How Do Beta Blockers Benefit Patients With Angina?

angina
Angina. Science Photo Library/Getty Images

Beta blockers have many uses in medicine. One of the most important is in the treatment of patients with coronary artery disease (CAD) and angina.

How Do Beta Blockers Benefit Patients With Angina?

In patients with stable angina caused by CAD, beta blockers are considered first-line therapy.

In stable angina, one or more of the coronary arteries is partially blocked by an atherosclerotic plaque.

Typically, the heart muscle supplied by the diseased artery gets enough blood flow during periods of rest. But during exercise or periods of stress, the partial blockage prevents the blood flow from increasing sufficiently to supply needed oxygen to the working heart muscle, and the muscle becomes ischemic (starved for oxygen). As a result, angina occurs.

Beta blockers work by blocking the effect of adrenaline on the heart. This has two major beneficial effects in patients with angina:

  • Slowing of the heart rate, in particular during periods of exercise or stress.
  • Reducing the force of heart muscle contraction.

Both of these effects reduce the amount of oxygen needed by the heart muscle, and ischemia (and angina) are delayed or prevented as a result.

What Is The Effect Of Beta Blockers In Patients With Angina?

In patients with angina, beta blockers are often very effective in improving the intensity or duration of exercise that can be performed without developing ischemia or angina.

Patients with stable angina who take beta blockers usually experience a noticeable diminishing of episodes of angina and have to take nitroglycerin less often.

In addition, in patients with angina who have had a myocardial infarction. (heart attack), beta blockers are the only anti-angina drugs that have been shown to reduce the risk of having another myocardial infarction.

Furthermore, in survivors of a myocardial infarction, or in patients who have heart failure in addition to stable angina, beta blockers have been shown to significantly improve overall survival.

The benefits provided by beta blockers have made them the drugs of first choice in treating patients with CAD and stable angina.

Side Effects of Beta Blockers

The main side effects of beta blockers include bradycardia (slow heart rate), breathing difficulties in people who have asthma or chronic lung disease, fatigue, worsening of symptoms of peripheral artery disease, depression, and erectile dysfunction. Beta blockers should also be avoided in patients with angina due to Prinzmetal's angina (coronary artery spasm), since in these patients beta blockers can occasionally cause more spasm.

Many of these side effects can be avoided in patients with angina by using beta blockers that work primarily on the heart itself, and that have relatively little effect on the blood vessels, lungs, and central nervous system.

These "cardioselective" beta blockers are Tenormin (atenolol) and metoprolol (Lopressor, Toprol XL).

Sources:

Fihn SD, Gardin JM, Abrams J, et al. 2012 ACCF/AHA/ACP/AATS/PCNA/SCAI/STS guideline for the diagnosis and management of patients with stable ischemic heart disease: a report of the American College of Cardiology Foundation/American Heart Association task force on practice guidelines, and the American College of Physicians, American Association for Thoracic Surgery, Preventive Cardiovascular Nurses Association, Society for Cardiovascular Angiography and Interventions, and Society of Thoracic Surgeons. Circulation 2012; 126:e354.

Continue Reading