The aortic valve : structure, complications and implications for transcatheter aortic valve replacement

The aortic valve operates in a complex haemodynamic environment, opening and closing over 100,000 times a day. When complications arise, such as aortic stenosis, prognosis can be very poor, leading to death within the first few years. Surgical valve replacement is currently the standard treatment for aortic stenosis. A thorough understanding of the anatomy and function of the native valve is imperative when developing a prosthetic replacement that can withstand the complex demands of the heart. This review focuses on the anatomy, structure and disease of the aortic valve and the implications for a transcatheter aortic valve replacement (TAVR). Current complications with TAVR, such as major vascular bleeding, conduction disturbances and patient-prosthesis mismatch (PPM), can be overcome by reducing the delivery profile and through the use of more accurate imaging technologies to work towards a fully functional and durable prosthesis

Which spinal levels are identified by palpation of the iliac crests and the posterior superior iliac spines?

The line joining the superior aspect of the iliac crests posteriorly (the intercristal line) is commonly stated to cross the midline at the L4 or L4–5 spinal level on imaging. This study aimed to assess the spinal level identified through palpation of surface anatomy (iliac crests and posterior superior iliac spines) in adults and the level of agreement compared with the intercristal line identified through imaging. The study participants included consecutive adult patients undergoing prone fluoroscopically guided spinal injections for chronic low back pain at the Royal Orthopaedic Hospital, Birmingham, between April and July 2004. Prior to fluoroscopic imaging, each patient's surface anatomy was palpated by two examiners and lines created to form the palpated intercristal line and the posterior superior iliac spine line. Following imaging, the mid-line spinal levels identified by these palpated lines were recorded and the level of agreement (kappa coefficient) with the intercristal line formed by imaging of the iliac crests was assessed. The results showed that although the L4 or L4–5 spinal levels were identified on imaging of the intercristal line in 86.7% of 75 patients (49 female), the intercristal line formed through palpation tended to identify higher levels; the L3 or L3–4 spinal levels in 77.3% of cases and more commonly in females than in males (85.7 vs. 61.5%) and in patients with higher body mass indices. The level of agreement between the two lines was poor (κ = 0.05). The posterior superior iliac spine line identified the S2 spinous process in 51% and the S1 in 44% of 60 (45 female) patients. The results suggest that formation of the intercristal line by palpation of the iliac crests identifies different spinal levels to those identified by imaging and that both methods should be regarded as different instruments. In the clinical situation, it may be more appropriate to consider that palpation of the intercristal line is a guide for identifying the L3 or L3–4 spinal levels rather than the L4 or L4–5 levels, particularly in females and patients with higher body mass indices