Evaluation of stimulation parameters on aortomyoplasty, using Latissimus Dorsi muscle in a goat model: an acute study

Objective: Dynamic aortomyoplasty using Latissimus Dorsi muscle (LDM) has b een shown to improve myocardial function. However, systematic examination o f the effects of stimulation parameters on aortic wrap function has not bee n done. Thus, the present study measures the direct effect of stimulation v oltage, pulse train duration, frequency of the pulses, and the duration of the stimulation delay from R wave on the aortic wrap function. Methods: In eight female goats, the left LDM was wrapped around the descending aorta. T he muscle was then subjected to electrical stimulation, altering frequency of stimulation pulses (16.6, 20, 25, 33 and 50 Hz), amplitude (2, 4, 6, 8 a nd 10 V), and number of pulses (2, 4, 6, 8 and 10 pulses) in a train stimul ation. Left ventricular, aortic pressure, and pressure generated by LDM on aorta (wrap pressure) was measured. The changes in hemodynamic parameters m entioned above were calculated and compared for different stimulation param eters during unassisted and assisted cardiac cycles. Results: Aortomyoplast y counterpulsation using LDM provided significant improvement in wrap press ure (78 mmHg +/- 2), aortic diastolic pressure, and changes in aortic diast olic pressure from 2 to 4 V (P < 0.05). Further increase in amplitude did n ot make any significant improvements of the above mentioned parameters. Sig nificant augmentation of wrap pressure (82 mmHg +/- 2), aortic diastolic pr essure (79 mmHg +/- 3) and changes in aortic diastolic pressure (12 mmHg +/ - 1) occurred at 6 pulses (P ( 0.05). Other changes in number of pulses did not show any significant improvements. Significant improvement of wrap pre ssure (80 mmHg +/- 2), aortic diastolic pressure (73 mmHg +/- 3) and change s in aortic diastolic pressure (12 mmHg +/- 1) was observed with a frequenc y of 33 Hz. To examine a wide range of delays from the onset of the QRS com plex to LDM stimulation, stimulation was delivered randomly. The exact dela y was determined from the ECG signal and superimposed LDM stimulation pulse s. Conclusions: In this study we present a new measurement, wrap pressure. We also present that in aortomyoplasty using LDM, the most significant impr ovement in wrap pressure, aortic diastolic pressure and changes in aortic d iastolic pressure occurs when the stimulation consists of an amplitude of 4 V, a frequency of 33 Hz and a train stimulation of 6 pulses. 8 (C) 1999 El sevier Science B.V. All rights reserved.