Anti b-adrenergic receptor antibodies in inappropiatesinus tachycardia syndrome: a novel physiopatogenicfactor?

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Abstract

Introduction

The inappropriate sinus tachycardia syndrome has beenattributed to an increase in the intrinsic sinus rate, associ-ated to a b-adrenergic hypersensitivity and a greatly de-pressed response to the cardiovagal reflex. However, the roleof an immunoregulatory dysfunction involving the auto-nomic membrane receptors has not been investigated.

Objective

To assess the prevalence of anti b-adrenergic receptor anti-bodies and anti M2-cholinergic receptor antibodies in patients with inappropriate sinus tachycardia syndrome.

Methods

Ten patients (females; age: 21-64 years old) with inappro-priate sinus tachycardia syndrome and 10 healthy volunteers were studied. The presence of b-adrenergic and M2-cholinergic receptor antibodies was assessed by thechronotropic effects of the IgG fraction on cultured ratcardiomyocites before and after exposure to atropine andpropranolol.

Results

No anti-autonomic receptor antibodies were detected withinthe IgG fraction of the healthy volunteers. Conversely, 8 of10 patients with inappropriate sinus tachycardia syndromehad circulating antib-adrenergic receptor antibodies (80%,p = 0.0004), but none of them had anti M2-cholinergic re-ceptor antibodies.

Conclusions

A high percentage of the patients with inappropriate sinustachycardia syndrome had circulating antibodies that rec-ognized and stimulated b-adrenergic receptors. This find-ing suggest that an immunoregulatory dysfunction involv-ing theb-adrenergic receptors might participate in thepathogenesis of this syndrome.