Implantable Defibrillator Most Effective in Patients With Low Ejection
Fractions

	October 5, 1999 - The improved survival associated with ICDs may be
limited to patients with EFs (ejection fractions) below 35%, according to 2
reports in the October Journal of the American College of Cardiology.
	Dr. Michael Domanski of the NHLBI and associates from the AVID
(Antiarrhythmics Versus Implantable Defibrillators) study checked survival
differences in patients treated with ICD or antiarrhythmic drugs according to
EF.
	Survival in patients with an EF of at least 35% did not differ
between the ICD and drug groups. For patients whose EF was between 20 and 34
however, one and two year survival was better with ICD (89% vs. 80%) than
with drug therapy. Patients whose EF fell below 20% had a one to two year
survival advantage when treated with ICD (82% vs 73%), compared with drug
therapy.
	"This suggests that patients with EF greater than 35% may not have
better survival with an ICD compared to taking antiarrhythmic drugs," the
authors conclude. "At lower EF, the ICD appears to offer improved survival
compared to drug therapy."
	A related study was done by Dr. Suneet Mittal. He studied the survival
of CAD patients with unexplained fainting who were treated with ICD after EPS
showed inducible monomorphic ventricular tachycardia. "The main findings of
this study," the authors say, "are that in patients with coronary artery
disease and unexplained fainting, testing suggests a probable arrhythmogenic
cause in about 50% of patients."
	They note that ethical issues prevented withholding ICD treatment
from patients, so the amount of benefit from ICDs could not be determined
from this study. Nevertheless, they write, "the results of this study suggest
that, despite frequent appropriate ICD therapy, patients with inducible
ventricular tachycardia are at high risk for cardiac and total mortality,
with a 2 year survival rate less than 50%."
	"No valid conclusions can be drawn about the potential mortality
benefit of ICDs in either patient subgroup," doctors write in a related
commentary. "Few would argue against ICD therapy for such patients on the
basis of reasonable clinical judgment, even without proof of effectiveness.
The observations in both reports," the commentary concludes, "confirm the
notion that existing published trials on ICD therapy are difficult to
generalize.

J Am Coll Cardiol 1999;34:1082-1089,1090-1098