F W Mocek

Wayne State University, Detroit, MI, United States

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Publications (9)26.43 Total impact

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    ABSTRACT: Skeletal muscle ventricles (SMV) have been shown to pump blood effectively in both acute and chronic models. In this study SMVs were placed in circulation in series with the descending thoracic aorta to function as diastolic counterpulsators. The SMVs were stimulated to contract at a 1:2 ratio with the heart. The R-wave delay and the burst duration were varied, both as a percentage of the total R-R' interval to determine the effect of the SMV on left ventricular (LV) relaxation in relation to other parameters of LV function. Optimal hemodynamic benefit was obtained using a 40% R-wave delay and a 30% burst duration. At these settings, the time constant of LV relaxation (tau) increased from a control value of 29.1 +/- 1.6 to 39.8 +/- 2.1 msec (P < 0.001). The tension time index decreased from a control value of 15.24 +/- .31 to 13.88 +/- .7 mm Hg-sec-1 (P < 0.001). The endocardial viability ratio, an indicator of myocardial blood flow, improved from 1.12 +/- .11 to 1.55 +/- .16 (P < 0.001) and LV dP/dt increased from 1555 +/- 180 to 2320 +/- 210 mm Hg-sec-1 (P < 0.05). In conclusion, this study demonstrates SMV diastolic counterpulsation results in improved LV performance which is associated with a prolongation of LV relaxation. A 40% R-wave delay interval and a 30% burst duration were the stimulation parameters which benefitted myocardial function optimally in this study.
    Journal of Surgical Research 11/1995; 59(5):569-77. · 2.02 Impact Factor
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    ABSTRACT: Skeletal muscle ventricles (SMVs) were constructed either extrathoracically or intrathoracically in 44 dogs using the left latissimus dorsi muscle. These SMVs functioned as aortic counterpulsators for from several hours to 216 days. In this study, the relationship between the morphologic changes in the SMVs and their time course in the circulation was evaluated retrospectively. The average volume of the SMV chamber after it had been excised and fixed in formalin was 21.3 +/- 11.0 mL (mean +/- the standard deviation) for extrathoracic SMVs and 20.0 +/- 7.5 mL for intrathoracic SMVs. The volume of the SMV chamber did not correlate with the time course in the circulation. The SMV wall was mainly composed of three components: muscular, fibrous, and fatty aspects. The overall thickness of the wall appeared to be preserved over time in the circulation. However, the thickness of the muscular component tended to decrease over time. SMV rupture occurred in 15 dogs between postoperative days 4 and 39. All ruptures occurred at the suture line between the SMV and the vascular conduits. There was some degree of thrombus in 24 SMVs. Before SMVs can be applied clinically for the purpose of cardiac assist, problems with rupture and thrombus formation must be solved. A better understanding of the morphologic changes that take place in the SMV over time also is needed.
    The Annals of Thoracic Surgery 05/1994; 57(4):912-20. · 3.45 Impact Factor
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    ABSTRACT: The mechanism of effectiveness of cardiomyoplasty was evaluated in the setting of chronic left ventricular dysfunction in terms of the pressure-volume relationship. The distal branches of the left coronary artery were ligated in 12 sheep. Seven sheep died and the 5 survivors underwent cardiomyoplasty using a left latissimus dorsi graft 10 to 12 weeks later. These muscle grafts were then electrically conditioned for 2 months. The systemic pressure and cardiac output were not different between the postinfarction and postcardiomyoplasty period with the pacemaker off or on. However, the pressure-volume loops were altered by cardiomyoplasty in all 5 animals. Emax, which is an index of ventricular contractility, increased after cardiomyoplasty from 2.66 +/- 0.92 to 4.59 +/- 1.73 mm Hg/mL (mean +/- the standard deviation; p < 0.05), but did not change between the pacemaker off and on situations. The pressure-volume area, which strongly correlates with myocardial oxygen consumption, decreased after cardiomyoplasty (1,932 +/- 615 mm Hg.mL), compared with before cardiomyoplasty (3,776 +/- 1,201 mm Hg.mL) (p < 0.05), but did not change between pacemaker off and on. The probable mechanism responsible for the effectiveness of cardiomyoplasty is an "active" support or constraint of the damaged myocardium by the latissimus dorsi and the prevention of further ventricular dilation. This suggests that left ventricular systolic function can be augmented by cardiomyoplasty, but that it is a secondary mechanism of action.
    The Annals of Thoracic Surgery 02/1994; 57(2):407-15. · 3.45 Impact Factor
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    ABSTRACT: We previously found that double cardiomyoplasty using both acutely raised, unconditioned latissimus dorsi muscles increased cardiac output by 9.6% (1,547 +/- 154 versus 1,695 +/- 166 mL/min), stroke volume by 18.2% (12.1 +/- 0.6 versus 14.3 +/- 0.7 mL), peak left ventricular pressure by 18.4% (98 +/- 3 versus 116 +/- 5 mm Hg), and peak right ventricular pressure by 62.5% (24 +/- 2 versus 39 +/- 4 mm Hg) (p < 0.05 for all differences). In this study 10 dogs underwent double cardiomyoplasty: 3 died perioperatively, and 7 underwent 8 weeks of muscle conditioning. After the conditioning period, the muscle flaps did not contract in 2 of the 7 dogs. Hemodynamics were measured in the remaining 5 dogs. Using fatigue-resistant muscle, cardiac output decreased by 3.7% (1,279 +/- 262 versus 1,233 +/- 274 mL/min), stroke volume decreased by 9.0% (9.5 +/- 1.2 versus 8.8 +/- 1.2 mL), and peak left ventricular pressure increased by 10.6% (82.1 +/- 6.5 versus 90.8 +/- 3.2 mm Hg), but not significantly. Peak right ventricular pressure increased significantly by 31.3% (24.3 +/- 2.1 versus 31.9 +/- 3.6 mm Hg; p < 0.05). Hemodynamic effects of individual left or right muscle contractions versus bilateral muscle stimulation were not significantly different except for a greater percentage increase in peak right ventricular pressure (right, 24.9 +/- 2.1 mm Hg unstimulated versus 28.0 +/- 2.1 stimulated; left, 26.3 +/- 0.9 mm Hg unstimulated versus 30.7 +/- 2.4 mm Hg stimulated; bilateral, 24.3 +/- 2.1 mm Hg unstimulated versus 31.9 +/- 3.4 mm Hg stimulated; p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)
    The Annals of Thoracic Surgery 07/1993; 56(1):31-7. · 3.45 Impact Factor
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    ABSTRACT: Skeletal muscle ventricles (SMVs) were constructed from the latissimus dorsi muscle in seven beagles. Following 3 weeks of vascular delay and 6 weeks of electrical conditioning, the SMVs were connected in series with the thoracic aorta using a valved aortic homograft for the efferent limb. The SMVs were stimulated to contract synchronously during diastole. Effective aortic diastolic counterpulsation was achieved in all dogs, with an average 24.2% +/- 15.3% improvement in diastolic pressure. In two animals surviving beyond 3 months, increase in SMV function was noted over time. Appropriate aortic homograft valve function was documented by echocardiogram. Acute reversible heart failure was induced with propranolol in one dog alive after 126 days. A 61.3% reduction in cardiac output and a 37.6% reduction in mean arterial blood pressure were achieved. During profound low cardiac output, SMV stimulation with 33 Hz and 50 Hz improved cardiac output by 16.9% and 17.8%, improved the tension time index by 14.9% and 16.1%, and improved the endocardial viability ratio by 34.1% and 34.1%, respectively. These results again demonstrate the long-term effectiveness of SMVs as aortic counterpulsators. A valve in the efferent limb of the SMV system functions appropriately over time and may improve the efficiency of the system.
    Journal of Cardiac Surgery 04/1993; 8(2):184-94. · 1.35 Impact Factor
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    ABSTRACT: Skeletal muscle ventricles are constructed from canine latissimus dorsi muscle. These skeletal muscle ventricles can be placed subcutaneously on the chest wall or inside the chest cavity. Skeletal muscle ventricles are connected to the descending thoracic aorta and activated to pump blood as aortic diastolic counterpulsators. The skeletal muscle ventricle in 1 animal pumped blood in the circulation for 27 months. Skeletal muscle ventricles can also function effectively under the condition of low cardiac output. Although thrombus has been detected in some skeletal muscle ventricles, thromboembolism to distal organs has been detected only rarely during the past few years. This research appears promising; however, skeletal muscle ventricle rupture remains a problem and currently accounts for about 30% of the mortality in the long-term experiments. It occurs at the site between the skeletal muscle ventricle outlet and the Dacron sewing ring that is necessary to connect conduits from the skeletal muscle ventricle to the animal's circulation. We believe that skeletal muscle ventricle rupture is likely to be a solvable problem. Once a solution has been found, skeletal muscle ventricles may be ready for clinical use in patients with chronic congestive heart failure.
    Texas Heart Institute journal / from the Texas Heart Institute of St. Luke's Episcopal Hospital, Texas Children's Hospital 02/1993; 20(2):105-11. · 0.67 Impact Factor
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    ABSTRACT: Skeletal muscle ventricles (SMVs) were constructed from the latissimus dorsi muscle in 6 dogs. After 3 weeks of vascular delay followed by 6 weeks of 2-Hz continuous electrical conditioning, a valved conduit was placed between the left ventricular apex and the SMV and a second valved conduit, between the SMV and the aorta. The SMV was stimulated to contract during diastole at a 1:2 ratio with the heart. The SMV pumped 47% of the systemic blood flow initially (0.73 +/- 0.23 versus 1.54 +/- 0.42 L/min) and 40% after 3 hours. Skeletal muscle ventricle stimulation resulted in a 58% increase in mean diastolic pressure initially (52 +/- 9 to 82 +/- 11 mm Hg; p < 0.05) and a 73% increase (45 +/- 7 to 78 +/- 8 mm Hg) after 3 hours of continuous pumping. This was associated with a 68% increase in the endocardial viability ratio initially and a 63% increase at 3 hours. The systolic tension-time index decreased by 26% initially and 25% at 3 hours. This study indicates that the SMV configuration of left ventricular apex to aorta may be particularly suitable for left ventricular assist.
    The Annals of Thoracic Surgery 01/1993; 55(1):78-85. · 3.45 Impact Factor
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    ABSTRACT: Skeletal muscle ventricles (SMVs) were constructed from the left latissimus dorsi in 22 mongrel dogs. The configuration of these SMVs was different from those previously reported. The animals were divided into two groups: group A (n = 11) SMVs rested for 10 weeks after construction; group B (n = 11) SMVs rested for 18 weeks. At the end of the delay period, SMVs were tested in vivo with a mock circulation device. The SMVs in group B developed stroke work greater than those in group A. After acute testing, SMVs (n = 12) were connected to the descending thoracic aorta and stimulated to contract during diastole. Aortic diastolic counterpulsation was achieved in all dogs, with 9 animals surviving from 1 to beyond 28 weeks. In all of the dogs surviving 1 week or more, the SMVs remained free of thrombus. Aspirin was used as the only antithrombotic agent. Skeletal muscle ventricles in this study were able to develop stroke work similar to that previously reported, intermediate between that of the right and left ventricular stroke work, with a significantly decreased incidence of thromboembolism.
    The Annals of Thoracic Surgery 07/1992; 53(6):1025-32. · 3.45 Impact Factor
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    ABSTRACT: It has been shown previously that skeletal muscle ventricles fashioned from canine latissimus dorsi muscle can function as effective blood pumps. We describe four dogs that have been reported on before but have now had skeletal muscle ventricles functioning as effective aortic diastolic counterpulsators for 191 to 836 days. One dog remains well with a skeletal muscle ventricle that has been pumping in circulation for 194 days; there has been no evidence of thrombus in the skeletal muscle ventricle cavity or thromboembolism. None of the three dogs that died had evidence of peripheral embolization, although two of those dogs had thrombus within the cavity of the skeletal muscle ventricle. This study proves that skeletal muscle ventricles can function long-term in the circulation and maintain diastolic pressure augmentation beyond 2 years. To the best of our knowledge, the dog whose skeletal muscle ventricle pumped in circulation for 836 days represents the longest living laboratory animal or human with a functioning heart assist device.
    The Journal of Heart and Lung Transplantation 01/1992; 11(5):S334-40. · 5.11 Impact Factor