One of the immediate consequences of apnea is a slight increase in acid levels inside oxygen-hungry muscle cells. When the researchers compared cells with the Y1103 mutation against normal cells in a slightly more acidic environment, the cells with the abnormal channels began to misbehave.
In normal cells, these sodium channels are closed at rest. In response to electrical signals they open briefly, allowing ions to flow though, then rapidly close again. When the pH falls, however, the mutant sodium ion channels tended to pop back open, delaying the cells' recovery after a burst of activity. In the heart, changes like this are known to increase the risk for abnormal rhythms and sudden death.
Fortunately, a drug called mexiletine, used to treat patients with arrhythmias, blocks late re-openings of sodium channels at low levels that do not interfere with normal function. Goldstein and colleagues found that the drug restored normal function in cells with two copies of the Y1103 channels even under acid conditions.
Although, the authors note, this study supports a role of Y1103 in SIDS, and the previous use of mexiletine by patients with arrhythmias "suggests a strategy for prophylactic therapy," they stress that their results "need to be replicated and the risks and benefits of treatment assessed" before screening programs are designed or drugs given to infants at risk to prevent SIDS.
Repetition of the findings would "lead us to consider genetic screening in African Americans in at least 3 situations," they add: "Infants with acute life-threatening events, siblings of SIDS victims, and couples that experience infertility or fetal demise."