Heart attacks, medically termed as myocardial infarctions (MI), are severe medical emergencies that require immediate attention. This condition, characterized by the death of heart muscle due to prolonged ischemia, can have devastating consequences if not promptly addressed. In this section, we'll dive into the pathogenesis, diagnosis, treatment, and complications associated with myocardial infarction, providing a comprehensive overview of this critical condition.
Myocardial Infarctions
Pathogenesis of Myocardial Infarction
Myocardial infarction primarily occurs when the heart muscle, or myocardium, becomes ischemic for an extended period, typically around 30-40 minutes, leading to tissue death. This usually happens when a thrombus (blood clot) forms over a coronary artery plaque, causing complete or near-complete occlusion of the vessel. This blockage prevents the heart from receiving the oxygen-rich blood it needs, resulting in a heart attack.
​The most affected region is usually the left ventricle due to its high demand for blood flow. The size and location of the infarct depend on which coronary artery is blocked. Blockages in the left anterior descending artery result in anterior wall infarcts, obstruction in the left circumflex artery result in lateral left ventricle wall infarcts, and occlusions in the right coronary artery lead to posterior wall infarcts.
Morphologically, infarcts can be classified as transmural, affecting the full thickness of the heart wall, or subendocardial, involving only the inner layers. Unfortunately, the heart muscle does not regenerate; hence, infarcted muscle is permanently lost, leading to a reliance on the remaining healthy muscle for heart function.
Diagnosis and Treatment of Myocardial Infarction
Early diagnosis and treatment of MI are paramount. Symptoms such as prolonged chest pain, often radiating to the jaw or left arm, accompanied by nausea and sweating, are clinical indicators. Diagnostic measures include electrocardiogram (ECG) changes that suggest heart muscle injury and elevated levels of cardiac enzymes like troponins and creatine kinase, signaling heart muscle cell damage.
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Treatment strategies focus on restoring blood flow to the affected area as quickly as possible. Thrombolytic drugs, known as "clot-busters," are highly effective if administered early. Other treatments include percutaneous transluminal coronary angioplasty (PTCA) and coronary artery bypass surgery, which may also be employed to treat unstable angina and prevent infarction.
Complications of Myocardial Infarction
Complications following an MI can be early or late and range from manageable to life-threatening.
Early Complications:
Dysrhythmias: Infarcted muscle can disrupt the heart's electrical rhythm, potentially leading to serious conditions that may require drug therapy or pacemakers.
Congestive Heart Failure/Cardiogenic Shock: If a significant portion of the heart muscle is damaged, the remaining muscle may not suffice, leading to blood congestion in the lungs or inadequate blood flow to the body.
Ventricular Rupture: The heart wall may rupture in the infarcted zone, causing acute hemorrhage and potentially fatal cardiac tamponade.
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Ventricular Aneurysm: A large scar from a transmural infarct may weaken and bulge, forming an aneurysm.
Chronic Congestive Heart Failure: Can become a long-term condition following significant heart muscle damage.
Pericarditis: Inflammation of the heart's surface can occur as a early or late complication.
Late Complications:
