A misleading statement appeared in the News and Views article “Cardiology: Solace for the broken-hearted?” by Christine L. Mummery (Nature 433, 585–587; 2005). The cardiac arrhythmias reported in reference 9 (P. Menasche et al., J. Am. Coll. Cardiol. 41, 1078–1083; 2003) were not the cause of fatalities in patients who received their own skeletal-muscle progenitor cells as therapy for heart damage, as implied in the passage concerned.