Balloon dilatation of the stenosed aortic valve: how does it work? Why does it fail?

[Interventions in congenital heart disease and their sequelae in adults]

The advancements of cardiac surgery over the last decades led to larger numbers of patients with operated congenital heart diseases surviving into adulthood. In Germany it is estimated that over 120,000 adults have operated congenital heart diseases. Five to 7% of them will need yearly hospital admissions. Interventional procedures are additional tools used to treat these patients with various sequelae or residua (Table 1). In the following review we concentrate on 2 different interventional procedures: dilatation and stent implantations for treatment of stenosis and the different devices used for the closure of shunt lesions. For congenital valvular pulmonary stenosis, balloon dilatation is the therapy of choice regardless the age of the patient. Stent implantation for the treatment of peripheral pulmonary stenosis (e.g., after previous systemic pulmonary shunts) can decrease the need for redo surgery, which is accompanied with increased risk. Stent implantations proved also to be useful to treat stenoses after Mustard patch in patients with transposition of the great arteries, after Fontan procedures or dealing with the rare pulmonary venous stenosis. In contrast, dilatation of bioprosthesis and conduit stenosis are not promising. Balloon dilatation of valvular aortic stenosis is an accepted therapy in childhood up to adolescents. Table 2 compares a surgical series including many infants with critical aortic stenosis with a series of balloon dilatation in children and another one in adults regarding lethality, complications, and results. Table 3 illustrates the immediate and late results of balloon dilatation of aortic coarctation in 3 different studies. The high recurrence rate in infants made clinicians refrain from taking this age group for balloon dilatation. In children and adult patients, good results are reported (75% reduction of gradients). The complication rate is low (2.3 to 3.3%) and aneurysm formation rate seldom (1 to 7%). Stenosed aorto-pulmonary collaterals will rarely need balloon dilatation. Surgical closure of atrial septal defect is a low risk procedure with a very low rate of residual shunts (2%). Of the 5 available devices for transcatheter closure of atrial septal defect Type II, only 2 occluders are in use in Germany, the Clamshell and the Amplatzer device. The largest clinical studies of the different systems, their efficacy, complications and residual shunt rate are presented in Table 4. For the deployment of these occluders a TEE is always needed. There are many more systems in clinical use to close the patent arterial duct (PDA) (Table 5). The Ivalon plug as well as the Rashkind device have probably only historical value. Different types of coils (Gianturco, Cook detachable, PFM) are now in use worldwide. The reason for their widespread use, besides their easy application, is the fact that most coils are relatively cheap and need only small sheaths for deployment. Their further evaluation identified a residual shunt rate of 5% as well as a number of complications (embolization, hemolysis, stenosis of the left pulmonary artery) in 0 to 6%. For the large PDA the Amplatzer device has recently been introduced. An additional indication for the use of the different occluding devices are aorto-pulmonary collaterals, venovenous fistulae, pulmonary or coronary artery fistulae. Aorto-pulmonary collaterals are often associated with complex cardiac lesions and occasionally appear after palliative procedures. An excellent cooperation between adult and pediatric cardiologists is needed in order to offer the group of adults with congenital heart diseases an adequate and comprehensive management.

Resection of subvalvular aortic stenosis. Surgical and perioperative management in seven dogs

Open heart surgery was performed during cardiopulmonary bypass (CPB) to surgically correct subvalvular aortic stenosis in seven dogs. After initiation of total CPB, cardiac arrest was induced by antegrade and retrograde administration of blood cardioplegia. The subvalvular fibrous stenosis was resected through a transverse aortotomy. Intraoperatively and postoperatively, dobutamine, nitroprusside, lidocaine, blood(-products), and crystalloid solutions were used to manage hypotension and optimize cardiac index. Aortic cross-clamp time varied from 73 to 166 minutes, and duration of CPB varied from 130 to 210 minutes. Iatrogenic incision into the mitral valve in two dogs was the most significant intraoperative complication. Postoperative complications included: hypoproteinemia (n = 7), premature ventricular depolarization (n = 6), increased systemic vascular resistance index (n = 5), increased O2 extraction (n = 3), pulmonary edema (n = 2), and decreased cardiac index (n = 1). All seven dogs were discharged alive and in stable condition. Six dogs are alive and in stable condition after a mean follow up of 15.8 months. This is the first detailed report of CPB in a series of clinical veterinary patients. Using the techniques described in this paper, open heart surgery of considerable duration can be performed successfully in dogs with significant myocardial hypertrophy and endomyocardial fibrosis secondary to subvalvular aortic stenosis.

Closed transventricular dilation of discrete subvalvular aortic stenosis in dogs

Discrete subvalvular aortic stenosis with peak systolic pressure gradients of more than 60 mm Hg was treated by closed transventricular dilation in six young dogs. Peak systolic pressure gradients were measured by direct catheterization before surgery, immediately after dilation, and 3 months after surgery. Maximum instantaneous pressure gradients were measured by continuous wave Doppler echocardiography before surgery and 6 weeks to 9 months after surgery. All dogs survived the procedure, and two dogs were clinically normal after 9 and 14 months. Two dogs died at week 6 and month 7. One dog was receiving medication for pulmonary edema 15 months after surgery. One dog underwent open resection of the subvalvular ring at month 3, and was clinically normal 6 months after the second procedure. Complications included intraoperative ventricular fibrillation in one dog, and mild postoperative aortic insufficiency in one dog. Closed transventricular dilation resulted in an immediate 83% decrease in the peak systolic pressure gradient from a preoperative mean of 97 +/- 22 mm Hg to a mean of 14 +/- 15 mm Hg. However, systolic pressure gradients measured by direct catheterization at month 3 (77 +/- 26 mm Hg), and by Doppler echocardiography at week 6 to month 9 (85 +/- 32 mm Hg) were not significantly different from preoperative values, which suggested recurrence of the aortic stenosis. Closed transventricular dilation should not be considered a definitive treatment for discrete subvalvular aortic stenosis in dogs, but may be useful in young dogs with critical aortic stenosis as a bridge to more definitive surgery.

Clinical and Doppler echocardiographic follow-up after percutaneous balloon valvuloplasty for aortic valve stenosis

Percutaneous balloon valvuloplasty has been shown to increase the aortic orifice area and to improve clinical symptoms. However, there are only few data concerning long-term results after balloon valvuloplasty. In this study, 36 patients (11 men, 25 women, mean age 75 +/- 8 years) were followed after balloon valvuloplasty for a period of up to 18 months by means of clinical parameters and repeated Doppler echocardiographic measurements after 1, 3, 6, 12 and 18 months. Invasive measurements revealed a decrease of the systolic peak gradient from 78 +/- 24 to 38 +/- 13 mm Hg (p less than 0.001), and an increase in the aortic orifice area from 0.58 +/- 0.23 to 0.93 +/- 0.2 cm2 (p less than 0.001). The Doppler echocardiographic approach revealed that the maximal instantaneous gradient decreased from 96 +/- 26 to 67 +/- 22 mm Hg (p less than 0.001). The aortic orifice area increased from 0.49 +/- 0.16 to 0.73 +/- 0.21 cm2 (p less than 0.001). Three patients (8%) died in the hospital. After hospital discharge, 16 patients (44%) died and 8 patients (22%) underwent successful aortic valve replacement after a mean follow-up of 8 +/- 6 months. Nine patients (25%) were alive after a follow-up period of 18 months. Seven of these (19%) remained clinically improved. During follow-up, the Doppler echocardiographic results revealed a continuous trend toward the preprocedural severity of the aortic valve stenosis. Progression of restenosis assessed by Doppler echocardiographic measurements was accelerated in the group of patients who subsequently died or underwent repeat balloon valvuloplasty or aortic valve replacement.