Dynamic cardiomyoplasty: clinical follow-up at 12 years

Elastomeric Cardiowrap Scaffolds Functionalized with Mesenchymal Stem Cells-Derived Exosomes Induce a Positive Modulation in the Inflammatory and Wound Healing Response of Mesenchymal Stem Cell and Macrophage

A challenge in contractile restoration of myocardial scars is one of the principal aims in cardiovascular surgery. Recently, a new potent biological tool used within healing processes is represented by exosomes derived from mesenchymal stem cells (MSCs). These cells are the well-known extracellular nanovesicles released from cells to facilitate cell function and communication. In this work, a combination of elastomeric membranes and exosomes was obtained and tested as a bioimplant. Mesenchymal stem cells (MSCs) and macrophages were seeded into the scaffold (polycaprolactone) and filled with exosomes derived from MSCs. Cells were tested for proliferation with an MTT test, and for wound healing properties and macrophage polarization by gene expression. Moreover, morphological analyses of their ability to colonize the scaffolds surfaces have been further evaluated. Results confirm that exosomes were easily entrapped onto the surface of the elastomeric scaffolds, increasing the wound healing properties and collagen type I and vitronectin of the MSC, and improving the M2 phenotype of the macrophages, mainly thanks to the increase in miRNA124 and decrease in miRNA 125. We can conclude that the enrichment of elastomeric scaffolds functionalized with exosomes is as an effective strategy to improve myocardial regeneration.

Elastomeric cardiopatch scaffold for myocardial repair and ventricular support

OBJECTIVES

Prevention of postischaemic ventricular dilatation progressing towards pathological remodelling is necessary to decrease ventricular wall deterioration. Myocardial tissue engineering may play a therapeutic role due to its capacity to replace the extracellular matrix, thereby creating niches for cell homing. In this experimental animal study, a biomimetic cardiopatch was created with elastomeric scaffolds and nanotechnologies.

METHODS

In an experimental animal study in 18 sheep, a cardiopatch was created with adipose tissue-derived progenitor cells seeded into an engineered bioimplant consisting of 3-dimensional bioabsorbable polycaprolactone scaffolds filled with a peptide hydrogel (PuraMatrix™). This patch was then transplanted to cover infarcted myocardium. Non-absorbable poly(ethyl) acrylate polymer scaffolds were used as controls.

RESULTS

Fifteen sheep were followed with ultrasound scans at 6 months, including echocardiography scans, tissue Doppler and spectral flow analysis and speckle-tracking imaging, which showed a reduction in longitudinal left ventricular deformation in the cardiopatch-treated group. Magnetic resonance imaging (late gadolinium enhancement) showed reduction of infarct size relative to left ventricular mass in the cardiopatch group versus the controls. Histopathological analysis at 6 months showed that the cardiopatch was fully anchored and integrated to the infarct area with minimal fibrosis interface, thereby promoting angiogenesis and migration of adipose tissue-derived progenitor cells to surrounding tissues.

CONCLUSIONS

This study shows the feasibility and effectiveness of a cardiopatch grafted onto myocardial infarction scars in an experimental animal model. This treatment decreased fibrosis, limited infarct scar expansion and reduced postischaemic ventricular deformity. A capillary network developed between our scaffold and the heart. The elastomeric cardiopatch seems to have a positive impact on ventricular remodelling and performance in patients with heart failure.

A Not-Motorized Implantable Device for Partial Circulatory Support: A Proof of Concept Experiment

A fully implantable circulatory assistance device without external connection and lifetime energy supply can eliminate a significant source of morbidity and mortality for patients. Here, we present and discuss concept and preliminary results of an original project for a not-motorized, fully implantable circulatory assistance device. The not-motorized implantable circulatory assistance device (NICA) has been tested into a cardiac simulator that was conceived according to the FDA and ISO standards. The instrumentation incorporated to the cardiac simulator includes probes for the aortic pressure (AoP) proximally to the device, a temperature control system, and one electromagnetic flowmeter to acquire the flow rate (AoF) proximally to the device. A control software allows to modulate the drive parameters such as velocity, acceleration, number of revolutions, the stroke volume, and the heart rate. Experiments have been performed with three different circuit resistances: 2100 dyn s/cm5, 1400, and 700. The AoF increased in the assisted cycles: 71% at 2100 dyn s/cm5, 67% at 1400 dyn s/cm5, and 25% at 700 dyn s/cm5. NICA performs a partial but significant support of AoF without energy supply. The improvement of AoF increases with the increasing of vascular resistances. The feedback received by this preliminary bench experiment acted as a preliminary proof of concept of this new device.

Review article: the new concept of interventional heart failure therapy--part 1: electrical therapy, treatment of CAD, fluid removal, and ventricular support

Congestive heart failure is a chronic and debilitating disease responsible for high cardiac morbidity and mortality in the world and is associated with more than 290 000 deaths in the United States each year. Recent advances in heart failure therapy target many of the mechanical and structural aspects of heart failure that are not addressed by drug-based therapies; these include abnormalities in electrical conduction, coronary artery or valvular architecture, and in ventricular size and shape. To target these abnormalities, newer therapies have largely been mechanical and device-based in nature and can be collectively described as interventional therapy. Interventional therapy includes the use of interventional medical therapy, electrical-based devices to augment ventricular function, catheterization-based devices for the treatment of underlying coronary artery disease and valvular disease, machines for the removal of excess fluid, mechanical pumps to assist the ventricles, surgical techniques aimed at reshaping the ventricles, the use of tissue therapies such as stem cell transplantation or complete heart transplant, palliative care, and self-care. This article is the first in a 2-part series that will review interventional heart failure therapy and present the most recent data supporting its use.

Reversing Left Ventricular Remodeling in Chronic Heart Failure

Chronic heart failure (CHF) has become an epidemic in the United States, with approximately 550,000 new cases annually. With the evolution of pharmacotherapy targeting neurohormonal pathways, the annual mortality in subjects with New York Heart Association (NYHA) class IV CHF has dramatically improved from 52% in the seminal CONSENSUS trial to less than 20% in more recent trials. Suppression of the renin-angiotensin-aldosterone system remains the first line of neurohormonal blockade followed by the addition of selective beta-adrenoreceptor blockers. For patients with NYHA class I and II symptoms, mortality rates have decreased to approximately 5% or less per year with the use of angiotensin-converting enzyme inhibitors, beta-blockers and aldosterone receptor blockers. However, after achieving optimal doses of the indicated pharmacotherapy, and despite the additional benefits obtained with biventricular pacemakers, there are still many patients who continue to experience signs and symptoms of CHF. Recognizing the beneficial effects of the above treatments on left ventricular (LV) remodeling, strategies have been developed to surgically reshape the left ventricle in patients with LV dilation who have associated poor LV function. This review will discuss the techniques and recent developments regarding surgical reshaping of the dilated, dysfunctional, and remodeled left ventricle.

Adaptive cardiac binding: a new method for treatment of dilated cardiomyopathy

Adaptive cardiac binding, a new surgical procedure for advanced heart failure, allows a gradual increase in compression on the dilated heart, with separate loads on the left and right ventricles. A canine model of biventricular heart failure (anastomosis between the carotid artery and jugular vein and doxorubicin administration) was created. Twenty-four dogs were divided into 4 groups: control, adynamic cardiomyoplasty, plastic cardiac binding, and adaptive cardiac binding. In the adaptive cardiac binding group, fluid was added (35, 15, and 10 mL) to each side of the pouch at weeks 1, 2, and 3. Left ventricular ejection fraction was 59%+/-4% before induction of heart failure and 27%+/-2% 6 weeks later. Immediately after the main operation, left ventricular ejection fractions were 35+/-3% (cardiomyoplasty), 34%+/-4% (plastic cardiac binding), and 35%+/-4% (adaptive cardiac binding). Four weeks later, left ventricular ejection fraction had not changed in the cardiomyoplasty (37%+/-3%) and plastic cardiac binding (32%+/-2%) groups, but significantly increased in the adaptive cardiac binding group (48%+/-5%); it had decreased to 23%+/-4% in controls. Adaptive cardiac binding is a promising new surgical approach for patients with end-stage heart failure.

"Demand" stimulation of latissimus dorsi heart wrap: experience in humans and comparison with adynamic girdling

BACKGROUND

Questionable systolic assistance and latissimus dorsi (LD) muscular degeneration as a result of continuous electrical stimulation constitute important drawbacks to dynamic cardiomyoplasty. To avoid full transformation of the LD and thereby cause better systolic assistance, a new stimulation protocol was developed. Fewer impulses per day are delivered so that the LD wrap has daily periods of rest (demand), based on a heart rate cutoff. We describe our experience of demand dynamic wrapping by discriminating between patients with active systolic assistance and those with a passive girdle effect (adynamic-girdling).

METHODS

Fourteen patients with primary dilated cardiomyopathy (13 men, 1 woman; mean age, 58.2 +/- 5.8 years; 12 sinus rhythm, 2 atrial fibrillation) underwent dynamic cardiomyoplasty between 1993 and 1996 as well as the demand protocol at different intervals. Clinical, echocardiographic, mechanographic, and cardiac invasive assessment records, as well as cardiovascular events (death and arrhythmias), were retrospectively reviewed. The patients were divided into two groups on the basis of the mechanographic measurement of speed of contraction of the heart wrap, as measured by tetanic fusion frequency analysis before starting demand stimulation: demand dynamic wrapping patients with fast LD (high tetanic fusion frequency, 7 patients), and adynamic-girdling patients with slow LD contraction times (low tetanic fusion frequency, 7 patients). It was assumed that in adynamic-girdling patients dynamic assistance was virtually absent, so the wrapping acted only as a passive constraint wall.

RESULTS

The two groups were comparable for sex, age, dilated cardiomyopathy cause, New York Heart Association class, and left ventricular ejection fraction at the start of the demand protocol period. After a mean duration of follow-up of 41.4 +/- 21.1 months (range, 23 to 69 months), the demand dynamic wrapping group showed improved New York Heart Association class (1.14 +/- 0.34 versus 2.07 + 0.18; p = 0.0004), higher values of left ventricular ejection fraction (34.6 +/- 8.0 versus 26.5 +/- 3.1; p = 0.005) and LD wrap tetanic fusion frequency (38.3 +/- 5.88 versus 24.3 +/- 2.93; p = 0.002), and a better survival (85.7% versus 28.6%; p = 0.037) than the adynamic-girdling group.

CONCLUSIONS

Demand dynamic wrapping offers good results in terms of fewer cardiovascular events and greater survival. When compared with the passive constraint effect of LD muscle, demand dynamic wrapping proved to be more effective.

Dynamic cardiomyoplasty as a biomechanic bridge to heart transplantation

We report a heart transplantation that was done 4 years after a dynamic cardiomyoplasty operation. The patient was a 42-year-old man. Radionucleide ventriculography with technetium 99 m revealed an ejection fraction of 18%. In July 1997 he had undergone a dynamic cardiomyoplasty operation. At the first postoperative month the left ventricular ejection fraction was 35%. In September 2000 he presented with heart failure symptoms. In May 2001 he had undergone heart transplantation. Postoperative course was uneventful. The failure of cardiomyoplasty was probably caused by degeneration of the latissimus dorsi muscle. In this case we have learned that muscle viability is lost within 4 years after dynamic cardiomyoplasty and heart transplantation is still an option for those patients.

Dynamic graciloplasty for urinary incontinence: the potential for sequential closed-loop stimulation

Muscle tissue transplantation applied to regain or dynamically assist contractile functions is known as 'dynamic myoplasty'. Success rates of clinical applications are unpredictable, because of lack of endurance, ischemic lesions, abundant scar formation and inadequate performance of tasks due to lack of refined control. Electrical stimulation is used to control dynamic myoplasties and should be improved to reduce some of these drawbacks. Sequential segmental neuromuscular stimulation improves the endurance and closed-loop control offers refinement in rate of contraction of the muscle, while function-controlling stimulator algorithms present the possibility of performing more complex tasks. An acute feasibility study was performed in anaesthetised dogs combining these techniques. Electrically stimulated gracilis-based neo-sphincters were compared to native sphincters with regard to their ability to maintain continence. Measurements were made during fast bladder pressure changes, static high bladder pressure and slow filling of the bladder, mimicking among others posture changes, lifting heavy objects and diuresis. In general, neo-sphincter and native sphincter performance showed no significant difference during these measurements. However, during high bladder pressures reaching 40 cm H(2)O the neo-sphincters maintained positive pressure gradients, whereas most native sphincters relaxed. During slow filling of the bladder the neo-sphincters maintained a controlled positive pressure gradient for a prolonged time without any form of training. Furthermore, the accuracy of these maintained pressure gradients proved to be within the limits set up by the native sphincters. Refinements using more complicated self-learning function-controlling algorithms proved to be effective also and are briefly discussed. In conclusion, a combination of sequential stimulation, closed-loop control and function-controlling algorithms proved feasible in this dynamic graciloplasty-model. Neo-sphincters were created, which would probably provide an acceptable performance, when the stimulation system could be implanted and further tested. Sizing this technique down to implantable proportions seems to be justified and will enable exploration of the possible benefits.

Orthotopic cardiac transplantation 30 months after successful dynamic cardiomyoplasty

Reports of cardiac transplantation after successful cardiomyoplasty are rare. We report the case of a 63-year-old man with intractable heart failure who underwent successful orthotopic cardiac transplantation 30 months after dynamic cardiomyoplasty.

Reevaluation of long-term outcomes of dynamic cardiomyoplasty

BACKGROUND

Palliative procedures have been proposed for treatment of dilated cardiomyopathies. This study analyzes long-term outcomes of 43 patients who underwent dynamic cardiomyoplasty.

METHODS

Patients were in New York Heart Association class III (n = 35) or IV (n = 8) before the procedure. Hospital mortality was 2.2%, and patients were followed for 44 +/- 33 months. Thirty-nine patients completed the skeletal muscle adaptation period, and the muscle flaps were stimulated to contract in concert with every cardiac beat (n = 27) or with every other beat (n = 12).

RESULTS

One-year event-free survival was 81.3% +/- 5.9%; 2-year, 65.1% +/- 7.2%; 5-year, 34.7% +/- 7.2%; and 9-year, 10.8% +/- 5.3%. Causes of late deaths were equally divided between progressive heart failure and arrhythmia-related events. Multivariable Cox proportional hazard regression identified that functional class IV, high pulmonary vascular resistance, and muscle flap stimulation synchronized to every cardiac beat were independent predictors of poor event-free survival. The same factors were associated with the occurrence of progressive heart failure, but none was a predictor of arrhythmia-related deaths. Five-year survival of patients maintained with the muscle flap stimulated at every other cardiac beat was 58.3% +/- 14.2%. Skeletal muscle stimulation protocols also influenced the long-term behavior of left ventricular ejection fraction.

CONCLUSIONS

Long-term results of dynamic cardiomyoplasty are limited by the patient's preoperative condition and by a high incidence of sudden cardiac death. These results may be improved using modified skeletal muscle stimulation protocols and cardioverter-defibrillator implantation, while maintaining dynamic cardiomyoplasty as an option for selected patients.

A review of the concept of circulatory bioassist focused on the "new" demand dynamic cardiomyoplasty: the renewal of dynamic cardiomyoplasty?

After the initial enthusiasm, the dynamic cardiomyoplasty lost its reputation owing to the poor long-term results, caused by the muscular degeneration subsequent to chronic continuous electrical stimulation of the latissimus dorsi. An activity-rest stimulation protocol that avoids full transformation of the skeletal muscle, maintaining muscular properties over time, has been successfully tried. This "demand" stimulation protocol showed in humans good results improving NYHA class, ejection fraction value, and survival. The discussion about the capability of this and a unique kind of cardiocirculatory bioassist is due to be reopened. In fact, heart transplant, percutaneous circulatory-supporting device, multisites stimulation therapy, and total artificial heart have some drawbacks, one of which is the economic cost. In developing countries the more economic demand dynamic cardiomyoplasty may still play a role.

Demand dynamic bio-girdling in heart failure: improved efficacy of dynamic cardiomyoplasty by LD contraction during aortic out-flow

PURPOSE

The value of dynamic cardiomyoplasty has been brought into question by the disappointing results produced by slow contraction-relaxation cycle and possibly degeneration of the latissimus dorsi muscle (LD) secondary to temporary tenotomy and chronic daily electrical stimulation. Objective of our study is to determine whether daily periods of rest introduced by demand stimulation in the continuous contraction protocol produce systolic assistance and improve clinical results.

METHODS

Twelve dynamic cardiomyoplasty patients (mean age 58.2 +/- 5.8 years, M/F=11/1, sinus rhythm/atrial fibrillation=11/1) with dilated myocardiopathy were enrolled in an unrandomized trial of Demand Dynamic Heart Bio-Girdling in a public regional teaching hospital. Periods of LD inactivity, each lasting several hours, were introduced daily on a heart rate-based demand regime. To avoid full transformation of LD, fewer impulses per day were delivered, daily providing the LD with long periods of rest (Demand light stimulation). The contractile properties were measured by transcutaneous non-invasive LD tensiomyogram interrogation (LD tensiomyogram). Bio-Girdle activation was synchronized to heart beat by combining tensiomyogram and echocardiography. Clinical, echocardiographic and hemodynamic records, as well as aortic flow measurements by Doppler aortic flow wire were taken during the follow-up.

MAIN FINDINGS

Mean duration of the demand stimulation follow-up was 40.2+13.8 months. At five years, "Demand stimulation" shows: 1) no operative death; 2) 83% actuarial survival; 3) highly significant 47.4% decrease of the NYHA class (from 3.17 +/- 0.38 to 1.67 +/- 0.77, p=0.0001); 4) 41.6% improvement of LVEF (from 22.6 +/- 4.38 to 32.0 +/- 7.0, p=0.001); 5) 7.5 +/- 3.0% increase in aortic flow velocity peak in assisted vs. unassisted beats, and 6) preservation of LD from slowness (TFF value 33 +/- 7.86 at follow-up versus 15.8 +/- 11.1 Hz just before switching from continuous to demand stimulation, p=0.0001) and muscle degenerative atrophy.

CONCLUSIONS

In dynamic cardiomyoplasty the demand light stimulation maintains LD contraction properties over time, produces effective systolic assistance, and improves clinical results. Demand dynamic bio-girdling is a safe and effective treatment for end-stage heart failure in selected patients.

Cardiocirculatory bio-assist: is it time to reconsider demand dynamic cardiomyoplasty? Review and future perspectives

In the last 15 years, dynamic cardiomyoplasty has remained an experimental procedure even after the enthusiastic short- and mid-term results, mainly because of the disappointing long-term outcome caused by muscular degeneration secondary to chronic continuous electrical stimulation of the latissimus dorsi. In Italy, a group of muscular pathologists, cardiologists, and cardiac surgeons conducted an experiment of an activity-rest stimulation protocol in humans that should avoid complete transformation of the skeletal muscle, maintaining its properties overtime. This "demand" stimulation protocol gave good results, improving New York Heart Association class, ejection fraction value, and survival. Even though dynamic cardiomyoplasty was excluded from the recent international guidelines for the management of heart failure, the discussion on the ability of this unique kind of cardiocirculatory bio-assistance is due to be reopened, thanks to the results of the new stimulation protocol. Heart transplantation, circulatory supporting devices, multisite stimulation therapy, and the total artificial heart are not always and in all countries the best solutions: the great economic cost, the numerous contraindications, the need for immunosuppression and antithrombotic therapy, and the troublesome follow up constitute important drawbacks. For patients in whom transplant surgery cannot be performed, as well as in developing countries, the nonprohibitively expensive demand dynamic cardiomyoplasty may still play a role.

Perioperative hemodynamic and geometric changes of the left ventricle during cardiomyoplasty in goats with dilated left ventricle

OBJECTIVE

Clinical data have suggested the occurrence of temporary short-term deterioration of the heart following cardiomyoplasty. The purpose of this study was to monitor the short-term hemodynamic effects of cardiomyoplasty in a goat model of a dilated left ventricle, using conductance catheters (ie, pressure-volume loops) and cardiac output measurements.

METHODS

Eight female goats underwent acute cardiomyoplasty 8 to 12 weeks after left ventricular (LV) dilatation was induced by a carotid jugular arteriovenous shunt. The cardiomyoplasty procedure was monitored using a Swan-Ganz catheter for cardiac output measurements and a 12-electrode (dual-field) conductance catheter to LV pressure-volume loops.

RESULTS

After wrapping the heart with the latissimus dorsi muscle, there was a significant reduction in both cardiac output and LV end-diastolic volume (LVEDV) at 10 min. Partial recovery was observed 45 min later.

CONCLUSION

A decrease in both cardiac output and LVEDV was observed following myocardial wrapping. This may explain some of the perioperative and postoperative morbidity and mortality observed following cardiomyoplasty.

From dynamic to cellular cardiomyoplasty

Dynamic Cardiomyoplasty. Latissimus dorsi dynamic cardiomyoplasty has been used in our institution for heart failure patients refractory to medical therapy; 113 cases were operated at Broussais and Pompidou Hospitals and 75 patients by our team abroad, in the scope of an international cooperative program. Cardiomyoplasty has been associated with better results due to technical improvements, the most significant mini-invasive techniques, the latest the use of growth factors to enhance muscle vascularization. Risk factors have been identified, resulting in more precise indications, a lower hospital mortality, and a wider use of this operation. There has been a new tendency to associate cardiomyoplasty with electrophysiological therapies: implantation of ventricular defibrillators and multisite cardiac pacing (for atrioventricular and interventricular resynchronization). Cellular Cardiomyoplasty. Adult myocardium cannot repair after infarction due to the absence of stem cells. Cell transplantation strategies for heart failure have been designed to replace damaged cells with cells that can perform cardiac work. Current possibilities in cell therapy for heart failure is the transplantation into the infarcted myocardium of autologous myoblasts (satellite cells originated from skeletal muscle), fetal cardiomyocytes, autologous heart cells, cells derived from bone marrow stem cells, and smooth muscle cells. Experimental studies demonstrated that cell transplantation into the myocardium was associated with the recovery of myocardial contractility and compliance, as well as the diastolic pressure-strain relationship in animal models (infarctlike myocardial lesions and dilated cardiomyopathy models). Healthy myoblasts and myotubes were observed 2 months after myocardial implantation. Clinical studies are now in progress.

Left ventricular splints and wraps for end-stage heart failure: a new approach in the new millennium

The epidemic of heart failure and its subsequent effect on public health policy is escalating. Cardiac transplantation continues to be limited by the shortage of donor organs, and the current generation of mechanical circulatory support devices has not yet approached the goal of destination therapy. A better understanding of the role of left ventricular remodeling in the development of heart failure has resulted in novel surgical therapies and devices that may reverse or retard the remodeling process.

Girdling effect of adynamic cardiomyoplasty in a model of dilated cardiomyopathy

OBJECTIVE

The potential benefits of adynamic cardiomyoplasty remain unclear. We determined whether unstimulated skeletal muscle wrap alone prevents or attenuates progressive left ventricular dilation in a canine model of congestive heart failure produced by repeated intracoronary infusions of doxorubicin.

SUBJECTS AND METHODS

14 dogs were randomized in to 2 groups, 1 undergoing cardiomyoplasty (CMP group) and 1 that did not (CONT group). Intracoronary doxorubicin was administered weekly for 5 weeks to induce heart failure. Hemodynamic data was obtained before infusion and 5 weeks afterward. Echocardiography was done weekly.

RESULTS

Significant left ventricular dilation was observed in the CONT group--left ventricular end-diastolic diameter increased from 28.9 +/- 2.7 to 38.5 +/- 3.3 mm (p < 0.05). Significant left ventricular dilation was also observed in the CMP group--left ventricular end-diastolic diameter increased from 28.9 +/- 3.3 to 38.0 +/- 4.2 mm (p < 0.05). Dilation was slower in the CMP group than in the CONT group, however. Ejection fraction decreased from 58.0 +/- 13.8 to 29.9 +/- 13.7% in the CONT group, but was preserved from 56.0 +/- 8.8 to 51.9 +/- 10.3% in the CMP group.

CONCLUSIONS

Adynamic cardiomyoplasty reduces ventricular dilation associated with heart failure without exacerbating left ventricular dysfunction.

Nonstimulated cardiomyoplasty improves hemodynamics in myocardial-infarcted rats

Cardiomyoplasty has been proposed as an alternative surgical treatment for congestive heart failure. The girdling effect of the muscle wrap is believed to reduce diastolic wall stress. We tested the hypothesis that nonstimulated or passive cardiomyoplasty (CDM) would reduce hemodynamic deficits in rats with experimentally induced myocardial infarction (MI). Four groups of animals were studied: intact (C, n = 6), CDM (n = 6), MI by ligation of the left coronary artery (n = 6), and left latissimus dorsi CDM performed 14 days post-MI (MI + CDM, n = 6). All groups were studied 8 weeks after MI and/or CDM or from the beginning of the experiment in controls. MI rats had a lower mean arterial pressure and higher end-diastolic pressure (EDP) compared with controls. End-diastolic pressure (EDP) and the left ventricular-body weight ratio (LV/BW) were reduced in the MI group after CDM. These data suggest that passive girdling of the heart provided by CDM may improve post-MI cardiac function.

Surgical treatments for heart failure

The surgical options for CHF are a part of a larger paradigm shift in management. Viable and effective surgical options other than cardiac transplant and ventricular assist devices clearly exist and are applicable to a large portion of patients with CHF. These surgical therapies are of acceptable risk before decompensated CHF develops. The rapidly evolving therapies for altering LV remodeling, which underlies CHF progression, are an exciting area that may be joined in the future by molecular advances in myoblast transfer and gene therapy. These therapies are the basis of the discipline of CHF surgery within cardiovascular surgery.

Dynamic cardiomyoplasty as a therapeutic alternative: current status

Dynamic cardiomyoplasty was proposed as an alternative surgical treatment for severe cardiomyopathies and has been performed worldwide in more than 1,000 patients. Patients indicated for this procedure are specifically those with dilated or ischemic cardiomyopathies. The ventricular function improvement observed after dynamic cardiomyoplasty derived from the direct action of synchronized skeletal muscle flap contraction and from a girdling effect that helps to reverse chamber remodeling and to decrease ventricular wall stress. Although long-term benefits of this procedure may be limited by skeletal muscle flap ischemic compromise, technological advances incorporated in the new myostimulators will possibly decrease this complication incidence. Clinical improvement has been reported as a consistent finding in cardiomyoplasty follow-up and the overall 5-year survival after this procedure ranges from 39 % to 54 %. On the other hand, the mortality after cardiomyoplasty has been significantly higher for patients in persistent New York Heart Association functional class IV, showing that this procedure needs to be indicated earlier than the heart transplantation. In this regard, only the results of an ongoing randomized trial will potentially define cardiomyoplasty influence on the survival of patients with severe heart failure. In the meantime, however, there are clearly several functional class III patients whose quality of life and exercise capacity have worsened despite the use of maximum medical therapy, justifying dynamic cardiomyoplasty indication.

The effect of cardiomyoplasty on left atrial function in experimental canine models

BACKGROUND

Cardiomyoplasty utilizes the latissimus dorsi muscle to boost the failing ventricle. However, the mechanism for clinical improvement still remains controversial. We have previously shown that left ventricular contraction was improved in the long-term periods after cardiomyoplasty in the normal canine heart model and in the dilated failing heart model. On the other hand, right ventricular filling was impaired if a rapid volume loading test was employed in the long-term period after cardiomyoplasty. The purpose of the present study was to determine whether cardiomyoplasty impairs the left atrial function and affects ventricular filling.

METHOD

Eleven mongrel dogs that had undergone cardiomyoplasty (study group, n = 5) or a sham operation (control group, n = 6) were studied for 12 weeks postoperatively. An IV 4.5% albumin solution (10 mL/kg) was infused into the right atrium, and hemodynamic changes in right cardiac catheterization and left atrial volume (LAV) were obtained by two-dimensional echocardiography. Atrial function was assessed by hemodynamic changes in Doppler echocardiography and hormonal changes.

RESULTS

Stroke volume was significantly increased, from 17.0 +/- 4.4 to 21.1 +/- 7.0 mL, respectively, before and 15 min after albumin infusion in the control group (p < 0.05). Heart rate and cardiac output were significantly increased, from 131.2 +/- 18.1 to 152.0 +/- 9.8 beats/min and 2.72 +/- 1.29 to 4.03 +/- 1.67 L/min, respectively, before and 15 min after albumin infusion in the study group (p < 0.05). No changes were observed in mean right atrial pressure and pulmonary capillary wedge pressure. LAV and atrial natriuretic peptide (ANP) levels increased significantly, from 5.8 +/- 2.1 to 8.5 +/- 3.8 mL and 22.5 +/- 7.5 to 44.5 +/- 31.7 pg/mL, respectively, before and 15 min after albumin infusion in the control group (p < 0.05). In the study group, LAV and ANP levels were also increased, from 10.1 +/- 2.4 to 12.7 +/- 2.8 mL and 64.2 +/- 60.6 to 232.6 +/- 272.2 pg/mL, respectively, before and 15 min after albumin infusion (p < 0.05). The peak velocities and the time-velocity integrals in the pulmonary venous flow of the systolic and diastolic waves, as well as their ratios (systolic to diastolic peak velocity ratio and systolic to diastolic time-velocity integral ratio) showed no significant differences between the two groups.

CONCLUSIONS

Cardiomyoplasty preserves left atrial filling and transport function; therefore, cardiomyoplasty may also activate ANP production by stimulating the atrium in the long-term period after cardiomyoplasty.

Adult cardiac myocytes survive and remain excitable during long-term culture on synthetic supports

OBJECTIVE

Cardiomyocytes can be transplanted successfully into skeletal and cardiac muscle. Our goal was to determine the feasibility of grafting cardiomyocytes onto various synthetic supports to create an excitable and viable tissue for implantation.

METHODS

Adult rat cardiomyocytes were cultured over an 8-week period onto different substitutes, including human glutaraldehyde-treated pericardium (n = 3), equine glutaraldehyde-treated pericardium (n = 3), polytetrafluoroethylene (n = 8), Dacron polyester (n = 16), and Vicryl polyglactin (n = 8).

RESULTS

Only the cells seeded on the Dacron survived, with the synthetic fibers colonized at 8 weeks. On the other supports, the number of myocytes progressively decreased from the first week, with their density (number of cells per square millimeter) being, after 20 days, 17 +/- 2 on the polytetrafluoroethylene and 5 +/- 1 on the human or equine pericardium compared with 45 +/- 3 on the Dacron. After 8 weeks of culture on Dacron, the sarcomeric protein (sarcomeric alpha-actinin) was detected in all cells. In addition, the staining was regularly arranged and well aligned in a striated pattern. Spontaneous beating activity was obtained. Moreover, electrical stimulation of the cell preparation resulted in the generation of calcium transients, the frequency of which followed the frequency of the electrical stimulation.

CONCLUSIONS

These results suggest that adult cardiac myocytes remain viable and excitable during long-term culture on a 3-dimensional Dacron support, which might constitute a new synthetic cardiac tissue.

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.

Basic design and construction of the Vienna FES implants: existing solutions and prospects for new generations of implants

We can distinguish 3 generations of FES implants for activation of neural structures: 1. RF-powered implants with antenna displacement dependent stimulation amplitude; 2. RF-powered implants with stabilised stimulation amplitude; and 3. battery powered implants. In Vienna an 8-channel version of the second generation type has been applied clinically to mobilisation of paraplegics and phrenic pacing. A 20-channel implant of the second generation type for mobilisation of paraplegics and an 8-channel implant of the third generation type for cardiac assist have been tested in animal studies. A device of completely new design for direct stimulation of denervated muscles is being tested in animal studies. There is a limited choice of technologically suitable biocompatible and bioresistant materials for implants. The physical design has to be anatomically shaped without corners or edges. Electrical conductors carrying direct current (D.C.) have to be placed inside a hermetic metal case. The established sealing materials, silicone rubber and epoxy resin, do not provide hermeticity and should only embed DC-free components. For electrical connections outside the hermetic metal case welding is preferable to soldering; conductive adhesives should be avoided. It is advisable to use a hydrophobic oxide ceramic core for telemetry antenna coils embedded in sealing polymer. Cleaning of all components before sealing in resin is of the utmost importance as well as avoidance of rapid temperature changes during the curing process.

Oxidative stress in the latissimus dorsi muscle of diabetic rats

The purpose of the present study was to investigate the effects of experimental diabetes on the oxidant and antioxidant status of latissimus dorsi (LD) muscles of male Wistar rats (220 +/- 5 g, N = 11). Short-term (5 days) diabetes was induced by a single injection of streptozotocin (STZ, 50 mg/kg, iv; glycemia >300 mg/dl). LD muscle of STZ-diabetic rats presented higher levels of thiobarbituric acid reactive substances (TBARS) and chemiluminescence (0.36 +/- 0.02 nmol/mg protein and 14706 +/- 1581 cps/mg protein) than LD muscle of normal rats (0.23 +/- 0.04 nmol/mg protein and 7389 +/- 1355 cps/mg protein). Diabetes induced a 92% increase in catalase and a 27% increase in glutathione S-transferase activities in LD muscle. Glutathione peroxidase activity was reduced (58%) in STZ-diabetic rats and superoxide dismutase activity was similar in LD muscle of both groups. A positive correlation was obtained between catalase activity and the oxidative stress of LD, as evaluated in terms of TBARS (r = 0.78) and by chemiluminescence (r = 0.89). Catalase activity also correlated inversely with glutathione peroxidase activity (r = 0.79). These data suggest that an increased oxidative stress in LD muscle of diabetic rats may be related to skeletal muscle myopathy.

Functional assessment of skeletal muscle ventricles after pumping for up to four years in circulation

BACKGROUND

The successful treatment of cardiac failure by heart transplantation is severely limited by the shortage of donor organs, and alternative surgical approaches are needed. An experimental approach that holds considerable promise is the skeletal muscle ventricle (SMV), an auxiliary blood pump formed from a pedicled graft of latissimus dorsi muscle and connected to the circulation in a cardiac assist configuration. Adaptive transformation, or conditioning, by electrical stimulation enables the skeletal muscle to perform a significant proportion of cardiac work indefinitely without fatigue.

METHODS

In 10 dogs, SMVs were constructed from the latissimus dorsi muscle, lined internally with pericardium, and conditioned by electrical stimulation to induce fatigue resistant properties. The SMVs were connected to the descending thoracic aorta via two 12-mm Gore-Tex conduits and the aorta was ligated between the two grafts. The SMV was stimulated to contract during the diastolic phase of alternate cardiac cycles. The animals were monitored at regular intervals.

RESULTS

At initial hemodynamic assessment, SMV contraction augmented mean diastolic blood pressure by 24.6% (from 61 +/- 7 to 76 +/- 9 mm Hg). Presystolic pressure was reduced by 15% (from 60 +/- 8 to 51 +/- 7 mm Hg) after an assisted beat. Four animals died early, 1 from a presumed arrhythmia, and 3 during propranolol-induced hypotension. The other 6 animals survived for 273, 596, 672, 779, 969, 1,081, and 1,510 days. Diastolic augmentation was 27.4% at 1 year (93 +/- 9 vs 73 +/- 6 mm Hg; n = 5), 34.7% at 2 years (85 +/- 6 vs 63 +/- 7 mm Hg; n = 3), 21.2% (89 +/- 10 vs 73 +/- 8 mm Hg; n = 2) at 3 years, and 34.5% (78 vs 58 mm Hg; n = 1) after 4 years in circulation. After 4 years, the isolated SMV was able to maintain a pressure of over 80 mm Hg while ejecting fluid at 20 mL/s. No animal showed evidence of SMV rupture or thromboembolism.

CONCLUSIONS

The SMVs in this study provided effective and stable hemodynamic assistance over an extended period of time. There was no evidence that the working pattern imposed on the muscular wall of the SMV compromised its viability. Areas of fibrofatty degeneration were suggestive of early damage that future protocols should seek to minimize.

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.

What does chronic electrical stimulation teach us about muscle plasticity?

The model of chronic low-frequency stimulation for the study of muscle plasticity was developed over 30 years ago. This protocol leads to a transformation of fast, fatigable muscles toward slower, fatigue-resistant ones. It involves qualitative and quantitative changes of all elements of the muscle fiber studied so far. The multitude of stimulation-induced changes makes it possible to establish the full adaptive potential of skeletal muscle. Both functional and structural alterations are caused by orchestrated exchanges of fast protein isoforms with their slow counterparts, as well as by altered levels of expression. This remodeling of the muscle fiber encompasses the major, myofibrillar proteins, membrane-bound and soluble proteins involved in Ca2+ dynamics, and mitochondrial and cytosolic enzymes of energy metabolism. Most transitions occur in a coordinated, time-dependent manner and result from altered gene expression, including transcriptional and posttranscriptional processes. This review summarizes the advantages of chronic low-frequency stimulation for studying activity-induced changes in phenotype, and its potential for investigating regulatory mechanisms of gene expression. The potential clinical relevance or utility of the technique is also considered.

Battery-powered miniature implant for electrical nerve stimulation

The range of application of implantable stimulators in functional electrical stimulation (FES) for therapeutic purposes and for the restoration of lost or damaged functions has steadily grown within the last 20 years. Each time a clinically used method is improved, a new field of FES application explored or basic research conducted, animal experiments are needed to check and evaluate the findings and results. It is precisely for this use that the stimulation system described in this paper was developed. The battery-powered single-channel stimulator can be used for the excitation of motor and sensory nerves with monophasic or biphasic impulses. All parameters and functions are programmable via the bidirectional telemetry circuit. Implant programming is achieved by a laptop computer, supported by a graphical user interface, instead of by a specially designed programmer. The maximum settings of the stimulation parameters are: frequency 100 Hz, monophasic pulse duration 0.8 ms, biphasic pulse duration 1.6 ms, stimulation current 3 mA. The implant volume was reduced to 2 cm3 (length 23 mm, width 13 mm, height 7.5 mm), lowering the weight to 3.6 g. Due to this small volume the implant can be used in small animals. The power supply via battery obviates the need for transcutaneous tunneling or permanent external high-frequency senders and facilitates the keeping of the animals.

Multifunctional implantable nerve stimulator for cardiac assistance by skeletal muscle

Different methods are used, clinically and experimentally, to assist severely impaired heart function by means of skeletal muscle. The efficiency of these methods is restricted by skeletal muscle losing strength after transpositioning and during conditioning and not being sufficiently resistant to fatigue. This is mainly due to the nonphysiological activation of the nerves by electrical stimulation. We have developed a battery operated, ECG triggered multichannel implant that is capable of implementing various advanced stimulation techniques. The stimulator can activate 2 skeletal muscles via the motor nerves. It allows for application of multichannel stimulation methods, i.e., carousel stimulation and sequential stimulation, as well as the programming of optimized pulse trains. Synchronization delay and burst duration can be automatically and dynamically adapted to the heart rate. The multichannel stimulator is hermetically sealed in a titanium case. Its calculated life span on the basis of the integrated battery is 3-5 years, depending on the programmed stimulation parameters. The implant dimensions are 65 x 17 mm (diameter x height), and it weighs 93 g. The implant has been tested in vitro as well as in vivo.