Ischemic Heart Disease dept book cardio.pdf

Grehemie Ptoart scare ISCHEMIC HEART DISEASE Mohammad Salem, M.D. The coronary circulation (Fig. 2-29) The left main coronary and right coronary arteries...

Grehemie Ptoart scare ISCHEMIC HEART DISEASE Mohammad Salem, M.D. The coronary circulation (Fig. 2-29) The left main coronary and right coronary arteries arise from the left and right coronary sinuses just distal to the aortic valve. 1. The left main coronary artery Within 2.5cm of its origin, the left main coronary artery divides into: The left anterior descending artery (LAD) which runs in the anterior interventricular groove. It gives branches to supply the anterior left ventricle, the apex and the anterior part of the septum The circumflex artery (LCX) which runs posteriorly in the atrioventricular grooveit gives marginal branches to supply the posterior left ventricle and inferior surface. 2. The right coronary artery (RCA) runs in the right atrioventricular groove. It gives branches to supply: The right atrium, the right ventricle and the infero-posterior aspect of the ‘left ventricle. (as the posterior descending vessel in the posterior inter ventricular groove). In most individuals the RCA, supplies the posterior descending artery, but in the remainder there is a dominant left system which supplies this vessel from the LCX. The sinoatrial node (SAN) is supplied by the right coronary artery in about 60% of individuals and the atrio- ventricular node (AVN) in 90%. The venous system mainly follows the coronary arteries but drains to the coronary sinus in the inferior atrio-ventricular groove and then to the right atrium. Aorta LCA (left coronary artery) Left main coronary artery Superior ———~ Pulmonar vena Cava artery an valve es ae Sinoatrial node — (left anterior descending artery) RCA— (right coronary arlery) —__—_-—--—-— Septal perforator branches CX (circumflex artery) Diagonal branches Obtuse marginal Posterior descending Inferior vena cava Apex Fig. (2-29): The coronary circulation Fs eS ESF SES ED EE 49 Cardiovascular  CORONARY ARTERY DISEASE (CAD) Ischemic Heart Disease Coronary artery disease (CAD) is also referred to as ischemic heart disease (IHD) and is usually due to atherosclerosis of a coronary artery. The term ischemic heart disease (IHD) describes a group of clinical syndromes characterized by myocardial ischemia, an imbalance between myocardial blood supply and demand Table (2-3): Classification of CAD: Stable CAD (chronic coronary syndrome) Acute coronary syndromes (ACSs) Stable angina pectoris. Unstable angina (UA). Vasospastic angina (Prinzmetal variant Non-ST-segment elevation myocardial angina). infarction (NSTEMI). Microvascular angina (syndrome X). ST -segment elevation myocardial Angina associated with myocardial bridging infarction (STEMI). of coronary arteries. Unspecified myocardial infarction (MI). Sudden cardiac death Stable CAD (chronic coronary syndrome) Stable Angina (Angina pectoris) Angina is a symptom, which must be recognized by its clinical manifestations. Etiology: The most common cause is atherosclerotic narrowing of one or moreepicardial coronary arteries. Theepicardial coronary arteries serve as conduits and are refen·ed to as conductance vessels, while the intra-myocardial arteries normally exhibit striking changes in tone and are therefore referred to as resistance vessels. Abnormal constriction of these vessels can cause ischemia, this condition is referred to as microvascular angina.This constriction can also occur in vasculitis and coronary embolization. Despite normal pericardia! coronary arteries, myocardial ischemia can develop due to increase in myocardial oxygen demand because of myocardial hypertrophy, e.g hypertension, aortic stenosis, hypertrophic cardiomyopathy and aortic regurge Vasculitis of the coronary arteries, metabolic disorders affecting the coronary at1eries, anatomic defects of the coronary arteries, coronary artery injury, mierial thrombosis due to disorders of hemostasis A reduction in oxygen carrying capacity of blood as in severe anemia. 50 Canfiovascu(ar  Pathophysiology: Myocardial ischemia is caused by an imbalance between myocardial oxygen supply and oxygen demand. Severe coronary narrowing and myocardial ischemia are frequently accompanied by the development of collateral vessels, especially when narrowing develops gradually. Effects of ischemia: It causes transient disturbances of the mechanical, biochemical and electrical function of the myocardium. Mechanical: transient left ventricular failure, mitral regurge if papillary muscles are involved. Biochemical: with severe oxygen deprivation, glucose is broken down to lactate and fatty acids can not be oxidized. Electrical: ventricular tachyarrhythmias. Risk factors for coronary atherosclerosis: 1. Age: men > 45y, women > 55y. 2. Family history of premature coronary heart disease (CHD). 3. Cigarette smoking. 4. Hypertension. 5. Diabetes mellitus. 6. Dyslipidemia. 7. Obesity. 8. Chronic kidney disease 9. Psychosocial factors such as stress and depression Clinical picture: Symptoms: Pain: usually builds up rapidly within 30 seconds and disappears in decrescendo within 5 to 15 minutes. Character: variably described but typically presents as tightness, squeezing orconstriction. Some patients describe an ache, a feeling of dull discomfort, indigestion, or burning pain. (The clenching of the fist over the sternum while describing the pain is classic). Site: retrosternal. It can be precordial Radiation: left shoulder, left arm, back, neck, jaw, teeth, back and rarely epigastrium. The precipitating factors: exertion, emotion, and sexual activity. The relieving factor: rest, and sublingual nitroglycerin. Nocturnal angina: occurring during sleep. Postprandial angina: develops after meals (because of an increased oxygen demand in splanchnic vascular bed) Angina equivalents: No chest pain, instead dyspnea, dizziness, fatigue or faintness , more in diabetics. When these symptoms occur in response to exercise or stress, patients must be evaluated for possible myocardial ischemia. 51 Cardl.ovascu(ar  Signs: Examination is often normal, there may be signs of risk factors. Investigations: ECG: It is normal in 50% of cases, but does not exclude the diagnosis. During anginal episode: ST segment depression, T wave inversion and may be ventricular tachyarrhythmias. B Fig. (2-30): A) ST depression with chest pain. B) ST returns to baseline Continuous ECG monitoring: To detect clinically silent ischemia as episodes of ST -segment depression. Provocative testing: Angina with normal resting ECG, the provocative testing can confinn the presence of ischemia, Stress ECG: Treadmill": Recording the 12-lead ECG before, during and after exercise. the physician should be present throughout the test. The test is discontinued upon evidence of: Chest discomfort, severe dyspnea, dizziness, fatigue, fall in systolic B.P. > 10 mmHg., ST segment depression of greater than 0.2 mV, or ventricular tachyarrhythmias :Sl A. B Fig. (2-31): ST Segement depression with exercise NB: The nom1al response to exercise includes a progressive increase in heart rate and blood pressure. 52 CardiovascuCar 1- Cardiac radio nucleotide imaging: Using thallium 201 shows area of absent perfusion during exercise, by means of a gamma camera, which is reversible 4 h. later. 2- Echocardiogram: to assess for ventricular dysfunction it directly affects management. If it shows reduced L VEF. It may also show regional wall motion abnormalities suggestive of ischemia or an old infarction within a specific coronary artery territory. 3- Stress echocardiogr-aphy: After I.V. dobutamine (pharmacological challenge) or exercise shows areas of regional wall motion abnormality (akinesia) in the left ventricle due to persistent ischemia or MI. 4- Multislice CT coronary angiography is emerging as the most reliable noninvasive method for coronary artery disease assessment. 1. For detection of define coronary anatomy with the aim of identifying flow-limiting atherosclerotic lesions, coronary plaques and significant obstructive coronary lesions. n. A coronary angiogram may occasionally be used to diagnose IHD in a patient with an atypical clinical presentation or indeterminate stress test results 111. In refractory ischemic symptoms despite goal-directed medical therapy. 5- Positron emission tomography (PET) (with exercise or pharmacologic stress). Indications: for assessing perfusion. Intravenous pharmacologic challenge Indications: patients who cannot exercise because of peripheral vascular or musculoskeletal disease Aim: To create a coronary "steal" by temporarily increasing flow in non-diseased segments of the coronary vasculature at the expense of diseased segments. For example, dipyridamole or adenosine to identify myocardial ischemia and increased risk of coronary events in exertional dyspnea.The development of a transient perfusion defect with radioactive thallium or 99111Tc to detect myocardial ischemia. 6- Cardiac magnetic resonance (CMR) stress testing It is evolving as an alternative to radionuclide, PET, or echocardiographic stress imaging. CMR stress testing perforn1ed with dobutamine infusion. Indications: to assess wall motion abnormalities accompanying ischemia. 7- Multislice MR imaging and myocardial perfusion CMR Indications: provide rather complete ventricular evaluation. 53 Carcfiovascu[ar  8- Coronary angiography: This invasive diagnostic method shows narrowing of coronary artery lumen. It can assess the severity of obstruction. Indications: l. Confirm or exclude the diagnosis of ischemia. 2. Patients who are severely symptomatic despite medical treatment. 3. Severe ischemia as demonstrated in non invasive testing. 4. High risk patients, including left ventricular dysfimction. Treatment: The goals of treatment of stable angina involve: Therapies that slow down the atherosclerotic disease, decrease future events of myocardial infarction, and decrease mortality. These goals can be achieved with a variety of modalities including: - Medical therapy: non-phrumacologic and lifestyle measures - Revascularization with either percutaneous coronary intervention (PCI) or coronary artery bypass graft surgery (CABG). I. Control of risk factors and associated disorders: Stop smoking. Treatment of hypertension, diabetes, anemia, infection, chronic kidney disease. Lowering LDL cholesterol