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

Guidelines for the Clinical Use of Transmyocardial Laser Revascularization

Patients with chronic, severe angina refractory to medical therapy who cannot be completely revascularized with either percutaneous catheter intervention or coronary artery bypass graft surgery (CABG) are clinically challenging. Transmyocardial laser revascularization (TMR), as sole therapy or as an adjunct to CABG, may be appropriate therapy for these patients. The recommendations are based on a review of the available evidence including expert consensus opinions. The author follows the format of the American Heart Association and the American College of Cardiology guidelines for diagnostic and therapeutic procedures. There are class I indications for sole therapy TMR and class IIA indications for TMR as an adjunct to CABG. TMR is indicated for selected patients: as sole therapy for a subset of patients with refractory angina. It also may be effective as an adjunct to CABG for a subset of patients with angina who cannot be completely revascularized surgically.

A Blinded, Randomized, Placebo-Controlled Trial of Percutaneous Laser Myocardial Revascularization to Improve Angina Symptoms in Patients With Severe Coronary Disease

OBJECTIVES

This study was a randomized, patient- and evaluator-blinded, placebo-controlled trial in patients treated using percutaneous myocardial laser revascularization.

BACKGROUND

Previous studies using similar therapies have been confounded by placebo bias.

METHODS

A total of 298 patients with severe angina were randomly assigned to receive low-dose or high-dose myocardial laser channels or no laser channels, blinded as a sham procedure. The primary end point was the change in exercise duration from baseline examination to six months.

RESULTS

The incidence of 30-day death, stroke, myocardial infarction, coronary revascularization, or left ventricular perforation occurred in two patients in the placebo, eight patients in the low-dose, and four patients in the high-dose groups (p = 0.12); 30-day myocardial infarction incidence was higher in patients receiving either low-dose or high-dose laser (nine patients) compared with placebo (no patients, p = 0.03). At six months, there were no differences in the change in exercise duration between those receiving a sham (28.0 s, n = 100), low-dose laser (33.2 s, n = 98), or high-dose laser (28.0 s, n = 98, p = 0.94) procedure. There were also no differences in the proportion of patients improving to better than Canadian Cardiovascular Society class III angina symptoms at six months. The follow-up visual summed stress single-photon-emission computed tomography scores were not significantly different from baseline in any group and were no different between groups. The modest improvement in angina symptoms assessed by the Seattle Angina Questionnaire also was not statistically different among the arms.

CONCLUSIONS

Treatment with percutaneous myocardial laser revascularization provides no benefit beyond that of a similar sham procedure in patients blinded to their treatment status.

Transmyocardial Revascularization

Low-powered lasers were first used in the 1980s to produce transventricular channels as an adjunct to coronary artery bypass surgery. High-powered lasers, which were introduced in the 1990s, are powerful enough to create transmyocardial channels with minimal damage to surrounding tissues. Clinical studies were first carried out in patients with inoperable coronary artery disease and angina pectoris refractory to medical therapy. Based on these studies, the Food and Drug Administration granted approval of transmyocardial revascularization (TMR) as a sole therapy. Recently, TMR has been combined with coronary artery bypass surgery and 2 types of laser systems are currently available which have not been compared. The results of clinical trials provide contrasting findings regarding benefit, and the procedure is associated with potential morbidity and mortality risk. Furthermore, the mechanism of action of TMR remains undefined. Additional studies need to be done with TMR to assess whether it is a useful treatment or an addition to the list of placebo therapies initially thought to have been of benefit in the therapy for angina pectoris.

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.

The Society of Thoracic Surgeons practice guideline series: transmyocardial laser revascularization

BACKGROUND

Patients with chronic severe angina refractory to medical therapy who cannot be completely revascularized with either percutaneous catheter intervention or coronary artery bypass graft surgery present clinical challenges. Transmyocardial laser revascularization, either as sole therapy or as an adjunct to coronary artery bypass graft surgery, may be appropriate for some of these patients. Although transmyocardial revascularization has consistently been demonstrated as an efficacious means of relieving angina, the mechanism of its effects are still debated, and criteria for the selection of patients for this novel therapy have not been adequately defined.

METHODS

We reviewed the available evidence to allow us to make recommendations for the appropriate therapeutic applications of transmyocardial revascularization following the format of the American Heart Association and the American College of Cardiology guidelines for diagnostic and therapeutic procedures. Our recommendations were classified as class I, IIA, IIB, or III. For each recommendation we defined the level of supporting evidence as A, B, or C.

RESULTS

We identified class I indications for transmyocardial revascularization as sole therapy and class IIA indications for transmyocardial revascularization as an adjunct to coronary artery bypass graft surgery with levels of evidence A and B, respectively.

CONCLUSIONS

Transmyocardial laser revascularization may be an acceptable form of therapy for selected patients: as sole therapy for a subset of patients with refractory angina and as an adjunct to coronary artery bypass graft surgery for a subset of patients with angina who cannot be completely revascularized surgically.

Cardiac denervation after clinical transmyocardial laser revascularization: short-term and long-term iodine 123–labeled meta-iodobenzylguanide scintigraphic evidence

OBJECTIVES

This study was designed to investigate whether transmyocardial laser revascularization induces myocardial denervation and to correlate this with myocardial perfusion and clinical status.

METHODS

Transmyocardial laser revascularization was performed with a Holmium:YAG (n = 3) or xenon chloride excimer laser (n = 5). Preoperative and postoperative iodine 123-labeled meta-iodobenzylguanide SPECT scintigraphy to assess cardiac innervation and perfusion scintigraphy were also performed. Furthermore, New York Heart Association functional angina class and quality of life were assessed.

RESULTS

In all patients postoperative iodine 123-labeled meta-iodobenzylguanide SPECT showed significantly decreased uptake and therefore sympathetic myocardial denervation at up to 16 months' follow-up (average preoperative and postoperative summed defect scores of 14.8 +/- 5.3 and 24.5 +/- 4.2, respectively; P =.00005). In 86% of segments, the decreased meta-iodobenzylguanide uptake could be correlated to the treated area. In all patients angina was reduced by 2 or more classes at 12 months' follow-up, and quality of life improved significantly.

CONCLUSIONS

Transmyocardial laser revascularization-induced improvement of angina and quality of life can be explained by destruction of nociceptors or cardiac neural pathways, changing the perception of anginal pain.

Improved quality of life after XeCl excimer transmyocardial laser revascularization: results of a randomized trial

BACKGROUND AND OBJECTIVES

We assessed quality of life (QOL) after XeCl transmyocardial laser revascularization (TMLR).

STUDY DESIGN/MATERIALS AND METHODS

Thirty patients were randomized to receive XeCl excimer TMLR or optimal cardiac medication (controls). QOL was assessed at baseline, 1, 3, 6, and 12 months using three different questionnaires: The Medical Outcomes Study Short Form-24 (MOS SF-24), the EuroQol Standardized Questionnaire, and the Seattle Angina Questionnaire (SAQ). The primary outcome measure was the change in score between baseline and 12 months.

RESULTS

TMLR patients scored significantly better compared to controls in the MOS SF-24 social functioning, energy, general health, and bodily pain domains, in the EuroQol usual activity domain and the EuroQol Visual Analogue Scale, and in the SAQ physical limitation, angina frequency and disease perception domains.

CONCLUSIONS

QOL significantly improved after XeCl excimer TMLR compared to medication. These results are similar to reported improvements in QOL after CO(2) and Ho:YAG TMLR.

Myocardial laser revascularization for the treatment of end-stage coronary artery disease

Myocardial laser revascularization is a novel therapeutic technique aimed at delivering oxygenated blood via a series of channels to the ischemic regions of the heart. These channels may be created surgically or via a less invasive percutaneous approach. In patients with end-stage coronary artery disease, both transmyocardial laser revascularization (TMR) and percutaneous myocardial laser revascularization (PMR) have been associated with a reduction in symptoms, improved exercise tolerance, and enhanced quality of life. However, the mechanism of action of laser therapy is incompletely understood, the results of objective cardiac perfusion measurements are inconclusive, and multiple randomized trials have failed to demonstrate an increase in survival. In addition, the positive results seen in TMR trials have been questioned because of a lack of blinding, raising the possibility that the benefit may have been due to the placebo effect. Finally, two recent sham-controlled, randomized clinical trials of PMR have not shown any benefit of the procedure, but instead have highlighted the important role of the placebo effect in the response to PMR. Further research is, therefore, needed to elucidate the value of myocardial laser revascularization.

Transmyocardial laser revascularization dose response: enhanced perfusion in a porcine ischemia model as a function of channel density

BACKGROUND

Transmyocardial laser revascularization (TMR) appears to provide symptomatic relief to patients with ischemic heart disease, but evidence that TMR enhances perfusion to ischemic myocardium remains limited. Furthermore, it is uncertain whether there exists a TMR dose-response relationship that is a function of channel number. We therefore compared restoration of blood flow as analyzed by rest and stress 99mTc-sestamibi scans and histologic grading of neovascularization after 50-channel, 25-channel, or 10-channel TMR using the excimer laser in an established model of porcine myocardial ischemia.

METHODS

Yorkshire swine underwent a thoracotomy and placement of an ameroid constrictor around the proximal circumflex coronary artery. Three weeks later, the animals underwent resting and adenosine stress 99mTc-sestamibi scans for evaluation of ischemia immediately before repeat thoracotomy and TMR with either 50 channels (n = 4), 25 channels (n = 4), or 10 channels (n = 4) in the circumflex territory. The animals underwent repeat perfusion analyses 4 weeks later, after which the animals were sacrificed and the hearts were perfusion fixed for histologic evaluation of neovascularization.

RESULTS

All animals survived to sacrifice. Semiquantitative analyses of the sestamibi perfusion scans 4 weeks after lasing demonstrated significant improvement (p < 0.04) in stress-induced ischemia in the 50-channel TMR animals, but not in the 25- or 10-channel TMR groups, as compared with scans obtained immediately before lasing. A computerized image analysis of perfusion scans similarly demonstrated an improvement in the area of ischemia of 42% +/- 22% in the scans obtained 4 weeks after lasing compared with scans obtained immediately before lasing in the 50-channel group (p < 0.004), but only a 12% +/- 9% improvement in the 25-channel group and an 8% +/- 4% improvement in the 10-channel group (p > 0.05). Histologic assessment of neovascularization demonstrated significantly greater number of microvessels per low-power field in the 50- versus the 25- and 10-channel groups (p < 0.001).

CONCLUSIONS

In an animal model of myocardial ischemia, TMR appears to enhance myocardial perfusion. A dose-response relationship related to channel number may be of significance when evaluating the efficacy of various treatment strategies.