Ultrasonic imaging of myocardial vibrations associated with coronary artery disease

Coronary artery disease (CAD) is a major cause of mortality in the western world. Although progress has been made in recent years for the noninvasive diagnosis of CAD, a widely available, inexpensive and effective diagnostic solution remains elusive. We have developed a novel ultrasound-based technology to detect and analyze the myocardial vibrations associated with diastolic murmurs produced by CAD. Conventional ultrasound imaging systems suppress these vibrations. We have developed algorithms to process the raw ultrasound data and isolate these vibrations and integrated them into a programmable ultrasound system for real-time vibration imaging. In preliminary results from clinical studies of patients with CAD, we have observed localized areas of vibrations in the neighborhood of the stenosed coronary artery. The vibrations are narrowband with frequency > 200 Hz, and appear to have harmonic components, thus indicating resonance phenomena potentially with nonlinear mechanisms involved. No such vibrations were observed in normal subjects. Analysis of myocardial vibrations could provide a noninvasive diagnostic test for CAD that overcomes many of the limitations of conventional noninvasive tests. Potentially, this technology could provide a new way of evaluating CAD and cardiac function.