24-hour ambulatory blood pressure monitoring in children with familial dysautonomia

Respiratory and cardiovascular indicators of autonomic nervous system dysregulation in familial dysautonomia

Familial dysautonomia (FD) is a profound sensory and autonomic nervous system disorder associated with an increased risk for sudden death. While bradycardia resulting from loss of sympathetic tone has been hypothesized to play a role in this mortality, extended in-home monitoring has failed to find evidence of low heart rates in children with FD. In order to better characterize the specific cardio-respiratory pathophysiology and autonomic dysregulation in patients with FD, 25 affected children and matched controls were studied with in-home technology, during day and night. Respiratory and heart rate timing and variability metrics were derived from inductance plethysmography and electrocardiogram signals. Selective shortening of inspiratory time produced an overall increase in respiratory frequency in children with FD, with higher daytime respiratory variability (vs. controls), suggesting alterations in central rhythm generating circuits that may contribute to the heightened risk for sudden death. Overall heart rate was increased and variability reduced in FD cases, with elevated heart rates during 20% of study time. Time and frequency domain measures of autonomic tone indicated lower parasympathetic drive in FD patients (vs. controls). These results suggest withdrawal of vagal, rather than sympathetic tone, as a cause for the sustained increase and dramatic lability in respiration and heart rates that characterize this disorder.

Echocardiographic abnormalities in familial dysautonomia

Sudden death accounts for up to 43% of all deaths in patients with familial dysautonomia (FD). The classic features of FD, namely, autonomic dysfunction, high blood pressure, and blood pressure labiality, are all risk factors for cardiac remodeling and hypertrophy. Myocardial remodeling and hypertrophy are independent risk factors for arrhythmias, cardiovascular events, and sudden death. An extensive review of the medical literature found no documentation of structural heart defects or myocardial remodeling in patients with FD. Sixteen patients with FD underwent physical examination, in-clinic blood pressure measurements, and echocardiographic study. On the basis of the findings, the patients were categorized by left ventricular geometric pattern. Twenty-four-hour ambulatory blood pressure monitoring was recommended to all participants. The majority of FD patients were found to have very high blood pressure values both during in-clinic measurements and during ambulatory blood pressure monitoring. Echocardiographic abnormalities were found in 43.75% of the study group; 18.75% of the study group had concentric hypertrophy, among which severe hypertrophy was found in 2 patients. Unknown previously, cardiac remodeling or hypertrophy is common in FD. We recommend that routine cardiac echocardiography be performed in this population, and attempts to treat high blood pressure should begin earlier in life.

Utility of ambulatory blood pressure monitoring in children and adolescents

Diagnosis of hypertension is critically dependent on accurate blood pressure measurement. "Accurate" refers to carefully following the guidelines for blood pressure measurement laid out for children and adults to minimize observer and subject errors that commonly occur in clinical blood pressure measurement. Accurate blood pressure measurement is more important in children and adolescents as the misdiagnosis of hypertension may have a life-long adverse impact on insurability and employment. Automated blood pressure measurement offers multiple advantages in achieving high-quality blood pressure determinations by reducing observer errors. The most commonly used form of automated blood pressure measurement is 24-h ambulatory blood pressure measurement (ABPM). Information on ABPM in children has grown exponentially over the last decade. Normative data exists for diagnosis of hypertension in children using ABPM including a novel method for determining normal values with the LMS method. There is further information about the utility of different determinants of 24-h blood pressure such as dipping status, morning surge and blood pressure load. ABPM has been able to detect significant differences in blood pressure in many disease states in children including chronic renal failure, polycystic kidney disease, solitary functioning kidney, and after renal transplantation. Increasingly nonambulatory automated blood pressure determinations have been used in management of hypertension in children. Although nonambulatory automated readings lack information about nocturnal blood pressure or blood pressure during daily activity, studies have suggested that home automated blood pressure measurements are a helpful adjunct to the usual office blood pressure reading.