Heart rhythm : the official journal of the Heart Rhythm Society
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Approximately 10% of sudden infant death syndrome (SIDS) cases may stem from potentially lethal cardiac channelopathies, with approximately half of channelopathic SIDS involving the Na(V)1.5 cardiac sodium channel. Recently, Na(V) beta subunits have been implicated in various cardiac arrhythmias. Thus, the 4 genes encoding Na(V) beta subunits represent plausible candidate genes for SIDS. ⋯ This study provides the first molecular and functional evidence to implicate the Na(V) beta subunits in SIDS pathogenesis. Altered Na(V)1.5 sodium channel function due to beta-subunit mutations may account for the molecular pathogenic mechanism underlying approximately 1% of SIDS cases.
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Genetic defects in the sodium channel or in the calcium channel have been identified in patients with Brugada syndrome (BS). However, the differences in their genotype-phenotype correlations are still unclear. ⋯ Although both sodium channel and calcium channel dysfunction produced similar BS ECGs and arrhythmogenesis at 60 bpm, calcium channel dysfunction was associated with a higher incidence of TWA at 60 bpm, less ST elevation, and fewer arrhythmias at 30 bpm compared with sodium channel dysfunction.
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Comparative Study
Causes of ventricular oversensing in implantable cardioverter-defibrillators: implications for diagnosis of lead fracture.
Implantable cardioverter-defibrillator (ICD) ventricular oversensing may result in inappropriate therapy, which may be triggered by lead/connection issues that require surgical revision or physiologic oversensing that may be resolved with reprogramming. The sensing integrity counter (SIC) is an oversensing diagnostic that increments for very rapid ventricular intervals < or =130 ms. ⋯ Oversensing resulting in frequent, very short intervals typically are caused by either lead/connection issues or physiologic signals. The additional finding of rapid NSTs usually indicates a lead/connection issue, even in the absence of impedance abnormalities.
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The presence of J waves on ECGs is related to idiopathic ventricular fibrillation (VF). ⋯ Idiopathic VF patients with J waves had a high incidence of LP showing circadian variation with night ascendancy. J waves may be more closely associated with depolarization abnormality and autonomic modulation than with repolarization abnormality.
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Ventricular tachyarrhythmia events (VTE) are common among refractory heart failure patients requiring ventricular assist device (VAD) support. It is unknown whether implantable cardioverter-defibrillator (ICD) detection and therapy can extend survival in the VAD population. ⋯ A concomitant ICD among VAD recipients is associated with extended survival.