Acute Coronary Syndrome – Stable Angina Management

Australian Prescriber VOLUME 38 : NUMBER 4 : AUGUST 2015

• Chronic stable angina is predictable in duration and severity, often triggered by physical exertion or emotional stress and relieved by rest or short-acting nitrates.
• The goal of medical therapy is to reduce symptoms and prevent disease progression, which requires a combination of lifestyle changes and drug treatment.

Diagnosis:

• History and clinical examination are essential for diagnosing angina. Symptoms such as chest pain, especially under exertion or stress, raise suspicion of myocardial ischemia.
• Patients should undergo ECG (electrocardiography) and be assessed for cardiovascular risk factors such as:
  • Diabetes
  • Hyperlipidemia
  • Hypertension
  • Smoking status
• Echocardiography assesses left ventricular function, providing insight into heart muscle performance, and helps determine if there’s existing damage due to ischemia or infarction.

Risk Stratification:

• Once stable coronary artery disease is diagnosed, the risk of future cardiovascular events is evaluated.
• The risk is predicted by clinical and demographic variables such as:
  • Gender: Men are at a higher risk of cardiovascular events.
  • Left ventricular function: Lower ejection fractions are associated with worse outcomes.
  • Stress testing results: The presence of ischemia under stress predicts future events.
  • Angiographic severity: More severe and widespread coronary artery disease increases risk.
• High-risk patients may require revascularization procedures (e.g., coronary artery bypass surgery, angioplasty) in addition to medical therapy.

Clinical Evaluation:

• Key risk factors associated with adverse outcomes in angina include:
  • Increasing age
  • Chronic kidney disease
  • Diabetes
  • Hypertension
  • Smoking
  • Previous myocardial infarction (MI)
  • Hypercholesterolemia
  • Heart failure
• Echocardiography plays a key role in assessing left ventricular ejection fraction (LVEF), which is one of the strongest predictors of long-term survival:
  • Patients with LVEF > 50% have a 12-year survival rate of 73%.
  • LVEF between 35-49% corresponds to a survival rate of 54%.
  • LVEF < 35% drops survival to only 21%.

Stress Testing:

• Exercise stress testing (on a treadmill or bicycle) is indicated for patients with a normal resting ECG who can physically exercise.
• During stress testing, various factors are measured:
  • Symptoms: Chest pain, shortness of breath
  • Exercise capacity: How long the patient can exercise before symptoms appear
  • Blood pressure response: Abnormal BP response may indicate ischemia
  • ECG changes: Ischemic changes, such as ST-segment depression
• Stress testing helps evaluate the efficacy of revascularization and guides the prescription of physical activity.
• Pharmacological stress testing (e.g., with dobutamine or adenosine) is used in patients unable to exercise, often combined with echocardiography or nuclear imaging to detect ischemia.

Imaging of Coronary Arteries:

• Coronary artery CT without contrast detects coronary calcification, although the correlation between calcification and luminal narrowing is not always direct.
  • Coronary artery CT is recommended in patients with intermediate risk of coronary artery disease (CAD) where further risk stratification is needed.
• CT angiography with intravenous contrast is used to visualize the coronary arteries and assess the degree of luminal narrowing.
• Invasive coronary angiography is indicated for patients with high-risk features or those whose symptoms are not well controlled with medication, providing direct visualization of coronary stenosis and guiding treatment strategies like revascularization.
  • Survival rates based on angiography findings:
    • Single-vessel disease: 74%
    • Two-vessel disease: 59%
    • Three-vessel disease: 50%
    • Left main or proximal LAD disease has a particularly poor prognosis if untreated.

Lifestyle Modification:

• Lifestyle changes are central to managing chronic stable angina and reducing the risk of cardiovascular events. The key modifiable risk factors include:
  • Hypertension: Control of blood pressure is critical.
  • Hyperlipidemia: Management of cholesterol levels with diet and statins.
  • Smoking cessation: Smoking is a major independent risk factor for coronary artery disease.
  • Diabetes management: Blood glucose control to reduce cardiovascular risk.
  • Obesity: Weight loss to achieve a healthy BMI.
  • Sedentary lifestyle: Encourage regular aerobic exercise.
• Regular exercise and a healthy diet (e.g., the Mediterranean diet) reduce cardiovascular morbidity.
• Smoking cessation is strongly encouraged with pharmacological support if necessary (e.g., nicotine replacement therapy, varenicline).
• Screening for sleep apnea is recommended, as it is often associated with cardiovascular disease.
• Annual influenza vaccination is recommended to prevent complications from respiratory infections.

Prevention of Cardiovascular Events:

• Low-dose aspirin (75-150 mg daily) reduces major cardiovascular events by up to 30% and is recommended for all patients with known coronary artery disease.
• Clopidogrel is an alternative for patients who are intolerant of aspirin.
• Statin therapy should be prescribed for all patients with coronary artery disease, regardless of their cholesterol levels, as it slows the progression and can promote regression of atherosclerosis.
• ACE inhibitors are recommended, particularly for patients with:
  • Hypertension
  • Left ventricular dysfunction
  • Diabetes
  • Chronic kidney disease
• If ACE inhibitors are not tolerated (e.g., due to cough or angioedema), angiotensin receptor blockers (ARBs) are a suitable alternative.

Drug	Indications	Mechanism	Adverse effects	Precautions
Nitrates (short- and long-acting)	Relief of acute or anticipated pain (short-acting) Prevention of angina (long-acting)	Systemic and coronary vasodilation	Headache Hypotension Syncope Reflex tachycardia	Avoid sildenafil and similar drugs Tolerance with long-acting nitrates
Beta blockers	First-line therapy for exertional angina and after myocardial infarction	Reduce blood pressure, heart rate and contractility Prolongs diastolic filling time	Fatigue Altered glucose Bradycardia Heart block Impotence Bronchospasm Peripheral vasoconstriction Hypotension Insomnia or nightmares	Avoid with verapamil because of risk of bradycardia Avoid in asthma, 2nd and 3rd degree heart block and acute heart failure
Dihydropyridine calcium channel antagonists (e.g. amlodipine, felodipine, nifedipine)	Alternative, or in addition, to a beta blocker Coronary spasm	Systemic and coronary vasodilator	Hypotension Peripheral oedema Headache Palpitations Flushing	Avoid short-acting nifedipine because of reflex tachycardia and increased mortality in ischaemia
Non-dihydropyridine calcium channel antagonists (e.g. verapamil, diltiazem)	Alternative, or in addition, to a beta blocker	Arteriolar vasodilator Centrally acting drugs reduce heart rate, blood pressure, contractility, and prolong diastole	Negative inotropic effect Bradycardia Heart block Constipation Hypotension Headache	Avoid verapamil in heart failure and in combination with a beta blocker
Nicorandil	Angina	Systemic and coronary vasodilator	Headache Dizziness Nausea Hypotension Gastrointestinal ulceration	Avoid sildenafil and similar drugs Metformin may reduce efficacy
Ivabradine	Angina Chronic heart failure	Reduces heart rate	Visual disturbances Headache Dizziness Bradycardia Atrial fibrillation Heart block	Caution with drugs that induce or inhibit cytochrome P450 3A4 Avoid in renal or hepatic failure
Perhexiline	Refractory angina	Favours anaerobic metabolism in active myocytes	Headache Dizziness Nausea, vomiting Visual change Peripheral neuropathy	Narrow therapeutic range Need to monitor adverse effects and drug concentrations