Laser revascularization of ischemic skeletal muscle.

BACKGROUND: Clinical trials have shown that transmyocardial laser revascularization is an effective secondary treatment for ischemic heart disease patients. Laser revascularization may also provide an alternative method for treating peripheral vascular disease. METHODS: The purpose of this study was to investigate the potential for laser revascularization in ischemic skeletal muscle. Eighteen rabbits (3-4 kg) were instrumented chronically with transit time ultrasound flowprobes on both common iliac arteries. All rabbits performed graded exercise tests on a treadmill where maximal blood flow was recorded. Unilateral hindlimb ischemia was produced by ligation of one femoral artery. At week 3 postligation, 10 rabbits received laser therapy and 8 underwent a sham surgery. In each of four muscles (gracilius, medialis, sartorius, and biceps femoris) 5 to 22 laser channels were created (average = 52 channels per leg). RESULTS: At week 3 postligation the maximal blood flow of the ischemic limb for the treated group was 64 +/- 3 ml/min (mean +/- SEM) and at 6 weeks postlaser therapy maximal blood flow increased to 75 +/- 5 ml/min. The sham surgery group had a maximal blood flow of 58 +/- 4 ml/min at week 3 postligation and 66 +/- 3 ml/min at week 6 postsham surgery. CONCLUSION: These results indicate that laser therapy does not induce angiogenesis and vascular remodeling in the ischemic hindlimb of a rabbit which exceeds that seen with a sham surgery.

Transmyocardial laser revascularization in the patient with unmanageable unstable angina.

BACKGROUND: Transmyocardial laser revascularization (TMR) provides relief for patients with chronic angina, nonamenable to direct coronary revascularization. Unmanageable, unstable angina (UUA) defines a subset of patients with refractory angina who are at high risk for myocardial infarction and death. Patients were classified in the UUA group when they had been admitted to the critical care unit with unstable angina for 7 days with three failed attempts at weaning them off intravenous antianginal medications. METHODS: Seventy-six treated patients were analyzed to determine if TMR is a viable option for patients with unmanageable unstable angina. These patients were compared with 91 routine protocol patients (protocol group [PG]) undergoing TMR for chronic angina not amenable to standard revascularization. The procedure was performed through a left thoracotomy without cardiopulmonary bypass. These patients were followed for 12 months after the TMR procedure. Both unmanageable and chronic angina patients had a high incidence of at least one prior surgical revascularization (87% and 91%, respectively). RESULTS: Perioperative mortality (< or = 30 days post-TMR) was higher in the UUAG versus PG (16% vs 3%, p = 0.005). Late mortality, up to 1 year of follow-up, was similar (13% vs 11%, UUAG vs PG; p = 0.83). A majority of the adverse events in the UUAG occurred within the first 3 months post-TMR, and patients surviving this interval did well, with reduced angina of at least two classes occurring in 69%, 82%, and 82% of patients at 3, 6, and 12 months, respectively. The percent improvement in angina class from baseline was statistically significant at 3, 6, and 12 months. A comparable improvement in angina was found in the protocol group of patients. CONCLUSIONS: TMR carried a significantly higher risk in unmanageable, unstable angina than in patients with chronic angina. In the later follow-up intervals, however, both groups demonstrated similar and persistent improvement in their angina up to 12 months after the procedure. TMR may be considered in the therapy of patients with unmanageable, unstable angina who otherwise have no recourse to effective therapy in the control of their disabling angina.

Transmyocardial laser revascularization in allograft coronary artery disease.

We used transmyocardial laser revascularization to treat accelerated cardiac allograft atherosclerosis in 2 patients. One patient received transmyocardial laser revascularization as sole therapy, the other as an adjunct to coronary artery bypass grafting. The systolic function improved in both patients, although the patient who had adjunctive transmyocardial laser revascularization died of systemic infection and renal failure on postoperative day 55. The second patient is alive and well 1 1/2 years after the laser procedure. We discuss 4 other patients who received transmyocardial laser revascularization treatment elsewhere in the United States. Transmyocardial laser revascularization has the potential to become important in the treatment of transplant atherosclerosis. Randomized clinical trials are warranted to assess the efficacy of transmyocardial laser revascularization in this setting.

Transmyocardial laser revascularization: results of a multicenter trial with transmyocardial laser revascularization used as sole therapy for end-stage coronary artery disease.

BACKGROUND: Transmyocardial laser revascularization was used as the sole therapy for patients with ischemic heart disease not amenable to percutaneous transluminal coronary angioplasty or coronary artery bypass grafting. This technique uses a carbon dioxide laser to create transmyocardial channels for direct perfusion of the ischemic heart. METHODS: Since 1992, 200 patients, at eight hospitals in the United States, have undergone transmyocardial laser revascularization. The patients have a combined 1560 months of follow-up for an average of 10 +/- 3 months per patient. Their age was 63 +/- 10 years and their ejection fraction was 47% +/- 12%. Eighty-two percent had at least one previous bypass graft operation and 38% had a prior angioplasty. Preoperatively, the patients underwent nuclear single photon emission computed tomography perfusion scans to identify the extent and severity of their ischemia. These scans were repeated at 3, 6, and 12 months. Angina class, admissions for angina, and medications were recorded. RESULTS: The perioperative mortality was 9%. Angina class decreased significantly from before treatment to 3, 6, and 12 months (p < 0.001). Likewise, there was a significant decrease in the number of perfusion defects in the treated left ventricular free wall. Concomitantly, there was a significant decrease in the number of admissions for angina in the year after the procedure when compared with the year before treatment (2.5 vs 0.5 admissions per patient-year). CONCLUSION: These combined results indicate that transmyocardial laser revascularization provides angina relief, decreases hospital admissions, and improves perfusion in patients with severe coronary artery disease.

Transmyocardial laser revascularization: historical background and future directions.

Transmyocardial laser revascularization (TMLR) was investigated as a possible treatment alternative for patients with refractory coronary artery disease. This paper is a summary of nearly four decades of research by the authors. Beginning in 1969 experimental studies were conducted on the beating heart. A prototype 450 W carbon dioxide laser was used to create channels in the ischemic myocardium. Initial clinical studies began in 1984. A protocol was developed for TMLR as an adjunct to CABG in those patient who had at least one vessel which could be bypassed and areas of ischemia which were not amenable to bypass. In the early 1990's the development of a 850 W CO2 laser for clinical use allowed us to begin investigation of TMLR on the beating heart. Patients with end stage coronary artery disease who were not candidates for other forms of treatment were selected. The early results are encouraging with patient followup of from 3 months to 5 years. There are numerous controversies regarding the effects of TMLR on myocardial function and perfusion. To quantify these effects the authors have performed acute and chronic studies on swine using sophisticated techniques with 3D cine magnetic resonance imaging. We concluded TMLR improved left ventricular function and perfusion in acute and chronic ischemia.

A clinician's overview of laser systems for cardiovascular applications.

This paper discusses the current lasers used in cardiovascular applications and presents an overview on function, characteristics, and tissue interactions of the principal lasers used in this field. The discussion includes the lasers and delivery systems currently in use, or with potential future application, for laser angioplasty and laser recanalization. Included are low-intensity laser as well as high-power laser applications.

Transmyocardial laser revascularization: a review.

There is an increasing number of treatment alternatives available for those with ischemic heart disease. Surgical procedures are more sophisticated, a wide array of medications are available, and numerous catheter techniques have evolved to treat patients with coronary artery disease. Technical advances and lifestyle modifications have contributed to a decline in age-adjusted death rates. Despite these advances, there remain a significant number of patients with myocardial ischemia who are not candidates for conventional therapies. Transmyocardial laser revascularization may be a viable adjunct or alternative therapy. In performing this technique, channels are made, from the epicardial surface of the heart through the left ventricle and endocardium, with the CO 2 laser. Perfusion is from the blood supply in the left ventricle via the channels. Postoperative thallium stress tests and left ventriculography indicate that the channels remain patent and protect the ischemic muscle. Experimental and early clinical results of transmyocardial laser revascularization suggest that a group of patients may benefit from this treatment.

Technical considerations and factors that influence the outcome of laser-assisted angioplasty.

In the last several years many studies have been conducted to evaluate the feasibility of laser-assisted angioplasty procedures as a therapeutic option for the treatment of patients with peripheral vascular disease. Assessing patient outcomes from studies done at various centers is complicated by the number of variables in patient selection, technical aspects of the procedures, laser parameters, and followup procedures. An ongoing process of defining and refining important parameters and aspects of these procedures is evolving. Important components in achieving good long-term results are technical dexterity with catheter systems, knowledge of angiography techniques, in-depth knowledge in the evaluation and treatment of patients with peripheral vascular disease, and a thorough understanding of laser biophysics and tissue interactions. The importance of technical details as a determinant of successful outcome in the treatment of these patients is discussed. Percutaneous vascular access is the method of choice for angioplasty procedures, but about 36% of patients will require surgical exposure of the femoral artery and possibly endarterectomy of patchplasty. In 11% of patients, the intraluminal channel is inadequate, revascularization is incomplete, or for other technical reasons surgical bypass is necessary. Peripheral laser-assisted angioplasty is a viable treatment alternative in selected patients. As the technique matures the value of its role in the therapeutic armamentarium will emerge.

Evaluation of clinical results following laser recanalization of the peripheral arteries.

As experience is gained with laser-assisted angioplasty and as long-term follow-up results become available, a realistic and objective view of its role in the treatment of patients with occlusive disease of arteries in the peripheral vascular tree is becoming available. Comparison with results of conventional treatment methods is warranted. Experience in treating patients with vascular lesions is helpful in patient selection, management during the procedure, and follow-up care. Evaluation of experience in 169 procedures, with a follow-up time of 1 month to 3 years indicates what direction evolving patency rates are taking.

Clinical and histological evaluation of laser myocardial revascularization.

Studies exploring methods to revascularize the ischemic myocardium through increasing the collateral circulation were conducted by many investigators before the advent of myocardial revascularization by aortocoronary bypass grafting. Present alternatives, including surgical intervention, balloon angioplasty, thrombolytic therapy, and medical management, are the treatment of choice for the majority of patients. There are, however, a number of patients who do not respond to conventional management strategies. A clinical protocol was designed to assess the efficacy of transmural revascularization by creating CO2 laser channels in the ischemic areas of the left ventricle. Channels were made from the epicardial surface of the heart, through the ventricle, to the endocardium. Patients entered in the study were candidates for bypass grafting, but because of the pathology of the coronary artery system, bypass grafting alone would have resulted in incomplete revascularization. Postoperative thallium stress tests and left ventriculography indicate that channels have remained patent and that they perfuse the myocardium. Myocardial revascularization by laser channels may offer a viable adjunct in the treatment of ischemic heart disease.

New concepts in revascularization of the myocardium.

The concept of direct revascularization of ischemic myocardium by transmural left ventricular conduits has been investigated by several researchers. Early success was followed by closure of the pathways by fibrosis and scarring caused by mechanical trauma. The CO2 laser was examined as an alternative method of creating channels. Early experiments supported the hypothesis that laser channels would perfuse ischemic areas and would remain patent. Histological examination showed patent, endothelialized channels more than 2 years following operation in the experimental model. A clinical protocol was designed to assess the results of laser revascularization in a series of 12 patients. Patients selected were candidates for bypass grafting, but because of the coronary artery pathology involved, it was thought bypass grafting alone would result in incomplete revascularization. None of the 12 patients have died. Follow-up ranges from 3 to 32 months. Postoperative thallium stress tests and left ventriculography indicate that channels have remained patent and that they perfuse the myocardium. Direct laser revascularization of the myocardium may offer a viable adjunct in the treatment of ischemic heart disease.

Laser myocardial revascularization.

A significant number of patients with ischemic heart disease are not candidates for coronary artery bypass or percutaneous transluminal angioplasty and do not respond to medical management. This group includes those who have diffuse coronary artery disease, those with poor ventricular function, and those who have had poor results from previous surgery. Developing a method to directly revascularize the myocardium by creating channels through the ventricular wall has challenged many investigators. Early methods, including needle acupuncture, were successful in the acute phase, but long-term patency could not be achieved. Closure of the channels was due to fibrosis and scarring. Experiments in our laboratory demonstrated that myocardial channels, made with the CO2 laser, remained patent up to five years. Histopathologic examination of the channels showed minimal damage to the surrounding cells in the acute phase. Studies at intervals of two months to two years showed patent endothelialized channels, with no evidence of fibrosis. Channels created in the myocardium protected the ventricle against an ischemic event when the left anterior descending branch of the coronary artery was ligated. Clinical experience with direct myocardial revascularization by CO2 laser indicates it may be a viable method of treating those patients with ischemic heart disease who are not candidates for other forms of management. The treatment and early postoperative follow-up in one patient are described.

Laser applications in thoracic and cardiovascular surgery.

Lasers are increasingly being used in thoracic and cardiovascular surgery. This general review discusses the use of carbon dioxide lasers for myocardial revascularization in animal studies, a report of a single clinical experience with laser revascularization of the heart, laser debridement of the gangrenous lesions of an ischemic extremity, and use of the laser for excision of chest wall tumors. Work is also being done using lasers in vaporization of atherosclerotic plaques, photoradiation therapy of bronchogenic carcinoma with hematoporphyrin derivative, and photoresection therapy of obstructive lesions of the bronchus and trachea.

Myocardial revascularization by laser: a clinical report.

Methods used to revascularize ischemic myocardium have included arterial reconstruction, coronary artery bypass grafting, providing direct circulation from the intraventricular chamber, and techniques to promote collateral circulation. Ventricular channels from the epicardial surface through the endocardium are readily made with the CO2 laser. Animal experiments suggest that these channels protect the ischemic myocardium and provide circulation to the muscle from the ventricular chamber. Clinical use of the CO2 laser in conjunction with aortocoronary bypass grafting is reported in a patient with three-vessel coronary artery disease and total occlusion of the left anterior descending coronary artery (LAD), and hypokinesis of the anterior wall and apex. Following bypass a series of laser channels were made in the hypokinetic area of the left ventricle. Postoperative myocardial Tc PYP scans were within normal limits, including the previously dyskinetic anterior apical area. Serial EKGs remained unchanged from the preoperative status. Creatinine phosphokinase-myocardial band (CPK-MB) was elevated to 6 on the first and second postop day and was 0 from the third day. The patient was not recatheterized. The technique of myocardial revascularization by laser may be a viable addition to present treatment modalities. Further investigation and long-term follow-up are needed.

Transventricular revascularization by laser.

Transventricular acupuncture or revascularization by the method of producing channels between the ventricular cavity and the ischemic myocardium has challenged several investigators. The concept of producing these channels using high-energy CO2 laser was based on the finding that the laser beam could produce small channels devoid of debris, and fibrosis would not occur. Four groups of mongrel dogs with six animals in each group were studied. In three groups the left anterior descending (LAD) branch of the coronary arteries was ligated above the first diagonal, and channels were made in the myocardium according to the protocol for each group. The fourth group was the control, the LAD was ligated but the myocardium was not exposed to laser treatment. In the control group all animals died within 20 minutes of LAD ligation. Animals in the other groups survived ligation with laser, and were subsequently sacrificed at varying intervals. At autopsy the epicardial component of the channels was visible. Penetration through the myocardium could be demonstrated. Microscopically the channels were patent and endothelialized. Further investigations are in process, but we believe laser channels protect and nourish the ischemic myocardium.

Revascularization of the heart by laser.

The possibility of revascularizing the myocardium with high-energy laser was investigated based on the finding that the laser beam could produce small channels in the tissue of the myocardium that were devoid of debris and scarring. The technique was investigated in 4 groups of 6 mongrel dogs each. In 3 of the groups, the left anterior descending (LAD) coronary artery was ligated above the first diagonal branch and the myocardium was treated with the laser energy according to the protocol of that group. In the fourth control group, the LAD artery was ligated but the myocardium was not subjected to laser treatment. In the first 3 groups, the myocardium was protected by the channels produced by the application of the laser energy. The animals were subsequently sacrificed at various intervals. In the control group, all of the animals died within 20 minutes of ligation of the artery. At autopsy, the epicardial sites of the channels created by the laser were clearly visible and a lack of charring in the channels was demonstrated. The penetration through the endocardial surface could be demonstrated. Microscopically, the channels were patent and endothelialized. It is concluded that the channels created in the myocardium effectively helped to protect the myocardium from acute coronary artery occlusion in this model in dogs.