Effect of short pulsed nonablative infrared laser irradiation on vascular cells in vitro and neointimal hyperplasia in a rabbit balloon injury model.

BACKGROUND: Neointimal hyperplasia after PTCA is an important component of restenosis. METHODS AND RESULTS: Cultures of rabbit endothelial cells and smooth muscle cells (SMCs) were irradiated with different doses of nonablative infrared (1064-nm) radiation. Normalized viability index detected with nondestructive Alamar Blue assay and direct cell count were studied. Our experiments demonstrated dose-dependent cytostatic or cytotoxic effects of laser irradiation. We also evaluated the long-term effect of endoluminal nonablative infrared laser irradiation on neointimal hyperplasia in a rabbit balloon injury model. PTCA of both iliac arteries of 23 New Zealand White rabbits was performed. One iliac artery was subjected to intra-arterial subablative infrared irradiation via a diffuse tip fiber. The contralateral vessel served as control. The diet was supplemented with 0.25% cholesterol and 2% peanut oil for 10 days before and 60 days after PTCA. Morphometry after 60 days showed that intimal areas were 0.76+/-0.18 and 1.85+/-0.30 mm(2) in the laser and control arteries, respectively (P=2.2x10(-11)). CONCLUSIONS: We conclude that nonablative infrared laser inhibited neointimal hyperplasia after PTCA in cholesterol-fed rabbits for up to 60 days.

LD Pace II, an easily programmable device for cardiomyoplasty.

The efficacy of programmable devices depends heavily on being able to select parameter values matched to the individual patient's needs. In many cases, physicians fail to make use of all of the features of a device because of programming complexities. This paper presents a new cardiomyostimulator, "LD Pace II", emphasising in particular its novel features and the steps taken to make the behaviour of the device easy for the physician to program.

LD-PACE II: a new cardiomyostimulator for cardiac bioassist.

The LD-PACE II was designed for use in cardiomyoplasty, aortomyoplasty, and skeletal muscle ventricles. All parameters specified as programmable can be changed in a noninvasive manner (using a programming interface wand connected to a computer using the Windows 95/98 environment). Two new functions may be very useful clinically, based on experimental research. 1. Work-rest regimen. The LD-PACE II is able to deliver alternating periods of muscle contractions and rest. Work and rest periods may be programmed independently between 1 and 120 minutes in increments of 1 minute. The work-rest regimen may be useful clinically if muscle contractions are needed for cardiac assist postoperatively. 2. Night/day regimen. This feature allows for a change in the ratio of muscle contractions according to a patient's activity level. During the day the cardiosynchronization ratio may be set from 1:1 to 1:4, and during the night it may be set for 1:8 to 1:16. This allows the muscle to have a long rest period, prevents overuse, and prolongs battery life. These two new features make this cardiomyostimulator very attractive for cardiomyoplasty in particular. The addition of the work-rest and night-day regimens allow the muscle to rest for periods during the day to prevent overuse, subsequent damage, and potential atrophy.

Age related skeletal muscle response to electrical stimulation.

We hypothesized that the conditioned muscles of elderly and growing organisms have different responses to electrical stimulation from that of young adult organisms. Five day old lambs, 1 year old sheep, and 8 year old elderly sheep were used for this investigation. The latissimus dorsi muscle (LDM) was partially mobilized and left in situ. Two electrodes were implanted and electrical stimulation (ES) was begun for 8 weeks; it was then stopped for 2 weeks. Biopsies were taken before ES, after 8 weeks of ES, and after the 2 week delay period. The LDM of old sheep has less fatigue resistance than the LDM of younger animals. Conditioned LDM of the lamb continued to be fatigue resistant after a 2 week delay compared with adult sheep. In all animals, lactate dehydrogenase (LDH) fraction five decreased and LDH-1 + 2 fractions increased after ES. After a 2 week delay, the data returned to baseline values only in adult animals. The percentage area occupied by mitochondria in old sheep was less after ES than in younger animals. In all animals, the mitochondrial area increased after ES and reverted to baseline values after the delay. The number of nuclei and fibers considerably increased after ES. Only in the lamb did the number of nuclei and fibers continue to be elevated after the delay. There are more changes in young skeletal muscle than in adult (1 year or 8 year old) muscle during ES, and they "remember" these properties. Elderly skeletal muscle does not convert to a fatigue resistant state as completely as adult skeletal muscle during a conventional 8 week ES protocol. It is necessary to change and prolong the ES protocol for elderly patients.

Angiogenesis in a patient with ischemic limb induced by intramuscular injection of vascular endothelial growth factor and fibrin platform.

Direct revascularization of critical ischemia of the limb is often unsuccessful due to the anatomic extent and distribution of arterial occlusive disease, and no pharmacologic treatment has proved effective in treating this condition. Patients with ischemic limb may eventually require amputation and may develop serious morbidity and mortality. The goal of limb salvage in these patients has stimulated research into alternative treatment methods, including angiogenesis. Attempts have been made to apply growth factors directly or to encode DNA for such factors, but it is unknown whether these factors remain at the target site long enough to be effective. We report our strategy of using vascular endothelial growth factor in a fibrin network, which enables the sustained release of biologic material at the target site.

Effects of electrical stimulation postcardiomyoplasty in a model of chronic heart failure: hemodynamic results after daily 12-hour cessation versus a nonstop regimen.

The hemodynamic effects of cardiomyoplasty (CMP) have been investigated in many centers, but the question of whether it is necessary to stimulate the latissimus dorsi muscle (LDM) 24 hours a day has not been answered. The main goal of our investigation was to determine whether hemodynamic results after CMP were impaired when continuous electrical stimulation (ES) was off for 12 hours a day. A model of chronic heart failure was created in 12 sheep by performing an arteriovenous anastamosis and administering doxorubicin. Two weeks after the anastomosis, CMP was performed in eight sheep (experimental series); ES training was begun at 2 weeks after CMP. After completion of the initial ES conditioning (8 weeks after CMP), one group of sheep continued to receive ES 24 hours daily. Another group of sheep had only 12 hours of ES daily. Hemodynamic parameters were investigated 2 weeks later with the stimulator turned on and then off. With doxorubicin administration, arteriovenous anastamosis created a stable model of biventricular heart failure (right atrial pressure 20 +/- 3 mmHg vs 6 +/- 2 mmHg at baseline; pulmonary capillary wedge pressure 18 +/- 3 mmHg vs 9 +/- 2 mmHg; left ventricular end-diastolic area 15.2 +/- 1.2 cm2 vs 6.4 +/- 0.7 cm2; left ventricular ejection fraction 0.38 +/- 0.6 vs 0.65 +/- 0.7). Cardiomyoplasty improved hemodynamic status in all eight experimental sheep. However, when the investigation was performed with the stimulator off, this improvement was statistically insignificant. With stimulation on, there was decreased right atrial pressure, pulmonary capillary wedge pressure, left ventricular end-diastolic volume, and increased left ventricular ejection fraction. With the stimulator turned off for 12 hours daily, hemodynamic measurements did not differ from data with continuous ES for 24 hours daily. Because hemodynamic results do not seem to be impaired, we recommend daily, periodic cessation of stimulation to prevent damage to the LDM after CMP.

Angiogenesis in the latissimus dorsi muscle using different regimens of electrical stimulation and pharmaceutical support.

It is our contention that the prevention of ischemia-reperfusion injuries immediately after latissimus dorsi muscle (LDM) mobilization and enhancement of angiogenesis will be effective in improving cardiomyoplasty results. The investigations were performed on adult sheep. Three hours after LDM mobilization, various stages of leukocyte-endothelium interaction were revealed: leukocytes binding to the endothelium, leukocyte destruction of endothelium, and leukocytes leaving capillaries through gaps in the endothelium. Fifty-six days after mobilization various stages of necrosis were discernible. The area occupied by capillaries was 3.45 +/- 0.26% vs. 3.99 +/- 0.24% in control muscle; most of the endothelial cells exhibited morphologic degeneration. Electrical stimulation with 60 CPM actually decreased the capillary density to 2.15 +/- 0.7%, and most of the endothelial cells were damaged, with disrupted plasma membranes. Muscle subjected to 15 CPM increased the percent of capillaries to 5.01 +/- 0.56%, and endothelial cells appeared normal in ultrastructure. Pharmaceutical support prevented muscle damage and accelerated revascularization. After 56 days of autologous biological glue (ABG) application, the area occupied by capillaries was 5.57 +/- 0.24%. This increased to 8.47 +/- 0.72% when aprotinin (proteinase inhibitor) was added to ABG, and to 9.40 +/- 1.24% with pyrrolostatin (free radical scavenger). Both ABG application with aprotinin and electrical stimulation at 15 CPM prevent the LDM from postmobilization damage, and increase angiogenic potential.

Biodesign of a skeletal muscle flap as a model for cardiac assistance.

In using autologous muscles for cardiac assistance, it is crucial to reduce ischemia-reperfusion injury in the surgically traumatized skeletal muscle. In adult sheep, we developed a simple model of surgically designed 2 latissimus dorsi muscle leaflets by modifying the vascular supply to these leaflets. Three pockets with graded injury were established, and muscle morphology and vascular remodeling were monitored in 3 experimental groups: muscle leaflets without any treatment (Group 1, n = 6) that served as controls; muscle leaflets integrated with a fibrin interlayer (Group 2, n = 6); and leaflets integrated with fibrin and entrapped pyrrolostatin (Group 3, n = 6). We applied the fibrinogen and thrombin solutions, which polymerize to form a three-dimensional meshwork joining the tissues, creating a provisional matrix for angiogenesis, and acting as a delivery depot for agents aimed at minimizing ischemia-reperfusion lesion formation. After 2 months, the muscle leaflets biointegrated with the fibrin interface showed none of the signs of necrosis or ischemia-reperfusion lesions seen in the controls. Although no angiogenic factors were incorporated, the fibrin interlayer rapidly (<2 weeks) became a densely vascularized tissue replete with a voluminous capillary network. In contrast, controls showed poor bonding between the tissues, muscle fiber deterioration, and a compromised vascular network. Muscle structure was best preserved and angiogenesis was greatest when pyrrolostatin, a free radical scavenger, was added to the fibrin meshwork to reduce damage caused by overproduction of free radicals. This newly designed model will be useful to study many current approaches in cardiovascular biology, from pharmaceuticals to gene therapy, which might prove advantageous in muscle-designed cardiac assistance.

Multistep approach to electrical stimulation after cardiomyoplasty.

UNLABELLED: Still a controversial procedure, cardiomyoplasty (CMP) improves the failing heart's ability to contract by using a latissimus dorsi muscle (LDM), but to date, hemodynamic results correlate poorly with clinical improvement. The following two causes for apprehension bar attempting to change the conventional electrical stimulation (ES) protocol to improve CMP results: (1) fear of beginning ES for LDM-assisted contraction immediately postmobilization and CMP and (2) fear of stopping or slowing ES during sleep periods. METHODS: In ten different experimental series, I used animal models of CMP to determine how to apply ES to newly mobilized LDM, how to begin partial cardiac assist immediately post-CMP, and how to suspend ES for 12 hours daily. RESULTS: From my experimental series I noted the following three results. (1) Different ES regimens applied 1 hour postmobilization changed the contractile force (CF). After a 30-minute fatigue test, CF decreased by 34% +/- 3% with continuous ES at 30 contractions per minute (cpm), by 23% +/- 2% with continuous ES at 15 cpm, by 25% +/- 5% with ES in a work-rest regimen at 30 cpm, and by 8% +/- 3% with ES in a work-rest regimen at 15 cpm. (2) Imitation of partial cardiac assist immediately postmobilization slightly decreased CF. Sixteen days postmobilization, during a 30-minute fatigue test in animals in which ES had been started immediately after mobilization, CF decreased by only 6% +/- 3% and did not change when ES was combined with imitation of cardiac assist for 30 minutes twice daily (work-rest regimen). (3) ES cessation for 24 hours daily or 12 hours daily in CMP model created no difference in ejection fraction (EF) with ES (54% +/- 4% vs 53% +/- 5%, respectively (or in left ventricular end-diastolic volume (LVEDV, 234.3 ml +/- 1.0 ml vs 24.8 mL +/- 0.6 mL, respectively) or in LV end-systolic volume (LVESV; 12.1 mL +/- 0.7 mL vs 12.8 mL +/- 0.7 mL, respectively). CONCLUSION: For improving angiographic potential in the LDM, ES can be started safely immediately post-CMP at 15 cpm (a 1:4 or 1:5 regimen) and single impulses per burst. For partial cardiac assist and for improving LDM performance, cardiac assist can be used for 30 minutes twice daily immediately post-CMP. To rest the muscle and save it from overuse, muscle contraction can be either stopped or slowed down during hours of sleep.

Unusual recurrence of hydatid cysts of the heart: report of two cases and review of the clinical and surgical aspects of the disease.

In cardiac echinococcosis, a hydatid cyst most frequently forms either solely in the heart or in the pericardium, but there are several reports of cysts forming in the liver or lung or in both. In two cases reported here, both patients developed cysts in new sites after one or more previous surgeries for hydatid cyst removal. In Case 1, the patient first underwent spleenectomy and resection of multiple cysts with no evidence of a cyst in the heart; 3 years later, there was no sign of Echinococcus in the liver, but a large inframyocardial cyst had damaged the left ventricle. In Case 2, the patient first underwent surgery to remove cysts from the pericardium, 2 years later from the anterior wall of the left ventricle, and, finally, 8 months after this second operation, from the left atrium also with no evidence of cyst formation anywhere else in the heart at the time of surgery. These cases emphasize the need for thorough and frequent reevaluation to detect new hydatid cyst formation in the heart and elsewhere caused by the Echinococcus organism.

Cardiomyoplasty after implantation of a pacemaker and cardioverter/defibrillator.

Presently, a combination of two surgical methods improves the survival of patients with advanced ventricular dysfunction: implantable cardioverter/defibrillator implantation (which prevents sudden cardiac death) and cardiomyoplasty (which prevents further dilatation of the heart and provides additional cardiac assistance). We report the clinical course of a patient who had cardiomyoplasty after cardioverter/defibrillator implantation and pacemaker insertion. It is a rare case in which three different devices cardioverter/defibrillator, pacemaker, and cardiomyostimulator) are functioning together without crosstalk.

Comparison of different regimens of electrical stimulation applied to nonmobilized and newly mobilized latissimus dorsi muscle.

We investigated the possibility of preventing further aggravation of muscle ischemia and necrosis in newly mobilized, unconditioned latissimus dorsi muscle (LDM) by utilizing short increments of stimulation with intervening rest periods. Adult St. Croix sheep (N = 12) weighing 30 +/- 8 kg were used in this study. Fatigue tests (30 min) using different stimulation regimens before and after LDM mobilization were performed on all animals; the length of time to return to baseline levels was also measured. Our investigation yielded results that contradict the conventional wisdom that any electrical stimulation damages newly mobilized LDM and will cause a considerable decrease in contractile force (CF). Stimulation regimens using continuous contractions at 30 and 60 contractions per minute (CPM) for 30 minutes were damaging to the LDM. CF also dropped significantly and returned slowly to baseline values: at 60 CPM, CF dropped to 50 +/- 4% and did not return to baseline even after 90 minutes of rest; at 30 CPM, CF dropped to 61 +/- 4% and baseline was restored after 80 minutes of rest. Electrical stimulation using continuous contractions at a slower rate (15 CPM) was tolerable, although a 23% decrease in CF was noted (p < 0.05 when compared to 60 CPM). These results did not satisfy us that such a regimen would be useful for cardiac assistance immediately after cardiomyoplasty. The work-rest regimen at 30 CPM also gave poor results: CF decreased to 75 +/- 2% and baseline was restored after 80 minutes of rest. Promising results were seen when utilizing a work-rest regimen at 15 CPM. The newly mobilized LDM showed no visible signs of fatigue: CF decreased minimally to 92 +/- 3% (p < 0.05 when compared to 30 CPM), and light microscopic analysis of biopsies revealed no morphological damage exceeding that typically seen after subtotal mobilization. Such results open avenues for future investigations: beginning electrical stimulation immediately after cardiomyoplasty (using a single impulse and a slow rate of contraction); decreasing the length of time necessary to obtain full cardiac assistance; and beginning partial cardiac assistance immediately after cardiomyoplasty (if needed) for approximately 30 minutes several times a day.