Sonomicrometric Studies on the Effects of Long-Term Pumping of Cardiac Assist Device on the Bulk and Regional Mechanics of the Normal Left Ventricle in Goat
Affiliations: Laboratory of Biomedical Control, Section of Scientific Instrumentation and Control, Research Institute of Electronics Science, Hokkaido University, Sapporo 060, Japan | Departments of Biomedical Engineering and Artificial Organs, National Cardiovascular Center Research Institute, Suita, Osaka 565, Japan | Department of Thoracic Surgery, Osaka Medical College, Takatsuki, Osaka 569, Japan
Note: [] Requests for reprints should be addressed to: Takao Nakamura, Ph.D., Cardiac Prostheses Res. Lab., C.W. 15, St. Vincent's Hospital, Victoria St., Darlinghurst, N.S.W. 2010, Australia.
Abstract: Pneumatically driven, diaphragm type left ventricular assist devices (LVADs) were implanted into 2 goats with normal hearts for approximately 1 month to study the effects of long-term pumping of LVAD on the cardiac mechanics. One sham-operated goat was used to obtain control data. Diameters and myocardial segment lengths of the left ventricle were measured with an ultrasonic displacement meter to calculate the bulk mechanical work (BMW) and regional myocardial mechanical work (RMW), respectively. The LVAD was pumped in the 2:1 drive mode (one counterpulsated pumping in every two cardiac cycles), and was temporarily driven in the 1:1 mode (one pumping in every cardiac cycle) or stopped to obtain the data under these conditions. During the second half of the post-operative period while the animal condition was stable, the BMW in the 2:1 and 1:1 modes were approximately 59% and 72% of that observed under the temporary pump-off condition (0.22 W/(lOO g)), respectively. The RMW in the 2:1 and 1:1 modes were 69% and 74% of that obtained during pump-off (6.2 mW/cm3), respectively. The myocyte diameter in the subendocardial layer was reduced by unloading effect of 1-month pumping, whereas those in middle and subepicardial layer showed little change.
Keywords: bulk mechanical work, chronic experiment, left ventricular assist device, regional mechanical work, ultrasonic displacement meter
