Your 85 Year Old Patient Has a Heart Rate of 70

Multiple Choice

Your 85 year old patient has a heart rate of 70 BPM. Analysis of the ECG reveals a slightly irregular rhythm with one P wave preceding each narrow QRS complex. The appearance of the P waves appears to change as often as from beat to beat. This is likely the result of:

A) early beats arising from the atria.
B) AV heart block.
C) an enlarged left atrium.
D) a changing pacemaker site.