Scientists at Johns Hopkins University are creating virtual replicas of patients’ hearts so they can test how to fix a life-threatening irregular heartbeat before treating the real organ. Doctors try to block ventricular tachycardia by burning off misfiring heart tissue but it’s difficult to pinpoint the right spots and those ablations often must be repeated. Hopkins researchers used custom, interactive “digital twins” of 10 patients’ hearts to predict where best to aim and over a year later those patients were faring well. The findings were published in the New England Journal of Medicine Wednesday. Larger studies of this technology are needed.