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Back to Cardiovascular Diseases
Stable angina pectoris
Definition
Chest pain in a patient already diagnosed to have ischemic
heart disease that did not change its pattern during the preceding 2 months.
Causes
-
Congenital
-
Traumatic
-
Inflammatory
-
Tumor
-
Miscellaneous: metabolic, embolic, prinzmetal, dissection.
-
Increased O2 demand: thyrotoxicosis.
-
Decreased O2 supply:anemia, carbon monoxide poisoning.
Risk Factors
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.
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Pathogenesis
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.
Clinical picture
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.
Precipitating factors
- Exercise
- Emotion
- Cold weather
- Heavy meals
Management
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.
Arteriography
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.
Indications:
- 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.
CABG
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.
PTCA
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.
Please
refer to the guideline search for new updated guidelines (click "guidelines"
on the left hand menu").
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