Of the 5209 original Framingham Heart Study subjects,
1825 attended the 18th examination and 1028 had an
ambulatory ECG. A total of 292 subjects were excluded
for reasons listed in Table 2. Excessive artifact was the
major reason (n= 160) for exclusion. Clinical characteristics
of the 736 eligible subjects are presented in Table 3.
The mean age of subjects was 72 years (range, 63 to 93);
there were 297 (40%) men. A history of myocardial
infarction was present in 68 subjects (9%) and a history of
congestive heart failure in 13 subjects (2%). The clinical
characteristics of eligible subjects were remarkably similar
to those of examined subjects who did not have ambulatory
monitoring (n=796) and also to subjects excluded for
rhythm, artifact, or medication use (n=292) except that
eligible subjects were about 2 years younger and had about
two beats per minute lower heart rate (on 12-lead ECG)
than the other groups.