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

Parasympathetic neurons derived from human pluripotent stem cells model human diseases and development

Autonomic parasympathetic neurons (parasymNs) control unconscious body responses, including "rest-and-digest." ParasymN innervation is important for organ development, and parasymN dysfunction is a hallmark of autonomic neuropathy. However, parasymN function and dysfunction in humans are vastly understudied due to the lack of a model system. Human pluripotent stem cell (hPSC)-derived neurons can fill this void as a versatile platform. Here, we developed a differentiation paradigm detailing the derivation of functional human parasymNs from Schwann cell progenitors. We employ these neurons (1) to assess human autonomic nervous system (ANS) development, (2) to model neuropathy in the genetic disorder familial dysautonomia (FD), (3) to show parasymN dysfunction during SARS-CoV-2 infection, (4) to model the autoimmune disease Sjögren's syndrome (SS), and (5) to show that parasymNs innervate white adipocytes (WATs) during development and promote WAT maturation. Our model system could become instrumental for future disease modeling and drug discovery studies, as well as for human developmental studies.

Transient third-degree atrioventricular block during anesthesia in a cat

Background:

Third-degree atrioventricular block (AVB) is usually permanent, with transient cases being rare. Cats with transient third-degree AVB. It had been not reported in detail.

Case Description:

A 9.3-year-old, male shorthair cat was evaluated for possible nervous disease resulting from otitis interna. Under propofol and isoflurane anesthesia, this cat developed a third-degree AVB. Isoproterenol was administered by continuous infusion to increase its heart rate. During recovery, heart rate returned to sinus bradycardia together with first-degree AVB without medical treatment. The cause of transient AVB was not observed at the examination.

Conclusion:

The case of this cat suggests that anesthesia can result in a transient third-degree AVB.

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.

Asymptomatic complete atrioventricular block in a 13-year-old girl

Atrioventricular (AV) block is a delay or an interruption in the transmission of an impulse from atria to ventricles due to an anatomic or a functional impairment in the conduction system. Atrioventricular block may be congenital or acquired. Electrocardiographic screening of asymptomatic school-aged children (median, 12.4 years) in Japan found the prevalence of a third-degree AV block to be 2 per 100,000. We report a case of asymptomatic complete AV block of unknown etiology in a 13-year-old child who did not require pacemaker placement. The importance of recognizing an asymptomatic complete AV block in the pediatric population, the classification and controversies of pacemaker placement, and the complications of pacemaker placement are discussed.

Cardiac sympathetic hypo-innervation in familial dysautonomia

OBJECTIVE

Familial dysautonomia (FD) involves incomplete development of the sympathetic nervous system. Whether such loss extends to sympathetic innervation of the heart has been unknown. This study used 6-[(18)F]fluorodopamine neuroimaging to assess cardiac sympathetic innervation and function in FD.

METHODS

Six adult FD patients underwent thoracic PET scanning for 30 minutes after i.v. 6-[(18)F]fluorodopamine injection, as did healthy volunteers without (N = 21) or with (N = 10) pre-treatment by desipramine, which interferes with neuronal uptake and thereby simulates effects of noradrenergic denervation. Effective rate constants for uptake and loss were calculated using a single compartment pharmacokinetic model.

RESULTS

FD patients had decreased uptake and accelerated loss of 6-[(18)F]fluorodopamine-derived radioactivity in the interventricular myocardial septum (P = 0.009, P = 0.05) and ventricular free wall (P = 0.007, P < 0.001), compared to untreated controls. Desipramine-treated subjects had decreased uptake but normal loss of 6-[(18)F]fluorodopamine-derived radioactivity.

CONCLUSIONS

FD involves cardiac noradrenergic hypo-innervation. Since accelerated loss of 6-[(18)F]fluorodopamine-derived radioactivity cannot be explained by decreased neuronal uptake alone, FD may also involve augmented NE loss from extant terminals.