Echocardiographic abnormalities in familial dysautonomia

Afferent Baroreflex Dysfunction: Decreased or Excessive Signaling Results in Distinct Phenotypes

Head and neck tumors can affect afferent baroreceptor neurons and either interrupt or intermittently increase their signaling, causing blood pressure to become erratic. When the afferent fibers of the baroreflex are injured by surgery or radiotherapy or fail to develop as in familial dysautonomia, their sensory information is no longer present to regulate arterial blood pressure, resulting in afferent baroreflex failure. When the baroreflex afferents are abnormally activated, such as by paragangliomas in the neck, presumably by direct compression, they trigger acute hypotension and bradycardia and frequently syncope, by a mechanism similar to the carotid sinus syndrome. We describe our observations in a large series of 23 patients with afferent baroreflex dysfunction and the cardiovascular autonomic features that arise when the sensory baroreceptor neurons are injured or compressed. The management of afferent baroreceptor dysfunction is limited, but pharmacological strategies can mitigate blood pressure swings, improve symptoms, and may reduce hypertensive organ damage. Although rare, the prevalence of afferent baroreflex dysfunction appears to be increasing in middle-aged men due to human papillomavirus related oropharyngeal cancer.

A Controlled Trial of Inhaled Bronchodilators in Familial Dysautonomia

BACKGROUND

Chronic lung disease is a leading cause of premature death in patients with familial dysautonomia (FD). A significant number of patients have obstructive airway disease, yet it is not known whether this is pharmacologically reversible.

METHODS

We conducted a double-blind, placebo-controlled, randomized clinical trial comparing the beta 2 agonist albuterol with the muscarinic blocker ipratropium bromide in patients homozygous for the IKBKAP founder mutation. Albuterol, ipratropium bromide, and placebo were administered on 3 separate days via nebulizer in the seated position. Airway responsiveness was evaluated using spirometry and impulse oscillometry 30 min post dose. Cardiovascular effects were evaluated by continuous monitoring of blood pressure, RR intervals, cardiac output, and systemic vascular resistance.

RESULTS

A total of 14 patients completed the trial. Neither active agent had significant detrimental effects on heart rate or rhythm or blood pressure. Albuterol and ipratropium were similar in their bronchodilator effectiveness causing significant improvement in forced expiratory volume in 1-s (FEV1, p = 0.002 and p = 0.030). Impulse oscillometry measures were consistent with a reduction in total airway resistance post nebulization (resistance at 5 Hz p < 0.006).

CONCLUSION

Airway obstruction is pharmacologically reversible in a number of patients with FD. In the short term, both albuterol and ipratropium were well tolerated and not associated with major cardiovascular adverse events.

Familial dysautonomia (Riley-Day syndrome): when baroreceptor feedback fails

Familial dysautonomia (FD) is a rare hereditary disorder caused by mutations within the gene that encodes for I-κ-B kinase complex associated protein (IKAP). A deficiency of IKAP affects the development of primary sensory neurons including those carrying baroreflex afferent volleys, a feature that explains their characteristic sensory loss and labile blood pressure. This review describes the history, the genotype of FD and the unusual cardiovascular autonomic phenotype of these patients. We outline the main consequences of a failure to receive information from arterial baroreceptors, including the characteristic "autonomic storms" and severe end-organ target damage.

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.