Answer for November 28, 2012
2nd degree Type I/Mobitz 1/Wenckebach. Most Mobitz 1 is due to excessive vagal tone, and can be a normal finding in athletes and others with high resting vagal tone. It may be a transient dysrrhythmia in any circumstance with high vagal tone, like straining at stool. It usually does not require treatment, unless the patient is symptomatic. Atropine would usually be effective in improving heart rate. This type of 2nd degree block differs significantly from Mobitz 2, which is usually due to damage to infranodal pathways, and may require a pacemaker for treatment.