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(Circulation. 1997;96:3006-3012.)
© 1997 American Heart Association, Inc.

Articles

Evaluation of the Spatial Aspects of T-Wave Complexity in the Long-QT Syndrome

Silvia G. Priori, MD, PhD; David W. Mortara, PhD; Carlo Napolitano, MD; Livia Diehl, MD; Vincenzo Paganini, MD; Francesco Cantù, MD; Giacomo Cantù, PhD; ; Peter J. Schwartz, MD

From Molecular Cardiology and Electrophysiology, Fondazione "Salvatore Maugeri," Pavia, Italy (S.G.P.); Centro di Fisiologia Clinica e Ipertensione, Ospedale Maggiore IRCCS, Università di Milano, Italy (C.N., L.D., V.P., F.C., P.J.S.); Dipartimento di Cardiologia, Ospedale Policlinico S. Matteo IRCCS, Università di Pavia, Italy (S.G.P., V.P., F.C., P.J.S.); Mortara Instrument, Milwaukee, Wis (D.W.M.); and Centro Studi Nucleari Enrico Fermi, Politecnico di Milano, Italy (G.C.).

Background The duration of the QT interval is only a gross estimate of repolarization. Besides its limited accuracy and reproducibility, it does not provide information on the morphology of the T wave; thus, morphologic alterations such as notches can be only qualitatively described but not objectively quantified.

Methods and Results To measure the complexity of repolarization in the long-QT syndrome (LQTS) patients, we previously applied principal component analysis to body surface mapping and found it useful in distinguishing normal from abnormal repolarization patterns (sensitivity, 87%). In the present study, we applied principal component analysis to 12-lead Holter recordings. The index of complexity of repolarization that we have developed (CR_24h) reflects the average 24-hour complexity of repolarization and is mathematically defined as the average ratio between the second and the first eigenvalue. We studied 36 LQTS patients and 40 control subjects. A mean of 22±1.3 ECG recordings at 1-hour intervals was used in each patient, and a total of 1655 recordings were analyzed. CR_24h was significantly higher in LQTS than in control subjects (34±12% versus 13±3%; P<.0001). A CR_24h exceeding 2 SD above the mean of the control group (>20%) was present in 32 of 36 patients (88%). The negative predictive value of CR_24h in LQTS was 88%, and the combination of prolonged QT and abnormal CR_24h identified all LQTS patients from normal subjects, including 4 affected symptomatic individuals with a normal QT interval duration, suggesting that CR_24h provides information independent of QT duration.

Conclusions Our data suggest that principal component analysis applied to 24-hour, 12-lead Holter recording adequately quantifies the complexity of ventricular repolarization and may become a useful noninvasive diagnostic tool in LQTS.

Key Words: electrocardiography • torsade de pointes • death, sudden

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