Pearls of Wisdom: Reducing the Residual Burden of Angina
John, a 56-year-old man with chronic stable angina, has been treated with metoprolol tartrate (Lopressor) 50 mg twice per day for several years and is tolerating that dose well.
He describes his angina control as “pretty good”, but reports that with sexual activity, exercise, and sometimes postprandially he experiences some angina. Activity-related symptoms do not appear to be worsening, and are only mild-moderate in intensity, but he wants to know if there is anything he might do with his medication to further reduce or eliminate symptoms.
Specifically, he asks whether it is worth increasing the dose of beta-blocker. His blood pressure is good (130/80 mm Hg), and his resting heart rate is 68 bpm. He is not experiencing any adverse drug effects from the beta-blocker. He is already taking appropriately chosen medications including an ACE inhibitor, statin, and aspirin.
What might be a way to reduce his residual burden of angina?
A. Switch to propranolol
B. Don’t adjust the beta-blocker, but add diltiazem
C. Switch to atenolol
D. Titrate the metoprolol to a resting heart rate of <60 bpm, and if still symptomatic to an exercise heart rate <125 bpm.
What is the correct answer?
(Answer and discussion on next page)
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Answer: Titrate the metoprolol to a resting heart rate of <60 bpm, and if still symptomatic to an exercise heart rate <125 bpm
Beta-blockers, such as metoprolol, are commonly chosen as first line treatment for angina. Since many of the patients who have angina have also experienced an myocardial infarction (MI), but-MI prophylaxis with beta-blockers is appropriate, and thereby reduces future MI risk as well as reducing angina.
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Duration of Treatment with Beta-Blockers
Curiously, it is only in the last few years that experts have spoken out about how long to administer beta-blockers post-MI. In an era where we are closely scrutinizing antiplatelet therapy following acute coronary syndromes, and have specific guidelines down to the number of months they should be administered (typically 3-12 months, depending upon stent type, for instance), little has been said about the duration of beta-blockers post-MI.
You may be surprised to learn that clinical trial data confirming post-MI beta-blocker efficacy only goes out about 3.5 years, after which it isanyone’s guess whether or not beta blockade is beneficial. When beta-blockers are well tolerated (and inexpensive), it is not so troubling to continue them long-term, especially since abrupt discontinuation of beta blockade can precipitate myocardial ischemia. When beta-blockers cause excessive fatigue, exercise intolerance, sexual dysfunction, or meaningful metabolic disturbances, the lack of confirmation that beta-blockers provide risk reduction past 3.5 years becomes more problematic.
Our patient has not had an MI, but does have angina, which has been “pretty well” controlled. He is asking what the options are for reducing residual angina burden, and is already taking other appropriate pharmacotherapy for persons with demonstrated coronary artery disease. He specifically inquired about increasing the beta-blocker dose. Should we?
Titrating Beta Blockade in Angina1
Stephen Glasser, MD has pointed out that as many as 15% of person treated to a resting heart rate of 60-70 bpm are not fully beta blockaded, as manifest by the fact that they achieve exercise heart rates greater than 125 bpm.1
So, his initial suggestion is to titrate the beta-blocker to a resting heart rate of 50-60, if angina symptoms persist with a resting heart rate of 60-70 bpm (predicated on no deterioration of drug tolerability at the higher dose).
What is Maximum Beta Blockade in Angina?1
Confirming this approach, Dr. Glasser studied 25 patients with persistent angina despite beta blockade and suppressed resting heart rate. He titrated the beta-blocker dose until the exercise heart rate was <125 bpm, after which most of the patients demonstrated improved control of angina
What’s the “Take Home”?
If angina symptoms persist despite initial beta blocker dosing, it may be worth a trial of titrating the beta blocker to an appropriate exercise heart rate (target = <125 bpm) rather than just using resting heart rate as a guide.
Glasser SP. Currently Recommended Drug Therapy for Persistent Angina. Contemporary Internal Medicine. 1992;May:17-26