Abstract

Background and objective QT interval correction for heart rate (QTc) is essential for clinical usage. A new QTc formula has been developed based on a data agnostic mathematical approach in a large population ECG data base. The formula requires testing on a within individual basis under conditions of intervention to increase heart rate. The objective of this study was to examine the stability and reliability the new QTc formulae within individuals when Heart Rate (HR) is increased by dobutamine. Methods HR and QT interval were measured in fifteen individuals who received intravenous dobutamine in a sequential protocol at 5, 10, 20, 30 and 40 micrograms/kg/min. Results Dobutamine produced a significant (p < 0.0001) increase in heart rate and a significant (p < 0.0001) reduction in QT. The new QTc formula showed relative stability with little change across the dobutamine dosages. Using a linear regression to evaluate the HR-QT interval, showed a significant (p < 0.0001) negative slope for the relationship. In contrast, the slope of the QTc-heart rate relationship for the new QTc formula did not differ from zero. Conclusion The new QT correction formula is relatively independent of the effect of increasing heart rate and should be useful QTc formula especially in conditions of increased heart rate.

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