End-Systolic Volume May Hold Key to SVR Success

Reed Miller

March 05, 2010

March 5, 2010 (Florence, Italy) — The STICH trial may have failed to show an improvement in survival with surgical ventricular reduction (SVR) because the surgery didn't make the ventricle small enough [1].

That is the conclusion of Dr Marisa Di Donato (University of Florence, Italy) and colleagues, the authors of a study that tracked the impact on survival of residual left ventricular end-systolic volume index (LVESVI) following SVR. Their results are published online February 25, 2010 in the European Journal of Heart Failure.

The seminal STICH trial compared SVR with bypass surgery vs bypass alone and found that the reduction in LV volume with SVR did not improve symptoms or exercise tolerance or reduce deaths or cardiac hospitalizations. However, as reported by heartwire , some observers suggested that SVR may have failed to improve outcomes in STICH because the volume reduction--19% on average in the study--still left the ventricle too big. "Our data strongly suggest that performing SVR before the patients have reached end-stage LV dilatation may maximize the benefit of treatment," the authors argue.

The authors agree that STICH shows that "widespread application of SVR to all patients with ischemic cardiomyopathy is not warranted" but argue their study shows "it is still possible to hypothesize that a definable group of patients exists who could benefit from SVR. . . . A post hoc subgroup analysis of STICH patients is now required to define the role of SVR in patients with different degrees of LV dilatation in ischemic cardiomyopathy and to help define appropriate patient-selection criteria for this procedure."

Di Donato et al's study enrolled 216 consecutive SVR patients with a preoperative LVESI of >60 mL/m2 and measured it again a week to 10 days after the surgery. In 197 of the patients, the SVR was concomitant with a coronary bypass graft procedure, and 63 of the patients had a mitral valve repaired.

Instead of focusing on the relative reduction in ventricular volume, Di Donato et al grouped patients by their residual LVESVI at discharge--71 patients had a postprocedure LVESI of >60 mL/m2, and 145 patients had an LVESI of <60 mL/m2.

For the overall study population, the LVESI decreased an average of 41% between baseline and discharge, and the LVESVI reduction from baseline was statistically significant in both groups--29% in the >60-mL/m2 group and 47% in the <60-mL/m2 group. The authors note that the probability of death at five years in patients with a postoperative LVESVI of >60 mL/m2 in their trial was 30%, which is about the same rate as in STICH.

Multivariate analysis shows risk of all-cause death was significantly higher in the high-LVESI group. Postoperative LVESVI of >60 mL/m2 was an independent predictor of mortality at follow-up (odds ratio 10.7; 95% CI 2.67–42.9; p=0.001). Presence of a non-Q-wave MI and a preoperative internal diastolic diameter of 65 mm were the strongest predictors of a patient ending up with a postoperative LVESVI of >60 mL/m2.

In the study, preoperative end-systolic volume of 94 mL/m2 was the maximum a patient could have and still have a chance of getting under the 60-mL/m2 threshold after surgery, indicating that there is a point of no return for ventricular expansion beyond which SVR cannot help the patient.

On March 16 at the morning late-breaking clinical-trials session at the American College of Cardiology 2010 Scientific Sessions in Atlanta, Dr Robert Michler (Duke Clinical Research Institute, Durham, NC) will present more change-in-LVESVI data from STICH.