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
- Tingling sensations in the extremities
- 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.