Ann Thorac Surg 2009;88:632-636. doi:10.1016/j.athoracsur.2009.03.010
© 2009 The Society of Thoracic Surgeons
New Technology
The Role of Intraoperative Indocyanine Green Fluorescence Angiography in Pediatric Cardiac Surgery
Brian Kogon, MDa,*,
Janet Fernandez, BSb,
Kirk Kanter, MDa,
Paul Kirshbom, MDa,
Bob Vincent, MDb,
Kevin Maher, MDb,
Nina Guzetta, MDc
a Division of Cardiothoracic Surgery, Emory University School of Medicine, Atlanta, Georgia
b Sibley Cardiology, Children's Healthcare of Atlanta, Atlanta, Georgia
c Division of Anesthesia, Emory University School of Medicine, Atlanta, Georgia
Accepted for publication March 6, 2009.
* Address correspondence to Dr Kogon, Emory University, Children's Healthcare of Atlanta, Egleston, Atlanta, GA 30322 (Email: brian_kogon{at}emoryhealthcare.org).
Presented at the Poster Session of the Forty-fifth Annual Meeting of The Society of Thoracic Surgeons, San Francisco, CA, Jan 26–28, 2009.
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Abstract
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Purpose: In surgical reconstructions for congenital heart defects, vessel and anastomotic site patency is critical to success. Indocyanine green fluorescence angiography offers potential for a reliable and rapid method of intraoperative assessment. We sought to determine its feasibility in congenital heart surgery.
Description: Patients undergoing the following repairs were eligible for imaging: (1) coronary artery reimplantation, (2) coarctation, (3) palliative shunts, and (4) pulmonary artery reconstruction.
Evaluation: Adequate postoperative images were obtained in 18 of 30 (60%) patients. Image adequacy was highest for Blalock-Taussig shunts (100%), coarctation repairs (86%), coronary reimplantations (66%), lowest for the hemi-Fontan (0%), Fontan (40%), and pulmonary artery reconstructions (33%). All adequate images showed vessel or anastomotic site patency, which corresponded to the subsequent postoperative echocardiograms and cineangiograms. There were no adverse events or mortalities.
Conclusions: Indocyanine green fluorescence imaging may provide an additional intraoperative imaging modality. Ultimately, the surgical procedure may be assessed and revised, if necessary, prior to leaving the operating room. This potentially will reduce the need for subsequent postoperative interventions, along with their associated morbidity and mortality.
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Introduction
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In children, complex surgical reconstructions are often required to treat congenital heart defects. As with coronary artery bypass grafting in adults, vessel and anastomotic site patency is critical to success. Certain congenital heart operations involve complicated blood vessel reconstructions and delicate anastomoses. Thrombosis, narrowing, and occlusion, particularly at suture lines, often contribute to morbidity and mortality. Unfortunately, the current method of evaluating the surgical repair intraoperatively is limited to echocardiography, either transesophageal or epicardial. Although this modality is excellent for some lesions, there is frequently indirect or poor resolution of anatomy in others. In addition, results are often subject to misinterpretation due to operator dependency.
The Novadaq Spy Intraoperative Imaging System (Novadaq Technologies Inc, Toronto, Canada) imaging system makes use of the fluorescence properties of indocyanine green to obtain images of blood vessels. Unlike conventional angiography, indocyanine green fluorescence imaging offers the potential for a reliable, noninvasive, inexpensive, and rapid method of intraoperative assessment of vessel and anastomotic patency.
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Technology
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Imaging Acquisition
The intraoperative imaging device (SPY Imaging System; Novadaq Technologies Inc) was positioned over the operative field. A bolus of fluorescent contrast agent was injected intravenously through an existing central line.
The imaging device emitted light at 806 nm causing the agent to fluoresce and emit light at 830 nm as it passed through the vascular system. A video camera equipped with an 830 nm band-pass filter captured and saved the images. The passage of contrast through the vascular system was also observed in real time on a video monitor [1].
The indocyanine green was administered in increments not to exceed the following individual doses: 1.25 mg in infants (< 1 yr), 2.5 mg in children (< 16 years), and 5 mg in adults. Repeat dosing and imaging was performed if needed. The total dose of dye was limited to 2 mg/kg. Images were obtained in the operating room prior to commencing and after weaning from cardiopulmonary bypass.
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Technique
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Patients
After obtaining internal review board approval, enrollment began. All patients underwent congenital heart surgery at the Children's Healthcare of Atlanta, Egleston Hospital. Patients undergoing the following repairs were eligible: coronary artery re-implantations, coarctation repairs, palliative shunts, and pulmonary artery reconstructions. Exclusion criteria included known sensitivity to indocyanine green iodides or inability to obtain informed consent.
Images
The surgeon and research coordinator reviewed individual image sequences and confirmed their adequacy. No revisions or alterations to the surgical plan were performed on the basis of the images.
Clinical Records
Preoperative, intraoperative, and postoperative echocardiographic reports were analyzed. Preoperative and postoperative cardiac catheterization reports were analyzed. The clinical course of the child was followed to detect any adverse events related to the SPY Imaging System.
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Clinical Experience
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Thirty-four imaging sequences were attempted during 30 patient operations as follows: arterial switch operations (4), coarctation repairs (8), hemi-Fontan connections (2), Fontan connections (6), modified Blalock-Taussig shunts, (6) right ventricle-pulmonary artery shunts (1), and pulmonary arterioplasties (7). Postoperative images were unobtainable during four of the procedures. For the remaining 30, adequate images were obtained in 18 (60%) (Fig 1). Image adequacy was highest for Blalock-Taussig shunts (100%) (Fig 2), coarctation repairs (86%) (Fig 3), and coronary reimplantations (66%) (Fig 4). Image adequacy was lowest for the hemi-Fontan (0%), Fontan (40%), and pulmonary artery reconstructions (33%). Reasons for unsuccessful imaging included small incision with difficult exposure, overlying structures obscuring the view of the desired area, nonuniform dye column, overdosing or underdosing of indocyanine green dye, bleeding with resultant extravasation of dye, and minimal penetrance through polytetrafluoroethylene (Gore-Tex; W. L. Gore & Assoc, Flagstaff, AZ). All of the successful images showed patent blood vessels and anastomoses. The results of successful intraoperative images (pre-repair and post-repair) were similar to the corresponding echocardiograms and cardiac cineangiograms. There were no adverse events and no mortalities.
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Fig 1. Ratio of successful images by procedure. (BTS = Blalock-Taussig shunts; PA = pulmonary artery; RV-PA = right ventricle to pulmonary artery.)
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Fig 2. Postoperative Blalock-Taussig (BT) shunt. (PTFE = polytetrafluoroethylene; RPA = right pulmonary artery.)
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Comment
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Indocyanine green has been approved for use in humans and has been safely used for more than 40 years. Its initial usefulness was for the measurement of cardiac output, assessment of hepatic function, and for ophthalmic angiography. In the last decade it has been used in adult cardiac surgery for intraoperative evaluation of coronary artery bypass grafts, and there have been many studies to show its efficacy in evaluating graft patency [2]. It has more recently been expanded into the fields of transplant surgery, neurosurgery, and plastic surgery. In transplant surgery, it has been used to evaluate donor-recipient anastomotic patency and organ perfusion [3]. During neurosurgery, it has been used in arterial, capillary, and venous phases to evaluate the occlusion of cerebral aneurysms and dural fistulas [4]. In plastic surgery, it has been used to evaluate the viability of tissue flaps and esophageal replacement grafts [5].
Although there is some impressive data regarding the use of the SPY imaging system in other specialties, there is little documented relative to its intraoperative usefulness in congenital heart surgery.
Intraoperative Imaging
For congenital heart surgery, the current method of evaluating repairs intraoperatively is transesophageal echocardiography. Although this modality is excellent for intracardiac lesions, there is frequently indirect or poor resolution of the surrounding vasculature. The gold standard for vascular imaging is conventional angiography, which can be performed intraoperatively using movable fluoroscopic equipment [6]. However, this is cumbersome, potentially nephrotoxic, often requires additional sites of vascular access, and has not been accepted routinely for congenital heart surgery. Several other methods have been developed and used for intraoperative assessment of vascular patency. These have included electromagnetic, ultrasound flow measurement, Doppler velocity waveform, thermal angiography, and intravascular ultrasound [7–9]. Although intravascular ultrasound may be the most promising and feasible with direct vascular access through an open chest, peripheral vascular access issues in small pediatric patients may be a limiting factor. Otherwise, most of these techniques suffer from severe limitations and often provide indirect or poor resolution definition of grafts or flow.
Rationale for Assessment in Certain Cardiac Defects
Certain congenital heart operations involve complicated blood vessel reconstructions and delicate anastomoses. Thrombosis, narrowing, and occlusion of vessels, particularly at suture lines, often contribute to morbidity and mortality. Clearly, with these operations, there is a particular risk for these problems and conventional imaging techniques are suboptimal.
Coronary artery reimplantation
Coronary artery reimplantation is required for several congenital heart defects. It is required during an arterial switch procedure for transposition of the great arteries, during repair of anomalous left coronary artery from the pulmonary artery, and during a Ross procedure or aortic root replacement. A widely patent coronary ostium without twisting or kinking of the proximal artery is critical to success, and problems can lead to myocardial ischemia and subsequent infarction.
Coarctation of the aorta
Repair for coarctation of the aorta involves opening a narrow area in the aorta to provide unobstructed flow from the aortic arch into the descending aorta. Residual ductal tissue or anastomotic problems can result in a recurrent coarctation, necessitating subsequent percutaneous or surgical intervention.
Palliative shunts
Placement of a shunt is a common palliative operation for congenital heart disease and is typically used in patients with inadequate or ductal-dependant pulmonary blood flow. This commonly takes the form of a systemic-to-pulmonary artery shunt (Blalock-Taussig shunt). Partial occlusion typically results in decreased peripheral oxygen saturation and hypoxemia. When children are shunt-dependent after surgery, relying on shunt patency for survival, occlusion may be life threatening. In these cases, surgical or catheter-based intervention may be urgently required to restore patency.
Pulmonary artery reconstruction
Pulmonary stenosis can occur anywhere along the right ventricular outflow tract. In its most severe form, pulmonary atresia, the native branch pulmonary arteries can be severely hypoplastic or even discontinuous. Occasionally, major aortopulmonary collaterals contribute to pulmonary blood flow. In these instances, a combination of branch or distal pulmonary artery reconstruction and unifocalization of collaterals is often required.
For these technically challenging operations, it would be extremely advantageous to detect potential problems with vessel and anastomotic patency prior to leaving the operating room, avoiding the need for subsequent postoperative cardiac catheterization, catheter-based intervention, or surgical reoperation, along with the associated morbidity and mortality.
Limitations
The design of our study allowed 40 patients, with a maximum of 10 patients in each of the four operative categories: (1) coronary reimplants, (2) coarctations, (3) variable palliative shunts, and (4) pulmonary reconstructions. This created very low numbers in some groups.
Although we have been able to determine which operations might be best suited for this technology, the small number of patients has skewed our results. For our most successful repairs (ie, arterial switch operations, coarctation repairs, and Blalock-Taussig shunts), the success rate was 14 of 16 (88%), although the success rate among the remaining repairs was 4 of 14 (29%). Reasons for unsuccessful imaging included a small incision with difficult exposure, overlying structures obscuring the view of the desired area, nonuniform dye column, over or underdosing of indocyanine green dye, bleeding with resultant extravasation of dye, and minimal penetrance through polytetrafluoroethylene (Gore-Tex [W.L. Gore & Assoc]). Although some of these difficulties have been overcome by an increase in experience as the study progressed, others have not. For our least successful repairs, such as the hemi-Fontans, Fontans, and pulmonary artery reconstructions, the inability to obtain a uniform dye column at the site of interest and the overlying structures obscuring the view of the desired area will likely provide ongoing persistent obstacles in these cases. The small number of patients has also limited our ability to detect suboptimal results. Fortunately, the great majority or congenital cardiac operations are first-time successes, and a larger number of patients would be required to detect such suboptimal technical repairs.
Future
In addition to intraoperative assessment, there may be situations in the intensive care unit where this technology would be advantageous. Often after complex reconstructions in neonates, the myocardium is edematous and cardiac function is marginal. The chest is left open intentionally to increase cardiac domain and allow for myocardial recovery. If these patients fail to progress, they are sent (usually in critical condition) to the cardiac catheterization laboratory to evaluate the surgical repair. This could potentially be avoided with open-chest bedside imaging in an intensive care unit setting.
Conclusion
Just as in many other surgical specialties, indocyanine green fluorescence imaging may provide an important intraoperative imaging modality for congenital heart surgery. The technology appears to be safe in children, and the results of successful intraoperative images are similar to the corresponding echocardiograms and cardiac cineangiograms.
Ultimately, with such imaging technology, congenital heart surgeons will be able to check the quality of the procedure and revise, redo, or perform additional procedures as dictated by the images, prior to leaving the operating room.
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Disclosures and Freedom of Investigation
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This work was supported by the Novadaq Technologies Inc, Toronto, Canada. They loaned the technology and provided research coordinator funding. The authors had full control of the design of the study, methods used, outcome measurements, analysis of data, and production of the written report.
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Footnotes
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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.
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References
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- Sekijima M, Tojimbara T, Sato S, et al. An intraoperative fluorescent imaging system in organ transplantation Transplant Proc 2004;36:2188-2190.[Medline]
- Raabe A, Beck J, Gerlach R, Zimmermann M, Seifert V. Near-infrared indocyanine green video angiography: a new method for intraoperative assessment of vascular flow Neurosurgery 2003;52:132-139.[Medline]
- Holm C, Mayr M, Hofter E, Ninkovic M. Perfusion zones of the DIEP flap revisited: a clinical study Plast Reconstr Surg 2006;117:37-43.[Medline]
- Elbeery JR, Brown PM, Chitwood Jr WR. Intraoperative MIDCABG arteriography via the left radial artery: a comparison with Doppler ultrasound for assessment of graft patency Ann Thorac Surg 1998;66:51-55.[Abstract/Free Full Text]
- Louagie YA, Haxhe JP, Buche M, Schoevaerdts JC. Intraoperative electromagnetic flow meter measurements in coronary artery bypass grafts Ann Thorac Surg 1994;57:357-364.[Abstract/Free Full Text]
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- Walpoth BH, Bosshard A, Genyk I, et al. Transit time flow measurement for early graft failure during myocardial revascularization Ann Thorac Surg 1998;66:1097-1100.[Abstract/Free Full Text]
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Abstract
Introduction
