A quantitative study of calcium deposition in the aortic wall following medtronic freestyle compared with homograft aortic root replacement. A prospective randomized trial

Background and aim of the study: Unstented aortic valve substitutes offer m any of the theoretical advantages of homografts such as superior hemodynami c performance and enhanced durability, particularly when inserted as a root . Many of these depend on the maintained flexibility of the valve component s. Calcification of the aortic wall may adversely affect these phenomena. E lectron beam computed tomography has been used to evaluate aortic wall calc ification in patients undergoing aortic root replacement in a prospective r andomized trial designed to compare the Medtronic Freestyle valve with the homograft valve replacement. Methods: Patients were followed with electron beam computed tomography scan s of the aortic root at six-monthly intervals after surgery. A calcificatio n score (Hounsfield units) and a calcified volume score (mm(3)) were obtain ed from each scan using a new modified technique. Results were related to h emodynamic data from echocardiography. The prevalence of calcification was also related to the homograft donor age, Results: Seventy-six patients (age range: 40-79 years) were randomized to r oot replacement with either homograft (n = 31) or Freestyle (n = 45) valves . Fifty-three scans of the aortic root were performed postoperatively in 37 patients. No statistical difference between the two groups was found at si x and 12 months after surgery. However, after 18 months the calcified volum e score was 5903.8 +/- 2356.8 mm(3) in the homograft versus 2725.6 +/- 1500 .5 mm(3) in the Freestyle group (p = 0.017). There was a correlation betwee n calcification score, calcified volume score and left ventricular mass (r = 0.323, p = 0.093 and r = 0.350, p = 0.068, respectively) on the one hand, and calcification score, calcified volume score and valve size on the othe r hand (r = 0.178, p = 0.466 and r = 0.068, p = 0.780, respectively). Conclusions: Electron beam computed tomography provides a powerful tool for the detection of calcium in the aortic wall of valve grafts. There is a lo w rate of calcification during the first 18 months in the Medtronic Freesty le valve, and this appears to be lower than that observed in homografts. Lo nger-term follow up of the aortic root in these patients is required. This is an ongoing study.