Use of Large Balloon Catheter to Treat Infants With Pulmonary Valve Stenosis

Case Reports

Patient 1

In June 2017, a 3-month-old girl weighing 5.4 kg was admitted to our hospital for treatment of pulmonary valve stenosis (Table I). She had been born prematurely at 36 weeks' gestation (weight, 2.3 kg). After admission, she was transferred to our neonatal intensive care unit. Physical examination revealed a systolic heart murmur at the upper left sternal border despite the patient's showing no signs of heart failure or cyanosis. An echocardiogram revealed thickening and doming of the pulmonary valve and an estimated transpulmonary pressure gradient of 70 mmHg consistent with pulmonary valve stenosis.

TABLE I. Patient Characteristics at the Time of Balloon Pulmonary Valvuloplasty

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Balloon pulmonary valvuloplasty was performed with the patient under sedation with thiamylal sodium. A 5F sheath was inserted in the right femoral vein, and pressures were measured with a 5F Berman angiographic catheter (Gadelius Medical K.K.). The right ventricular (RV) pressure increased to a maximum of 94 mmHg, and the peak transpulmonary pressure gradient was 71 mmHg. A biplane right ventriculogram showed doming of the pulmonary valve (Fig. 1A). The end-systolic diameter of the pulmonary valve was 8.3 mm (Z score, 2.1). A 5F end-hole angiographic catheter (Gadelius Medical K.K.) was advanced across the stenotic pulmonary valve, after which a 0.018-in Thruway^™ exchange guidewire (Boston Scientific Corporation) was maneuvered into the distal left pulmonary artery. Next, a 12-mm TMP PED balloon catheter was inserted and advanced over the guidewire through the 5F sheath until it crossed the pulmonary valve (Fig. 1B). After its position was confirmed angiographically, the balloon was rapidly inflated with diluted contrast media until the balloon waist completely disappeared (Fig. 1C). The patient's RV pressure decreased to 53 mmHg, and her transpulmonary pressure gradient, to 32 mmHg. A postprocedural right ventriculogram showed full excursion of the pulmonary valve leaflets (Fig. 1D). No vascular injury, pulmonary or tricuspid valve regurgitation, or other complications were noted. The patient was discharged home 2 days after BPV. An echocardiogram at 7 months of age showed no recurrence of pulmonary valve stenosis.

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Discussion

The TMP PED balloon catheter, approved in 2016 by the Japanese Ministry of Health, Labor, and Welfare, is a double-lumen balloon catheter consisting of a thin shaft and a 20-mm-long semicompliant balloon made of polyamide elastomer; the varying sizes can be inflated to diameters of 4, 6, 8, 10, and 12 mm (Table II and Fig. 2).³ Its end-hole can accommodate either a 0.014-in guidewire (for 4- to 10-mm balloons) or a 0.018-in guidewire (for 12-mm balloons).³ The minimum sheath size is 3F for all series except for the 12-mm balloon, which requires a 4F sheath. The rated burst pressure is 4 atm at balloon diameters of 4, 6, and 8 mm and 3.5 atm at balloon diameters of 10 and 12 mm.³

TABLE II. Comparison of Balloon Catheters for Balloon Pulmonary Valvuloplasty in Infants

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The TMP PED is one of several balloon catheters available for BPV in neonates and young infants who have pulmonary valve stenosis. Other models include the Tyshak^® series (NuMED, Inc./B. Braun Interventional Systems Inc.), Z-MED II^™ (NuMED, Inc./B. Braun), and Sterling^™ Over-the-Wire (Boston Scientific). Table II summarizes the characteristics of each.

In young infants with isolated pulmonary valve stenosis, the median diameter of the pulmonary valve annulus has been estimated at 9.2 mm echocardiographically and 9.8 mm angiographically.⁴ When a single balloon is used to dilate the pulmonary valve, the recommended balloon diameter is 120% to 140% of the diameter of the accurately measured pulmonary valve annulus, or approximately 10 to 12 mm.⁴ When patients have a pulmonary valve annulus that is too large to dilate with a single balloon or a small femoral vein, then the double-balloon technique is recommended to avoid vascular injury and to achieve the desired treatment effect.⁵ However, obtaining the additional vascular access necessary to perform the double-balloon technique in infants is troublesome.⁵ Tricuspid valve injury is also a concern because the catheter must pass through the tendinous cords and papillary muscles of the tricuspid valve.⁵ Therefore, the single-balloon technique is preferred.

The 12-mm TMP PED balloon catheter is suitable for BPV in neonates and young infants with pulmonary valve stenosis because its thin shaft allows good trackability and pushability. Other 12-mm balloon catheters, such as the Tyshak II, are also suitable. However, the 12-mm TMP PED balloon requires a smaller guidewire (the Tyshak II, for example, requires a 0.025-in guidewire).

In the 2 cases reported here, we successfully treated infants with isolated pulmonary valve stenosis by performing BPV with a relatively large 12-mm TMP PED balloon through a small-diameter sheath. We reduced both patients' transpulmonary pressure gradient without causing valvular or vascular injuries. Together, these reports highlight the safety and feasibility of performing BPV with a 12-mm TMP PED balloon catheter in young infants with pulmonary valve stenosis.