Effects of cardiac assist on the bulk and regional mechanics of the ischemic left ventricle in dogs.
Pneumatically driven left ventricular assist devices (LVADs) were implanted between the left atria and the descending thoracic aortas of dogs and were counter-pulsated synchronously with the electrocardiogram at 1:1 and 2:1 duty ratios. Seven pairs of miniature sonomicrometers were implanted into the left ventricle (LV) to measure the LV muscular length and diameter. Ischemia was induced by the ligation of the left anterior descending coronary artery (LAD). Bulk and regional mechanical work were calculated from these dimensions and the left ventricular pressure. LVAD reduced the bulk work in the ischemic and normal hearts not only in the 1:1, but also in the 2:1, pumping modes. The left ventricular bulk work measured under the pump-off condition decreased progressively until around 2 h after the LAD ligation, and thereafter, it became constant. The regional myocardial work in the normal area of the ischemic heart was significantly decreased by the LVAD pumping (by 55%), whereas that in the ischemic area remained at near zero level regardless of pumping or nonpumping. The results obtained indicated that LVAD is useful not only to rest the severely damaged natural heart, but also to maintain the viability of ischemic myocardium.
Nakamura
T
T
Department of Biomedical Control, Hokkaido University, Sapporo, Japan.
Hayashi
K
K
Seki
J
J
Nakatani
T
T
Noda
H
H
Fukuda
S
S
Takano
H
H
Akutsu
T
T
D000818:Animals; D003327:Coronary Disease / Q000503:physiopathology*; D004285:Dogs; D005260:Female; D006352:Heart Ventricles / Q000503:physiopathology; D006353:Heart-Assist Devices; D008297:Male; D009200:Myocardial Contraction / Q000502:physiology*; D014463:Ultrasonography / Q000295:instrumentation / Q000379:methods