Effect of QT Interval Correction during Autonomic Blockade in Combination with Changes in Posture

MARIANO LLAMEDO SORIA; PEDRO ARINI; MARCELO RISK; PABLO LAGUNA

COMPUTERS IN CARDIOLOGY

IEEE

Año: 2005 vol. 32 p. 519 - 522

0276-6574

The measurement of QT interval on ECG is a marker for malignant ventricular arrhythmias. When QT is mea- sured, it must be corrected to become independent of heart rate (HR) and become a comparable measure of repo- larization between different conditions. The objective of this work was to evaluate different types of QT interval correction (Bazzett, Individual and Hodges) for different QT/RR relations. This was accomplished with selective blockade of sympathetic and vagal autonomic systems by using combinations of postural changes and drugs. When comparing vagal condition (supine) versus sympathetic condition (standing atropine) a significant shortening of 43 ms (P < 0.006) was observed. Whereas when comparing sympathetic (standing) versus vagal condition (supine pro- pranolol) a significant lengthening of 23 ms (P < 0.005) was observed. The Individual correction method achieved the best uncorrelation between QT and RR interval, mak- ing QT more independent of HR and ANS status.