Does external stenting reduce porcine vein-graft occlusion via an action on vascular nerves?

BACKGROUND: Neural reorganization occurs in porcine vein grafts and placement of an external stent reduces graft occlusion. AIM OF THE STUDY: To determine the effect of external stenting on the innervation of porcine vein grafts. METHODS: Saphenous vein into carotid artery grafting (with and without external stents) was performed in 16 pigs. After one and six months, grafts were removed, nerves were counted, and neointima was assessed. RESULTS: In vein graft compared to ungrafted vein, there was a significant (p < 0.05) decrease in medial perivascular nerves, but a dramatic increase in paravascular nerves in the adventitia (p < 0.05). In stented vein grafts there was also a reduction of perivascular nerves and the paravascular nerve proliferation observed in vein grafts at one month was inhibited (p < 0.05). Neointima formation and the appearance of large paravascular nerve bundles in the adventitia of vein grafts were abolished by external stenting. CONCLUSIONS: Neural reorganization plays a role in vein-graft failure, possibly through the local release of mitogens; the prevention of this reorganization contributes to the inhibitory effect of the external stent on neointima formation.

Place of video-thoracoscopy in thoracic surgical practice.

The advent of video-endoscopy revolutionizes the practice of surgery. Within a short span of time, video-assisted thoracic surgery (VATS) has become an acceptable approach to a wide range of thoracic procedures. The use of VATS as a diagnostic modality is now well established. For therapeutic procedures, VATS has also been generally accepted for the treatment of such conditions as primary spontaneous pneumothorax, loculated effusions, thoracodorsal sympathectomy, and resection of simple mediastinal cysts. Its roles in more complex procedures such as thymectomy and anatemic lung resections, however, remain poorly defined at present, even though the existing intermediate-term results are encouraging. VATS is still in evolution. Miniaturization of instruments promises to reduce access-induced trauma even further. On the other hand, attention to cost-containment is essential if VATS is to be applicable to patients in developing countries. Technology will continue to change. Carefully conducted clinical trials should precede the general acceptance of any new technology, no matter how attractive it may appear initially.

Macro-porosity is necessary for the reduction of neointimal and medial thickening by external stenting of porcine saphenous vein bypass grafts.

BACKGROUND: placing external non-restrictive macro-porous stents around porcine vein grafts prevents neointima formation and medial thickening in both the short and long term. Whether the porosity of the stent material influences this effect, however, has not been determined. Therefore, the effect on neointimal and medial thickening of external macro-porous (polyester) and micro-porous (polytetrafluorethylene) stents of equal diameter were compared. The effect on expression of platelet-derived growth factor (PDGF), a potent mediator of vascular smooth muscle cell migration and proliferation and its receptors was also investigated. METHODS AND RESULTS: saphenous vein-carotid artery interposition grafting was performed in Landrace pigs with external placement of 8 mm diameter macro- and micro-porous stents contralaterally. One month after surgery, graft wall dimensions, PDGF and PDGF receptor expression and cell proliferation using proliferating cell nuclear antigen (PCNA) were measured on histological sections. Macro-porous stents significantly reduced neointimal and medial thickening compared with micro-porous stents (0.1+/-0.02 vs. 0.25+/-0.03 mm, P<0.002, and 0.10+/-0.02 vs. 0.17+/-0.02 mm, P<0.014, respectively). Macro-porous stents significantly reduced the percentage of cells expressing PDGF and PCNA, compared with micro-porous stents (36+/-9 vs. 80+/-7, P < 0.002, and 11+/-3 vs. 21+/-2, P < 0.02, respectively). The percentage of cells expressing PDGF receptors was similar with both the stent types. Adventitial microvessel formation occurred across macro-porous stents but was markedly suppressed by micro-porous stents. CONCLUSIONS: porosity is crucial to the efficacy of external stents in reducing neointima formation in porcine vein grafts. Decreases in PDGF expression and cell proliferation accompany the reduction in neointima formation. In addition, macro-porous stents allow adventitial microvessels to connect with the vasculature outside the stent, thereby potentially improving oxygenation. Although external stenting is highly effective in reducing neointima formation after vein grafting, the properties of the stent material necessary for this effect have not been defined. This study establishes that macro-porosity is one essential feature required to reduce PDGF expression cell proliferation and neointima formation.

Early experience with left ventricular volume reduction surgery in Syria.

OBJECTIVE: To review our early experience with left ventricular volume reduction surgery (the Batista operation) in the management of patients with end-stage heart failure. METHODS: Between December 1996 and April 1998, 10 patients (9 males, mean age 32yr) with advanced symptomatic cardiomyopathy underwent left ventricular volume reduction surgery at Damascus University Cardiovascular Surgical Center. The cause of cardiomyopathy was idiopathic in three patients, valvular in four, ischemic in two, and viral myocarditis in one patient. Concomitant procedures included aortic valve replacement in four patients, mitral valve repair in six patients, and coronary artery bypass grafting in two patients. RESULTS: All patients survived the procedure. Echocardiography prior to discharge documented significant improvement in ejection fraction in all but two patients. Mean follow-up was 7.6 months. After discharge, three patients developed progressive congestive heart failure to which they subsequently succumbed, and two more patients died suddenly late postoperatively. Only two patients continue to show both clinical and echocardiographic evidence of improvement. CONCLUSION: Left ventricular volume reduction surgery cannot be freely advocated until better means are found to identify patients who will benefit from the procedure, and proper prophylaxis against fatal postoperative complications can be afforded.

Patient-prosthesis mismatch is negligible with modern small-size aortic valve prostheses.

BACKGROUND: Concern has been raised about residual significant gradients when small aortic prostheses are used, particularly in patients with large body surface areas. We studied the performance of six types of small aortic prostheses using dobutamine stress echocardiography. METHODS: Sixty-three patients (mean age, 67 +/- 7 years) who had undergone aortic valve replacement 17 +/- 6 months previously were studied. Two bileaflet mechanical prostheses (St. Jude Medical and CarboMedics: sizes, 19 mm and 21 mm) and two biological prostheses (Medtronic Intact and St. Jude BioImplant: size, 21 mm) were evaluated. A graded infusion of dobutamine was given and Doppler studies of valve performance were carried out. RESULTS: All prostheses except one biological valve had acceptable hemodynamic performance under stress. Using regression modeling, gradient at rest was the only variable found to predict gradient under stress (p < 0.001). Moreover, the most important predictor of gradient at rest was valve design, which accounted for 72% of the variance (p < 0.001). This relationship was independent of valve size (19 mm or 21 mm) or material (ie, mechanical or biological). Body surface area accounted for 4% of the variance in gradient only. CONCLUSIONS: The main predictor of transprosthetic gradient is the inherent characteristics of each particular prosthesis, with relatively insignificant contribution from variations in body surface area. Patient-prosthesis mismatch is not a problem of clinical significance when certain modern valve prostheses are used.

Thoracoscopic surgery for pulmonary tuberculosis.

Tuberculosis historically was a major impetus for the development of thoracic surgery, and it remains a serious health problem of global proportion. Thoracoscopy was first introduced at the turn of this century for closed chest adhesiolysis as an adjunct to collapse therapy for treatment of tuberculosis. This indication became obsolete with the discovery of streptomycin during the 1940s; and for a long time since then thoracoscopy was used only sporadically for the diagnosis of pleural disease. However, over the last few years, modern video-assisted thoracoscopic surgery (VATS) has provided a new approach to the management of pulmonary tuberculosis. Over the last 5 years we have used VATS for diagnosis or treatment (or both) of 62 patients with pulmonary tuberculosis, including 20 pleural biopsies, 8 decortications, 17 wedge lung resections, 8 drainages of empyema, and 9 lobectomies. There was no surgical mortality, and complications were few. We conclude that VATS provides a safe, effective diagnostic modality (pleural biopsy, wedge resections) and therapeutic modality (decortications, drainage of empyema) for selected patients with pulmonary tuberculosis.

Thoracoscopic surgery for spontaneous pneumothorax.

Spontaneous pneumothorax in apparently healthy individuals is a relatively common occurrence. The management of patients with spontaneous pneumothorax remains controversial. With the advances in thoracoscopic techniques and instrumentation, video-assisted thoracic surgery (VATS) is now accepted by many as the procedure of choice for surgical treatment of spontaneous pneumothorax. We report our combined experience with 757 patients who suffered from recurrent or persistent spontaneous pneumothorax treated by VATS over a 5-year period. Surgical indications included persistent air leak (n = 165), recurrence (n = 325), radiologically demonstrated huge bulla (n = 12), spontaneous hemopneumothorax (n = 13), incomplete expansion of the lung (n = 212), and bilateral involvement (n = 30). Several surgical procedures were undertaken, based on the thoracoscopic findings: endoscopic stapled bullectomy (n = 312), argon beam coagulation (n = 6), endoscopic suturing (n = 52), and endoloop ligation (n = 352). In 49 cases, mechanical or chemical pleurodesis was the only procedure performed. There were no mortalities or intraoperative hazards. Complications consisted of wound infections (n = 16), localized empyema (n = 2), chest wall bleeding (n = 1), and persistent air leaks (bulla type III) (n = 31). The median duration of the operation was 55 minutes (15-160 minutes), and the average postoperative hospital stay was 4.5 days (range 0-27 days). There were 16 recurrences (2.1%), after a mean follow-up of 30 months (range 1-60 months). Seven patients had recurrence from 9 to 17 months after stapled bullectomy. All the remaining patients had recurrence after failed pleurodesis. On the basis of our results, we conclude that video-assisted thoracoscopic management allows effective, safe performance of standard surgical procedures, avoiding a formal thoracotomy incision. We consider thoracoscopy the treatment of choice for patients with pneumothorax requiring surgical therapy.

Increased secretion of basement membrane-degrading metalloproteinases in pig saphenous vein into carotid artery interposition grafts.

Late saphenous vein bypass graft failure in humans involves medial and neointimal thickening as the result of migration and proliferation of vascular smooth muscle cells (SMCs). Recent work on angioplasty indicates that basement membrane-degrading metalloproteinases (MMPs) cooperate with growth factors to mediate SMC migration and proliferation. We sought evidence here for a similar role in experimental vein grafts in pigs. Tissue levels and secretion of MMP-2 and MMP-9 were compared by quantitative zymography in veins and grafts removed 2 to 168 days after implantation. Pro and active forms of MMP-2 were present in veins, but levels were increased in vein grafts after 7 days (4- and 6-fold, respectively) and 28 days (3-fold for both), returning to values in veins after 168 days. MMP-9 was not detected in veins, was increased in grafts after 2 days, further increased after 7 days (6-fold) and 28 days (15-fold), and declined to undetectable levels by 168 days. Immunocytochemistry detected increased expression of MMP-2 and MMP-9 with the same time course. MMP-2 was widely distributed, whereas MMP-9 was concentrated in highly proliferative SMCs at the superficial layers of the thickened neointima. We conclude that increased production of the basement membrane-degrading MMP-2 and MMP-9 spanned the period of neointima formation and SMC proliferation in experimental vein grafts. MMPs therefore constitute new therapeutic targets for reducing late vein graft failure.

Avoiding cardiopulmonary bypass in multivessel CABG reduces cytokine response and myocardial injury.

BACKGROUND: Proinflammatory cytokines play a key role in the inflammatory cascade after cardiopulmonary bypass and may induce cardiac dysfunction. We compared the production of cytokines and the degree of postoperative myocardial injury in patients with multivessel coronary artery disease undergoing coronary artery bypass grafting through median sternotomy with or without cardiopulmonary bypass. METHODS: Forty-four consecutive patients were studied. Patients were selected for off-pump coronary artery bypass grafting whenever complete revascularization was technically feasible. There were no differences between the two groups with respect to age, sex, symptoms, or functional class. Plasma levels of tumor necrosis factor-alpha, interleukin (IL)-6, IL-8, and IL-10 were measured before the operation, at the end of the procedure, and 2, 4, 8, 24, and 48 hours thereafter. Levels of the MB isoenzyme of creatine kinase and cardiac troponin-I were also measured after the operation. RESULTS: The number of grafts was 2+/-0.7 in the off-pump group (n = 18) and 3+/-0.8 in the cardiopulmonary bypass group (n = 26). There were no deaths or major complications in either group. Levels of tumor necrosis factor-alpha were low in both groups. No significant intergroup differences were noted regarding serial IL-6 measurements. However, IL-8 and IL-10 levels after the operation were lower in the off-pump group (IL-8, 4+/-1 versus 38+/-12 pg/mL, p < 0.01; IL-10, 5+/-2 versus 191+/-33 pg/mL, p < 0.001). Whereas postoperative creatine kinase-MB values were similar in the two groups, cardiac troponin-I levels were significantly lower in the off-pump group (8 hours, p < 0.005; 24 hours, p < 0.02, respectively). Moreover, cardiac troponin-I values 24 hours after operation correlated strongly with IL-8 levels (r = 0.61, p < 0.005), indicating that the degree of myocardial injury may be related to IL-8 production. CONCLUSIONS: Compared with conventional coronary artery bypass grafting, coronary revascularization without cardiopulmonary bypass is associated with reduced cytokine responses and less myocardial injury.

Early experience with partial left ventriculectomy in the Asia-Pacific region.

BACKGROUND: We report our early experience with partial left ventriculectomy done by a group of cardiac surgeons in the Asia-Pacific region. METHODS: Partial left ventriculectomy was done in 48 patients (mean age, 43 years) with advanced symptomatic cardiomyopathy. The origin of cardiomyopathy was idiopathic in 30 patients, valvular in 10, ischemic in 3, peripartum in 3, sarcoidosis in 1, and viral myocarditis in 1. Procedures performed on the mitral valve were repair with Alfieri method in 8 patients, ring annuloplasty in 2, and replacement in 25. RESULTS: Seventy-seven percent of patients required myocardial support for weaning from cardiopulmonary bypass, and the overall in-hospital mortality rate was 27%. Mean follow up was 6.5 months (range, 1 to 18 months), and patient survival at 1, 3, and 6 months after discharge was 91%, 88%, and 84%, respectively. Sixty-five percent of survivors with idiopathic and valvular disease achieved significant and sustained improvement in ventricular contractility and symptoms, but there were no clear symptomatic benefits from partial left ventriculectomy in patients with cardiomyopathy from other causes. Most cases of late recurrence of heart failure symptoms (90%) appeared to be related to the development of progressive mitral incompetence. CONCLUSIONS: After partial left ventriculectomy left ventricular function improved in patients with idiopathic and valve related cardiomyopathies. Late deterioration was related to the development of significant mitral valve incompetence postoperatively, hence definitive mitral valve repair or replacement at the time of the partial left ventriculectomy procedure is advised.

Ministernotomy for aortic valve replacement in a patient with osteogenesis imperfecta.

Open heart operations in patients with osteogenesis imperfecta are associated with increased morbidity and mortality resulting from tissue friability and bone brittleness. We used a ministernotomy approach for aortic valve replacement in a patient with osteogenesis imperfecta, with clear benefits and a satisfactory outcome.

Video-assisted thoracic surgery: a renaissance in surgical therapy.

Within a few years, video-assisted thoracic surgery (VATS) has become the accepted or preferred approach over a wide range of thoracic procedures. The authors review the development of this technique, the basic operative strategies and the current surgical indications. Technical pitfalls and future developments are also discussed.

A survey on partial left ventriculectomy in the Asia-Pacific region.

BACKGROUND: There has been increasing interest in partial left ventriculectomy as a new therapy for end-stage heart failure. Because the most significant impact of this development is likely to be in regions where heart transplantation is largely unavailable, we conducted a survey among a group of cardiac surgeons based in the Asia-Pacific region to evaluate their overall views on partial left ventriculectomy procedures. METHODS: A questionnaire was sent to surgeons from 65 major institutions in 17 countries and regions in the Asia-Pacific. Questions examined current demographics and opinions regarding potential application and future prospects of this operation. RESULTS: Surveyed surgeons were based in equal proportions in academic, government, and private practice institutions. One third of respondents have already performed partial left ventriculectomy operations, largely in small numbers. In total, 86 procedures were performed with 75% hospital survival rate. Failures were thought to be caused by limited knowledge about patient selection criteria and lack of experience with operative technique and perioperative care. The majority of respondents believe that partial left ventriculectomy is potentially a valuable intervention and intend to perform more cases. Nevertheless, most surgeons identified the need to have larger clinical experience, to perform randomized trials against other therapeutic modalities, and to improve perioperative care. CONCLUSIONS: Although all surgeons recognize that more knowledge is needed before partial left ventriculectomy becomes a standard procedure, it is clear from this survey that the procedure has rapidly gained interest, with more surgeons seeking to learn it.

Routine intraoperative angiography improves the early patency of coronary grafts performed on the beating heart.

OBJECTIVES: The techniques of performing coronary revascularization without cardiopulmonary bypass are rapidly evolving. However, concern remains regarding the accuracy of coronary artery anastomoses performed on the beating heart. This report reviews the use of intraoperative angiography in the critical appraisal of "off-pump" coronary artery bypass graft (CABG) surgery. PATIENTS: Intraoperative angiography was performed in 24 consecutive patients undergoing CABG surgery without cardiopulmonary bypass. In all, 24 left internal mammary artery (LIMA) grafts and 18 saphenous vein bypass grafts were assessed for patency, anastomosis quality, distal and proximal runoff, and correct placement. RESULTS: All of the saphenous vein-to-coronary artery anastomoses were widely patent, although two patients (8%) required revision of their LIMA grafts on the basis of angiographic findings. CONCLUSION: Intraoperative angiography permits the surgeon to immediately appraise the CABG and to revise, if necessary, any graft abnormality, thus potentially eliminating the need for early repeated surgery. The practice of routine intraoperative angiography is likely to improve the outcome of CABG surgery on the beating heart.

Favorable scanning electron microscopic findings of stapled saphenous vein-carotid artery anastomoses.

BACKGROUND: In the progress toward "off-pump" endoscopic coronary artery surgical procedures, new techniques for coronary artery anastomoses are being developed. One such approach is the use of nonpenetrating titanium clips. We evaluated the quality of anastomoses achieved using this technique in a porcine model of saphenous vein-carotid artery grafting using scanning electron microscopy. METHODS: Bilateral saphenous vein-carotid artery interposition grafts were implanted in 10 "white race" pigs, using the nonpenetrating clips in one side of the neck and conventional hand suturing on the opposite side. One week after operation, the grafts were harvested. RESULTS: All grafts were patent 7 days after operation, and 40 anastomoses underwent scanning electron microscopic study. In all samples, the luminal surfaces of both the carotid artery and vein graft were covered by a continuous layer of endothelial cells up to the anastomosis. Anastomotic sites in all clipped samples and most of the sutured anastomoses were completely endothelialized, and anastomotic clefts were indistinguishable. However, in 25% of sutured specimens, the suture material remained clearly visible inside the lumen of the vessel, and the subendothelial matrix remained exposed, with extensive fibrin, red blood cells, and platelet deposition on its surface. CONCLUSIONS: Because the endothelial coverage consistently appeared to be complete and the subendothelial matrix was not exposed, it is likely that the risk of early anastomotic thrombosis is reduced by using the nonpenetrating titanium clips.

Video-assisted thoracoscopic thymectomy.

Video-assisted thoracoscopic surgery (VATS) provides a new, alternative approach to thymectomy and has several advantages over the other established techniques. However, even among surgeons using this approach, there are differences in the actual technique. We prefer the right approach using conventional instruments. The rationale behind our technique is discussed.

Video-assisted thoracoscopic thymectomy for myasthenia gravis.

Thymectomy is an established therapy in the management of generalized myasthenia gravis, in addition to medical treatment. However, the optimal surgical approach to thymectomy has remained controversial. There are advocates for transternal, transcervical approaches or "maximal" thymectomy. Video-assisted thoracic surgery (VATS) presents a new approach to thymectomy and forms the basis of this article, in which we discuss patient selection, technique, and results. We believe complete thymectomy, comparable with the transternal approach, could be achieved by VATS. Our intermediate-term results compare well with other surgical techniques. By minimizing chest wall trauma, VATS not only causes less postoperative pain, shortens hospital stay, gives better cosmetic results but also leads to wider acceptance by patients (and their neurologists) for earlier surgery. However, the true role of this approach in thoracic surgery awaits long-term results.

Perioperative care in left ventricular volume reduction.

BACKGROUND: While the operative technique of left ventricular volume reduction (LVVR) is rapidly becoming standardized, the optimal perioperative management strategy is yet to be determined. We present our experience with the care of patients undergoing LVVR. METHODS: LVVR was performed in 21 patients (mean age = 65.5 years) with congestive heart failure. Our management strategy was initially based on afterload reduction with sodium nitroprusside, but was later modified to include routine preoperative intra-aortic balloon support, normothermic cardiopulmonary bypass, antegrade intermittent warm blood cardioplegia, and postoperative support with phosphodiesterase-III inhibitors. Hemodynamic manipulations are aimed to attain systemic vascular resistance between 600 and 800 dyne/sec per cm(-5) and the lowest mean blood pressure that is able to maintain satisfactory systemic perfusion. Postoperatively, aggressive antifailure medical therapy with a high dose of angiotensin converting enzyme inhibitors, nitrates, and diuretics was initiated early and maintained indefinitely. RESULTS: Using this approach, postoperative progress was characterized by hemodynamic stability. IABP support was used for 59.6+/-9 hours following surgery, and inotropic support for 103+/-12 hours. In our series there were four (19%) in-hospital deaths, two of which were related to heart failure. CONCLUSION: The described approach is associated with an acceptable early outcome. However, further advances in myocardial protection methods and pharmacological and mechanical support techniques are necessary for a wider adoption of this procedure.