Posted by Donni McMasters on July 12, 1999 at 13:09:17
I am a 31 year old female with a consistantly low pulse rate. I have Hypothyroidism and I am on .075 mg Synthroid. I am not an athelete although I do try to keep up with my 2 small children. I had chest pains recently and was told that my EKG was normal but I had a low pulse rate. I asked the doctor if that would make me fatigued and he answered yes. He did not seem concerned. I feel tired all the time and was wondering if this is something that I should have looked at more closely. I do seem to feel lightheaded at some times but can go days without feeling it. I am currantly breast feeding an infant also. So I do know there are not many drugs that I can take at present. I check my bp regulary and it is below normal at about 110/60 most of the time. The highest my pulse has been after working outside or some activity is 60. I'm not sure as to the lowest it has gone.
Thank You for your time and consideration,
Posted by CCF CARDIO MD - CRC on July 12, 1999 at 14:22:53
Thank you for your question. Heart rate control is due to two influences. One influences the heart to speed up and the other to slow down. The "natural" or intrinsic rate of the heart free of all influences (i.e if the heart were placed by itself in a test tube) it about 100 beats per minute (BPM). The vagus nerve is the "brakes" on the heart. This nerve is under control of the parasympathetic nervous system (part of the nervous system we don't think about). The vagus nerve will slow the heart down to a typical rate of 50 to 90 BPM. Rates slower than this can be seen in athletes and in certain heart conditions. The "gas pedal" of the heart is due to the sympathetic nervous system. Various conditions such as exercise, fear, anger, etc. will cause the heart to increase its rate. The maximum heart rate that can be achieved is determined by age. A simple formula that can be used to determine maximum heart rate is 220 - age.
The a slow heart rate is not really "good or bad" but is based more on the physiology of the particular state of the heart. Certainly a fast heart rate during a brisk jog is "good" where that same rate during a nap may be considered "bad". Likewise a slow heart rate leading to any symptoms (i.e lightheadedness or fainting) would be considered bad but otherwise is not in and of itself a problem.
Information provided here is for general educational purposes only. Only your doctor can provide specific diagnoses and treatments. If you would like to be seen at the Cleveland Clinic, please Call 1 - 800 - CCF - CARE for an appointment at Desk F15 with a cardiologist.