Undesirable outcomes of pulmonary valve balloon dilatation 1. Mortality

In our study, one patient died on the 11^st day after valve dilatation and the cause of death was not related to the procedure. The patient was a 5-day old baby with body weight of 3.2 kg. The baby had SpO2

of 40% and class III heart failure before the procedure. Doppler echocardiography prior dilatation showed a critical pulmonary valve stenosis with the artery peak systolic pressure gradient of 92.4 mmHg and 16.2 mmHg after dilatation. The causes of dead was ventilator associated, pneumonia and pneumothorax. This patient presented evidence of high risk as 5-day-old infant, severe stenosis and severe heart failure. According to Colli and Tevfik's studies, causes of death related to the balloon dilatation procedure depends on specific characteristics of selected patients, for example patients with severe stenosis DMP, severe heart failure, infancy, the risk of higher mortality is from 6% to 30%. As the outcomes of dilatation performed by Endate et al in 55 patients, 3 patients (5.5%) died after the 6-72 hours following the procedure due to heart failure and intractable pulmonary edema.

4.4.2. The failure of balloon dilatation

Balloon dilatation procedure could not be performed for 3 patients and all of them required surgical valvotomy instead. We considered it as a failure of valve dilatation.

These 3 patients have common characteristics: were 2 - 3 months old, small weight, critical hospitalized conditions with SpO2 40 - 60%

and heath failure class III. Doppler echocardiography showed 2 patients of moderate pulmonary stenosis (systolic pressure gradient of 70 - 79 mmHg), the other patient of severe pulmonary stenosis (systolic pressure gradient of 103 mmHg). The diameter of the pulmonic-valve orifices were very small (1.9 - 3.3 mm), with the average of 2.7 ± 0.72 mm. They were smaller than the those of successful dilatation patients (3.1 ± 0.9 mm).

The surgical valvotomy for 3 patients showed that they all had very thick pulmonary valve and the leaflets were almost entirely fused together.

These failure cases were conducted in the early stages (in 2007 - 2010) of our center when we still did not have much experiences.

Sunethra et al. reported that, among 101 children aged less than 42 months with pulmonary valve stenosis and underwent dilatation, the failure rate was 5.9% as the pulmonary valve could not be crossed.

The reason of the failure was that patients had critical pulmonary stenosis and too small pulmonic-valve orifice diameter.

4.4.3. Pulmonary valve regurgitation after balloon dilatation After dilatation, the balloon used to separate leaflets might fused together and could partly tear edges of the valve. Other studies reported that the valve openings were mostly found when the balloon to valve ring diameter ratio is greater than 1.4 times. At 12-month follow up, 6.8% and 46.6% and 38.6% patients had pulmonary valve insufficiency level III, level II, level I respectively and no patients had pulmonary valve insufficiency level 4. The balloon of average balloon size to valve diameter ratio of 1.32 ± 0.94 times was used, in which 8 patients underwent the dilatation with the balloon to valve ring diameter ratio of ≥ 1.5 times. The outcomes showed that most of patients had pulmonary valve insufficiency level I, II and no patients had serious pulmonary valve insufficiency. It also demonstrated that there was no relationship between pulmonary valve insufficiency and the ratio of the size of the balloon to the diameter of the pulmonary valve in our study.

Other studies reported about 74 - 95.1% patients of pulmonary valve insufficiency after dilatation. Severe pulmonary valve insufficiencies were normally related to the physical valve damage such as tearing. Asim et al and Louisa et al suggested that there was no connection of the balloon size to the pulmonary valve diameter with the pulmonic-valve orifice. In contrast, studies by Berman et al showed that the pulmonary valve insufficiency was related to patient age (under 2 months old), the pulmonary stenosis degree and the balloon size (the balloon size to pulmonary valve diameter ratio of 1.33 - 1.5).

4.4.4. Complications after balloon dilatation for pulmonary valve stenosis

4.4.4.1. Rupture of tricuspid valve papillary muscle

One patient had rupture of tricuspid valve papillary muscle after dilatation in this study. The artery pressure gradients by Doppler echocardiography of pre and post dilatation were was 73.8 mmHg and 9.4 mmHg (intervention we had the first phase of intervention in 2010).

The reason for the rupture in other studies might be that the balloon was too long, or the balloon was under tricuspid valve papillary muscle, or the balloon inflation caused the rupture. But in our study, it was because of the balloon under tricuspid valve papillary muscle due to our lack of experience in the early stages.

4.4.4.2. Thrombosis

In our study, one patient had brain thrombosis (1% patients) probably due to a blood clot in the catheter, it would go from the right atrium, through the foramen ovale with left to right shunt. Hussein et al performed balloon dilatation in 37 infants of severe pulmonary stenosis, 2.7% patients had brain thrombosis. Christian et al performed balloon dilatation in 53 infants and neonates, 7.5% patients had thrombosis femoral vein, 1,9% patients had brain thrombosis and died after 3 days.

4.4.5. Re-stenosis after balloon dilatation of pulmonary valve stenosis

After dilatation, 5 patients (5.1%) were diagnosed with re-stenosis, only 2 patients (2%) required repeated balloon dilatation.

The balloon to valve ring diameter ratios were 1.24± 0.05 times and 1.25 ± 0.08 times in these 5 and 2 above patients respectively and 1.32 ± 0.1 times in 94 patients of free re-stenosis. Since the number of re-stenosis patients were too small, we could not find the factors associated with the balloon-to-valve ring ratio as well as the patient age.

Rao et al found that risk factor of re-stenosis was higher among pulmonary stenosis patients of balloon/annulus ratio under 1.2 times, while we could not find a similar result in our study.

The re-stenosis rate from other institutions reported as 10%

(patients) and it varied depending on the study population. For example, it was 5% by Mourad, 23% by McCrindle and 30% by Tevfik in infants of pulmonary stenosis with right ventricular hypoplasia.

CONCLUSION

We performed percutatnous balloon dilatation for pulmonary valve stenosis for 99 patients aged less than 2 years old and concluded.

1. The efficiency of the balloon dilatation for pulmonary valve