***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: PURPOSE To describe differences in health status ( symptoms , physical function , and quality of life ) between continued medical management and transmyocardial revascularization with a carbon dioxide laser in patients with severe , symptomatic , inoperable coronary artery disease . SUBJECTS AND METHODS This prospect i ve , multicenter trial r and omized 98 patients to transmyocardial revascularization and 99 to continued medical therapy .  Health status was assessed with the Seattle Angina Question naire and the Short Form-36 at baseline and at 3 , 6 , and 12 months . A new analytic technique , the benefit statistic , was developed to facilitate interpretability of disease-specific health status assessment s over time . RESULTS Of the 99 patients assigned to medical therapy , 59 ( 60 % ) subsequently underwent transmyocardial revascularization . By an intention-to-treat analysis , patients initially r and omized to transmyocardial revascularization had 44 % of their angina eliminated versus 21 % for the medical treatment group ( difference = 23 % ; 95 % confidence interval [ CI ] , 11 % to 34 % ) . Differences in the benefits of transmyocardial revascularization on physical limitations ( 33 % vs 11 % in the medical arm [ difference = 23 % ; 95 % CI , 15 % to 31 % ] ) and quality of life ( 47 % vs 20 % in the medical arm [ difference = 26 % ; 95 % CI , 18 % to 35 % ] ) were similarly large . These benefits were apparent at 3 months and sustained throughout the 1 year of follow-up . An efficacy analysis that excluded patients who crossed over from the medical treatment to transmyocardial revascularization arm suggested greater treatment benefits . CONCLUSIONS Transmyocardial revascularization may offer a valuable palliative alternative to patients with severe limitations in health status for whom no st and ard revascularization options exist 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 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 Percutaneous transmyocardial laser revascularisation ( PTMR ) is a proposed catheter-based therapy for refractory angina pectoris when bypass surgery or angioplasty is not possible . We undertook a r and omised trial to assess the safety and efficacy of this technique . METHODS 221 patients with reversible ischaemia of Canadian Cardiovascular Society angina class III ( 61 % ) or IV ( 39 % ) and incomplete response to other therapies were recruited from 13 centres . Patients were r and omly assigned PTMR with a holmium : YAG laser plus continued medical treatment ( n=110 ) or continued medical treatment only ( n=111 ) . The primary endpoint was the exercise tolerance at 12 months . Analyses were by intention to treat . FINDINGS 11 patients died and 19 withdrew ; 92 PTMR-group and 99 medical-treatment-group patients completed the study .  Exercise tolerance at 12 months had increased by a median of 89.0 s ( IQR -15 to 183 ) with PTMR compared with 12.5 s ( -67 to 125 ) with medical treatment only ( p=0.008 ) . On masked assessment , angina class was II or lower in 34.1 % of PTMR patients compared with 13.0 % of those medically treated . All indices of the Seattle angina question naire improved more with PTMR than with medical care only . By 12 months there had been eight deaths in the PTMR group and three in the medical treatment group , with similar survival in the two groups . INTERPRETATION PTMR was associated with increased exercise tolerance time , low morbidity , lower angina scores assessed by masked review ers , and improved quality of life . Although there is controversy about the mechanism of action , and the contribution of the placebo effect can not be quantified , this unmasked study suggests that this palliative procedure provides some clinical benefits in the defined population of patients 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 prospect ively r and omized to have TMR by holmium : yttrium aluminum garnet laser or TS .  Subjects were clinical ly 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 
    Output:
    
Synthesis of the existing trials through appropriate statistical methods using meta analysis may improve the power to detect clinical ly important differences between TMR and conventional methods of revascularization .
Therefore , a comprehensive current meta- analysis is needed to determine the benefits of TMR to patients ( improved clinical outcomes ) , practitioners ( improved quality of care ) , and providers ( improved cost-effectiveness )