Ejection Fraction May Improve But the Scar Still Exists! The Risk May Be Lower But Not Zero
We read with great interest the report by Kini et al. (1). The results are interesting, and the authors make a strong case against the clinical utility and cost-effectiveness of continued generator replacements in patients with implantable cardioverter-defibrillators who have improved ejection fraction (EF). We disagree with the conclusions of the authors and find it rather bold to arrive at such sweeping recommendations based on limited data. In this study, 8% (n = 5) of the 59 patients received appropriate therapy despite improvement in EF over a mean of 3.5 years, for an event rate of 2.8% per person-year or 1.4% per year (n = 5/3.5 years). This rate is much higher than the 0.1% risk of sudden cardiac death in the general population (2). If the general population is considered a control group, then the absolute risk reduction is 1.3% with a number needed to treat of 76. With that number needed to treat, we find it hard to explain the recommendation that a potentially lifesaving therapy should be withheld. Again, if we consider all patients who had an improvement in EF to >35%, we would include the 8 patients who had an event before generator replacement despite an EF >35%, which would increase the event rate to 20% (n = 13 of 67) or 3.7% per year. This reduces the number needed to treat even further. Although EF, which is the surrogate marker for the risk of sudden cardiac death, may improve over time, the scar that is the substrate for reentry is unlikely to resolve, especially in patients with ischemic cardiomyopathy (3). The cost-effective analysis used in the current paper is not robust either. Thus, until larger studies are reported that can effectively predict those who are at risk for sudden cardiac death despite improvement in EF, we should continue to replace generators after a thorough discussion with the individual patient respecting his or her preferences.
1. : "Appropriateness of primary prevention implantable cardioverter-defibrillators at the time of generator replacement: are indications still met?". J Am Coll Cardiol 2014; 63: 2388.
Cardiac arrest and sudden death. In: Heart disease: a textbook of cardiovascular medicine . Edited by . Philadelphia: WB Saunders1997: 742.
3. : "Assessment of myocardial scarring improves risk stratification in patients evaluated for cardiac defibrillator implantation". J Am Coll Cardiol 2012; 60: 408.