I"m 70 and had a pulse reading of 42. What could cause this?

Patricia Smith,

Thanks for your question. 

This pulse rate is low for any age and will need to be checked by your physician.  I suggest you call and make an appointment to be seen in as soon as possible.  If you have any symptoms of dizziness, light-headedness, vision changes, or the feeling that you might pass out, you should go to the emergency room.

There a few factors to consider when the pulse rate is low.  The first is the pulse rate may not be low, and the patient may be having "extra" heart beats which is actually early contractions of the heart.  These early beats are often not felt when taking a pulse, and not detected by a machine as there is insufficient blood pumped during that early beat.    When these early beats are taken into consideration, the pulse is actually higher.  An electrocardiogram will help determine this, and sometimes a 24 hour monitor of the heart is needed to "catch" the slow rhythm or abnormal beats.

Another factor is medication which can slow the heart rate.  The most common medication is beta blockers (propranolol, metoprolol, atenolol).  People react differently to these medications, and in some, they can slow the heart too much.  There are other medications that can have the same effect, and your doctor will help sort this out.

And the last situation is that your natural pacemaker has slowed down to a point that a pacemaker might be needed to ensure that your pulse does not slow too much.  There are other abnormal rhythms of the heart that manifest as a slow heart rate, something your doctor will be able to determine easily with an electrocardiogram.

I hope this has been helpful.

Martin Cane, M.D.