PARADOXICALLY SHORTENED QT INTERVAL AFTER A PROLONGED PAUSE

We analyzed Holter ECG recordings in 15 patients with episodes of prol onged RR intervals > 2.5 seconds. In 13 patients, the QT interval shel ved a linear prolongation when RR interval was < 1.5 seconds and becam e relatively flat at longer RR intervals. In the remaining two patient s, the QT and RR intervals were correlated within physiological range of RR intervals. However, at longer RR intervals, the QT interval was unexpectedly shortened and constant. The paradoxically shortened QT in terval observed in the present 2 cases may indicate an abnormal adapta tion of repolarization time to an abrupt increase in the preceding RR intervals.