Gettysburg Medical News
 The Clinical View
 by P.E. Hoffsten, MD
11 January 2006

HOW FAST SHOULD YOUR HEART BEAT?

            The lady was 76 years old and had a history of emphysema.  She was in the hospital being treated for pneumonia and seemed to be recovering without incident.  One evening without warning, her pulse suddenly jumped from 74 beats per minute to 125 beats per minute.  She was not exercising, had not been startled, was not having any discomfort before the event began and had no previous history of a fast heartbeat.  Over the course of about 10-15 minutes with this fast heartbeat, she began to develop chest discomfort.   An electrocardiogram was checked and showed a very regular heart beat but no evidence of a “heart attack” or a threatened heart attack.

            Instead, she had what is medically called “SVT”.  These are initials for supraventricular tachycardia.  Supraventricular is a word meaning that the rhythm of the heart was originating from the upper part of the heart which is the safer origin for the rhythm of the heart.  So called “ventricular tachycardias” are dangerous and often fatal but supraventricular tachycardias are a nuisance, although not dangerous.  They make the person feel bad because the heart out put drops significantly when the heartbeat is so fast that the heart doesn’t have time to fill up between heart beats.  Therefore, each heartbeat, although more rapid, puts out just a small amount of blood and the person feels terrible.

            Fortunately, now there is a very quick and easy way to treat the type of supraventricular tachycardia that this lady had.  A simple injection of a medication called Adenosine converts the rhythm in about 15 seconds back to a normal rhythm. The heartbeat is re-established in a normal manner and the sensations of discomfort resolve.  But the problem is that the fast heartbeat has been going for several hours and there may be a prolonged fatigue for a day or two after this.  But if it has only been for a short time, there will be no after effects.

            The type of supraventricular tachycardia this lady had is relatively common in young women who have no other illness or heart problem.  Often times, these individuals can be treated with a medication to prevent the recurrent fast heartbeat.  The healthcare providers at your local clinics are aware of this problem and can help provide guidance on how to prevent and how to treat the fast heartbeat when it comes.

            The answer to the question in the title above is dependent upon a number of factors.  For normal adults, the normal heartbeat is between 60-100 beats per minute.  Well-trained athletes and especially swimmers can have a resting heartbeat in the 40’s and be perfectly healthy.  John Landy, the very first man to run a 4-minute mile, was in outstandingly good condition with a resting heartbeat of 32 beats per minute.  For adults in their 50-60’s, heartbeats in the 40’s are usually a sign of the clock that runs the heart not being fast enough and a pacemaker will probably be needed at some point.

            On the other end of the spectrum, heartbeats faster than 100 per minute in a resting state are very abnormal.  For a human being exerting heavily, heartbeats can go up as high as 150-180 beats per minute.  The reason for these very rapid heartbeats in a person exercising so hard, is that the return of blood to the heart is stimulated by the muscular action of the exercise being carried out.

            There are other causes of supraventricular tachycardia than the type mentioned above.  One is called atrial fibrillation and is a very inefficient rhythm that is very uncomfortable for most people that have it.  This rhythm usually requires special considerations and treatments to prevent or control it.  Again, the healthcare professionals at your local clinics are very skilled at recognizing and treating this type of problem or obtaining help from cardiologists when needed.