טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentAvrahami Alon
SubjectDesign of a Myocardial Pacing System Based on Focused
Ultrasound
DepartmentDepartment of Biomedical Engineering
Supervisor Professor Emeritus Adam Dan
Full Thesis textFull thesis text - English Version


Abstract

Sudden cardiac death is one of the leading causes of death in the Western world. Each day approximately 1000 people in the United States suffer cardiac death. As many as 20 to 40% of these cases result from asystole- a state of no cardiac electric activity, with no contractions and no cardiac output. In these cases, the chances of successful revival are low- drug therapy has little success rate and de-fibrillation is usually not effective. External Cardiac Pacing, as a temporary measure until implantation of an internal pacemaker or another treatment is available, can be lifesaving.

External electrical cardiac pacing was demonstrated over 200 years ago, and has been commercially in use since 1952. The concept of running an electrical current through the chest is a simple-to-implement and reasonably-effective process, yet it is not without its flaws.  Chief among these are the extreme pain caused to the receiving patient and the obstruction of ECG measurements, making pacing effectiveness questionable and difficult to determine.

On the other hand, the phenomenon of Mechano-Electric Feedback has been known for some time. Direct mechanical stimulation to the heart was seen to cause cardiac contractions. However, the underlying biological mechanism remains unclear to this day.

 Evidence also suggests that ultrasound-induced pressure changes can cause various cardiac effects, albeit only on rare occasions and in extreme conditions.

In this study, a hypothesis was suggested in which the effect of ultrasound pulses on myocardial cells could be harnessed and used as an alternative method for external myocardial pacing. During the study, a system was designed to serve as a proof-of-concept, demonstrating the feasibility of an external ultrasound-based pacing system. The proof-of-concept goal was to be able to use the device to induce premature cardiac beats in a healthy heart upon demand.

The system was built utilizing High-Intensity Focused Ultrasound and according to optimization guidelines, and was tested both in-vitro and in-vivo in a series of experiments to validate its effectiveness.

The device was able to generate premature beats, but could not do so systematically upon-demand. The results indicate that while such a pacing system may indeed be feasible, further improvements in the field of cardiac tracking and targeting are required.