Ne. Mezilis et al., QT VARIABILITY BEFORE AND AFTER EPISODES OF NONSUSTAINED VENTRICULAR-TACHYCARDIA IN PATIENTS WITH HYPERTROPHIC CARDIOMYOPATHY, PACE, 21(11), 1998, pp. 2387-2391
This study examined the changes in QT dynamics occurring during 5-minu
te intervals sampled immediately before and 1 hour after episodes of n
onsustained ventricular tachycardia (VT) in patients with hypertrophic
cardiomyopathy (HCM). Twenty-four hour Holter recordings were perform
ed in 10 patients with HCM in the absence of antiarrhythmic medication
s and processed by the ELA Medical QT analysis software. All sinus com
plexes were averaged over 30-second segments and 2,880 templates were
created. For each template, a mean corrected QT(ec) (time interval bet
ween the onset of QRS and the end of the T wave) and QT(ac) (time inte
rval between the onset of the QRS and the peak of the T wave) were cal
culated, with their standard deviations (SDQT(e) and SDQT(a)) taken as
indices of QT variability. The slopes of the regression line for the
QT(e) and QT(a) against the corresponding RR also were calculated. For
ty 5-minute segments were analyzed immediately before (sample A) and 1
hour after (sample B) 20 episodes of nonsustained VT. QT(ac) was sign
ificantly longer in group A than in group B (321 +/- 20 vs 312 +/- 22,
P < 0.0001) and SDQT(a) was significantly lower (2.8 +/- 1.2 vs 4.7 /- 3.7 P < 0.03). There were no significant differences in QT(ec), SDQ
T(e), QT(e)/RR and QT(a)/RR before and after the episodes. Our data in
dicate that in patients with HCM, the averaged QT,, is significantly l
onger and the QT(a) variability significantly lower before episodes of
nonsustained VT.