The application of root mean square electrocardiography (RMS ECG) for the detection of acquired and congenital long QT syndrome.
BACKGROUND
Precise measurement of the QT interval is often hampered by difficulty determining the end of the low amplitude T wave. Root mean square electrocardiography (RMS ECG) provides a novel alternative measure of ventricular repolarization. Experimental data have shown that the interval between the RMS ECG QRS and T wave peaks (RTPK) closely reflects the mean ventricular action potential duration while the RMS T wave width (TW) tracks the dispersion of repolarization timing. Here, we tested the precision of RMS ECG to assess ventricular repolarization in humans in the setting of drug-induced and congenital Long QT Syndrome (LQTS).


METHODS
RMS ECG signals were derived from high-resolution 24 hour Holter monitor recordings from 68 subjects after receiving placebo and moxifloxacin and from standard 12 lead ECGs obtained in 97 subjects with LQTS and 97 age- and sex-matched controls. RTPK, QTRMS and RMS TW intervals were automatically measured using custom software and compared to traditional QT measures using lead II.


RESULTS
All measures of repolarization were prolonged during moxifloxacin administration and in LQTS subjects, but the variance of RMS intervals was significantly smaller than traditional lead II measurements. TW was prolonged during moxifloxacin and in subjects with LQT-2, but not LQT-1 or LQT-3.


CONCLUSIONS
These data validate the application of RMS ECG for the detection of drug-induced and congenital LQTS. RMS ECG measurements are more precise than the current standard of care lead II measurements.
Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, Utah, United States of America.
Robert L
RL
Lux
Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, Utah, United States of America.
Christopher Todd
CT
Sower
Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, Utah, United States of America.
Nancy
N
Allen
The Division of Pediatric Cardiology, University of Utah, Salt Lake City, Utah, United States of America.
Susan P
SP
Etheridge
Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, Utah, United States of America ; The Division of Pediatric Cardiology, University of Utah, Salt Lake City, Utah, United States of America.
Martin
M
Tristani-Firouzi
The Division of Pediatric Cardiology, University of Utah, Salt Lake City, Utah, United States of America.
Elizabeth V
EV
Saarel
D000293:Adolescent; D000328:Adult; D002316:Cardiotonic Agents / Q000627:therapeutic use; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D003627:Data Interpretation, Statistical; D015716:Electrocardiography, Ambulatory / Q000379:methods*; D005260:Female; D024841:Fluoroquinolones / Q000627:therapeutic use; D006339:Heart Rate; D006801:Humans; D008133:Long QT Syndrome / Q000175:diagnosis* / Q000188:drug therapy / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D000077266:Moxifloxacin; D016032:Randomized Controlled Trials as Topic; D055815:Young Adult
D002316:Cardiotonic Agents; D024841:Fluoroquinolones; D000077266:Moxifloxacin