Familial atrial standstill with coexistent atrial flutter

Familial Atrial Standstill in Association with Dilated Cardiomyopathy

. Atrial standstill is an extremely uncommon arrhythmia that rarely appears to be familial and genetically determined. Atrial standstill has been associated with several conditions including, but not restricted to, congenital heart disease, valvular heart disease, conduction disturbances, Brugada syndrome, myocardial infarction, and amyloidosis. Only a few cases of familial clustering of atrial standstill have been reported so far. This report represents a family with atrial standstill associated with syncope, dilated cardiomyopathy, and sudden cardiac death.

A cardiac sodium channel mutation cosegregates with a rare connexin40 genotype in familial atrial standstill

Atrial standstill (AS) is a rare arrhythmia that occasionally appears to be genetically determined. This study investigates the genetic background of this arrhythmogenic disorder in a large family. Forty-four family members were clinically evaluated. One deceased and three living relatives were unambiguously affected by AS. All other relatives appeared unaffected. Candidate gene screening revealed a novel mutation in the cardiac sodium channel gene SCN5A (D1275N) in all three affected living relatives and in five unaffected relatives, and the deceased relative was an obligate carrier. In addition, two closely linked polymorphisms were detected within regulatory regions of the gene for the atrial-specific gap junction protein connexin40 (Cx40) at nucleotides -44 (G-->A) and +71 (A-->G). Eight relatives were homozygous for both polymorphisms, which occurred in only approximately 7% of control subjects, and three of these relatives were affected by AS. The three living AS patients exclusively coinherited both the rare Cx40 genotype and the SCN5A-D1275N mutation. SCN5A-D1275N channels showed a small depolarizing shift in activation compared with wild-type channels. Rare Cx40 genotype reporter gene analysis showed a reduction in reporter gene expression compared with the more common Cx40 genotype. In this study, familial AS was associated with the concurrence of a cardiac sodium channel mutation and rare polymorphisms in the atrial-specific Cx40 gene. We propose that, although the functional effect of each genetic change is relatively benign, the combined effect of genetic changes eventually progresses to total AS.

Genetic aspects of arrhythmias

Advances in the treatment and prevention of heart disease have led to consistently declining morbidity and mortality rates over the past 30 years. Despite these advances, therapy remains largely palliative. The development of curative therapies is limited by our lack of knowledge of the basic mechanisms of disease. In the next decade, we will probably change many of these current approaches from treating the crisis to preventing the disease. Molecular biology and genetics have elucidated several basic pathways. It is hoped that targeted therapies will prevent or arrest many of these cardiac diseases, in particular, arrhythmias and sudden death. With the discovery of the genes causing familial diseases like long QT, hypertrophic cardiomyopathy, and Brugada syndrome, we have identified several substrates responsible for triggering malignant arrhythmias.