Right internal thoracic artery through the transverse sinus in myocardial revascularization

Background. A major concern in evaluating dynamic cardiomyoplasty has been whether the synchronous stimulation of latissimus dorsi muscle is essential for benefit or not. We studied 10 patients to determine the efficacy of the systolic augmentation generated by the synchronous electrical stimulation of the latissimus dorsi muscle.

Methods. Left ventricular ejection fraction, end-systolic and end-diastolic volume indexes, and stroke volume index obtained during resting, peak exercise, and recovery periods (“on” values) were compared with those obtained 1 week after cessation of electrical stimulus (“off” values). Double product and estimated total body oxygen consumption at peak exercise were also calculated and compared.

Results. Higher ejection fractions (0.36 ± 0.07 versus 0.33 ± 0.06 at rest, 0.40 ± 0.07 versus 0.33 ± 0.07 peak exercise, and 0.37 ± 0.06 versus 0.31 ± 0.06 at recovery) and lower end-systolic volume indexes with relatively constant end-diastolic volume indexes were observed with the cardiomyostimulator on. Further, exercise response was better with the cardiomyostimulator on. Double product indirectly reflected better myocardial oxygen supply/demand ratio when on at peak exercise (17 ± 2.2 mm Hg × beats/min × 10⁻³ for on versus 19 ± 2.6 mm Hg × beats/min × 10⁻³ for off). Estimated total body oxygen consumption was improved at peak exercise when the cardiomyostimulator was functional (12 ± 2.7 mL · kg⁻¹ · min⁻¹ versus 11 ± 2.6 mL · kg⁻¹ · min⁻¹).

Conclusions. Current data suggest a true systolic assist during synchronous contractions of the latissimus dorsi muscle. It is thought, therefore, that synchronous electrical stimulation is essential for maximum benefit and all the beneficial effect of cardiomyoplasty certainly cannot be attributed to simple wrapping itself.     

Diagnostic approach and treatment strategy in tachycardia-induced cardiomyopathy

BACKGROUND: Due to the absence of differential guidelines for heart failure with tachyarrhythmia, it is difficult to diagnose tachycardia-induced cardiomyopathy (TIC) at the initial visit. Furthermore, clinical outcomes of rate versus rhythm control in TIC are unclear. HYPOTHESIS: Because the etiology of TIC is different from dynamic cardiomyoplasty (DCMP), differential parameters may be present. METHODS: We assessed 21 patients with TIC (15 men; mean age, 50+/-14 years) and 21 control patients with idiopathic DCMP. We assessed clinical courses, echocardiographic parameters, as well as outcomes by treatment. RESULTS: In the TIC group, the related tachyarrhythmias were atrial fibrillation (n=12), atrial flutter (n=5), atrial tachycardia (n=3) and paroxysmal supraventricular tachycardia (n=1). After treatment, all patients became asymptomatic and the ejection fraction (EF) improvement (DeltaEF>or=15%) was observed in all patients (left ventricular ejection fraction [LVEF], 30+/-11%initial versus 58+/-6%last). In the idiopathic DCMP group, no patient showed EF improvement (EF increase相似文献   

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.     

Feasibility of pacemaker therapy after dynamic cardiomyoplasty

A 54-year-old man presented with total atrioventricular (AV) block 3 months after dynamic cardiomyoplasty was performed because of heart failure due to idiopathic dilated cardiomyopathy. Though the cardiomyostimulator acted as a back-up pacemaker, a DDDR pacemaker was implanted to optimize hemodynamics. During testing no cross-sensing or cross-stimulation between the pacemaker and the cardiomyostimulator was demonstrable. The synchronization delay, however, had to be adjusted.     

Influence of Different Conditioning Methods on Force and Fatigue Resistance in Chronically Stimulated Skeletal Muscles

A study was undertaken to compare different conditioning methods for the transformation of latissimus dorsi muscle into a fatigue resistant one for application in circulatory assist. In ten sheep four electrodes were sutured to the epineurium of the left thoracodorsal nerve for indirect electrical stimulation of the latissimus dorsi muscle. In six sheep a "carousel stimulation, " a special multichannel stimulation, in combination with a recently developed conditioning protocol was used for muscle conditioning ( multichannel method ). In four sheep, a conventional stimulation protocol using single channel stimulation was applied for transformation of the muscle (single channel method). The final experiments were carried out when fatigue resistance was obtained. The maximum tetanic forces at different preloads were determined and fatigue resistance was tested during 20 minutes of continuous stimulation. Both conditioning patterns led to fatigue-free chronic stimulation. Muscles conditioned by multichannel stimulation exhibited between 20% and 33% less force than the contralateral unconditioned muscles, whereas in the single channel group this loss was between 32% and 43%. Thus, the multichannel method revealed relatively superior in preserving muscle force for chronic stimulation.     

Multimodality noninvasive imaging for assessing therapeutic effects of exogenously transplanted cell aggregates capable of angiogenesis on acute myocardial infarction

Although the induction of neovascularization by cell-based approaches has demonstrated substantial potential in treating myocardial infarction (MI), the process of cell-mediated angiogenesis and its correlation with therapeutic mechanisms of cardiac repair remain elusive. In this work, three-dimensional (3D) aggregates of human umbilical vein endothelial cells (HUVECs) and cord-blood mesenchymal stem cells (cbMSCs) are constructed using a methylcellulose hydrogel system. By maximizing cell–cell and cell–ECM communications and establishing a hypoxic microenvironment in their inner cores, these cell aggregates are capable of forming widespread tubular networks together with the angiogenic marker α_vβ₃ integrin; they secret multiple pro-angiogenic, pro-survival, and mobilizing factors when grown on Matrigel. The aggregates of HUVECs/cbMSCs are exogenously engrafted into the peri-infarct zones of rats with MI via direct local injection. Multimodality noninvasive imaging techniques, including positron emission tomography, single photon emission computed tomography, and echocardiography, are employed to monitor serially the beneficial effects of cell therapy on angiogenesis, blood perfusion, and global/regional ventricular function, respectively. The myocardial perfusion is correlated with ventricular contractility, demonstrating that the recovery of blood perfusion helps to restore regional cardiac function, leading to the improvement in global ventricular performance. These experimental data reveal the efficacy of the exogenous transplantation of 3D cell aggregates after MI and elucidate the mechanism of cell-mediated therapeutic angiogenesis for cardiac repair.     

细胞性心肌成形术研究进展

许多基本的心血管疾病发展到晚期会演变为充血性心力衰竭 ,尽管治疗手段已有了明显进步 ,但充血性心力衰竭仍然是一个主要并且将继续为人类关注的健康问题。充血性心力衰竭可使具有完整舒缩功能的心肌细胞数量减少 ,心肌结构完整性遭到破坏。心脏移植治疗终末期心力衰竭是金标准 ,但供体的不足限制了其临床广泛应用 ,就需要其它新方法来替代以挽救丧失的心肌细胞。细胞性心肌成形术被证明是一种行之有效的替代治疗方法。细胞性心肌成形术就是将包括自体心肌细胞在内的不同类型的细胞移植到宿主心肌组织中加固其结构和改善其功能。最近研究发现胚胎干细胞和成体干细胞均可以向心肌细胞方向分化。自体骨骼肌成肌细胞、内皮祖细胞等其它类型细胞同样成功地在宿主受损心肌组织中存活并增殖分化 ,改善宿主心脏功能。这里对目前细胞性心肌成形术的移植细胞类型作一综述。     

骨骼肌心脏辅助的发展与现状

应用骨骼肌辅助心脏功能的研究已40年。本文综述了该领域的发展历程,基本原理,以及各种不同形式的骨骼肌辅助心脏(包括动力性心肌成形术,骨骼肌心室,骨骼肌驱动的反搏装置,动力性主动脉成形术等)的研究和临床应用状况,为慢性难治性心衰的治疗提供一个新的有效的途径。     

Experimental evaluation of the hemodynamic efficiency of dynamic cardiomyoplasty in the surgical treatment of severe left ventricular failure

A. N. Bakulev Institute of Cardiovascular Surgery, Academy of Medical Sciences of the USSR, Moscow. (Presented by Academician of the Academy of Medical Sciences of the USSR V. I. Burakovskii.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 112, No. 12, pp. 584–588, December, 1991.     

The dose-related response of rabbit fast muscle to long-term low-frequency stimulation

Rabbit tibialis anterior muscles were stimulated continuously at 2.5 Hz, 5 Hz, or 10 Hz for 10 months. The resulting adaptive transformation was dose-related for contractile speed, myosin isoform composition, and enzyme activities. The “fast-oxidative” state produced by stimulation at 2.5 Hz was stable: even after 10 months, 84% of the fibers were of type 2A. Absence of a secondary decline in oxidative activity in these muscles provided strong evidence of a causal link between myosin transitions and metabolic adaptation. Significant fiber loss occurred only after prolonged stimulation at 10 Hz. The myosin isoform composition of individual muscles stimulated at 5 Hz resembled that of muscles stimulated at either the lower or the higher frequency, behavior consistent with a threshold for fiber type change. In clinical applications such as cardiomyoplasty, muscles could be used more effectively by engineering their properties to combine speed and power of contraction with the necessary resistance to fatigue. © 1998 John Wiley & Sons, Inc. Muscle Nerve 21: 1632–1646, 1998