Ann Thorac Surg 2007;83:2058-2059
© 2007 The Society of Thoracic Surgeons
Original Articles: Cardiovascular
Invited commentary
John R. Pepper, FRCS
Department of Surgery, Royal Brompton Hospital, Sydney St, London, SW3 6NP United Kingdom
(Email: j.pepper{at}rbht.nhs.uk).
Valve replacement for aortic stenosis must rank as one of the most satisfying procedures of the adult surgical repertoire. Patients notice relief of symptoms and improved exercise tolerance within weeks, and operative mortality is in the low single figures. However we can not be complacent while there are subgroups of patients who experience a much higher mortality and survivors who have little improvement in quality of life. Such groups are elderly females whose left ventricular (LV) hypertrophy is often severe, or other elderly patients with poor LV function. There is little we can do to alter reduced arterial compliance in a rigid vascular system, but we should strive to insert a valve substitute that offers the least resistance to flow and therefore allows the left ventricle to unload as fully as possible.
We have learned from studies of stentless valves and from mechanical assistance of end-stage heart failure how exquisitely sensitive the left ventricle is to loading. Studies of prosthesis patient mismatch (PPM) in which the indexed effective orifice area (EOA) have been used rather than the geometric orifice area (GOA), showing that survival is enhanced if PPM is avoided, especially when LV function is impaired.
In an observational, nonrandomized study, Borger and colleagues [1] showed that peak and mean transvalvular gradients are significantly lower with the supra-annular positioned Magna pericardial valve compared with the intra-annular placed Hancock II prosthesis (peak 22.2 vs 32.3 mm Hg; p = 0.001; and mean 10.4 vs 18.5 mm Hg; p = 0.001). This mean value for the Magna is close to that reported in stentless valves in which the mean gradients are generally less than 9 mm Hg. The effective orifice area was greater (1.40 vs 1.29cm2; p = 0.07) and PPM (30 vs 52%; p = 0.02) was significantly less frequent in the Magna group. Unfortunately the EOA was not related to body surface area, so it is difficult to compare with other series. As 83% of the patients were operated on for aortic stenosis, it is odd that only the postoperative values for LV mass index are given so we can not judge the severity of pre-existing LV hypertrophy.
Nevertheless, this study shows that the design of aortic valve substitutes is improving. Accurate and comprehensive data are important as we shall soon be able to compare surgical results with transcutaneous aortic valve replacement in which the stentless valve substitute consisting of equine or bovine pericardium is very thin, but the native valve tissue remains in situ.
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- Borger MA, Nette AF, Maganti M, Feindel CM. Carpentier-Edwards Perimount Magna valve versus Medtronic Hancock II: a matched hemodynamic comparison Ann Thorac Surg 2007;83:2054-2059.[Abstract/Free Full Text]
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