Myocardial Infarction
MYOCARDIAL INFARCTION
This term refers to the death of a certain segment of the heart muscle (myocardium), usually the result of a focal complete blockage in one of the main coronary arteries or a branch thereof.
The main cause of myocardial infarction is atherosclerosis in the coronary arteries. Refer to figure 70 for the pathogenesis of myocardial infarction. This event results in impaired contractility of the heart muscle within seconds, and is initially restricted to the affected segment.
The myocardial ischemia or infarction begins in the endocardium (the inner lining of the heart) and spreads to the epicardium (the outer lining of the heart). Irreversible heart damage will occur if the blockage is complete for at least 15-20 minutes. …show more content…
However, in a recent study two fifths of the patients with acute myocardial infarction had angiographic evidence of multiple complex coronary plaques, which were associated with a less favorable in-hospital course. The presence of these plaques with complex morphologic features is the angiographic hallmark of unstable coronary syndromes and correlates with pathologic plaque and thrombus.
Other causes of MI
Carbon monoxide poisoning is one of the occupational toxic risk factors for not only myocardial infarction but also cardiomyopathy.
Firefighters '"chronic" occupational exposure to carbon monoxide results in increased blood concentrations of carboxyhemoglobin, even in nonsmoking firefighters; changes in cardiac serum enzyme levels in one study suggested myocardial (heart) damage.
Increase symptoms in patients known to have coronary disease occur with exposure to carbon monoxide. Carbon monoxide has an affinity for hemoglobin that is much greater than that of oxygen. The cardiac effects are the results of hypoxia. These effects are determined by the degree of carbon monoxide exposure, the hemoglobin concentration, and the presence or absence of coronary or myocardial disease.
A decrease in exercise performance occurs even in normal individuals with low level exposure. Patients with angina pectoris have a greater reduction in exercise tolerance. …show more content…
Myocardial infarctions are divided into two types, according to their severity. A NSTEMI is the less severe type.
In a NSTEMI, the blood clot only partly occludes the artery, and as a result only a portion of the heart muscle being supplied by the affected artery dies.
In contrast to the more severe form of heart attack (the STEMI), the NSTEMI does not produce characteristic elevation in the "ST segment" portion of the ECG. (ST segment elevation indicates that a relatively large amount of heart muscle damage is occurring, because the coronary artery is totally blocked). This means that in a NSTEMI, the artery is only partially blocked.
A common problem when a patient has an acute coronary syndrome without ST segment elevation is deciding whether an actual heart attack is occurring or instead whether the patient is simply having unstable angina. Measuring cardiac enzymes, which reflect heart muscle damage, is an important tool in making this distinction.
Laboratory Diagnosis of Myocardial Infarction
This term refers to the death of a certain segment of the heart muscle (myocardium), usually the result of a focal complete blockage in one of the main coronary arteries or a branch thereof.
The main cause of myocardial infarction is atherosclerosis in the coronary arteries. Refer to figure 70 for the pathogenesis of myocardial infarction. This event results in impaired contractility of the heart muscle within seconds, and is initially restricted to the affected segment.
The myocardial ischemia or infarction begins in the endocardium (the inner lining of the heart) and spreads to the epicardium (the outer lining of the heart). Irreversible heart damage will occur if the blockage is complete for at least 15-20 minutes. …show more content…
However, in a recent study two fifths of the patients with acute myocardial infarction had angiographic evidence of multiple complex coronary plaques, which were associated with a less favorable in-hospital course. The presence of these plaques with complex morphologic features is the angiographic hallmark of unstable coronary syndromes and correlates with pathologic plaque and thrombus.
Other causes of MI
Carbon monoxide poisoning is one of the occupational toxic risk factors for not only myocardial infarction but also cardiomyopathy.
Firefighters '"chronic" occupational exposure to carbon monoxide results in increased blood concentrations of carboxyhemoglobin, even in nonsmoking firefighters; changes in cardiac serum enzyme levels in one study suggested myocardial (heart) damage.
Increase symptoms in patients known to have coronary disease occur with exposure to carbon monoxide. Carbon monoxide has an affinity for hemoglobin that is much greater than that of oxygen. The cardiac effects are the results of hypoxia. These effects are determined by the degree of carbon monoxide exposure, the hemoglobin concentration, and the presence or absence of coronary or myocardial disease.
A decrease in exercise performance occurs even in normal individuals with low level exposure. Patients with angina pectoris have a greater reduction in exercise tolerance. …show more content…
Myocardial infarctions are divided into two types, according to their severity. A NSTEMI is the less severe type.
In a NSTEMI, the blood clot only partly occludes the artery, and as a result only a portion of the heart muscle being supplied by the affected artery dies.
In contrast to the more severe form of heart attack (the STEMI), the NSTEMI does not produce characteristic elevation in the "ST segment" portion of the ECG. (ST segment elevation indicates that a relatively large amount of heart muscle damage is occurring, because the coronary artery is totally blocked). This means that in a NSTEMI, the artery is only partially blocked.
A common problem when a patient has an acute coronary syndrome without ST segment elevation is deciding whether an actual heart attack is occurring or instead whether the patient is simply having unstable angina. Measuring cardiac enzymes, which reflect heart muscle damage, is an important tool in making this distinction.
Laboratory Diagnosis of Myocardial Infarction