Congenital aortic stenosis is an obstructive heart disease of the left ventricular outflow tract due to congenital abnormalities in the development of the aortic valve and accounts for approximately 3-6% of congenital heart disease [1]. Most patients with congenital aortic stenosis do not present with clinical symptoms in childhood, whereas approximately 10% of patients with severe aortic stenosis present with cardiac insufficiency or even cardiogenic shock in the newborn or early infancy and require early treatment [2]. Percutaneous balloon aortic valvuloplasty (PBAV) is one of the effective means of treating pediatric congenital aortic stenosis, and this technique has been carried out in China since 1989, but the number of procedures is limited, especially balloon dilatation in neonates and small infants with severe AS, with high surgical risks, complications and mortality, and has not been seen in China reported. In this study, we analyzed and summarized the PBAV procedures performed in recent years in small infants with congenital severe aortic stenosis in our hospital.
Data and Methods
1. Subjects: Small infants with severe aortic stenosis admitted from June 2010 to March 2011 who met the inclusion criteria were randomly enrolled. Inclusion criteria: Patients with severe aortic stenosis under the age of 3 months. Severe aortic stenosis was defined as aortic stenosis combined with left ventricular enlargement and left heart insufficiency. Exclusion criteria: combined mitral stenosis, left ventricular dysplasia, aortic annular dysplasia, and combined cardiovascular malformations other than arteriovenous insufficiency. The legal guardians of the enrolled patients signed an informed consent form. A total of 4 children were included in this study.
2. Preoperative evaluation: X-ray chest radiographs, electrocardiograms and echocardiograms were routinely performed before surgery. Echocardiography was performed to assess the aortic leaflets, aortic annulus diameter, mitral annulus diameter, left ventricular size, left heart systolic function, aortic regurgitation and its degree, and whether aortic constriction and other cardiac malformations were combined. Perform arterial blood gas analysis and blood electrolyte examination to understand whether there is acid-base and water-electrolyte imbalance.
3. Preoperative adjustments: For patients with severe aortic stenosis with combined left heart insufficiency, apply positive inotropic drugs and diuretics preoperatively. For critically ill neonates with aortic stenosis who rely on arterial catheter opening to maintain effective body circulation, intravenous prostaglandin E2 is applied to maintain arterial catheter opening. In critically ill patients with combined respiratory or circulatory failure, apply mechanical ventilation. Maintain water and electrolyte balance and acid-base balance.
4. PBAV method [3]: Routine percutaneous femoral arterial and venous cannulation with heparin 100 U/kg anticoagulation. Right heart catheterization was performed first, and then a pigtail catheter was inserted through the femoral artery to reach the ascending aorta. Ascending aortic manometry was performed first, and ascending aortography was performed in parallel to observe aortic regurgitation and negative valve jet, and the diameter of the aortic annulus was measured. According to the measured aortic annulus diameter, a suitable balloon dilation catheter is prepared. Take a soft-tipped guidewire and insert it directly into the left ventricle via a pigtail catheter or an end-hole catheter, following the guidewire to insert the catheter. After the catheter is inserted into the left ventricle, the guidewire is withdrawn and the catheter is left in the left ventricle. The left ventricular pressure and peak transvalvular systolic pressure difference were measured, and then a 260 cm long J-shaped stiffened guidewire was inserted from the catheter into the left ventricle. The balloon is inserted through the guidewire to dilate the catheter, and when the center of the balloon rides right over the aortic valve orifice, the balloon is dilated until the lumbar recess disappears, followed by rapid aspiration of the balloon. This is repeated several times, with each interval of about 5 min. After PBAV, cardiac catheterization was performed to remeasure the peak transvalvular systolic pressure difference, and ascending aortography was performed to evaluate the degree of aortic stenosis release and whether aortic regurgitation occurred or worsened. After the procedure, local compression was applied to stop the bleeding. Echocardiography was performed again immediately after the operation to understand the presence of pericardial effusion and aortic regurgitation, and to measure the transvalvular peak systolic pressure difference and left ventricular ejection fraction (LVEF).
5.Follow-up: Follow-up was performed 1 month after PBAV, and X-ray chest radiograph, electrocardiogram and echocardiogram were reviewed.
6.Statistical analysis: SPSS 16.0 software was used for statistical analysis. The measurement data were expressed as ±s. One-way ANOVA was used for comparison between multiple groups, and LSD-t test was used for comparison between two groups. p<0.05 was considered a statistically significant difference.
Results
1, General: four children were (50±25) d (34-87 d) old at the time of surgery, three were male and one was female, and had a body mass of (3.89±0.85) kg (2.8-4.8 kg). All children had different degrees of cardiac insufficiency such as shortness of breath, nausea, pauses in breastfeeding, increased heart rate, and enlarged liver on admission, and LVEF measured by echocardiography was less than 50%. One patient had preoperative respiratory failure and was given mechanical ventilation. two patients had acidosis and water-electrolyte imbalance and were given acid correction and electrolyte supplementation. all four patients had myocardial strain such as ST-segment depression and T-wave inversion in the left thoracic leads on the ECG. Echocardiographic examination showed that the aortic valve was functional bilobed valve in 3 cases and trilobed valve in 1 case; pericardial effusion in 3 cases; no mitral stenosis, left ventricular dysplasia and aortic annular dysplasia.
2. efficacy of PBAV: 4 patients with preoperative aortic annular diameter (8.2±0.9) mm, balloon diameter/annular diameter ratio of 0.92±0.06 (0.86-1.0), and balloon length of 20-40 mm underwent successful PBAV. peak transvalvular systolic pressure difference measured by ultrasound Doppler decreased from (60.6±15.2) mm Hg (1 mm Hg=0.133 kPa) preoperatively to (29.6±15.2) mm Hg (1 mm Hg=0.133 kPa) immediately postoperatively. (29.5±8.0) mm Hg in the immediate postoperative period (P<0.01); LVEF was (47.6±7.5)% preoperatively and (52.2±18.9)% in the immediate postoperative period (P>0.05). Two children had severe bradycardia during balloon dilatation, but their heart rates returned to normal after 1:10,000 epinephrine intravenous infusion and cardiopulmonary resuscitation without other serious complications.
All four children were followed up at 1 month after surgery. Echocardiography showed a transvalvular systolic peak pressure difference of (36.5±11.0) mm Hg, which was significantly lower than before surgery (P<0.05) and not statistically significant when compared with the immediate postoperative period (P>0.05); LVEF was (81.0±1.1%), which was significantly higher than before and immediately after surgery (P<0.01); and aortic regurgitation was mild to mild. All children showed no cardiac insufficiency and did not require reintervention or surgery (Table 1).
Table 1 Pre- and post-interventional data of 4 small infants with severe aortic stenosis
Case number
Preoperative
Immediate postoperative
1 month postoperatively
Transvalvular systolic peak pressure difference (mm Hg)
Echocardiography Cardiac catheterization
LVEF (%)
Transvalvular peak systolic pressure difference (mm Hg)
Echocardiography Cardiac catheter
LVEF
(%)
AI
Transvalvular peak systolic pressure differencea
(mm Hg)
LVEF
(%)
AI
1
79.6 80.0
39.3
44.6
49.3
57.0
20.6 24.0
24.7
Slight
20.4
81.8
Mild
2
49.8 47.0
26.0 None b
67.7
Slight
39.6
80.2
Slight
3
46.9 63.0
32.3 29.0
58.9
Slight
45.0
79.9
Mild
4
65.9 45.0
39.2 None b
57.6
Mild
40.9
82.1
Mild
Note: a measured by echocardiography; b due to postoperative cardiopulmonary resuscitation, postoperative cardiac catheterization was not used to measure peak transvalvular systolic pressure difference; LVEF: left ventricular ejection fraction; AI: aortic regurgitation; 1 mm Hg = 0.133 kPa
Discussion
Severe aortic stenosis in neonates and small infants differs significantly from older pediatric and adult patients in terms of pathophysiology, clinical presentation, and principles of management. Myocardial oxygen consumption is increased by left ventricular hypertrophy secondary to severe left ventricular outflow tract obstruction. In addition, excessive systolic pressure has a compressive effect on the subendocardial myocardium, which affects myocardial blood supply and produces subendocardial myocardial ischemia, which leads to a series of changes such as myocardial fibrosis, left ventricular dilatation, and left heart failure. Body circulation in neonates with critical aortic stenosis is often dependent on the arterial catheter for maintenance, and self-closing of the arterial catheter can lead to circulatory collapse and even death [4].
In pediatric patients with congenital aortic stenosis, the degree of aortic stenosis is usually assessed using the peak transvalvular systolic pressure difference, and if the peak transvalvular systolic pressure difference is greater than 50 mm Hg on cardiac catheterization, it can be used as an indication for intervention or surgery. However, in patients with aortic stenosis in neonates or infants with combined left ventricular enlargement, left ventricular insufficiency, or body circulation dependent arterial catheter opening, intervention or surgery should be considered regardless of the level of transvalvular peak systolic pressure difference [5]. In the present study, all 4 patients had severe aortic stenosis, and in 2 of them, although the preoperative transvalvular peak systolic pressure difference was less than 50 mm Hg, there was significant cardiac insufficiency with LVEF less than 50%. Transvalvular peak systolic pressure difference in the presence of left heart insufficiency does not accurately reflect the degree of aortic stenosis and tends to underestimate the severity of aortic stenosis. The above 2 patients were diagnosed with severe aortic stenosis by confirming the presence of morphologically severe stenosis in the aortic valve by 2D echocardiography, along with clinical manifestations of left heart insufficiency, and were therefore selected for PBAV treatment, and the 2 patients experienced significant improvement in cardiac function after surgery due to the relief of the valve stenosis.
Severe aortic stenosis in neonates and small infants has a high anatomic variability and requires the selection of an appropriate surgical approach on a case-by-case basis. During preoperative echocardiography, mitral annular diameter, left ventricular diameter, and aortic annular diameter need to be measured. If there is significant mitral valve and left ventricular dysplasia, the Norwood procedure should be chosen [6] and treated as a single ventricle; if the mitral valve and left ventricle are still well developed and the aortic annulus is dysplastic, the Ross+Konno procedure may be considered; if the mitral valve, left ventricle, and aortic annulus are all well developed, PBAV or surgical valve junctional dissection may be chosen [7]. In this study, all patients were evaluated preoperatively by echocardiography for mitral valve, left ventricular, and aortic annulus development, and mitral stenosis, left ventricular dysplasia, and aortic annulus dysplasia were used as exclusion criteria; the four patients enrolled had well-developed mitral, left ventricular, and aortic annuli, so PBAV was chosen and achieved the desired outcome.
Patients with severe aortic stenosis in neonates and small infants are often critically ill, often combined with cardiac insufficiency and even cardiogenic shock, and can be combined with respiratory failure, acid-base and water-electrolyte balance disorders, and should be systematically evaluated preoperatively. For patients with cardiac insufficiency, positive inotropic drugs and diuretics are required; for patients with critical neonatal aortic stenosis whose body circulation depends on the opening of the arterial catheter, prostaglandin E2 can be applied to maintain the opening of the arterial catheter to maintain effective blood flow in the body circulation; for patients with respiratory or circulatory failure, mechanical ventilation should be used; for patients with combined acid-base or water-electrolyte disorders, timely For patients with combined acid-base or water-electrolyte disorders, timely correction should be performed. In this study, all four patients had different degrees of cardiac insufficiency, and were treated with cardiac stimulation and diuresis after admission, which improved the cardiac function and LVEF to some extent before surgery. These measures helped to improve the systemic condition of the children and create better conditions for PBAV surgery.
Complication rates and mortality rates are higher in neonates and small infants with PBAV than in older children. In an early retrospective study, the incidence of surgical death was as high as 9% due to left ventricular perforation, severe aortic regurgitation, and sepsis due to prolonged operation [8]. Due to technological advances, many of the previous complications could have been prevented and avoided using current diagnostic tools and catheterization techniques. A recent study with a large sample showed that early morbidity and mortality in neonates with PBAV was about 4%, the incidence of moderate to severe aortic regurgitation was 15%, small left ventricular and aortic annular development was a risk factor for long-term survival, and a large balloon diameter/annular diameter ratio was a risk factor for the development of aortic regurgitation [9]. In this study, balloon diameter/annular diameter ratios of 0.86 to 1.0 were used, and after balloon dilatation, the peak transvalvular systolic pressure difference was significantly reduced and the children’s cardiac functional status improved significantly. None of the children required further interventions or surgical procedures at follow-up. Except for 2 patients with severe intraoperative bradycardia, no other serious complications occurred, and postoperative aortic regurgitation was only mild to mild.
In this study, all 4 small infants with severe aortic stenosis achieved better recent results after PBAV. Preoperative patient selection and adjustment of systemic status are important prerequisites for successful surgery, and the selection of an appropriately sized balloon catheter is a key factor in ensuring surgical efficacy and reducing aortic regurgitation. Studies have shown that PBAV is a safe and effective treatment for severe aortic stenosis in small infants in the absence of a combined aortic annulus and left ventricular dysplasia. However, for most patients with aortic stenosis, PBAV remains only a palliative treatment [10].