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FIG 18.4 Retrograde aortic balloon valvoplasty with rapid right ventricular pacing as seen in frontal projection FIG 18.5 Anterograde balloon aortic valvoplasty The balloon is introduced through the femoral vein and across the oval fossa defect, or after a transseptal puncture, to access the left heart The wire is placed in the descending aorta and provides stability to the balloon Recent reports of long-term outcome after aortic balloon valvoplasty indicate that there is an excellent early relief of the valvar gradient but an increase in aortic regurgitation.96 Independent predictors of unfavorable outcome have been a small aortic root, poor function of the left ventricle or mitral valve, and limited experience of the operator.97 Valvar morphology has recently been demonstrated to relate to valvar function following valvuloplasty, with functionally unicuspid valves and other subtypes with greater leaflet fusion demonstrating better response to balloon dilation.98 Procedure-related mortality is reported at 4.8% and is highest in critical AS.97 Although the risk of vascular injury is high, the majority of the complications are transient and respond to thrombolysis and anticoagulation In critical aortic stenosis, the morphology of the aortic root, the mitral valve and presence of left ventricular endocardial fibroelastosis have a major impact on outcome and need for reintervention Neonatal critical aortic stenosis remains challenging despite continuing development of catheter technology for small babies Despite effective relief of stenosis, patients may require functionally univentricular palliation if the morphology is not favorable for effective biventricular circulations or if the ventricular myocardium remains dysfunctional (see also Chapter 44) Implantation of the Aortic Valve Percutaneous interventions on the aortic valve in adults with calcific aortic valvar stenosis and other comorbidities rendering the valve inoperable are encouraging The first report of insertion of bovine pericardial trifoliate valve came from Cribier and colleagues.99 Procedural complications in early implantations were related to the anterograde approach and the large size of the system required for delivery The technique has been refined, with development of a retrograde approach, and implantation of the valve with rapid right ventricular pacing to reduce the risk of embolization.20 Self-expanding stentmounted valves have also been used in similar clinical settings.100 However, the current devices available are not yet suitable for routine use in children and young adults, although occasional implants have occurred.101 Mitral Valve Mitral Stenosis Congenital mitral valvar stenosis is a complex disease, with involvement of supravalvar, valvar, and subvalvar components (see Chapter 34) Balloon dilation is rarely used as first intervention, due to the high risk of restenosis or risk of injury to the valvar tension apparatus and leaflets, leading to severe regurgitation However, percutaneous valvoplasty has successfully replaced closed and open mitral commissurotomy for rheumatic mitral stenosis Selection of patients based on echocardiography is fundamental in predicting outcomes and requires a detailed assessment of the mitral valve.102 The approach is anterograde after transseptal puncture The Inoue balloon is most widely used, which consists of a coaxial balloon with a double lumen Inflation leads to sequential dilation of the distal part, facilitating entry into the left ventricle, of the proximal part fixing the balloon across the mitral valve, and of the central part, which dilates the valvar annulus A Multitrack technique with a monorail system with two balloons over a single guidewire was introduced by Bonhoeffer and colleagues,46 permitting successful dilation of the fused leaflets of the mitral valve
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