Cardiac pacing in patients with familial dysautonomia

Beat-to-beat QT interval dynamics and variability in familial dysautonomia

Familial dysautonomia (FD) is a disease characterized by dysfunction of the autonomic and sensory nervous systems. During the last five decades, the average life span of patients with FD has increased substantially. Nevertheless, sudden or unexplained death remains the most common cause of death in FD. Recently, our group reported that cardiac remodeling and hypertrophy are common in FD patients. We also described asymptomatic contractile dysfunction in some FD patients. It was speculated that repolarization abnormalities increases the risk of sudden death in patients with FD. However, data regarding repolarization dynamics in FD patients are limited. Twelve patients with FD and 12 healthy individuals (age and sex matched) underwent 5-min electrocardiograms. Time domain analysis of QT dynamics, power spectral analysis, QT variability index (QTVI), and normalized QT variance (QTVN) were computed. There was no difference in the time domain analysis of QT dynamics parameters between the two groups. QTVI((RR)) was also not statistically different. QTVI((HR)) was lower in the FD group compared to controls, but both values were low (therefore not considered pro-arrythmogenic) compared to published data. QTVN, not influenced by heart rate variability, was significantly higher in the FD group (0.39 +/- 0.1% vs. 0.3 +/- 0.05%, p = 0.032). In conclusion, most QT dynamics parameters in patients with FD are similar to that of normal controls. Nevertheless, FD patients have significantly higher QTVN, which might indicate higher risk for ventricular arrhythmias.

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.

Late ventricular potentials and QT dispersion in familial dysautonomia

Familial dysautonomia is a worldwide disorder characterized by maldevelopment and dysfunction of the autonomic and sensory systems. Despite major improvements in disease management in recent years, sudden death remains the cause of death in up to 43% of patients. The aim of this study was to evaluate electrocardiographic markers of sudden death in familial dysautonomia. A comparative case series design was used. Electrocardiographic measurements were performed in 13 patients with familial dysautonomia, 7 male and 6 female, aged 9-46 years. QT was measured from all leads and corrected QT (QTc) was calculated with the Bazett formula. QT dispersion (QTd), a marker of arrhythmogenicity, was calculated and corrected for heart rate. Late ventricular potential parameters, predictive of arrhythmias, were calculated as well. Findings were compared to a matched control group using the Mann-Whitney-Wilcoxon test. A prolonged QT interval was noted in 30.7% of patients. Several QT dispersion parameters were significantly abnormal in the study group compared to the controls. All late potential parameters were within normal range in both groups. In conclusion, patients with familial dysautonomia commonly have electrocardiographic abnormalities and may be at a higher risk for adverse cardiac events.

Familial dysautonomia: frequent, prolonged and severe hypoxemia during wakefulness and sleep

Sudden unexplained deaths have been reported in 13% [corrected] of Familial Dysautonomia (FD) subjects. To characterize cardiorespiratory dysregulation in children with FD that might contribute to potential sudden death, respiratory inductance plethysmography (chest/abdomen), ECG, hemoglobin saturation, and pulse waveform (VivoMetrics, Inc.) were recorded in the home during daytime wakefulness and overnight sleep in 25 children with IKBKAP mutation-confirmed FD and 25 age-, and gender-matched controls. Breath-to-breath and beat-to-beat characterization of breathing, hemoglobin saturation, and heart rate was conducted. Children with FD had more frequent, prolonged, and severe episodes of hypoxemia than matched controls, awake and asleep. Though a small percent of the study time revealed bradycardia and apnea, the hypoxemia was the most prevalent pattern in FD and rarely occurred with related bradycardia. Though infrequent with desaturation or bradycardia, apnea was more prevalent in FD subjects than controls, and more apparent during sleep than wakefulness. Children with FD have cardiorespiratory dysregulation during wakefulness and sleep, likely representing alveolar hypoventilation. We hypothesize that the related repeated hypoxemia (and presumed related hypercarbia) may render individuals with FD more vulnerable to sudden death.

Documented transient third-degree atrioventricular block and asystole in a child with familial dysautonomia

An 11-year-old boy with familial dysautonomia presented with palpitations. Continuous 24-h Holter monitoring revealed intermittent high-grade atrioventricular block and asystole. The unopposed parasympathetic tone in patients with dysautonomia may make them susceptible to bradycardia and atrioventricular block. We recommend routine 24-h Holter monitoring screening and, when indicated, consideration of pacemaker implantation to reduce the high risk of sudden death phenomena in this patient population.