Sinus arrhythmia. 1. Data and patterns from groups of individuals followed from 1 month to 23 years of age.

eration and deceleration of the heart usually associated with respiration, but oc casionally found with digitalis intoxication1 or due to other causes. This paper will dis cuss only the respiratory form of sinus ar rhythmia2 first described in 1847 by Lud wig. Though no textbook on pediatrics or cardiology fails to include a paragraph or two on sinus arrhythmia, there has been surprisingly little information collected on this subject, so that in these brief discus sions some erroneous or inadequately tested impressions have been perpetuated for 50 years.