Clinical cardiomyoplasty: review of the ten-year United States experience

Cardioprotective effect of silicon-built restraint device (ASD), for left ventricular remodeling in rat heart failure model

This study aims to evaluate the feasibility and cardio-protective effects of biocompatible silicon-built restraint device (ASD) in the rat's heart failure (HF) model. The performance and compliance characteristics of the ASD device were assessed in vitro by adopting a pneumatic drive and ball burst test. Sprague-Dawley (SD) rats were divided into four groups (n = 6); control, HF, HF + CSD, and HF + ASD groups, respectively. Heart failure was developed by left anterior descending (LAD) coronary artery ligation in all groups except the control group. The ASD and CSD devices were implanted in the heart of HF + ASD and HF + CSD groups, respectively. The ASD's functional and expansion ability was found to be safe and suitable for attenuating ventricular remodeling. ASD-treated rats showed normal heart rhythm, demonstrated by smooth -ST and asymmetrical T-wave. At the same time, hemodynamic parameters of the HF + ASD group improved systolic and diastolic functions, reducing ventricular wall stress, which indicated reverse remodeling. The BNP values were reduced in the HF + ASD group, which confirmed ASD feasibility and reversed remodeling at a molecular level. Furthermore, the HF + ASD group with no fibrosis suggests that ASD has significant curative effects on the heart muscles. In conclusion, ASD was found to be a promising restraint therapy than the previously standard restraint therapies. Stepwise ASD fabrication process (a) 3D computer model of ASD was generated by using Rhinoceros 5.0 software (b) 3D blue wax model of ASD (c) Silicon was prepared by mixing the solutions (as per manufacturer instruction) (d) Blue wax model of ASD was immersed into liquid Silicon (e) ASD model was put into the oven for 3 hours at 50 °C. (f) Blue wax started melting from the ASD model (g) ASD model was built from pure silicon (h) Two access lines were linked to the ASD device, which was connected with an implantable catheter (Port-a-cath), scale bar 100 µm. (Nikon Ldx 2.0).

The use of soft robotics in cardiovascular therapy

INTRODUCTION

Robots have been employed in cardiovascular therapy as surgical tools and for automation of hospital systems. Soft robots are a new kind of robot made of soft deformable materials, that are uniquely suited for biomedical applications because they are inherently less likely to injure body tissues and more likely to adapt to biological environments. Awareness of the soft robotic systems under development will help promote clinician involvement in their successful clinical translation. Areas covered: The most advanced soft robotic systems, across the size scale from nano to macro, that have shown the most promise for clinical application in cardiovascular therapy because they offer solutions where a clear therapeutic need still exists. We discuss nano and micro scale technology that could help improve targeted therapy for cardiac regeneration in ischemic heart disease, and soft robots for mechanical circulatory support. Additionally, we suggest where the gaps in the technology currently lie. Expert commentary: Soft robotic technology has now matured from the proof-of-concept phase to successful animal testing. With further refinement in materials and clinician guided application, they will be a useful complement for cardiovascular therapy.

Exo-organoplasty interventions: A brief review of past, present and future directions for advance heart failure management

Heart failure (HF) is a debilitating disease in which abnormal function of the heart leads to imbalance of blood demand to tissues and organs. The pathogenesis of HF is very complex and various factors can contribute including myocardial infarction, ischemia, hypertension and genetic cardiomyopathies. HF is the leading cause of death and its prevalence is expected to increase in parallel with the population age. Different kind of therapeutic approaches including lifestyle modification, medication and pacemakers are used for HF patients in NYHA I-III functional class. However, for advance stage HF patient's (NYHA IV), ventricle assist devices are clinically use and stem cells are under active investigation. Most of these therapies leads to modest symptoms relief and have no significant role in long-term survival rate. Currently there is no effective treatment for advance HF except heart transplantation, which is still remain clinically insignificant because of donor pool limitation. As HF is a result of multiple etiologies therefore multi-functional therapeutic platform is needed. Exo-organoplasty interventions are studied from almost one century. The major goals of these interventions are to treat various kind of heart disease from outside the heart muscle without having direct contact with blood. Various kind of interventions (devices and techniques) are developed in this arena with the passage of time. The purpose of this review is to describe the theory behind intervention devices, the devices themselves, their clinical results, advantages and limitations. Furthermore, to present a future multi-functional therapeutic platform (ASD) for advance stage HF management.

Cardiac assist with a twist: apical torsion as a means to improve failing heart function

Changes in muscle fiber orientation across the wall of the left ventricle (LV) cause the apex of the heart to turn 10-15 deg in opposition to its base during systole and are believed to increase stroke volume and lower wall stress in healthy hearts. Studies show that cardiac torsion is sensitive to various disease states, which suggests that it may be an important aspect of cardiac function. Modern imaging techniques have sparked renewed interest in cardiac torsion dynamics, but no work has been done to determine whether mechanically augmented apical torsion can be used to restore function to failing hearts. In this report, we discuss the potential advantages of this approach and present evidence that turning the cardiac apex by mechanical means can displace a clinically significant volume of blood from failing hearts. Computational models of normal and reduced-function LVs were created to predict the effects of applied apical torsion on ventricular stroke work and wall stress. These same conditions were reproduced in anesthetized pigs with drug-induced heart failure using a custom apical torsion device programmed to rotate over various angles during cardiac systole. Simulations of applied 90 deg torsion in a prolate spheroidal computational model of a reduced-function pig heart produced significant increases in stroke work (25%) and stroke volume with reduced fiber stress in the epicardial region. These calculations were in substantial agreement with corresponding in vivo measurements. Specifically, the computer model predicted torsion-induced stroke volume increases from 13.1 to 14.4 mL (9.9%) while actual stroke volume in a pig heart of similar size and degree of dysfunction increased from 11.1 to 13.0 mL (17.1%). Likewise, peak LV pressures in the computer model rose from 85 to 95 mm Hg (11.7%) with torsion while maximum ventricular pressures in vivo increased in similar proportion, from 55 to 61 mm Hg (10.9%). These data suggest that: (a) the computer model of apical torsion developed for this work is a fair and accurate predictor of experimental outcomes, and (b) supra-physiologic apical torsion may be a viable means to boost cardiac output while avoiding blood contact that occurs with other assist methods.

Stem cell transplantation: potential impact on heart failure

Cell transplantation is a promising new modality in treating damaged myocardium after myocardial infarction and in preventing postmyocardial infarction LV remodelling. Two strategies are plausible: the first uses adult tissue stem cells to replace the scar tissues and amend the lost myocardium, whilst the second strategy uses embryonic stem cells in an attempt to regenerate myocardium and/or blood vessels.

Differential expression of the fast skeletal muscle proteome following chronic low-frequency stimulation

Physiological and biochemical responses of skeletal muscle fibres to enhanced neuromuscular activity under conditions of maximum activation can be studied experimentally by chronic low-frequency stimulation of fast muscles. Stimulation-induced changes in the expression pattern of the rabbit fast skeletal muscle proteome were evaluated by two-dimensional gel electrophoresis and compared to the altered isoform expression profile of established transformation markers such as the Ca2+-ATPase, calsequestrin and the myosin heavy chain. Sixteen muscle proteins exhibited a marked change in their expression level. This included albumin with a 4-fold increase in abundance. In contrast, glycolytic enzymes, such as enolase and aldolase, showed a decreased expression. Concomitant changes were observed with marker elements of the contractile apparatus. While the fast isoforms of troponin T and myosin light chain 2 were drastically down-regulated, their slow counterparts exhibited increased expression. Interestingly, mitochondrial creatine kinase expression increased while the cytosolic isoform of this key muscle enzyme decreased. The expression of the small heat shock protein HSP-B5/alphaB-crystallin and the oxygen carrier protein myoglobin were both increased 2-fold following stimulation. The observed changes indicate that the conversion into fatigue-resistant red fibres depends on: (i) the optimum utilization of free fatty acids via albumin transportation, (ii) a rearrangement of the creatine kinase isozyme pattern for enhanced mitochondrial activity, (iii) an increased availability of oxygen for aerobic metabolism via myoglobin transport, (iv) the conversion of the contractile apparatus to isoforms with slower twitch characteristics and (v) the up-regulation of chaperone-like proteins for stabilising myofibrillar components during the fast-to-slow transition process.

Ischemic Preconditioning of Skeletal Muscle

BACKGROUND

The time course of the late phase of ischemic preconditioning (IPC) was determined in latissimus dorsi muscle (LDM) flaps using viability and function as the endpoints.

MATERIALS AND METHODS

LDM flaps from Sprague-Dawley rats were allocated into 6 groups. LDMs were preconditioned with 2 30-minute periods of ischemia separated by 10 minutes of reperfusion and subjected to a 4-hour ischemic insult after 24, 48, 72, and 96 hours from IPC. LDMs were evaluated for percent necrosis and muscle contractile function and compared with controls.

RESULTS

The late phase of IPC provides significant protection against necrosis up to 72 hours. Conversely, when the end point used was muscle contractile function, the protection only lasted 48 hours.

CONCLUSION

The time course of late-phase protection in skeletal muscle is 2-3 days. Late phase IPC appears to protect muscle flaps during the most critical time period following elevation.

Safety and Biocompatibility of the Myosplint System—A Passive Implantable Device That Alters Ventricular Geometry for the Treatment of Heart Failure

A passive implantable device developed for the treatment of heart failure, the Myosplint System, has demonstrated therapeutic efficacy in a canine model of pacing induced heart failure. The current study sought to demonstrate chronic device safety and biocompatibility, in vivo, in a normal porcine model. Two devices were implanted into each normal, beating heart of 6 juvenile and 15 adult pigs without cardiopulmonary bypass. Animals survived 90 (juvenile and adult) or 180 days (adult only). Serial hematologic and biochemical profiles were evaluated in each pig during the study period. A comprehensive necropsy study was performed in each pig to evaluate device stability, healing response, thromboembolism, hemorrhage, and intravascular hemolysis related to the Myosplint system. Six adult animals died from infectious disease (four) or perioperative (two) complications unrelated to device design or function and were excluded from the final analysis. No clinical, biochemical or pathologic evidence of significant, device related adverse events was observed in surviving animals. The chronic myocardial healing response appeared normal at term, and all devices maintained their structural integrity throughout the study. The Myosplint system was easily implanted in beating hearts and was rapidly incorporated into host tissues without clinically significant morbidity in this porcine model.

"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.

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.

Growth factors improve latissimus dorsi muscle vascularization and trophicity after cardiomyoplasty

BACKGROUND

Dynamic cardiomyoplasty consists of wrapping the electrostimulated latissimus dorsi muscle (LDM) around the failed heart. Partial ischemia followed by atrophy of the middle and distal part of the LDM were observed in 30% of clinical cases after LDM flap elevation from its origin. In the current study, we hypothesized that local administration of growth factors at the LDM/epicardial interface could improve muscle vascularization and trophicity.

METHODS

In 24 sheep, dynamic cardiomyoplasty was performed using the left LDM. A multiperforated catheter was positioned at the LDM/epicardial interface for a weekly administration, during a 1-month period, of the following factors: basic fibroblast growth factor (bFGF, n = 6), vascular endothelial growth factor (VEGF, n = 6), and regenerating agent (RGTA, n = 6). Six sheep injected with phosphate-buffered saline (used for dilution of the growth factors) were used as a control group. At 3 months, angiographic, histologic, and histomorphometric studies were performed.

RESULTS

Angiographic studies of the animals treated with growth factors demonstrated hypervascularization due to the development of new vessels. Histomorphometric and histologic studies showed a significant increase in the number of capillaries and arterioles (100 fields/muscle) in the groups treated with bFGF (443.0 +/- 101.2, p < 0.01), RGTA (293.2 +/- 29.3, p < 0.05), and VEGF (246.5 +/- 45.9, p < 0.05), as compared with the control group (81.5 +/- 11.4). A significantly lower atrophy score was observed in the groups treated with bFGF (1.4 +/- 0.18, p < 0.05), RGTA (1.59 +/- 0.17, p < 0.05), and VEGF (1.96 +/- 0.14, NS), as compared with the control group (2.48 +/- 0.16).

CONCLUSIONS

Local administration at the heart/muscle interface of growth factors increases muscle vascularization and avoids muscle atrophy in an experimental cardiomyoplasty model, both of which are advantageous to the contracting LDM. The local growth factors delivery system used in this study appears efficient, easy to implant, and manipulate and safe.

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.

Effects of acute dynamic cardiomyoplasty in a goat model of chronic ventricular dilatation: part 1

BACKGROUND

The acute effects of cardiomyoplasty in an experimental model of chronic dilated heart have not been thoroughly investigated. Therefore, a model of chronic left ventricular (LV) dilatation was created to accurately determine actual changes shortly after passive and active wrapped skeletal muscle.

METHODS

A carotid-jugular shunt model in 8 goats was used to induce progressive dilatation of the cardiac ventricles. Geometric modifications induced by the arteriovenous shunt were monitored by transthoracic echocardiography. After 8 weeks, cardiomyoplasty was performed, and the acute hemodynamic changes obtained with static cardiomyoplasty soon after the wrapping procedure were determined. Hence, hemodynamic variables recorded during assisted cardiac beats were then compared with data collected with unassisted cardiac beats using the conductance catheter method to generate pressure-volume loops.

RESULTS

During electrical stimulation of the unconditioned skeletal muscle wrapped around the dilated left ventricle, a significant increase in stroke volume (117 +/- 48 mL versus 87 +/- 38 mL; p < 0.05) was observed. Early wrapped latissimus dorsi muscle activation also induced a reduction in LV end-systolic volume (from 51 +/- 28 mL to 27 +/- 14 mL; p < 0.05) when compared with unassisted LV contraction.

CONCLUSIONS

In a chronic model of cardiac dilatation, acute dynamic cardiomyoplasty was shown to increase LV contractile performance and reduce LV volume. Further evaluation is necessary to show the effects of a conditioned wrapped muscle on LV systolic function and dimensions in the long-term.

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.

Can latissimus dorsi muscle stimulation benefit heart during training period after vascular delay?

We hypothesized that a two-stage vascular delay procedure followed by 5 weeks of conditioning of the latissimus dorsi muscle (LDM) could benefit the heart during the training period and greatly increase cardiac assistance when examined with maximum potential. In mongrel dogs (n = 10), left ventricle (LV) dysfunction was induced by intracoronary injections of latex microspheres [90 +/- 2 micro diameter]. Vascular delay of the LDM was performed in one group (n = 6), whereas the other group (control, n = 4) did not undergo vascular delay. After 2 weeks, CMP was performed in all animals followed by LDM conditioning. After 5 weeks of muscle training, we examined left ventricular function at 20 Hz-4 volts, 33 Hz-4 volts, and 50 Hz-10 volts stimulation by assessing peak aortic pressure (AoP), left ventricular pressure (LVP), maximum LV +dP/dt, stroke volume (SV), stroke work (SW), stroke power (SP), and aortic flow. LDM assisted beats were compared with nonstimulated beats. LDM stimulation caused significant increases in pressure and flow in the vascular delay group. At 20 Hz-4 volts, absolute increases were LVP (10.2 +/- 0.6) mm Hg, AoP (9.8 +/- 1.7) mm Hg, SV (1.8 +/- 0.4) ml, SW (5.3 +/- 1.0) gm x m, SP (40.8 +/- 12.7) gm x m/sec, max LV dP/dt (104.8 +/- 53.2) mm Hg/sec, and peak aortic flow (0.9 +/- 0.3) L/min. At 33 Hz-4 volts, the absolute increases were LVP (13.6 +/- 1.3) mm Hg, AoP (12.1 +/- 2.4) mm Hg, SV (2.7 +/- 0.7) ml, SW (7.4 +/- 1.4) gm x m, SP (72.7 +/- 16.5) gm x m/sec, max LV dP/dt (294 +/- 19) mm Hg/sec, and peak aortic flow (1.8 +/- 0.5) L/min. At 50 Hz-10 volts, the absolute increases were LVP (17.7 +/- 0.7) mm Hg, AoP (21.1 +/- 1.9) mm Hg, SV (6.0 +/- 1.1) ml, SW (14.6 +/- 2.2) gm.m, SP (128.2 +/- 15.3) gm x m/sec, max LV dP/dt (352 +/- 62) mm Hg/sec, and peak aortic flow (3.3 +/- 0.4) l/min (p < 0.05). The percentage increases were significantly larger in the vascular delay group compared with controls at 50 Hz-10 volts LDM stimulation. By using a two-stage vascular delay procedure, LDM stimulation can provide meaningful cardiac assistance during training periods. Furthermore, brief periods of maximal potential benefit (demand cardiomyoplasty) can be achieved during the training period.

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.

Vascular delay and intermittent stimulation: keys to successful latissimus dorsi muscle stimulation

BACKGROUND

The goal of this study was to obtain physiologically significant increases in peak left ventricular (LV) systolic pressure and stroke volume with latissimus dorsi muscle (LDM) stimulation in cardiomyoplasty (CMP). We hypothesized that preserving LDM integrity by vascular delay and intermittent stimulation would significantly increase LDM cardiac assistance.

METHODS

In 4 control dogs and 12 dogs that had undergone a vascular delay (VD) procedure, LV dysfunction was induced by intracoronary microsphere injections. Cardiomyoplasty surgery was performed 14 days later, followed by progressive LDM conditioning. In the control dogs and in 6 of the VD dogs, the LDM was stimulated 24 hours per day (VD plus constant stimulation [CS]). In the other 6 VD dogs, LDMs were stimulated on a daily schedule of 10 hours on and 14 hours off (VD plus interrupted stimulation [IS]). Latissimus dorsi muscle stimulated beats were compared with nonstimulated beats 9 weeks later.

RESULTS

In the control dogs, LDM stimulation had minimal effects. In VD + CS and VD + IS, LDM stimulation increased peak LV pressure, stroke volume, stroke work, and stroke power (p < 0.05). However, these changes were greater in the VD + IS group, in which LDM stimulation increased peak aortic pressure by 17.6 +/- 1.7 mm Hg, peak LV pressure by 19.7 +/- 1.1 mm Hg, peak positive LV dp/dt by 398 +/- 144 mm Hg per second, stroke volume by 5.1 +/- 0.7 mL, stroke work by 10.9 +/- 0.9 gm.m, and stroke power by 122.7 +/- 11.6 gm.m per second (p < 0.05 compared with VD + CS). Quantitative morphometric analysis showed minimal LDM degeneration in the VD + IS group (7.5% +/- 1.1%), and VD + CS group (10.5% +/- 4.5%) compared with the control group (29.5% +/- 4.5%, p < 0.05).

CONCLUSIONS

VD and IS considerably increased the LV assistance with LDM stimulation. Further studies of this combined approach to CMP should be planned.

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.

Surgical options for the treatment of heart failure

This article will examine the role of specific surgical interventions for congestive heart failure (CHF). The most definitive surgical option for severe end-stage heart failure is cardiac transplantation. In general, patients considered for heart transplant should have severe heart disease despite all other therapies with a high risk of death within 1 year. Noncardiac conditions that would by themselves shorten life expectancy or increase the risks of rejection, infection, or other fatal complication, should not be present. However, in light of the limited donor pool, complications associated with long-term immunosuppressive therapy, and the ever-increasing number of CHF patients, the role of cardiac transplantation for CHF will continue to be limited. The conduct of and evaluation for cardiac transplantation has been well described previously and therefore will not be evaluated in this review (1); however, there has been recent progress in the genetic modification of animal organs for potential use in transplantation (xenografts) (2). If these developments come to fruition, then cardiac transplantation/organ replacement may become a surgical option for a much greater number of CHF patients. One alternative approach to complete cardiac transplantation is the surgical placement of transformed cells into the diseased myocardium, briefly discussed under "Future Directions." This article will examine surgical options that are currently being used for CHF patients, surgical modalities that are currently under clinical evaluation, and finally, potential future therapies with respect to surgical options for heart failure.

Low-frequency stimulation of fast muscle affects the abundance of Ca(2+)-ATPase but not its oligomeric status

After chronic, low-frequency stimulation, a rapid decline in Ca(2+) pump activity is observed during the early stages of skeletal muscle transformation. However, this variation in enzymatic activity does not coincide with a drastic reduction in the amount of sarcoplasmic reticulum Ca(2+)-ATPases. To investigate whether changes in subunit interactions within Ca(2+) pump complexes contribute to this phenomena, we performed a chemical cross-linking analysis of 4 days continuously, and 4 days discontinuously, electrostimulated fast muscle fibers. The abundance of the slow and fast Ca(2+)-ATPase isoforms sarco(endo)plasmic reticulum Ca(2+)- ATPase types 1 and 2 was affected during the fast-to-slow transition process, demonstrating that, even after short-term stimulation, distinct changes in the isoform expression pattern of muscle proteins occur. However, the oligomeric status of both ion pump species did not change. Hence, chemical modifications of critical enzyme domains must be responsible for the rapid stimulation-induced activity changes, not variations in protein-protein interactions within Ca(2+)-ATPase units. Oligomerization appears to be of central importance to the proper physiological functioning of the Ca(2+)-ATPase and does not undergo changes during skeletal muscle conditioning.

Preparation of a skeletal muscle ventricle in sheep: severe damage to the Latissimus dorsi muscle due to mobilization before preconditioning

As part of a study examining the use of a skeletal muscle ventricle for cardiac assistance in sheep, a new concept of muscle preconditioning was put into practice. We aimed to produce a latissimus dorsi muscle (LDM) capable of performing chronic work immediately after the construction of a skeletal muscle ventricle. The left LDM was detached from the thoracic wall, divided longitudinally and reattached in situ to achieve vascular delay. The right LDM was left unaffected. Thereafter, preconditioning of both LDM was started according to the clinically approved stimulation protocol for cardiomyoplasty. Preconditioning of the unaffected right LDM in situ resulted in a complete muscle fiber transformation with no signs of degeneration or necrosis. Mobilization of the left LDM before preconditioning led to a distinct damage of the muscle. During conditioning, the increase in burst duration from 2 to 3 impulses in sheep A and from 3 to 5 impulses in sheep B resulted in a homogenous degeneration of the muscle fibers of the left LDM. Histomorphological analysis showed a dramatic increase in the percent perimysial and endomysial connective tissue. The applied concept of muscle prefabrication proved to be a failure. Muscle splitting and mobilization followed by vascular delay and in situ conditioning as a concept of muscle prefabrication should be strictly avoided.

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.

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.

Nontransplant cardiac surgery for end-stage cardiomyopathy

OBJECTIVE

To treat end-stage cardiomyopathy, we evaluated endoventricular circular patch plasty, partial left ventriculectomy, and valvular reconstruction alone in our 2-year experience.

METHODS

Among 86 patients with heart failure evaluated between December 1996 and February 1999, 33 patients with ischemic cardiomyopathy (25 men and 8 women; mean age 61 +/- 7.8 years; New York Heart Association class 3.5 +/- 0.5) were treated with endoventricular circular patch plasty combined with coronary bypass grafting (84%) and mitral reconstruction (36%). The other 53 patients with nonischemic cardiomyopathy (45 men and 8 women; mean age 48 +/- 14.3 years, New York Heart Association class 3.7 +/- 0.5), were treated by left ventricular reduction by partial left ventriculectomy (n = 37) or patch plasty (n = 3) and valve reconstruction alone (n = 13). The first 24 patients (group I) underwent ventriculectomy with or without valve reconstruction; the more recent 29 patients (group II) underwent left ventricular reduction (n = 16) or valve reconstruction alone (n = 13) on the basis of the intraoperative echocardiographic evaluation to observe changes of wall motion and thickness during cardiopulmonary bypass.

RESULTS

Ischemic Group: Hospital mortality in elective (n = 26) and emergency (n = 7) operations was 4% and 43%, and 3 patients died in the late postoperative period. Mean New York Heart Association class and ejection fraction improved from 3.5 +/- 0.5 to 1.5 +/- 0.7 and from 23% +/- 7.7% to 36% +/- 8.6%, respectively. Left ventricular end-diastolic and end-systolic volume indexes decreased from 162 +/- 46 mL/m(2) to 110 +/- 39 mL/m(2) and from 130 +/- 47 mL/m(2) to 70 +/- 32 mL/m(2), respectively. Nonischemic Group: In 40 patients with left ventricular reduction, hospital mortality in elective (n = 33) and emergency (n = 7) operations was 6% and 86%, and 5 patients died in the late postoperative period. Mean New York Heart Association class and ejection fraction improved from 3.7 +/- 0.5 to 1.7 +/- 0.6 and from 18% +/- 6.4% to 31% +/- 5.9%. Left ventricular end-diastolic and end-systolic volume indexes decreased from 203 +/- 45 mL/m(2) to 110 +/- 37 mL/m(2) and from 164 +/- 40 mL/m(2) to 79 +/- 33 mL/m(2), respectively. In 13 patients undergoing valve reconstruction alone (12 mitral with or without tricuspid and 1 tricuspid plus left ventricular assist device), hospital mortality in elective (n = 9) and emergency (n = 4) operations was 0% and 50% with no late deaths. Mean New York Heart Association class and ejection fraction improved from 3.6 +/- 0.5 to 2.0 +/- 0.5 and from 22% +/- 6.0% to 30% +/- 14.5%, respectively. Mean left ventricular end-diastolic and end-systolic volume indexes decreased from 170 +/- 34 mL/m(2) to 150 +/- 50 mL/m(2) and from 140 +/- 38 mL/m(2) to 104 +/- 40 mL/m(2), respectively. Overall mortality decreased from 50% in group I to 10% in group II. The survival estimates at 2 years were 77% (confidence limits 57%-88%) in the ischemic group and 63% (confidence limits 47%-75%) in the nonischemic group (no significant difference). The analysis of our data showed that the factors influencing the surgical results for dilated cardiomyopathy were presence of severe mitral regurgitation, preoperative New York Heart Association functional class IV with emergency operation, and operative procedures with randomly performed partial left ventriculectomy without an intraoperative echo test.

CONCLUSION

Endoventricular circular patch plasty, partial left ventriculectomy, and solo valve reconstruction can be performed with an acceptably low risk as elective operations. The selection of operative procedures in idiopathic dilated cardiomyopathy and avoidance of emergency surgery improved operative mortality and morbidity. Among patients who survived at least 1 year, there were no late deaths up to 30 months' follow-up.

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.

Multistep approach to electrical stimulation after cardiomyoplasty

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.

Congenital Heart Surgery Nomenclature and Database Project: pediatric cardiomyopathies and end-stage congenital heart disease

The extant nomenclature for cardiomyopathy is reviewed for the purpose of establishing a unified reporting system. The subject was debated and reviewed by members of the STS-Congenital Heart Surgery Database Committee and representatives from the European Association for Cardiothoracic Surgery. All efforts were made to include all relevant nomenclature categories using synonyms where appropriate. A functional classification based on pathophysiology is proposed. Cardiomyopathy is subdivided into: dilated cardiomyopathy, hypertrophic cardiomyopathy, restrictive cardiomyopathy, right ventricular cardiomyopathy, and end-stage congenital heart disease. A comprehensive database set is presented that is based on a hierarchical scheme. Data are entered at various levels of complexity and detail that can be determined by the clinician. These data can lay the foundation for comprehensive risk stratification analyses. A minimum database set is also presented that will allow for data sharing and would lend itself to basic interpretation of trends. Outcome tables relating diagnoses, procedures, and various risk factors are presented.

Surgical approaches to dilated cardiomyopathy

Heart failure is one of the leading causes of hospitalization in the United States today. Congestive heart failure is a chronic progressive disease with the common central element being the remodeling of the cardiac chamber associated with ventricular dilation. Secondary mitral regurgitation is a complication of end-stage cardiomyopathy and is associated with a poor prognosis. Historically, these patients were not considered operative candidates due to the high morbidity and mortality in this patient population. Heart transplantation is now considered the standard of treatment for select patients with end-stage heart disease, however, it is only applicable to a small number of patients. In an effort to address this problem, newer and alternative surgical approaches are evolving, including mitral valve annuloplasty, the Batista myoplasty, and cardiomyoplasty. When these operative techniques that alter the shape of the left ventricle are utilized, in combination with optimal medical management for heart failure, survival is improved and patients can avoid or postpone transplantation.

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.

Composite cardiac binding in experimental heart failure

BACKGROUND

Composite cardiac binding consists of wrapping the heart with a synthetic membrane and a pericardial interposition. The goal of the present study was to apply composite cardiac binding to a canine model of heart failure.

METHODS

Twenty dogs were randomized to 2 groups: untreated heart failure (group 1, n = 13) and heart failure pretreated by composite cardiac binding (group 2, n = 7). They received a total dose of 1 mg x kg(-1) of intracoronary doxorubicin over 4 weeks. Hemodynamic data were obtained at weeks 0, 7, and 12. All animals were followed up with weekly echocardiography for 12 weeks.

RESULTS

Survival in group 1 was 54% and in group 2 was 100% at week 12 (p = 0.0438). Left ventricular end-diastolic pressure increased by 153% in group 1 and by 59% in group 2 (p = 0.0395) at week 12. Ejection fraction decreased by 27% in group 1 and by 19% in group 2 (p = 0.4401) at week 12.

CONCLUSIONS

Composite cardiac binding significantly prolongs survival and attenuates left ventricular dilatation and the increase in left ventricular end-diastolic pressure associated to chronic heart failure. Further evaluation in established heart failure is needed. Composite cardiac binding may be used for the prevention of recurrent dilatation following reduction ventriculoplasty.

Dynamic cardiomyoplasty: at the crossroads

BACKGROUND

Dynamic cardiomyoplasty remains a promising, but still unproven surgical treatment for patients with end-stage heart failure. Lack of a clear survival advantage and ongoing misunderstanding of its mechanism of action have hindered its acceptance as a treatment alternative for patients with end-stage heart failure. This review seeks to update current clinical results and practice of dynamic cardiomyoplasty and to present its likely mechanism of action.

METHODS

The method involved a literature review.

RESULTS

More than 600 patients have undergone dynamic cardioplasty since 1985. Improvement in average New York Heart Association class was noted in 80% to 85% of hospital survivors. Operative mortality has decreased from 31% in Phase I to less than 3% in the ongoing Phase III trial. Clinical work as well as recent animal work supports the hypothesis that through a combination of long-term elastic constraint and active dynamic assist, dynamic cardiomyoplasty decreases myocardial wall stress associated with the remodeling process of progressive heart failure.

CONCLUSIONS

Though dynamic cardiomyoplasty can be shown to limit the remodeling process of heart failure in animal studies and some patients, its ultimate role in the treatment of heart failure will depend on the outcome of randomized, controlled studies.

Vascular delay of the latissimus dorsi provides an early hemodynamic benefit in dynamic cardiomyoplasty

OBJECTIVES

Dynamic cardiomyoplasty (CMP) as a surgical treatment for chronic heart failure improves functional class status for most patients. However, significant hemodynamic improvement with latissimus dorsi muscle (LDM) stimulation has not been consistent. The current protocols do not allow early LDM stimulation after CMP surgery. We hypothesized that vascular delay of LDM would increase myocardial assistance after CMP and allow early (48-h) LDM stimulation after CMP.

METHODS

Mongrel dogs (n = 24) were divided in four groups: 1) controls (n = 6), single-stage CMP; 2) Group ES (n = 6), single-stage CMP with early LDM stimulation beginning 48 h, postoperatively; 3) Group VD (n = 6), vascular delay of the LDM followed by CMP without early LDM stimulation, and 4) Group VDES (n = 6), vascular delay of LDM (14-18 days), followed by CMP with early stimulation (48 h postoperatively). Two weeks after CMP, global cardiac dysfunction was induced by injecting microspheres into the left coronary artery. LDM-assisted (S) beats were compared with nonstimulated beats (NS) by measuring aortic pressure (AoP), LV pressure, aortic flow, and by calculating first derivative of LV contraction (+/-dP/dt), stroke volume (SV), and stroke work (SW).

RESULTS

In ES, LDM stimulation had no effect on the hemodynamic parameters. In the other groups, LDM stimulation significantly (p < 0.05) increased AoP, LVP, dP/dt, SV, and SW. However, these increases were much larger in VD and VDES. In VD, LDM stimulation increased peak AoP by 21.5+/-3.8 mm Hg, LVP by 22.1+/-4.1 mm Hg, dP/dt by 512+/-163 mm Hg/sec, SV by 10.4+/-2.3 mL, and SW by 22.1+/-5.4 g/m(-1). Similarly, in VDES, LDM stimulation increased peak AoP by 24.1+/-4.7 mm Hg, LVP by 26.2+/-4.3 mm Hg, dP/dt by 619+/-47 mm Hg/sec, SV by 6.5+/-0.7 mL, and SW by 16.7+/-4.1 g/m(-1).

CONCLUSIONS

In dogs with global LV dysfunction, CMP after vascular delay resulted in a significant improvement in hemodynamic function measured 2 weeks after surgery. This improvement was not provided by single-stage CMP with or without early stimulation. Vascular delay of the LDM before surgery may play an important role for early benefit after CMP, shorten the overall muscle training period, as well as increase hemodynamic response to LDM stimulation.

A new method of double cardiomyoplasty: "contractile muscular sling"

BACKGROUND

In several experimental studies, double cardiomyoplasty using both latissimus dorsi muscles did not provide sufficient assist to the failing heart and did not clearly show improvement compared with single cardiomyoplasty. This study demonstrated the superior efficacy of our method of double cardiomyoplasty compared with single cardiomyoplasty.

METHODS

In 16 dogs, the two latissimus dorsi muscles were crossed in front of the heart and directly sutured to each other behind the heart. Control hemodynamic measurements were obtained, and acute heart failure was induced by intravenous administration of propranolol. After the hemodynamic changes with bilateral latissimus dorsi muscle assistance were measured, single cardiomyoplasty was done in the same dog, and the hemodynamic variables were measured.

RESULTS

With our double cardiomyoplasty, aortic systolic pressure increased by 25% (p < 0.001); pulmonary artery systolic pressure, by 40% (p < 0.001); end-systolic elastance, by 155% (p < 0.001); and cardiac output, by 55% (p < 0.001). There were significant increases in aortic pressure, pulmonary artery pressure, end-systolic elastance, stroke volume, and cardiac output with our double cardiomyoplasty compared with single cardiomyoplasty.

CONCLUSIONS

In this study, our double cardiomyoplasty provided significant hemodynamic improvement compared with single cardiomyoplasty.

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.

Mortality remains high for outpatient transplant candidates with prolonged (>6 months) waiting list time

OBJECTIVES

The study aimed to determine the risk of death or urgent transplant for patients who survived an initial 6 months on the outpatient heart transplant waiting list when criteria emphasizing reduced peak oxygen consumption are used for transplant candidate selection.

BACKGROUND

Waiting time is a key criterion for heart donor allocation. A recent single-center investigation described decreasing survival benefit from transplant for patients who survived an initial 6 months on the outpatient waiting list.

METHODS

Kaplan-Meier survival analyses were performed for 80 patients from the Hospital of the University of Pennsylvania (HUP) listed from July 1986 to January 1991, and 132 patients from Columbia-Presbyterian Medical Center (CPMC) listed from September 1993 to September 1995. Survival from the time of outpatient listing for the entire group (ALL) was compared to subsequent survival from 6 months onward for those patients who survived the initial 6 months after placement on the outpatient list (6M). Both urgent transplant and left ventricular assist device implantation were considered equivalent to death; elective transplant was censored. RESULTS Survival for 6M was not significantly better than ALL at HUP (subsequent 12 months: 60+/-7 vs. 60+/-6% [mean+/-SD]; p = 0.89) nor at CPMC (subsequent 12 months: 60+/-6 vs. 48+/-5%; p = 0.35). Survival for 6M at both centers was substantially lower than survival following transplant from the outpatient list in the United States in 1995.

CONCLUSIONS

When high-risk patients are selected for nonurgent transplant listing, mortality remains high, even among those who survive the initial six months after listing. Time accrued on the waiting list remains an appropriate criterion for donor allocation.

Evaluation of a compressive-type skeletal muscle pump for cardiac assistance

BACKGROUND

Recent investigations have focused on using the latissimus dorsi muscle for cardiac assistance. Although cardiomyoplasty has been applied clinically, other procedures remain experimental, but promising, modes of cardiac assistance. We assessed the latissimus dorsi muscle as an in situ energy source for circulatory assist devices.

METHODS

We developed a pneumatic chamber as a compressive-type muscle actuator. The chamber was implanted under the latissimus dorsi muscle and converted contractile power into pneumatic pressure. The effect of chamber position and size and the influence on muscle blood flow were examined. After muscle conditioning, the pump performance of a circulatory assist device driven by the chamber was evaluated.

RESULTS

The chamber functioned better when placed in the proximal position of the latissimus dorsi muscle. The size affected the generated pneumatic pressure, and the higher resting pressure of the chamber reduced the muscle blood flow. The maximum stroke work of the circulatory assist device was greater than that of the right ventricle but less than that of the left ventricle. The chamber could drive the circulatory assist device against the systemic range of afterload in which a high preload was available. Long-term adhesion surrounding the chamber reduced the pressure generation capability.

CONCLUSIONS

The compressive-type muscle actuator using the latissimus dorsi muscle generated acceptable hemodynamic work for right ventricular bypass or aortic counterpulsation.

Surgical therapy for dilated cardiomyopathy

As the next millennium approaches, excitement and promise characterize the future of dilated cardiomyopathy. Until recently, dilated cardiomyopathy was considered an incurable, uniformly fatal chronic disease. Epidemiologic studies have demonstrated that at least a quarter of patients with recent onset of symptoms with cardiomyopathy manifest spontaneous improvement and a sustained favorable prognosis. It is imperative that patients who present with new-onset cardiomyopathy be managed medically and closely followed. Medical treatment remains the foundation of therapy, and certainly the advent of beta-blocker use may herald further benefit beyond that observed with conventional therapy (ACE inhibitors and digoxin). Unless mechanical support is required for hemodynamic instability and end organ failure, patients should be treated medically and observed. As discussed earlier, transient mechanical support as a bridge to recovery should be considered in the appropriate clinical scenario before committing to cardiac transplantation. Patients with established disease who have been followed for extended periods (> 6 months) that have progressive symptoms despite optimal medical therapy should be considered for surgical therapies. Cardiac transplantation is available to only a minority of the diseased population. All newer modalities of surgical unloading therapy theoretically reduce wall stress. Clearly in dilated cardiomyopathy, ventricular performance is reduced; however, individual myocyte contractile function may be intact. Studies of isolated myocytes (which are unloaded) have yielded conflicting data; however, if contractile function is intact and performance is reduced primarily secondary to abnormal loading conditions, surgical unloading therapies should yield benefit. Hence the thesis of Batista that geometric alteration will improve performance assumes intrinsic integrity of the myocyte contractile function. The implication of intrinsic myocyte contractile dysfunction is that surgical remodeling does not yield improved ventricular performance. Although clinicians have learned that selection criteria appear to play a role in predicting beneficial outcomes with cardiomyoplasty and the Batista procedure, clinical techniques to assess the integrity of myocyte function are unsophisticated. Quantifying interstitial fibrosis, assays for the degree of apoptosis, and various immunologic measures currently do not provide the insight necessary to predict outcomes reliably. The future assessment of dilated cardiomyopathy and the decision to consider alternative surgical procedures versus cardiac transplantation will likely be determined by biomolecular studies. At present, these new surgical procedures are promising therapies and potential alternatives to cardiac transplantation. Controlled studies to determine the clinical and survival benefit compared with medical therapy will ultimately be required, after the surgical techniques and patient selection criteria are refined. Randomized, prospective controlled studies assessing LVAD therapy and cardiomyoplasty are in progress.

Preconditioning of the latissimus dorsi muscle in cardiomyoplasty: vascular delay or chronic electrical stimulation

OBJECTIVES

In standard single stage cardiomyoplasty (CMP), the latissimus dorsi muscle (LDM) is not preconditioned prior to surgery. We hypothesized that latissimus dorsi preconditioning by vascular delay or by chronic electrical stimulation would result in an improved LV hemodynamic function early (14 days) after CMP.

METHODS

Mongrel dogs had preconditioning of the latissimus dorsi by a vascular delay procedure followed by CMP 14-18 days later (group I VD). Dogs in group II underwent 4 weeks of chronic stimulation (CS) of the latissimus dorsi (2 V/30 Hz, six bursts/min) followed by CMP. The latissimus dorsi muscle was fully stimulated from 48 h after cardiomyoplasty in both groups (2 V/30 Hz, three bursts/min). Two weeks after myoplasty, injecting 2.0-3.0 x 10(5) 90 microm latex microspheres in the left main coronary artery induced global cardiac dysfunction. Hemodynamic function was then evaluated for latissimus dorsi muscle assisted (S) beats and non-stimulated beats (NS) in each group by measuring peak systolic aortic pressure (AOP), left ventricular pressure (LVP) and end diastolic pressure (LVEDP), and by calculating maximum and minimum dP/dt.

RESULTS

Dogs with vascular delay of the latissimus dorsi showed a marked increase for all hemodynamic indices (AOP: 23.9+/-2.5%, LVP: 23.5+/-2.2%, max dP/dt: 49.4+/-3.3%) for LDM assisted (S) beats compared to non-stimulated beats (P < 0.001). Animals with chronic electrical training did not demonstrate a significant increase in any hemodynamic parameter with LDM stimulation.

CONCLUSION

Preconditioning the LDM may play an important role in providing early cardiac assistance in CMP. Preconditioning the LDM with vascular delay resulted in improving performance of the LDM with consistent increases in LV hemodynamics. This was not observed after preconditioning with chronic electrical stimulation. Vascular delay of the latissimus dorsi can significantly improve muscle performance in CMP and could provide hemodynamic assistance early after surgery.

Surgical alternatives in the treatment of heart failure

Heart failure continues to plague a large population worldwide, and its incidence is increasing annually as a result of an aging population. It is associated with lengthy hospital stays, multiple hospital readmissions, and decreased quality of life because of its clinical manifestations. Although cardiac transplantation has become the therapy of choice for patients with heart failure, scarcity of donor hearts and age limitations prohibit its widespread use. Despite major advances in medical management, researchers continue to explore alternative surgical therapies to help augment cardiac function. This article explores surgical interventions in the management of heart failure, many of which are still experimental or in clinical trials. Coronary artery bypass surgery, dynamic cardiomyoplasty, and partial left ventriculectomy for the management of heart failure are discussed in detail. Descriptions of each surgical procedure, special care needs, and clinical outcomes are presented. However, because readers are familiar with the coronary artery bypass procedure and postoperative patient care, the discussion will focus on issues related to coronary artery bypass grafting in the presence of ischemic cardiomyopathy.

Cardiomyoplasty and implantable cardioverter defibrillator: efficacy and safety of concomitant device implantation: sudden death and cardiomyoplasty

Sudden death represents a common event in the natural history of patients affected by chronic heart failure. Such an outcome also has been shown to characterize the follow-up of the cardiomyoplasty procedure. We report two cases of patients who had cardiomyoplasty and experienced witnessed episodes of ventricular arrhythmia at variable times after surgery (2 years and 2 months, respectively). In the first case, an implantable cardioverter defibrillator (ICD) was implanted subsequent to the arrhythmic episode, whereas the second patient had a combined cardiomyoplasty and ICD implantation procedure. In particular, this patient underwent a modified wrapping technique, herein described, because of a large left ventricular dilatation. In both cases, ventricular defibrillation did not affect the correct functioning of the implanted cardiomyostimulator. Our article confirms that ventricular arrhythmia is common in cardiomyoplasty patients. The combined use of a skeletal muscle stimulator and implantable defibrillator may therefore be effective in preventing arrhythmia-related sudden death without any concurrent effect on the correct functioning of the wrapped muscle/heart circuit, with likely benefit on long-term cardiomyoplasty patient survival.

Variable effects of cardiomyoplasty on left ventricular function

Cardiomyoplasty (CMP) has been considered as a possible treatment for patients with heart failure. Symptomatic improvements occur almost uniformly among survivors with CMP, but changes in left peak ventricular systolic pressure (PVSP) and stroke volume vary in patients. This study examined whether there is variability present shortly after cardiomyoplasty surgery. Cardiomyoplasty was performed in 11 mongrel dogs with normal ventricular function. Nine to twelve days after CMP, left ventricular (LV) function was evaluated by simultaneously measuring LV volume (conductance catheter) and pressure (Millar catheter). The latissimus dorsi muscle (LDM) was stimulated synchronously with ventricular systole in a ratio of 1:4 to 1:7 to avoid muscle fatigue. Data were analyzed on a beat by beat basis. The PVSP, and maximum dP/dt (+dP/dt) increased, but the absolute value of minimum dP/dt (-dP/dt) decreased in stimulated beats in 7 dogs while 4 dogs did not respond. The net changes in stimulated beats versus nonstimulated beats of PVSP were 6.1 +/- 1.8 mm Hg (4.3%), of stroke work was 4.5 +/- 1.9 gm x m (29.5%), of +dP/dt was 185 +/- 47 mm Hg/s (8%), and of -dP/dt was 168 +/- 43 mm Hg/s (7.8%) (p < 0.05) for all these net changes in the responding group while these variations were not significant in the nonresponding group. From the results of our study, active LDM assist improves left ventricular systolic function, occurring in only 7 of 11 experiments. This improvement is inconsistent and varied individually. The integrity of the LDM, tightness of wrapping, and adhesions might contribute to the variability which is present early after surgery and before the LDM is converted into a fatigue resistance muscle.

Regional perfusion and oxygenation in the pedicled latissimus dorsi muscle flap: the effect of mobilisation and electrical stimulation

BACKGROUND

The pedicled latissimus dorsi muscle flap is dependent upon an adequate blood supply via a single nutrient artery arising at its most proximal point. It has been suggested that when the latissimus dorsi muscle is used for cardiomyoplasty there is a risk of ischaemic damage to the distal regions of the flap under the additional metabolic stress of repeated electrical stimulation.

METHODS

A rabbit model was developed in which the latissimus dorsi muscle was raised as a pedicled flap (n = 10). Needle microelectrodes were used to measure oxygenation and perfusion simultaneously in different regions of the muscle. Perfusion was measured using a gas tracer technique in which nitrous oxide was used as the marker. Muscle performance was measured by electrical stimulation of the mobilised flap.

RESULTS

The mean (standard error) perfusion of the distal muscle fell significantly from 19.5 (6.2) to 11.9 (3.8) ml.min-1 100 g-1 (P < 0.05) as a consequence of mobilisation, although tissue oxygenation was maintained. Perfusion and pO2 of the proximal regions of the flap were unchanged. During electrical stimulation perfusion increased by 72 (12)% from resting levels in the proximal region, but by only 39 (8)% in the distal muscle. Tissue pO2 decreased during stimulation by 5.7 (1.8) mmHg proximally compared to 11.7 (3.7) mmHg distally P < 0.05). During recovery the pO2 remained below baseline for 24 minutes in the proximal muscle compared to 32 minutes in the distal muscle.

CONCLUSIONS

Mobilisation results in a reduction in the perfusion of distal areas of the latissimus dorsi muscle flap. During repeated contraction the perfusion remains reduced and is unable to maintain tissue oxygen requirements. This has implications for dynamic applications of the latissimus dorsi muscle flap and supports the suggestion that ischaemia is the cause of distal muscle atrophy and fibrosis in cardiomyoplasty. Combined perfusion and pO2 data provide a new insight into muscle viability studies.