Continuously Recorded Physical Activity Level During Myocardial Ischemia Detected by Ambulatory Electrocardiography

Background The goal of the study was to establish the usefulness of a new device, the Actograph, to differentiate the causes of ischemia detected in ambulatory Holter monitoring. Twenty‐five patients (7 women, 18 men) with angiographically proven coronary artery disease and stable effort angina were evaluated. Methods Patients had their physical motor activity (PMA) registered by means of an Actograph simultaneously with Holter monitoring during 24 hours when they underwent a standardized bicycle exercise test and performed their usual daily activity with mandatory walking and stair climbing. Results Nineteen of 25 patients had 97 transient ischemic episodes (TIEs) in the postexercise monitoring period (5.1 episodes/patient and 91.5 min/patient). Seventy‐four TIEs were associated with a high heart rate (HR) increase and evidence of PMA. Seven TIEs occurred without HR increase, but with evidence of considerable physical exercise. During 13 TIEs there was HR increase without any proof of physical activity. In only three TIEs there was neither HR increase nor measurable PMA. Patients’activity period during 24 hours extended from 19.6%–48.9% of recording time. The higher the patients’activity level during the 24‐hour period, the higher the number of TIEs were noted (r = 0.57, P < 0.03). Increased activity was recorded in patients’diaries only during 51(69%) of TIE with evidence of increased HR and PMA. Patients who had only asymptomatic TIEs on the ambulatory ECG had significantly higher PMA than patients without ischemia during Holter monitoring (26% vs 33%; P < 0.001). PMA during walking was significantly higher than during bicycle exercise and climbing stairs (P < 0.001). Surprisingly, the physical activity episodes with lowest PMA, bicycle exercise testing, in all cases were accompanied by TIE, while activity episodes with highest PMA, walking, provoked TIEs only in 40% of cases. There is clearly no correlation between activity measured by the Actograph and HR increase during cycloergometer tests (R2 = 0.08), while stair climbing and walking shows good correlation (R2 = 0.6). Conclusions The Actograph is a useful device that gives additional insight into the pathophysiology of ischemia. The weakness of the method is lack of the ability to measure intensity of physical activity.