Andersons pediatric cardiology 1125

FIG 42.33 A neonate with critical pulmonary valve stenosis (A) Baseline right ventricular angiogram documenting severe stenosis of the pulmonary valve with only a narrow jet entering the main pulmonary artery (B) Initial balloon valvuloplasty with a tight waist/hourglass appearance—note the wire position through the patent ductus arteriosus into the descending aorta (C) Balloon being fully inflated without a residual waist (D) Right ventricular angiogram documenting subvalvar narrowing after balloon pulmonary valvuloplasty The choice of guidewire is dependent on the operator and on the age of the patient In older patients who are stable during the procedure, it would be reasonable to use a hydrophilic wire to gain a distal position in the pulmonary artery, exchanging it for a stiff exchange wire, which then can be used for advancing the balloon catheter In neonates, a coronary angioplasty wire can be passed through the valve and used to deliver the angioplasty catheter The choice of the type of the initial balloon used often depends on the availability at each institution In general, in small patients, fairly compliant balloons such as the Tyshak II or Tyshak mini are often used, whereas in older patients less compliant balloons, such as the ZMed II, may offer advantages due to the higher-rated burst pressure Some centers have even used unconventional balloons such as the Inoue balloon, even though these are less desirable choices for the procedure.90 The choice of dimension of the balloon has been the source of much discussion It is clear that the balloon must be oversized in relation to the dimension of the pulmonary valve, but there is evidence that sizes in excess of 120% to 125% of the pulmonary valve are no more efficacious at reducing the severity of pulmonary stenosis yet create more problems in terms of subsequent pulmonary incompetence or other complications.91,92 An exception could be argued in cases where the valve is markedly dysplastic and stenosed There are few detailed data and little evidence for choosing the length of the balloon Shorter balloons may be more difficult to stabilize centrally over the pulmonary valve, whereas longer balloons carry more risk of damage to the tricuspid valve,88 atrioventricular node,93 and distal pulmonary arteries Simple, intuitive choices are a 20-mm balloon for neonates and infants, a 30-mm balloon for children, and 40- to 50-mm balloons for adolescents and adults.69 In most cases, therefore, a coaxial angioplasty balloon of the appropriate size is selected and tracked over the guidewire to the pulmonary valve If the balloon fails to track through the right ventricle, then there is a good chance that the catheter has passed behind some tension apparatus of the tricuspid valve In that case it is better to withdraw the catheter and guidewire and recross the tricuspid valve so as to obtain a better position To force the angioplasty balloon onward is disadvantageous because the balloon would be drawn in a denatured form back through the tricuspid valve with the potential for serious damage.88 When it is difficult to cross the pulmonary valve with the chosen dimension of balloon, it is often better to exchange the balloon angioplasty catheter for a smaller one, even as small as a 3-mm coronary angioplasty balloon, in order to predilate the valve before returning with the original.94 In neonates, trackability of the balloon across the valve can be improved if the wire has been positioned across the arterial duct and is compressed at the inguinal site externally Balloon preparation follows standard technique, as outlined in Chapter 19 In unstable patients, the balloon should be prepped and ready to use prior to crossing the pulmonary valve Ideally an inflation device is used that can be operated with a single hand while the other hand controls the wire position This simultaneous coordination between balloon position and inflation aids in achieving a central position of the balloon across the valve during inflation While watching the hourglass impression of the pulmonary valve on the balloon during inflation (see Fig 42.29), the balloon might prolapse forward or backward and manipulation of the balloon and the guidewire may be required Cardiac output control through rapid ventricular pacing is usually not required for balloon pulmonary valvuloplasty The balloon is inflated until its waist is seen on fluoroscopy to have been abolished Application of higher pressure does not serve any useful purpose beyond the point at which parallel walls of the balloon have been reached, and it carries a greater risk of rupture If there is still a residual hourglass impression on the balloon during inflation, then the ventriculoarterial junction itself may be hypoplastic and the procedure will have limited benefit In some patients with a dysplastic pulmonary valve, attempts can be made to use a balloon that may accept higher inflation pressures, in particular if a low-pressure compliant balloon such as the Tyshak II was used for the initial inflation Following the first inflation, most operators inflate one or more times and study the way that the balloon inflates and deflates to determine whether an hourglass impression is still caused by the pulmonary valve After inflation and careful withdrawal, the pressure in the right ventricle and the gradient across the pulmonary valve should be recorded The position of the wire can be preserved using a monorail catheter or an end-hole catheter and a Tuohy-Borst adaptor Alternatively, a pressure wire can be used to assess the valvar and subvalvar gradient without having to completely withdraw the wire into the right ventricle In patients beyond infancy, recrossing the valve with a balloon-tipped catheter is usually easily accomplished This differs from the procedure on neonates with severe or critical pulmonary valve stenosis, where an infundibular subpulmonary narrowing may become more apparent once the right ventricular pressure decreases after valvuloplasty Careful pullback will show whether any residual gradient is confined to the pulmonary valve or indeed is present in the subvalvar right ventricular outflow tract If there is a significant valvar gradient, the decision to reattempt dilation with a larger balloon can be made The presence of a significant subvalvar gradient is a well-described phenomenon after dilation of the pulmonary valve and can have serious consequences with a low-cardiac-output state This is the