What is ischemic heart disease?
Ischemic heart disease refers to a group of related conditions resulting from myocardial ischemia. Myocardial ischemia occurs when there is an imbalance between the oxygen supply (through blood perfusion) to the heart muscle and the heart’s demand for oxygenated blood.
How common is ischemic heart disease?
Ischemic heart disease is the leading cause of mortality worldwide, responsible for around 12% of global deaths. It is more commonly seen in men than women and typically manifests after the age of 50. However, it can begin earlier in life, with its prevalence increasing as people age.
What are the risk factors for ischemic heart disease?
The risk factors can be divided into two broad categories:
Traditional Risk Factors:
Non-modifiable factors:
Male sex
Increasing age
Family history of premature ischemic heart disease
Modifiable factors:
Cigarette smoking
Hypertension
Diabetes mellitus
Hypercholesterolemia
Emerging Risk Factors:
Metabolic causes:
Obesity
Inactivity or sedentary lifestyle
High body mass index (BMI)
Dietary causes:
High intake of saturated fats (e.g., butter, animal fats)
Excess sugar consumption
Other associations:
Chronic inflammatory diseases (e.g., psoriasis, chronic kidney disease, HIV/AIDS)
Non-alcoholic fatty liver disease (NAFLD)
Prolonged screen time (TV or smartphones)
Psychosocial stress, urban living, work-related stress, sleep deprivation, and prolonged sitting
What causes myocardial ischemia in ischemic heart disease?
The primary cause is obstruction of blood flow in the coronary arteries due to atherosclerosis. Over 90% of cases are attributed to atherosclerotic plaques in the epicardial coronary arteries.
Other less common causes include:
Emboli in the coronary arteries
Inflammation of myocardial vessels
Coronary artery spasms
What is the role of atherosclerosis in ischemic heart disease?
Atherosclerosis, which involves the buildup of plaques in the arterial walls, can begin during childhood or adolescence. However, its clinical manifestation as ischemic heart disease typically occurs much later in life.
Progressive narrowing of coronary arteries due to atherosclerosis reduces blood supply, leading to myocardial ischemia. When the obstruction becomes significant, it results in critical stenosis.
Critical stenosis: Obstruction of more than 70% of the vascular cross-sectional area, causing ischemia during exercise.
Severe stenosis: Obstruction of more than 90% of the vascular cross-sectional area, causing ischemia even at rest.
What are the clinical consequences of myocardial ischemia?
The consequences of myocardial ischemia include:
Angina pectoris (chest pain):
Stable angina: Occurs without significant plaque damage and is usually triggered by physical exertion.
Unstable angina: Results from acute changes in plaques, such as rupture, fissure, ulceration, or hemorrhage.
Myocardial infarction (heart attack):
Caused by sudden obstruction of coronary arteries due to plaque changes, leading to cardiac tissue death.
Sudden cardiac death:
Caused by fatal arrhythmias resulting from myocardial ischemia.
Chronic ischemic heart disease:
Develops over time and is often accompanied by heart failure.
Which coronary arteries are commonly involved in ischemic heart disease?
The epicardial coronary arteries most commonly involved are:
Left anterior descending artery (LAD)
Left circumflex artery
Right coronary artery
What happens in acute plaque changes, and how do they contribute to ischemic heart disease?
Acute plaque changes, such as rupture, fissure, ulceration, or hemorrhage within the plaque, can lead to sudden obstruction or occlusion of coronary arteries. This can result in conditions like:
Unstable angina
Acute myocardial infarction
Sudden cardiac death
How does myocardial ischemia affect the heart cells?
When myocardial ischemia occurs, the lack of oxygen leads to:
Reduced ATP production
Decreased availability of nutrients
Impaired removal of metabolic waste products
This eventually causes cell injury, which manifests as chest pain, necrosis of cardiac tissue (infarction), or arrhythmias.
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