In this issue of the Journal, Hays, Lujan, and Chilton describe techniques to accurately measure aortic valve gradient during cardiac catheterization.¹ While noninvasive cardiologists may consider this whole discussion a waste of time — “old cardiology” — there are times when an accurate gradient is important.
       The gold standard of accuracy is measuring the pressure in the ascending aorta and simultaneously in the left ventricle using catheters with excellent frequency response.² The most precise way of doing this is to place two catheters simultaneously in the circulation, one in the ascending aorta and one in the left ventricle. While this had been possible using a double lumen catheter manufactured by Cordis Corporation (Miami, Florida), the catheter was large — 8 Fr — and is no longer manufactured. So to solve this problem, the authors looked at available techniques and evaluated one using a long 6 Fr sheath and enclosing a 4 Fr pigtail which would then be placed in the left ventricle. This has the advantage of requiring only one peripheral arterial puncture and only onr 6 Fr sheath. The other techniques and their advantages and disadvantages to obtain this measurement from one arterial puncture were detailed as well. Other techniques documented by the authors, the Millar catheter or pressure wire, have disadvantages of availability, and in the case of the pressure wire, the need for complete anticoagulation.
       The authors carefully evaluated this technique using a long sheath to obtain pressures in the aorta just below the subclavian vein and using that to compare with pressures in the ascending aorta. They showed an excellent correlation with the pressures in the ascending aorta and from this sheath. They did mention the need for full anticoagulation, and this has been my experience with a similar technique using a larger available sheath, and also with the pressure wire going through a 4 Fr catheter. I was impressed that clotting would occur unless anticoagulation was in place (and also, the clots were huge). There was one embolic stroke in this series which may have been from the vessel itself, the aortic valve or from a clot in the catheter.
       However, since this paper was written, a new catheter has been introduced, 6 French overall, with concentric lumens, the larger central lumen leading to either a pigtail or a Sones-like tip, with a smaller lumen surrounding the central lumen and opening into the ascending aorta. The authors referred to this catheter (Vascular Solutions, Inc., Minneapolis, Minnesota) but were not able to test it. This seems less likely to generate clot, but that remains to be seen. The same potential for areas not to be adequately flushed would seem to be in play in this catheter, as well as the long sheath technique. My own experience to date has been quite good.
       In any case, the authors are to be congratulated for their careful evaluation of this technique which combines the simplicity of a single arterial puncture with a reasonably-sized catheter and the accuracy of direct aortic measurement. My own experience with a technique like this, however, with the potential for thrombosis, emphasizes the need for anticoagulation once the central catheter is in place.
       Whether the “moving target”, so much a factor in innovative interventional and invasive cardiology, has moved on to another device remains to be seen.

1. Hays J, Lujan M, Chilton R. Aortic stenosis catheterization revisited: A long sheath single-puncture technique. J Invasive Cardiol 2005;18:262–267.
2. Fusman B, Faxon D, Feldman T. Hemodynamic rounds: Transvalvular pressure gradient measurement. Catheter Cardiovasc Interv 2001;53:553–561.