Medical and Surgical Treatment of Angina Pectoris

There are four main aims in the managements of patients with coronary artery disease:

1.To address underlying conditions that provoke or exacerbate angina;
2.To prevent myocardial infarction and death;
3.To give pharmacological therapy for angina;
4.Revascularization.

Identify and address any precipitating factors

Attention should be given to underlying conditions that provoke or exacerbate angina. These include anaemia, hyperthyroidism, tachyarrhythmias (irregular and high heart rates) and valvular heart disease. Drugs that are known to provoke angina such as vasoconstrictors and vasodilators should be substituted with other similar agents that have a neutral cardiovascular profile.

Lifestyle and risk factor modification

The cessation of smoking should be encouraged as coronary heart disease risk will decline. However, it may be up to 10 years before the baseline risk is achieved compared to non-smokers.

There is a strong relationship between blood pressure and coronary heart disease risk. Hypertension should be controlled, aiming for a systolic pressure of less than 140 mmHg and diastolic pressure of less than 90 mmHg.

A number of primary and secondary prevention trials have shown that cholesterol lowering is associated with a reduced risk of coronary events, and serum levels should be maintained below 5.0 mmol/L.

Although definitive evidence is not yet available on strict glycaemic control and reduction of coronary disease risk, current consensus opinion favors tight blood sugar control in diabetics and patients with impaired glucose tolerance.

Aspirin

The use of aspirin (75-325 mg) is associated with an average 33% reduction in coronary events. It should be prescribed for all patients with angina unless absolutely contraindicated. Under these circumstances, an alternative anti platelet agent such as clopidogrel should be considered.

Medical management of Angina Pectoris:

Sublingual nitrates
Short-acting sublingual glyceryl trinitrate (nitroglycerin) works quickly in treating acute attacks of angina.

β-Blockers
Numerous β-blockers are available and appear equally effective. The mode of action is by decreasing heart rate, contractility and blood pressure, and hence the oxygen demands of the heart. β-Blockers are frequently combined with nitrates to ameliorate reflex tachycardia. Although limited data exist in the setting of chronic stable angina, reduction of mortality after myocardial infarction is established. β- Blockers also improve survival and prevent stroke in patients with hypertension.

Long-acting nitrates
Prophylaxis can be achieved with longer-acting preparations such as isosorbide mononitrate and isosorbide dinitrates. Nitrates improve exercise tolerance and time to onset of angina by reducing pre-load and promoting coronary artery vasodilatation. The main problems with nitrates are headaches (which subside as the patient gets used to the drug), reflex tachycardia and the development of tolerance.

Calcium antagonists
Calcium antagonists exert a negative inotropic effect by reducing the transmembrane flux of calcium. They can be broadly divided into short-acting dihydropyridine (nifedipine), long-acting dihydropyridine (amlodipine, felodipine) and non-dihydropyridine calcium antagonists (e.g. diltiazem, verapamil). All the calcium antagonists are of similar efficacy in treating chronic stable angina and are excellent first-line agents for vasospastic (Prinzmetal's) angina.


Latest developments in medical management of angina
A number of agents have been introduced recently for the treatment of angina. Nicorandil (a potassium channel activator) is effective in the treatment of angina, although evidence of comparative efficacy with other anti-anginal agents and reduction of adverse events are awaited.


Revascularization
The indications for revascularization are symptomatic (angina refractory to maximal medical therapy) and prognostic. Prognostic features for revascularization are determined from a coronary artery disease configuration obtained by coronary angiography. The following adverse prognostic features are clearly associated with survival benefit from revascularization:

a. left main stem coronary artery disease
b. triple vessel disease
c. double vessel disease involving the proximal left anterior descending artery.

Percutaneous coronary interventions (PCI)
Catheter-based intervention techniques are employed for patients with suitable anatomy (discrete and short segments of stenosis) without left main involvement, poor ventricular function or diabetes.

Percutaneous transluminal coronary angioplasty (PTCA) is employed by femoral arterial puncture and introduction of a catheter into the aorta and subsequently into the coronary arteries. Balloon dilatation of coronary stenoses is undertaken under radiological guidance. Freedom from angina is achieved in 72% of patients at one year. The mortality rate associated with angioplasty is 1% and the frequency of myocardial infarction is 5%. Other procedural complications are similar to coronary angiography. The main disadvantage is the high proportion of re-stenosis, occurring in 30-40% at 6 months.

The use of coronary stents has increased due to lower rates of re-stenosis and re-intervention compared to PTCA. Self-expanding stents are deployed in the coronary arteries using the same approach as PTCA.

Latest invasive therapies in angina:
Other new therapies currently under evaluation are the use of drug eluting stents to minimize restenosis, coronary atherectomy, and laser angioplasty that directly ablates coronary artery plaques.



Surgical management of Angina

When revascularization is indicated, coronary artery bypass surgery is preferred for patients with left main stem involvement, diabetes and poor ventricular function as survival advantage has been demonstrated over PCI. Surgery is also advocated for patients with unsuitable anatomy for PCI (long complex stenosis and occluded vessels).

What is done in Coronary artery bypass surgery?

The sternum, the central bone of the chest is opened longitudinally with an oscillating saw. The internal mammary artery is harvested simultaneously with the long saphenous vein by a second surgeon . The pericardium is opened and cardiopulmonary bypass is instituted. The heart is arrested using cardioplegia solution containing a high concentration of potassium . The segments of long saphenous veins are reversed and anastomosed to the coronary arteries and aorta . This will deliver blood directly from the aorta to the coronary arteries, bypassing segmental stenoses. The internal mammary artery is anastomosed directly to the left anterior descending artery as a pedicle graft. Once the cardioplegia solution is washed out of the coronary system, the heart resumes beating. All the bleeding are secured and the sternum closed with stainless steel wires.

Coronary artery bypass surgery can prolong the quantity and quality of life. The success rate is 95% for complete relief of angina, although this falls to 75% at 5 years. The average mortality rate of this procedure is 3%. Postoperatively, stroke occurs in 3% and transient atrial fibrillation in 30%. Other complications include bleeding and wound infection.

Latest developments in Coronary artery surgery

Coronary artery surgery can currently be performed without the use of cardiopulmonary bypass (off pump) with the use of specific stabilizers. The advantages and impact on graft patency are currently under evaluation. Coronary revascularization using only arterial grafts (internal mammary and radial arteries) is also under evaluation to determine if graft patency can be improved. Thoracoscopic robotic surgical techniques of coronary surgery without sternotomy or bypass are currently being developed.



Prognosis of chronic stable angina:

The average mortality of patients with chronic stable angina is 2-3% per year with a similar risk of myocardial infarction at 2-3% per year

What is angina?
Diagnosis of Angina.
Medical and Surgical Treatment of Angina.