Manipulating the QT interval of the ECG by cognitive effort

Abnormal prolongation of the QT interval of the ECG has been reported to indicate a hazard of sudden arrhythmic death. Therefore, with the aid of biofeedback from a newly devised instrument capable of measuring and recording the QT interval of the ECG in real time, ten healthy subjects, aided by biofeedback, attempted to shorten and also to lengthen QT. Although the changes achieved were relatively small, the ten subjects as a group were successful in both shortening and lengthening QT at the 0.01 level of significance. The degree of success varied, however, from person to person and from time to time in the same individual. If the findings reported here can be applied more generally to patients at risk for sudden death, and if biofeedback effects can be made to persist without reinforcement, it or other cognitive techniques may prove clinically useful for shortening QT.