March 16, 2010 (Atlanta, Georgia) — Yet another analysis of the Surgical Treatment for Ischemic Heart Failure (STICH) trial has failed to identify a subset of coronary-bypass patients that benefits from surgical ventricular reduction (SVR).
At last year's American College of Cardiology (ACC) 2009 Scientific Sessions in Orlando, FL, Dr Robert H Jones (Duke University, Durham, NC) presented results from the 1000-patient STICH trial showing that CABG with SVR reduced end-systolic volume index (ESVI)--the volume of the left ventricle indexed to the patient's size--more than CABG alone, but that result made no difference in angina, heart-failure symptoms, or on six-minute-walk test. Death and hospitalization rates were the same with both procedures.
At this year's ACC conference, STICH investigator Dr Robert Michler (Duke Clinical Research Institute) presented results of a new analysis intended to determine whether any magnitude of postoperative change in left-ventricle ESVI identified a subgroup of CABG-plus-SVR patients who derived a survival benefit compared with CABG alone.
The analysis was limited to the 595 patients who had accurate preoperative and four-month postoperative measures of their end-systolic volume. Limiting the analysis to this subgroup biased the study in favor of SVR, Michler said, because these patients had a lower mortality than the 1000 patients in STICH overall. However, despite that bias, the analysis found no subset of patients based on baseline ESVI or reduction in ventricular volume that had statistically significant better outcomes than comparable patients who had CABG only.
Many surgeons assumed that patients whose baseline end-systolic volume index was especially high (>90 mL/m2) would benefit most from SVR, Michler said. However, this analysis found the opposite. Among the 235 patients whose baseline ESVI was >90 mL/m2, the trial showed a statistically nonsignificant trend toward more all-cause mortality in patients undergoing both CABG and SVR but showed a nonsignificant trend in favor of CABG only in the 360 patients with baseline ESVI <90 mL/m2 . This pattern held even when the large- and small-ventricle groups were further subdivided based on whether the surgery reduced their ESVI by more or less than 30 mL/m2.
Speaking at a press conference after the results were announced, Jones said, "The take-home [message] is that--except in an emergency situation where we can't get somebody off of coronary bypass--there does not appear to be any patient at the time of bypass surgery whom we can identify who needs ventricular-reduction surgery.
There does not appear to be any patient at the time of bypass surgery whom we can identify who needs ventricular-reduction surgery.
He suggested that the most surprising finding was how much ventricular reduction was caused by CABG alone. Over 20% of CABG-only patients had 30% or more reduction in their ESVI four months' postsurgery. "This is an operation that began in the 1950s, and there have literally been millions of patients to undergo this surgery, but there's never been a randomized trial and there's never been a coherent trial," Jones said. "I think what surprised most surgeons is that bypass alone reduced ventricular size almost as much as ventricular surgery.
"It's surprising, but it's a definitive result and raises the question of whether we should ever do ventricular-[reduction] surgery."
Michler pointed out that the group of patients with baseline ESV between 60 and 90 mL/m2 showed the most promising trend toward benefit from SVR, and therefore he suggested a randomized trial just looking at that patient subset may be warranted.
Asked about that suggestion during the press conference, Jones commended Michler's optimism but said that he believes there would be little "enthusiasm or energy among the surgical community for that trial."
Michler said that the STICH results should be viewed as more definitive than previous trials of SVR because the study compared preoperative and postoperative ventricular volume at four months. Most previous studies have only measured postop ventricular volume immediately after the surgery or one week later, which fails to account for the ventricle's tendency to reshape itself over several weeks.
Jones explained that "the heart can eject only what it can fill, so the idea of making the heart smaller is that it has a bit less compliance [and] sacrificing that to hopefully have the ventricle work more efficiently in a smaller state, but over time what happens is that the ventricle tries to reseek its normal size."
Jones rejected the idea that the lack of benefit with SVR in STICH can be blamed on suboptimal surgical technique. "What the surgeon does can help the emptying of the heart but not the filling of the heart. And the heart has to be able to fill during times of stress, exercise, and daily activity," he said. "So just because the surgeon can force it to be smaller by mechanically changing it, it then gradually reenlarges to the size it wants to be. It doesn't suggest that there was anything wrong with the surgery."
Heartwire from Medscape © 2010 Medscape, LLC
Cite this: Finally Final? New STICH Analysis Finds No Subset That Benefits From Ventricular Reconstruction - Medscape - Mar 16, 2010.
Comments