Abnormal ventricular repolarization in long QT QT syndrome carriers is related to short left ventricular filling time and attenuated stroke volume response during exercise

摘要

Background Long QT syndrome ( LQTS ) carriers are characterized by abnormal ventricular repolarization, prolonged systole, and mechanical dispersion. Prolonged left ventricular ( LV ) systole has been shown to result in disproportionate shortening of LV filling in other conditions. The aim of this study was to assess LV filling, diastolic function, and stroke volume ( SV ) response to dynamic exercise, in a group of LQTS carriers. Methods Forty‐seven LQTS carriers (45?±?15?years, 20 symptomatic) and 35 healthy individuals underwent bicycle stress echocardiogram. Electrocardiographic and echocardiographic measurements were obtained at rest, peak exercise, and 4?minutes into recovery. Results Long QT syndrome carriers and controls did not differ in age, gender, heart rate, QRS duration, or LV ejection fraction. At rest, LQTS carriers had longer QT c and shorter filling time ( FT ). At peak exercise, QT c increased and remained longer than controls at recovery. A negative correlation was found between QT c and FT ( r ?=??.398, P ?=?.001) with greater fall in FT in LQTS carriers than in controls at peak exercise (?23%?±?10 vs +2%?±?3, P ??.0001). FT correlated with SV ( r? =?+.27, P? = ? .001), which increased more in controls than in LQTS carriers (+32%?±?4 vs +2%?±?1, P? ? .05). These differences were more pronounced in symptomatic LQTS carriers who had shorter FT and smaller SV at peak exercise and during recovery compared to asymptomatics ( P? ? .05). Conclusions Long QT syndrome carriers have longer QT c, but also shorter FT . These disturbances worsen at peak exercise (particularly in symptomatics) compromising LV filling and SV , hence a potential pathomechanism for adverse events.