ST analysis of Holter tapes.

In recent years, it has become increasingly clear that for an important subset of patients with coronary artery disease, many or all of their ischemic episodes are not accompanied by anginal pain. For these patients, it is desirable to detect these ischemic episodes as periods of ST-segment depression on Holter tapes. In the past, such detection has been difficult because the analysis methods were artifact-sensitive and failed to differentiate ischemic from nonischemic ST-segment changes. This work describes a new ST-segment analysis algorithm that has been added to the existing computer-based Holter analysis system. This system is highly artifact-resistant and has been designed to minimize the loss of processing speed while maintaining extremely high accuracy.

Comparison of amplitude-modulated (direct) and frequency-modulated ambulatory techniques for recording ischemic electrocardiographic changes.

Continuous ambulatory electrocardiographic monitoring of ST-segment configuration has become a useful technique for evaluation of myocardial ischemia. Concern that direct or amplitude-modulated (AM) recording and playback systems have inherent limitations that cause inaccurate ST-segment recordings has led to preference for frequency-modulated (FM) devices. To determine the accuracy of AM and FM ambulatory electrocardiographic systems, the signal was compared from the same set of 2 bipolar leads simultaneously recorded by standard electrocardiography and AM and FM recorders in 14 patients during treadmill exercise. Also, simultaneous AM and FM recorders were compared in 9 ambulatory patients in 16 monitoring sessions. The AM recording system accurately reproduced ST segments recorded during treadmill exercise (range 4.0 mm of ST-segment depression to 2.0 mm of ST elevation) when measured at the J point (r = 0.91, p less than 0.0001), and 0.08 second after the J point (r = 0.95, p less than 0.0001). FM recording was equally accurate (r = 0.89 and 0.95, respectively, p less than 0.0001). Similarly, during ambulatory recording, the AM technique accurately recorded maximal ST depression in each episode as recorded by the FM device (28 episodes, range 0 to 3 mm of ST depression, r = 0.85, p less than 0.0001). Both AM and FM ambulatory electrocardiographic systems can accurately reproduce ST-segment deviation associated with ischemia and can be used to monitor transient ST-segment changes in patients with coronary artery disease.

A 60x computer-based Holter tape processing system.

Since its introduction in 1968, the basic algorithm for automatic recognition of ventricular ectopic depolarizations, developed at Worcester Polytechnic Institute, has been implemented and modified by a number of investigators. The modified multi-template algorithm is conceptually similar to the original algorithm except that there are eight templates stored for each patient. A new template is stored whenever the match with each of the old templates yields a correlation coefficient less than 0.79. The system reads a Holter tape at 60 x real time for heart rates of 80 beats per minute, with relatively few false positives.

Cardiovascular monitoring in the coronary care unit.

The present status of cardiovascular monitoring in the coronary care unit is reviewed. Major emphasis is placed on electrocardiographic monitoring, the only form of monitoring used on most patients who have suffered recent myocardial infarction. The capabilities and limitations of computer systems to perform electrocardiographic monitoring are reviewed, as are present techniques for hemodynamic monitoring and computerized integration of electrocardiographic, hemodynamic, and other patient data.