Effects on coronary endothelial function of the Cohn stabilizer for beating heart bypass operations

Temporary coronary artery occlusion during off-pump coronary artery bypass grafting with the new poloxamer P407 does not cause endothelial dysfunction in epicardial coronary arteries

OBJECTIVE

The aim of this study was to assess the efficacy of the novel reversible thermosensitive gel poloxamer 407 for occlusion of the coronary vessel necessary for minimally invasive operations and its effects on coronary endothelium.

METHODS

Domestic swine were submitted to occlusion of the left anterior descending or right coronary artery using the poloxamer. The left and right internal thoracic arteries were used as grafts to perform coronary artery bypasses. Animals were humanely killed after 3 hours of perfusion (acute; n = 8) or 3 days (subacute; n = 6). The vascular reactivity of coronary artery was evaluated in response to serotonin and bradykinin. Histologic studies were performed to analyze cardiomyocyte necrosis and endothelial coverage.

RESULTS

The gel led to an occlusion of 7.8 +/- 2.2 minutes. Concentration-response curves of occluded coronary segments showed no difference of endothelium-dependent relaxations in both operated groups (P < .05 vs control). Histologic studies demonstrated the absence of cardiomyocyte necrosis after coronary artery occlusion in the acute group; a small infarct zone was detected in 1 animal in the subacute group, resulting from an occlusion of the first diagonal branch. The endothelial layer coverage was preserved in both groups.

CONCLUSION

The poloxamer 407 represents a promising technique for obtaining hemostasis at the site of anastomosis during construction of bypasses during beating heart coronary artery surgery, without damage to the endothelium or ischemic consequence.

Intracoronary Shunt-Induced Endothelial Cell Damage in Porcine Heart

BACKGROUND

Injury to and dysfunction of the endothelium can compromise the patency of coronary arteries and lead to impaired perfusion of the heart. Such injury can occur after the application of an intravascular shunt and/or a snare to a coronary artery during bypass surgery. In this study, multiphoton microscopy was used to assess the integrity of endothelium in porcine coronary arteries subjected to shunting and snaring during off-pump coronary artery bypass grafting (OPCAB).

MATERIALS AND METHODS

In open chest porcine, the left anterior descending artery was manipulated in different regions using snare and shunt to simulate OPCAB. Sections of left anterior descending artery were labeled with fluorescent dyes to evaluate the viability of the endothelium. The structural integrity of the endothelium was evaluated by calcein- and ethidium homodimer-mediated fluorescence. Endothelial functional viability was assessed by measuring cellular esterase activity, calcium mobilization, and endothelial nitric oxide synthase-mediated generation of nitric oxide using fluorescence dyes and multiphoton microscopy.

RESULTS

Substantial endothelial damage was observed in shunted region of the coronary arteries. In contrast, endothelium remained structurally viable in regions that were snared, similar to control regions of the coronary arteries that were not manipulated. Esterase activity, calcium mobilization, and nitric oxide generation was greater in the control and snared regions of the coronary arteries in comparison to the shunted region.

CONCLUSIONS

The use of intracoronary shunts led to structural damage and attenuation of endothelial function in porcine coronary arteries, whereas snared vessels maintained their viability and integrity, similar to the control sections. The routine use of shunts in OPCABG may lead to endothelial damage and possibly to long-term graft failure.

Novadaq SPY: intraoperative quality assessment in off-pump coronary artery bypass grafting

OBJECTIVES

Off-pump coronary artery bypass grafting may decrease operative morbidity when compared to on-pump bypass grafting; however, it is technically demanding and thus quality control is essential. This study assesses the clinical feasibility of a new, indocyanine green (ICG)-based imaging system (SPY; Novadaq Technologies; Toronto, ON, Canada) to monitor the quality of anastomoses and grafts in off-pump revascularization.

SETTING

Thirty-eight consecutive patients undergoing nonemergent coronary artery bypass grafting without the use of extracorporeal circulation at two Swiss cardiac surgery clinics were included. On completion of bypass grafts, the quality of the grafts was assessed using the ICG-based imaging system. The imaging device comprises an 806-nm laser light source that is used to cause ICG to fluoresce and a near infrared-sensitive charged couple device videocamera that is used to capture the fluorescence images. ICG was administered through the central venous line, and images were acquired during the first pass of the ICG through the field of view. Graft flow (qualitative) and the quality of the grafts and anastomoses were assessed intraoperatively.

RESULTS

Between March 2002 and September 2002, a total of 38 patients (26 men and 12 women; mean +/- SD age, 64.6 +/- 10.5 years; body mass index, 27.1 +/- 2.9) underwent surgery and imaging at two institutions. One hundred seven of 124 grafts (45 arteries and 62 veins) were analyzed. Seventeen grafts could not be assessed due to difficulties in positioning. The imaging system was easy to handle, and no adverse reactions to ICG were observed. Four of the 107 grafts imaged required revision (three anastomotic constrictions and one graft dissection). Each imaging sequence required approximately 1.25 to 2.5 mg of ICG. The images were equivalent to angiography without the need for radiographs and catheter insertion. In addition, the course of coronaries that would otherwise be difficult to locate in obese patients could be detected using the imaging system. Biochemical and ECG data demonstrated an absence of intraoperative or postoperative myocardial damage, and no liver enzyme elevation or renal dysfunction.

CONCLUSIONS

This study supports the clinical utility of a ICG-based imaging system for the assessment of the quality of bypass grafts, which appears to be safe and simple to use.

Heparin versus danaparoid in off-pump coronary bypass grafting: results of a prospective randomized clinical trial

OBJECTIVE

The incidence of heparin-induced thrombocytopenia is increasing, and the thrombin inhibitor danaparoid could be a useful alternative. The objective of the present study was to compare danaparoid and heparin in patients undergoing off-pump coronary artery bypass grafting.

METHODS

In a prospective, randomized, double-blind clinical trial comparing heparin (bolus of 1 mg/kg) with danaparoid (bolus of 40 U/kg), 71 patients underwent off-pump coronary artery bypass grafting with one of the study drugs. The amount of blood lost, the number of homologous blood products transfused, the troponin T levels, and the amount of anti-Xa activity were monitored.

RESULTS

Thirty-four patients underwent 2.6 +/- 0.7 bypasses with danaparoid, and 37 patients underwent 2.5 +/- 0.9 grafts with heparin (P =.8). Postoperative blood losses averaged 1394 +/- 1033 mL in patients receiving danaparoid and 1130 +/- 868 mL in patients receiving heparin (P =.2). The number of homologous blood products transfused averaged 3.6 +/- 7 units in patients receiving danaparoid and 1.9 +/- 4.4 units in patients receiving heparin (P =.2). The number of patients requiring homologous blood transfusion was higher in patients receiving danaparoid (18/34 [53%]) than in patients receiving heparin (10/37 [27%], P =.03). Serum anti-Xa activity averaged 1.6 +/- 0.6 U/mL in patients receiving danaparoid and 1.9 +/- 0.8 U/mL in patients receiving heparin 30 minutes after injection of the drugs (P =.1) and 0.3 +/- 0.1 and 0.04 +/- 0.08 U/mL, respectively, 12 hours after coronary artery bypass grafting (P =.001). Troponin serum levels were similar 48 hours after coronary artery bypass grafting (0.5 +/- 0.6 and 0.4 +/- 0.6 microg/L, respectively).

CONCLUSION

Although off-pump coronary artery bypass grafting with danaparoid versus heparin increases the number of patients exposed to homologous blood transfusion (relative risk, 2; 95% confidence limits, 1-4), off-pump coronary artery bypass grafting with danaparoid is a valuable alternative to heparin in patients with thrombocytopenia requiring surgical intervention.

Future technology for off-pump coronary artery bypass (OPCAB)

Over the past 5 years, many coronary artery surgeons have embraced technology and advanced the field of beating heart surgery to the point where off-pump coronary artery bypass (OPCAB) is becoming a mature procedure. Enabling technologies are now available for all stages of the procedure, including cardiac positioning, coronary artery stabilization, coronary artery visualization, and performance of the proximal and distal anastomoses. Despite these successes, only a minority of cardiac surgeons performs this procedure routinely. Proponents of OPCAB and the medical device industry will need to continue to develop new technologies to make OPCAB less technically challenging and more widely accepted. Progress towards routine single-vessel off-pump totally endoscopic coronary artery bypass has been slow. Translating the benefits of multivessel OPCAB to an endoscopic setting remains a formidable challenge that will require further technologic breakthroughs.

Robotically assisted versus conventional freehand technique during beating heart anastomoses of left internal thoracic artery to left anterior descending artery

BACKGROUND

Although robotically assisted coronary arterial anastomoses are being performed clinically, the short-term and long-term quality and integrity of the left internal thoracic artery (LITA) to left anterior descending artery (LAD) anastomosis remains unknown. The goal of this study was to perform a histologic and angiographic assessment of porcine beating heart LITA to LAD anastomoses using either robotic assistance or a conventional freehand technique.

METHODS

Twelve pigs underwent beating heart LITA to LAD anastomoses using either the robotically assisted (n = 6) or conventional freehand techniques (n = 6). Quantitative histologic analysis was performed in all animals in order to determine the degree of vascular wall damage. Selective coronary arteriography was performed in all animals immediately after the procedure in order to evaluate anastomotic patency. The unpaired Student's t test was used for all comparisons between groups.

RESULTS

There were no differences in vascular wall damage between the robotically assisted and freehand techniques. Postoperative angiography revealed no stenoses in either group.

CONCLUSIONS

Use of the robotically assisted technique for creation of a LITA to LAD anastomosis was not associated with increased histologic damage when compared with the freehand technique in a beating heart porcine model. Furthermore, there was no difference between the two techniques in postoperative patency rate. These results support further clinical investigation of robotically assisted coronary bypass surgery.

A new intracardiac microaxial pump: first results of a multicenter study

As coronary artery bypass grafting (CABG) surgery in the beating heart technique is progressing, new devices have been developed to overcome hemodynamic instabilities while tilting the heart for exposure of back wall vessels. A new device for in heart biventricular intracorporeal circulation was applied in 42 patients undergoing CABG surgery (Group 1). The control group consisted of 38 patients operated on using a conventional cardiopulmonary bypass setup (Group 2). The study protocol of the prospective, randomized multicenter study was approved by the local ethics committees. Patients were included following inclusion criteria and patient informed consent. Mean age, procedure time, mean arterial pressure (MAP), and hemolysis by means of plasma free hemoglobin (fHb) were assessed preoperatively, perioperatively, on postoperative Days 1 to 3, at discharge, and at a 3 month follow-up. The mean age was 62.1 (range 59-74) years (Group 1), 62.7 (range 48-72) years (Group 2); procedure time was 112 min +/- 31.9 min (Group 1), 137.4 min +/- 36.2 min (Group 2); and 2.3 +/- 0.6 (Group 1), 2.2 +/- 0.7 (Group 2), vessels were revascularized. The flow on pump was 3.7 (2.5/4.4) L/min (Group 1), 4.9 (3.6/6.2) L/min (Group 2) which resulted in a MAP of 69.8 (4.0/143) mm Hg (Group 1), 58.3 (5.3/94) mm Hg while assessing the vessels of the back wall. Hemolysis defined by fHB was lower than 20 mg/dl at all times pre- and postoperatively. Intraoperative maximum values were up to 100 mg/dl in 4 patients (2 in Group 1 and 2 in Group 2). Body mass index was 26.4 +/- 2.6 (Group 1), 27.9 +/- 3.2. New York Heart Association Class was II to III in both groups. There were no pump related life threatening or severe adverse events. Beating heart procedures with ICC can be reliably and safely achieved. As the device is easy to use, it may deserve a more widespread use in the future.