Rx of Coronary hear disease (CHD)
Coronary hear disease (CHD)/Ischemic heart disease (IHD) is a condition in which there is an inadequate supply of blood and oxygen to a portion of the myocardium.
It typically occurs when there is an imbalance between myocardial oxygen supply and demand.
The most common cause of myocardial ischemia is atherosclerotic disease - which results in inadequate perfusion of the myocardium.
the single most important cause of premature death in Europe, the Baltic states, Russia, North and South America, Australia and New Zealand.
By 2020 it is estimated that it will be the major cause of death in all regions of the world.
Abnormal constriction or failure of normal dilation of the coronary resistance vessels can also cause ischemia. When it causes angina, this condition is referred to as microvascular angina.
Factors influenting myocardial oxygen supply and demand/Pathophysiology
Oxygen demand
Cardiac work
Heart rate
Blood pressure
Myocardial contractility
Left ventricular hypertrophy
Valve disease, e.g. aortic stenosis
Oxygen supply
Coronary blood flow
Duration of diastole
Coronary perfusion pressure (aortic diastolic minus coronary sinus or right atrial diastolic pressure)
Coronary vasomotor tone
Oxygenation
Haemoglobin
Oxygen saturation
Coronary Atherosclerosis-
Epicardial coronary arteries are the major site of atherosclerotic disease.
The major risk factors for atherosclerosis disturb the normal functions of the vascular endothelium:
high plasma low-density lipoprotein (LDL),
low plasma high-density lipoprotein (HDL),
cigarette smoking,
hypertension, and
diabetes mellitus
These functions include local control of vascular tone, maintenance of an antithrombotic surface, and impairment of inflammatory cell adhesion and diapedesis.
The loss of these defenses leads to inappropriate constriction, luminal thrombus formation, and abnormal interactions with blood leukocytes, especially monocytes, and platelets.
This leads to atherosclerosis.
CORONARY HEART DISEASE: CLINICAL MANIFESTATIONS AND PATHOLOGY
Angina
Angina pectoris is the symptom complex caused by transient myocardial ischaemia and constitutes a clinical syndrome rather than a disease.
It may occur whenever there is an imbalance between myocardial oxygen supply and demand.
Coronary atheroma is by far the most common cause of angina.
The symptom may also be a manifestation of other forms of heart disease, particularly aortic valve disease and hypertrophic cardiomyopathy.
Stable Angina
Occurs when coronary perfusion is impaired by fixed or stable atheroma of the coronary arteries.
Activities precipitating angina
Common
Physical exertion
Cold exposure
Heavy meals
Intense emotion
Uncommon
Lying flat (decubitus angina)
Vivid dreams (nocturnal angina)
Clinical Features
Chest discomfort/pain-
usually described as heaviness, pressure, squeezing, smothering, or choking, and only rarely as frank pain.
typically lasts 2–5 min, and can radiate to either shoulder and to both arms (especially the ulnar surfaces of the forearm and hand).
typically caused by exertion (e.g., exercise, hurrying, or sexual activity) or emotion (e.g., stress, anger, fright, or frustration) and are relieved by rest, they may also occur at rest.
Physical findings-
Usually negative
Evidence of valve disease (particularly aortic)
Important risk factors (eg. Hypertension, diabetes.)
Evidence of left ventricular dysfunction (cardiomegaly and gallop rhythm)
Other conditions- carotid bruits, peripheral vascular disease, anemia and thyrotoxicosis (unrelated conditions)
Cardiovascular Disease Classification Chart
Investigations
Resting ECG- Ischemia causes characteristic changes in the electrocardiogram.
Repolarization abnormalities, as evidenced by inversion of T waves and, when more severe, by displacement of ST segments.
Transient T-wave inversion likely reflects nontransmural, intramyocardial ischemia.
Transient ST-segment depression often reflects subendocardial ischemia.
ST-segment elevation is thought to be caused by more severe transmural ischemia.
Exercise ECG- is performed using a standard treadmill or bicycle ergometer protocol while monitoring the patients ECG, BP and general condition.
Planar or down-sloping of ST segment depression of 1 mm or more is indicative of ishemia.
Up-sloping ST depression is less specific.
A positive exercise test. The resting 12-lead ECG shows some minor T-wave changes in the inferolateral leads but is otherwise normal. After 3 minutes' exercise on a treadmill there is marked planar ST depression in leads II, V4 and V5 (right offset). Subsequent coronary angiography revealed critical three-vessel coronary artery disease.
Other forms of stress testing
Myocardial perfusion scanning-
Stress echocardiography-
Coronary arteriography-
A technetium scan showing reversible anterior myocardial ischaemia. The images are cross-sectional tomograms of the left ventricle. The resting scans (right) show even uptake of technetium and look like doughnuts; during stress (in this case a dobutamine infusion) there is reduced uptake of technetium, particularly along the anterior wall (arrows), and the scans look like crescents (left).
Coronary angiogram from a patient with stable angina. There is severe stenosis of the left main stem (arrow).
Management
Assessment of the likely extent and severity of arterial disease
Identification and control of signifiacant risk factors
The use of measures to control symptoms
The identification of high-risk patients and application of treatments to improve life expectancy
Advice to patients with stable angina
Do not smoke
Aim at ideal body weight
Take regular exercise (exercise up to, but not beyond, the point of chest discomfort is beneficial and may promote collateral vessels)
Avoid severe unaccustomed exertion, and vigorous exercise after a heavy meal or in very cold weather
Take sublingual nitrate before undertaking exertion that may induce angina
Medical Therapy
Antiplatelet therapy- Low-dose (75-150 mg) aspirin, Clopidogrel (75 mg daily) is an equally effective antiplatelet agent that can be prescribed if aspirin causes troublesome dyspepsia or other side-effects.
Anti-anginal drug treatment-
Nitrates GTN (in the form of metered dose aerosol and sublingual tablets), transdermal and oral (isosorbide dinitrate and mononitrate).
Beta blockers
Calcium channel blockers
Potassium channel activators- eg Nicorandil
Invasive Treatment
Percutaneous Coronary Intervention
Coronary Artery Bipass Grafting
Severe stenosis of the circumflex artery (arrow). A balloon has been advanced into the stenosis, over a guidewire, and has been inflated. (Note the waisting caused by the lesion.) Residual stenosis and dissection (tramline shadow-arrow) after balloon dilatation. A stent is deployed on a balloon. The stent is visible on plain fluoroscopy (arrow). Angiogram after stenting. A short balloon is used to dilate the stent at high pressure. Final result.
Coronary artery bypass graft surgery. Narrowed or stenosed arteries are bypassed using saphenous vein grafts connected to the aorta, or by utilising the internal mammary artery.
A scheme for the investigation and treatment of stable angina on effort. (PCI = percutaneous coronary intervention; CABG = coronary artery bypass grafting)
