Experimental study on potential for cardiac assist by latissimus dorsi myograft--an importance of muscle ischemia

We have studied contractile property and fatigue rates of skeletal muscle ventricle (SMV) constructed using the latissimus dorsi muscles of 11 dogs. The role of early interruption of collateral blood supply in the prevention of muscle ischemia and SMV fatigue was evaluated. Systolic function of SMV was measured in a hydraulic test system; afterload was set at 70 mmHg and preload 15 or 25 mmHg. Control SMV (GI: N = 7), which was fashioned immediately after interruption of collateral blood supply, generated an initial SMV pressure of 222 +/- 50 mmHg and stroke volume of 15 +/- 7 ml/beat with muscle stimulation at a burst-frequency of 50 Hz, but could sustain flow for only 3.5 +/- 0.8 minutes. SMV subjected to a vascular delay (Group II: N = 4) demonstrated improvement of fatigue rates; duration of flow 32.4 +/- 14.0 and sufficient contractile property (initial SMV pressure 182 +/- 17 mmHg, stroke volume 1- +/- 2 ml/beat). Thermography surface temperature mapping revealed remarkable improvement of blood distribution in GII muscles. Flow rates of thoracodorsal artery were significantly greater in GII muscles compared to those in GI muscles (15.0 +/- 3.7 ml/min/LD 100 g, 10.1 +/- 3.1 ml/min/LD 100 g, p less than 0.05, respectively). Despite significant improvement of functional durability in GII muscles, the ratio of oxygen consumption to lactate output was not different between 2 groups. These results suggest that early interruption of collateral blood supply can minimize muscle ischemia, resulting in diminishing fatigue of latissimus dorsi muscles without changes in skeletal muscle metabolism.     

Effects of collateral blood vessel ligation and electrical conditioning on blood flow in dog latissimus dorsi muscle

Utilization of skeletal muscle as a myocardial substitute requires it to undergo two major modifications: mobilization to the site of action and adaptation to continuous activity. We have examined the effects of collateral blood vessel ligation, which would accompany mobilization, on blood flow in control and electrically conditioned canine latissimus dorsi (LD) muscle. Blood flows were measured at rest and during a vigorous isometric fatigue test. In 22 control muscles, electrical stimulation during the fatigue test resulted in a sevenfold increase in muscle blood flow (0.26 +/- 0.18 ml/g/min at rest, 1.69 +/- 0.84 ml/g/min during stimulation). No difference was detected in flow to distal and proximal portions of the muscle. In three muscles where collateral vessels were ligated immediately before measurement of blood flow, flow in the proximal portion of the muscle was not significantly different from control, but in the distal portion, stimulation failed to elicit an increase in flow (0.12 +/- 0.13 ml/g/min at rest, 0.16 +/- 0.07 ml/g/min during stimulation). In animals allowed a 3-week recovery period following collateral vessel ligation, stimulation-induced increases in blood flow were detected but remained lower than control. Muscles which had been conditioned by continuous electrical stimulation for 6-7 weeks at 2 or 10 Hz generated less peak isometric tension than controls (peak tension = 4.5 +/- 1.7 kg control, 2.4 +/- 0.7 kg following 2 Hz conditioning, 1.6 +/- 0.4 kg following 10 Hz conditioning). However, these muscles demonstrated an increased resistance to fatigue.(ABSTRACT TRUNCATED AT 250 WORDS)     

Skeletal Muscle Ventricles: Another Alternative for Heart Failure

A bstract Background : Autologous muscle has the potential of generating power for cardiac assistance. Problems with muscle fatigue have been overcome by the development of successful protocols of electrical conditioning and by allowing a recovery interval after the initial harvest. Methods : Our laboratory has pursued research with latissimus dorsi muscle pouches, which we term skeletal muscle ventricles (SMVs). By allowing several weeks for a "vascular delay" interval and then electrically conditioning the muscle, these pouches can be connected to the circulation and stimulated to assist the heart. Results : These pouches have been developed and tested in the canine model in numerous configurations, achieving survival beyond 3 years. Conclusions : Although still experimental, SMVs may have the potential of becoming a viable alternative for the future treatment of patients with end-stage heart failure and with infants with certain congenital anomalies.     

Potential for left ventricular assistance by latissimus dorsi myograft--sequential effects of electrical preconditioning on skeletal muscle fiber type, blood flow and metabolic status

In order to evaluate the possibility of left ventricular assistance by latissimus dorsi (LD) myograft, we have studied contractile property and fatigue rates of skeletal muscle ventricle (SMV) constructed using canine LD muscles. Twenty three dogs were divided into 3 groups depending on the conditioning protocol of LD muscles; Group I (Control n = 12), Group II (Vascular delay n = 4) and Group III (Vascular delay and electrical preconditioning n = 7). SMVs in GIII dogs generated sufficient pressure and forward flow in a hydraulic test system with muscle stimulation at a burst-frequency of 50 Hz (SMV pressure 131 +/- 42 mmHg, Stroke volume 7.0 +/- 3.0 ml/beat). Although SMVs in GI and GII dogs could sustain flow for only 4.0 +/- 1.1 minutes and 32.4 +/- 14.0 minutes, respectively, SMVs in GIII were able to pump continuously for 107.5 +/- 15.0 minutes (p less than 0.01, vs GI and GII). Thermography surface temperature mapping revealed marked improvement of blood distribution of LD muscles in GII and GIII dogs. Flow rates of thoracodorsal artery during SMV stimulation were GI: 10.0 +/- 3.1 ml/minute/LD 100 g, GII: 15.0 +/- 3.7 ml/minutes/100 g and GIII: 20.7 +/- 2.5 ml/minutes/100 g (p less than 0.01 vs GI). The ratio of oxygen consumption to lactate output was GI: 0.33 +/- 0.10, GII: 0.36 +/- 0.09 and GIII: 1.56 +/- 0.97 (p less than 0.01 vs GI, p less than 0.05 vs GII). Histochemical examination of LD muscles using alkaline ATPase stain revealed muscle fiber type transformation of GIII muscles. These results suggest electrically preconditioned LD muscles have sufficient contractile property for partial left ventricular assistance, and highly fatigue-resistant properties resulted from muscle fiber transformation, improved muscle perfusion and metabolic changes.     

Long-term stimulation of a diaphragm muscle pouch

Denervated hydraulic pouches were fashioned from a retrosternal portion of the right hemidiaphragm and electrically stimulated for several hours at voltages selected to achieve pressures commensurate with those encountered in the right ventricle. The data revealed a progressive decline in pressures generated by the pouch with time, the deterioration perhaps enhanced by inpaired perfusion of the pouch but statistically independent of systemic blood pressures. Therefore it was concluded that contraction of the diaphragm muscle could not be used clinically to assist the heart.     

Liver circulation and oxygen metabolism during short time ligation and the hepatic artery in the dog

The changes of liver circulation and liver oxygen metabolism during and after one hour hepatic artery ligation (HAL) were studied in eight mongrel dogs. At the end of the HAL period total hepatic blood flow (THBF) was reduced from 115.6 +/- 5.5 ml/min . 100 g liver tissue to 68.0 +/- 3.7 ml/min . 100 g or 59% of the initial value. The portal venous blood flow was reduced from 83.1 +/- 3.4 to 58.8 +/- 3.7 ml/min . 100 or 82% of the initial value and the liver oxygen consumption was reduced from 4.1 +/- 0.2 ml/min . 100 g to 3.1 +/- 0.3 ml/min . 100 g or 76% of the initial value. The changes in portal venous blood flow and liver oxygen consumption were reversible following reopening of the hepatic artery. The clinical importance of a reduced portal venous blood flow and liver oxygen consumption following HAL and the possibilities to increase the portal venous blood flow are discussed.     

Oxygen consumption of chronically stimulated skeletal muscle

The latissimus dorsi muscles of six dogs were made fatigue resistant by chronic electrical conditioning. Once the muscles were conditioned, oxygen consumption was measured during periods of exercise. The ratio of the tension developed to oxygen consumed during moderate stimulation (300 msec on) for the control and the electrically conditioned muscles was 16.3 +/- 3.5 and 36.5 +/- 6.7 kg-sec/ml oxygen, respectively. During intense stimulation (800 msec on) the ratio was 12.6 +/- 2.1 and 54.2 +/- 8.9 kg-sec/ml oxygen, respectively. Thus the conditioned muscle was able to develop and maintain tension with a considerably reduced oxygen expenditure. The increased efficiency of the conditioned muscle helps to explain its increased resistance to fatigue and the ability of pumping chambers constructed from electrically preconditioned skeletal muscle to perform sustained cardiac type work.     

Voltage-dependent performance of skeletal muscle pouches: implications for cardiomyoplasty.

Cardiomyoplasty, a new therapy for heart failure, uses autologous skeletal muscle to mechanically assist the heart. The success of dynamic cardiomyoplasty is critically dependent on the contraction strength of the assisting skeletal muscle. Unlike cardiac muscle, skeletal muscle contracts in a graded response to electrical stimulation. However, in current cardiomyoplasty practice, no systematic technique exists to set the stimulating voltage effecting skeletal muscle contraction. The stimulating voltage is simply set to some multiple of the "threshold" voltage. Furthermore, researchers do not consider the role of stimulating voltage when they determine the amount of assistance afforded during cardiomyoplasty. To more accurately assess the value of this heuristic voltage-setting technique, we investigated the role of stimulating voltage on the strength of contraction of the latissimus dorsi muscle. Six New Zealand white rabbits had isovolumic hydraulic pouches constructed from the latissimus dorsi muscle. The muscles were wrapped around a compliant balloon in which isovolumic pressure development was measured during tetany-inducing burst (pulse-train) stimulation. The tetanic plateau of the pouch pressure record was used to measure the effects of stimulating voltage on skeletal muscle contraction. Results indicated that (1) increasing stimulating voltage from two to four times the "threshold" voltage increased normalized pouch pressure from 0.38 +/- 0.21 to 0.78 +/- 0.12 (mean +/- SD) (p < 0.05); (2) the threshold-normalized voltage necessary to cause maximal muscle contraction varied widely (5.7 +/- 2.0, mean +/- SD; range, 3.1 to 9.3); and (3) the current achieving maximal pressure development varied from 5.6 to 31.4 mA (19.9 +/- 10.4 mA).(ABSTRACT TRUNCATED AT 250 WORDS)     

Skeletal muscle ventricle used for right ventricle assistance

There are a number of advantages in using an electrically stimulated autogenous skeletal muscle to construct an auxiliary ventricle to assist a heart. The purpose of this study was to determine the feasibility of biological right ventricular assistance using long-term electrically stimulated skeletal muscle grafts. In fourteen dogs, the latissimus dorsi muscles and the right thoracodorsal nerves were exposed and unipolar pulse generator was implanted. The initial rate of 70 cycle/min. was increased to a rate of 100 cycle/min. Six or 12 months later, the latissimus dorsi was wrapped around a latex pouch equipped with inflow and outflow valved conduit (skeletal muscle ventricles; SMVs). The SMVs were connected to main pulmonary artery and right atrium. These SMVs were stimulated 20 Hz for 200 msec at a fixed rate of 90 cycle/min, the hemodynamic changes with or without skeletal muscle ventricular assistance (SMVA) were measured. In as animals the circulation failed after total right ventricular bypass without SMVA. But the SMVA increased aortic blood pressure, aortic blood flow, left atrial pressure and peak pulmonary pressure significantly. There was a linear correlation between central venous pressure and skeletal muscle ventricular assist flow. Histologic studies showed the conditioned muscles had a greater percentage of slow-twitch, fatigue resistant fibers on ATPase stain. These results suggested the long-term electrical conditioning skeletal muscle could be possible to use SMVs in humans to provide support in children with some types of congenital heart disease.     

Durability of confluent endothelial cell monolayers on small-caliber vascular prostheses in vitro

Since implantation of small-caliber vascular grafts with preformed confluent endothelial cell monolayers (ECMs) may prevent acute platelet deposition and thrombus formation, we have evaluated the conditions necessary to produce durable ECMs. Cultured human umbilical-vein ECs in buffer were attached to vascular grafts--either expanded polytetrafluoroethylene (ePTFE) or knitted Dacron, both with inside diameters of 4 mm--precoated with collaten type I and perfused in vitro with serum-containing culture medium to achieve cell spreading into confluent monolayers. The number of cells attached was quantified by DNA measurements and indium-111 labeling. Morphology was evaluated by scanning electron microscopy. The maximum number of cells that attached acutely was 3.6 X 10(5) cells/cm2 graft, and the minimum number needed for confluence was 1.4 X 10(5) cells/cm2 graft. Confluence was morphologically complete after 2 hours of in vitro perfusion at 15 ml/min. When ECMs were exposed to varying flow rates, cell retention after 1 hour was 96.1% +/- 5.6% at 50 ml/min, 94.6% +/- 6.1% at 100 ml/min, 77.6% +/- 10.8% at 200 ml/min (p less than 0.001), and 40.1% +/- 10.4% at 400 ml/min (p less than 0.0001). Confluence was maintained for all grafts exposed to flows of 100 ml/min or less. Fewer cells were retained when acutely attached, unspread cells (71.5% +/- 11.5%) were compared with established ECMs (89.9% +/- 6.7%) at a flow rate of 100 ml/min (p less than 0.0001). ECMs on knitted Dacron were more durable than on ePTFE (82.7% +/- 5.3% versus 75.5% +/- 4.8% remained attached at 200 ml/min, P less than 0.05). 111Indium-labeled and unlabeled cells were equivalent with respect to saturation level attachment, spreading time to confluence, and durability under flow at 100 ml/min. We conclude that confluent and durable endothelial cell monolayers can be established on small-caliber vascular grafts within 2 hours.     

Urethral controlled bladder substitution: a comparison between Parks S pouch and hemi-Kock pouch

To study the effect of the configuration of ileal reservoirs on the urodynamic features, 12 S bladders and 12 Kock pouches were compared. Volume capacity and pressure characteristics were studied 6 months postoperatively. The mean capacity of the reservoirs was 500 +/- 83 ml. for the S bladder and 536 +/- 56 ml. for the Kock pouch. The amplitudes of phasic contractions at 50%, 80% and 100% capacity were similar in both groups. However, the frequency of these contractions was higher in the S bladder. The intraluminal pressure at full capacity was 31 +/- 15 cm. water for the S bladder and 39 +/- 20 cm. water for the Kock pouch. The similar urodynamic features of the S and Kock pouches indicate their ultimate expansion into reservoirs of close physical characteristics and urodynamic behavior.     

Perfusion parameters and pressure at zero flow in canine gracilis muscle flaps.

The perfusion parameters and pressure at zero flow were examined in island gracilis muscle flaps in dogs under sodium pentobarbital anesthesia. Complete surgical isolation of the muscle preparation was obtained. Normal blood flow in denervated muscle in situ was 8.0 +/- 0.8 ml/min/100 g tissue as measured by electromagnetic blood flowmetry. The artery supplying each flap was occluded with a microclip and the drop in pressure distal to the clip was observed. The lowest pressure obtained following occlusion was the pressure at zero flow. A positive pressure at zero flow in the vascular bed was thereby identified at a pressure of 10.3 +/- 1.2 mm Hg.     

Epidural blood flow and regression of sensory analgesia during continuous postoperative epidural infusion of bupivacaine

Epidural blood flow was measured in seven patients undergoing elective abdominal surgery during combined lumbar epidural and general anesthesia. After an initial dose of 20 ml plain bupivacaine 0.5%, a continuous epidural infusion of bupivacaine 0.5% (8 ml/hr) was given for 16 hours for postoperative pain relief. The epidural blood flow was measured by a local 133Xe clearance technique in which 15-35 MBq 133Xe diluted in 1 ml saline was injected through the epidural catheter on the day before surgery (no bupivacaine), 30 minutes after the initial dose of bupivacaine on the morning before surgery, and 8, 12, and 16 hours later during the continuous infusion. Initial blood flow was 6.0 +/- 0.7 ml/min per 100 g tissue (mean +/- SEM). After epidural bupivacaine, blood flow increased in all seven patients to 7.4 +/- 0.7 ml (P less than 0.02). Initial level of sensory analgesia was T4.5 +/- 0.17 (mean +/- SEM). Postoperatively, two patients maintained the initial level of sensory analgesia and low pain score throughout the 16-hour study. In these two patients epidural blood flow remained constant after the initial increase. Flow increased further to 10.3 +/- 0.8 ml/min per 100 g tissue (P less than 0.03) in the other five patients as the level of sensory analgesia regressed postoperatively. These data suggest that changes in epidural blood flow during continuous epidural infusion of bupivacaine, and thus changes in rates of vascular absorption of bupivacaine from the epidural space, may be an important factor contributing to differences in rates of regression of sensory analgesia.     

Effect of proximal gastric vagotomy on feeding stimulated Heidenhain pouch acid secretion and gastrin release.

Truncal vagotomy (TV) is known to increase the feeding stimulated acid output of Heidenhain pouches. A series of experiments were performed in dogs to see if proximal gastric vagotomy (PGV) also had this effect. Dogs were prepared with gastric fistulas (GF) and Heidenhain pouches (HP). Gastric function testing included three categories of tests: (1) serum gastrin determinations and Heidenhain pouch acid secretion after feeding, (2) gastric emptying and simultaneous Heidenhain pouch acid secretion, and (3) gastric and Heidenhain pouch acid secretion and serum gastrin levels after insulin. Compelte testing consisting of two control and two post-PGV tests was accomplished in five dogs in each category. Insulin testing confirmed that an adequate PGV was performed because GF peak acid output in response to 0.5 U/kg insulin IV was reduced 88% by PGV (p less than .01). In response to two separate meals peak acid output (PAO) from the HP's was not increased significantly after PGV: Meal I pre-PGV 450 +/- 112 vs post-PGV 400 +/- 99 muEq/15 min; Meal II pre-PGV 256 +/- 62 vs post-PGV 304 +/- 150 muEq/15 min. This finding may represent an important physiologic difference between PGV and truncal vagotomy.     

Evaluation of blood flow in free microvascular flaps

Free flap surgery is routine today, yet little is known of its pathophysiology. In this study, the authors evaluated the hemodynamics in different types of free microvascular flaps, by measuring intraoperative transit-time flow. Eighty-six free transplants--21 free TRAM flaps for breast reconstruction, 18 radial forearm flaps for head and neck reconstructions, and 47 muscle flaps for head and neck, trunk and lower extremity reconstructions--were studied. Donor artery flow was highest in the radial artery (mean: 57.5 +/- 50 (SD) ml/min) but dropped (p < 0.001) to one tenth (6.1 +/- 2 ml/min) after anastomosis. The flow was lowest (4.9 +/- 3 ml/min) in the recipient artery of the TRAM flap but, after anastomosis, increased significantly (13.7 +/- 5 ml/min) to the level of the flow in the donor artery. The donor-artery flow in muscle flaps had a mean of 15.9 +/- 11 ml/min, and it significantly increased after anastomosing (23.9 +/- 12 ml/min). Weight-related intake of blood was highest in the radial forearm flap (18.5 +/- 6 ml/ min/100g) and lowest in the TRAM flap (2.5 +/- 1 ml/min/100g). The study showed that blood flow through a free microvascular flap does not depend on recipient artery flow. Even low-flow arteries can be used as recipients, because the flow increases according to free-flap requirements. The blood flow through a free microvascular flap depends on the specific tissue components of the flap.     

P2 purinoceptor saturation by adenosine triphosphate impairs renal autoregulation in dogs

Recent studies have suggested a role for P2 purinoceptors on vascular smooth muscle cells in the mechanism of renal autoregulation. Experiments were performed in anesthetized dogs (n = 9) to examine renal blood flow (RBF) autoregulatory efficiency before and after saturation of P2 purinoceptors with acute intra-arterial administration of ATP (1 mg/kg per min). Dogs were pretreated with the nitric oxide synthase inhibitor nitro-L-arginine (NLA) (50 microg/kg per min), to avoid endothelial P2 receptor-mediated effects on nitric oxide release caused by the intra-arterial ATP infusions. NLA treatment decreased RBF (5.3+/-0.3 to 3.6+/-0.2 ml/min per g) and sodium excretion (3.6+/-0.4 to 0.9+/-0.2 ml/min per g) without producing significant changes in GFR (0.92+/-0.04 to 0.90+/-0.06 ml/min per g) or RBF autoregulatory efficiency. ATP administration to NLA-treated dogs resulted in further decreases in RBF (2.8+/-0.2 ml/min per g), GFR (0.58+/-0.05 ml/min per g), and sodium excretion (0.6+/-0.2 micromol/min per g). In addition, there was marked impairment of RBF autoregulatory efficiency during ATP infusion. The slopes of the arterial pressure-blood flow relationships at renal arterial pressures of >75 mmHg were significantly altered, from 0.003+/-0.001 to 0.2+/-0.002 ml/min per g per mmHg. Discontinuation of ATP infusion restored RBF autoregulatory efficiency. Norepinephrine (5 microg/kg per min) administration in these NLA-treated dogs decreased RBF (2.5+/-0.3 ml/min per g; n = 4) to a similar extent, compared with ATP, but did not impair RBF autoregulation. These results support the hypothesis that P2 purinoceptors may be involved in mediating autoregulatory adjustments in renal vascular resistance.     

Laser revascularization of ischemic skeletal muscle

BACKGROUND: Clinical trials have shown that transmyocardial laser revascularization is an effective secondary treatment for ischemic heart disease patients. Laser revascularization may also provide an alternative method for treating peripheral vascular disease. METHODS: The purpose of this study was to investigate the potential for laser revascularization in ischemic skeletal muscle. Eighteen rabbits (3-4 kg) were instrumented chronically with transit time ultrasound flowprobes on both common iliac arteries. All rabbits performed graded exercise tests on a treadmill where maximal blood flow was recorded. Unilateral hindlimb ischemia was produced by ligation of one femoral artery. At week 3 postligation, 10 rabbits received laser therapy and 8 underwent a sham surgery. In each of four muscles (gracilius, medialis, sartorius, and biceps femoris) 5 to 22 laser channels were created (average = 52 channels per leg). RESULTS: At week 3 postligation the maximal blood flow of the ischemic limb for the treated group was 64 +/- 3 ml/min (mean +/- SEM) and at 6 weeks postlaser therapy maximal blood flow increased to 75 +/- 5 ml/min. The sham surgery group had a maximal blood flow of 58 +/- 4 ml/min at week 3 postligation and 66 +/- 3 ml/min at week 6 postsham surgery. CONCLUSION: These results indicate that laser therapy does not induce angiogenesis and vascular remodeling in the ischemic hindlimb of a rabbit which exceeds that seen with a sham surgery.     

可控膀胱增强缩窄回肠控制机能的临床研究

目的设计一种控尿可靠,导尿容易和手术方法简单的可控膀胱输出道. 方法对20例尿流改道的患者,采用缩窄的回肠作为输出道,并将部分输出道固定在回肠储尿囊与腹壁之间,输出道的内口与回肠储尿囊作端侧吻合,其外口与脐孔作端端防狭窄吻合的手术方法治疗.术后1.5～3个月和6～ 17个月分别对输出道和储尿囊行尿动力学检查. 结果 1例术后55 d死于心脏疾病,其余19例中,18例术后昼夜能控制尿.术后1.5～3个月尿动力学显示储尿囊充盈时输出道最大闭合压为46～124(92±17)cmH2O(1 cmH2O=0.0 98 kPa),空虚时34～84(67±12)cmH2O,两者间差异有非常显著性意义(t=10.5 9, P＜0.01);6～17个月12例行尿动力学检查,储尿囊充盈时输出道最大闭合压为7 7～154(101±21)cm H2O,空虚时为56～115(74±15) cm H2O,两者差异有非常显著性意义(t=8.54, P＜0.01);储尿囊容量为360～750 (455±111)ml,充盈时内压为16～35(23±6)cmH2O,充盈过程中没有收缩波出现. 结论储尿囊与腹壁的壁外支持可明显增强缩窄回肠的控尿能力,这种术式还具有导尿容易和手术方法简单的特点.     

Electrically stimulated resistance training in SCI individuals increases muscle fatigue resistance but not femoral artery size or blood flow

STUDY DESIGN: Longitudinal. OBJECTIVES: The purpose of this study was to evaluate the effect of lower extremity resistance training on quadriceps fatigability, femoral artery diameter, and femoral artery blood flow. SETTING: Academic Institution. METHODS: Five male chronic spinal cord injury (SCI) individuals (American Spinal Injury Association (ASIA): A complete; C5-T10; 36+/-5 years old) completed 18 weeks of home-based neuromuscular electrical stimulation (NMES) resistance training. Subjects trained the quadriceps muscle group twice a week with four sets of 10 dynamic knee extensions against resistance while in a seated position. All measurements were made before training and after 8, 12, and 18 weeks of training. Ultrasound was used to measure femoral artery diameter and blood flow. Blood flow was measured before and after 5 and 10 min of distal cuff occlusion, and during a 4-min isometric electrical stimulation fatigue protocol. RESULTS: Training resulted in significant increases in weight lifted and muscle mass, as well as a 60% reduction in muscle fatigue (P = 0.001). However, femoral arterial diameter did not increase. The range was 0.44+/-0.03 to 0.46+/-0.05 cm over the four time points (P = 0.70). Resting, reactive hyperemic, and exercise blood flow did not appear to change with training. CONCLUSION: NMES resistance training improved muscle size and fatigue despite an absence of response in the supplying vasculature. These results suggest that the decreases in arterial caliber and blood flow seen with SCI are not tightly linked to muscle mass and fatigue resistance. In addition, muscle fatigue in SCI patients can be improved without increases in arterial diameter or blood flow capacity.     

Increased coronary artery blood flow with aortomyoplasty in chronic heart failure

BACKGROUND: We hypothesized that diastolic counter-pulsation using aortomyoplasty will increase coronary blood flow. METHODS: In dogs (n = 6, 20 to 25 kg), the left latissimus dorsi muscle was isolated, wrapped around the descending thoracic aorta, and conditioned by chronic electrical stimulation. Heart failure was induced by rapid ventricular pacing. In a terminal study, left ventricular and aortic pressures, and blood flow in the left anterior descending coronary artery and descending aorta were measured. The endocardial-viability ratio was calculated. RESULTS: Aortomyoplasty increased mean diastolic aortic pressure (70 +/- 5 to 75 +/- 5 mm Hg, p < 0.05) and reduced peak left ventricular pressure (86 +/- 4 to 84 +/- 4 mm Hg, p < 0.05), leading to a 16% increase in endocardial-viability ratio (1.29 +/- 0.05 to 1.49 +/- 0.05, p < 0.05). Coronary blood flow was increased by 15% (8.2 +/- 1.5 to 9.4 +/- 1.6 mL/min, p < 0.05). During muscle contraction, 2.7 +/- 0.5 mL was ejected from the wrapped aortic segment. CONCLUSIONS: These data demonstrate that aortomyoplasty provides successful diastolic counterpulsation after muscle conditioning and heart failure.