What is Angina?
Angina is a form of chest pain or discomfort as a result of reduced blood supply to heart muscles. This reduced blood supply results in reduced oxygen supply to heart muscles and as a result deficient waste removal from heart muscles leading to chest pain or discomfort. The most usual reason for this is some form of obstruction of coronary arteries due to medical conditions like atherosclerosis which hampers blood supply to heart muscles resulting in ischemia.
Angina is generally presented as discomfort, tightness, heaviness sensation rather than total pain. Angina occurring at rest and worsening is suggestive of an MI (heart attack) and necessitates instant medical attention and if left untreated causes death. Angina generally occurs with exertion, extreme stress, after heavy meal, in cold temperatures when heart muscles require more oxygen and the obstructed coronary arteries are not able to do it. Anginal pain generally ends in 15 minutes and is eased up by resting or by placing a Nitro tablet under tongue, which helps in relaxing blood vessels and reduces blood pressure with resultant less demand for oxygen by heart muscles.
Pathophysiology of Angina
Angina develops due to myocardial ischemia and this happens when the coronary blood flow becomes inadequate to meet the oxygen demand of the heart muscle. In other words, angina occurs as a result of imbalance between the heart's demand and supply of oxygen. This imbalance results from an increase in demand (e.g. during physical exertion, exercise etc) without a proportional increase in supply of oxygen due to obstruction or atherosclerosis of the coronary arteries.
Classification and Types of Angina
- Stable Angina Pectoris: This is also known as effort angina and is one of the more common forms of angina. This type of angina is present when the patient is exerting himself e.g. running, brisk walking, climbing stairs, exercising etc. hence the name "effort angina." Symptoms abate following the cessation of activity or after taking medications such as Nitro. Stable angina is usually predictable.
- Unstable Angina Pectoris: This type of angina is not that common but is quite a serious condition when compared to stable angina. Symptoms are unpredictable, more intense, and are unrelieved with rest or medications. Unstable angina is a pain that starts even at rest, is of severe intensity, and not relieved by Nitro. It is an indication of heart attack and immediate medical attention is required. Unstable angina is also known as "crescendo angina."
- Microvascular Angina Pectoris: It has angina like chest pain, but the cause is unknown. Scientists believe the cause to be poor functioning of the small vessels (microvessels) of arms, legs and heart. These vessels don't have blockages in them thus leading to difficulty in diagnosis. The prognosis of microvascular angina is excellent.
Causes and Risk Factors of Angina
The main cause of angina by far is coronary artery disease. Coronary arteries are responsible for supplying oxygenated blood to heart muscles. Disease of these arteries leads to development of cholesterol deposits known as cholesterol plaques in artery walls. Accumulation of these hardened cholesterol plaques leads to narrowing of coronary arteries. This condition is known as arteriosclerosis. If narrowing continues to increase more than 50%, the coronary arteries will not be able to supply adequate oxygenated blood to heart muscles and will not be able to meet increased oxygen demand during physical activities such as exercise or at times of stress. This lack of oxygenated blood supply to heart muscles causes angina or chest pain. Arteriosclerosis is exacerbated by smoking, high blood pressure, elevated cholesterol, and diabetes.
One of the less common causes of angina is coronary artery spasms. The walls of arteries contain muscle fibers and contractions of these muscle fibers leads to spasm or constriction of arteries resulting in decreased blood supply and as a result angina. Angina caused by vasospasm is termed as Variant Angina or Prinzmetal's angina. These spasms can take place in normal arteries as well as those arteries affected by arteriosclerosis. Coronary artery spasm can also occur due to usage of certain drugs such as cocaine.
There are some causes of chest pain which are not due to lack of oxygen to heart muscles but due to other medical conditions and should be differentiated from angina. These are:
- Pulmonary embolism.
- Mitral valve prolapse.
- Aortic dissection.
- Nerve compression.
- Esophageal spasm/reflux.
- Depression and panic attacks.
Risk Factors of Angina
- Age (above 55 years for men, above 65 for women).
- Cigarette smoking.
- Diabetes mellitus (DM).
- Family History of premature heart disease.
- Kidney disease (microalbuminuria or GFR)
- Sedentary lifestyle.
Signs and Symptoms of Angina
Angina presents itself more as a chest discomfort, rather than frank pain, which is described as pressure, heaviness, tightness, squeezing, burning, or choking sensation. This discomfort is usually retrosternal in location and referred to back, neck area, jaw, and shoulders. Angina is usually precipitated by physical exertion, emotional stress and is relieved with rest and /or medication. Sometimes along with angina, the patient may also experience symptoms like indigestion, heartburn, weakness, sweating, nausea, cramping, shortness of breath, and pallor. A variant form of angina is Prinzmetal's angina which occurs in patients with normal coronary arteries. It is thought to be caused by arterial spasms.
Tests to Diagnose Angina
Tests like CT scan calcium scoring are very reliable in detecting small amounts of calcium in the plaque of coronary arteries. In the absence of atherosclerotic coronary artery disease CT scan comes up negative. Ultrafast CT scanning is useful in evaluating chest pain in younger patients (men under 40 and women under 50 years old). Other tests like exercise treadmill test, magnetic resonance imaging (MRI), electrocardiogram (ECG, EKG), coronary angiogram, stress echocardiography, stress thallium, cardiac catheterization, thallium scintigram or sestamibi scintigram etc. are also done to diagnose angina.
Treatment for Angina
The main aim of treatment is relief of symptoms, slowing the progression of disease and decreasing future anginal episodes and heart attack. Treatment for angina includes rest, medications like nitroglycerin which is placed under the patient's tongue. Nitroglycerin is a potent vasodilator which helps in dilation of the arteries thereby increasing the oxygen supply to heart muscles and relieving angina.
The Following Medications Can Also Be Used:
- Beta-blockers such as acebutolol, atenolol, bisoprolol, metoprolol, nadolol, propranolol, timolol, carvedilol.
- Calcium channel blockers: Amlodipine, bepridil, diltiazem, felodipine, isradipine, nicardipine, nifedipine, nimodipine, nisoldipine, verapamil.
If patients continue to have angina despite taking medication then depending on the severity and location of angina and atherosclerosis, surgical procedures like balloon angioplasty (percutaneous transluminal coronary angioplasty or PTCA with or without stents) or coronary artery bypass graft surgery (CABG) to increase coronary artery blood flow can be done.
Identifying and treating risk factors is also important in treatment and prevention of angina. Patients need to get tested for elevated cholesterol and other fats in the blood, diabetes and hypertension (high blood pressure) regularly. Other than this, they should be encouraged to stop smoking, follow a healthy diet and exercise regime and keep their weight under control.