Introduction
A great number of congenital cardiac lesions are now being treated by interventional cardiac catheterization techniques. Advances in equipment and devices have allowed for trans-catheter closure of some 75 per cent of all secundum atrial septal defects (ASDs), virtually all cases of patent arterial duct in childhood (except premature neonates) and a fair number of ventricular septal defects (VSDs) in older children. Further, virtually all cases of pulmonary valve stenosis and a large number of aortic valve stenoses from neonates to young adults are being treated by catheter balloon valvuloplasty. Intravascular stent designs have evolved and have proved highly effective in enlarging pulmonary arterial vessels, which may not be easily accessible to a cardiac surgical approach. Treatment of adolescent and adult native or re-coarctation is now virtually entirely catheter based. The development of trans-catheter devices is rapidly progressing – in the future, biodegradable devices will become commonplace, thereby further expanding the indication for trans-catheter treatment.
Cardiopulmonary bypass in itself carries mortality and morbidity. Increasingly, cardiac surgeons and interventional cardiologists work together to develop ways of treatment to make bypass times shorter and achieve highly successful patient outcomes at reduced risk. This so-called hybrid approach is evolving and is destined to become one of the major treatment avenues for congenital heart disease in the future. As these techniques become more commonplace and the availability of specifically designed hybrid cardiac theatres increases, there is likely to be a future training demand for cardiac surgeons to develop some of the wire skills required for cardiac catheter work. At the same time, there is a need to refine existing catheter equipment and to develop bespoke equipment to maximize on the true potential of these techniques (Figure 23.1).
Figure 23.1 Typical working field during a hybrid procedure in a 3-kg neonate. The tip of the sheath (arrow) is placed in the main pulmonary artery and is secured by a purse-string suture. Access is limited not only by the bypass cannulae and the sternal spreader but also by the X-ray tube some 10 cm above the surgical field.
Exit Angiography.
The routine use of intra-operative epicardial or trans-oesophageal ultrasound techniques has been established for more than two decades in surgery for congenital heart disease. However, ultrasound techniques are limited with regards to assessment of reconstructed pulmonary arteries and the aortic arch.
In the majority of patients after complex pulmonary artery reconstruction or unifocalization procedures, it is of value to assess the surgical results immediately after weaning off bypass in order to check on the integrity of the repair and the morphology of the reconstructed pulmonary arteries and obtain central pulmonary arterial pressures. At the end of the bypass run, the X-ray tube is moved into position. The right atrium or main pulmonary artery is punctured with a needle, and a 0.018-inch wire is placed, over which a No. 4 French short introducer sheath is inserted. The dilator sheath is removed, blood is aspirated, and pressures are transduced. A single dose of diluted contrast agent (0.5–1 mL/kg of body weight) is injected rapidly either manually or by pump whilst acquiring the images either at 15 or 30 frames per second. The passage through the lungs and the capillary bed is recorded and can be reviewed on the video monitors for detailed analysis. If significant narrowing of the reconstructed pulmonary arteries is identified, there must be a discussion as to whether (1) to accept the result for the time being, (2) whether to revise the observed lesion surgically or (3) whether to consider stent implantation. Balloon angioplasty for postsurgical strictures immediately after bypass is unsafe and probably ineffective. Stenting of such lesions is safer and allows one to straighten out any observed kinks. Running polypropylene sutures can safely be over-dilated to some 20 per cent.
Post-Bypass Atrial Septal Stenting.
In some cases, filling pressures after weaning from bypass may be excessively high after complete closure of an ASD. In such cases, a small atrial communication may be of benefit for early postoperative recovery. The right atrium can be punctured under direct vision, and the needle can be advanced under epicardial ultrasound guidance into the left atrium. A wire is introduced to the left atrium, and a No. 4 or 5 French short sheath is placed within the left atrium. A test injection is conducted to delineate the plane of the atrial septum under 30- to 40-degree left anterior oblique angiographic projection. A balloon catheter is then advanced across the atrial septum and inflated fully. The resultant communication will normally measure about half the chosen balloon diameter and is unlikely to remain open for a long time. More reliable communications can be created by placing a premounted coronary or renal stent. The stent is advanced across the atrial septum. The introducer sheath is withdrawn to the right atrial side, still covering part of the stent, and the balloon is inflated, to achieve flaring of the left atrial side. The sheath is then withdrawn well into the right atrial cavity. The balloon is inflated further so as to dilate the right atrial aspect of the stent to achieve a diablo configuration.
Peri-ventricular Device Closure of VSD.
The majority of muscular VSDs close spontaneously during the first six to 12 months of life. However, if a significant defect/shunt persists after six months of age, there may be a need for intervention. In cases with multiple defects and in the presence of cardiac failure, pulmonary artery (PA) banding may be indicated. However, peri-ventricular closure of the largest VSDs may be the better option.
After (limited) median sternotomy, the right ventricular cavity is entered by a needle, and an appropriately sized guide wire and sheath are advanced across the defect straight into the left ventricular cavity under ultrasound control (either direct epicardial or trans-oesophageal). Defect dimensions are measured in at least two planes during diastole, and an appropriately sized short sheath is selected. The device is placed under ultrasound control. Repeat angiography through the left atrial appendage with left anterior oblique and cranial angulation may be indicated to identify and plan closure of additional defects.
The same techniques can be employed after surgical correction of congenital heart disease when the post-bypass cardiac ultrasound study documents persistence of a residual muscular VSD.
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