Unstable Angina and Calcium Channel Blockers

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Unstable Angina and Heart Attack

Angina is a term used to describe the chest pain associated with heart disease related to a decrease in oxygen supply to the heart. Conditions like atherosclerosis, diabetes and hypertension are common causes of heart disease characterized by an imbalance in the blood and oxygen supply to the heart muscles and an increase in the demand for these.

Angina is usually characterized as a constricting or squeezing type of pain, sometimes just a heaviness or discomfort, but may also be like a stabbing, burning kind of pain. It is often associated with physical exertion or stress, usually lasting for one to five minutes and may be relieved by rest and nitroglycerine. However, when chest pains occur suddenly, even without exertion, gets worse, even with rest or nitroglycerine and lasts much longer than a few minutes the patient may be experiencing unstable angina. This is an ominous situation because a heart attack or a myocardial infarction may be evolving.

Treatment for Unstable Angina

Emergency treatment for unstable angina usually calls for immediate hospitalization with continuous monitoring. Because the need for oxygen supply to the heart is increased, supplemental oxygen must be given. Initial medical therapy consists of:

  • Anticoagulation and antiplatelet therapy to prevent stroke
  • Use of beta-blockers to decrease the workload of the heart
  • Use of nitrates to increase coronary blood flow

Further medical management may include the use of pain relievers (morphine), ACE inhibitors, statins and calcium channel blockers.

Unstable Angina and Calcium Channel Blockers

The use of calcium channel blockers in the treatment of unstable angina has been found to be controversial. Unlike beta blockers, drugs like verapamil and diltiazem have not been proven to decrease the risk for heart attack and death. This is why it is not in the first line of choice for emergency treatment of acute chest pains. However, according to the American Heart Association calcium channel blockers are very useful in preventing coronary spasms in variant or Prinzmetal’s angina, a type of unstable angina that usually occurs at rest.

Calcium channel antagonists, as these drugs may also be referred to, prevent and reduce the frequency and severity of chest pains due to coronary spasm. Sudden constriction or spasm of the coronary arteries decreases blood flow to the heart muscles and can cause immediate death of these cells. If severe, death from a heart attack can ensue. Calcium channel blockers like diltiazem (Cardizem, Dilacor XR) and verapamil (Calan, Isoptin SR) dilate or relax these blood vessels to allow blood and oxygen to reach these active heart muscle cells. They also prevent the spasms and decrease the total workload that the heart has to work against, thus decreasing oxygen demand while increasing oxygen supply.

Calcium channel antagonists may also be indicated if a patient cannot take beta blockers.

Possible side effects of calcium channel blockers include:

  • Irregularities in heartbeats
  • Decreased blood pressure
  • Headache, dizziness and flushing
  • Leg or ankle edema
  • Weakness
  • Tingling sensations in the extremities
  • Constipation
  • Skin rash

The aim of treatment of unstable angina is to prevent a full-blown heart attack or myocardial infarction that can result in death. The role of calcium channel blockers in cases involving coronary spasm that is not relieved by conventional treatment like beta blockers and nitrates is important. However, caution must also be exercised in its use, since there are other drugs that are considered more effective as first line treatment.


WebMD, “Calcium channel blockers for heart attack and unstable angina”, https://www.webmd.com/heart-disease/calcium-channel-blockers-for-heart-attack-and-unstable-angina

American Heart Association, “Angina Pectoris Treatments”, https://www.americanheart.org/presenter.jhtml?identifier=4496