Background: Percutaneous myocardial laser (PML) is a catheter-based treatment providing access to the endocardial surface of the myocardium to create channels using a holmium: yttrium-aluminum-garnet (HO:Y AG) laser. A prospective, randomized, double blind trial to compare PML versus Sham procedure was performed to evaluate the contribution of placebo effect related to clinical benefits achieved post-PML.treatment.
Methods: Eighty-two patients from two institutions with refractory angina not amenable to direct coronary revascularization (PTCA or CABG), were randomly assigned to either PML treatment or the sham procedure. With the exception of one concealed, unblinded laser technician, the nature of the treatment was blinded to all others involved for the duration of the trial. A blinded assessor determined the primary endpoint of Canadian Cardiovascular society Angina Scale (CCSAS) class at baseline, 3, 6, and 12 months foIlowing the treatment. Secondary end points consisted of mortality, morbidity, quality of life assessment, cardiac medication use and exercise tolerance testing. Among the 82 patients, 86.6% were in CCS class III, and 13.4% in class IV. The mean left ventricular ejection fraction was 64.7%, 82.9% of patients had triple vessel disease, 67.1 % had previous myocardial infarction, and 89% had previous coronary interventions. The treatment groups were comparable at baseline. A mean of 19.7 laser/sham positions were obtained, and a mean of 78.7 pulses/sham were fired.
Results: At 3,6 and 12 months angina improved by at least one class in 55%, 64% and 64% of patients who underwent PML compared to 47% (p = 0.4), 38% (p = 0.01) and 40% (p = 0.03) in the sham group. Angina improvement by at least two classes was seen in 25%, 41 % and 36% versus 15% (p = 0.24), 13% (p= 0.004) and 15% (p =0.03), respectively. Related quality of life measures were significantly better in the PML group at 6 and 12 months (p < 0.05); other secondary endpoints were not statistically different (p > 0.05). There was no crossover or differences in medical therapy between treatment groups during follow-up