Transmyocardial laser revascularization in the treatment of myocardial ischemia

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.

The role of TGFβ1 and LRG1 in cardiac remodelling and heart failure

Heart failure is a life-threatening condition that carries a considerable emotional and socio-economic burden. As a result of the global increase in the ageing population, sedentary life-style, increased prevalence of risk factors, and improved survival from cardiovascular events, the incidence of heart failure will continue to rise. Despite the advances in current cardiovascular therapies, many patients are not suitable for or may not benefit from conventional treatments. Thus, more effective therapies are required. Transforming growth factor (TGF) β family of cytokines is involved in heart development and dys-regulated TGFβ signalling is commonly associated with fibrosis, aberrant angiogenesis and accelerated progression into heart failure. Therefore, a potential therapeutic pathway is to modulate TGFβ signalling; however, broad blockage of TGFβ signalling may cause unwanted side effects due to its pivotal role in tissue homeostasis. We found that leucine-rich α-2 glycoprotein 1 (LRG1) promotes blood vessel formation via regulating the context-dependent endothelial TGFβ signalling. This review will focus on the interaction between LRG1 and TGFβ signalling, their involvement in the pathogenesis of heart failure, and the potential for LRG1 to function as a novel therapeutic target.

Surgical therapy for heart failure

Today's healthcare delivery system is challenged with an escalating number of heart failure patients who have exhausted medical therapy and overwhelmed the limits of organ transplantation. Scientific and technological advances over the last 20 years have now brought new surgical options to this vast patient population, ranging from ventricular restoration surgery to surgical gene therapy and beyond. This article reviews the myriad of surgical options that are available to these patients, their benefits and shortcomings, as well as potential future directions.

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.

Treatment of chronical myocardial ischemia by adenovirus-mediated hepatocyte growth factor gene transfer in minipigs

Growth factor gene transfer-induced therapeutic angiogenesis has become a novel approach for the treatment of myocardial ischemia. In order to provide a basis for the clinical application of an adenovirus with hepatocyte growth factor gene (Ad-HGF) in the treatment of myocardial ischemia, we established a minipig model of chronically ischemic myocardium in which an Ameroid constrictor was placed around the left circumflex branch of the coronary artery (LCX). A total of 18 minipigs were randomly divided into 3 groups: a surgery control group, a model group and an Ad-HGF treatment group implanted with Ameroid constrictor. Ad-HGF or the control agent was injected directly into the ischemic myocardium, and an improvement in heart function and blood supply were evaluated. The results showed that myocardial perfusion remarkably improved in the Ad-HGF group compared with that in both the control and model groups. Four weeks after the treatment, the density of newly formed blood vessels was higher and the number of collateral blood vessels was greater in the Ad-HGF group than in the model group. The area of myocardial ischemia reduced evidently and the left ventricular ejection fraction improved significantly in the Ad-HGF group. These results suggest that HGF gene therapy may become a novel approach in the treatment of chronically ischemic myocardium.

Functional Near-Infrared Fluorescence Imaging for Cardiac Surgery and Targeted Gene Therapy

Cardiac revascularization is presently performed without realtime visual assessment of myocardial blood flow or perfusion. Moreover, gene therapy of the heart cannot, at present, be directed to specific territories at risk for myocardial infarction. We have developed a surgical imaging system that exploits the low autofluorescence, deep tissue penetration, low tissue scatter, and invisibility of near-infrared (NIR) fluorescent light. By completely isolating visible and NIR light paths, one is able to visualize, simultaneously, the anatomy and/or function of the heart, or any desired tissue. In rat model systems, we demonstrate that the heptamethine indocyanine-type NIR fluorophores IR-786 and the carboxylic acid form of IRDye78 can be injected intravenously in the living animal to provide real-time visual assessment of myocardial blood flow or perfusion intraoperatively. This imaging system may prove useful for the refinement of revascularization techniques, and for the administration of cardiac gene therapy.