Transmyocardial laser revascularization]

The clinical experience with transmyocardial laser revascularization indicates that angina is relieved significantly, perfusion and treadmill tolerance are improved and hospital admissions are decreased. The exact mechanism for a laser revascularization linked improvement is still unknown. Transmyocardial laser revascularization should be used only in highly selected cases when conventional methods fail to improve patients symptoms. Further evaluation of the efficacy of the new indirect revascularization method in clinical (larger multicenter trials) and experimental studies to elucidate the mechanism of TMLR is warranted. Experimental long-term studies to explain the mechanism are in progress.     

Transmyocardial laser revascularization: current status.

Transmyocardial laser revascularization (TMLR) has been widely evaluated for treatment of the ischemic myocardium either in conjunction with coronary artery bypass grafting or as sole therapy. Clinically, it has shown significant improvement for angina symptoms, but the mechanism by which this modality works is unknown at this time. The original premise on which transmyocardial revascularization was established depended on its ability to essentially generate channels that would directly carry blood from the ventricle into the ischemic myocardium. This theory, however, has not been substantiated, so other mechanisms have been postulated. This article gives a historical perspective on the advent of transmyocardial revascularization and the many animal and human studies that have paved the way for its clinical use. Current controversies are examined, along with the new advances in laser technology and where the future of TMLR is headed.     

Transmyocardial laser revascularization in ischemic cardiomyopathy.

BACKGROUND: In ischemic cardiomyopathy (left ventricular ejection fraction [LVEF] < or = 30%), myocardial revascularization by coronary artery surgery has better results than heart transplantation, provided there is sufficient ischemic but viable myocardium. The mode of action of transmyocardial laser revascularization (TMR) is still being debated, but if the procedure induces improved myocardial perfusion it could be a "bridge," or alternative, to heart transplantation. METHODS: We retrospectively analyzed 194 patients, who underwent TMR between July 1997 and October 1999. Patients with TMR as an adjunct to coronary artery surgery (n = 30) and those who did not provide written consent to the procedure (n = 8) were excluded; 126 patients had normal or moderately reduced left ventricular function, and 30 patients with ischemic cardiomyopathy (LVEF < or = 30%) were included. RESULTS: After 12 months, the Canadian Cardiovascular Society (CCS) score dropped significantly from 3.6 (3 to 4) to 2.4 (1 to 4) and maximum work load increased significantly from 58 W (25 to 100 W) to 73 W (25 to 120 W). However, thallium score and LVEF did not improve significantly (27% [15% to 30%] to 32% [15% to 45%]). Prior to the TMR procedure, all 30 patients had a "low risk" or "medium risk" of death according to the Aaronson classification. The 30-day, 1-year, and 2-year survival rates were 83%, 50%, and 47%, respectively. CONCLUSIONS: We conclude that TMR in ischemic cardiomyopathy (LVEF < or = 30%) has a perioperative risk comparable to that for heart transplantation, but there is no improvement of myocardial performance or life expectancy. Therefore, TMR cannot be regarded as a "bridge," or alternative, to transplantation. However, in individual cases with contraindications for transplantation the anti-anginal effect may justify use of the procedure.     

Transmyocardial laser revascularization causes sustained VEGF secretion

Transmyocardial laser revascularization (TMR) using a carbon dioxide (CO(2)) laser has been shown to relieve angina, increase vascular density, and improve myocardial contraction. A study of 28 patients receiving TMR was conducted to monitor vascular endothelial growth factor (VEGF) levels with the goal of clarifying the relationship between TMR, the amelioration of angina, and vascular density. Serum VEGF levels were measured during four periods (preoperative, postoperative, convalescence, and late) in these 28 patients who received sole therapy TMR for un-revascularizable ischemic angina and the levels were compared with the control group consisting of 10 nonischemic thoracotomy patients. Twelve of the 28 patients had previous coronary artery bypass graft(s); 10 had unstable angina, and 1 had an ejection fraction less than 30%. Overall, angina class was reduced from 3.8 +/- 0.9 to 1.0 +/- 0.9 (P < 0.01) at the 1-year follow-up. There were no perioperative mortalities; however, there was one late mortality. The results show that VEGF levels were higher in the convalescence and late periods. Specifically in the late period, VEGF levels in TMR therapy patients surpassed those of the control group and normalized VEGF levels were three times higher in the late period than preoperatively. The sustained VEGF secretion observed in this study may help to explain why CO(2) TMR therapy causes locally increased vascular density and angina relief.     

Transmyocardial revascularization

Transmyocardial revascularization (TMR) is a puncture technique proposed as a solution for patients with coronary artery disease who cannot be efficiently treated with the standard revascularization procedures such as bypass surgery or percutaneous transluminal coronary angioplasty (PTCA). The studies presented in this review have investigated the use of lasers to revascularize ischaemic myocardium. Needle puncture methods are also briefly described. The results from experimental studies are not conclusive but the encouraging clinical reports raise further questions about the mechanism of angina relief.     

Transmyocardial laser revascularization with excimer laser: clinical results at 1 year

BACKGROUND: Transmyocardial laser revascularization, a new strategy for the treatment of diffuse ischemic heart disease, uses laser technology for the theoretical purpose of forming transmyocardial channels in the heart to increase perfusion to ischemic zones. This report summarizes our initial clinical experience with the procedure. METHODS: Excimer transmyocardial laser revascularization was performed in a reversibly ischemic region of the heart in 15 patients. Ischemia and myocardial viability were evaluated by assessment of symptoms and of results of radionuclide single photon emission computed tomography imaging, exercise tolerance testing, and 24-hour Holter monitoring. RESULTS: No adverse events occurred as a result of the laser revascularization, although 1 patient with preoperative ventricular arrhythmias died 48 hours postoperatively as a result of refractory ventricular tachycardia. Angina class decreased significantly from base line values in patients who had undergone the procedure (mean Canadian Cardiovascular Association angina class, 3.5+/-0.5 at base line, 1.6+/-0.6 at 1 month, 1.5+/-0.8 at 3 months, 1.9+/-0.9 at 6 months, 1.8+/-0.8 at 12 months; p<0.002), and nitroglycerin requirements were similarly decreased in patients who had undergone laser revascularization (mean g/wk of sublingual nitroglycerin, 19+/-4 at baseline, 5+/-3 at 1 month, 4+/-2 at 3 months, 4+/-2 at 6 months, 2+/-1 at 12 months; p<0.02). Exercise tolerance testing demonstrated increase in exercise duration compared with base line values (mean minutes, 7.4+/-3.1 at base line, 8.0+/-3.9 at 1 month, 8.5+/-4.4 at 3 months, and 9.0+/-3.9 at 12 months; p>0.05); those increases were not large enough to be statistically significant, however. CONCLUSIONS: Our data are consistent with the concept that excimer transmyocardial laser revascularization in individuals with significant ischemic heart disease appears to be well tolerated, can be performed safely, and may lead to a reduction in ischemic symptomatology.     

Transmyocardial laser revascularization: early results and 1-year follow-up

BACKGROUND: Transmyocardial revascularization using a high-energy CO2 laser has emerged as a new therapeutic option for patients with severe diffuse coronary artery disease refractory to conventional modes of therapy. METHODS: From December 1994 to September 1997, 102 patients underwent isolated transmyocardial revascularization. The mean age was 56.7 +/- 9.2 years and 92.15% were men. Mean preoperative angina class and ejection fraction were 2.6 +/- 0.7 and 44.7% +/- 10.5%, respectively. Diabetes was present in 49.01% of patients, 32.3% had history of previous myocardial infarction, and 12.7% had undergone a previous coronary artery bypass graft procedure. An average number of 23 +/- 8 channels were created in each patient using an 800-W CO2 laser. RESULTS: The early mortality was 14.7% and univariate predictors of mortality were age more than 55 years, female sex, creatine kinase more than 1,600 IU, absence of intercoronary collaterals, and mean pulmonary artery pressure greater than 21 mm Hg. At 1-year follow-up there was significant improvement in angina class and effort tolerance but no significant change in left ventricular ejection fraction. CONCLUSIONS: We conclude that transmyocardial revascularization provides symptomatic benefit and improves exercise tolerance in a group of patients suffering from disabling angina not amenable to other modes of treatment. The high early mortality can be brought down with strict patient selection criteria. The mechanism of beneficial effects is uncertain and patency of laser channels is controversial, but laser-induced neoangiogenesis is being looked on as a possible explanation.     

Transmyocardial laser revascularization: experimental studies in healthy porcine myocardium

Background. Clinical studies have demonstrated a significant reduction of cardiac index shortly after transmyocardial laser revascularization in patients with low ejection fraction. We analyzed the influence of transmyocardial laser revascularization on healthy myocardium in pigs.

Methods. Carbon dioxide channels were created in 20 pigs which were observed for 6 hours. Ten pigs received one laser channel and ten pigs two laser channels per cm² in the left anterior descending artery region. Seven pigs served as controls. Perfusion (microspheres), function, histochemical, and histologic assessments were subsequently performed.

Results. A significant deterioration of left ventricular stroke work index was observed shortly after transmyocardial laser revascularization in both laser groups (p < 0.05). After 6 hours the left ventricular stroke work index did not increase and showed significantly reduced values at rest (p < 0.05) and during stress in the laser groups (p < 0.01). Normal regional perfusion, small ischemic and necrotic areas, open laser channels in the left anterior descending artery region and significantly increased myocardial water content were observed in the laser groups (p < 0.01).

Conclusions. Carbon dioxide laser channels significantly decrease global heart function shortly after transmyocardial laser revascularization in healthy porcine myocardium. This myocardial tissue showed no recovery 6 hours postoperatively.     

Transmyocardial laser revascularization in the treatment of myocardial ischemia.

Since 1990, over five thousand patients worldwide have undergone transmyocardial laser revascularization (TMR) for the treatment of myocardial ischemia due to end-stage coronary artery disease. Recently four prospective randomized controlled clinical trials have reported their results in comparing TMR to maximal medical therapy. All of the trials demonstrated that TMR provided notable relief of angina when compared to medical management. Additional objective data in the form of exercise tolerance and myocardial perfusion scanning are used to support the symptomatic improvement. Although the trials are similar, they are not identical, and this review provides an update and comparison of their results.     

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 as an adjunct to coronary artery bypass grafting

Many patients with angina related to coronary artery disease respond to medical management or can be completely revascularized using available percutaneous coronary interventions or coronary artery bypass grafting (CABG). There is evidence, however, to indicate that up to 25% of patients are incompletely revascularized following CABG and that incomplete revascularization is a significant independent predictor of early and late mortality and adverse events. Transmyocardial revascularization (TMR) is a surgical option for patients with debilitating angina due to coronary artery disease in areas of the heart not amenable to complete revascularization using conventional treatments. In randomized, 1-year controlled trials with long-term follow-up and in additional clinical experience, TMR performed adjunctively to CABG in patients who would be incompletely revascularized by CABG alone has yielded significantly improved clinical outcomes. Based on these published results, the Society of Thoracic Surgeons has issued a practice guideline recommending adjunctive TMR in this difficult patient group.     

Transmyocardial revascularization using an XeCl excimer laser: results of a randomized trial

Background

CO₂ and holmium:yttrium aluminum garnet (YAG) transmyocardial laser revascularization (TMLR) are used to treat patients with refractory angina. A randomized trial to investigate the efficacy and safety of XeCl excimer TMLR was performed.

Methods

Thirty patients with refractory angina were randomized in pairs to excimer TMLR or maximal medication. We assessed angina, quality of life (QOL), exercise time, myocardial perfusion, and ventricular wall motion at base line and at 3, 6, and 12 months after TMLR.

Results

TMLR patients manifested a significantly better outcome with respect to angina class and quality of life. One TMLR patient died perioperatively versus none in the control group. After TMLR angina decreased from class 3.8 ± 0.4 at base line to 1.9 ± 0.9 at 12 months versus 3.9 ± 0.3 to 3.7 ± 0.6 in the control group, respectively (p = 0.000001). At 12 months a decrease of greater than or equal to two angina classes was indicated in 11 out of 14 TMLR patients versus none in the control group (p = 0.00001). Improved myocardial perfusion or exercise time was not indicated despite a small decrease in reversible wall motion abnormality score.

Conclusions

Excimer TMLR significantly relieves angina and improves QOL without evidence of improved cardiac perfusion or function.     

Transmyocardial laser revascularization as sole reoperative therapy following late anginal recurrence: case report

A case of recurrent angina 3 years following sole therapy transmyocardial laser revascularization (TMR) is described. Repeat sole therapy TMR with the Holmium:YAG system was performed and resulted in complete and immediate angina relief. Repeat TMR should be considered in patients with angina recurrence who underwent primary TMR.