Dr. Paul Wang & Ursula Bellugi

We all know that no medical procedure is 100 % safe, so no procedure should be done unless it is truly needed. Unfortunately, many children with Williams syndrome do need surgical procedures and/or cardiac catheterization. Two possible complications relating to surgery and catheterization have recently come to light. Although both are rare, they are worth knowing about.

It now appears that a small number of children with Williams syndrome can have narrowing of the coronary arteries. These are the arteries that go from the aorta to the heart muscle itself. (These same arteries are narrowed in adults with atherosclerosis, but for a different reason.) All the WS kids who have had 'Coronary Artery Stenosis' also had SVAS (Supravalvular Aortic Stenosis), but that may not hold up as more cases are discovered. If severe, coronary narrowing can cause 'myocardial ischemia' - lack of blood to the heart itself - and the possibility of permanent damage to the heart. Some of the children with coronary stenosis that we have seen did have damaged, scarred hearts. While an EKG might show evidence of ischemia or damage that has occurred already, it is very difficult to diagnose coronary narrowing except by doing a catheterization.

Coronary artery stenosis can cause complications, including heart attack, during the catheterization procedure. Therefore, it is important that your cardiologist be aware of this possibility beforehand. Also, it is advised that "non-ionic contrast agents" be used during the catheterization, rather than "ionic agents". This could help reduce the risk of the procedure itself. A good reference is by EE Conway, J. Noonan, RW Marion, & CN Steeg, in Journal of Pediatrics, October 1990, vol. 117, pp. 593-595.

At the 1990 convention in Boston, one parent reported that her child had "Malignant Hyperthermia". This is a very rare complication of anesthesia in which the body temperature rises extremely quickly and extremely high soon after anesthesia is started. We are aware of another case of malignant hyperthermia in a child with WS. Also a journal article has been published about another child with WS who developed Masseter Spasm, which sometimes precedes malignant hyperthermia. In masseter spasm, the jaw muscles tighten and force the mouth closed.

Although treatable, malignant hyperthermia is potentially very serious. It sometimes runs in families, and it seems to be more frequent during surgery for strabismus, which many kids with Williams have. The anesthesia drugs most frequently associated with malignant hyperthermia are "succinycholine" and "halothane" (but even with these drugs, the occurrence is very rare). Again, the important thing is that the anesthesiologist be made aware of the association between Williams syndrome and malignant hyperthermia, so that appropriate precautions and the use of other anesthetic drugs can be considered. The journal article referencing this information is by J Patel & MJ Harrison, Anaesthesia, 1991, vol. 46, pp. 115-116 If you have any unanswered questions about coronary stenosis or malignant hyperthermia, be sure to bring them up with your child's regular physician, cardiologist or anesthesiologist.