Chronic ultrastructural effects of temporary intraluminal shunts in a porcine off-pump model

Clinical validation of coronary artery flow through an intracoronary shunt during off-pump coronary artery bypass grafting

OBJECTIVES

Intracoronary shunts have been developed for a bloodless field and preserved forward flow preventing ischemia during off-pump coronary artery bypass (OPCAB) surgery. However, reports directly measuring the forward flow through the shunt in clinical settings are lacking.

METHODS

Using a 7.5-MHz Doppler probe, we investigated the coronary flow through a 1.5-mm shunt inserted into the left anterior descending artery (LAD) for anastomosis with the internal thoracic artery during OPCAB in 30 consecutive patients. The following Doppler flow parameters were obtained before and after shunting: peak velocity, mean velocity, time-velocity integral, and flow.

RESULTS

No patients developed significant electrocardiographic changes and the peak value of postoperative myocardial band of creatine kinase was 17 ± 16 IU/L. All Doppler flow parameters of the LAD decreased significantly after shunting; peal velocity: 71.3 ± 34.6 cm/second to 54.5 ± 25.3 cm/second (-24% ± 27%), mean velocity: 33.3 ± 18.3 cm/second to 26.3 ± 14.0 cm/second (-21% ± 23%), and time-velocity integral: 28.7 ± 12.1 cm to 19.0 ± 7.1 cm (-28% ± 14%), and flow: 38.7 ± 16.8 mL/minute to 25.0 ± 9.5 mL/minute (-31% ± 13%) (P < .01).

CONCLUSIONS

The LAD flow is preserved at least 50% through a 1.5-mm intracoronary shunt, although the flow pattern was attenuated, during OPCAB anastomosis. The Doppler evaluation of the coronary artery flow before and after shunting is useful to justify the protective use of the shunt on myocardial perfusion during OPCAB.

Elective minimally invasive coronary artery bypass: shunt or tournique occlusion? Assessment of a protective role of perioperative left anterior descending shunting on myocardial damage. A prospective randomized study

Background

To determine impact of intraluminal-left anterior descending shunt to prevent myocardial damage in minimally invasive coronary artery bypass.

Methods

38 patients were randomly assigned to external tournique occlusion (n = 19) or intraluminal-left anterior descending shunt group (n = 19). Blood samples for cardiac troponin T were collected at 30 minutes prior to, 6 and 24 hours after surgery.

Results

One patient in external tournique occlusion and two patients in intraluminal-left anterior descending shunt group were excluded from futher analysis due to preoperative cardiac troponin T level above the 99th-percentile. Postoperatively, each six patients in external tournique occlusion (33.3%) and intraluminal-left anterior descending shunt (35.3%) group were above the 99th-percentile. Two patients from each group (external tournique occlusion group 11.1% vs. intraluminal-left anterior descending shunt group 11.8%) had peak values above 10-% coeficient of variation cutoff (p = 1). There were no significant differences in between both groups at all studied timepoints.

Conclusion

There was no protective effect of intraluminal shunting on myocardial damage compared to short-term tournique occlusion. It is upon the surgeon's discretion which method may preferrably be used to achieve a bloodless field in grafting of the non-occluded left anterior descending in minimally invasive coronary artery bypass.

Safe introduction and quality control of new methods in coronary surgery

Introduction:

The first part of the paper analyses off pump coronary bypass surgery (OPCAB), which is compared with traditional on-pump procedures (ONCAB). Furthermore ,the paper evaluates the use of a new automatic device for performance of the proximal anastomosis and finally the effect of intracoronary shunt on myocardial ischemia during OPCAB. The main goal of the paper is to demonstrate the importance of careful clinical studies during introduction of the new techniques in cardiac surgery.

Methods:

Statistical analysis was performed on a large clinical database from Buffalo, NY, USA comparing OPCAB and ONCAB. Subsequently, a sequential controlled clinical study compared patients operated with a new automatic connector device to patients operated with classic suture technique. Finally a randomized study was performed to evaluate the effect of the use of an intracoronary shunt during construction of distal anastomosis.

Results:

The studies from Buffalo demonstrated reduced complications rates in high risk patients when OPCAB techniques were used. The use of connector devices in saphenous venous anastomosis was clearly inferior to standard technique. Intracoronary shunt was found to be beneficial by preventing ischemia.

Discussion:

Numerous studies have studied the results of OPCAB vs ONCAB and although results are variable it seems that OPCAB is advantageous in high risk patients, while in low risk patients there are much less if any benefit. The results of the studies of connector devices caused the product to be taken off the market. The value of shunt in OPCAB was clearly demonstrated by the randomized studies.

Conclusion:

The investigations presented in this paper clearly demonstrates the importance of well-designed studies when new surgical methods are introduced. In the present period of rapid technological development, carefully controlled, un-biased clinical trials are crucial to preserve patient safety and avoid unjustified societal cost.

Intracoronary shunt versus bulldog clamp in off-pump bypass surgery. Endothelial trauma: shunt versus clamp

BACKGROUND

During off-pump coronary bypass grafting, local vascular control of the target vessel and a bloodless field are crucial. The aim of this study is to asses the histopathological outcomes of intracoronary shunts and bulldog clamping on the beating heart in a canine model.

METHODS

Twelve healthy adult mongrel dogs weighing between 15 to 25 kg were included in the study. Following left thoracotomy, proximal left anterior descending artery segment 1 cm to distal of diagonal branch was marked. Arteriotomy at this site was performed and a shunt was inserted for 10 min in the shunt group. The bulldog clamp was applied 3 cm distal to the mark for 10 min after heparinization in the bulldog group. Thirty days after the procedure, the specimens of left anterior descending artery from both regions were collected and were examined. Vascular damage, presence of intimal hyperplasia, and denudation were noted.

RESULTS

Only intimal denudation was found significantly higher in the shunt group (P < 0.05). In this group, only one case had grade 0 endothelial damage. In the bulldog group, all cases had endothelial damage of various grades.

CONCLUSION

The proven advantages of temporary intracoronary shunts are well-known, e.g., preserving the ventricular functions. Despite these advantages, our study revealed an ultimate bad result for an off-pump coronary by pass patient: intimal denudation. We conclude that further studies with a larger number of subjects are needed to decide whether routine shunt insertion into coronary arteries during off-pump coronary bypass surgery is appropriate or not.

Controversies in the Use of Intraluminal Shunts During Off-Pump Coronary Artery Bypass Grafting Surgery

Technical advances have made the performance of multivessel off-pump coronary artery bypass feasible. Snaring and intraluminal shunts are the techniques used for vascular control. Snaring provides a bloodless surgical field, is usually well tolerated by the patient, and is supported by years of clinical experience. Intraluminal shunts aim to achieve hemostasis at the arteriotomy site and to allow antegrade flow to provide myocardial protection. There are unresolved issues regarding whether shunts have a clinical benefit, do provide adequate flow to provide myocardial protection, and whether they cause significant endothelial damage. In this article, we have reviewed the literature to lend perspective to these issues.

Simple On-Site Assembled Blower-Mister Device Provides Sufficient Humidification and Visualization in Off-Pump Surgery

To effectively perform an anastomosis on a coronary artery under beating heart conditions, the anastomotic site must be cleared of blood to allow visualization for accurate suturing. We describe a simple, cost effective, on-site assembled blower-mister system.