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A928
October 19, 2009
2:00 PM - 4:00 PM
Room Area M
Comparison of Automatic Versus Manual Perioperative QT Measurement
  **   Diana Anton, M.D., Hannes Pfizenmayer, M.D., Patrick Friederich, M.D.
Department of Anesthesiology, Bogenhausen Hospital, Munich, Germany
Introduction:

Patients suffering from the Long QT Syndrome are exposed to a high risk of experiencing torsade de pointes ventricular arrhythmia and sudden cardiac death. Ventricular arrhythmia may be triggered by adrenergic stimulation caused by emotional or physical stress such as that occurring during the induction of anesthesia. Furthermore, anesthetic agents by prolonging the QT interval are also capable of inducing ventricular arrhythmia (1, 2). Despite being frequently indicated (2) perioperative monitoring of the QT interval has so far not been established. The aim of this study, therefore, was to determine, if automatic perioperative determination of QT intervals is possible and reliable. It was, furthermore, intended to evaluate how automatically determined QT values compare to those measured manually.

Methods:

Electrocardiograms (ECGs) from 52 patients undergoing surgery were analyzed. Serial recordings were printed on paper during the pre-, intra-, and postoperative period. ECGs were determined separately in three leads by five anesthesiologists previously trained in QT analysis. Manually determined QT intervals were compared to QT values obtained automatically using the 12sl algorithm (GE, Milwaukee, Wisconsin, USA). The manually determined QT values were corrected for heart rate according to the method described by Charbit et al. (3). Automatically determined QTc values were corrected for heart rate with the Bazett formula implemented in the 12sl algorithm. For statistical analysis Kruskal-Wallis, Fleiss´ kappa statistics and nonparametric tests were used. Data are presented as mean ± SD.

Results:

278 electrocardiograms were analyzed. The average age of the patients was 55 ± 16 years. The mean Body-mass-index was 27 ± 4 kg/m 2 , heart rate was 67 ± 12 beats/min. Manually determined QT values varied from 388 ± 41 ms to 446 ± 57 ms. Interobserver agreement on QT intervals was low (kappa = 0,097). The manually determined mean QT value (424 ± 45 ms) was significantly different from the automatically determined mean QT value (418 ± 41 ms, p ≤ 0,001). After correction for heart rate interobserver agreement on QTc intervals was again low (kappa = 0,053). The manually determined mean QTc value did, however, not significantly differ from the automatically determined mean QTc value (438 ± 31 ms vs. 438 ± 25 ms, p ≥ 0,05).

Discussion:

To the best of our knowledge this study demonstrates the feasibility of automatically determined perioperative QT intervals for the first time. Automatic QT measurements show several advantages over manual analysis of QT intervals. Automatic QT measurement is less time consuming, it is available online and it is not prone to reader variability. Our data clearly demonstrate that monitoring of QT intervals during the entire course of perioperative treatment is possible. Our data, furthermore, suggest that automatic QTc monitoring should be favoured over manual QTc monitoring in the perioperative management of patients suffering from the Long QT Syndrome.

References:

1 Charbit B, Alvarez JC, Dasque E et al. Anesthesiology 2008; 109: 206-12

2 Kies S, Pabelick C, Hurley H. et al. Anesthesiology 2005; 102: 204-10

3 Charbit B, Samain E, Merckx P, Funck-Brentano C. Anesthesiology 2006; 104: 255-60.

From Proceedings of the 2009 Annual Meeting of the American Society Anesthesiologists.