Development of a new activity-input-type ambulatory electrocardiogram and its clinical usefulness

There are some problems with interpretation of the results of ambulatory electrocardiographic monitoring of patients with angina pectoris. To eliminate some of these difficulties, we developed a new activity-input-type ambulatory electrocardiogram which could simultaneously record the electrocardiogram and the patient's activities. Daily activities were classified into 8 levels from lying down to running or climbing a slope, in order to record them as analyzable square waves. Accuracy of the activity input to this equipment in 10 patients with effort angina was good, with 86.7% accuracy for eating and 91.7% for defecation. A comparison was made between the first and second recordings of daily activity changes in each exertional level. The numbers, mean duration and maximum duration of actions in each level were not always equal, and often changed between the two recordings. Maximum ST depression in each exertional level showed a favorable correlation of r = 0.931 (by 1.76 +/- 0.59 vs 1.77 +/- 0.66) between the first and the second recordings. The descriptions of activities recorded in patients diaries are unreliable indicators of time, because subjects check the time sometimes during, and sometimes after, the actions concerned. This equipment can easily make real-time recordings of such information, and thus provide advantages in research. When observing the pathologic condition of patients with angina pectoris and evaluating anti-anginal drug efficacy, information on the activity of each patient is important. This equipment therefore contributes to improving problems of ambulatory electrocardiographic monitoring for the patients with angina pectoris.