MIECT: How did it start?

Transiently assuming the functions of both heart and lungs as surgeons repair critical valves and vessel lesions can be achieved by mechanical circulatory support has its origins in cardiopulmonary bypass (CPB). However, CPB technologies induce also some unintended adverse effects. During the 90s, a mayor trend pushed many physicians to reconsider the place of coronary artery bypass grafting (CABG) and challenged the surgical reference treatment by less invasive catheter-based angioplasties. Nevertheless, best long-term patient outcomes were related to surgery. Therefore, a small number of multidisciplinary teams in Regensburg and Paris started to develop a minimally invasive CPB system. The basic concept relied on a closed-loop perfusion circuit with a non-occlusive pump. Moreover, the team in Paris pushed the concept further and developed a complete fully integrated CPB system allowed first closed-heart and later open-heart surgery with aortic cross-clamping and efficient cardioprotection. Those were the initial steps towards the future developments of minimally invasive extracorporeal circulation technologies. Initial clinical results were clearly positive in terms of overall morbimortality. Moreover, several preliminary results pointed out the biological benefits that decreased hemodilution, improved preservation of the immune reactions and more stable anticoagulation could bring to the field of ECT.

Long-term results of Freestyle stentless bioprosthesis in the aortic position: a single-center prospective cohort of 500 patients.

OBJECTIVE: Stentless xenograft bioprostheses may be the future valve of choice for aortic valve replacement. The study aim was to investigate the long-term clinical outcome after aortic valve replacement with the Medtronic Freestyle bioprosthesis (Medtronic Inc, Minneapolis, Minn). METHODS: Between April 1997 and November 2004, a total of 500 patients (mean age, 74.5±9.6 years; 52% were male) underwent aortic valve replacement with a Freestyle bioprosthesis, without population selection. The surgical procedure used a modified subcoronary technique in 479 patients and a complete root replacement in 21 patients, conducted with mini-extracorporeal circulation. Concomitant procedures included coronary artery bypass grafting in 122 patients (24%) and mitral valve repair/replacement in 11 patients. RESULTS: The mean cardiopulmonary bypass time was 98±26 minutes, and total aortic crossclamp time was 77±19 minutes. Operative mortality was 5.2%. The median follow-up time was 104.8±5.7 months. During this period, there were 224 deaths (n=122 cardiovascular and n=102 noncardiovascular deaths). The actuarial survivals from cardiovascular and valve-related mortality were 67%±3% and 70%±4%, respectively, at 10 years. Freedom from structural valve deterioration at 10 years was 94%±2%. The linearized structural valve deterioration incidence was 0.6% per patient/year. Multivariate Cox regression analysis revealed that older age, impaired renal function, and coronary artery disease were independent predictors of cardiovascular death. In the subgroup of patients aged less than 65 years at implantation (n=45), the actuarial cardiovascular survival was 83%±8% and freedom from structural valve deterioration was 89%±6% at 10 years. CONCLUSIONS: The use of the Freestyle bioprosthesis for aortic valve replacement resulted in good long-term cardiovascular survival and freedom from structural valve deterioration in this cohort regardless of age at implantation.

Alternative to the bentall procedure for elderly patients with aortic root aneurysms.

We describe an alternative technique to the Bentall procedure for elderly patients with aortic root aneurysms. It is the subcoronary implantation of a Freestyle (Medtronic, Minneapolis, MN) aortic bioprosthesis with interposition of a graft material between the upper part of the Freestyle bioprosthesis and the distal aorta. The technique described avoids the proximal anastomosis of the graft and avoids the coronary reimplantations of the Bentall procedure which are still a potential risk of bleeding particularly in elderly patients.

A technique of aortic annulus enlargement with a Freestyle stentless bioprosthesis.

We describe our surgical technique to manage a small aortic annulus during aortic valve replacement. Starting with the posterior annular enlargement incision described by Manouguian, a stentless porcine aortic root, with excision of the left and right porcine coronary segments and conservation of the mural wall (Freestyle MS design, Medtronic, Minneapolis, MN ), was used. The Freestyle bioprosthesis enlarges the aortic annulus using a direct suture of the valve on the enlarged annulus, and the aorta is closed by a direct suture of the mural wall of the bioprosthesis. Therefore, the aortic annulus enlargement is made only using the aortic bioprosthesis, without other material.

Eight-year results of Freestyle stentless bioprosthesis in the aortic position: a single-center study of 500 patients.

BACKGROUND AND AIM OF THE STUDY: Stentless bioprostheses may be the future valve of choice for aortic valve replacement (AVR). The study aim was to investigate mid-term clinical outcome after AVR with the Medtronic Freestyle valve. METHODS: Between April 1997 and November 2004, a total of 500 patients (241 females, 259 males) was implanted with a Freestyle bioprosthesis for AVR, without population selection, by a single surgical team at the authors' institutions. Mean patient age was 74.5 +/- 9.6 years (range: 26-91 years); 34 patients (7%) were aged < 60 years, 121 (24%) were aged > 80 years, and 205 (41%) were in NYHA classes III or IV. The surgical procedure used included a modified subcoronary technique in 482 cases and complete root replacement in 18, conducted with mini-extracorporeal circulation. Concomitant procedures included coronary artery bypass grafting in 123 patients (25%), mitral valve repair/replacement in five, and maze in two. Follow up was 98% complete; the mean follow up was 31.3 months (range: 4-95 months). RESULTS: The mean cardiopulmonary bypass time was 98 +/- 26 min, and total aortic cross-clamp time 77 +/- 19 min. Operative mortality was 5.2% (n = 26), and no patients aged under 60 years died. At eight years, freedom from structural valve deterioration was 100% (0% in the young population), freedom from endocarditis 97.2%, freedom from reoperation 97%, and overall survival 83%. Most of the late deaths (n = 56) were of non-cardiac origin, and occurred in older patients. After one year, the mean aortic echocardiographic gradient was 11.5 +/- 1.1 mmHg, and was improved compared to that at discharge. No significant aortic insufficiency occurred. CONCLUSION: Use of the Freestyle stentless bioprosthesis for AVR resulted in excellent short-term survival in the octogenarian population, and excellent mid-term results in the younger population. In time, experience will indicate whether the Freestyle should be considered as the bioprosthesis of choice for patients of all ages.

Comparison of the inflammatory response between miniaturized and standard CPB circuits in aortic valve surgery.

OBJECTIVE: One of the complications of CPB is the systemic inflammatory response syndrome (SIRS). Recent developments tend to minimize the biological impact of CPB in using miniaturized closed circuit with reduced priming volume and less blood-air interface. The benefit of these miniaturized closed circuits in terms of inflammatory response has been proved in coronary surgery. However, in open heart surgery, the CPB circuit is no more closed and the benefit of the miniaturized set-up could disappear. The aim of the study is to compare the SIRS between standard and miniaturized circuits in aortic surgery. METHODS: Forty patients who underwent singular aortic valve replacement were randomly assigned either to a standard CPB (group A, n=20) or to a miniaturized CPB (group B, n=20). Pertinent clinical and surgical data were collected. Hematological parameters (leukocyte and neutrophil counts) and biochemical parameters (C-reactive protein, cytokine tests) were determined pre-, on and post-CPB. RESULTS: There were an increase in leukocyte and neutrophil counts and a decline in hematocrit in both groups. In both groups, there was a raise after CPB, in C-reactive protein, IL-6, TNF-alpha, neutrophil elastase, and IL-10. However, the raises of elastase and TNF-alpha were significantly lower after the weaning of miniaturized CPB (116+/-46 ng/ml and 10+/-4 pg/ml, respectively) compared to standard CPB (265+/-120 ng/ml, P=0.01 and 18+/-7 pg/ml, P=0.03). The raise of IL-10 is also lower with miniaturized circuit (15+/-6 pg/ml) compared to standard circuit (51+/-26, P=0.004). CONCLUSIONS: This study demonstrates in aortic surgery, the lesser inflammatory response of a miniaturized CPB compared to a standard CPB. However, there is always some inflammation after CPB and a small bio-reactive free perfusion circuit is still to be found in open heart surgery.

Routine use of bilateral skeletonized internal thoracic artery grafts in middle-aged diabetic patients.

BACKGROUND: The purpose of this study was to determine whether middle-aged diabetic patients aged less than 70 years could have routine use of bilateral skeletonized internal thoracic artery grafting without an increased surgical risk. METHODS: Between January 1997 and December 2003, 712 consecutive patients aged less than 70 years underwent bilateral internal thoracic artery grafting. Among these, 164 were diabetic and underwent bilateral internal thoracic artery grafting without other preoperative selection than age. The postoperative results of these 164 nonselected consecutive diabetic patients were compared to these of the 548 nondiabetic patients. RESULTS: The operative mortality rate was 4.3% (7 patients) in the diabetic group and 2.4% (13 patients) in the nondiabetic group (p = not significant [NS]). Deep sternal wound infection was observed in 2 patients (1.1%) in the diabetic group and in 6 patients (1.2%) in the nondiabetic group (p = NS). There were no significant difference in the morbidity rate between the two groups except for renal failure without dialysis (6.7% in the diabetic group vs 2.0% in the nondiabetic group, p < 0.01). CONCLUSIONS: Routine use of bilateral internal thoracic artery grafting was performed in nonselected middle-aged diabetic patients without increased morbidity. The low rate of deep wound infections could be related to the skeletonized technique of internal thoracic artery harvesting.

Reduction of the inflammatory response following coronary bypass grafting with total minimal extracorporeal circulation.

OBJECTIVE: Cardiopulmonary bypass (CPB) is known to cause part of the systemic inflammatory reaction after cardiac surgery that can be responsible for organ failure. A novel technique based on a minimal extracorporeal circulation (MECC(R)) system has been evaluated with regard to the inflammatory response in a prospective study involving patients undergoing coronary artery bypass grafting. METHODS: Sixty consecutive patients were randomly assigned to either standard normothermic CPB (n=30) or the MECC system, with a reduced priming volume, no aortic venting and no venous reservoir, excluding the blood-air interface (n=30). Specific evaluation of cytokine release (IL-1beta, IL-6, TNF-alpha), as well as neutrophil elastase secretion and beta-thromboglobulin release from platelets and S100 protein assay were performed. Serial blood samples were taken prior to the onset, after initiation, at the end and after weaning of the CPB; further samples were collected 6 and 24h after the end of the CPB. RESULTS: All patients were similar with regards to pre- and intra-operative characteristics and clinical outcomes were comparable for both groups. MECC system allowed a reduced hemodilution with a mean drop of the hematocrit of 8.5 vs. 15.3% (P<0.05). Mononuclear phagocytes dropped in a more important manner under standard CPB conditions (247+/-151 vs. 419+/-168, P=0.002), but both groups demonstrated a rise in monocyte count at the end of the CBP. No significant release of IL-1beta was observed in either group. By the end of CPB, IL-6 levels were significantly lower in the MECC group (38.8+/-19.6 vs. 87.9+/-78.9, P=0.04), despite a higher monocyte count. Plasma levels of TNF-alpha rised significantly more during standard CPB than with the MECC system (17.8+/-15.4 vs. 10.1+/-5.6, P=0.002). With MECC, the neutrophil elastase release was reduced (72.7+/-47.9 vs. 219.6+/-103.4, P=0.001). Platelet count remained at higher values with the minimal compared to standard CPB. It is noteworthy to consider that beta-thromboglobulin levels showed slightly lower platelet activation in the MECC group at all times of CPB (110.5+/-55.6 vs. 134.7+/-46.8, P=0.10). The pattern of release of S100 protein showed higher values in patients undergoing standard CPB than after MECC. CONCLUSIONS: The MECC system is suitable to maintain total extracorporeal circulation and demonstrates a lower inflammatory reaction when compared to standard CPB.