The SCN5A A1180V mutation exhibited a -4.5-mV shift of inactivation in vitro and was associated with longer resting corrected QT intervals in unaffected carriers compared to noncarriers.
Observational (n=32)
Does the SCN5A A1180V mutation alter Na+ channel function and associate with atrioventricular block and dilated cardiomyopathy in a familial cohort?
The novel SCN5A A1180V mutation alters Na+ channel function and is associated with a high risk for familial progressive adult-onset atrioventricular block and subsequent dilated cardiomyopathy.
BACKGROUND: Increased susceptibility to dilated cardiomyopathy has been observed in patients carrying mutations in the SCN5A gene, but the underlying mechanism remains unclear. In this study, we identified and characterized, both in vitro and clinically, an SCN5A mutation associated with familial progressive atrioventricular block of adult onset and dilated cardiomyopathy in a Chinese family. METHODS AND RESULTS: Among 32 family members, 5 were initially diagnosed with atrioventricular block after age 30; 4 were studied, 3 of whom later developed dilated cardiomyopathy. We found a heterozygous single-nucleotide mutation resulting in an amino acid substitution (A1180V) in all studied patients and in 6 other younger unaffected members but not in 200 control chromosomes. When expressed with the beta1 subunit, the mutated channels exhibited a -4.5-mV shift of inactivation with slower recovery leading to a rate-dependent Na(+) current reduction and a moderate increase in late Na(+) current. Clinical study revealed that although QRS duration decreased with increasing heart rate in noncarrier family members, this change was blunted in unaffected carriers whose ECG and heart function were normal. Resting corrected QT interval of unaffected carriers was significantly longer than that of noncarriers, even though it was still within the normal range. CONCLUSIONS: A1180V expresses a mild Na(+) channel phenotype in vitro and a corresponding clinical phenotype in unaffected mutation carriers, implying that A1180V caused structural heart disease in affected carriers by disturbing Na(+) influx and, hence, cellular Na(+) homeostasis. The high penetrance of A1180V suggests this phenotype as a high risk factor for dilated cardiomyopathy with preceding atrioventricular block.
Ge et al. (Wed,) conducted a observational in Atrioventricular block and dilated cardiomyopathy (n=32). SCN5A A1180V mutation vs. Noncarriers and control chromosomes was evaluated on In vitro Na+ channel properties and clinical ECG parameters (QRS duration, corrected QT interval). The SCN5A A1180V mutation exhibited a -4.5-mV shift of inactivation in vitro and was associated with longer resting corrected QT intervals in unaffected carriers compared to noncarriers.