Background—Routine preoperative catheterization is standard practice in patients with single-ventricle physiology before bidirectional Glenn anastomosis. Because catheterization is invasive and exposes patients to ionizing radiation, cardiac magnetic resonance (CMR) may be a safe and effective alternative.

Methods and Results—We conducted a prospective, randomized, single-center clinical trial comparing catheterization with CMR in patients considered for bidirectional Glenn operation from February 2003 to June 2006. End points were frequency of adverse events of the preoperative evaluation and a composite score of clinically successful surgery. Of 92 eligible patients, 82 were enrolled on the basis of screening echocardiogram, fulfillment of inclusion criteria, and informed consent. Patients were randomized to catheterization (n=41) or CMR (n=41). There were no baseline differences between groups. Four treatment crossovers occurred, 3 to catheterization and 1 to CMR. Catheter interventions were performed in 17 patients (41%). Catheterization resulted in more minor adverse events (78% versus 5%; P<0.001), longer preoperative hospital stays (median, 2 versus 1 day; P<0.001), and higher hospital charges ($34 477 versus $14 921; P<0.001). There was 1 major adverse event in the CMR group (P=1.0). The operative course and frequency of postoperative complications were similar between the 2 groups. The proportion of patients who had a successful bidirectional Glenn operation was similar (71% versus 83%; P=0.3). At the 3-month follow-up, there were no differences in clinical status, oxygen saturation, or frequency of reinterventions.

Conclusions—CMR is a safe, effective, and less costly alternative to routine catheterization in the evaluation of selected patients before bidirectional Glenn operation. Further studies are necessary to determine whether there are long-term benefits from transcatheter interventions in these patients.