Tissue-engineered cardiac constructs for cardiac repair.

Several recent basic research studies have described surgical methods for cardiac repair using tissue cardiomyoplasty. This review summarizes recent advances in cardiac repair using bioengineered tissue from the viewpoint of the cardiac surgeon. We conclude that the results of many basic and preclinical studies indicate that bioengineered tissue can be adapted to conventional surgical techniques. However, no clinical studies have yet proved bioengineered tissue is effective as a treatment for human heart failure. Today's cardiac surgeons can look forward to the advent of new techniques to benefit patients who respond poorly to existing treatment for heart failure.

Cellular cardiomyoplasty: routes of cell delivery and retention.

Experimental and clinical studies have proven the feasibility of cellular cardiomyoplasty in treating the damaged myocardium following ischemic injury. Over the years, this field has exploded with different investigators trying different routes of cell delivery ranging from direct cell injection into the heart to peripheral intravenous delivery utilizing the various signaling mechanisms known. These different routes have resulted in a wide range of retention and engraftment of cells in the target tissues. In this review, we will explore the different modalities of cell delivery, the pros and cons of each route and the cellular retention and therapeutic efficacy of these routes. We will then look into the different theories that try to explain the observed retention and engraftment of cells in the target tissues. Finally, we will discuss various methods that can improve cellular retention and engraftment and hence better improvement in myocardial function.

Study of muscular and ventricular function in dynamic cardiomyoplasty: a ten-year follow-up.

BACKGROUND: The basic physiologic principle underlying cardiomyoplasty is long-term electrostimulation of a latissimus dorsi muscle (LDM) wrapped around the heart to obtain a phasic activity that could be integrated with ventricular kinetics. The aim of cardiomyoplasty is to prolong survival and to improve the quality of life of patients with severe chronic and irreversible myocardial failure by improving systolic contraction and correcting diastolic dysfunction. METHODS: To evaluate the long-term outcome of cardiomyoplasty, we investigated 82 patients electively undergoing this procedure in-our hospital. All patients had severe chronic heart failure that did not respond to optimal medical treatment. Patients had a mean age of 50 +/- 12 years (84% males). The cause of heart failure was ischemic (55%), idiopathic cardiomyopathy (34%), ventricular tumor (6%), and other (5%). The mean follow-up was 4.3 years. RESULTS: The mean New York Heart Association functional class improved after operation from 3.2 to 1.8. Average radioisotopic left ventricular ejection fraction increased from 17% +/- 6% to 28% +/- 3% (p < 0.05). Stroke volume index increased from 35 +/- 9 to 46 +/- 8 ml/beat/m2 (p < 0.05). The heart size remained stable at long term (evaluated by echo and computed tomography scanning). After cardiomyoplasty the number of successive hospitalizations resulting from congestive heart failure was reduced to 0.4 hospitalizations/patient/year (before operation 2.5, p < 0.05). Computed tomography scans showed at long-term a preserved LDM structure in 82% of patients who underwent operation. Survival probability at 7 years was 54% for the totality of patients, and 66% for patients who underwent operation in New York Heart Association functional class 3. Five patients underwent heart transplantation after cardiomyoplasty (mean delay 29 months), principally as a result of the natural evolution of their underlying heart disease, without major technical difficulties. CONCLUSIONS: Our 10-year clinical experience demonstrates that cardiomyoplasty increases ejection fraction, improves functional class, and ameliorates quality of life. Ventricular volumes and diameters remain stable long term. LDM structure is maintained long term if electrostimulation is performed avoiding excessive myostimulation. Patient selection is the most important determinant for early and late outcome. Late death in patients undergoing cardiomyoplasty is principally due to sudden death. Our future aim is to incorporate a cardioverter-defibrillator in the cardiomyostimulator, thus improving long-term results. Cardiomyoplasty may delay or prevent end-stage heart failure and the need for heart transplantation.

[Surgical alternatives to direct repeat revascularization of coronary arteries--common mechanisms for reducing ventricular volume, laser transmyocardial revascularization and cardiomyoplasty]. / Alternatives chirurgicales á la revascularisation directe itérative des artéres coronaires--mécanismes communs de la réduction du volume ventriculaire, de la revascularisation transmyocardique au laser et de la cardiomyoplastie.

There are a number of surgical alternatives to repeat artery bypass grafting, which is the primary treatment for recurrent severe myocardial ischemia. In patients with endstage coronary artery disease unsuitable for repeat bypass procedures, orthotopic heart transplantation is now well established. However, the increasing donor shortage limits this option to relatively few patients, a fact well documented by longer waiting lists despite less stringent donor criteria. Hence, other surgical therapies, which may at this time be underused, should be explored. In addition to mechanical circulatory support by means of implantable blood pumps which are now available with wearable drivers and rechargeable batteries, mention should be made of surgical left ventricular volume reduction and reverse remodeling, transmyocardial laser revascularization (TMR), and dynamic cardiomyoplasty. The mechanisms that explain the beneficial effects of the three latter procedures are not fully understood. But it may be speculated for these procedures that Laplace and Starling laws play a major role in the sometimes spectacular recovery. It is probably due to the complexity of the procedures mentioned, the severe condition of the patients, the high risk of a proactive attitude under such circumstances, and the significant cost, that the number of these alternative procedures performed is still rather low despite the fact that the results are similar to those of transplantation. However, careful individual evaluation is of prime importance for better results. The presence or absence of symptoms is certainly a major issue for the decision-making process. If the left ventricular ejection fraction is preserved, transmyocardial laser revascularisation may relieve angina. Dynamic cardiomyoplasty may be appropriate if the left ventricular ejection fraction is low, provided the heart is not too big and that there is neither too much mitral regurgitation nor major arrhythmia. If the left ventricle is very big and major mitral regurgitation is present, volume reduction giving transventricular access to the mitral valve can be evaluated. A decision-making tree is proposed.

[Circulatory support by an electrically stimulated muscle flap. Experimental experiences]. / Kreislaufunterstützung durch elektrisch stimulierte Muskellappen. Experimentelle Erfahrungen.

Functional electrical stimulation of the latissimus dorsi muscle flap for circulatory assistance extends the traditional concept of using this flap for reconstructive procedures into the field of cardiac surgery. It requires a transformed muscle which is able to contract for long periods of time without fatigue. Two main groups of experiments have been carried out in sheep. In six sheep the latissimus dorsi muscle (MLD) was transformed into a fatigue-resistant muscle by the means of multichannel stimulation of the supplying motor nerve. After that, stimulation of MLD at a frequency of 70 contractions per minute could be performed continuously without significant muscle fatigue. The loss of maximal force caused by the conditioning procedure was about one third of the initial force. In a second series of acute experiments the MLD was used for cardiomyoplasty. The muscle was divided into two parts which were wrapped around the heart in two different forms. The resting tension of the muscle was preserved. EKG-synchronous stimulation resulted in an increase in left ventricular pressure between 12 and 53%. The increase in arterial pressure was between 10,6 and 58%.

Clinical results of dynamic cardiomyoplasty.

Thirty-five cardiomyoplasty procedures were performed in five patients with dilated and 30 patients with ischemic cardiomyopathies. Russian-made cardiomyostimulators (CMS) were implanted in these patients. Twenty-one patients underwent a one-step procedure using a left thoracotomy for cardiomyoplasty, while in 14 patients, a two-step procedure that included a mid-line sternotomy was carried out. During the average follow-up period of 9 +/- 2.1 months, studies were carried out that showed in survivors improved clinical functional status and decreased heart failure symptoms. Evidence of revascularization of the ischemic myocardium from the latissimus dorsi muscle (LDM) wrap was obtained by angiography and radioactive scintigraphy. In five patients, the CMS had to be removed due to complications, and in all these patients, their clinical functional status deteriorated following the cessation of cardiomyostimulation.

Efficacy of a skeletal muscle-powered dynamic patch: Part 1. Left ventricular assistance.

In this study, we examined the capability of a skeletal muscle-powered, dynamic patch to provide left ventricular assistance. An actuator was developed that used linear traction power furnished by the latissimus dorsi muscle and liquid as the medium for power transfer. The proximal portion of the muscle was dissected and was reattached to the actuator. The left ventricular apex was excised, and the dynamic patch lined with autologous pericardium was implanted during cardiopulmonary bypass. Hemodynamic studies were performed in 8 dogs after weaning from cardiopulmonary bypass. Muscle stimulation was found to significantly increase the systolic aortic pressure (91.6 versus 112.1 mm Hg; p < 0.01), the mean aortic pressure (65.2 versus 73.0 mm Hg; p < 0.01), and aortic blood flow (0.77 versus 0.92 L/min; p < 0.01). The left atrial pressure decreased from 17.9 to 16.6 mm Hg (p < 0.01). This "hybrid" left ventricular assist device possesses notable clinical advantages because of its remarkable efficacy in assisting circulation. Further experimental studies using preconditioned skeletal muscle are necessary to assess the long-term effects of this technique.