***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: OBJECTIVES We sought to evaluate the safety and efficacy of percutaneous transmyocardial revascularization ( PTMR ) in patients with refractory angina caused by one or more chronic total occlusions ( CTOs ) of a native coronary artery . BACKGROUND Previous unblinded , r and omized trials of PTMR in patients with end-stage coronary artery disease and refractory angina have demonstrated significant relief of angina and increased exercise duration . Whether such benefits would be realized in blinded patients with less extensive coronary artery disease is unknown . METHODS A total of 141 consecutive patients with class III or IV angina caused by one or more chronically occluded native coronary arteries in which a percutaneous coronary intervention ( PCI ) had failed were prospect ively r and omized , at 17 medical centers , in the same procedure , to PTMR plus maximal medical therapy ( MMT ) ( n = 71 ) or MMT only ( n = 70 ) . Blinding was achieved through heavy sedation , dark goggles and the concurrent performance of PCI in all patients . RESULTS Baseline characteristics were similar between the two groups . A median number of 20 laser channels were created in patients r and omized to PTMR . At six months , the anginal class improved by two or more classes in 49 % of patients assigned to PTMR and in 37 % of those assigned to MMT ( p = 0.33 ) . The median increase in exercise duration from baseline to six months was 64 s with PTMR versus 52 s with MMT ( p = 0.73 ) . There were no differences in the six-month rates of death ( 8.6 % vs. 8.8 % ) , myocardial infa rct ion ( 4.3 % vs. 2.9 % ) or any revascularization ( 4.3 % vs. 5.9 % ) in the PTMR and MMT groups , respectively ( p = NS for all ) . CONCLUSIONS In patients with class III or IV angina caused by nonrecanalizable CTOs , the performance of PTMR does not result in a greater reduction in angina , improvement in exercise duration or survival free of adverse cardiac events , as compared with MMT only BACKGROUND Transmyocardial and percutaneous laser revascularization ( TMR , PTMR ) may reduce angina and increase exercise tolerance in otherwise untreatable angina patients , although the mechanism is unknown and the placebo effect may be significant . One other proposed mechanism is cardiac denervation leading to silent ischemia . METHODS Electrocardiograms obtained during symptom-limited exercise ( ETT , modified Bruce protocol ) at baseline and 12 months were analyzed ( blinded core laboratory ) from 182 patients r and omized to TMR ( n = 92 ) or medical therapy alone ( MED(TMR ) , n = 90 ) and 219 patients r and omized to PTMR ( n = 109 ) or medical therapy alone ( MED(PTMR ) , n = 110 ) . RESULTS Exercise duration increased 1 year after TMR or PTMR relative to medically treated patients ( 6.8 + /- 3.4 min vs 8.6 + /- 3.5 min for TMR ; 7.3 + /- 3.1 min vs 9.1 + /- 3.6 min for PTMR , P < .05 ) . At baseline , 20 % of TMR and MED(TMR ) subjects had ST depression > 1.0 mm , > 80 % had angina during exercise , but only 3 % had ST changes without chest pain ( silent ischemia ) . This did not change after TMR . In the PTMR group , more subjects exercised to > 1.0 mm ST depression ( from 17 % to 34 % , P < .05 ) , with no change in MED(PTMR ) , but the proportion with silent ischemia did not change in either group . CONCLUSION Exercise tolerance improved after TMR and after PTMR . Relative to PTMR , TMR more effectively suppressed pain during exercise and ischemic ST depression . However , neither TMR nor PTMR induced significant silent ischemia . These results suggest that denervation may not be a significant factor contributing to angina relief after these procedures . The contribution of the placebo effect was not determined by these results BACKGROUND The construction of subendocardial channels to perfuse ischemic areas of the myocardium has been investigated since the 1950s . We assessed the safety and efficacy of transmyocardial revascularization with a carbon dioxide laser in patients with refractory angina and left ventricular free-wall ischemia that was not amenable to direct coronary revascularization . METHODS In a prospect i ve , controlled , multicenter trial , we r and omly assigned 91 patients to undergo transmyocardial revascularization and 101 patients to receive continued medical treatment .  The severity of angina ( according to the Canadian Cardiovascular Society [ CCS ] classification ) , quality of life , and cardiac perfusion ( as assessed by thallium-201 scanning ) were evaluated at base line and 3 , 6 , and 12 months after r and omization . RESULTS At 12 months , angina had improved by at least two CCS classes in 72 percent of the patients assigned to transmyocardial revascularization , as compared with 13 percent of the patients assigned to medical treatment who continued medical treatment ( P<0.001 ) . Patients in the transmyocardial-revascularization group also had a significantly improved quality of life as compared with the medical-treatment group . Myocardial perfusion improved by 20 percent in the transmyocardial-revascularization group and worsened by 27 percent in the medical-treatment group ( P=0.002 ) . In the first year of follow-up , 2 percent of patients assigned to undergo transmyocardial revascularization were hospitalized because of unstable angina , as compared with 69 percent of patients assigned to medical treatment ( P<0.001 ) . The perioperative mortality rate associated with transmyocardial revascularization was 3 percent . The rate of survival at 12 months was 85 percent in the transmyocardial-revascularization group and 79 percent in the medical-treatment group ( P=0.50 ) . CONCLUSIONS In patients with angina refractory to medical treatment and coronary artery disease that precluded coronary-artery bypass surgery or percutaneous transluminal coronary angioplasty , transmyocardial revascularization improved cardiac perfusion and clinical status over a 12-month period BACKGROUND Excimer laser coronary angioplasty is reported to give excellent procedural results for treatment of complex coronary lesions , but this method has not been compared with balloon angioplasty in a r and omised trial . METHODS Patients ( n = 308 ) with stable angina and coronary lesions longer than 10 mm on visual assessment were included . 151 patients ( 158 lesions ) were assigned r and omly to laser angioplasty and 157 ( 167 lesions ) to balloon angioplasty . The primary clinical endpoints were death , myocardial infa rct ion , coronary bypass surgery , or repeat coronary angioplasty of the r and omised segment during 6 months of follow-up . The primary angiographic endpoint was the minimal lumen diameter at follow-up in relation to the baseline value ( net gain ) , as determined by quantitative coronary angiography . FINDINGS Laser angioplasty was followed by balloon angioplasty in 98 % of procedures . The angiographic success rate was 80 % in patients treated with laser angioplasty compared with 79 % in patients treated with balloon angioplasty . There were no deaths . Myocardial infa rct ion , coronary bypass surgery , and repeat angioplasty occurred in 4.6 % , 10.6 % , and 21.2 % , respectively , of the patients in the laser angioplasty group compared with 5.7 % , 10.8 % , and 18.5 % of the balloon angioplasty group . Net mean ( SD ) gain in minimal lumen diameter was 0.40 ( 0.69 ) mm in patients treated with laser angioplasty and 0.48 ( 0.66 ) mm in those treated with balloon angioplasty ( p = 0.34 ) . The restenosis rate ( > 50 % diameter stenosis ) was 51.6 % in the laser angioplasty group versus 41.3 % in the balloon angioplasty group ( p = 0.13 ) . INTERPRETATION Excimer laser angioplasty followed by balloon angioplasty provides no benefit additional to balloon angioplasty alone with respect to the initial and long-term clinical and angiographic outcome in the treatment of obstructive coronary artery disease OBJECTIVES We sought to assess the variability of results obtained with thallium scintigraphy as a method for tracking the extent of myocardial ischemia in medically refractory patients with angina who are not suitable for coronary artery bypass graft surgery or percutaneous transluminal coronary angioplasty . BACKGROUND New therapies are being evaluated for patients with " no option " angina in whom medical therapy has failed . Nuclear techniques , like thallium scintigraphy , are used in multicenter trials to evaluate whether such therapies improve myocardial perfusion . However , the variability of test results is unknown in this patient group in a multicenter study . METHODS The Angina Treatments : Lasers And Normal Therapies In Comparison ( ATLANTIC ) study was a r and omized trial of transmyocardial laser revascularization ( n = 182 ) . Patients underwent dipyridamole thallium stress tests at baseline and 3 , 6 and 12 months after enrollment . The control group ( n = 90 ) was treated with constant medical therapy during the study and is a relevant group to investigate test variability . Test variability over time was quantified by the mean absolute change in the percentage of reversible perfusion defects between baseline and follow-up . RESULTS Baseline percent myocardium with ischemia averaged 17.0 + /- 13.7 % and did not change during follow-up . However , variations in the percent myocardium with reversible perfusion defects over time amounted to an average of 6 to 8 percentage points , or 43 % to 55 % of the baseline value . Only approximately 13 % of this variability was attributable to variability in image reconstruction and analysis . CONCLUSIONS As demonstrated in the ATLANTIC study , percent myocardial ischemia in control subjects receiving constant medical therapy varied in individual patients by an average of approximately 50 % . This may limit the utility of thallium scintigraphy to detect improved myocardial perfusion over time in response to therapy OBJECTIVES This study was a r and omized , 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 r and omly 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 infa rct ion , 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 infa rct ion 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 Question naire 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 Background —Although transmyocardial laser revascularization ( TMR ) has provided symptomatic relief of angina over the short term , the long-term efficacy of the procedure is unknown . Angina symptoms as assessed independently by angina class and the Seattle Angina Question naire ( SAQ ) were prospect ively collected up to 7 years after TMR . Methods —Seventy-eight patients with severe angina not amenable to conventional revascularization were treated with a CO2 laser .  Their mean age was 61±10 years at the time of treatment . Preoperatively , 66 % had unstable angina , 73 % had had ≥1 myocardial infa rct ion , 93 % had undergone ≥1 CABG , 42 % had ≥1 PTCA , 76 % were in angina class IV , and 24 % were in angina class III . Their average pre-TMR angina class was 3.7±0.4 . Results —After an average of 5 years ( and 
    Output:
    
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