Acute Coronary Syndrome (ACS) describes conditions where there is a sudden reduction in blood flow to the heart. This can cause heart muscle damage or tissue death. ACS is a medical emergency requiring immediate attention to restore proper heart function.
The Immediate Mechanism
The direct cause of ACS involves atherosclerosis, a progressive condition where fatty deposits (plaque) accumulate within the coronary arteries. These arteries supply blood to the heart muscle. Over time, plaques harden, narrowing the arteries and restricting blood flow.
ACS often occurs when a plaque ruptures, exposing its inner material. Platelets rush to the site, forming a blood clot (thrombus) that can block the artery. This obstruction causes the heart muscle to lack oxygen. This lack, known as ischemia, impairs heart function and leads to ACS symptoms and damage.
Major Contributing Factors
Long-term conditions and lifestyle choices increase the risk of atherosclerosis, the underlying cause of most ACS cases.
High blood pressure (hypertension) damages artery walls, making them susceptible to plaque formation. This accelerates atherosclerosis and increases plaque vulnerability to rupture.
Elevated cholesterol, especially high low-density lipoprotein (LDL), contributes to plaque buildup. LDL accumulates in arterial walls, leading to inflammation and fatty streaks, the earliest stage of atherosclerosis.
Diabetes promotes atherosclerosis. Chronic high blood sugar damages blood vessels and hardens arteries. Often accompanied by dyslipidemia and inflammation, diabetes makes individuals two to four times more likely to develop heart disease.
Smoking is a modifiable risk factor for atherosclerosis and ACS. Chemicals in cigarette smoke damage blood vessel lining, causing endothelial dysfunction and chronic inflammation. This increases plaque formation and makes existing plaques prone to rupture, contributing to blood clot formation.
Obesity and a sedentary lifestyle increase ACS risk. Excess weight often leads to high blood pressure, high cholesterol, and diabetes, all contributing to atherosclerosis. Physical inactivity is independently associated with increased cardiovascular disease risk, reducing blood flow and negatively impacting vascular function.
Age is a non-modifiable risk factor; men over 45 and women over 55 have a higher heart attack risk. A family history of early-onset coronary artery disease (before age 55 for males, 65 for females) also increases ACS predisposition. This suggests a genetic component accelerating atherosclerosis at younger ages.
Other Influencing Elements
While atherosclerosis and plaque rupture are the most common causes, other factors can also lead to ACS.
Coronary artery spasm (Prinzmetal’s angina) involves temporary narrowing of coronary arteries due to sudden muscle contraction. These spasms restrict blood flow to the heart, causing chest pain and potentially a heart attack, often at rest.
Severe emotional or physical stress can trigger ACS, sometimes without significant blockages (Takotsubo syndrome). This relates to a sudden surge of stress hormones that temporarily impair heart function. Illicit drug use, particularly stimulants like cocaine, can induce ACS by causing coronary artery spasms, increasing heart rate and blood pressure, and accelerating atherosclerosis.
Rare inflammatory conditions can affect coronary arteries, contributing to ACS. Systemic inflammatory processes can directly contribute to plaque instability and rupture, increasing the risk of acute coronary events.