Children with sick hearts: towards anesthesia safety

Whilst caring for an asymptomatic child, one of the greatest concerns for the anesthesiologist is that anesthesia and surgery may unmask occult cardiac disease. Data from the 1998 to 2003 Pediatric Perioperative Cardiac Arrest (POCA) Registry, noted that the most common causes of cardiac arrest were cardiovascular (1). Cardiomyopathy (CM) whilst being exceedingly rare in children (1.24 cases per 100 000 children <10 years of age) (2) may, however, be a significant cause of unexpected perioperative cardiac arrest. Children with a known CM should also be considered at high risk for a perioperative mishap. The key to successful anesthesia management is consideration for the specific pathophysiologic subtype of CM and administration of an appropriate anesthetic. A literal definition of CM is a disease or disorder of heart muscle and predictably with such a vague definition, a diverse group of lesions is encompassed. There are five pathophysiologically different subtypes, namely: dilated, hypertrophic, restrictive, arrhythmogenic right ventricle and unclassified (2). The most common type is dilated CM (DCM) whilst arrhythmogenic right ventricular dysplasia (ARVC) and the unclassified group present less commonly (3). Children with CM can present at any age soon after birth, however, restrictive CM tends to present a little later, at about 2 years of age (3). In terms of diagnosis, there have been recent advances in the identification of genetic markers of CM. Gene investigation in related family members at risk for sudden cardiac death (SCD) has revealed the long arm of chromosome 10 being a particularly important site for mutations causing DCM (4). Hypertrophic CM (HCM) is now known to be caused by mutations in one of at least 12 sarcomeric or nonsarcomeric genes and is recognized as the most common cause of SCD in the children (5,6). Identification of gene probes is important for the management of siblings and family members of patients with CM, who may also be at risk for SCD. Assessing cardiac function at the bedside in CM is not easily achieved, since children are able to adapt physiologically very adequately until an advanced stage of the disease process. Because of this physiologic adaptation allowing relatively normal daily activity, echocardiologic assessment is required perioperatively. In a recent retrospective review in Pediatric Anesthesia, Williams et al. (7) add to our understanding of CM by determining prognostic indicators of adverse perioperative outcome in children with CM. The authors categorized patients into a mild to severe disease state, depending on the myocardial fractional shortening (FS) as measured by echocardiography. Patients with severe CM as denoted by an FS of <16%, are at increased risk of perioperative mishap. This may seem intuitive but to the best of our knowledge, up until now, these data have not been validated in a large enough cohort in the pediatric anesthesia literature. The authors use of FS to quantify cardiac function is noteworthy. FS, an approximate measure of left ventricular systolic function, is preferred to ejection fraction (EF), in patients with abnormally shaped hearts since EF requires a normal heart shape to render a meaningful value (8). This value may also depend on the expertise and abilities of the echocardiographer. Although anesthesiologists are familiar with FS and EF, these parameters may not be the most appropriate measures of myocardial functional Correspondence to: Dr Warwick Ames, Department of Pediatric Anesthesia, Duke University Medical Center, DUMC Box 3094, Durham, North Carolina, USA (email: ames2002@mc.duke.edu). Pediatric Anesthesia 2008 18: 195–197 doi:10.1111/j.1460-9592.2007.02306.x