Paul Philipp Heinisch

Graft preservation solutions in cardiovascular surgery.

Vein grafts are still the most commonly used graft material in cardiovascular surgery and much effort has been spent in recent years on investigating the optimal harvesting technique. One other related topic of similar importance remained more or less an incidental one. The storage solutions of vein grafts following procurement and prior to implantation are, despite their assumed impact, a relatively neglected theme. There is no doubt that the endothelium plays a key role in long-term patency of vein grafts, but the effects of the different storage solutions on the endothelium remain unclear : In a review of the literature, we could find 20 specific papers that addressed the question, of which the currently available preservation solutions are superior, harmless, damaging or ineffective. The focus lies on saline and autologous whole blood. Besides these two storage media, novel or alternative solutions have been investigated with surprising findings. In addition, a few words will be spent on potential alternatives and novel solutions on the market. As there is currently no randomized clinical trial regarding saline versus autologous whole blood available, this review compares all previous studies and methods of analysis to provide a certain level of evidence on this topic. In summary, saline has negative effects on the endothelial layers and therefore may compromise graft patency. Related factors, such as distension pressure, may outbalance the initial benefit of autologous whole blood or storage solutions and intensify the harmful effects of warm saline. In addition, there is no uniform consent on the superiority of autologous whole blood for vein graft storage. This may open the door to alternatives such as the University of Wisconsin solution or one of the specific designed storage solutions like TiProtec™ or Somaluthion™. Whether these preservation solutions are superior or advantageous remains the subject of further studies.

Long-term follow-up after implantation of the Shelhigh® No-React® complete biological aortic valved conduit

OBJECTIVES Long-term follow-up reports after implantation of the Shelhigh® (Shelhigh, Inc., NJ, USA) No-React® aortic valved conduit used for aortic root replacement do not exist. METHODS Between November 1998 and December 2007, the Shelhigh® No-React® aortic valved conduit was implanted in 291 consecutive patients with a mean age of 69.6 ± 9.1 years, and 33.7% were female (n = 98). Indications were annulo-aortic ectasia (n = 202), aortic valve stenosis combined with ascending aortic aneurysm (n = 67), acute type A aortic dissection (n = 29), endocarditis (n = 26) and other related pathologies (n = 48) including 62 patients with previous cardiac surgery. Data from two cardiac institutions were analysed retrospectively using SPSS (SPSS Software IBM, Inc., 2014, NY, USA). RESULTS Operative mortality was 10% (n = 29). Main cause of death was cardiac failure in 15 patients (51.8%), neurological events in 6 patients (20.7%), respiratory failure in 4 patients (13.8%), bleeding complications in 2 patients (6.9%) and gastrointestinal ischaemia in 2 cases (6.9%). There were 262 hospital survivors and all were entered in the follow-up study (100% complete). During the long-term follow-up (mean 70.3 ± 53.1 in months), a total of 126/262 patients (44.3%) died. Main causes of death in patients after discharge were cardiac (n = 37, 14.1%), neurological (n = 15, 5.7%) respiratory (n = 12, 4.6%), endocarditis (n = 12, 4.6%) and peripheral vascular disease (n = 5, 1.9%). In 29 (11.1%) patients, the cause of death could not be determined. Reoperation was required in 25 (8.6%) patients due to infection of the conduit (n = 9), aortoventricular disconnection (n = 4), pseudoaneurysm formation (n = 4) and structural valve degeneration (n = 8). Reoperations were performed 5.0 ± 3.8 (range 0.1-11.7) years after index surgery. CONCLUSIONS The Shelhigh® No-React® aortic valved conduit showed satisfactory short-term operative results. However, the long-term follow-up revealed a relatively high rate of deaths, which may be explained by the epidemiology of the patient group, but a substantial proportion of deaths could not be clarified. The overall rate of reoperation (8.6%) during the mid-term follow-up is worrisome and the failures due to aortoventricular disconnection, endocarditis and pseudoaneurysm formation remain unexplained. The redo-procedures were technically demanding. We recommend close follow-up of patients with the Shelhigh® No-React® aortic valved conduit, because besides classical structural valve degeneration, unexpected findings may be observed.

Transvalvular pressure gradients for different methods of mitral valve repair: only neochordoplasty achieves native valve gradients

OBJECTIVES Many surgical and interventional methods are available to restore patency for patients with degenerative severe mitral valve regurgitation. Leaflet resection and neochordoplasty, which both include ring annuloplasty, are the most frequently performed techniques for the repair of posterior mitral leaflet flail. It is unclear which technique results in the best haemodynamics. In this study, we investigated the effect of different mitral valve reconstruction techniques on mitral valve haemodynamics and diastolic transvalvular pressure gradient in an ex vivo porcine model. METHODS Eight porcine mitral valves were tested under pulsatile flow conditions in an in vitro pulsatile flow loop for haemodynamic quantification. Severe acute posterior mitral leaflet flail was created by resecting the posterior marginal chorda. The acute mitral valve regurgitation was corrected using 4 different repair techniques, in each valve, in a strictly successive order: (i) neochordoplasty with polytetrafluoroethylene sutures alone and (ii) with ring annuloplasty, (iii) edge-to-edge repair and (iv) triangular leaflet resection, both with ring annuloplasty. Valve haemodynamics were measured and quantified for all valve configurations (native, rupture and each surgical reconstruction). The results were analysed using a validated statistical linear mixed model, and the P-values were calculated using a 2-sided Wald test. RESULTS All surgical reconstruction techniques were able to sufficiently correct the acute mitral valve regurgitation. Neochordoplasty without ring annuloplasty was the only reconstruction technique that resulted in haemodynamic properties similar to the native mitral valve (P-values from 0.071 to 0.901). The diastolic transvalvular gradient remained within the physiological range for all reconstructions but was significantly higher than in the native valve for neochordoplasty with ring annuloplasty (P < 0.000), edge-to-edge repair (P < 0.000) and leaflet resection (P < 0.000). Neochordoplasty without ring annuloplasty resulted in a significantly better pressure gradient than neochordoplasty with a ring annuloplasty (P < 0.000). Additionally, neochordoplasty with a ring annuloplasty resulted in significantly lower transvalvular pressure gradients than edge-to-edge repair (P < 0.000) and leaflet resection (P < 0.000). CONCLUSIONS Neochordoplasty with or without ring annuloplasty was the reconstruction technique that almost achieved native physiological haemodynamics after repair of posterior mitral leaflet flail after acute isolated chordal rupture in our ex vivo porcine model.

Right atrial pressure and venous return during cardiopulmonary bypass

The relevance of right atrial pressure (RAP) as the backpressure for venous return (QVR) and mean systemic filling pressure as upstream pressure is controversial during dynamic changes of circulation. To examine the immediate response of QVR (sum of caval vein flows) to changes in RAP and pump function, we used a closed-chest, central cannulation, heart bypass porcine preparation (n = 10) with venoarterial extracorporeal membrane oxygenation. Mean systemic filling pressure was determined by clamping extracorporeal membrane oxygenation tubing with open or closed arteriovenous shunt at euvolemia, volume expansion (9.75 ml/kg hydroxyethyl starch), and hypovolemia (bleeding 19.5 ml/kg after volume expansion). The responses of RAP and QVR were studied using variable pump speed at constant airway pressure (PAW) and constant pump speed at variable PAW Within each volume state, the immediate changes in QVR and RAP could be described with a single linear regression, regardless of whether RAP was altered by pump speed or PAW (r2 = 0.586-0.984). RAP was inversely proportional to pump speed from zero to maximum flow (r2 = 0.859-0.999). Changing PAW caused immediate, transient, directionally opposite changes in RAP and QVR (RAP: P ≤ 0.002 and QVR: P ≤ 0.001), where the initial response was proportional to the change in QVR driving pressure. Changes in PAW generated volume shifts into and out of the right atrium, but their effect on upstream pressure was negligible. Our findings support the concept that RAP acts as backpressure to QVR and that Guytons model of circulatory equilibrium qualitatively predicts the dynamic response from changing RAP.NEW & NOTEWORTHY Venous return responds immediately to changes in right atrial pressure. Concomitant volume shifts within the systemic circulation due to an imbalance between cardiac output and venous return have negligible effects on mean systemic filling pressure. Guytons model of circulatory equilibrium can qualitatively predict the resulting changes in dynamic conditions with right atrial pressure as backpressure to venous return.

Aortic root stiffness affects the kinematics of bioprosthetic aortic valves

Objectives In this study, the influence of aortic root distensibility on the haemodynamic parameters and valve kinematics of a bioprosthetic aortic valve was investigated in a controlled in vitro experiment. Methods An Edwards INTUITY Elite 21 mm sutureless aortic valve (Edwards Lifesciences, Irvine, CA, USA) was inserted in three transparent aortic root phantoms with different wall thicknesses (0.55, 0.85 and 1.50 mm) mimicking different physiological distensibilities. Haemodynamic measurements were performed in an in vitro flow loop at heart rates of 60, 80 and 100 bpm with corresponding cardiac outputs of 3.5, 4.0 and 5.0 l/min and aortic pressures of 100/60, 120/90 and 145/110 mmHg, respectively. Aortic valve kinematics were assessed using a high-speed camera. The geometric orifice area (GOA) was measured by counting pixels in the lumen of the open aortic valve. The effective orifice area (EOA) was calculated from the root-mean-square value of the systolic aortic valve flow rate and the mean systolic trans-valvular pressure gradient. Results The tested aortic root phantoms reproduce physiological distensibilities of healthy individuals in age groups ranging from 40 to 70 years (±10 years). The haemodynamic results show only minor differences between the aortic root phantoms: the trans-valvular pressure gradient tends to increase for stiffer aortic roots, whereas the systolic aortic valve flow rate remains constant. As a consequence, the EOA decreased slightly for less distensible aortic roots. The GOA and the aortic valve opening and closing velocities increase significantly with reduced distensibility for all haemodynamic measurements. The resulting mean systolic flow velocity in the aortic valve orifice is lower for the stiffer aortic root. Conclusions Aortic root distensibility may influence GOA and aortic valve kinematics, which affects the mechanical load on the aortic valve cusps. Whether these changes have a significant effect on the onset of structural valve deterioration of bioprosthetic heart valves needs to be further investigated.

Mitral valve replacement in patients under 65 years of age: mechanical or biological valves?

Purpose of review There is controversy regarding the optimal choice of prosthetic valves in patients less than 65 years of age requiring mitral valve replacement (MVR). Recently, trends for valve replacement are moving towards biological prosthesis also in younger patients, which is justified by the fact that a later valve-in-valve procedure is feasible in the case of degeneration of the tissue valve. This strategy is increasingly recommended in aortic valve surgery but is questionable for MVR. The purpose of this review is to evaluate current guidelines and analyse evidence for biological MVR in patients under 65 years. Recent findings There are differences between guidelines of the American Heart Association and those of the European Society of Cardiology concerning the choice of prostheses in patients undergoing MVR. Although the European Society of Cardiology recommends a mechanical mitral valve in patients under 65 years of age, the American Heart Association does not provide detailed advice for these patients. Mitral valve replacement with biological valves in patients under 65 years is associated with higher rates of reoperation due to structural valve deterioration. In addition, several studies showed a decreased survival after biological MVR. Summary Evidence for biological MVR in patients less than 65 years without comorbidities or contraindication for oral anticoagulation does not exist. Recommendations for patients less than 65 years of age should not be blurred by current ‘en-vogue’ methods for promising but not yet proven valve-in-valve strategies.

Minimally Invasive Extracorporeal Circulation Circuit Is Not Inferior to Off-Pump Coronary Artery Bypass Grafting: Meta-Analysis Using the Bayesian Method

The pathophysiologic side effects of cardiopulmonary bypass have already been identified. Minimally invasive extracorporeal circulation technologies (MiECT) and off-pump coronary artery bypass graft surgery (OPCABG) aim to reduce these problems. This meta-analysis provides a comparison of MiECT and OPCABG in randomized and observational studies. A fully probabilistic, Bayesian approach of primary and secondary endpoints was conducted. MiECT does not give inferior results when compared with OPCABG. However, there is a trend to borderline significantly higher blood loss in this group in randomized controlled trials. The question whether MiECT is equivalent to OPCABG can be answered with the affirmative, but long-term follow-up data are needed to detect any advantage over time.

Minimally invasive extracorporeal circulation: excellent outcome and life expectancy after coronary artery bypass grafting surgery

OBJECTIVE Coronary artery bypass grafting (CABG) remains the gold standard for complex revascularisation in multivessel disease. The concept of the minimally invasive extracorporeal circulation circuit (MiECC) was introduced to minimise pathophysiological side effects of conventional extracorporeal circulation. This study presents early and long-term outcomes after CABG with use of MiECC in a single-centre consecutive patient cohort. METHODS From 1 January 2005 to 31 December 2010, 2130 patients underwent isolated CABG with MiECC at our centre. We evaluated morbidity and mortality follow-up data with a median follow-up of 3.6 years. Kaplan-Meier curves and estimates of the primary end-point for all-cause mortality were compared with the life expectancy of the general population. RESULTS Mortality in CABG patients was comparable to the general population beginning 1 year after surgery for the whole observation period. All-cause 30-day mortality was 0.8%. The mean estimated logistic EuroSCORE and EuroSCORE II were 5.8 ± 8.6 and 3.0 ± 5.1, respectively. Mean perfusion time was 71.1 ± 23.8 min with a cross-clamp time of 44.9 ± 16.3 min. Mortality was predicted by the presence of diabetes mellitus (odds ratio [OR] 1.85, 95% confidence interval [CI] 1.40-2.46; p <0.001), peripheral arterial disease (OR 2.36, 95% CI 1.64-3.38; p <0.001), severe obstructive pulmonary disease (OR 3.21, 1.42-7.24; p = 0.005), chronic renal failure (OR 3.68, 2.49-5.43; p <0.001) and transfusion of more than one unit of erythrocyte concentrate in the perioperative period (OR 1.46, 1.09-1.95; p = 0.015). Cerebrovascular events occurred in 36 patients (1.7%). CONCLUSION CABG with use of MiECC is associated with a mortality rate comparable to the overall life expectancy of the general population. MiECC is the first choice for routine and emergency CABG at our centre with a 30-day mortality rate of 0.8% and a low complication rate.

Type A aortic dissection model to improve endovascular research and technologies

Objective Type A aortic dissection is a life-threatening disease requiring immediate surgical treatment. With emerging catheter-based technologies, endovascular stent-graft implantation to treat aneurysms and dissections has become a standardized procedure. However, endovascular treatment of the ascending aorta remains challenging. Thus we designed an ascending aortic dissection model to allow simulation of endovascular treatment. Methods Five formalin-fixed human aortas were prepared. The ascending aorta was opened semicircularly in the middle portion and the medial layer was separated from the intima. The intimal tube was readapted using running monofilament sutures. The preparations were assessed by 128-slice computed tomography. A bare-metal stent was implanted for thoracic endovascular aortic repair in 4 of the aortic dissection models. Results Separation of the intimal and medial layer of the aorta was considered to be sufficient because computed tomography showed a clear image of the dissection membrane in each aorta. The dissection was located 3.9 ± 1.4 cm proximally from the aortic annulus, with a length of 4.6 ± 0.9 cm. Before stent implantation, the mean distance from the intimal flap to the aortic wall was measured as 0.63 ± 0.163 cm in the ascending aorta. After stent implantation, this distance decreased to 0.26 ± 0.12 cm. Conclusion This model of aortic dissection of the ascending human aorta was reproducible with a comparable pathological and morphological appearance. The technique and model can be used to evaluate new stent-graft technologies to treat type A dissection and facilitate training for surgeons.

Hemodynamic performance of Edwards Intuity valve in a compliant aortic root model

Numerous designs of bioprosthetic valves exist. The sutureless surgical valve is a newer design concept which combines elements of the transcatheter valve technology with surgical valves. This design aims at shorter and easier implantation. It was the aim of this study to perform hemodynamic and kinematic measurements for this type of valves to serve as a baseline for following studies which investigate the effect of the aortic root on the valve performance. To this end, the Edwards Intuity aortic valve was investigated in a new in vitro flow loop mimicking the left heart. The valve was implanted in a transparent, compliant aortic root model, and the valve kinematics was investigated using a high speed camera together with synchronized hemodynamic measurements of pressures and flows. The valve closure was asynchronous (one by one leaflet), and the valve started to close before the deceleration of the fluid. The aortic root model showed a dilation of the sinuses which was different to the ascending aorta, and the annulus was found to move towards the left ventricle during diastole and towards the aorta during systole.