Evaluation of aortic root and valve calcifications by multi-detector computed tomography

In percutaneous aortic valve replacement (AVR), whilst calcifications are used as landmarks in fluoroscopic placement of the stent, they may also complicate stent placement. In response to this problem, the study aim was to examine severe aortic root calcification by using multi-detector computed tomography (MDCT), to better understand the pathology complicating percutaneous valve placement.

In 33 patients with severe aortic stenosis and scheduled for surgery, the 'inner orifice' and 'outer fibrous' annulus diameter and area (with and without calcification) were measured, in addition to the distances of the calcifications and coronary ostia from the annulus, using by ECG-gated 64-slice MDCT. Aortic root calcification was evaluated as minimal (< 25% of total circumference), mild (25-50%), moderate (50-75%), and severe (75-100%).

The inner orifice annulus area was 5.9 +/- 1.9 cm2 (range: 1.4-10.1 cm2), while the outer fibrous area was 7.5 +/- 1.8 cm2 (range: 4.7-11.5 cm2). The proximal-to-distal extent of valve calcification from the annulus in the mid-center of leaflets was 0.8 +/- 0.26 cm. In 36% of patients, valvular calcification extended +/- 3 mm within the coronary-ostium level. The distance of the coronary ostia from the annulus was variable, with a mean of 1.3 +/- 0.35 cm (range: 0.6-2.4 cm) for the left coronary artery. In 42% of patients, a 'low coronary ostium' (< or = 1.1 cm), and in 6% a 'critical-low-coronary ostium' (< or = 8 mm) was identified. Annulus calcification was present in 100% of cases, but the severity varied widely (severe 50%, moderate 35%, mild 15%). In 36% of cases, the aortic annulus calcification extended caudally into the membranous part of the interventricular septum (and thus into the left ventricular outflow tract), and in 42% of cases (n = 14) into the anterior mitral valve leaflet.

The present results indicated that cardiac MDCT may qualify as a primary pre-procedural imaging modality to select patients for percutaneous AVR, based on the measurement and characterization of the aortic root and valve calcification. In comparison to echocardiography, CT will reduce--if not eliminate--difficulties in visualizing the aortic orifice area in heavily calcified valves. Furthermore, knowledge of the exact location of calcific deposits provides a distinct advantage to the fluroscopist for precise placement of the percutaneous aortic valve. Likewise, knowledge of the coronary arteries orifice in relation to the valve plane is critical to prevent inadvertent coronary artery occlusion, and would clearly be beneficial when planning future valve designs.