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Portland, OR - Left-ventricular systolic function was at least moderately reduced
in only about half of those who experienced sudden cardiac death (SCD) over
two years in a US community-based study [1].
Less than one third had severely reduced LVEF, by far the most common
indication for a prophylactic implantable cardioverter defibrillator (ICD).
None of the study patients were being protected by such a device. "These findings . . . confirm the need to
identify SCD risk predictors other than severe LV dysfunction in the general
population," write Dr Eric C Stecker (Oregon Health and Science
University, Portland) and colleagues in a report published online February
23, 2006 in the Journal of the American College of Cardiology and
scheduled for the journal's March 21, 2006 issue. In the group's analysis of SCD patients enrolled in the ongoing Oregon
Sudden Unexpected Death Study who had evaluable pre-SCD LV systolic
functional data, features associated with SCD in the setting of normal LVEF
included younger age, female sex, and presence of a seizure disorder.
The Oregon study "provides population-based data that
unfortunately show that only a small proportion of sudden-death victims could
have benefited from the current primary-prevention ICD guidelines,"
observes Dr William J Groh (Krannert Institute of Cardiology, Indiana
University, Indianapolis) [2]. In an accompanying editorial, he writes
that in the absence of proven SCD risk predictors for persons without known
LV dysfunction, "there are population-based approaches that can be
applied to prevent sudden death." Groh notes that the rate of
CAD-related SCD has apparently declined along with rates of "non-sudden
coronary death" as ischemic heart disease therapy has improved. "Early identification of coronary risk factors and primary- and
secondary-prevention measures should continue to decrease the population
vulnerable to sudden death," Groh writes. "As well, communities
need to optimize their emergency response to the cardiac-arrest victim,
thereby increasing the likelihood of survivability of the arrhythmias
associated with sudden death." In the Oregon study, 121 of the 714 persons stricken with SCD had
undergone prior LV systolic functional assessment. The subgroup appeared to
differ from the larger group only by being slightly older, according to the
authors. About 30% of the subjects with LV systolic data had a severely
depressed LVEF, defined as <35%. However, the group writes,
"Even if all of the other risk predictors, such as history of
resuscitated cardiac arrest, long-QT or Brugada syndromes, hypertrophic
cardiomyopathy, and arrhythmogenic right-ventricular dysplasia, were taken
into account, only 35% of SCD cases would have been identified as being at
high risk for SCD." After searching for possible indicators of elevated SCD risk in the
setting of normal LV systolic function, the investigators found several
candidates. Of note, a history of seizure disorder was observed only among
patients with a normal LVEF. Characteristics of SCD cases that underwent
evaluation of LV function
*Highest LVEF group vs either other group. SCD=sudden cardiac death To download table as a slide, click on slide logo below In his editorial, Groh described limitations of the study that may
suggest reduced LVEF is even rarer among SCD victims than was estimated. It's
not evident how many persons in the community were protected from SCD by
ICDs. Moreover, Groh writes, "One would expect that patients having an
indication that prompted a structural cardiac assessment would be more likely
to have significant left ventricular dysfunction than those without such an
indication." Thus, he concludes, it is likely that a lower proportion of
the 593 persons without such an assessment would have an LVEF low enough to
qualify for a primary-prevention ICD.
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