An uncommon case of complete AV block.

BACKGROUND: Granulomatosis with polyangiitis (GPA) is a rare systemic inflammatory disorder characterized by vasculitis of the small vessels, as well as necrotizing granulomatous lesions, affecting mainly upper and lower respiratory tracts, lungs and kidneys. Cardiac involvement has traditionally been a rare manifestation of GPA, with misleading clinical presentation until late stages. Cardiac conducting tissue involvement is a rare and potentially life-threatening complication. CASE PRESENTATION: We report the case of a 45-year-old man diagnosed with GPA with typical symptoms, but also complete atrioventricular (AV) block at the onset of the disease. The echocardiogram was unremarkable but the cardiac magnetic resonance (CMR) showed evidence of inflammation of the basal and septal ventricle walls. Despite effective immunosuppressive therapy, a permanent pacemaker was required for recurring complete AV block. DISCUSSION: Conduction system abnormalities are a rare manifestation of GPA, due to granulomatous lesions within the conduction system, or arteritis of the atrioventricular nodal artery. Patients are often asymptomatic, so careful and regular screening for cardiac involvement in this multi-system condition is required, often with echocardiogram, electrocardiogram (ECG) monitoring and CMR. Early immunosuppressive treatment may reverse a complete AV block but a pacemaker implantation may sometimes be necessary.

Dobutamine potentiates arterial chemoreflex sensitivity in healthy normal humans.

beta-Adrenergic agonists may increase chemosensitivity in humans. We tested the hypothesis that the beta1-agonist dobutamine increases peripheral chemosensitivity in a double-blind placebo-controlled randomized and crossover study. In 15 healthy subjects, we examined the effects of dobutamine on breathing, hemodynamics, and sympathetic nerve activity (measured using microneurography) during normoxia, isocapnic hypoxia (10% O2), posthypoxic maximal voluntary end-expiratory apnea, hyperoxic hypercapnia, and cold pressor test (CPT). Dobutamine increased ventilation (7.5 +/- 0.3 vs. 6.7 +/- 0.2 l/min, P = 0.0004) during normoxia, markedly enhanced the ventilatory (16.1 +/- 1.6 vs. 11.4 +/- 0.7 l/min, P < 0.0001) and sympathetic (+403 +/- 94 vs. +222 +/- 5%, P < 0.03) responses at the fifth minute of isocapnic hypoxia, and enhanced the sympathetic response to the apnea performed after hypoxia (+501 +/- 107% vs. +291 +/- 38%, P < 0.05). No differences were observed between dobutamine and placebo on the responses to hyperoxic hypercapnia and CPT. Dobutamine increases ventilation during normoxia and potentiates the ventilatory and sympathetic responses to hypoxia in healthy subjects. Dobutamine does not affect the responses to hyperoxic hypercapnia and CPT. We conclude that dobutamine enhances peripheral chemosensitivity.