Clinical presentation, genetic etiology and outcome associated with fetal cardiomyopathy: comparison of two eras.

OBJECTIVE: To assess the rate and type of genetic diagnosis and clinical outcome of cases of fetal cardiomyopathy (CM) during two eras, in order to examine the impact of advanced genetic testing and improved perinatal management strategies. METHODS: All diagnoses of fetal CM in Alberta, Canada, encountered between 2003 and 2019, were reviewed retrospectively. Genetic, cardiac and non-cardiac diagnoses and clinical outcome were documented. Cases with CM secondary to extracardiac pathology and maternal conditions were excluded. Cases diagnosed in the earlier era of the study period (2003-2012) were compared with those diagnosed in the later era (2013-2019). RESULTS: Thirty-eight cases of fetal CM met the inclusion criteria. Median gestational age (GA) at diagnosis was 22.8 (range, 13.4-37.4) weeks. Associated structural heart disease was present in 39% (15/38) of cases and 24% (9/38) had arrhythmia. Hydrops was identified in 29% (11/38) of cases at presentation, and a further 18% (7/38) developed hydrops later in gestation. Twenty-six percent (10/38) of cases underwent termination of pregnancy and 24% (9/38) had intrauterine death. Of liveborn cases, neonatal death occurred in 16% (3/19), late death occurred in 21% (4/19) and 63% (12/19) were alive at the last follow-up. Excluding cases that had termination of pregnancy and those with a liveborn infant who received planned palliative care, the rate of neonatal survival was higher in the later compared with the earlier era (69% (11/16) vs 45% (5/11)), although the difference was not statistically significant (P = 0.26). A genetic etiology was confirmed in 39% (15/38) of cases and strongly suspected in 24% (9/38). A significantly higher proportion of cases had a confirmed or strongly suspected genetic etiology in the later era compared with in the earlier era (76% (19/25) vs 38% (5/13); P = 0.04). CONCLUSIONS: In the recent era, a higher proportion of fetal CM cases had a confirmed or strongly suspected genetic etiology than reported previously. Based on comparison with older series, modern perinatal management strategies may not have a significant impact on neonatal survival in cases of fetal CM; however, a larger study would be better powered to detect more subtle differences. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

Physiology and Pathophysiology of Sodium Channel Inactivation.

Voltage-gated sodium channels are present in different tissues within the human body, predominantly nerve, muscle, and heart. The sodium channel is composed of four similar domains, each containing six transmembrane segments. Each domain can be functionally organized into a voltage-sensing region and a pore region. The sodium channel may exist in resting, activated, fast inactivated, or slow inactivated states. Upon depolarization, when the channel opens, the fast inactivation gate is in its open state. Within the time frame of milliseconds, this gate closes and blocks the channel pore from conducting any more sodium ions. Repetitive or continuous stimulations of sodium channels result in a rate-dependent decrease of sodium current. This process may continue until the channel fully shuts down. This collapse is known as slow inactivation. This chapter reviews what is known to date regarding, sodium channel inactivation with a focus on various mutations within each NaV subtype and with clinical implications.