- Miscellaneous: metabolic, embolic, prinzmetal, dissection.
- Increased O2 demand: thyrotoxicosis.
- Decreased O2 supply: anemia, carbon monoxide poisoning.
The overall incidence of death as a result of Ischemic heart disease is 0.5 in 1000. Certain risk factors increase the incidence of this disease and its complications.
- Age: the incidence increases with age, the incidence being 1.5 in 1000 at the age of 50.
- Gender: Males are more prone than females (especially premenopausal women). Males are 5 times more prone to develop the disease at the age of 50.
- Serum cholesterol: A ratio of LDL to HDL of greater than 4:1 increases the risk dramatically. Conversely, a higher HDL level seems to offer protection. Serum cholesterol levels should be kept below 200mg/dL.
- Smoking: increases the incidence by 60%.
- Hypertension: whether systolic or diastolic tends to increase the risk.
- Diabetes mellitus: is known to increase the incidence of IHD both in males and females.
- Family history: a familial predisposition is known to exist and is in part due to inheritence of the above risk factors.
- Oral contraceptives is associated with an increased incidence of myocardial infarction.
- Gout, Type A personality, premature arcus corneae, obesity, hypertriglyceridemia and diagonal ear lobe crease have all been reported to increase the risk of developing ischemic heart disease.
Stable angina pectoris is caused by an imbalance between myocardial oxygen consumption and myocardial oxygen demands. MVO2 (myocardial oxygen demands) are affected by heart rate, blood pressure + contractility, tension.
ECG shows downslope of the ST segment during an attack or stress test. It may show upslope in Prinzmetal's angina.
Central chest tightness or heaviness which is brought on by exertion and relieved by rest. It may radiate to the arms, the neck, jaw or teeth. Associated symptoms include dyspnea, nausea, sweatiness, faintness.
- Cold weather
- Heavy meals
Exercise stress test
Exercise must increase the heart rate to 85% of the predicted maximum for age to reach the optimal test specificity of 75%.
The stress test not only helps in the diagnosis of ambiguous cases but is required for stratification of patients with established angina into those with high risk of developing MI and those with low risk.
Stratification is established by categorizing patients into those that are markedly positive and those that aren't.
Markedly positive patients have any of the following:
- New ST depression >1mm early after start.
- New ST depression >2mm in multiple leads.
- Unable to exercise for > 2mints.
- Decrease BP.
- Heart failure / sustained arrhythmia
- > 5mints after exercise needed for ST depression to normalize.
Patients with markedly positive results should be referred for arteriography for assessment of possible revascularisation. Patients with known angina who can complete 7mints of the standard test without significant ST changes have an excellent prognosis with medical treatment alone.
Invasive diagnosis of CAD: angiography is the definitive test for CAD. Associated with 0.2% operative mortality in elective cases. Significant obstruction is defined as that which is >70% reduction of the arterial lumen.
Also prognostic information about the number of vessels involved and the condition of the left ventricle.
- stable angina with markedly positive stress tests.
- stable angina refractory to medical management.
The purpose is to stratify patients into high risk group indicated for coronary artery bypass grafting (CABG) and low risk groups for medical treatment or percutaneous transluminal coronary angioplasty (PTCA).
High risk group
- Left main CAD, multivessel disease, proximal left anterior descending coronary.
- Ejection fraction < 40%.
- Other clinical factors taken into account: older age, DM, hypertension, severe angina, ST elevation at rest, markedly positive stress test, prior MI.
75% remain free of manifestations at 5yrs; use of internal mammary artery graft is associated with 10yr graft patency. After 10yrs 50% develop recurrence either in the vein graft or in native vessels.
Includes balloon angioplasty, intracoronary stenting, various atherectomy devices; success is achieved in 90% of cases. Recurrence 50% in 6months, stenting reduces this incidence.
Patient for PTCA should aspirin before and heparin during and after to reduce the risk of thrombosis.
Medical treatment of stable angina pectoris
- All patients should be instructed to take sublingual nitroglycerin or aerosol form. It is available in 0.4 and 0.6mg concentration. The response should be evident within 2 mints, if not the dose can be repeated every 5mints (usually not more than 3 tabs should be given and not more than 9mints should elapse) if so the patient should consult a doctor.
- All patients should be treated with aspirin. Which irreversibly inhibits platelet cyclo-oxygenase activity interfering with platelet adhesion. One aspirin is usually enough (300mg).
- All activities stopped, adequate rest and graduated exercise program + modification of risk factors, treatment of aetiological and precipitating factors.
- Patients with recurrent episodes of exertional dyspnea should take beta-blockers unless contraindicated.
If resistant to monotherapy with beta-blockers a calcium antagonist or long acting nitrate is added.
Patients with persistent symptoms that are prescribed all 3 drugs should be referred for angiography and revascularisation.