LETTER TO THE EDITOR
Percutaneous laser revascularization in patients with chronic total occlusions
Emerson C. Perin, MD, FACCa,
Samuel J. DeMaio, MD, FACC,
Barry George, MD, FACC and
William W. O’Neill, MD, FACC
a Associate Director, New Interventional Cardiovascular Technology, Texas Heart Institute, 6624 Fannin, Suite 2220, Houston, Texas 77030, USA
eperin{at}crescentb.net
As clinical investigators of the percutaneous myocardial revascularization (PMR) device, we read with interest "A Prospective, Multicenter, Randomized Trial of Percutaneous Transmyocardial Laser Revascularization in Patients With Nonrecanalizable Chronic Total Occlusions" (PMR-CTO trial) by Stone and colleagues (1). Based upon the lack of available follow-up data and objective evidence, we do not agree with their negative conclusions regarding this study or with their generalizations regarding different laser systems.
There was approximately 50% available follow-up data for both primary study end points at six months: namely total exercise duration and angina improvement. The limited six-month follow-up data favors PMR-treated patients and may have achieved significance with complete follow-up at 6 and 12 months. Importantly, the review of major adverse events through six months supports the reasonable safety of the procedure.
The discussion regarding laser technology, along with the conclusion of the need for further study of PMR, leaves the impression that the laser systems used in the various studies are similar and presumes that the difference in trial outcomes is explained by protocol design. Despite being HO:YAG systems, the lasers used in the various studies discussed are not similar regarding energy delivery and tissue interaction. The (DMR) laser system used in the DIRECT study transmitted a single energy pulse to the endocardial surface and did not advance into the endocardium to create a channel. The DMR system was designed for triggering an endogenous tissue response, not for channel formation (2). The CardioGenesis PMR laser systems fiberoptics deliver multiple energy pulses while penetrating into the myocardium to create deep, non-transmural channels. Based on the negative outcome for the DIRECT trial utilizing the DMR system, it is clear that fiberoptic penetration into the myocardium and significant channel formation, as with PMR, are essential to achieving clinical benefit.
For PMR, the placebo question has been effectively addressed by the independently conducted, randomized, double blind, true-sham BELIEF trial, which was performed to assess the potential of placebo as a principal mechanism for angina improvement with the CardioGenesis Axcis PMR system. The investigators concluded that the significant 12-month clinical benefit for PMR-treated patients, compared to sham control, was not attributable to placebo (3). During the BELIEF trial, patients, investigators, and assessors were blinded, and cardiac medications were held constant. In the PMR-CTO trial, physicians were not blinded, and patient blinding (i.e., heavy sedation, PMR simulation, eye coverage) may not have been consistently achieved. Whereas Stone and Colleagues challenge the lack of increased exercise tolerance or reduction in ischemia in BELIEF, the study was not designed or intended to show a change in those measures. Studies performed with the CardioGenesis PMR system, examining perfusion with position emission tomography (PET), have shown significant perfusion improvement (4,5).
Three randomized, multi-center trials [PACIFIC(6), PMR010(7), and the independent BELIEF] encompassing nearly 650 patients have been completed with the CardioGenesis PMR systems. All have consistently demonstrated a significant clinical benefit favoring the PMR-treated patients in all primary end points, with significantly improved functional capacity at 12 months. PMR is not DMR.
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References
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1. Stone GW, Teirstein PS, Rubenstein R, et al. A prospective, multicenter, randomized trial of percutaneous transmyocardial laser revascularization in patients with nonrecanalizable chronic total occlusions. J Am Coll Cardiol. 2002;39:1581–1587[Abstract/Free Full Text]
2. Kornowski R, Fuchs S, Leon MB. Biosense guided direct myocardial revascularization. Kornowski R, Epstein SE, Leon MB. Handbook of Myocardial Revascularization and Angiogenesis. London: Martin Dunitz Ltd; 1999. p. 64–75
3. Salem M, Rotevatn S, Stavnes S, et al. Blinded evaluation of laser intervention electively for angina pectoris. (abstr)Circulation. 2001;104(Suppl II):II444
4. Bortone AS, D’Agostino D, Schena S, et al. Instrumental validation of percutaneous transmyocardial revascularization: follow-up data at one year. Ann Thorac Surg. 2000;70:115–118[Abstract/Free Full Text]
5. Weimer M, Butz T, Wielepp JP, et al. Improvement in myocardial perfusion detected by positron emission tomography in patients with end-stage coronary artery disease treated with percutaneous myocardial laser revascularization. (abstr)Circulation. 2001;104(Suppl II):II445
6. Oesterle SN, Sanborn TA, Ali N, et al. Percutaneous transmyocardial laser revascularization for severe angina: the PACIFIC randomized trial. Lancet. 2000;356:1705–1710[CrossRef][Medline]
7. Whitlow PL, Knopf WD, O’Neill WW, et al. 12-Month follow-up of percutaneous myocardial revascularization in patients with refractory angina. (abstr)J Am Coll Cardiol. 1999;33(Suppl A):29A
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