In the simpler, unenlightened world of the past, a heart attack was just a heart attack. It was a serious problem caused by a blockage in one of the coronary arteries. The blockage was due to the accumulation platelets, fibrin, cholesterol and calcium that formed a plaque attached to the inner surface of the coronary artery. Over time, that plaque had increased in size to the point of completely blocking the flow of blood, and thus oxygen, to the heart muscle, the myocardium.
The lack of oxygen to the heart muscle caused the heart to scream out with pain in the chest, neck, shoulder, and left arm. The lack of oxygen to the heart muscle also caused the muscle to die in the section of the heart supplied by the blocked artery causing dramatic changes in the appearance of the person’s electrocardiogram. The damaged heart muscle cells then, also, released chemical elements into the blood stream that when measured by laboratory assay, confirmed a heart attack, or myocardial infarction, had occurred.
Infarction of the myocardium then caused instability in the heart resulting in very serious arrhythmias (irregular heart beats) that were potentially fatal— ventricular tachycardia, ventricular fibrillation, and even cardiac arrest. Infarction also weakened the pumping function of the heart causing blood to accumulate in the lungs and causing extreme weakness and/or shortness of breath. The whole situation was potentially life-threatening, but it was straightforward and easy to explain and understand.
Then came the 21st century with its highly sophisticated technological advancements, and doctors learned more and more about the heart and the serious things that can happen to it. Echocardiography, cardiac CT, MRI, and PET scanning, stress testing, catheterization and angiography, and electrophysiology studies have provided doctors with detailed information that has enabled new, more focused, more effective treatments. It has also brought about a broader classification of myocardial infarction.
In 2018, the American College of Cardiology, the European Society of Cardiology, and the World Heart Federation published updated definitions of heart attacks, or myocardial infarctions. Infarction is the term applied to the injury or death of the heart muscle, the myocardium. Through diligent study, the three organizations listed above determined there are five subtypes of myocardial infarctions. I’ve already written about type I heart attacks, but there are four additional types. Of those, only type II has significance for this article.
Type I is the classic MI that occurs from a blocked coronary. Type II heart attacks occur when factors other than arteriosclerosis of the coronary artery occur and the myocardium’s need for oxygen exceeds the artery’s ability to supply that need. Arterial spasm, anemia (with low oxygen saturation), embolism, low blood pressure, and low blood oxygen level stress the myocardium to the point of injury/infarction. Types III, IV, and V occur soon after an angioplasty or a coronary bypass procedure, more than 48 hours after a coronary artery procedure, or 30 days after a stent. For practical clinical purposes, Types I and II make up the majority of heart attacks. Differentiating between the two is important because they are treated differently. Type I often requires angioplasty and stenting while Type II is treated by correcting the underlying cause.
Cardiology continues to evolve and knowledge continues to expand. The whole philosophy of treating coronary disease has gone from 3 weeks of bed rest, arrhythmia control, and prayer to the aggressive assault of the blocked artery to remove the obstruction and re-establish blood flow to preserve as much myocardium as possible. Revascularization of the heart is the goal of treatment and preventing heart muscle damage is the hoped-for outcome. This aggressive approach has been very successful.
Treatments like sublingual nitroglycerin for chest pain and long-acting nitrates for improving cardiac function are remnants of the past. Today’s angioplasty, stenting, and bypass grafting have improved the quality and longevity of life for millions of people.
References: Spiriano P. Type 1 vs. Type 2 MI: New Clues to sharpen Diagnosis Medscape 2025 October 1.
google.com 4th Universal Definition of Myocardial Infarction
