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The prognostic accuracy of different QT interval measures
Kaspar Lund1, Juha S Perkiömäki, Christian Brohet
1Department of Cardiology, Skejby University Hospital, DK-8200 Aarhus N, Denmark. KasparLund@bigfoot.com
Insights
The longest QT interval offers the highest accuracy in predicting arrhythmic death. Using the mean of the three longest QT intervals is recommended for consistent prognostic accuracy in electrocardiogram studies.
Area of Science:
- Cardiology
- Electrocardiography
- Predictive Analytics
Background:
- QT interval measurement accuracy for predicting arrhythmic death varies.
- Lead selection methods may explain discrepancies in study results.
Purpose of the Study:
- To analyze the prognostic accuracy of all known lead selection methods for QT interval measurement.
- To determine the optimal method for QT interval measurement to predict adverse cardiovascular outcomes.
Main Methods:
- Utilized QT databases from three institutions with over 3500 twelve-lead surface ECGs.
- Included diverse patient populations: normal, acute myocardial infarction, and remote myocardial infarction.
- Defined prognostic accuracy using the area under the Receiver Operator Curve (ROC-area).
Main Results:
- Lead I and aVL showed the highest accuracy among standard leads; AVR was least accurate.
- Precordial lead V4 demonstrated high prognostic accuracy.
- The longest QT interval measurement was more accurate than any standard lead selection.
Conclusions:
- The longest QT interval provides the highest prognostic accuracy for predicting arrhythmic death.
- Significant differences in lead selection accuracy can explain variability in literature.
- Recommends using the mean of the three longest QT intervals for improved prognostic accuracy.
Background:
The QT intervals accuracy for predicting arrhythmic death varies between studies, possibly due to differences in the selection of the lead used for measurement of the QT interval. The purpose of this study was to analyze the prognostic accuracy of all known ways to select the lead.
Methods And Results:
Three institutions that used different methods for measuring QT intervals provided their QT databases. They included more than 3500 twelve-lead surface ECGs. The data represented low- and high-risk patients of the normal population (survivors vs dead from cardiovascular causes), acute myocardial infarction (survivors versus death from all causes) and remote myocardial infarction (with vs without a history of ventricular arrhythmia). The prognostic accuracy was defined as the area under the Receiver Operator Curve (ROC-area). The most accurate standard leads were I and aVL and the least accurate was AVR. The most accurate precordial lead was V4. The prognostic accuracy of the longest QT interval was higher than for any standard lead. The prognostic accuracy of the mean of the three longest QT intervals was equal to or slightly lower than for the longest QT interval.
Conclusions:
The highest prognostic accuracy is obtained with the longest QT interval. The accuracies of the lead selection methods are so different that it can explain a substantial part of the differences between otherwise similar studies in the literature. We recommend the use of the mean value of the three longest QT intervals.