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Percutaneous treatment of aortic valve stenosis

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Percutaneous aortic balloon valvuloplasty serves best as palliative therapy in severely symptomatic patients, and as a bridge to surgery in hemodynamically unstable adult patients. 21,22 Percutaneous aortic balloon valvuloplasty is not an option in patients who are good candidates for surgical valve replacement. 1

PERCUTANEOUS AORTIC VALVE REPLACEMENT: THREE TECHNIQUES

Percutaneous aortic valve replacement was first reported in 1992 using a closed-chest pig model. 14 Since then, three prosthetic valves have been used in human clinical trials for this procedure: the Cribier-Edwards valve (Edwards Lifesciences Corporation, Irvine, CA), the CoreValve (CoreValve Inc, Irvine, CA), and the Edwards SAPIEN valve (Edwards Lifesciences Corporation, Irvine, CA) ( Table 1 ). These have been implanted in humans using three different percutaneous techniques ( Figure 1 ).

The antegrade technique

Figure 1.
In the antegrade technique, an approach that has been studied but is no longer being used, access to the femoral vein is gained and the catheter with the prosthetic aortic valve is advanced, traversing the interatrial septum and the mitral valve, and is positioned within the diseased aortic valve. 15,23,24 The main advantage of this approach is that the femoral vein can accommodate the large catheter sheath and that subsequent management of the access site is by manual compression only. 15,23,24 The main disadvantages are the potential for mitral valve injury and severe mitral regurgitation, and the technical challenge of delivering the aortic valve prosthesis to the correct aortic position. 15,23,25–27

The retrograde technique

In the retrograde (ie, transfemoral) technique, access to the femoral artery is gained and the catheter with the prosthetic aortic valve is advanced to the stenotic aortic valve. 8,11,26,28–30 This approach is faster and technically easier than the antegrade approach, but it can be associated with injury to the aortofemoral vessels and with failure of the prosthesis to cross the aortic arch or the stenotic aortic valve. 11,23,30

The transapical technique

In the transapical technique, the valve delivery system is inserted via a small incision made between the ribs. The apex of the left ventricle is punctured with a needle, and the prosthetic valve is positioned within the stenotic aortic valve. 27,31–33 The main advantage of this approach is that it allows more direct access to the aortic valve and eliminates the need for a large peripheral vascular access site in patients with peripheral vascular disease, small tortuous vasculature, or a history of major vascular complications or vascular repairs. 31–33 Potential disadvantages are related to the left ventricular apical puncture and include adverse ventricular remodeling, left ventricular aneurysm or pseudoaneurysm, pericardial complications, pneumothorax, malignant ventricular arrhythmias, coronary artery injury, and the need for general anesthesia and chest tubes. 27,31–35

Common features of the three approaches

The three percutaneous approaches have certain final steps in common. 11,23,30,33 The position of final deployment of the prosthetic valve is determined by the patient’s native valvular structure and anatomy and is optimized by using fluoroscopic imaging of the native aortic valve calcification as an anatomical marker, along with guidance from supra-aortic angiography and transesophageal echocardiography. 11,23,30,33 Ideally, the aortic valve prosthesis is placed at mid-position in the patient’s aortic valve, taking care to not to impinge on the coronary ostia or to impede the motion of the anterior mitral leaflet. 11,23,30,33 In all three procedures, the prosthesis is then deployed by maximally inflating, rapidly deflating, and immediately withdrawing the delivery balloon. This final step is carried out during temporary high-rate right ventricular apical pacing, which produces ventricular tachycardia at 180 to 220 beats/min for up to 10 seconds. 11,23,30,33 This leads to an immediate decrease in stroke volume, resulting in minimal forward flow through the aortic valve, which in turn facilitates precise positioning of the prosthetic valve.

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