Ann Thorac Surg 2006;81:322-326
© 2006 The Society of Thoracic Surgeons
New technology
Ultrasound Mini-Transducer with Malleable Handle for Coronary Artery Surgery
Ricardo P.J. Budde, PhD,
Patricia F. A. Bakker, MD, PhD
*
,
Rudy Meijer,
Cornelius Borst, MD, PhD,
Paul F. Gründeman, MD, PhD
Heart Lung Center Utrecht, University Medical Center Utrecht, Utrecht, the Netherlands
Accepted for publication June 22, 2005.
* Address correspondence to Dr Bakker, Department of Cardiothoracic Surgery, Heart Lung Center Utrecht, University Medical Center Utrecht, Room E 03.406, Heidelberglaan 100, Utrecht, 3584 CX the Netherlands (Email: utrecht.cardioresearch{at}hli.azu.nl).
 |
Abstract
|
|---|
PURPOSE: A 13 MHz epicardial ultrasound mini-transducer (15 x 9 x 6 mm) with a custom made malleable handling tool was evaluated to assess the coronary artery and anastomosis on all sides of the heart.
DESCRIPTION: On indication, in 8 patients undergoing coronary artery bypass surgery on the arrested heart, 8 coronary arteries as well as 27 coronary anastomoses were scanned.
EVALUATION: The malleable handle was easily adjusted, and all sides of the heart were accessible for scanning with the mini-transducer. Based on intraoperative scanning, the anastomotic site was altered (n = 4), an additional coronary artery was grafted (n = 2), and the left anterior descending coronary artery was identified after incorrect conventional selection of the diagonal branch (n = 1). No anastomosis construction errors were detected. In one anastomosis, a calcified plaque was seen in the outflow corner.
CONCLUSIONS: The epicardial ultrasound mini-transducer with its malleable handle allowed successful visualization and assessment of the coronary arteries and anastomoses on all sides of the heart. Ultrasound information greatly aided in intraoperative decision making that resulted in anastomotic site changes and prevented grafting of the wrong vessel.
|
Introduction
|
|---|
In coronary artery bypass grafting, epicardial ultrasound enables intraoperative assessment of the coronary artery and anastomosis [1–8]. Despite promising results on the anterior side of the heart, widespread adoption has been prevented by the inability to scan the lateral and posterior sides due to the bulky transducers at the time [1–3].
We previously described a high-frequency epicardial ultrasound mini-transducer for the assessment of coronary arteries and anastomoses on ex-vivo hearts [8], at all sides of the beating porcine heart [6, 7] and at the anterior side of the beating heart in patients [5].
|
Technology
|
|---|
A custom made handling tool was developed that can be bended into any desired shape to allow optimal access to any part of the heart. We evaluated this malleable handle with the mini-transducer to scan coronary arteries and anastomoses on all sides of the heart in patients undergoing coronary artery bypass grafting surgery.
|
Technique
|
|---|
Patients
Epicardial ultrasound scanning was performed upon indication in 8 patients undergoing coronary artery bypass grafting surgery. The target arteries and sites for grafting were determined on the preoperative coronary angiogram by the surgeon (PFAB). A median sternotomy approach, cardiopulmonary bypass, and antegrade and retrograde tepid blood cardioplegia were applied. The left internal mammary artery was used for grafting of the left anterior descending (LAD) coronary artery and diagonal branches. All other coronary arteries were grafted using the greater saphenous vein.
Ultrasound Equipment
A high-frequency (up to 13 MHz in B-mode) linear array epicardial ultrasound mini-transducer (15 x 9 x 6 mm) (UST-5531; Aloka, Tokyo, Japan) was used [6–8]. It has a 10-mm image scan width and offers B-mode and color Doppler imaging [6–8].
Two sternal wires were fixed to the mini-transducer by a custom made snap-on clip [6, 7] and were wrapped around its cable to act as a handling tool (Fig 1, top panel). By bending the wires, the probe handle could be adjusted to any desired shape for optimal access to each individual area to be scanned (Fig 1, bottom panels).
View larger version (113K):
[in this window]
[in a new window]
|
Fig 1. The 13 MHz mini-transducer with custom-made malleable probe handling tool. The probe is placed in a sterile probe cover for clinical use (not shown).
|
|
The mini-transducer was placed in a gel-filled sterile protective cover (Ultracover [International Medical Products, Inc, Zutphen, The Netherlands]) to act as a sterile and electrical barrier. Sterile ultrasound gel (Parker Laboratories, Fairfield, NJ) was applied directly onto the epicardial surface or anastomosis, or both, for improved visualization.
The ultrasound imaging system (SSD 5000 [Aloka, Tokyo, Japan]), was positioned at the head end of the operating table. The continuous scan image was recorded on videotape for retrospective time analysis.
Scanning was performed by a person (RPJB or RM) with experience in epicardial ultrasound scanning.
Indications for Scanning
In this series, indications for intraoperative scanning of the coronary artery prior to anastomosis construction (pre-scan) were as follows: decision making problems in optimal distal anastomotic site selection in diffuse coronary disease, discrepancies between preoperative angiographic and intraoperative findings, questions regarding the angiographic degree of stenosis and an intramural vessel course. Indications for anastomosis scanning included impaired visualization during suturing, poor vessel wall quality, small diameter vessels, and back bleeding during anastomosis construction.
Coronary Artery Pre-Scanning
Pre-scanning of the coronary arteries was performed prior to arteriotomy on the arrested heart during continuous retrograde blood cardioplegia. If severe calcifications or plaques were detected during scanning, another anastomotic site, free of disease and distal to the most severe stenosis, was selected by ultrasound. Additional anastomoses were constructed when an unexpected significant stenosis, in contrast with the angiographic findings, was observed during scanning.
Anastomosis Scanning
If there was an indication to perform a coronary pre-scan or scanning of an anastomosis (as previously explained), all anastomoses in that patient were scanned using a standard approach. First, vein graft anastomoses were scanned during continuous antegrade blood cardioplegia perfusion (80 to 100 mm Hg) of the vein graft before construction of the proximal anastomosis on the aorta. The left internal mammary artery-(diagonal)-LAD anastomosis was subsequently constructed and scanned on the arrested heart during cardiopulmonary bypass after removal of the left internal mammary artery bulldog clamp, and immediately prior to removal of the aortic cross-clamp.
|
Clinical Experience
|
|---|
Coronary Artery Pre-Scanning
See Table 1
for indications and results. Pre-scanning of eight coronary arteries in 5 patients required 196 seconds (median range, 57 to 375). Ultrasound findings affected the number of coronary artery anastomoses in 2 patients, and in 2 other patients the anastomotic site was changed (n = 4). In 1 patient, with parallel running intramural diagonal branches and LAD, ultrasound scanning revealed incorrect identification of a diagonal as a LAD. Echocardiographically, the LAD was identified by the underlying ventricular septum and septal perforators (Fig 2).
View larger version (138K):
[in this window]
[in a new window]
|
Fig 2. Longitudinal ultrasound image of the left anterior descending (LAD) coronary artery. Note the ventricular septum and the septal perforating branch (arrow).
|
|
Anastomosis Scanning
A total of 27 anastomoses, on all sides of the heart were successfully visualized in 150 seconds (median range, 54 to 335) (Figs 3, 4; 
Table 2). No damage to the anastomoses or probe cover leakage was observed.
View larger version (121K):
[in this window]
[in a new window]
|
Fig 4. Fully patent left internal mammary artery–left anterior descending coronary artery (LIMA-LAD) anastomosis with power Doppler imaging. Ultrasound shadowing was caused by a clip (arrow) on the LIMA side branch.
|
|
No anastomosis construction errors were detected. In one left internal mammary artery-diagonal-LAD jump graft, a large calcified plaque was detected in the outflow corner on the posterior LAD wall (Fig 5). It had not been observed on the preoperative angiogram nor was it intraoperatively detected, despite careful inspection and palpation. In this patient there was no indication for pre-scanning as the angiogram seemed easy to interpret. However, during anastomosis scanning, the LAD was visualized and several disease free sites were detected distal to the anastomosis. Transit-time measured flow was 23 mL/min for the LAD anastomosis alone and 44 mL/min for both anastomoses combined. The graft was accepted. In three other anastomoses without pre-scanning, small calcified plaques were observed.
View larger version (44K):
[in this window]
[in a new window]
|
Fig 5. Left internal mammary artery–left anterior descending coronary artery (LIMA-LAD) anastomosis. Left-hand panels: oblique longitudinal ultrasound image showing large calcified plaque in the outflow corner. Middle panels: transverse image at the level of the outflow corner. Right-hand panel: preoperative angiogram with the anastomotic site indicated (arrow).
|
|
|
Comment
|
|---|
The principal findings of this study are as follows: (1) the epicardial ultrasound mini-transducer with malleable handle enabled successful assessment of coronary arteries and anastomoses on all sides of the arrested heart, and (2) intraoperative scanning greatly aided in optimal anastomotic site selection and prevented grafting of the wrong vessel.
Access to the Lateral and Posterior Side of the Heart
In contrast to previous studies [1–4], the small size and custom-made malleable handling tool of the present mini-transducer enabled optimal visualization at all sides of the heart, including sections of and the anastomoses on the obtuse marginal branches located close to the base of the heart.
Anastomotic Site Selection
In a previous study of epicardial ultrasound scanning of the LAD on the beating heart [5], the anastomotic site was changed in 3 of 13 patients. In the present study when pre-scanning was performed on indication in patients on cardiopulmonary bypass, the anastomotic site was altered in four of eight arteries.
Pre-scanning revealed incorrect identification of a diagonal branch as the LAD in 1 patient. Grafting of the wrong vessel (diagonal instead of LAD) has been reported [9]. The underlying ventricular septum and septal perforating branches (Fig 2) may serve as distinctive echocardiographic landmarks for discrimination between the LAD and diagonal branches.
The detection of a large calcified plaque in the outflow corner of a left internal mammary artery-LAD anastomosis in a patient in which LAD pre-scanning was not performed further supports the routine use of epicardial ultrasound prior to the arteriotomy. It is conceivable that part of the anastomotic stenoses seen at postoperative angiography [10] are due to grafting at suboptimal anastomotic sites rather than to suture errors. A study in which intraoperative ultrasound scanning is combined with postoperative angiography may provide more insight into this matter.
We regard the 196 seconds (range, 57 to 375 seconds) of scanning time acceptable for routine use in relation to the diagnostic benefit.
Anastomosis Scanning
No construction errors were detected in 27 anastomoses (9 arterial and 18 vein grafts). Validation by postoperative angiography was not performed, but previous validation in the ex-vivo porcine and human heart showed that ultrasound detects construction errors with significant higher sensitivity (0.98) and specificity (1.00) than angiography (sensitivity 0.75; specificity 0.81) [8].
In one anastomosis, at first there was no flow seen in the anastomosis during power Doppler imaging. After repositioning of a retraction sling, power Doppler flow was detected. Conduit compression or kinking needs to be excluded if no power Doppler flow is observed in the anastomosis.
Scanning in General
For accurate interpretation of the ultrasound image, the ultrasound machine with the monitor needs to be placed as close as possible to the scanning person. Alternatively, the ultrasound image could be displayed on a monitor mounted on an articulating arm that can be positioned at the head end during scanning and put aside during the rest of the operation.
Use of Epicardial Ultrasound
In this study, epicardial ultrasound was used only on indication. However, the promising results combined with the changing coronary artery bypass grafting patient characteristics towards an elderly population with a high incidence of diffuse coronary artery disease, in our view supports more frequent intraoperative use of epicardial ultrasound in patients undergoing coronary artery bypass grafting surgery. Larger studies are needed to determine if routine use is beneficial to the patient.
Limitations
Scanning was performed on the arrested heart using antegrade and retrograde blood cardioplegia. Under these conditions it was quick and easy. Scanning on the stabilized beating heart may be more difficult due to motion artefacts. However, it seemed to be no problem for accurate visualization in previous animal [6, 7] and patient studies [3–5].
In conclusion, using an epicardial ultrasound mini-transducer with a malleable handle, coronary arteries, and anastomoses on all sides of the heart were successfully visualized and assessed. Epicardial ultrasound information aided in intraoperative decision making that resulted in changes of the anastomotic site and number of anastomoses and prevented grafting of the wrong vessel. The absence of anastomotic construction errors was demonstrated intraoperatively in all distal coronary anastomoses.
|
Disclosures and Freedom of Investigation
|
|---|
The ultrasound probe and imaging system used in the study were purchased using academic funds. The authors had full control of the design of the study, methods used, outcome measurements, analysis of data, and production of the written report.
|
Disclaimer
|
|---|
The Society of Thoracic Surgeons, the Southern Thoracic Surgical Association, and The Annals of Thoracic Surgery neither endorse nor discourage use of the new technology described in this article.
|
References
|
|---|
- McPherson DD, Hiratzka LF, Lamberth WC, et al. Delineation of the extent of coronary atherosclerosis by high-frequency epicardial echocardiography N Engl J Med 1987;316:304-309.[Abstract]
- Hiratzka LF, McPherson DD, Lamberth Jr WC, et al. Intraoperative evaluation of coronary artery bypass graft anastomoses with high-frequency epicardial echocardiographyexperimental validation and initial patient studies. Circulation 1986;73:1199-1205.[Abstract/Free Full Text]
- Suematsu Y, Takamoto S, Ohtsuka T. Intraoperative echocardiographic imaging of coronary arteries and graft anastomoses during coronary artery bypass grafting without cardiopulmonary bypass J Thorac Cardiovasc Surg 2001;122:1147-1154.[Abstract/Free Full Text]
- Haaverstad R, Vitale N, Tjomsland O, Tromsdal A, Torp H, Samstad SO. Intraoperative color Doppler ultrasound assessment of LIMA-LAD anastomoses in off-pump coronary artery bypass grafting Ann Thorac Surg 2002;74:S1390-S1394.[Abstract/Free Full Text]
- Eikelaar JHR, Meijer R, van Boven WJ, Klein P, Gründeman PF, Borst C. Epicardial 10-MHz ultrasound in off-pump coronary bypass surgerya clinical feasibility study using a minitransducer. J Thorac Cardiovasc Surg 2002;124:785-789.[Abstract/Free Full Text]
- Budde RPJ, Meijer R, Bakker PFA, Borst C, Gründeman PF. Endoscopic localization and assessment of coronary arteries by 13 MHz epicardial ultrasound Ann Thorac Surg 2004;77:1586-1592.[Abstract/Free Full Text]
- Budde RPJ, Dessing TC, Meijer R, Bakker PFA, Borst C, Gründeman PF. Robot-assisted 13 MHz epicardial ultrasound for endoscopic quality assessment of coronary anastomoses Interactive Cardiovascular and Thoracic Surgery 2004;3:616-620.[Abstract/Free Full Text]
- Budde RPJ, Meijer R, Dessing TC, Borst C, Gründeman PF. Detection of construction errors in ex vivo coronary artery anastomoses by 13-MHz epicardial ultrasonography J Thorac Cardiovasc Surg 2005;129:1078-1083.[Abstract/Free Full Text]
- Diegeler A, Thiele H, Falk V, et al. Comparison of stenting with minimally invasive bypass surgery for stenosis of the left anterior descending coronary artery N Eng J Med 2002;347:561-566.[Abstract/Free Full Text]
- Berger PB, Alderman EL, Nadel A, Schaff HV. Frequency of early occlusion and stenosis in a left internal mammary artery to left anterior descending artery bypass graft after surgery through a median sternotomy on conventional bypass. Benchmark for minimally invasive direct coronary artery bypass Circulation 1999;100:2353-2358.[Abstract/Free Full Text]
This article has been cited by other articles:
|
|
|
|
 
G. D'Ancona, J. M. Hartman, F. Bartolozzi, E. van Deel, D. J.G.M. Duncker, A. J.J.C. Bogers, M. Pilato, and A. P. Kappetein
Epicardial coronary artery Doppler: validation in the animal model
Interactive CardioVascular and Thoracic Surgery,
August 1, 2008;
7(4):
634 - 637.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
P. K. Hol, K. Andersen, H. Skulstad, P. S. Halvorsen, P. S. Lingaas, R. Andersen, J. Bergsland, and E. Fosse
Epicardial Ultrasonography: A Potential Method for Intraoperative Quality Assessment of Coronary Bypass Anastomoses?
Ann. Thorac. Surg.,
September 1, 2007;
84(3):
801 - 807.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
A. Calafiore
Invited commentary
Ann. Thorac. Surg.,
January 1, 2006;
81(1):
326 - 326.
[Full Text]
[PDF]
|
|
|
Top
Abstract
Introduction
