Ann Thorac Surg 1999;68:263-264
© 1999 The Society of Thoracic Surgeons
How to Do It
Intraoperative detection of embedded coronary arteries in MIDCAB using a color Doppler microprobe
Katsushi Oda, MDa,
Kunihiko Hirose, MDa,
Takashi Fukutomi, MDa,
Toshiyuki Yamashiro, MDa,
Shohei Ogoshi, MD, PhDa
a Department of Surgery II, Kochi Medical School, Kochi, Japan
Address reprint requests to Dr Oda, Department of Surgery II, Kochi Medical School, Kohasu Oko, Nankoku, Kochi, 783-8505, Japan;
e-mail: odak{at}kochi-ms.ac.jp
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Abstract
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Intraoperative detection of deeply embedded coronary arteries is difficult, especially in minimally invasive coronary artery bypass grafts. This report describes an effective method to identify embedded coronary arteries by using a color Doppler microprobe. Five embedded left anterior descending coronary arteries were successfully identified by intraoperative ultrasonography. We believe that the color Doppler microprobe is helpful for surgeons in this difficult situation.
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Introduction
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In coronary artery bypass grafts (CABG), one of the most difficult procedures is to identify and locate the coronary artery when it is deeply embedded in the fat tissue or myocardium. In minimally invasive direct coronary artery bypass grafts (MIDCAB), it is particularly difficult to locate deeply embedded coronary arteries due to a confined operation field. Therefore the intramuscular course of the left anterior descending artery (LAD) shows contraindications for MIDCAB at present [1]. In this study, we demonstrated the usefulness of a color Doppler microprobe (CDM) for detecting deeply embedded LAD in MIDCAB.
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Material and methods
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The ultrasound unit (SSD-200, Aloka, Tokyo, Japan) used in this study is equipped with a specially designed CDM. The CDM is a long handle that is in the shape of a crankshaft. The tip of the CDM is 3.5 mm in height, 3.5 mm in width, and 13 mm in length. Although the signal-sending surface is small, B-mode, M-mode, pulsed Doppler and color Doppler capabilities are available. The transducer frequency is 7.5 MHz and the transducer is of a linear array type. When the course of the coronary artery was not apparent by inspecting the surface anatomy or by palpation, intraoperative ultrasonography (IOUS) was performed to identify the exact location of the LAD. A stabilizer was used to reduce cardiac motion, thus providing better visualization. The CDM was placed directly on the surface of the heart (Fig 1 ). The LAD was then examined by color Doppler mapping.
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Results
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IOUS was performed on 5 patients who underwent MIDCAB. IOUS revealed that the LAD was embedded in the myocardium in 3 patients and in thick fat tissue in 2. All cases but 1 were successfully operated upon using MIDCAB. The location of the LAD were confirmed by identifying the septal branches using color Doppler imaging (Fig 2 ). IOUS acted as an accurate guide to the location of the LAD, which were found directly beneath the probe, allowing easy dissection. The small width of the CDM allowed for easier identification and provided the exact location of the LAD. Minimal dissection of the coronary artery was achieved and it was particularly effective in MIDCAB, because visual detection of the coronary artery is restricted. In 1 case, we could not perform MIDCAB because the LAD was too deeply embedded in the myocardium. Although it could be clearly detected by IOUS (Fig 3 ), the risks were considered too high to dissect such a deeply embedded coronary artery on a beating heart.
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Fig 2. Left; Color Doppler image of the LAD showing a septal branch coming out from the LAD. Right; a schematic drawing
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Fig 3. Left; Color Doppler image of an ungraftable LAD. After dissection of overriding fat tissue, it was still embedded deeply in the myocardium. Right; a schematic drawing
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Comment
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We introduced CDM for assessing ITA grafting during operations in 1996 [2]. In this study, we applied the CDM for detecting LAD which were deeply embedded in fat tissue or the myocardium. Although it is possible to use to assess a coronary artery on the surface of the heart, it is much more effective for detecting a coronary artery embedded in fat tissue or the myocardium.
We have examined coronary arteries in 50 cases using IOUS. Ultrasonography always needs practice to obtain a stable image. After examination of 10 to 15 cases, it became a reliable method to assess coronary arteries. All coronary arteries including LAD, LCX and RCA were successfully examined.
Compared to the conventional probe, the CDM is surprisingly small in size. The characteristics of the CDM make it useful for detecting embedded coronary arteries in MIDCAB. There are several studies about the usefulness of ultrasonography in assessing the coronary artery during CABG [3–6]. However, in those studies, the probes were much larger than the CDM, and therefore, location of the LAD was relatively imprecise. As a result, the large probe was considered inappropriate in MIDCAB and its usefulness significantly reduced. The capability of color Doppler image is another advantage of the CDM. Clear color Doppler image was obtained on a beating heart and it was effective to identify coronary arteries. The LAD is easily identified by confirming septal branches. We believe that the CDM will be a useful tool in detecting embedded coronary arteries in MIDCAB.
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Acknowledgments
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We gratefully acknowledge the assistance of Tomotaka Takeshima in performing the ultrasonographic examinations.
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References
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Accepted for publication January 28, 1999.
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Abstract
Introduction
