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The Journal of Thoracic and Cardiovascular Surgery, Vol 102, 757-765, Copyright © 1991 by The American Association for Thoracic Surgery and The Western Thoracic Surgical Association
KF Lee, SA Hanan, GE Tuchy, IM Rebeyka, T Yeh Jr, MR Borges, AS Abd-Elfattah and AS Wechsler
Reduction of left ventricular work load during systole, a critical
component of arterial counterpulsation, has not previously been documented
for skeletal muscle-powered extraaortic counterpulsation. To assess its
capacity for afterload reduction, a skeletal muscle extraaortic
counterpulsator was connected to the thoracic aorta and counterpulsated.
Canine hearts (n = 7) were instrumented with left ventricular Millar
catheters (Millar Instruments, Inc., Houston, Tex.) for pressure
measurements and with piezoelectric ultrasonic crystals for measurement of
the left ventricular minor axis dimension and wall thickness. During
systole, skeletal muscle extraaortic counterpulsation resulted in a
significant change in all three determinants of left ventricular
circumferential wall stress compared with control conditions (no
counterpulsation). Pressure decreased (peak systole, 100 +/- 5 versus 75
+/- 6 mm Hg; p less than 0.05 by paired t test), minor axis dimension
decreased (end systole, 46.4 +/- 1.1 versus 45.8 +/- 1.1 mm; p less than
0.05 by paired t test), and wall thickness increased (end systole, 10.4 +/-
0.7 versus 10.6 +/- 0.7 mm; p less than 0.05 by paired t test). Left
ventricular wall stress/dimension work loops showed a shift downward and to
the left, a shift consistent with afterload reduction. The mean systolic
left ventricular wall stress was significantly reduced, from 67.3 +/- 10.6
to 47.7 +/- 8.1 10(3) dyne/cm2 (p less than 0.05 by paired t test).
Skeletal muscle extraaortic counterpulsation increased the diastolic aortic
pressure from 72 +/- 6 to 105 +/- 8 mm Hg (p less than 0.05 by paired t
test). Our data, which documented the counterpulsator's direct effects on
left ventricular functional mechanics, showed that skeletal muscle
extraaortic counterpulsation is capable of both diastolic augmentation of
arterial pressure and systolic unloading of the left ventricle. Skeletal
muscle extraaortic counterpulsation has potential application for
ventricular unloading in the treatment of chronic end-stage heart failure.
ARTICLES
Skeletal muscle extraaortic counterpulsation. A true arterial counterpulsation
Department of Surgery, Medical College of Virginia, Richmond 23298.
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