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Cardiovascular care news and articles from our expert team

Starting betablockers?

Posted on Thursday March 21, 2024 in Heart Health

An article by Dr Edward Leatham, Consultant Cardiologist, author of The Naked Heart  a series of simple blog and video explanations covering all of the main common medical conditions that can affect us, as we age.

Beta blockers work on the beta receptor situated on the surface of cells that are affected by circulating adrenaline which the body releases in times of stress. Small amounts of adrenaline circulate, even at rest and help determine the resting heart rate and cardiac output. They also have a direct action on the Sinoatrial node which sets the heart rate and the AV node, which becomes very important in patients prone to atrial fibrillation and flutter. Beta blockers have been developed over 50 years and are used to treat a wide range of conditions, including palpitations due to arrhythmia, high blood pressure, anxiety, migraine to name just a few. For a cardiologist, beta blockers are a commonly used medication, possibly because we live in a high stress world and patients come to us with symptoms that are often improved by taking blockers. Cardioselective beta blockers are more popular as they are far less likely to trigger bronchoconstriction or asthma. Here are a few points that are often raised by our patients.#cardiologist #afib #beta-blockers

Cardioselective Beta Blockers

  • work by competitive inhibition of beta receptors on the heart, which normally bind adrenaline
  • This ‘blocks’ or dampens adrenaline activation of the heart
  • Beta blockers thus lower the heart rate as well as peak contractility of the heart pump.
  • They are widely used to prevent and moderate heart rhythm disorders and to treat heart failure.
  • They also work as a ‘chill pill’ to lower adrenaline effects caused by anxious thoughts

Dose range

Everyone is wired differently, so to find the best dose, your doctor will often oversee a trial of various doses to find one that suits. The optimum dose of beta blocker to take varies between individuals For Bisoprolol (Cardicor) it varies from 1.25 mg to 10 mg once a day. It is normal when starting to notice a few days of slowing down as the body adjusts Upto 1 in 20 people find even the smallest dose makes them feel lethargic.

How do healthcare professionals (HCPs) find the best dose?

For Bisoprolol, we often start at the lowest dose of 1.25 mg taken every morning on 1st rising. Due to its long half life, it will then take up to 3 days to be steady state Assuming a normal pre treatment pulse or heart rate in range 60-90 beats per minute (BPM), we then look for a drop in heart rate to roughly 45-55 BPM. If the pulse rate exceeds 55 BPM your HCP may then advise you to increase by an extra 1.25 mg each morning.

Whats the dose range of Bisoprolol used in my patients?

As a rough, non audited or precise guide, I would say that the most popular dose is Bisoprolol 2.5 mg for woman and 5 mg for men, however there is a wide range of repsonses: 20% of patients only manage 1.25 mg once a day. 10% of patients require 10 mg once a day:

I have a low resting heart rate, can I take beta blockers?

Your resting heart rate is determined by several factors including the vagal nerve. Some people have high resting vagal nerve activity which produces low resting heart rate. You can tell, by assessing how your heart rate rises on exercise (when vagal tone is switched off). This means that some patients with low resting heart rates will still be offered beta blockers (only after an ECG) to moderate symptoms of palpitation or to temper heart rate response to exercise

Be aware

Once you take a betablocker it is perfectly normal for your heart rate to drop as low as 35 BPM overnight during sleep. Heart rate monitoring devices like Apple watch will often alarm if the heart rate drops. Providing there is no heart block showing on your regular ECG and you feel fine, there is no need to be concerned about low heart rates at night. Your heart rate response to exercise will be damped

If you are taking too much

If the dose is too high or you are intolerant to beta blockers you will feel less well after day 2, in which case its best to go back to the previous dose you felt fine on, or stop it until advised If you have blackouts or major dizzy spells you should get urgent medical advice and may need to stop the beta blocker

If you are taking too little

If the dose is too low you will notice very little change in your resting heart rate. Only when your pulse rate drops from your normal into the range 45-55 BPM have you reached the effective beta blockade zone.

  • Once on beta blockers, the normal algorithms used to calculate target heart rate for aerobic exercise are messed up, and cannot be used.
  • As a guide, exercise to high level to get hot and sweaty, red in face, take your pulse- insead of 150-160 it may only be 90-110 BPM.
  • Thats your new target heart rate to work to!

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