Endoscopic Doppler for Detecting Vessels in Closed Chest Bypass Grafting

(#2000-93443 ... June 24, 2000)

Volkmar Falk, MD,¹, James I. Fann, MD, ² Jürg Grünenfelder, MD, ¹ Thomas A. Burdon, MD,²

¹ Department of Cardiothoracic Surgery, Stanford University Medical Center, Stanford, California
² Section of Cardiothoracic Surgery, VA Palo Alto HCS, Palo Alto, California

ABSTRACT

A new method of endoscopic ultrasonography during endoscopic bypass grafting is described. Using a 7.5 MHz ultrasonic catheter (AcuNav, Acuson, Mountain View, CA) that was introduced through a 5mm port and manipulated by robotically enhanced endoscopic instruments, detection of the internal thoracic artery (ITA) and the left anterior descending (LAD) artery was possible through layers of fat and muscle in a canine model.

AUTHOR/ARTICLE INFORMATION

Address correspondence and reprint to: Volkmar Falk, MD, Department of Cardiac Surgery, University of Leipzig, Heartcenter, Russenstr. 19 04289 Leipzig, Germany, Phone: 01149-341-865-1421, Fax: 01149-341-1452, Email: falv@medizin.uni-leipzig.de

REVIEW AND COMMENTARY

1. Editorial Board Member AR11 writes:

This is an inevitable progression in the development of closed chest bypass surgery, making use of all types of instrumentation. While the authors apparently can use the Doppler probe to facilitate the procedure, their presentation is muddled. As indicated by the authors, the dog is not a particularly good model as the vessels are epicardial and easy to spot. Perhaps if the experimental demonstration were repeated in another species, e.g., a series of pigs or sheep, the results might be more readily accepted.

Authors' Response by Volkmar Falk, MD:

It was not the purpose of this communication to present a large body of data, but to demonstrate the possible application of a technique that has been shown useful in conventional surgery in an endoscopic environment. We will continue using a similar device in a human trial soon. This trial will answer the important question if the probe will be sensitive enough to help localize stenoses, calcified areas, and healthy parts of the native coronary circulation.

Both in pigs, as well as in sheep, the coronaries are equally superficial. It is only in humans that the coronary may be covered by fat or run intramyocardial. To prove the concept, the dog model was suitable as it could be shown that endoscopic detection of vessels is possible under layers of muscle and fat.

2. Editorial Board Member EE455 writes:

This may be a key technique to enable later routine endoscopic coronary artery bypass grafting (CABG). The authors should provide more practical insights about the technique's interpretation and feasability.

a) Is the signal easily sampled and identified? Are there artifacts?

b) Can the probe be bent, and if not, is it technically feasible in the future? (As far as Figure 1 [see Figure 1 :104:] shows, the course of the LITA is very tangential to the probes tip and might in some cases be out of its reach, unless the probe is flexible).

c) Did the technique provide information about graft patency? (This being evoked as an option in the Introduction.)

Authors' Response by Volkmar Falk, MD:

a) Sampling of the image is readily achieved. The small diameter of the target vessels require a high frequency which naturally limits the depth. Artifacts could potentially come from blood flow inside the ventricle, but the combination of 2D-imaging, color flow Doppler, and CW Doppler allows correct interpretation of the signal.

b) The probe used is built for transvascular intracardiac use and is infact bendable, using the tools of the telemanipulation system. The design of a probe that would be made for endoscopic use would of course have a somewhat different design with a more flat transducer.

c) In this case, the anastomosis was not performed and graft patency was therefore not tested using the probe. Patency of grafts has been tested in other studies using similar technology (see references).

3. Editorial Board Member PB44 writes:

What might the cost implications be for this device?

Authors' Response by Volkmar Falk, MD:

The Doppler probe used for this study was a disposable probe made for transvascular intracardiac use. The price of these devices (greater than $1,500 US-Dollar) is prohibitive for a routine endoscopic application in a procedure that is already expensive. Reusable probes will therefore be required in the future.