Anastomotic devices - what do we need?

By Ulrich Hake, MD, PhD

The cardiosurgical - to be more precise the coronary surgical - world is now confronted with the latest technological innovation - the proximal and the distal anastomotic device.

The principal indication until now to use a proximal anastomotic device is beating heart surgery for those cases where venous grafts are required - and the vein has to cooperate by demonstrating sufficient diameter and adequate quality. One of the rationales behind beating heart is reduction of cerebral embolism and everybody will understand that it is irrational to perform a perfect off-pump procedure only to risk cerebral athero-embolism in the last moment by using a side-biter for the proximals. If you do it on-pump, however, there is virtually no need to use an anastomotic device since all anastomoses can be easily performed during one period of aortic X-clamping.

Whereas proximal anastomotic devices already represent a technical challenge similar to man's trip into orbit, distal anastomotic devices are even more sophisticated and can be compared to a precise landing on the moon.

As for the distals, until now only a tricky system of ferro-magnetic rings is available on the market. This system requires a controlled incision in the coronary artery and precise snap-in lock of the two magnets - or you will fail your landing site on the lunar surface. There are other devices in clinical trials where you either insert a PTFE-T-tube or put an umbrella-configurated connector into the anastomosis. All this looks good and works for the majority of implantations very smoothly - the question is how long will they last.

One of the eternal principles engineers seem to stick to is that whenever they have to connect one soft-tissue small-diameter tube with a second one -be it small or large - they are forced to put a strut-like element in-between. This element - the so-called connector or clip - shall both keep the anastomosis mechanically open and is at the same time the only fixation between the two vessels. To implant a metallic ring into the orifice of the proximal anastomosis may be without consequence, especially if the connector has a "large" diameter of about 4mm and is externally located without any contact to the blood surface. With respect to the distal device, however, one would appreciate something that is not stiff and, of course, not located within the anastomosis - the more the surgically everted suture is imitated the more success will be attained by a distal anastomotic device.

While an indication to use a proximal anastomotic device can be rationally derived already, at the present it is difficult to justify any clinical indication for a distal anastomotic device. Any innovation should be directed towards a problem and aim to facilitate a solution. To use a distal anastomotic device for the LAD - IMA anastomosis in off-pump surgery is hardly justified - problems here are mainly caused by an intramural LAD or by diffuse sclerosis and are therefore suture-independent. Moreover, one must clearly recognize the risk of possibly jeopardizing a high-quality mammary artery system by implanting a tubular stiff metal connector within the circulation. Difficulties with the circumflex or posterior descending system in off-pump surgery are usually associated with wrong indications or mismanagement of hemodynamics resulting in inadequate exposure and/or consecutive mistakes. To use a distal anastomotic device for the circumflex/PDA region may be justified to quickly correct these specific situations - always remembering the distal connector is not a life jacket.

An additional problem is that the construction design of most current devices requires that they be used only in patients with the best quality grafts and a good distal outflow. In other words, we might - very carefully expressed- add an unnecessary risk factor to an otherwise low-risk procedure only in order to pursue a future novel therapeutic approach.

Now, as we increasingly turn to non-robotic endoscopic coronary surgery, distal anastomotic devices become a "must". Then, however, the argument that the use of a distal device with a strut -stent-ring-like construction in today's off-pump or even in the on-pump patient, is only an interim step is somewhat ethically debatable, and places patients in the the role of test subjects. Until now data demonstrating more than short-term patency are limited, and I certainly hope that we will not have a large number of patients who experience distal anastomotic problems.

I consider myself to be more than open-minded towards innovation in cardiac surgery - but the indication for any innovative device must be rational and clearly defined. I personally believe that coronary surgery will move towards sternal sparing operations and functional revascularisation, sometimes combined with interventional approaches. This is especially realistic if you monitor the changes in demography and morbidity that we have encountered in our patients during the last decade. The more differentiated surgical concepts become the more will it become mandatory to scrutinize therapies in order to establish the appropriate strategy for the individual patient. As for the distal anastomotic device I know that they have arrived and indications are already defined today. I venture to predict that only developments that adopt surgical principles and surgical thinking will ultimately have success. These principles include easy loading and easy access to target areas, and, with special reference to the distals, avoidance of a strut-ring-like construct within the anastomosis as well as the option to modify the anastomosis according to coronary pathology.