Myocardial revascularization with laser. Preliminary findings

Long-term results of isolated transmyocardial laser revascularization in combination with the intramyocardial autologous bone marrow stem cells injection

To evaluate the long-term results of TMLR using a CO² laser in combination with intramyocardial injection of ABMSC as an isolated procedure in patients with the end-stage coronary artery disease, the study included 20 patients (90% male), with a mean age of 58.4 ± 8.7 years. To assess the long-term results, patients were examined in a hospital. The Minnesota Living with Heart Failure Questionnaire (MLHFQ) and the Seattle Angina Questionnaire (SAQ) were used. The evolution of laboratory and instrumental indices, as well as medical therapy, was assessed. The end points of the study were death, acute myocardial infarction (AMI), repeated myocardial revascularization, recurrent hospitalizations due to coronary artery disease, and stroke. The changes in angina functional class were also evaluated. The median of follow-up period was 54 (36; 83) months, that is, 4.5 years. The analysis of the evolution of echocardiographic data showed the absence of statistically significant changes in the following parameters: left ventricular end-diastolic diameter (EDD) (p = 0.967), end-systolic diameter (ESD) (p = 0.204), end-diastolic volume (EDV) (p = 0.852), end-systolic volume (ESV) (p = 0.125), and left ventricular ejection fraction (LVEF) (p = 0.120). The patients continued to regularly take the main groups of medications. Nitrate consumption was significantly reduced (p < 0.001). Significant positive dynamics were observed in the changes in angina functional class. At the baseline, all patients had angina III FC, in the long term, 3 patients had II FC, 11 patients had I FC, and 6 patients had no angina. Clinical outcomes (mortality, recurrent myocardial infarction, stroke) were absent during the follow-up period. There were two cases of repeated myocardial revascularization. Regression analysis revealed that SYNTAX score was associated with the clinical outcome "repeated revascularization." TMLR in combination with intramyocardial injection of ABMSC is a safe method to achieve a statistically significant antianginal effect and reduce the need for "nitrates," which in turn improves the quality of life and reduces the frequency of hospitalizations due to coronary artery disease. These results can be achieved with strict adherence to the certain indications for the intervention.

Refractory Angina: the Current State of Mechanical Therapies

PURPOSE OF REVIEW

Refractory angina (RA), which is characterized by tissue ischemia along with neurological, mitochondrial, and psychogenic dysfunction, is becoming a major cause of morbidity in patients with advanced coronary artery disease. In this review, we discuss in detail the invasive mechanical non-cell therapy-based options, the evidence behind these therapies, and future trends.

RECENT FINDINGS

There is extensive ongoing research in the areas of spinal-cord stimulation, transmyocardial laser revascularization, sympathectomy, angiogenesis, and other non-cell-based therapies to explore the best therapy for refractory angina. There is conflicting data in the literature suggesting subjective improvement in angina, but very few studies boast improvement in core objective parameters such as myocardial blood flow, survival, or rehospitalizations. Patients with refractory angina are a complex group of patients that need novel approaches to help alleviate their symptoms and reduce mortality. A carefully selected sequence of therapies may provide the best results in this patient population.

Clinical outcomes meta-analysis: measuring subendocardial perfusion and efficacy of transmyocardial laser revascularization with nuclear imaging

INTRODUCTION

Randomized and nonrandomized clinical trials have tried to assess whether or not TMR patients experience an increase in myocardial perfusion. However there have been inconsistencies reported in the literature due to the use of different nuclear imaging modalities to test this metric. The primary purpose of this meta-analysis was to determine whether SPECT, MUGA and PET scans demonstrate changes in myocardial perfusion between lased and non-lased subjects and whether laser type affects myocardial perfusion. The secondary purpose was to examine the overall effect of laser therapy on clinical outcomes including survival, hospital re-admission and angina reduction.

METHODS

Sixteen studies were included in the primary endpoint analysis after excluding all other non-imaging TMR papers. Standardized mean difference was used as the effect size for all quantitative outcomes and log odds ratio was used as the effect size for all binary outcomes.

RESULTS

Statistically significant improvements in myocardial perfusion were observed between control and treatment groups in myocardial perfusion at 6-month follow up using PET imaging with a porcine model. However non-significant differences were observed in patients at 3 and 12 months using SPECT, PET or MUGA scans. Both CO₂ and Ho:YAG laser systems demonstrated an increase in myocardial perfusion however this effect was not statistically significant. In addition both laser types displayed statistically significant decreases in patient angina at 3, 6 and 12 months but non-significant increases in survival rates and decreases in hospital re-admissions.

CONCLUSION

In order to properly assess myocardial perfusion in TMR subjects, subendocardial perfusion needs to be analyzed via nuclear imaging. PET scans can provide this level of sensitivity and should be utilized in future studies to monitor and detect perfusion changes in lased and non-lased subjects.

Association between High Endocardial Unipolar Voltage and Improved Left Ventricular Function in Patients with Ischemic Cardiomyopathy

We know that endocardial mapping reports left ventricular electrical activity (voltage) and that these data can predict outcomes in patients undergoing traditional revascularization. Because the mapping data from experimental models have also been linked with myocardial viability, we hypothesized an association between increased unipolar voltage in patients undergoing intramyocardial injections and their subsequent improvement in left ventricular performance. For this exploratory analysis, we evaluated 86 patients with left ventricular dysfunction, heart-failure symptoms, possible angina, and no revascularization options, who were undergoing endocardial mapping. Fifty-seven patients received bone marrow mononuclear cell (BMC) injections and 29 patients received cell-free injections of a placebo. The average mapping site voltage was 9.7 ± 2 mV, and sites with voltage of ≥6.9 mV were engaged by needle and injected (with BMC or placebo). For all patients, at 6 months, left ventricular ejection fraction (LVEF) improved, and after covariate adjustment this improvement was best predicted by injection-site voltage. For every 2-mV increase in baseline voltage, we detected a 1.3 increase in absolute LVEF units for all patients (P=0.038). Multiple linear regression analyses confirmed that voltage and the CD34(+) count present in bone marrow (but not treatment assignment) were associated with improved LVEF (P=0.03 and P=0.014, respectively). In an exploratory analysis, higher endocardial voltage and bone marrow CD34(+) levels were associated with improved left ventricular function among ischemic cardiomyopathy patients. Intramyocardial needle injections, possibly through stimulation of angiogenesis, might serve as a future therapy in patients with reduced left ventricular function and warrants investigation.

Transmyocardial Revascularization: Peril and Potential

Transmyocardial laser revascularization is a technique for the treatment of patients with chronic angina pectoris that is refractory to medical therapy and who are not eligible for surgical intervention. Percutaneous myocardial revascularization is a less-invasive catheter-based procedure that has been adapted from transmyocardial laser revascularization. Six prospective randomized clinical trials have been performed with transmyocardial laser revascularization and 5 have been performed using percutaneous myocardial revascularization. All of the transmyocardial laser revascularization and 4 of the percutaneous myocardial revascularization studies showed a significant improvement in angina class; however, results for improved survival, increased exercise tolerance, improved ejection fraction, and improved myocardial perfusion were less definitive. Transmyocardial laser revascularization has significant potential for morbidity and mortality. This article summarizes the results of the randomized trials, explains the current theories for the mechanism of transmyocardial laser revascularization, and discusses its current role in treatment for patients, considering the evidence that currently exists.

Transmyocardial laser revascularization versus medical therapy for refractory angina

BACKGROUND

This is an update of a review previously published in 2009. Chronic angina and advanced forms of coronary disease are increasingly more frequent. In spite of the improvement in the efficacy of available revascularization treatments, a subgroup of patients continue suffering from refractory angina. Transmyocardial laser revascularization (TMLR) has been proposed to improve the clinical situation of these patients.

OBJECTIVES

To assess the effects (both benefits and harms) of TMLR versus optimal medical treatment in people with refractory angina who are not candidates for percutaneous coronary angioplasty or coronary artery bypass graft, in alleviating angina severity, reducing mortality and improving ejection fraction.

SEARCH METHODS

We searched the following resources up to June 2014: the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, the metaRegister of Controlled Trials database, ClinicalTrials.gov, and the WHO International Clinical Trials Registry. We applied no languages restrictions. We also checked reference lists of relevant papers.

SELECTION CRITERIA

We selected studies if they fulfilled the following criteria: randomized controlled trials (RCTs) of TMLR, by thoracotomy, in patients with Canadian Cardiovascular Society or New York Heart Association angina grade III-IV who were excluded from other revascularization procedures.

DATA COLLECTION AND ANALYSIS

Three authors independently extracted data for each trial about the population and interventions compared and assessed the risk of bias of the studies, evaluating randomisation sequence generation, allocation concealment, blinding (of participants, personnel and outcome assessors), incomplete outcome data, selective outcome reporting, and other potential sources of bias.

MAIN RESULTS

From a total of 502 references, we retrieved 47 papers for more detailed evaluation. We selected 20 papers, reporting data from seven studies, which included 1137 participants, of which 559 were randomized to TMLR. Participants and professionals were not blinded, which suggests high risk of performance bias. Overall, 43.8% of participants in the treatment group decreased two angina classes, as compared with 14.8% in the control group: odds ratio (OR) 4.63, 95% confidence interval (CI) 3.43 to 6.25), and heterogeneity was present. Mortality by intention-to-treat analysis was similar in both groups at 30 days (4.0% in the TMLR group and 3.5% in the control group), and one year (12.2% in the TMLR group and 11.9% in the control group). However, the 30-day mortality as-treated was 6.8% in the TMLR group and 0.8% in the control group (pooled OR was 3.76, 95% CI 1.63 to 8.66), mainly due to a higher mortality in participants crossing from standard treatment to TMLR. The assessment of subjective outcomes, such as improvement in angina, was affected by a high risk of bias and this may explain the differences found. Other adverse events such as myocardial infarction, arrhythmias or heart failure, were not considered in this review, as they were not predefined outcomes in trials design and they show a high inconsistency across studies. No new trials on transmyocardial laser revascularization have been published in the last ten years and it is very unlikely that new research will be undertaken in this field.

AUTHORS' CONCLUSIONS

This review shows that risks associated with TMLR outweigh the potential clinical benefits. Subjective outcomes are subject to high risk of bias and no differences were found in survival, but a significant increase in postoperative mortality and other safety outcomes suggests that the procedure may pose unacceptable risks.

Transmyocardial revascularization devices: technology update

Transmyocardial laser revascularization (TMR) emerged as treatment modality for patients with diffuse coronary artery disease not amendable to percutaneous or surgical revascularization. The procedure entails the creation of laser channels within ischemic myocardium in an effort to better perfuse these areas. Currently, two laser devices are approved by the US Food and Drug Administration for TMR – holmium:yttrium–aluminum–garnet and CO₂. The two devices differ in regard to energy outputs, wavelengths, ability to synchronize with the heart cycle, and laser–tissue interactions. These differences have led to studies showing different efficacies between the two laser devices. Over 50,000 procedures have been performed worldwide using TMR. Improvements in angina stages, quality of life, and perfusion of the myocardium have been demonstrated with TMR. Although several mechanisms for these improvements have been suggested, evidence points to new blood vessel formation, or angiogenesis, within the treated myocardium, as the major contributory factor. TMR has been used as sole therapy and in combination with coronary artery bypass grafting. Clinical studies have demonstrated that TMR is both safe and effective in angina relief long term. The objective of this review is to present the two approved laser devices and evidence for the safety and efficacy of TMR, along with future directions with this technology.

Protective effects of panax notoginseng saponins on cardiovascular diseases: a comprehensive overview of experimental studies

Panax notoginseng saponins (PNS) are one of the most important compounds derived from roots of the herb Panax notoginseng which are traditionally used as a hemostatic medicine to control internal and external bleeding in China for thousands of years. To date, at least twenty saponins were identified and some of them including notoginsenoside R1, ginsenoside Rb1, and ginsenoside Rg1 were researched frequently in the area of cardiovascular protection. However, the protective effects of PNS on cardiovascular diseases based on experimental studies and its underlying mechanisms have not been reviewed systematically. This paper reviewed the pharmacology of PNS and its monomers Rb1, Rg1, and R1 in the treatment for cardiovascular diseases.

Does laser type impact myocardial function following transmyocardial laser revascularization?

BACKGROUND

Transmyocardial laser revascularization (TMR) is currently clinically performed with either a CO(2) or Ho:YAG laser for the treatment of severe angina. While both lasers provide symptomatic relief, there are significant differences in the laser-tissue interactions specific to each device that may impact their ability to enhance the perfusion of myocardium and thereby improve contractile function of the ischemic heart.

METHODS

A porcine model of chronic myocardial ischemia was employed. After collecting baseline functional data with cine magnetic resonance imaging (MRI) and dobutamine stress echo (DSE), 14 animals underwent TMR with either a CO(2) or Ho:YAG laser. Transmural channels were created with each laser in a distribution of 1/cm(2) in the ischemic zone. Six weeks post-treatment repeat MRI as well as DSE were obtained after which the animals were sacrificed. Histology was preformed to characterize the laser-tissue interaction.

RESULTS

CO(2) TMR led to improvement in wall thickening in the ischemic area as seen with cine MRI (40.3% vs. baseline, P < 0.05) and DSE (20.2% increase vs. baseline, P < 0.05). Ho:YAG treated animals had no improvement in wall thickening by MRI (-11.6% vs. baseline, P = .67) and DSE (-16.7% vs. baseline, P = 0.08). Correlative semi-quantitative histology revealed a significantly higher fibrosis index in Ho:YAG treated myocardium versus CO(2) (1.81 vs. 0.083, P < 0.05).

CONCLUSIONS

In a side-by-side comparison CO(2) TMR resulted in improved function of ischemic myocardium as assessed by MRI and echocardiography. Ho:YAG TMR led to no improvement in regional function likely due to concomitant increase in fibrosis in the lasered area.

Transmyocardial laser revascularization versus medical therapy for refractory angina

BACKGROUND

Chronic angina and advanced forms of coronary disease are increasingly more frequent. Although the improved efficacy of available revascularization treatments, a subgroup of patients present with refractory angina. Transmyocardial laser revascularization (TMLR) has been proposed to improve the clinical situation of these patients.

OBJECTIVES

To assess the efficacy and safety of TMLR versus optimal medical treatment in patients with refractory angina in alleviating the severity of angina and improving survivorship and heart function.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials on The Cochrane Library (Issue 2 2007), MEDLINE (January 2006 to June 2007), EMBASE ( 2004 to June 2007) and ongoing studies were sought using the metaRegister of Controlled Trials database (mRCT) and ClinicalTrials.gov databases. No languages restrictions were applied. Reference lists of relevant papers were also checked.

SELECTION CRITERIA

Studies were selected if they fulfilled the following criteria: randomized controlled trials of TMLR, by thoracotomy, in patients with angina grade III-IV who were excluded from other revascularization procedures. From a total of 181 references, 20 papers were selected, reporting data from seven studies.

DATA COLLECTION AND ANALYSIS

Two reviewers abstracted data from selected papers; . The reviewers performed independently both quality assessment and data extraction. Selected studies present methodological weaknesses. None of them fulfilled all the quality criteria.

MAIN RESULTS

Seven studies (1137 participants of which 559 randomized to TMLR) were included. Overall, 43.8 % of patients in the treatment group decreased two angina classes as compared with 14.8 % in the control group, odds ratio (OR) of 4.63 (95% confidence interval (CI) 3.43 to 6.25), and heterogeneity was statistically significant. Mortality by intention-to-treat analysis at both 30 days (4.0 % in the TMLR group and 3.5 % in the control group) and 1 year (12.2 % in the TMLR group and 11.9 % in the control group) was similar in both groups. The 30-days mortality as treated was 6.8% in TMLR group and 0.8% in the control group, showing a statistically significant difference. The pooled OR was 3.76 (95% CI 1.63 to 8.66), because of the higher mortality in patients crossing from standard treatment to TMLR.

AUTHORS' CONCLUSIONS

There is insufficient evidence to conclude that the clinical benefits of TMLR outweigh the potential risks. The procedure is associated with a significant early mortality.

Transmyocardial laser revascularization

It has been almost a decade since transmyocardial laser revascularization (TMR) was approved for clinical use in the United States. The safety of TMR was demonstrated initially with nonrandomized studies in which TMR was used as the only treatment for patients with severe angina. TMR efficacy was proven after multiple randomized controlled trials. These revealed significant angina relief compared to maximum medical therapy in patients with diffuse coronary disease not amenable to conventional revascularization. In light of these results, TMR has been used as an adjunct to coronary artery bypass grafting (CABG). By definition, patients treated with this combined therapy have more severe coronary disease and comorbidities that are associated with end-stage atherosclerosis. Combination CABG + TMR has resulted in symptomatic improvement without additional risk. The likely mechanism whereby TMR has provided benefit is the angiogenesis engendered by the laser-tissue interaction. Improved perfusion and concomitant improvement in myocardial function have been observed post-TMR. Additional therapies to enhance the angiogenic response include combining TMR with stem cell-based treatments, which appear to be promising future endeavors.

Transmyocardial revascularization ameliorates ischemia by attenuating paradoxical catecholamine-induced vasoconstriction

BACKGROUND

The mechanism by which transmyocardial revascularization (TMR) offers clinical benefit is controversial. We hypothesized that TMR ameliorates ischemia by reversing paradoxical catecholamine-induced vasoconstriction.

METHODS AND RESULTS

Chronic ischemic cardiomyopathy was created in 11 dogs by placing ameroid constrictors on the proximal coronary arteries and their major branches. Six weeks later, 35 channels were created percutaneously in the left circumflex artery region, with the left anterior descending artery region serving as control. At rest, wall thickening and myocardial blood flow did not change in the treated region, whereas they deteriorated in the control bed. Contractile and myocardial blood flow reserve increased in the treated region but deteriorated in the control region. There was diminished iodine 123 metaiodobenzylguanidine uptake and a significant reduction in noradrenergic nerves in the treated region compared with the control region, with a corresponding reduction in tissue tyrosine hydroxylase activity.

CONCLUSIONS

We conclude that the absence of a catecholamine-induced reduction in MBF reserve and contractile reserve in the TMR-treated region with associated evidence of neuronal injury indicates that the relief of exercise-induced ischemia after TMR most likely results from reversal of paradoxical catecholamine-induced vasoconstriction. These findings may have implications in selecting patients who would benefit from TMR.

Results of coronary artery endarterectomy and coronary artery bypass grafting for diffuse coronary artery disease

BACKGROUND

Coronary artery endarterectomy with coronary artery bypass grafting for diffuse coronary artery disease has been associated with increased morbidity and mortality. We evaluated our institutional experience to redefine the role of coronary endarterectomy for diffuse coronary artery disease.

METHODS

From 1985 to 2002 isolated coronary artery endarterectomy with coronary artery bypass grafting was performed in 1,478 consecutive patients. The short-term outcomes were compared with concurrent series of conventional coronary artery bypass graft surgery, and risk factors for adverse outcomes after coronary endarterectomy were identified.

RESULTS

Patients in the coronary endarterectomy group were of higher risk with increased incidence of comorbidities and three-vessel coronary disease. The operative mortality (3.2% versus control 2.2%; p = 0.03) and the incidence of major postoperative morbidity (not significant) were comparable between the groups. Prolonged cardiopulmonary bypass time, recent acute myocardial infarction, redo surgery, and poor ventricular function were important predictors of in-hospital mortality. Vessel endarterectomized, technique of endarterectomy, and cardiopulmonary bypass versus off-pump technique did not alter results. At long-term follow-up, 5-year and 10-year survivals were 83% +/- 5%, and 74% +/- 3%, respectively, and freedom from angina at 5 and 10 years was 75% +/- 5%, and 69% +/- 4%, respectively, with 96% of survivors in New York Heart Association class II.

CONCLUSIONS

In selected patients with diffuse coronary artery disease, coronary endarterectomy can be used as a tool for myocardial revascularization. The operative mortality and major morbidity were comparable or similar to coronary artery bypass grafting, and short-term and long-term results were favorable.

Perioperative management of patients undergoing transmyocardial laser revascularization

Advanced revascularization strategies continue to uncover a growing number of patients with symptomatic diffuse coronary artery disease. Transmyocardial laser revascularization (TMR) provides significant benefit in terms of improved quality of life and more complete revascularization for these difficult to treat patients when TMR is used as sole therapy or in combination with coronary artery bypass grafting. The safe clinical application of this important procedure relies on diligent perioperative management with appropriate patient selection, intraoperative care that avoids myocardial ischemia, and postoperative pain control along with expeditious reinstitution of antianginal medications. The treatment paradigms learned with the safe application of TMR should prove useful as new therapies to extend our revascularization options are developed.

Clinical results of sole therapy TMR treatment

The safety and efficacy of transmyocardial laser revascularization (TMR) is best demonstrated by the data collected from several multi-institutional randomized controlled trials. These trials are an important link between the preclinical data and the most common use of TMR (TMR + Coronary Artery Bypass Grafting). In addition to significant symptomatic relief both short- and long-term objective data were also garnered in these studies. A review of the history, study design, and outcomes is provided.

Cardiovascular imaging to quantify the evolution of cardiac diseases in clinical development

Cardiovascular diseases are the leading causes of mortality in western countries, leading to the development of a large set of preventive and curative treatments. Medical imaging is the gold standard to evaluate both cardiac perfusion and cardiac function and can be used even before the advent of hard events to accurately assess treatment effects. This study reviews the different image modalities that can be used to evaluate the evolution of cardiac diseases, especially coronary artery diseases. It also reviews different techniques heavily relying upon image co-registration techniques and population model designs that enable accurate quantitative evaluation of cardiac perfusion and cardiac function through time. It will draw the pros and cons of the different imaging modalities in actual clinical trials: Gated or tagged MRI, MRI for perfusion, PET, SPECT, Gated SPECT, MUGA, Ultrasound. This study also details the latest advances in quantification of cardiac SPECT, which has wide use in clinical trials today.

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.

Coronary endarterectomy: impact on morbidity and mortality when combined with coronary artery bypass surgery

BACKGROUND

The results of coronary endarterectomy (CE) performed in addition to coronary artery bypass grafting (CABG) have been controversial. We aimed to examine the impact of CE performed in addition to CABG when compared with CABG alone in our unit.

METHODS

Patients who had CABG between January 1995 and December 2001 were included. They were divided into two groups, the CABG-only group and CABG and CE group. The following outcomes were compared: perioperative myocardial infarction, postoperative ventricular arrhythmias, cerebrovascular accident, renal impairment, and early mortality.

RESULTS

Of 5,782 patients who underwent CABG, 461 patients (8.6%) required CE in addition to CABG. There was a higher mortality and incidence of postoperative renal impairment in the group of patients who had CABG and CE, with no significant difference in other outcomes. However, the patients in the CABG and CE group had a higher incidence of male sex, previous myocardial infarctions, preoperative renal impairment, and poor left ventricular function, with longer cross-clamp and cardiopulmonary bypass times than in the CABG-only patients. Although female sex, renal impairment, nonelective surgery, impaired left ventricular function, and peripheral vascular disease were associated with increased mortality in all the patients, and use of statins and aspirin was associated with a reduction in mortality, CE was not a predictor of mortality. Furthermore, on propensity scores analysis, CE was not associated with increased mortality.

CONCLUSIONS

Coronary endarterectomy when combined with CABG seemed to be associated with a higher mortality than isolated CABG in our study groups, but this is related to comorbidities of these patients rather than the CE.

Left anterior descending coronary endarterectomy: Early and late results in 196 consecutive patients

BACKGROUND

With advances in percutaneous coronary interventions, many patients now referred for coronary artery bypass grafting have diffuse coronary artery disease. We undertook this retrospective study to determine whether left anterior descending (LAD) coronary endarterectomy is a safe and effective long-term adjunct to coronary artery bypass grafting in patients who cannot otherwise be completely revascularized.

METHODS

Between January 1992 and March 2000, 196 of 7,633 (2.5%) consecutive patients underwent LAD coronary endarterectomy with coronary artery bypass grafting. Median age was 67 years (range, 33 to 97 years), 101 patients (52%) had unstable angina, and 182 (93%) were in New York Heart Association class III or IV. Thirty-three patients (17%) had ongoing myocardial infarction; another 17 (9%) had myocardial infarction less than 1 month. Thirty patients (15%) required intraaortic balloon pump preoperatively and 19 (10%) were reoperations.

RESULTS

All patients underwent LAD endarterectomy with coronary artery bypass grafting to the LAD. The left internal mammary artery was grafted to the LAD in 151 patients (77%), and 46 of 151 (30%) of these required an additional vein patch to the endarterectomized bed. Concomitant valve procedures were performed in 8 (4%) patients. Overall hospital mortality was 3% (6 of 196). Perioperative myocardial infarction in the LAD territory was 3%. One-year survival was 94% (95% confidence interval, 90% to 97%), whereas 5-year survival was 74% (95% confidence interval, 66% to 80%). Freedom from cardiac events (angina, myocardial infarction, congestive heart failure, percutaneous coronary interventions) was 90% (95% confidence interval, 84% to 94%) at 1 year and 84% (95% confidence interval, 75% to 90%) at 5 years.

CONCLUSIONS

Despite the presence of diffuse coronary artery disease, coronary artery bypass grafting with LAD endarterectomy offers excellent results with very low hospital mortality and morbidity, and favorable long-term survival.

Efficacy of transmyocardial laser revascularization and thoracic sympathectomy for the treatment of refractory angina

BACKGROUND

Transmyocardial laser revascularization (TMR) is an effective treatment for relief of refractory angina. This benefit may be mediated by increase in myocardial perfusion or by cardiac denervation. We investigate the efficacy of TMR and thoracic sympathectomy (TS) for relief of angina and whether any clinical benefit is associated with enhanced myocardial perfusion.

METHODS

Twenty consecutive patients with nonrevascularizable coronary arteries and intractable angina were prospectively randomized to have TMR by holmium: yttrium aluminum garnet laser or TS. Subjects were clinically evaluated before, and for 42 months after, surgery. They underwent exercise tolerance testing and rest and stress quantitative perfusion magnetic resonance imaging (MRI) before, and 6 months after surgery.

RESULTS

The demographics of the two groups were similar. There was no perioperative mortality; however, two patients died in the TS group during follow-up. The Canadian Cardiovascular Society angina score improved from 3.4 +/- 0.5 to 2.6 +/- 1.1 (p = 0.06) in the TS group at 6 months but returned to 3.2 +/- 0.7 at 42 months, while in the TMR group it improved from 3.6 +/- 0.5 to 1.9 +/- 0.7 (p = 0.008) at 6 months and deteriorated to 2.5 +/- 0.9 (p = 0.01) after 42 months of surgery. The TMR-treated patients showed significant improvements in the SF-36 scores and Seattle Angina Questionnaire only at 6 months, whereas TS-treated patients did not show amelioration at any time during follow-up. The MRI protocol was completed in 15 of 20 (TMR = 8; TS = 7) patients and no significant differences in qualitative or quantitative perfusion variables were demonstrated in either group.

CONCLUSIONS

A greater clinical benefit was obtained with TMR than with TS early after surgery but this clinical effect did not seem to be associated with improvement in myocardial perfusion as assessed by MRI and part of the beneficial effect was lost by 42 months after surgery.

[Long-term results of percutaneous transmyocardial laser revascularization therapy at the University of Vienna Medical Center]

INTRODUCTION

Percutaneous transmyocardial laser revascularization (PTMR) was used for treating patients with therapy refractory angina pectoris who are not amenable for angioplasty or bypass surgery ("no-option patients"). The aim of this study was to evaluate the short- and long-term results of PTMR-interventions performed at the University of Vienna between February 1999 and May 2000.

PATIENTS AND METHODS

Twenty-four "no-option" patients underwent PTMR. The chronically ischemic myocardial areas were determined by perfusion scintigraphy; after coronary angiography and contrast ventriculography 10 patients were treated with the Biosense laser using 3D-NOGA-mapping guidance and 14 patients with the Eclipse laser using biplane fluoroscopic guidance. After an average follow-up period (FUP) of 7.7 +/- 4.2 months, all patients underwent perfusion scintigraphy, coronary angiography and contrast ventriculography. Global and regional left ventricular (LV) function were calculated by the area-length method.

RESULTS

The ischemic myocardial areas of the patients were treated with an average of 16 laser points. In one patient, an intramural hematoma caused by the Biosense laser catheter was observed, in another patient the ventricular wall was perforated by the Eclipse laser (both events were resolved conservatively); during the in-hospital stay 2 patients suffered from severe angina pectoris and in one patient a pacemaker was implanted. During the 7-month-FUP one patient had a myocardial infarction; in one patient a stent implantation, in another one coronary bypass surgery had to be performed (in not-lasered areas), 2 patients died. Thus, the composite MACE rate was 33.3%. Angina class improved significantly during the FUP, but a trend to deterioration of global ejection fraction was observed. The rest and late rest myocardial perfusion remained unchanged.

CONCLUSION

While the angina class of the patients improved significantly, no significant change of myocardial perfusion but a trend to deterioration of LV function after the FUP were observed.

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.

Evaluation of myocardial perfusion and left ventricular function six months after percutaneous transmyocardial laser revascularization: Comparison of two Ho-YAG laser systems with the same wavelength, but different energy delivery and navigation systems

BACKGROUND AND OBJECTIVES

Myocardial perfusion and left ventricular function (LVF) were assessed after percutaneous transmyocardial laser revascularization (PTMR) in patients not amenable to conventional revascularization, with a comparison of two laser systems.

STUDY DESIGN/MATERIALS AND METHODS

PTMR was performed with an Eclipse laser in 15 patients, and with a Biosense DMR in 10 patients. (201)Thallium scintigraphy, coronary angiography, and ventriculography were performed at baseline and at the 7.5+/-4.3-month follow-up. All patients in the Biosense DMR group and 10 in the Eclipse group underwent NOGA mapping before PTMR and after follow-up.

RESULTS

The event-free survival rates were comparable, and the angina scores of all patients improved significantly, but more so in the Biosense DMR group than in the Eclipse group (1.2+/-1.1 vs. 2.3+/-0.9, P < 0.05). Both, the electrical activity assessed by NOGA mapping and the normalized (201)thallium uptake at redistribution improved significantly in the treated segments after Biosense DMR, while the global LVF decreased insignificantly in the Eclipse group.

CONCLUSIONS

PTMR resulted in significant improvements in the clinical symptoms, but the electrical activity improved only in the Biosense DMR group, without transforming to a better LVF.

Absence of clinical signs of cardiac denervation after percutaneous myocardial laser revascularization

BACKGROUND

Percutaneous myocardial revascularization with laser (PMR) is a catheter-based technique that has generated much interest in the treatment of patients with severe coronary artery disease. Several mechanisms have been proposed to explain the reported clinical benefits of this technique. Cardiac autonomic denervation is among these.

METHODS

We studied 32 consecutive patients with chronic severe angina not suitable for other revascularization approaches. Canadian Class Society (CCS) class clinical assessment, Naughton exercise stress test, and scintigraphic myocardial perfusion were evaluated before and 1 and 6 months after PMR. Ewing's autonomic tests, heart rate variability (HRV), and plasmatic catecholamines were assessed before revascularization in non-diabetic and diabetic patients and repeated 1 month after PMR in 13 non-diabetics. A psychological test was carried out before PMR to evaluate the attitude towards this new procedure.

RESULTS

All the markers of autonomic cardiac control were unmodified after the procedure. Moreover, scintigraphic perfusion measured in the lasered areas was similar before and after the procedure. On the other hand, the clinical conditions significantly improved (CCS class from 3+/-0.8 to 1.9+/-0.9 at 1 month, P<0.01) and the exercise-related ischemic threshold was significantly better (from 311+/-28 to 453+/-51 s, P<0.05). The patients with a psychologically 'positive' expectation for this new procedure had results comparable to those with a 'negative' expectation.

CONCLUSIONS

PMR improves symptoms in patients with end-stage coronary artery disease in the absence of any detectable clinical sign of heart denervation.

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 revisited

Transmyocardial Revascularzation (TMR) is a relatively new surgical procedure used to treat angina that persists, despite other interventions (i.e. angioplasty, stenting or coronary artery bypass surgery). TMR is accomplished via an incision that exposes the heart muscle and permits application of the laser hand piece that creates new channels in the myocardium, thus improving myocardial perfusion and oxygen supply to the left ventricle. This article will explain the procedure, review patient selection criteria and discuss the nursing care for the TMR patient.

Role of MMPs and plasminogen activators in angiogenesis after transmyocardial laser revascularization in dogs

We examined the role of matrix metalloproteinases (MMPs), tissue inhibitors of MMP (TIMPs), and plasminogen activator (PA) in transmyocardial laser revascularization (TMLR)-induced angiogenesis. TMLR was accomplished with a carbon dioxide laser in seven dogs whose left anterior descending coronary artery (LAD) was ligated. Seven control dogs underwent only LAD ligation, and four dogs underwent a sham operation, consisting only of a left thoracotomy. Two weeks later, transmural myocardial samples were harvested from the distributions of the LAD and the left circumflex artery for substrate zymography, immunohistochemical staining, and in situ zymography. MMP-1, MMP-2, TIMP-1, TIMP-2, and urokinase-type PA levels in the distribution of the LAD were higher in the laser group than in the control or sham group. Counts of von Willebrand factor-positive microvessels and smooth muscle alpha-actin-positive arterioles demonstrated that the angiogenesis and ateriogenesis was promoted in the laser group and correlated directly with the number of MMP-stained microvessels. We conclude that TMLR induces the expression of MMPs, TIMPs, and urokinase-type PA and that these proteinases play an important role in angiogenesis after TMLR.

Effect of transmyocardial laser revascularization on myocardial perfusion and left ventricular remodeling after myocardial infarction in rats

PURPOSE

To monitor perfusion changes in remote myocardium caused by transmyocardial laser revascularization (TMLR) and to investigate the influence of TMLR on left ventricular morphology and function.

MATERIALS AND METHODS

The coronary arteries were ligated in 32 Wistar rats. Eight weeks later, cine magnetic resonance (MR) imaging was performed in both the treatment (n = 12) and control group (n = 8). TMLR was then performed in the remote myocardium in the treated group. Twelve weeks after myocardial infarction, cine MR imaging, including dobutamine-induced (10 micro g per kilogram of body weight per minute via the tail vein) stress, was repeated and followed with hemodynamic measurements in both groups and with perfusion MR imaging (in-plane resolution, 140 x 140 micro m) of the isolated heart at rest and during nitroglycerin-induced stress in the TMLR group (n = 10).

RESULTS

Left ventricular dilatation and hypertrophy were enhanced in the TMLR group (change in end-diastolic volume at 8-12 weeks: control group, 24.6 micro L +/- 16.7 and TMLR group, 81.7 micro L +/- 15.7; change in left ventricular mass: control group, 54.5 mg +/- 19.2 and TMLR group, 124.1 mg +/- 30.7; P <.03 for both). Ejection fractions at rest were approximately equal (control group, 40% +/- 2; TMLR group, 38% +/- 2; P value not significant), but during dobutamine-induced stress, the ejection fraction was higher in the TMLR group (54.4% +/- 4.9; control group, 47.4% +/- 4.8; P <.05). TMLR-treated areas were better perfused than was untreated myocardium (difference in perfusion: TMLR-treated vs control region, 3.89 mL/min/g +/- 0.83 at rest vs 2.29 mL/min/g +/- 1.06 during nitroglycerin-induced stress; P <.05 for both). Hemodynamic measurements revealed no differences between groups.

CONCLUSION

High-spatial-resolution perfusion MR imaging depicted a significant perfusion improvement after TMLR. Post-myocardial infarction remodeling of the left ventricle was found to be enhanced.

Transmyocardial coil implants: a novel approach to transmyocardial revascularization

BACKGROUND

Transmyocardial laser revascularization (TMLR) has potential benefit for patients with end-stage coronary artery disease and intractable angina not amenable to conventional revascularization techniques. Neovascularization has been proposed to occur around the laser channels. Our aim was to determine the feasibility of a novel nonlaser myocardial revascularization technique and its effect on angiogenesis in a nonischemic porcine model.

METHODS

In the first phase, six transmyocardial stainless steel coil implants (TMI) were deployed to the lateral wall of the left ventricle in each of 6 pigs. The animals were sacrificed at 8 and 12 weeks, with a single animal dying prematurely at 4 weeks, and the myocardium was assessed for new vessel growth. In the second phase, 8 implants were deployed in each of 12 pigs with regular fluoroscopic follow-up until sacrifice at 2 weeks to assess implant stability.

RESULTS

The deployment procedure was safe and feasible with no complications evident. A significant increase in new vessels at implant sites with 5.43 +/- 3.67, 4.97 +/- 2.44, and 3.57 +/- 2.29 seen per high power field at 12, 8, and 4 weeks, respectively, compared to 1.00 +/- 1.06 (p < 0.0001) in control myocardium. There was no evidence of implant migration in Phase 2.

CONCLUSIONS

TMIs can feasibly be deployed in the nonischemic pig model with a high success rate. The presence of angiogenesis at the implant site and the maintenance of this reaction for 3 months implies that TMI may offer an alternative to TMLR while providing a platform for delivery of angiogenic factors.

Alternatives to traditional coronary bypass surgery

Over 1 million percutaneous coronary interventions (PCI) and a half million surgical coronary artery bypass grafting procedures (CABG) are performed in the United States annually for treatment of coronary artery disease. With recent advances in anti-restenosis strategies, the number of PCIs is expected to increase dramatically. Still, these therapies treat relatively discrete coronary lesions. However, there is a relatively large number of patients for whom traditional therapies are not optimal, either because there are diffuse coronary artery lesions, because there are chronic total occlusions, or because, in the instance of bypass surgery, creating proximal or distal anastomoses is problematic. We review three strategies in various stages of development aimed at treating patients not optimally served by traditional forms of revascularization: transmyocardial laser revascularization, angiogenic therapies, and direct ventricle-to-coronary artery bypass.

Angiogenesis by endothelial cell transplantation

PURPOSE

Myocardial angiogenesis may improve regional perfusion and perhaps function after cardiac injury. We evaluated the effect of endothelial cell transplantation into a myocardial scar on angiogenesis and ventricular function, as an alternative to angiogenic gene or protein therapy.

METHODS AND RESULTS

A transmural myocardial scar was created in the left ventricular free wall of rat hearts by cryoinjury. Allogeneic aortic endothelial cells were injected into the scar 2 weeks after cryoinjury. A cluster of transplanted cells was identified at the site of injection 1 day and 1 week after transplantation, but not after 2 weeks. The size of this cluster of transplanted cells decreased as vascular density in the transplanted scar tissue increased with time. Six weeks after transplantation, vascular density was significantly greater in transplanted hearts than in control hearts. Regional blood flow, by microsphere analysis, was greater in the transplanted rats. Systolic and diastolic ventricular function was similar between groups. In a second series of experiments, syngeneic aortic endothelial cells labeled with bromodeoxyuridine were transplanted 2 weeks after cryoinjury. Vascular density in the transplanted scar was greater than in controls. Labeled transplanted endothelial cells were identified forming part of the newly developed blood vessels. No difference in vascular density was found between allogeneic and syngeneic cell transplantation. Vascular endothelial growth factor was not expressed at greater levels in the transplanted cells or the myocardial scar.

CONCLUSION

Transplanted endothelial cells stimulated angiogenesis, were incorporated into the new vessels, and increased regional perfusion in myocardial scar tissue, but did not improve global function in this cryoinjury rat model.

Transmyocardial laser revascularization

Low-powered lasers were first used in the early 1980s to produce transventricular channels as an adjunct to coronary artery bypass graft surgery (CABG). Early results were encouraging, but because of the combined procedure, could not be attributed directly to use of the laser [1]. High-powered lasers were introduced into clinical practice in 1990 [2]. These lasers are powerful enough to create a transmyocardial channel with minimal thermal damage to surrounding tissues [3]. Clinical studies, using transmyocardial laser revascularization (TMR) as the sole operative therapy for patients with severe and diffuse coronary artery disease (CAD) who have Class III or IV angina, and are on medical therapy, have been conducted since 1993. Based on the results of these studies, the FDA granted approval for the use of TMR as a sole therapy. Clinical studies are currently underway to assess the results of combined TMR and CABG [4]. Results of four controlled randomized studies have been published [5-8]. The data from two of these studies formed the basis for FDA approval of two different types of laser systems. The results of these studies have not provided any additional insights into the mechanism of action of TMR, which remains the Achilles' heel of this procedure. In this review, background information about the TMR procedure will be discussed along with an analysis of the recently published randomized studies.

Quantitative analysis of myocardial perfusion changes with transmyocardial laser revascularization

Transmyocardial laser revascularization (TLR) is a technique of creating left ventricular transmural channels in patients with refractory angina. We aimed to measure perfusion changes quantitatively using technetium-99m methoxyisobutyl isonitrile. Perfusion scans were performed on 94 TLRs and in 94 control patients at rest and during exercise at assessment, and 3-, 6-, and 12-month follow-up. A serial set of scans allowed direct comparison of each patient over all visits. Bull's-eyes were divided into 5 anatomic regions and a 20-region model. Severity values were calculated for rest, stress, and each cardiac region using a threshold of 1 for analysis. Higher scores indicated greater severity of ischemia and lower perfusion. At 3-month follow-up, the severity was significantly worse during TLR than in control patients both during stress (0.172 +/- 0.003 and 0.161 +/- 0.003, respectively, p = 0.007) and at rest (0.170 +/- 0.003 and 0.158 +/- 0.003, respectively, p = 0.002). At 6 months, severity during stress was 0.176 +/- 0.003 with TLR and 0.162 +/- 0.003 in controls (p = 0.001), with no significant difference at rest. At 12 months, there was no significant difference between TLR and control groups at stress and rest. Regional severity deteriorates during TLR compared with control patients anteriorly (p = 0.001, p = 0.0016, p = 0.005 at 3, 6, and 12 months), apically (p = 0.005, p = 0.0046, p = 0.032, respectively), and laterally (p <0.0001, p = 0.001, p = 0.002, respectively). An apparent improvement is observed in the inferoseptal region at 6- and 12-month follow-up-an area not lasered. Thus, TLR appears to produce deterioration in resting myocardial perfusion in lasered regions, and improvement in nonlasered regions, with no difference in exercise-induced myocardial ischemia compared with that in control patients.

Survival after transmyocardial laser revascularization in relation to nonlasered perfused myocardial zones

BACKGROUND

Transmyocardial laser revascularization for severe diffuse coronary artery disease reduces angina significantly. The effect on survival, however, is questionable, and risk factors are not adequately addressed. Considering that transmyocardial laser revascularization channels do not remain patent for improving direct myocardial blood supply, other variables such as perfusion through open native or grafted vessels in remote non-transmyocardial laser revascularization areas are probably more important for survival. This hypothesis is the subject of the study.

METHODS

Transmyocardial laser revascularization was performed with a CO2 laser system in 63 patients between October 1995 and December 1997. Patients received transmyocardial laser revascularization alone or in combination with coronary artery bypass grafting. The heart was divided into three perfusion zones as determined by the three major coronary arteries. Patients were divided into three groups according to the number of zones that were perfused by either a native coronary artery or a patent bypass graft: group 1 (n = 9), none; group 2 (n = 24), one; and group 3 (n = 30), two. Follow-up was performed at 3, 6, 12, 24, and 36 months and was 100% complete. Mean latest follow-up was 26.2 months, minimal follow-up of survivors was at least 12 months.

RESULTS

Overall mortality was remarkably higher in group 1 (77.8%) compared with group 2 (20.8%, p = 0.005) and group 3 (13.3%, p = 0.001). Hospital mortality was 22.2% in group 1, 0% in group 2, and 3.3% in group 3. Late mortality was also higher in group 1 (55.5% versus 20.8%, and versus 9.9%, respectively). Cardiac deaths were more frequent in group 1 (55.5% versus 12.5% in group 2, p = 0.02, and versus 9.9% in group 3, p = 0.009). The number of perfused myocardial zones showed a significant influence for survival (p = 0.002).

CONCLUSIONS

These data give some directional evidence that survival seems to be beneficially affected by the number of nonlasered perfused myocardial zones through native vessels or grafts in patients undergoing transmyocardial laser revascularization.

Transmyocardial laser revascularization induced angiogenesis correlated with the expression of matrix metalloproteinases and platelet-derived endothelial cell growth factor

OBJECTIVE

Transmyocardial laser revascularization (TMLR) has been widely evaluated as a treatment for ischemic myocardium. However, its mechanism remains unclear. One mechanism is angiogenesis. This study examines the relationship between TMLR and angiogenesis from the viewpoint of matrix metalloproteinases and platelet-derived endothelial cell growth factor.

METHODS

The left anterior descending coronary artery (LAD) was ligated permanently in 12 beagle dogs. TMLR was accomplished in six of the 12 dogs using a carbon dioxide laser. No laser treatment was done in the six control dogs. Two weeks after the initial operation, dogs were euthanized and transmural samples (each of approximately 0.5 g) were cut from the center of the infarcted LAD territory, right ventricular wall, left circumflex artery perfuse area and interventricular septum except the LAD perfuse area. They were snap-frozen in liquid nitrogen for matrix metalloproteinases and platelet-derived endothelial cell growth factor activity analysis. Hematoxylin and eosin staining, double immunohistologic staining with anti-proliferating cell nuclear antigen and von Willebrand factor antibody, and immunohistologic staining with antibody against platelet-derived endothelial cell growth factor were performed for histologic studies. The activities of matrix metalloproteinases were examined by gelatin zymography. The activity of platelet-derived endothelial cell growth factor was examined by a spectrophotometric method.

RESULTS

The channels were found to be infiltrated with granulation tissue and fibrosis. In the laser group, the active matrix metalloproteinase-2 and platelet-derived endothelial cell growth factor activity in the area of the left anterior descending coronary artery was significantly higher than in the control group (P<0.0001 and P=0.037, respectively). Within the channel remnants or close to these areas, the number of von Willebrand factor positive microvessels and proliferating cell nuclear antigen with correlating von Willebrand factor positive microvessels were significantly higher than in the control group (P=0.001 and P=0.0006, respectively). These increases in microvessels significantly correlated with the expression of matrix metalloproteinases and platelet-derived endothelial cell growth factor.

CONCLUSION

Based on these findings it was concluded that transmyocardial laser revascularization induced angiogenesis correlated with the expression of active matrix metalloproteinases-2 and platelet-derived endothelial cell growth factor.

Dissociation between improvement in angina pectoris and myocardial perfusion after transmyocardial revascularization with an excimer laser

Xenon chloride excimer laser transmyocardial revascularization significantly reduced angina in all patients and increased regional myocardial perfusion in most patients; however, there was no correlation between symptomatic improvement and flow improvement. Patients' symptomatic improvement preceded improved perfusion by several months.

Effects of transmyocardial laser revascularization by using a prototype pulsed CO2 laser on contractility and perfusion of chronically ischemic myocardium in a porcine model

The purpose of this study was to test a new prototype pulsed CO2 laser to be used for transmyocardial laser revascularization (TMR). We wanted to determine whether it can reduce thermal damage and mitigate induced ischemia with improvement in contractile reserve of the heart as evidenced by contrast echocardiography at rest and under dobutamine stress. TMR is an emerging surgical strategy for treatment of myocardial ischemia not amenable to conventional percutaneous or surgical revascularization. Eleven pigs underwent ameroid occluder placement at the origin of the circumflex coronary artery. Six weeks later, occlusion of the circumflex coronary artery was documented. TMR was then carried out on 10 pigs by using a prototype pulsed CO2 laser that delivered 8-12 joules in 1.5 ms with a spot size of 1 mm. Six weeks after TMR, the pigs were restudied. The animals developed significant ischemia after 6 weeks of ameroid occlusion, at rest (p = 0.01) and at peak stress (p = 0.004). Wall motion for the ischemic segments improved significantly 6 weeks after TMR at peak stress (p = 0.02). TMR results in an improvement in wall motion in our model of chronic ischemia and improves wall motion score index more during induced stress than at rest.

Effect of transmyocardial laser revascularization on chronic ischemic hearts in sheep

BACKGROUND

We investigated the effect of transmyocardial laser revascularization (TMR) on myocardial function and regional blood flow in an animal model of ischemic heart disease.

METHODS

Chronic ischemia was induced in 11 sheep by the application of coronary stenosis on the left anterior descending (LAD) and circumflex coronary artery (LCX). Ten weeks later, in six of them, transmyocardial channels were created in the anterior free wall and in the posterior wall of the left ventricle. Five animals served as controls. The myocardial function was assessed by echocardiography taken at baseline and every 2 weeks after coronary stenosis and after TMR. Myocardial perfusion was measured by colored microspheres, injected at baseline, immediately after coronary stenosis, before and after TMR, and at 20 weeks after coronary stenosis. The hearts were retrieved at 20 weeks for light microscopic examination.

RESULTS

The left ventricular end-diastolic and end-systolic cavity area was elevated 20 weeks after coronary stenosis in the control and TMR groups. There was no difference between groups (analysis of variance; ANOVA, non-significant). The wall thickening fraction (WTF) decreased progressively and significantly after coronary stenosis in both groups. The WTF was further acutely reduced by TMR, and recovered gradually to the pre-TMR level. No significant difference in WTF was observed between the TMR and control groups. The resting myocardial blood flow was significantly increased by TMR at 20 weeks (P=0.03). Light microscopic examination revealed channel patency in 49% of the laser scars at 10 weeks post-TMR. A dense capillary network was observed at the edges of the surrounding scar.

CONCLUSIONS

In an experimental model of ischemic heart disease, TMR developed angiogenesis in the lased channels, but, however, failed to improve myocardial function.

Symptomatic improvement after transmyocardial laser revascularization: how long does it last?

BACKGROUND

The aim of this study was to determine whether short-term clinical improvement after isolated transmyocardial holmium laser revascularization (TMLR) in patients with coronary artery disease not amenable to traditional treatment is maintained through a longer follow-up.

METHODS

Between November 1995 and June 1999 34 patients underwent TMLR (mean age, 67+/-7 years); previous revascularization procedures had been performed in 76%. Preoperatively, mean angina class was 3.6+/-0.5 in 12 patients with unstable angina; mean left ventricular ejection fraction was 47%+/-9%.

RESULTS

There was 1 early death due to low cardiac output. Mean duration of TMLR and of the entire operation was 25+/-12 minutes and 125+/-43 minutes, respectively. There were no major postoperative complications; mean hospital stay was 8+/-4 days. There were 8 late deaths caused by stroke (2 patients), cardiac failure (1 patient), and myocardial infarction (5 patients). Follow-up of current survivors ranges from 4 to 48 months (mean, 32+/-12 months). At 1-year follow-up mean angina class was 1.8+/-0.8; but at a later follow-up (mean, 35+/-10 months) it significantly increased to 2.2+/-0.7 (p = 0.005). Three-year actuarial survival was 76%+/-8% and freedom from cardiac events 44%+/-10%.

CONCLUSIONS

Our results show that after initial clinical improvement many patients experience return of angina or cardiac events; this questions the long-term symptomatic benefit of TMLR.