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At least 19 recordsLinked to original sources

PubMed1989

Functional right-heart replacement with skeletal muscle ventricles.

Skeletal muscle ventricles were constructed from the latissimus dorsi in seven dogs. All skeletal muscle ventricles underwent a vascular delay period followed by 4-7 weeks of electrical preconditioning. In group 1 (n = 5), the skeletal muscle ventricle was used to replace native right-heart function. Venous return from the superior and inferior venae cavae was directed to the skeletal muscle ventricle with outflow directed to the pulmonary artery. In group 2 (n = 2), the skeletal muscle ventricle was used for partial bypass of the right heart. In both groups, right-heart bypass was continued for as long as 8 hours. In group 1 after 4 hours of continuous complete right-heart bypass, stroke work was 163 +/- 63% of canine right ventricular stroke work. Skeletal muscle ventricle output was 1.14 +/- 0.02 l/min, central venous pressure was 13 +/- 1.5 mm Hg, and systemic systolic blood pressure was 95 +/- 9 mm Hg. Skeletal muscle ventricles are capable of performing the work of the right heart with near-physiological filling pressures.

Animals↗

PubMed1997

Stroke volume validation and energy evaluation for the dynamic training of skeletal muscle ventricles.

Skeletal muscle ventricles used for cardiac assistance were trained dynamically by shifting volume within an elastic training device. To optimize this dynamic training that is by variation of stimulation patterns and application of drugs, methods for stroke volume and energy evaluation were required. A volume shift induced by a muscle contraction resulted in a pressure rise in the training device. Stroke volume was calculated by relating the pressure difference of a muscle contraction to the device's compliance. For validation of the calculated stroke volume, a mock system was built to simulate muscle contractions under various conditions. The stroke volume measured independently and calculated by means of the pressure rise inside the training device, showed an approximately one-to-one relation (R=0.996). Calculation of delivered energy from skeletal muscle ventricles thereby became possible. This method offers a simple, reliable and practical procedure to quantify the dynamic training of skeletal muscle ventricles for use in cardiac assistance.

Biomechanical Phenomena↗

PubMed2003

Haemodynamic considerations in the design of a skeletal muscle ventricle.

Skeletal muscle ventricles (SMVs) configured to operate as diastolic counterpulsators show promise as cardiac assist devices. In four pigs, SMVs were connected to the aorta by a single-limbed conduit and activated during every third cardiac diastole. During the assisted beats, mean diastolic aortic pressure increased by 30.3 +/- 2.2%, peak diastolic aortic pressure increased by 38.5 +/- 2.7%, the endocardial viability ratio increased by 42.3 +/- 3.4%, and mean left anterior descending coronary artery flow increased by 61.6 +/- 4.5%. Although there are major advantages to making the connection to the aorta by a single-limb conduit, the lack of separation between inlet and outlet means that such devices must be designed carefully to avoid thrombogenesis under chronic conditions. Design rules were developed for this configuration, based on earlier in vitro studies. They addressed the problem of stasis by promoting the development of a propagating vortex that travels the length of the ventricle and ensured proper exchange of blood with the circulation by limiting the volume of the connecting conduit. An SMV compatible with these rules was connected in a pig. At elective termination 1 week later, activation of the SMV increased peak diastolic pressure by 20.1% and reduced left-ventricular stroke work in the post-assisted beat by 10.1%. The SMV was free from thrombus.

Animals↗

PubMed1993

Functional evaluation of intrathoracic versus extrathoracic skeletal muscle ventricles.

Skeletal muscle ventricles (SMVs) were constructed from the latissimus dorsi muscle in 10 dogs. In Group I (n = 5), SMVs were left in an extrathoracic position on the chest wall. In Group II (n = 5), SMVs were placed within the chest cavity. After a 3- to 4-week vascular delay period, SMVs were electrically preconditioned with 2 Hz continuous stimulation for 6 weeks. At a second procedure, SMVs were connected to a mock circulation system, and function was evaluated under differing conditions of preload and afterload. SMVs in Group II were significantly more compliant, as demonstrated by the end diastolic pressure volume relationship, than those in Group I (P < 0.01). SMVs in Group II were also capable of generating greater stroke work than those in Group I (P < 0.05). SMVs in Group II were also capable of greater stroke work than those in Group I at physiologic preloads (P < 0.05). These findings suggest that SMVs placed in an intrathoracic position exhibit better diastolic and systolic function.

Animals↗

PubMed1995

Endothelial cell-lined skeletal muscle ventricles in circulation.

Skeletal muscle ventricles were constructed from the latissimus dorsi in six dogs by wrapping the muscle around a polypropylene mandrel. Jugular vein endothelial cells were harvested enzymatically and grown in tissue culture. After 3 weeks of vascular delay and 4 weeks of electrical conditioning, five skeletal muscle ventricles were seeded with 5 to 8 x 10(6) autologous endothelial cells by percutaneous injection of a cellular suspension into the lumen of the skeletal muscle ventricle; one skeletal muscle ventricle was injected with culture medium alone as an unseeded control. The autologous endothelial cells were all prelabeled with a lipid-bound cellular marker, PKH-26. After an additional 4 weeks of electrical conditioning, the mandrels were removed and the skeletal muscle ventricles were connected to the descending thoracic aorta and activated to contract during cardiac diastole at a 1:2 ratio with the heart. After 3 hours of continuous pumping, mean diastolic pressure was increased by 35% (58 +/- 7 versus 78 +/- 6 mm Hg, p < 0.05). At this time, the skeletal muscle ventricles were excised for histologic examination. Sections stained with hematoxylin and eosin revealed a continuous cellular layer lining the skeletal muscle ventricle; no cells were present on the lumen of the control skeletal muscle ventricle. All seeded skeletal muscle ventricles exhibited fluorescence as a result of the PKH-26 cellular marker. Immunofluorescent staining with antibodies to von Willebrand factor and ultrastructural analysis with an electron microscope confirmed the endothelial character of these cells lining the lumen of the skeletal muscle ventricles. The ability to create endothelial cell-lined muscular pumping chambers holds important implications for the resolution of thrombotic events in cardiac assist devices as well as toward the clinical application of skeletal muscle ventricles.

Animals↗

PubMedDate not supplied

Progressive pressure expansion in skeletal muscle ventricle conditioning.

Skeletal muscle ventricle (SMV) conditioning typically results in reduced muscle performance. This study investigated the effects of progressive SMV resting pressure expansion and dynamic muscle training on SMV pumping capability. SMVs were formed from latissimus dorsi muscle in five goats. Three experimental SMVs were conditioned against a compliant pneumatic implant system. SMV resting pressure was progressively increased as the SMV adapted to each increment. Resting pressure rose from 40 to 100-120 mmHg over an 8 week period of time. Two control SMVs were conditioned against a non expanded incompressible implant. Both experimental and control SMVs were electrically burst stimulated for at least 6 weeks after an initial 2 week vascular delay interval. Results demonstrate that 1) experimental SMVs increased in volume; 2) SMV passive and active (evoked isovolumetric pressure) pressure-volume curves adapted to the increasing or static resting volume; and 3) two of three experimental SMVs generated greater stroke volumes than control SMVs across a range of counterpulsation pressures and electrical stimulation parameters. Progressive pressure expansion using a compliant implant system improved final SMV pumping performance and merits further investigation.

Adaptation, Physiological↗

PubMed1993

Update on skeletal muscle ventricles as aortic diastolic counterpulsators.

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.

Animals↗

PubMed1994

Chronic morphologic changes of skeletal muscle ventricles in circulation.

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.

Animals↗

PubMedDate not supplied

Skeletal muscle ventricles in continuity with the bloodstream.

BACKGROUND AND AIM OF STUDY: The prevalence of end-stage congestive heart failure and limitation of clinical alternative treatments present the need for creative new solutions. Formation of a ventricle from skeletal muscle (SMV) has shown promise in the animal laboratory. Two modes of the SMV for cardiac assistance, the counterpulsation (CP-SMV) and the ventricular assist (VA-SMV), using the latissimus dorsi muscle were applied in a canine model. Ability to augment arterial pressure was assessed. The effect of stimulation delay on the degree of augmentation was also evaluated. METHODS AND RESULTS: Thirty-five SMVs were connected in continuity with the bloodstream in the two modes: (1) CP-SMV (aorta-to-aorta) (n = 12); and (2) VA-SMV (left ventricular [LV] apex-to-aorta) (n = 23). In the CP-SMV mode, designed to simulate the intra-aortic balloon pump, the SMV was simply interposed into the path of the descending aorta (DAo) without prosthetic valves in either the inflow or the outflow conduit. In order to obligate blood flow through the SMV, the DAo was ligated between the two grafts. In the VA-SMV mode, the connection was made with valved conduits from the LV apex (inflow) to the ascending aorta (outflow) (n = 11) or to the DAo (n = 12). The ascending aorta (AAo) was also ligated proximal to the outflow conduit for the same reason of obligating blood flow through the SMV. The SMV was timed to contract in diastole in both the CP-SMV mode and the VA-SMV mode. In the VA-SMV mode, the average systolic pressure without stimulation was 101.6 +/- 2.2 mmHg and with stimulation 118.21 +/- 4.78 mmHg (mean augmentation, 14.5 +/- 2.6 mmHg) (p < 0.01). In the CP-SMV mode, the average systolic pressure without stimulation was 97 +/- 32 mmHg and with stimulation, 122 +/- 26 mmHg (mean augmentation, 25 +/- 8.6 mmHg) (p < 0.001). We also extended earlier work on timing of stimulation of isolated SMV by evaluating the effect of stimulation delay on the degree of augmentation in continuity with the bloodstream with the SMV in the VA-SMV configuration. Delays of 50 msec to 225 msec were evaluated. SMV stimulation was via the thoracodorsal nerve at an amplitude of 1.5 V and a frequency of 25 Hz. The greatest augmentation occurred at a stimulation delay of 150 msec (p < 0.001). CONCLUSION: Both counterpulsation and assist configurations produced effective diastolic augmentation. Although diastolic augmentation occurred with all timing delays, the optimal delay was 150 msec. Complications in the survival animals include AAo problems, SMV rupture, respiratory insufficiency, intraoperative instability, and thrombosis (which occurred in 51% [18/35] of the animals). This high frequency of thrombosis in the canine model suggests the use of a less thrombogenic SMV lining, more aggressive or prolonged anticoagulation, or an alternative animal model.

Animals↗

PubMedDate not supplied

Simple electrical model of the circulation to explore design parameters for a skeletal muscle ventricle.

To efficiently investigate a variety of designs for an accessory skeletal muscle ventricle for circulatory assistance, we developed an electrical model of the human circulatory system. Heart and blood vessels were modeled as resistive-capacitive networks, pressures as voltages, blood flow as electric current, and the cardiac valves as diodes. Pumping of blood was simulated by the application of damped rectangular voltage pulses to the capacitances of the cardiac ventricles and the skeletal muscle ventricle. Three configurations of a skeletal muscle ventricle were studied: the apico-aortic, in which the skeletal muscle ventricle is interposed between the left ventricle and the abdominal aorta; the aorto-aortic, in which the skeletal muscle ventricle is interposed between the thoracic aorta and the abdominal aorta; and the atrial-aortic, in which the skeletal muscle ventricle is interposed between the left atrium and abdominal aorta. The three skeletal muscle ventricle designs were tested as counterpulsatile assist devices in simulations of the normal circulation and congestive heart failure. Performance of the various skeletal muscle ventricle designs was evaluated by comparing total output, mean left ventricular power expenditure, mean skeletal muscle ventricle power expenditure, and mean perfusion pressure of the skeletal muscle comprising the pouch. Under both normal heart and heart failure conditions, the apico-aortic design was superior to the aorto-aortic and to the atrial-aortic designs. With optimal stimulation parameters, the apico-aortic design reduced left ventricular minute work to 16% of normal during simulated heart failure while maintaining a viable resting cardiac output of 3.4 L/min.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Circulation↗

PubMed1991

Autogenously lined skeletal muscle ventricles in circulation. Up to nine months' experience.

Skeletal muscle ventricles were constructed in fifteen dogs. After a delay period of 4 weeks the skeletal muscle ventricles were connected to the descending thoracic aorta with a polytetrafluoroethylene bifurcation graft (Gore-Tex bifurcation graft, W.L. Gore & Associates, Inc., Elkton, Md.). The aorta was ligated between the two limbs of the graft so that there was obligatory blood flow through the skeletal muscle ventricle. Nine skeletal muscle ventricles were lined with autogenously derived tissue, either pleura or pericardium, whereas six had no specific lining other than an induced fibrous reaction. The skeletal muscle ventricles were activated to contract during cardiac diastole. Aortic diastolic counterpulsation was achieved in all dogs, with ten surviving from 1 week to beyond 9 months. Thrombus eventually developed in all but three of the skeletal muscle ventricles, but no dog had clinical evidence of thromboemboli. The three thrombus-free skeletal muscle ventricles were lined with pleura, including the animal surviving beyond 9 months. These results indicate that canine skeletal muscle can provide aortic diastolic counterpulsation for 9 months without clinically apparent thromboembolic complications.

Animals↗

PubMed1996

Skeletal muscle ventricles: frontiers in 1995.

Skeletal muscle ventricles (SMVs) constructed from electrically conditioned latissimus dorsi muscle (LDM) may become an alternative for assisting the failing heart. Left and right heart circulatory assist using SMVs has been performed successfully in both acute and chronic animal models. The configurations used to connect SMVs to the circulation have included a left atrium to aorta bypass, a left ventricle apex to aorta bypass, aortic counterpulsators, a cavopulmonary bypass, and a right ventricle to pulmonary artery bypass. One SMV used as an aortic counterpulsator functioned effectively in the circulation for more than 27 months. Recent application of the pericardium to the SMV as an inner layer and design changes in the connection of the SMV to the circulation have reduced the risk of thrombus formation and SMV rupture. Although several problems have yet to be solved, the goal of the SMV as a permanent circulatory assist device without the limitation of an external power source seems within reach.

Animals↗

PubMed1990

Skeletal muscle ventricles for total heart replacement.

Skeletal muscle ventricles (SMV) were constructed from canine left latissimus dorsi muscle. The animals were divided into three groups: group A (n = 5), SMVs rested 4 weeks without electrical conditioning; group B (n = 6), SMVs rested 4 weeks and then electrically conditioned for 6 weeks; group C (n = 5), SMVs rested 18 weeks without electrical conditioning. At the end of each protocol, the SMVs were acutely tested by connecting them to a mock-circulation device. The SMVs in group C developed stroke work at physiologic preloads superior to any previously reported, as high as 194% of left ventricular stroke work at afterloads of 80 mmHg. The SMVs in group B developed work outputs equivalent to 53% of the left ventricle, which is still more than four times that of the right ventricle. The results show that it is possible to harvest sufficient work from skeletal muscle ventricles to fully replace cardiac function at physiologic preloads.

Adaptation, Physiological↗

PubMed1993

[Functional evaluation of skeletal muscle ventricles for circulatory assist].

Skeletal muscle has a potential power for cardiac assist. Two approaches have been used to harvest this power: dynamic cardiomyoplasty, which involves the application of muscle directly to the heart to support cardiac contractile function; and the construction of skeletal muscle pouches or ventricles, which are used as separate pumps working either in parallel or in series with the heart. In this study, we evaluated the function of the skeletal muscle ventricles (SMVs) for circulatory assist. In six dogs (18.5 +/- 2.3 kg, mean +/- S.E.M.), SMVs were constructed from the right latissimus dorsi muscle, and placed in the right hemithorax. After a 3-week vascular delay period, the SMVs were preconditioned electrically by 2 Hz continuous stimulation for six weeks. Nine weeks later, SMVs were connected to a mock circulation device for functional evaluation. As right-sided pumps, at a preload of 10 mmHg, SMVs generated stroke work of 0.63 +/- 0.04 x 10(6) ergs with 25 Hz and 0.80 +/- 0.06 x 10(6) ergs with 85 Hz, which exceeded that of the native right ventricle. As left sided pumps, also at a preload of 10 mmHg, SMV stroke work was 0.49 +/- 0.13 x 10(6) with 25 Hz 0.90 +/- 0.09 x 10(6) ergs, which was roughly half that of the left ventricle. These results demonstrate that SMVs have the potential to function as left or right heart assist devices.

Animals↗

PubMed1994

Pericardium-lined skeletal muscle ventricles in circulation up to 589 days.

Skeletal muscle ventricles (SMVs) were constructed from the latissimus dorsi muscle in 15 beagles. The animals were divided into two groups based on modifications in the SMV construction: group I consisted of 5 animals and group II of 10 animals. After a 3-week vascular delay and 6 to 8 weeks of 2-Hz electrical conditioning, the SMVs were connected to the thoracic aorta. In group I, counterpulsation at 33 Hz resulted in an initial 24.4% augmentation of the mean diastolic pressure, a 27.1% decrease in the presystolic pressure, and a 15.9% increase in the endocardial viability ratio. In group II, the mean diastolic pressure rose by 24.7%, the presystolic pressure decreased by 14.3%, and the endocardial viability ratio increased by 24.5%. During propranolol-induced heart failure, the percentage increase in the mean diastolic pressure was improved (12.9% before propranolol infusion versus 27.6% during propranolol infusion), as was the percentage increase in the endocardial viability ratio (11.2% versus 28.7%). Under low cardiac output conditions, SMV contraction resulted in small but statistically significant increases in the total cardiac output (4.3% at 33 Hz, 7.6% at 85 Hz). One animal in group I survived for 589 days with a functioning SMV before progressive dilation of the SMV (impending rupture) developed. Delayed rupture of the SMV sewing ring anastomosis occurred in 2 dogs. Five animals in group II are all alive, with functioning SMVs in the circulation for 377 to 464 days. No animals in group II had rupture of their SMV or showed evidence of thrombus formation.

Animals↗

PubMed1998

Power output of pericardium-lined skeletal muscle ventricles, left ventricular apex to aorta configuration: up to eight months in circulation.

OBJECTIVE: The purpose of this experiment was to evaluate the potential for a skeletal muscle ventricle connected to the circulation between the left ventricle and the aorta to provide effective, long-term cardiac assist. METHODS: Skeletal muscle ventricles were constructed from the latissimus muscle in 10 dogs. After conditioning, the skeletal muscle ventricles were connected to the left ventricle and the aorta with 2 valved conduits. The skeletal muscle ventricle was programmed to contract during diastole. RESULTS: At time of implantation, skeletal muscle ventricles stimulated at 33 Hz and in a 1:2 ratio with the heart significantly decreased left ventricular work by 56% (P <.01) and at 50 Hz by 65% (P <.01). At a 1:2 ratio, the power output of the skeletal muscle ventricles was 59% of left ventricular power output at 33 Hz (P <. 01) and 93% at 50 Hz (P <.01). Animals survived 7, 11, 16, 17, 72, 99, 115, 214, and 249 days. Three deaths were directly related to the skeletal muscle ventricle. One animal is alive at 228 days. In the animal that survived 249 days, skeletal muscle ventricle power output at 8 months with a 33 Hz stimulation frequency and a 1:2 contraction ratio was 57% of left ventricular power output and 82% at 50 Hz. At a 1:1 ratio, skeletal muscle ventricle power output was 97% and 173% of the left ventricle at 33 and 50 Hz, respectively. CONCLUSIONS: Left ventricular assist with a skeletal muscle ventricle connected between the left ventricle and the aorta is the most hemodynamically effective configuration we have tested and can maintain significant power output up to 8 months.

Animals↗

PubMedDate not supplied

Skeletal muscle ventricles seeded with autogenous endothelium.

Skeletal muscle ventricles (SMVs) are muscular pumping chambers constructed from skeletal muscle. Previously, SMVs were connected to the systemic circulation with vascular conduits and used to assist the heart. In this study, SMVs were constructed from the latissimus dorsi muscle in eight dogs. The SMVs were seeded with autologous endothelial cells, but not connected to the circulation. Endothelial cells were harvested enzymatically from autogenous external jugular vein and grown in tissue culture. After 9 weeks, 6 electrically conditioned SMVs were seeded with endothelial cells by injecting 4-5 ml of culture medium containing 5-8 x 10(6) autogenous endothelial cells into each SMV lumen adjacent to the mandrel. Conditioning was stopped at the time of endothelial seeding. One week after seeding, electrical conditioning was resumed. Two weeks after seeding, the animals were killed and the SMVs excised. Histologic examination confirmed the presence of a confluent monolayer of cells covering 80-100% of the luminal surface in each seeded SMV. The endothelial nature of the cells lining the SMV lumen was established by fluorescent microscopy. Endothelial cells were pre labeled with the cellular marker PKH before seeding; the SMVs were also incubated with the endothelial marker dil-acetylated LDL. Endothelial cells also were identified by staining with fluorescently labeled antibodies to von Willebrand factor. Based upon these data, electrically conditioned SMVs can be seeded successfully with a near-complete, autologous endothelial monolayer. Additionally, this endothelial monolayer can be maintained on the luminal surface of a contracting SMV. In-circulation studies will determine whether endothelial cell seeding of SMVs can decrease or eliminate the incidence of thromboembolism.

Animals↗

PubMedDate not supplied

Performance of skeletal muscle ventricles: effects of ventricular chamber size.

Skeletal muscle ventricles were constructed in 12 dogs. In one group of dogs (n = 7) the skeletal muscle ventricles were constructed around a 17 ml Teflon mandrel, and in the other group (n = 5) a 45 ml mandrel was used. Use of the larger mandrel resulted in an increase in compliance and greater stroke work over the physiologic range of preloads and afterloads. With the larger mandrel, stroke work consistently exceeded normal canine stroke work at physiologic filling pressures.

Animals↗