However, Bazett’s correction has a strong residual correlation with heart rate. Finally, within-person variability and measurement error are additional sources of variability in the QT interval length.īazett’s correction is still recommended for the diagnosis of congenital long and short QT syndrome ( 8, 9). Other factors associated with QT interval length variability include age, sex, hypertension, body mass index, medication usage, low-calorie diets, serum potassium levels, and common genetic variants ( 7). Marked prolongations in the QT interval may be caused by genetic disorders (e.g., long QT syndrome), pharmacological agents (e.g., antiarrhythmics, antipsychotics, and antibiotics), electrolyte abnormalities (e.g., hypokalemia and hypomagnese-mia), and their interactions ( 7). Normal values for the QTc range from 350 to 450 ms for adult men and from 360 to 460 ms for adult women however, 10%-20% of otherwise healthy persons may have QTc values outside this range. The electrocardiographic QTc is approximately normally distributed in the general population. Bazett’s formula is the most commonly used method to calculate QTc and adjusts for the heart rate, although it tends to underestimate the duration of repolarization when the heart rate is particularly slow (or overestimate when the heart rate is fast). Frequently, reference ranges for the QT-interval in the general population are expressed in terms of QTc, a corrected form of the QT interval ( 3- 6).
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |