Approach to Coronary Heart Disease Introduction Coronary artery disease is a leading cause of morbidity and mortality in Western countries. The underlying pathology is the development of atherosclerotic plaque in the intima of the coronary arteries. While in most cases, coronary atherosclerotic plaque will remain clinically silent, it can clinically manifest in a number of forms, such as stable coronary artery disease, acute coronary syndrome, heart failure, and sudden cardiac death. Clinical Manifestations of Coronary Artery Disease Stable Coronary Artery Disease In stable coronary artery disease, sometimes now referred to as chronic coronary syndrome, atherosclerotic plaque deposits in the coronary arteries lead to significant narrowing of the coronary lumen with subsequent obstruction of the coronary blood stream. This results in insufficient oxygen supply of the downstream myocardium during situations of increased demand (typically physical exercise). There is no close correlation between the anatomic degree of luminal obstruction and the extent of downstream ischemia at exercise, which depends on numerous factors. These include the severity and length of the lesion, the amount of dependent myocardium, the resistance of the microvasculature, and the amount of collateral flow from other coronary territories. Revascularization serves to treat symptoms and improve prognosis and is usually recommended when the amount of ischemic myocardium exceeds 10% of the left ventricular mass. Acute Coronary Syndromes Acute coronary syndromes have a mechanism that is different from stable coronary artery disease. Typically, the index event is the rupture (most frequently) or erosion (less frequently) of the fibrous cap of an atherosclerotic plaque. Material from within the plaque is exposed to the blood stream and leads to immediate thrombocyte aggregation so that a thrombus forms on the surface of the ruptured plaque. This thrombus can obstruct coronary blood flow, and depending on the degree of obstruction and downstream myocardial damage, the resulting clinical manifestation is either completely silent or symptomatic in the form of unstable angina, non-ST-elevation myocardial infarction, or ST-elevation myocardial infarction. Treatment is usually emergent and includes both medication to counter thrombus aggregation and mechanical interventions to restore blood flow. Heart Failure Acute coronary syndromes, including myocardial infarction, can remain clinically silent; therefore, substantial damage to the myocardium can occur without the patient’s noticing any chest pain episodes. It is possible that heart failure with severely impaired left ventricular function is the 1st clinical manifestation of coronary artery disease, and patients with newly identified heart failure need to be worked up for the presence of coronary artery obstruction. Especially when left ventricular functional impairment is regional, coronary artery disease should be suspected. Sudden Cardiac Death Sudden death is a possible 1st manifestation of coronary artery disease. The underlying event is almost uniformly arrhythmia. Acute mechanical complications, such as myocardial rupture secondary to an acute myocardial infarction, are possible but exceedingly infrequent. Arrhythmia leading to sudden death is usually ventricular fibrillation. It can either occur in the context of an acute coronary syndrome or be triggered by the sudden ischemia, or it can occur in patients with heart failure due to old, often previously unknown, myocardial infarction. The more pronounced the reduction in left ventricular function, the higher the risk of arrhythmic death. Diagnostic Strategies Stable Coronary Artery Disease Two diagnostic strategies exist for the diagnosis of stable coronary artery disease. The underlying process is the presence of coronary stenoses that lead to myocardial ischemia. Testing can aim either at identifying the ischemic myocardium under exercise or at the direct visualization of coronary artery stenoses. Since not all coronary stenoses cause ischemia, and since stenoses that do not cause ischemia do not require revascularization, the usual preferred approach in patients with suspected stable coronary artery disease is the noninvasive identification of stress-induced myocardial ischemia by an imaging-based stress test. Ischemia can be achieved with physical exercise (treadmill or bicycle exercise) or pharmacologic stress (dipyridamole or dobutamine to increase contractility and myocardial oxygen demand or adenosine to achieve maximum vasodilation and “steal” effects). Commonly used tests include single-photon emission computed tomography (SPECT) and positron emission tomography (PET) myocardial perfusion and metabolic imaging, stress echocardiography, and stress magnetic resonance (MR) imaging. Another strategy is the direct visualization of coronary anatomy, as achieved by invasive coronary angiography or noninvasively by computed tomography (CT) coronary angiography. It is limited by the fact that not all stenoses cause ischemia and, hence, require revascularization, and if a stenosis is detected, it may be difficult to determine whether it mandates treatment. Invasive coronary angiography can be combined with measurement of the fractional flow reserve (FFR), which quantifies the relationship of mean arterial blood pressure before and after the stenosis during maximum vasodilation achieved by adenosine. Currently, FFR is considered the gold standard to identify myocardial ischemia, and FFR values < 0.8 indicate that the respective lesion should be revascularized. Both testing approaches, ischemia and coronary anatomy, have certain limitations. Ischemia testing has limited sensitivity and specificity. Also, ischemia testing cannot identify coronary atherosclerotic plaque, which is nonobstructive but might have implications for the future cardiovascular event risk. Anatomic imaging, on the other hand, often identifies stenoses, and the treating physician (and patient) may feel compelled to perform revascularization, even though not all stenoses cause relevant ischemia. Additionally, invasive coronary angiography is associated with potential complications, and noninvasive coronary angiography by CT suffers from limited image quality, which, if misinterpreted, can lead to false-positive findings and unnecessary downstream testing. Hence, the testing strategy has to take into account patient characteristics, pretest likelihood, and also local expertise with the various diagnostic tests. The most frequently applied strategy encompasses initial testing for ischemia, followed, if positive, by anatomic imaging. Coronary visualization by CT, however, may be a suitable alternative to reliably rule out coronary stenoses, especially in patients who do not have a high likelihood of being diseased. Acute Coronary Syndromes Acute coronary syndromes encompass a wide spectrum from unstable angina to ST-segment elevation myocardial infarction (STEMI). In STEMI, electrocardiography is the only test performed and leads to immediate coronary catheterization. In non-ST elevation acute coronary syndromes, further testing is usually performed before a decision about invasive angiography can be made. It includes laboratory testing (troponin) complemented by echocardiography to exclude differential diagnoses (acute pulmonary embolism, aortic dissection) and assess regional as well as global left ventricular function. It may also include testing for ischemia. Coronary CT angiography plays an increasingly important role to rule out coronary artery disease, especially in patients who present with acute chest pain but have a relatively low pretest likelihood of acute coronary disease. Only gold members can continue reading. Log In or Register to continue Share this:Click to share on Twitter (Opens in new window)Click to share on Facebook (Opens in new window) Related posts: page Copyright Approach to Shunts INDEX Multimodality Approach to Cardiovascular Disorders Approach to Heart Failure Stay updated, free articles. 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Approach to Coronary Heart Disease Introduction Coronary artery disease is a leading cause of morbidity and mortality in Western countries. The underlying pathology is the development of atherosclerotic plaque in the intima of the coronary arteries. While in most cases, coronary atherosclerotic plaque will remain clinically silent, it can clinically manifest in a number of forms, such as stable coronary artery disease, acute coronary syndrome, heart failure, and sudden cardiac death. Clinical Manifestations of Coronary Artery Disease Stable Coronary Artery Disease In stable coronary artery disease, sometimes now referred to as chronic coronary syndrome, atherosclerotic plaque deposits in the coronary arteries lead to significant narrowing of the coronary lumen with subsequent obstruction of the coronary blood stream. This results in insufficient oxygen supply of the downstream myocardium during situations of increased demand (typically physical exercise). There is no close correlation between the anatomic degree of luminal obstruction and the extent of downstream ischemia at exercise, which depends on numerous factors. These include the severity and length of the lesion, the amount of dependent myocardium, the resistance of the microvasculature, and the amount of collateral flow from other coronary territories. Revascularization serves to treat symptoms and improve prognosis and is usually recommended when the amount of ischemic myocardium exceeds 10% of the left ventricular mass. Acute Coronary Syndromes Acute coronary syndromes have a mechanism that is different from stable coronary artery disease. Typically, the index event is the rupture (most frequently) or erosion (less frequently) of the fibrous cap of an atherosclerotic plaque. Material from within the plaque is exposed to the blood stream and leads to immediate thrombocyte aggregation so that a thrombus forms on the surface of the ruptured plaque. This thrombus can obstruct coronary blood flow, and depending on the degree of obstruction and downstream myocardial damage, the resulting clinical manifestation is either completely silent or symptomatic in the form of unstable angina, non-ST-elevation myocardial infarction, or ST-elevation myocardial infarction. Treatment is usually emergent and includes both medication to counter thrombus aggregation and mechanical interventions to restore blood flow. Heart Failure Acute coronary syndromes, including myocardial infarction, can remain clinically silent; therefore, substantial damage to the myocardium can occur without the patient’s noticing any chest pain episodes. It is possible that heart failure with severely impaired left ventricular function is the 1st clinical manifestation of coronary artery disease, and patients with newly identified heart failure need to be worked up for the presence of coronary artery obstruction. Especially when left ventricular functional impairment is regional, coronary artery disease should be suspected. Sudden Cardiac Death Sudden death is a possible 1st manifestation of coronary artery disease. The underlying event is almost uniformly arrhythmia. Acute mechanical complications, such as myocardial rupture secondary to an acute myocardial infarction, are possible but exceedingly infrequent. Arrhythmia leading to sudden death is usually ventricular fibrillation. It can either occur in the context of an acute coronary syndrome or be triggered by the sudden ischemia, or it can occur in patients with heart failure due to old, often previously unknown, myocardial infarction. The more pronounced the reduction in left ventricular function, the higher the risk of arrhythmic death. Diagnostic Strategies Stable Coronary Artery Disease Two diagnostic strategies exist for the diagnosis of stable coronary artery disease. The underlying process is the presence of coronary stenoses that lead to myocardial ischemia. Testing can aim either at identifying the ischemic myocardium under exercise or at the direct visualization of coronary artery stenoses. Since not all coronary stenoses cause ischemia, and since stenoses that do not cause ischemia do not require revascularization, the usual preferred approach in patients with suspected stable coronary artery disease is the noninvasive identification of stress-induced myocardial ischemia by an imaging-based stress test. Ischemia can be achieved with physical exercise (treadmill or bicycle exercise) or pharmacologic stress (dipyridamole or dobutamine to increase contractility and myocardial oxygen demand or adenosine to achieve maximum vasodilation and “steal” effects). Commonly used tests include single-photon emission computed tomography (SPECT) and positron emission tomography (PET) myocardial perfusion and metabolic imaging, stress echocardiography, and stress magnetic resonance (MR) imaging. Another strategy is the direct visualization of coronary anatomy, as achieved by invasive coronary angiography or noninvasively by computed tomography (CT) coronary angiography. It is limited by the fact that not all stenoses cause ischemia and, hence, require revascularization, and if a stenosis is detected, it may be difficult to determine whether it mandates treatment. Invasive coronary angiography can be combined with measurement of the fractional flow reserve (FFR), which quantifies the relationship of mean arterial blood pressure before and after the stenosis during maximum vasodilation achieved by adenosine. Currently, FFR is considered the gold standard to identify myocardial ischemia, and FFR values < 0.8 indicate that the respective lesion should be revascularized. Both testing approaches, ischemia and coronary anatomy, have certain limitations. Ischemia testing has limited sensitivity and specificity. Also, ischemia testing cannot identify coronary atherosclerotic plaque, which is nonobstructive but might have implications for the future cardiovascular event risk. Anatomic imaging, on the other hand, often identifies stenoses, and the treating physician (and patient) may feel compelled to perform revascularization, even though not all stenoses cause relevant ischemia. Additionally, invasive coronary angiography is associated with potential complications, and noninvasive coronary angiography by CT suffers from limited image quality, which, if misinterpreted, can lead to false-positive findings and unnecessary downstream testing. Hence, the testing strategy has to take into account patient characteristics, pretest likelihood, and also local expertise with the various diagnostic tests. The most frequently applied strategy encompasses initial testing for ischemia, followed, if positive, by anatomic imaging. Coronary visualization by CT, however, may be a suitable alternative to reliably rule out coronary stenoses, especially in patients who do not have a high likelihood of being diseased. Acute Coronary Syndromes Acute coronary syndromes encompass a wide spectrum from unstable angina to ST-segment elevation myocardial infarction (STEMI). In STEMI, electrocardiography is the only test performed and leads to immediate coronary catheterization. In non-ST elevation acute coronary syndromes, further testing is usually performed before a decision about invasive angiography can be made. It includes laboratory testing (troponin) complemented by echocardiography to exclude differential diagnoses (acute pulmonary embolism, aortic dissection) and assess regional as well as global left ventricular function. It may also include testing for ischemia. Coronary CT angiography plays an increasingly important role to rule out coronary artery disease, especially in patients who present with acute chest pain but have a relatively low pretest likelihood of acute coronary disease. Only gold members can continue reading. Log In or Register to continue Share this:Click to share on Twitter (Opens in new window)Click to share on Facebook (Opens in new window) Related posts: page Copyright Approach to Shunts INDEX Multimodality Approach to Cardiovascular Disorders Approach to Heart Failure Stay updated, free articles. 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