Patients who had prior aortic root replacement with the Bentall’s technique were recruited over a period of 15 months. The referrals for imaging were all based on clinical review and recommendation by patients’ treating physicians as part of their long-term follow-up. Detailed background history was obtained from each patient and further corroborated with the patient’s medical record. Clinical information collected included indications for surgery, original pathology, comorbidites, original operation report, and associated histopathology reports.
The original Bentall procedure and its subsequent modifications have been published previously [4, 5]. In brief, Bentall et al. used a wrap/inclusion technique whereby the coronary ostia were not excised from the native aorta but sutured onto side-holes of the prosthetic aorta. Current approaches commonly use the ‘button’ technique with end-to-side re-implantation of the coronary ostia with a surrounding ‘button’ or cuff of native aortic tissue directly onto the aortic graft (modified Bentall operation). In this series, all patients underwent the modified Bentall procedure.
Standard two-dimensional and Doppler TTE was performed by an experienced sonographer using commercially available transducer and equipment (M3S probe, Vivid7, GE, Horten, Norway). Echocardiograms were recorded and stored in a digital database and then analysed offline using commercially available software (GE EchoPac 7.0.1, Horten, Norway). Echocardiogram was performed with patients in the left lateral decubitus position. TTE used conventional and novel acoustic windows to interrogate the coronary ostia. Conventional acoustic windows concentrated on the parasternal short-axis views whilst several off-axis views were attempted to determine the optimum TTE acoustic window for visualizing the coronary ostia. The coronary ostial diameter was measured using electronic calliper at the coronary ostial-aortic graft junction from the optimum acoustic window.
All patients also underwent MDCT imaging using a dual-source 64-slice scanner (Siemens Medical Solutions, Forchheim, Germany). The scanner parameters have been previously published . 100 ml of contrast (Omnipaque 350; Amersham Health, Princeton, USA) followed by 81 ml of saline flush was injected continuously at 3.5 ml/s. Bolus tracking (when aortic root image density value exceeded 100 HU) was used to initiate the scan after 8 seconds of monitoring delay. Axial images were reconstructed at 0.6 mm slice thickness and 0.3 mm increment, using retrospective electrograph gating. A medium-soft convolution kernel was used (B25F). Nitroglycerine was not used for the study cohort to eliminate any potential confounder when measuring coronary artery diameters. None of our patients required beta-blockers during their scans.
The diameters of the coronary vessels on CT scan were assessed offline using commercially available software (Syngo® Circulation, Siemens Medical Solutions, Erlangen, Germany). Measurements were performed from the ‘best diastole’ data set. The coronary ostial diameter was measured using electronic calliper at the coronary ostial-aortic graft junction. 0.6 mm multi-planar reconstructions were manipulated to obtain an image perpendicular to the aortic root at the level of the coronary ostium that showed the greatest ostial dilation on visual assessment. A soft tissue window was used (600/200).
The study complies with the Declaration of Helsinki and was approved by the institution (Concord Hospital) Ethics Committee on Human Research (CH62/6/2008-059).
All continuous variables are expressed as mean ± standard deviation. Mean coronary ostial diameters obtained from TTE versus MDCT were compared using paired t tests. Analysis was performed using PRISM 4.03 (GraphPad Software, Inc.). A two-tailed probability value <0.05 was considered statistically significant.