Changes in QT Interval during Exercise Testing in Patients with VVI Pacemakers

. The changes in QT intervals were studied in nine patients with normal sinus node function who had VVI pacemakers. Though PP intervals uniformly shortened during exercise, the change in QaT* intervals during exercise was variable. The correlation between PP and QaT intervals varied from case to case. A good correlation was found in only two cases (r =+0.816 or +0.897); a fair correlation was found in four cases (r =+0.672, +0.615, +0.615, or −0.669) and in the remaining three, the correlation was poor (r =+0.494, +0.467 or−0.424). In patients who are candidates for VTI pacemaker implantation, changes in QaT intervals should be assessed during exercise stress testing to determine if the intervals shorten during exercise or not.
(QaT*: Interval from the pacing spike to the apex of T-wave.)