Chronic effects of a cardiac assist device on the bulk and regional mechanics of the failed left ventricle in goats.
Pneumatically driven, diaphragm-type left ventricular assist devices (LVADs) were implanted into 8 goats with profound induced infarction to the left ventricle by using multiple ligations of the left anterior descending (LAD) coronary artery as well as small arteries in the LAD distribution area. Left ventricular diameters, regional myocardial segment lengths, and wall thicknesses were measured by sono-micrometers. After left ventricular function seemed to be recovered, the goats were weaned off the LVADs after a gradual decrease of pump bypass flow over several days. Thereafter, hemodynamic and cardiac parameters were observed for about 1 month more. Three animals recovered successfully owing to the LVAD pumping. Before starting pump-weaning procedures, the bulk mechanical work (BMW) done by the left ventricle during LVAD pumping and under temporary pump-off conditions was 0.08 +/- 0.01 (mean +/- SE) and 0.22 +/- 0.01 W/100 g left ventricular weight (LVW), respectively, while the regional mechanical work done by the normal myocardium (RMWn) was 1.5 +/- 0.4 and 4.3 +/- 0.9 mW/cm3 during pumping and under temporary pump-off conditions, respectively. BMW and RMWn values obtained under pump-on conditions both increased gradually during the weaning process. Even after pump removal, they continued to increase and reached constant values of about 0.3 W/100 g LVW and 10 mW/cm3, respectively, around 2 weeks after pump removal. Although the myocardium in the infarction area did no work for the first several days after surgery, it recovered to do some external work with the aid of LVAD pumping. However, recovery of left ventricular function owed more to compensatory increases in pumping ability of the remaining normal myocardium than to recovery of the damaged myocardium. The LVAD could salvage severely damaged hearts unless the infarction area exceeded 50% of the left ventricular wall.
Laboratory of Biomedical Control, Hokkaido University, Sapporo, Japan.
T
T
Nakamura
K
K
Hayashi
J
J
Seki
S
S
Fukuda
H
H
Noda
T
T
Nakatani
H
H
Takano
T
T
Akutsu
D000818:Animals; D005260:Female; D006041:Goats; D006352:Heart Ventricles / Q000473:pathology; D006353:Heart-Assist Devices; D006439:Hemodynamics; D008297:Male; D017202:Myocardial Ischemia / Q000473:pathology / Q000503:physiopathology / Q000628:therapy; D016277:Ventricular Function, Left