Control of rapid heart rate changes for electrocardiographic analysis: implications for thorough QT studies.
BACKGROUND
Following an abrupt change in heart rate (HR), QT adaptation is achieved within a delayed time frame.


OBJECTIVE
The exclusion of electrocardiograms (ECGs) showing rapid HR changes influences the level of a drug-induced QT prolongation.


METHODS
Continuous 12-lead ECG-Holter monitoring was performed in 31 healthy subjects. Using the "bin" method, we evaluated moxifloxacin effects on (1) QT interval duration at different RR intervals and (2) on the rate dependence of QT interval. These endpoints were calculated separately for five types of ECG analysis: classification of cardiac complexes based on (a) the single preceding RR interval (RR-1) and (b) RR filters excluding rapid HR changes according to the formula RR-1 = RR[time-window] +/- threshold, where the time-window could be 30 or 60 s (R30 and R60) and the threshold 15 or 30 ms (th15 or th30).


RESULTS
Moxifloxacin-induced QT prolongation was consistently higher using the stable models when compared with the RR-1 model. Moxifloxacin-induced QT prolongation at RR = 1000 ms was 8.2 +/- 11.2 vs. 10.9 +/- 10.4 ms using the RR-1 and R60th15 stable models, respectively (p < 0.05). Moxifloxacin-induced QT prolongation was more pronounced at slow than at fast HR. This so-called "reverse rate-dependent" effect was more pronounced when assessed using stable HR models (0.023 IC95% [0.019;0.027] vs. 0.015 IC95% [0.012;0.017] using the RR-1 model).


CONCLUSIONS
The exclusion of ECGs with rapid HR changes influences the magnitude of drug-induced QT changes. The hysteresis phenomenon should not be neglected when dedicated QT studies are performed.
Extramiana
Fabrice
F
Lariboisière University Hospital, Paris, France. fabrice.extramiana@lrb.ap-hop-paris.fr
Maison-Blanche
Pierre
P
Haggui
Abdeddayem
A
Badilini
Fabio
F
Beaufils
Philippe
P
Leenhardt
Antoine
A
D000293:Adolescent; D000328:Adult; D000890:Anti-Infective Agents / Q000494:pharmacology; D001372:Aza Compounds / Q000494:pharmacology; D015716:Electrocardiography, Ambulatory / Q000187:drug effects* / Q000379:methods; D005260:Female; D024841:Fluoroquinolones; D006329:Heart Conduction System / Q000187:drug effects*; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D000077266:Moxifloxacin; D011804:Quinolines / Q000494:pharmacology
D000890:Anti-Infective Agents; D001372:Aza Compounds; D024841:Fluoroquinolones; D011804:Quinolines; D000077266:Moxifloxacin