Minimized Cardiopulmonary Bypass Reduces Retinal Microembolization: A Randomized Clinical Study Using Fluorescein Angiography

Evaluation of cerebrovascular events via retinal angiography during transcatheter aortic valve implantation

OBJECTIVES

Patients receiving transcatheter aortic valve implantation (TAVI) are elderly with multiple comorbidities and at increased risk of perioperative cerebrovascular events. Retinal vasculature represents a surrogate of central nervous system circulation and is noninvasively achievable by retinal imaging. The aim of this study was to evaluate the applicability of retinal angiography of microvascular complications and association to cerebral ischemic events during TAVI.

DESIGN

One hundred patients (male 54%, age: median 82 years, range 64-95 years) undergoing TAVI were recruited for this study. Imaging of retinal vasculature was evaluated with a handheld fundus camera before, during and 1 month after. Cerebrovascular events were determined as a part of contemporary clinical evaluation with cerebral CT and CTA imaging when symptoms occurred.

RESULTS

Altogether 66/100 patients (66%) were included in the analysis. In-hospital ischemic event (transient ischemic attack, cerebral infarction) was observed in 1/66 patient (1.5%). Retinal vascular abnormalities occurred in 8/66 patients (12.1%); 4/66 patients (6.1%) were detected with a cholesterol plaque in the retinal artery, 2/66 (3%) a capillary leakage, 1/66 (1.5%) and optic disk hemorrhage and 1/66 (1.5%) a macular bleeding. No significant association between retinal vasculature abnormalities and cerebrovascular events was detected mainly due to the low event rate.

CONCLUSIONS

Perioperative evaluation of cerebrovascular ischemia with noninvasive imaging of retinal vasculature is possible in most patients undergoing TAVI. More data is needed to evaluate the association of cerebrovascular events and retinal microvascular abnormalities during the procedure.

Miniaturized cardiopulmonary bypass in adult cardiac surgery: a clinical update

INTRODUCTION

Cardiopulmonary bypass has undoubtedly been the cornerstone in the rapid development of cardiac surgery, allowing even the performance of procedures beyond the scope of cardiothoracic surgery. Its use however, is associated with significant complications that arise from the mechanical effects of the circuit on circulating blood components as well as the contact of blood with non-endothelial surfaces. Miniature cardiopulmonary bypass systems have been developed in an attempt to minimize these complications. Areas covered: Herein clinical outcomes from the most recent studies in adult cardiac surgery are discussed. The main benefits of miniaturisation as well as potential areas of further application are described. Expert commentary: Data is critically appraised in the context of current guidelines. Finally the need for further basic science in addition to large multi-centre randomized controlled trial data is highlighted.

The scientific evidence of arterial line filtration in cardiopulmonary bypass

BACKGROUND

The indication for arterial line filtration (ALF) is to inhibit embolisation during cardiopulmonary bypass. Filtration methods have developed from depth filters to screen filters and from a stand-alone component to an integral part of the oxygenator. For many years, ALF has been a standard adopted by a majority of cardiac centres worldwide. The following review aims to summarize the available evidence in support for ALF and report on its current practice in Europe.

METHOD

The principles and application of ALF in Europe was investigated using a survey conducted in 2014. The scientific evidence for ALF was examined by performing a systematic literature search in six different databases, using the following search terms: "Cardiopulmonary bypass AND filters AND arterial". The primary endpoint was protection against cerebral injury verified by the degree of cerebral embolisation or cognitive tests. The secondary endpoint was improvement of the clinical outcome verified elsewise. Only randomised clinical trials were considered.

RESULTS

The response rate was 31% (n=112). The great majority (88.5%) of respondents were using ALF, following more than 10 years of experience. Integrated arterial filtration was used by 55%. Of respondents not using ALF, fifty-four percent considered starting using integrated arterial filtration. The systematic literature database search returned 180 unique publications where 82 were specifically addressing ALF in cardiopulmonary bypass. Only four out of the 82 identified publications fulfilled our inclusion criteria. Of these, three were more than 20 years old and based on the use of bubble oxygenation.

CONCLUSION

ALF is a standard implemented in a majority of cardiopulmonary bypass procedures in Europe. The level of scientific evidence available in support of current arterial line filtration methods in cardiopulmonary bypass is, however, poor. Large, well-designed, randomised trials are warranted.

What We have Learned about Minimized Extracorporeal Circulation versus Conventional Extracorporeal Circulation: An Updated Meta-Analysis

Introduction

The benefits of minimized extracorporeal circulation (MECC) compared with conventional extracorporeal circulation (CECC) are still in debate.

Methods

PubMed, EMBASE and the Cochrane Library were searched until November 10, 2014. After quality assessment, we chose a fixed-effects model when the trials showed low heterogeneity, otherwise a random-effects model was used. We performed univariate meta-regression and sensitivity analysis to search for the potential sources of heterogeneity. Cumulative meta-analysis was performed to access the evolution of outcome over time.

Results

41 RCTs enrolling 3744 patients were included after independent article review by 2 authors. MECC significantly reduced atrial fibrillation (RR, 0.76; 95% CI, 0.66 to 0.89; P<0.001; I2 = 0%), and myocardial infarction (RR, 0.43; 95% CI, 0.26 to 0.71; P = 0.001; I2 = 0%). In addition, the results regarding chest tube drainage, transfusion rate, blood loss, red blood cell transfusion volume, and platelet count favored MECC as well.

Conclusions

MECC diminished morbidity of cardiovascular complications postoperatively, conserved blood cells, and reduced allogeneic blood transfusion.

Comparison of the use of minimized cardiopulmonary bypass with conventional techniques on the incidence of retinal microemboli during aortic valve replacement surgery

OBJECTIVES

Minimized cardiopulmonary bypass (MCPB) circuits have been shown to reduce cerebral and retinal microembolisation during coronary artery bypass graft (CABG) surgery compared to conventional CPB (CCPB) circuits. Our aim was to evaluate whether the reduction of microembolisation is sustained in aortic valve surgery, as well as to evaluate the effects of MCPB on inflammatory, endothelial, and platelet activation markers.

MATERIAL AND METHODS

Patients were randomized to undergo aortic valve replacement (AVR), with or without CABG, with MPCB (n=20) or CCPB (n=20). After anaesthesia induction and termination of CPB, standardized digital retinal fluorescein angiography images were obtained on both eyes and analyzed in a blinded fashion. Blood samples were collected at eight time points until the third postoperative day.

RESULTS

Fewer patients in the MCPB group showed evidence of microembolic perfusion defects on postperfusion retinal fluorescein angiographs compared to the CCPB group (37% vs. 63%, absolute difference 26%, 95% CI -5% -51%, P = 0.194). Polymorphonuclear leukocyte (PMN) elastase and von Willebrand factor release were statistically significantly reduced in the MCPB group, but there were no significant differences in other markers of inflammation, coagulation or endothelial activation. A significantly higher three-fold increase in the amount of shed blood was collected to the cell saver with a higher rate of intraoperative platelet transfusion in the MCPB group compared to CCPB.

CONCLUSIONS

The use of MCPB was associated statistically insignificantly with less retinal microemboli compared to CCPB. MCPB was complicated by excess bleeding and need for transfusion. The feasibility of MCPB techniques in valve surgery requires further studies.