Degree Type

Dissertation

Date of Award

1994

Degree Name

Doctor of Philosophy

Department

Chemical and Biological Engineering

First Advisor

Donald F. Young

Second Advisor

Mary Helen Greer

Abstract

The performance of a direct systolic cardiac augmentation device, called a heart cuff, was evaluated during application of the device to canine hearts following a period of global ischemia. The heart cuff was developed to provide temporary, partial assistance to a heart experiencing postischemic myocardial dysfunction (myocardial stunning);Myocardial stunning is a postischemic mechanical dysfunction which results from a sublethal tissue injury occurring at the time of reperfusion. The injury will resolve if the myocardial tissue is given sufficient time to recover. Stunning may significantly contribute to the morbidity and mortality of many cardiac procedures because of the temporary inability of the heart to maintain adequate hemodynamic parameters. Standard therapies for a stunned myocardium currently involve the use of pharmacological agents which may be detrimental to the myocardial tissue or circulatory support devices which may be inadequate or require extensive surgical placement;Six mongrel dogs were anesthetized and cardiac fibrillation was induced with a low-voltage alternating current. The subjects were allowed to fibrillate for a period of 3 to 5 minutes. Following defibrillation, the heart cuff was placed around the heart and assistance was synchronized with systole by using the ECG signal for timing. Hemodynamic and cardiac parameters were then measured every 5 minutes for a period of one hour during assistance with every heart beat (EB), assistance with every other heart beat (EOB), and no assistance (NA). The following averages are for all dogs and include each measurement during the one hour of postischemic cardiac support with the heart cuff. Peak left ventricular pressure (LVP) averaged 56 ± 7 and 27 ± 8 mm Hg for EB and NA, respectively. Mean cardiac output averaged 0.44 ± 0.10 and 0.11 ± 0.08 L/min for EB and NA, respectively. Maintenance of cardiac function was dependent on the partial assistance provided by the heart cuff for each dog during the entire support period. Three dogs showed gradual improvement in function with non-assisted peak LVP improving from 12 ± 0.40 to 27 ± 0.40 mm Hg (Dog 1), 14 ± 1.09 to 43 ± 0.97 mm Hg (Dog 2), and 13 ± 0.90 to 41 ± 0.79 mm Hg (Dog 3);The heart cuff was found to provide significant enhancement to the cardiac function of hearts which had undergone global ischemia and to allow some functional recovery to occur. The use of such a device with appropriate enhancements may be a feasible alternative to current therapies for postischemic myocardial dysfunction.

DOI

https://doi.org/10.31274/rtd-180813-11628

Publisher

Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/

Copyright Owner

Raymond Kenneth Kudej

Language

en

Proquest ID

AAI9424236

File Format

application/pdf

File Size

122 pages

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