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Ann Thorac Surg 1997;64:171-174
© 1997 The Society of Thoracic Surgeons

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Original Articles: Cardiovascular

Thoracoscopic Transmyocardial Laser Revascularization

Division of Cardiac Surgery, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts

Accepted for publication February 10, 1997.

	Abstract

Top Footnotes Abstract Introduction Materials and Methods Results Comment Acknowledgments References

 
Background. Transmyocardial laser revascularization is a promising surgical technique used to treat nonreconstructable ischemic heart disease. Recent clinical data show that this technique improves the regional perfusion of ischemic myocardium and reduces angina. Presently, transmyocardial laser revascularization requires an open, lateral thoracotomy. We report here the use of thoracoscopic techniques to perform transmyocardial laser revascularization in a closed chest fashion.

Methods. Five Yorkshire farm pigs underwent left chest thoracoscopic exploration and pericardiotomy. A specialized laser handpiece then was introduced into the chest and thoracoscopic transmyocardial laser revascularization was performed (one channel per square centimeter) using an 800-W CO₂ laser.

Results. Video analysis and gross pathology revealed that the anatomic area accessible to thoracoscopic transmyocardial laser revascularization included the entire left ventricular free wall distributions of the left anterior descending, left circumflex, and posterior descending arteries, from base to apex. Standard hematoxylin and eosin staining confirmed the creation of complete and patent 1-mm-diameter transmural channels throughout these distributions.

Conclusion. We have shown that transmyocardial laser revascularization can be performed effectively and safely by thoracoscopy, and that this less invasive technique may reduce morbidity and provide a more cost-effective alternative therapy for nonreconstructable ischemic heart disease.

	Introduction

Top Footnotes Abstract Introduction Materials and Methods Results Comment Acknowledgments References

 
Despite continued success in treating ischemic heart disease with interventional radiologic techniques and coronary artery bypass grafting, there remains a clinically symptomatic patient population with diffuse, small-vessel pathology not amenable to these current therapeutic modalities. Recently, transmyocardial laser revascularization (TLR) has been used successfully to treat this growing population of patients [1, 2].

Arterioluminal vessels and myocardial sinusoids that open freely into the ventricular cavity first were described by Wearn and associates [3]. The use of these networking intramyocardial channels as direct conduits for myocardial reperfusion was attempted by Beck [4] with myopexy and omentopexy, and later by Vineberg [5] with intramyocardial implantation of the internal mammary artery. A variety of other techniques have been used to create channels that would connect the ventricular cavity directly to this "sinusoidal" network, including transmural ventricular acupuncture [6], low-energy CO₂ laser drilling [7], and holmium:yttrium-argon-garnet laser drilling [8]. Recently, by performing TLR with a high-energy, 800-W CO₂ laser, we and others have shown improvements in regional perfusion of the ischemic myocardium by both subjective and objective measurements [1, 2]. However, although this procedure does not require cardioplegic arrest or cardiopulmonary bypass, it does require a left lateral thoracotomy. These experiments were designed to explore the feasibility of performing thoracoscopic TLR, which may lead to a decrease in the morbidity of TLR while reducing the delivery cost of this promising technique.

	Materials and Methods

Top Footnotes Abstract Introduction Materials and Methods Results Comment Acknowledgments References

 
Yorkshire farm pigs of either sex (n = 5) were used for these experiments and all animals received humane care in compliance with the "Principles of Laboratory Animal Care" formulated by the National Society for Medical Research and the "Guide for the Care and Use of Laboratory Animals" prepared by the National Academy of Sciences and published by the National Institutes of Health (NIH Publication No. 85-23, revised 1985). Anesthesia was induced using ketamine hydrochloride, 10 mg/kg (Parke-Davis, Morris Plains, NJ), mixed with xylazine, 0.5 mg/kg (Miles, Shawnee Mission, KA), and an adequate anesthetic plane was maintained with 2% halothane inhalation. All animals then were subjected to selective right lung ventilation, placed in the right lateral decubitus position, and flexed to increase intercostal space and thoracic cavity size. Systemic arterial pressure was monitored through a physiologic pressure transducer (Statham, P10EZ; Spectromed, Oxnard, CA) in a femoral artery. Venous access was established through the femoral vein and continuous electrocardiographic monitoring (78352C; Hewlett-Packard, Andover, MA) was carried out.

A 30-degree angled thoracoscope (Karl Storz, Culver City, CA) was introduced into the left thoracic cavity through a 2-cm incision in the seventh intercostal space in the posterior axillary line (port 1). Second and third incisions were made in the eighth intercostal space in the midaxillary line (port 2) and in the seventh intercostal space in the anterior axillary line (port 3) for further instrumentation. In 3 of the 5 animals, a fourth instrument site was required and was placed about two fingerbreadths medial to the tip of the scapula (port 4). Bretylium, 5 mg/kg, was given as an intravenous bolus before thoracic instrumentation. Sponge sticks were used for retraction of the lung through port 2 to expose the left lateral pericardial surface. Avoiding any visible epicardial vessels, a skin hook was placed through port 3 and the pericardium was elevated 1 cm anterior to the phrenic nerve in the midventricular region. Pericardiotomy then was performed 1 cm anterior to the phrenic nerve with endoscopic scissors (Ethicon Inc, EndoSurgery, Cincinnati, OH), extending from the atrioventricular groove to the apex. With the pericardium elevated and the atria retracted, the pericardial incision also was carried medially along the atrioventricular groove to the level of the left anterior descending artery. The pericardial flap then was pushed inferomedial to expose the entire left ventricular free wall.

Specialized thoracoscopic laser handpieces (PLC Inc, Milford, MA), 0 or 90 degrees, then were introduced into the chest through the various instrument ports. Thoracoscopic TLR was accomplished with an 800-W CO₂ laser (PLC Inc.). The maximal output of the Heart Laser is 80 J, with an adjustable pulse width from 5 to 99 ms. Port locations and the handpiece angle for each laser shot were chosen to facilitate a laser beam vector perpendicular to the epicardial surface without significantly distorting or compressing the left ventricle. Video-assisted placement of the laser handpieces was used to avoid any major coronary vasculature, and transmyocardial channels were drilled with a distribution of about one channel per square centimeter. The average pulse width and energy delivery of the laser shots were 20 ms and 16 J, respectively, to achieve transmyocardial penetration. Electrocardiographic monitoring was maintained throughout the procedure and all laser shots were fired synchronously with the R wave of the electrical cycle. Hemostasis of bleeding epicardial channel openings was achieved with gentle sponge stick pressure applied over the channels for 30 to 120 seconds. Hemodynamic stability then was achieved in all animals. After completion of the procedure, all animals were systemically heparinized and given a lethal dose of potassium chloride. A left lateral thoracotomy then was performed, and the hearts were harvested and fixed in 10% formalin.

Intraoperative video observation, video analysis, and gross pathologic inspection from all experiments was carried out. Representative areas of myocardium were embedded in paraffin, sectioned at 4 mm, and stained with hematoxylin and eosin. Channel distribution, dimensions, and patency were assessed by an independent observer.

	Results

Top Footnotes Abstract Introduction Materials and Methods Results Comment Acknowledgments References

 
All animals survived thoracoscopic TLR, maintaining a normal sinus rhythm and a mean systolic blood pressure greater than 60 mm Hg before sacrifice. Hemostasis of laser channels was achieved in all animals with simple epicardial pressure as described previously. One animal suffered a laceration of an epicardial coronary vein during pericardiotomy that also was controlled with simple point pressure over the injury. By using various combinations of port site and handpiece angle, the anatomic area that we were able to visualize and that was accessible to thoracoscopic TLR included the complete left ventricular free wall distributions of the left anterior descending, left circumflex, and posterior descending arteries, from base to apex (Fig 1). Gross pathology and standard hematoxylin and eosin staining confirmed the creation of complete and patent 1-mm-diameter transmural channels throughout the distribution described previously (Fig 2).

View larger version (21K): [in this window] [in a new window]   Fig 1. . Thoracoscopic transmyocardial laser channel distribution. The distribution of laser channels (dots) from each postmortem specimen is depicted as determined by gross pathologic examination. (CRX =right circumflex artery;LAD =left anterior descending artery;PDA =posterior descending artery.)

View larger version (106K): [in this window] [in a new window]   Fig 2. . Histologic features of laser channels. (A) Epicardial surface (EPI) and penetration of laser channel. (B) Patent channel in midmyocardium. (C) Laser channel penetrating endocardial surface (END) into the left ventricular cavity.

	Comment

Top Footnotes Abstract Introduction Materials and Methods Results Comment Acknowledgments References

This experimental model has demonstrated that TLR can be performed effectively and safely in a closed chest fashion using thoracoscopic techniques and new thoracoscopic laser equipment. The clinical application of thoracoscopic TLR should reduce further the direct cost of performing transmyocardial revascularization. With refinement of these closed chest techniques, we will decrease operative time, intensive care unit utilization, and total number of hospital days required for therapy. This is analogous to the reductions in aggregate costs seen with the advent of laparoscopic techniques in the surgical treatment of symptomatic cholelithiasis and of thoracoscopic techniques in the performance of pulmonary wedge resection [10].

We have shown that TLR can be performed effectively and safely by thoracoscopy. We conclude that this less invasive, closed chest technique may reduce the morbidity of TLR compared to present techniques that require a formal thoracotomy, and may improve the cost-effectiveness of this alternative therapy for nonreconstructable ischemic heart disease.

	Acknowledgments

Top Footnotes Abstract Introduction Materials and Methods Results Comment Acknowledgments References

 
The laser for this study was provided courtesy of PLC Medical Systems, Inc, Milford, MA. This work was supported by funds derived from the Brigham Cardiac Surgical Research Fund.

	Footnotes

Top Footnotes Abstract Introduction Materials and Methods Results Comment Acknowledgments References

 
Address reprint requests to Dr Cohn, Division of Cardiac Surgery, Brigham and Women's Hospital, 75 Francis St, Boston, MA 02115.

	References

Top Footnotes Abstract Introduction Materials and Methods Results Comment Acknowledgments References

 

1. Horvath KA, Mannting F, Cummings N, Shernan SK, Cohn LH. Improved myocardial perfusion and relief of angina after transmyocardial laser revascularization. J Thorac Cardiovasc Surg 1996;111:1047–53.[Abstract/Free Full Text]
2. Mirhoseini M, Shelgikar S, Cayton MM. New concepts in revascularization of the myocardium.Ann Thorac Surg 1988;45:415–20.[Abstract]
3. Wearn JT, Mettier SR, Klumpp TG, Zschiesche LJ. The nature of the vascular communications between the coronary arteries and the chambers of the heart. Am Heart J 1933;2:143–64.
4. Beck CS. The development of a new blood supply to the heart by operation. Ann Surg 1935;102:801–13.[Medline]
5. Vineberg A. Clinical and experimental studies in the treatment of coronary artery insufficiency by internal mammary artery implant. J Thorac Cardiovasc Surg 1965;50:181–9.
6. Sen PK, Udwadia TE, Kinare SG, Parulkar GB. Further studies in multiple transmyocardial acupuncture as a method of myocardial revascularization. Surgery 1968;64:861–70.[Medline]
7. Landreneau R, Nawarawong W, Laughlin H, et al. Direct CO_{2 laser revascularization of the myocardium. Lasers Surg Med 1991;11:35–42.}
8. Yano OJ, Bielefeld MR, Jeevanandam V, et al. Prevention of acute regional ischemia with endocardial laser channels. Ann Thorac Surg 1993;56:46–53.[Abstract]
9. Horvath KA, Smith WJ, Laurence RG, Schoen FJ, Appleyard RF, Cohn LH. Recovery and viability of an acute myocardial infarct after transmyocardial laser revascularization. J Am Coll Cardiol 1995;25:258–63.[Abstract]
10. Hazelrigg SR, Nunchuck SK, Landreneau RJ, et al. Cost analysis for thoracoscopy: thoracoscopic wedge resection. Ann Thorac Surg 1993;56:633–5.[Abstract]

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This Article Abstract Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Brian J. deGuzman Keith A. Horvath Lawrence H. Cohn Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by deGuzman, B. J. Articles by Cohn, L. H. Search for Related Content PubMed PubMed Citation Articles by deGuzman, B. J. Articles by Cohn, L. H.