Automated Analysis of the Esophageal Accelerogram as a Minimally Invasive Monitor of Manifest Contractile State

Abstract

Automated real-time monitoring of the heart’s relative contractile state was achieved simply and cost effectively through automated analysis of the esophageal accelerogram (EA) and electrocardiogram (ECG). Previous work showed that the first major complex of the EA contains information which is a sensitive indicator of the left ventricle’s mechanical activity. An automated system was developed around a small, inexpensive, personal computer through the application of current software engineering design and implementation techniques. The resulting system has freed the physician from tedious, time consuming data analysis in the operating room. The ECG and EA analog signals are obtained from conventional physiologic monitors and processed by the system to yield an index of the relative contractile state every five seconds. This discrete index is trended along with heart rate (HR) by plotting the last twenty minutes of data. In addition, the most current numeric values of HR and the contractile index are presented. The system is contained on a single cart, and therefore, is easily rolled into the operating room (OR). Operation of the system was designed to be simple and unoccupying in the sometimes hectic environment of the operating room. System performance was tested and found to be accurate when supplied with correct analog signals. Electrocautery device generated electromagnetic interference of the ECG or EA caused the system to produce an appropriate error message and “hold” until an acceptable signal was obtained. Due to the minimally invasive nature of the esophageal probe, monitoring of the heart’s relative contractile state is performed on a routine basis with minimal risk to the patient.