Heart attack and the basics

All opinions expressed here are those of the author and not of the employer. Information provided here is for medical education only. It is not intended as and does not substitute for medical advice.

Podcast audio: heart attack and a simple description of cardiac catheterization

Refer to the basic blood supply description in the anatomy blog. In brief, there are three main blood vessels or arteries which supply the heart. Left anterior descending artery, notoriously called the ‘widow-maker’ is the largest and supplies the front of the heart. The other two arteries – left circumflex and the right coronary arteries, surround the heart in the middle and supply the left, right and back sides of the heart (figure 1).

Figure 1: Blood supply to the heart

All three arteries divide into various branches, getting smaller as they go further in their course. These three arteries are assigned the responsibility of supplying the entire real estate of the heart. 

Cholesterol plaques may develop within the walls of these arteries. Plaques are formed by certain cells in the blood called macrophages ingesting (or eating) fat globules. This is one of the way body gets rid of excess fat through scavenging. Some arteries are especially prone to have these cells ‘settle’ in the walls of the arteries, heart arteries being one of them. Over time these cells may die and release the fat to the vicinity creating a cholesterol filled plaque.

This could be an ongoing process which may slowly obstruct the flow downstream. On occasions the plaque may rupture and expose its innards to the blood. The exposed plaque acts as a magnet for platelets and other clotting agents and starts forming a clot. This can result in a sudden and sometimes complete obstruction of the artery. The heart muscles dependent on the artery for nutrition and oxygen supply are suddenly starved (figure 2). This is one of the most common causes of a heart attack or ‘acute myocardial infarction’. 

Figure 2: Sudden obstruction of the artery results in a starving and dying muscle zone in its supply area.

Risk factors: 

Plaque

formation is accelerated by certain risk factors such as poorly

controlled hypertension, diabetes, high cholesterol levels, old age,

male gender, obesity, smoking, family history

to name a few. Arterial plaques anywhere in the body is a risk factor

for plaques in the heart arteries. Exercise primes the heart to function

in extreme conditions, makes favorable changes to the heart, open up new channels. Just like long-distance marathon runners learn

to optimize their movements and conserve energy for the long run. Lack

of exercise does the opposite and the heart does not need to optimize

anymore. 

Consequence of a heart attack: 

If

the obstruction is further up in the artery, the amount of heart

muscles affected may be massive. Starved muscles behave stunned. They

stop contracting, sometimes balloon out, may even rupture; depending

on the extent of damage. They are also prone to sudden and persistent

electrical activation which could overwhelm the entire electrical system

of the heart, short-circuiting it. Heart valves with attachments to the

affected walls may malfunction and start leaking. In short, the