog.myheart.net/2014/03/17/do-i-need-a-stress-test/, https://www.youtube.com/watch?v=fjruImr3IgE

There are several different types of heart attacks, however the one that you are likely referring to is the heart attack that is caused by an acute blockage of a vessel. Such heart attacks occur when an unstable area in an artery wall bursts and leads to clot formation. The clot that forms, leads to critical blockage of the artery, cutting off the blood supply beyond that point. The heart muscle supplied by that artery now no longer gets the blood it needs, and dies, typically within a matter of hours. This is why a heart attack is the most feared complication of coronary artery disease.

The age old question has been does the unstable area that bursts occur in an area with already large blockage, or in an area with only mild blockage. It used to be assumed that it occurred in people with already 60-70% blockages or more, however over time we realized that actually it is the other areas with not as severe blockage that are unstable and burst often. Even in those with 80% blockage, it may well be the 10% blockage area that is unstable and bursts. It is for this reason as mentioned in the articles above that a normal stress test without blockage doesn't necessarily rule out a heart attack occurring in the future. Therefore we treat risk factors for coronary disease aggressively in those with even mild blockages as this indicates the disease process is already there.

As for cholesterol, we know the following, that in those with high cholesterol, there is increased risk of events. The higher the LDL the higher the risk, although the absolute risk of having a heart attack is still relatively low, meaning that not everyone with increased cholesterol is going to get a heart attack, so i wouldn't use the word common. Current guidelines have a target LDL range of around 130 for those without a prior history of cardiac disease. However research done a few years ago demonstrated that up to 70% of those admitted with a heart attack had LDL below this level. Half had LDL lower than 100, and 20% had lower than 70, which are the targets for those at moderate and high risk respectively. This shows that having a low cholesterol does not necessarily negate the risk of an event. Its not entirely clear whether aggressive cholesterol treatment of those and moderate to low risk would change this so its difficult to recommend that routinely. I would say that the single best thing anyone could to is address all risk factors such as diet, exercise, bp, lipids etc. in order to effectively reduce their overall risk.

Hope that was helpful,

---------- FOLLOW-UP ----------

QUESTION: Hi Dr Ahmed,

Thank you for your reply...One follow up ?...I was looking at the results from a cardiac MRI from couple years ago...Under the page that showed the Rest Function and Viability for the LAD, RCA, & LCX - there were a total of 17 catagories (basal ant, basal inf Sept, Apical Inf, etc) and all had Normal by each one of them....Does that mean there is normal blood flow (CMRI's don't look at coronary arteries correct?)..What does all those 17 catagories refer to?....Thanks

Answer
Hi,

These 17 categories are segments that the heart is divided up in to that allow standardization in reporting across various modalities. The various arteries are typically associated with given segments. For example if segments 1,2,7,8,13,14 and 17 were affected, this would mean the LAD was affected. If you do a quick internet search for the 17 segment heart model I'm sure you could see it visually demonstrated in images. Yours were all normal, no none of the segments in any of the artery areas were abnormal. So a pretty good result! The normal refers to normal wall motion which is indicative of normal perfusion and thus adequate blood supply.

Hope that was helpful,  

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Mustafa Ahmed MD

Expertise

Cardiology, Interventional Cardiology, Cardiac Surgery, Hypertension, Pulmonary Embolism, Structural and Valve Disease

Experience

Board Certification Internal Medicine and Cardiology Interventional and Structural Cardiology

Organizations
http://blog.myheart.net

Publications
Multiple Publications In High Quality Peer Reviewed Journals. Internationally Recognized.

Education/Credentials
MD from The Royal Victoria University of Manchester, England Medicine, Cardiology, Interventional Cardiology, Research Training - University of Alabama

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