Coronary artery disease

Coronary artery diseaseMamoon Rashid2011M022Patient storyA 45-year-old man began having chest pressure with exertion that was relieved with rest. He did not have diabetes, high blood pressure, or high cholesterol, and had never had a myocardial infarction. His examination and resting ECG were normal. On the basis of the testing modalities available, he was scheduled for exercise stress testing. After a positive test, he underwent coronary angiography that demonstrated a significant stenosis in the left coronary artery. He underwent a stenting procedure and was placed onaspirinand cholesterol-lowering medication.IntroductionIn the United States, a person dies of coronary heart disease every 39 seconds. Coronary heart disease is a manifestation of atherosclerotic disease and has many modifiable risk factors. Patients with and without coronary heart disease should be advised to stop smoking, maintain normal blood pressure and cholesterol levels, exercise, achieve or maintain a normal weight, and control diabetes mellitus if present.EpidemiologyCoronary heart disease (CHD) is the leading cause of death in the United States, responsible for approximately 400,000 deaths in 2008.Each year, 1.5 million myocardial infarctions occur (first and recurrent) with a 33% mortality rate.In 2005, the prevalence of CHD among U.S. adults older than 18 years of age was higher in men than woman (8.2% vs. 5.0%).

Etiology & PathophysiologyMyocardial ischemia is the result of an imbalance between myocardial oxygen supply and demand. Coronary atherosclerosis and other diseases reduce the supply of oxygenated blood by obstructing the coronary arteries. Although the obstructions may not be enough to produce myocardial ischemia at rest, increases in myocardial oxygen demand during activities can precipitate myocardial ischemiaEtiology & PathophysiologyCHD is one of several manifestations of atherosclerotic disease, which begins with endothelium dysfunction.Endothelium, when normal, balances vasoconstrictors and vasodilators, impedes platelet aggregation, and controls fibrin production.Dysfunctional endothelium encourages macrophage adhesion, plaque growth, and vasoconstriction by recruiting inflammatory cells into the vessel walls, the initiating step of atherosclerosis.The vessel wall lesions develop a cap of smooth muscle cells and collagen to become fibroadenomas.The vessels with these lesions undergo enlargement, allowing progression of the plaque without compromising the lumen.After plaque rupture, the exposed lipid core triggers a superimposed thrombus that occludes the vessel.Increased thrombosis is triggered by known cardiac risk factors including elevated low-density lipoprotein (LDL) cholesterol, cigarette smoking, and hyperglycemia.

Nonatherosclerotic Causes of Epicardial Coronary Artery ObstructionFixedCongenital anomaliesMyocardial bridgesVasculitidesAortic dissectionGranulomasTumorsScarring from trauma, radiationTransientVasospasmEmbolusThrombus in situNonatherosclerotic Causes of Epicardial Coronary Artery ObstructionRISK FACTORSMajor independent risk factorsAdvancing ageTobacco smokingDiabetes mellitusElevated total and low-density lipoprotein (LDL) cholesterolLow high-density lipoprotein cholesterolHypertension

Predisposing risk factorsAbdominal obesityEthnic characteristicsFamily history of premature coronary heart diseaseMetabolic syndromeObesityPhysical inactivityPsychosocial factorsSigns & SYMPTOMSThe major symptom is angina pectoris, with a clinical diagnosis based on five features:The character of the pain is a deep visceral pressure or squeezing sensation, rather than sharp or stabbing or pinprick-like pain.The pain almost always has some substernal component, although some patients complain of pain only on the right or left side of the chest, upper back, or epigastrium.The pain may radiate from the thorax to the jaw, neck, or arm. Arm pain in angina pectoris typically involves the ulnar surface of the left arm. Occasionally, the radiated pain may be more noticeable to the patient than the origin of the pain, resulting in complaints of only jaw or arm pain. Angina pectoris is transient, lasting between 2 and 30 minutes. It is relieved by cessation of the precipitating event, such as exercise, or by the administration of treatment, such as sublingualnitroglycerin. AGGRAVATING FACTORSIncreased myocardial oxygen demandTachycardiaHypertensionThyrotoxicosisHeart failureValvular heart diseaseCatecholamine analogues (eg, bronchodilators, tricyclic antidepressants, cocaine)Reduced myocardial oxygen supplyAnemiaHypoxiaCarbon monoxide poisoningHypotensionTachycardiaDiagnosis:Physical examinationThe physical examination is often not helpful in the diagnosis of chronic ischemic heart disease. This is because many patients with chronic ischemic heart disease have no physical findings related to the disease, or if they do, the findings are not specific for coronary artery disease. For example, a fourth heart sound can be detected in patients with chronic ischemic heart disease, especially if they have had a prior myocardial infarction; however, fourth heart sounds are very common in hypertensive heart disease, valvular heart disease, and primary myocardial disease.Diagnosis:lab testsA complete blood count is useful to detect anemia, which will aggravate angina. Thyroid function tests are also important since hyperthyroidism can aggravate angina and hypothyroidism can lead to atherosclerosis. High-sensitivity C-reactive protein (CRP) has been used to detect the increased inflammation of active atherosclerosis. Values greater than 3 mg/L predict coronary events.Mortality can be predicted by brain natriuretic peptide (BNP) or troponin levels in patients with coronary artery disease. Diagnosis:non invasive testsECG:ECG is the most frequently used method for detecting myocardial ischemia because of its ready availability, low cost, and ease of application. The usual criterion for diagnosing ischemia is horizontal or down-sloping ST segment depression.EXCERSICE STRESS TESTPHARMACOLOGICAL STRESS TESTING:There are two basic kinds of pharmacologic stress tests. One uses drugs, such as the synthetic catecholaminedobutamine, that mimic exercise; the other uses vasodilator drugs, such asadenosine, that, by producing profound vasodilatation, increase heart rate and stroke volume, thereby raising myocardial oxygen demand.Newer methods being tested include CT for diagnosis.Diagnosis : invasiveCoronary Angiography:Coronary angiography is the standard for evaluating the anatomy of the coronary artery tree. It is best at evaluating the large epicardial coronary vessels that are most frequently diseased in coronary atherosclerosis. Experimental studies suggest that lesions that reduce the lumen of the coronary artery by 70% or more in area significantly limit flow. If such lesions are detected, they are considered compatible with symptoms or other signs of myocardial ischemia.

Date of download: 11/8/2015Copyright 2015 McGraw-Hill Education. All rights reserved.Coronary arteriogram demonstrating severe stenosis (white arrow) in the left coronary artery. Note that the circumflex artery (CX) is patent.

Legend:The Color Atlas of Family Medicine, 2e, 2013

TreatmentTreatment consists of increasing supply or reducing demandor both. Heart rate is a major determinant of myocardial oxygen demand, and attention to its control is imperative. Any treatment that accelerates heart rate is generally not going to be efficacious in preventing myocardial ischemia.. Furthermore, because most coronary blood flow occurs during diastole, the longer the diastole, the greater the coronary blood flow; and the faster the heart rate, the shorter the diastole.Blood pressure is another important factor: Increases in blood pressure raise myocardial oxygen demand by elevating left ventricular wall tension, yet blood pressure is the driving pressure for coronary perfusion. A critical blood pressure is required that does not excessively increase demand, yet keeps coronary perfusion pressure across stenotic lesions optimaltreatmentDrugUsual DoseComments; Adverse EffectsNitratesNitroglycerin0.40.6 mg sublingualAborts acute attacks; headaches, hypotensionIsosorbide dinitrate1060 mg three times dailyNeed 8 h off every 24 h to avoid toleranceIsosorbide mononitrate20 mg twice dailyTake 7 h apartDrugDaily Dosage (mg)Comments; Adverse Effects-BlockersPropranolol160320Central nervous system side effectsfatigue, impotencecommonMetoprolol100400CardioselectiveAtenolol50200CardioselectiveBisoprolol520CardioselectivePindolol540Marked intrinsic sympathomimetic activityCalcium Channel Blockers, Heart Rate LoweringDiltiazem120360Heart rate lowering; atrioventricular (AV) block, heart failure, edemaVerapamil120480Heart rate lowering; AV block, heart failure, constipationDihydropyridine Calcium Channel BlockersAmlodipine510Least myocardial depressionNifedipine3060Hypotension, tachycardiaNicardipine60120Potent coronary vasodilatorSodium Current InhibitorRanolazine10002000 mgMay increase QT interval on ECGADJUVANT THERAPYAll patients with coronary artery disease should takeaspirin(81325 mg/day), and selected high-risk patients should also takeclopidogrel. These drugs reduce platelet aggregation and retard the growth of atherothrombosis. Also important is correction of dyslipidemia, smoking cessation, exercise, weight loss, control of hypertension, and management of stress. In patients with known coronary artery disease, it is important to decrease low-density lipoprotein (LDL) cholesterol and perhaps increase high-density lipoprotein (HDL) cholesterol to published targets (< 100 mg/dL and > 40 mg/dL, respectively). Angiotensin-converting enzyme (ACE) inhibitors may have a protective effect in patients with coronary artery disease, especially postmyocardial infarction.Treatment:revascularizationCatheter Based Methods:The standard percutaneous coronary intervention (PCI) is balloon dilatation with placement of a metal stent. Such treatment is limited to the larger epicardial arteries and can be complicated by various types of acute vessel injury, which can result in myocardial infarction unless surgical revascularization is immediately performed. Smaller arteries may be amenable to plain old balloon angioplasty (POBA).PCI requires intense antiplatelet therapy, usually withaspirinandclopidogrel, to prevent stent thrombosis. In the absence of acute complications, initial success rates for significantly dilating the coronary artery are greater than 85%, and the technique can be of tremendous benefit to patients.The principal disadvantage to PCI is restenosis, which occurs in about one-third of patients treated with a bare metal stent during the first 6 months.

Treatment:revascularizationCoronary Artery Bypass Graft Surgery:Controlled clinical trials have shown that coronary artery bypass graft (CABG) surgery can successfully alleviate angina symptoms in up to 80% of patients with less than 2% operative mortality rates. Although the initial cost of surgery is high, studies have shown it can be competitive with repeated angioplasty and lifelong pharmacologic therapy in selected patients.The standard surgical approach is to use the saphenous veins, which are sewn to the ascending aorta and then, distal to the obstruction, in the coronary artery, effectively bypassing the obstruction with blood from the aorta.The major problem with saphenous vein grafts is recurrent atherosclerosis in the grafts, which is often quite bulky and friable.

prognosisThere are two major determinants of prognosis in patients with chronic ischemic heart disease. The first is the clinical status of the patient, which can be semiquantitated by the Canadian Cardiovascular Societys angina functional class system. In this system, class I is asymptomatic, II is angina with heavy exertion, III is angina with mild-to-moderate exertion, and IV comprises patients who cannot perform their daily activities without getting angina or who are actually experiencing angina decubitus. The higher the Canadian class, the worse the prognosis.A second prognostic system is based solely on coronary anatomy. The more vessels involved, and the more severely they are involved, the worse the prognosis.QuestionsName 1 drug used for Pharmacological Stress Testing: Dobutamine

Angina with Heavy Exertion belongs to which Canadian Class? Class 1/Class2/Class 3 or Class 4? Class 2Hypothyroidism can aggravate angina? True or False : FalsePlain Old Baloon Angioplasty is used for Small or Large areteries? : SmallCoronarly blood flow occurs mostly in Diastole or Systole? : Diastole