Researchers find link between familial and new-onset AF
Lubitz S. JAMA. 2010;doi:10.1001/jama.2010.1690.
New-onset atrial fibrillation was found to be most common among those with familial atrial fibrillation when compared with those without familial atrial fibrillation, an association not attenuated by adjustment for atrial fibrillation risk factors, according to study data.
“We report an association between the occurrence of AF in a first-degree relative and risk of new-onset AF in 4,421 individuals of European descent,” the researchers commented in their study, adding that the findings support and extend previous reports of AF heritability.
The study included participants from the Framingham Heart Study who were at least 30 years of age, free of AF at baseline examination and had at least one parent or sibling enrolled in the study. Researchers followed up with the final study group (n=4,421; mean age, 54 years; 54% women) through 2007.
After 11,971 examinations, researchers reported familial AF in 1,185 participants (26.8%), with premature familial AF occurring in 351 cases (7.9%). Those with familial AF had a more common occurrence of AF than those without (5.8% vs. 3.1%), which was not attenuated, even after adjustment for AF risk factors (multivariable-adjusted HR=1.40; 95% CI, 1.13-1.74) or reported AF-related genetic variants.
Further data indicated that among the different features of familial AF examined, premature familial AF was associated with the greatest improved discrimination beyond traditional risk factors (P=.004).
As recommendations for additional research, the study investigators wrote, “Future efforts should attempt to discern the factors that mediate the association between familial AF and AF risk, further explore the relationships between premature familial AF and risk prediction, and determine whether incorporating genetic variants into an AF prediction model enhances its performance.”
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AEDs did not improve survival among hospitalized patients with cardiac arrest
Chan P. JAMA. 2010;304:2129-2136.
Patients hospitalized for cardiac arrest experienced no improvement in survival with the use of automated external defibrillators and, in some cases, had lower rates of survival when compared with those who were not treated with the device.
The study, published in the Journal of the American Medical Association, featured 11,695 patients, 9,616 (82.2%) with non-shockable rhythms such as asystole and pulseless electrical activity, and 2,079 (17.8%) with shockable rhythms, including ventricular fibrillation and pulseless ventricular tachycardia.
Of the study population, AEDs were used in 4,515 patients (38.6%), with 2,117 (18.1%) surviving to hospital discharge. Researchers reported AED use was significantly associated with a lower rate of survival after in-hospital cardiac arrest vs. no AED use (16.3% vs. 19.3%; adjusted rate ratio=0.85; 95% CI, 0.78-0.92).
Further, AED use among cardiac arrests due to non-shockable rhythms was associated with lower survival (10.4% vs. 15.4%; adjusted rate ratio=0.74; 95% CI, 0.65-0.83), whereas AED use for cardiac arrests due to shockable rhythms was not associated with survival (38.4% vs. 39.8%; adjusted rate ratio=1.00; 95% CI, 0.88-1.13).
“We found that use of AEDs among hospitalized patients with cardiac arrests was not associated with improved survival,” the researchers wrote. “While randomized controlled trials are needed to confirm these findings, current use of AEDs in hospitalized patients may warrant reconsideration.”
This is an interesting study that shows how a seemingly good idea can have unexpected negative consequences. In the in-hospital setting, delay to defibrillation is not, or should not be, nearly as great a problem as it is in the out-of-hospital setting. Out-of-hospital, highly trained rescuers must be called to the scene from a distance. The AED greatly increases the pool of potential rescuers and that's why they are effective in that setting. In-hospital, trained rescuers should be readily available. The time advantage gained by having an AED available is probably measured in seconds not minutes. Therefore, the gain that's accrued in ventricular tachycardia/ventricular fibrillation cases is small. In contrast, the potential for delays or interruptions in providing recommended therapy for pulseless electrical activity cases or other types of bradyasystolic arrests seems to have deleterious effects and negates any chance for overall benefit.