Investigations
Blood tests
Full blood count to exclude anaemia and leucocytosis as an indicator of infection, urea and electrolytes, fasting glucose and a fasting lipid profile are the usual blood tests considered.
ECG
For patients with intermittent chest pain, ECG is often normal between episodes of pain. Look for changes suggesting coronary artery disease like abnormal Q waves, ST elevation or depression, and abnormal T waves, arrhythmias and evidence of left ventricular hypertrophy. An ECG during paing a repeat ECG after 24 to 48 hours are important add ons, often yielding valuable information. 5 – 10% of myocardial infarctions may be missed in an initial ECG. 24 hour Holter (ambulatory) ECG recording is useful in assessing the total ischemic burden, both silent and manifest.
Chest X-ray to assess cardiac size or exclude pneumonia or pneumothorax. Coronary angiography, radionuclide imaging and cardiac magnetic resonance imaging are the other imaging modalities useful in selected cases.
Coronary angiography
Coronary angiography is of course currently the gold standard for the diagnosis of coronary artery disease, though it may miss out abluminally growing plaques, being a luminogram. Coronary angiography is undertaken for the assessment of angina uncontrolled by medication, mainly to know the suitability for coronary intervention. Angiography is also needed in case of recurrence of angina following coronary angioplasty or bypass grafting. A strongly positive exercise test is an important indication for coronary angiography. Severity of coronary narrowing is described using percentage stenosis. Thoug >50% is usually regarded as significant disease, interventions are considered only for stenosis of 70% or more.
Management of angina
There are two main therapeutic goals: Relief of symptoms and improvement of prognosis
Beta blockers should be used as the first line therapy for the relief of symptoms. They act by reducing the myocardial oxygen demand in case of angina of increased demand. Patients who are intolerant to beta blocker can be treated with calcium channel blockers, long acting nitrates and nicorandil. These agents can also be used as add on therapy when angina is not adequately controlled with beta blockers and the option for coronary revascularisation is not available.
Beta blockers
Beta-blockers reduce the effects of the sympathetic nervous system on the cardiovascular system.
Beta-1 adrenoreceptor blockers act by their negative chronotropic and inotropic effects. They also have a negative dromotropic effect in that they delay the conduction through the AV node, which is useful in controlling the ventricular rate in atrial fibrillation, contributing to relief of angina in cases in which the fast rate in atrial fibrillation has precipitated the anginal episode. Atenolol and metoprolol are relatively specific for beta-1 receptors or “cardioselective”.
Aspirin (acetyl salicylic acid)
Aspirin is given for all patients with coronary artery disease unless contraindicated. It is one of the most important agents for secondary prevention of myocardial infarction. It has a role in primary prevention as well.
ACE Inhibitors
ACE inhibitors are initiated early in the course of myocardial infarction unless contraindicated and titrated upwards to the maximum tolerated or target dose. ACE inhibitors can be continued indefinitely in patients with preserved left ventricular (LV) function or LV systolic function, whether or not they have heart failure symptoms, to improve the long term prognosis. They can prevent ventricular remodeling in case of large infarcts and reduce the chance for left ventricular dysfunction.
Assessment/monitoring
Assess LV function in all patients who have had a myocardial infarction, by echocardiography. Measure renal function, serum electrolytes and BP before starting an ACE inhibitor or ARB and again within 1 or 2 weeks. Serial rise in creatinine should prompt evaluation for renal artery stenosis.