There are a number of medical disorders that can slow down the pulse below the normal rate and which, as a result, may also induce palpitations.
• Medication: Digitalis, the drug that is commonly used to control irregular heart beats, may cause slow pulse. Also, the beta-blockers, such as inderal, atenolol, commonly used for a range of disorders including high blood pressure, angina, anxiety, migraine and abnormal rhythms of the heartbeat, also slow the pulse.
• Hypothyroidism: Low levels of thyroxine, the hormone produced by the thyroid gland, causes a pulse rate steadily below 60, although in a very fit person the rate could be as slow as 40 (the other symptoms of hypothyroidism include weight gain, constipation, mental and physical inactivity, lethargy, thinning of hair and dry skin).
• Heart Block: If your pulse rate is below 60 and physical strain makes you feel dizzy and senseless, this suggests a heart block. (The messages transmitted by the conduction system of the heart sometimes fail to get through from their source in the upper chambers of the heart to the lower ventricular chambers. As a result, the muscles of the ventricles will not contract as often as they should.)