What is a heart attack?
A heart attack (also known as a myocardial infarction) is the death of heart muscle from the sudden blockage of a coronary artery by a blood clot. Coronary arteries are blood vessels that supply the heart muscle with blood and oxygen. Blockage of a coronary artery deprives the heart muscle of blood and oxygen, causing injury to the heart muscle. Injury to the heart muscle causes chest pain and chest pressure sensation. If blood flow is not restored to the heart muscle within 20 to 40 minutes, irreversible death of the heart muscle will begin to occur. Muscle continues to die for six to eight hours at which time the heart attack usually is “complete.” The dead heart muscle is eventually replaced by scar tissue.
One cannot overemphasize the importance of seeking prompt medical attention in the presence of symptoms that suggest a heart attack. Early diagnosis and treatment saves lives, and delays in reaching medical assistance can be fatal. A delay in treatment can lead to permanently reduced function of the heart due to more extensive damage to the heart muscle. Death also may occur as a result of the sudden onset of arrhythmias such as ventricular fibrillation.
Although chest pain or pressure is the most common symptom of a heart attack, heart attack victims may experience a variety of symptoms including:
i. Pain, fullness, and/or squeezing sensation of the chest
ii. Jaw pain, toothache, headache
iii. Difficulty in taking breath
iv. Epigastric (upper middle abdomen) discomfort
vi. Indigestion, Heartburn
vii. Arm pain (more commonly the left arm, but may be either arm)
viii. Upper back pain
ix. General malaise (vague feeling of illness)
x. No symptoms (Approximately one quarter of all heart attacks are silent, without chest pain or new symptoms. Silent heart attacks are especially common among patients with diabetes.
Early detection of the risk factors associated with the metabolic syndrome is needed for institution of appropriate primary prevention measures in patients at risk for diabetes.
Clinical evidence of insulin resistance includes:
i. Abdominal obesity (or borderline abdominal obesity),
ii. High-normal blood pressure (or mild hypertension),
iii. High-normal triglycerides (150 to 250 mg/dL),
iv. Reduced HDL cholesterol (<40 mg/dL in men; <50 mg/dL in women),
v. Borderline high-risk LDL cholesterol (130 to 159 mg/dL), and in some patients, IFG Impaired Fasting Glucose(110 to 126 mg/dL).
Factors increasing risk of developing CHD in diabetic patients:
iii. Insulin resistance associated with obesity
iv. Asian origin
vi. Diabetic nephropathy (macroalbuminuria)
vii. Poor glycaemic control
Factors that increase the risk of developing atherosclerosis and heart attacks include increased blood cholesterol, high blood pressure, use of tobacco, diabetes mellitus, male gender, and a family history of coronary heart disease. While family history and male gender are genetically determined, the other risk factors can be modified through changes in lifestyle and medications.
High Blood Cholesterol (Hyperlipidemia):
A high level in cholesterol in the blood is associated with an increased risk of heart attack because cholesterol is the major component of the plaques deposited in arterial walls. Cholesterol, like oil, cannot dissolve in the blood unless it is combined with special proteins called lipoproteins. (Without combining with lipoproteins, cholesterol in the blood would turn into a solid substance.) The cholesterol in blood is either combined with lipoproteins as very low-density lipoproteins (VLDL), low-density lipoproteins (LDL) or high-density lipoproteins (HDL).
The cholesterol that is combined with low-density lipoproteins (LDL cholesterol) is the “bad” cholesterol that deposits cholesterol in arterial plaques. Thus, elevated levels of LDL cholesterol are associated with an increased risk of heart attack.
The cholesterol that is combined with HDL (HDL cholesterol) is the “good” cholesterol that removes cholesterol from arterial plaques. Thus, low levels of HDL cholesterol are associated with an increased risk of heart attacks.
Measures that lower LDL cholesterol and/or increase HDL cholesterol (losing excess weight, diets low in saturated fats, regular exercise, and medications) have been shown to lower the risk of heart attack. One important class of medications for treating elevated cholesterol levels (the statins) have actions in addition to lowering LDL cholesterol which also protect against heart attack. Most patients at “high risk” for a heart attack should be on a statin no matter what the levels of their cholesterol.
Treatment of heart attacks include:
i. Anti-platelet medications to prevent formation of blood clots in the arteries
ii. Anti-coagulant medications to prevent growth of blood clots in the arteries
iii. Coronary angiography with either (PTCA) with or without stenting to open blocked coronary arteries
iv. Clot-dissolving medications to open blocked arteries
v. Supplemental oxygen to increase the supply of oxygen to the heart’s muscle
vi. Medications to decrease the need for oxygen by the heart’s muscle
v. Medications to prevent abnormal heart rhythms
The primary goal of treatment is to quickly open the blocked artery and restore blood flow to the heart muscle, a process called reperfusion. Once the artery is open, damage to heart muscle ceases, and the patient becomes pain free. By minimizing the extent of heart muscle damage, early reperfusion preserves the pumping function of the heart. Optimal benefit is obtained if reperfusion can be established within the first four to six hours of a heart attack. Delay in establishing reperfusion can result in more widespread damage to heart muscle and a greater reduction in the ability of the heart to pump blood. Patients with hearts that are unable to pump sufficient blood develop heart failure, decreased ability to exercise, and abnormal heart rhythms. Thus, the amount of healthy heart muscle remaining after a heart attack is the most important determinant of the future quality of life and longevity.