Beta-Blockers and Calcium Channel Blockers
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Direct answer
Beta-blockers and calcium channel blockers are drugs for hypertension, angina and arrhythmias that act on the heart and vessels through different receptors and channels. Beta-1 selective blockers such as metoprolol and bisoprolol are preferred in heart failure with reduced ejection fraction, while dihydropyridines such as amlodipine suit hypertension and angina. Non-dihydropyridines such as verapamil are avoided in heart failure with reduced ejection fraction because they depress contractility.
What you must remember
- Selectivity: propranolol is non-selective, metoprolol, atenolol and bisoprolol are beta-1 selective, and carvedilol and labetalol also block alpha-1 receptors.
- Beta-blocker indications: post-myocardial infarction, heart failure with reduced ejection fraction, angina, atrial fibrillation rate control, portal hypertension (propranolol) and migraine prophylaxis.
- Beta-blocker cautions: asthma (non-selective agents are avoided), symptomatic bradycardia, heart block and decompensated heart failure.
- Beta-blocker adverse effects: fatigue, bradycardia, bronchospasm, masking of hypoglycaemia and rebound tachycardia on abrupt withdrawal.
- Dihydropyridines: amlodipine, nifedipine and felodipine are vascular-selective, causing reflex tachycardia, ankle oedema and gingival hyperplasia; amlodipine is neutral in heart failure.
- Non-dihydropyridines: verapamil and diltiazem slow atrioventricular conduction, useful in supraventricular tachycardia and rate control, and are avoided in heart failure with reduced ejection fraction.
- Interactions: verapamil or diltiazem with a beta-blocker risks heart block, and CYP3A4 inhibitors such as clarithromycin raise amlodipine levels.
A decision sequence for cardiac patients
A 58-year-old man with stable angina and hypertension asks whether a beta-blocker or a calcium channel blocker suits him better. The choice depends on heart rate, ejection fraction, airway disease and co-medication, and the steps below set out the order.
- Check the heart and the airway: assess ejection fraction, heart rate, atrioventricular conduction, and any asthma or COPD before selecting a class.
- Match the indication: beta-blockers suit post-infarction patients, heart failure with reduced ejection fraction and rate control, while dihydropyridines suit hypertension and angina with normal heart function.
- Consider a non-dihydropyridine: verapamil and diltiazem slow conduction and help supraventricular tachycardia and rate control, but are avoided in heart failure with reduced ejection fraction.
- Check interactions: combining verapamil or diltiazem with a beta-blocker risks heart block, and co-prescribed CYP3A4 inhibitors raise dihydropyridine levels.
- Titrate and watch side effects: monitor heart rate and blood pressure, expect fatigue and ankle oedema, and watch for bronchospasm and masked hypoglycaemia in diabetics.
- Taper rather than stop: withdraw beta-blockers gradually over days to weeks, since sudden stopping can cause rebound tachycardia and ischaemia.
High-yield viva angles
Viva questions usually test whether the drug suits the heart's pump function and the airway.
- Trap: giving verapamil or diltiazem in heart failure with reduced ejection fraction Correct: these are negative inotropes that worsen the pump, so amlodipine or an evidence-based beta-blocker is used instead.
- Trap: using a non-selective beta-blocker in asthma Correct: blocking beta-2 receptors causes bronchospasm, so non-selective agents are avoided in asthma.
- Trap: choosing propranolol as routine first-line therapy for uncomplicated hypertension Correct: propranolol is non-selective and reserved for specific indications such as portal hypertension and migraine prophylaxis.
Frequently asked questions
Why are non-dihydropyridine calcium channel blockers avoided in heart failure?
Verapamil and diltiazem are negative inotropes that depress myocardial contractility, which worsens heart failure with reduced ejection fraction. Amlodipine, a dihydropyridine, is neutral and can be used in heart failure. Evidence-based beta-blockers are preferred for the heart failure itself.
Which beta-blockers are used with caution in asthma?
Cardioselective beta-1 blockers such as metoprolol, bisoprolol and atenolol are used with caution in asthma, since they have less effect on beta-2 receptors in the airway. Non-selective agents such as propranolol are avoided because they can precipitate bronchospasm. Any asthma patient needs close monitoring when a beta-blocker is started.
Why do dihydropyridines like nifedipine cause reflex tachycardia?
Nifedipine causes arteriolar vasodilation that lowers blood pressure, and the baroreflex responds with a rise in heart rate. Amlodipine has a slower onset and is less likely to cause this. Ankle oedema is a separate, dose-related effect of dihydropyridines.
Why are verapamil and diltiazem dangerous when combined with beta-blockers?
Verapamil and diltiazem slow atrioventricular conduction, and beta-blockers add further nodal depression. The combination can cause severe bradycardia or heart block in susceptible patients. Combined use requires careful monitoring or should be avoided.