Objective To compare four heart rate correction formulas for calculation of

Objective To compare four heart rate correction formulas for calculation of the rate corrected QT interval (QTc) among infants and young children. of the QTc-RR regression lines for the four correction formulas were: ?0.019 (Bazett); 0.1028 (Fridericia); ?0.1241 (Hodges); and 0.2748 (Framingham). With the Bazett method a QTc >460 ms was 2 standard deviations above the imply compared with “long term” QTc ideals of BMS-345541 414 443 and 353 ms for the Fridericia Hodges BMS-345541 and Framingham formulas respectively. Conclusions The Bazett method calculated probably the most consistent QTc; 460 msec is the best threshold for long term QTc. The study supports continued use of the Bazett method for babies and children and differs from the use of the Fridericia correction during clinical tests of new medications. < 0.001]. Numbers 2 demonstrates the QTc-RR interval scatter plots and regression lines based on the Bazett Fridericia Hodges and Framingham formulas. The Bazett method offered a regression collection having a slope closest to zero (?0.019) indicating the best consistency across heart rates. The slopes of the QTc-RR regression lines for the additional correction formulas were Fridericia (+0.1028); Hodges (?0.1241); and Framingham (+0.2748). The Bazett method was also probably the most consistent for the variables of sex and age (Table IV; available at www.jpeds.com). The Fridericia method was second best in five of seven sub-groups becoming surpassed from the Hodges method for HR <130 BMS-345541 and among males. Number 1 Uncorrected QT-RR Scatter Storyline of all subjects. Number 2 QTc-RR Scatter Storyline of all subjects: (a) Bazett (b) Fridericia (c) Hodges (d) Framingham formulas. A linear regression slope closer to zero shows better QT correction across different heart rates (RR intervals). The Bazett and Fridericia methods calculate the corrected QT intervals through different ideals of an exponent (e) in the correction method (QTc = QT/RRe where e = 0.5 for the Bazett KLF4 correction and 0.33 for Fridericia). Consequently we computed slopes of QTc-RR regression lines for different ideals of e (from 0.3 to 0.6). An e value of 0.48 resulted in a regression collection having a slope equal to zero (Figure 3; available at www.jpeds.com). Results of these slope calculations further support the conclusion the Bazett method provides the very best regularity in QTc ideals across heart rates seen in babies and children. Number 3 Correlation coefficient between QTc and RR with numerous correction element exponents. The correction element exponent e in the method QTc = QT/RRis diverse across the ideals of 0.3 – 0.6. Number 4 depicts two super-imposed curves of distribution comparing the QTc ideals computed with data from our subjects from the Bazett and Fridericia formulas respectively. As can be seen from this graph using a threshold of 460 ms as definition for “long term QT” (>2SD above the mean) calculation of the QTc based on the Fridericia method will lead to an increased quantity of false negatives. Similarly using an absolute threshold of 414 ms while calculating QTc based on the Bazett method will lead to an increased quantity of false positives. Thus the definition of BMS-345541 “potentially prolonged QT” is dependent within the method used and needs to be clearly stated. Number 4 Two superimposed distribution curves comparing the QTc ideals computed from the Bazett vs Fridericia formulas. The X-axis denotes QTc ideals in msec. The vertical collection represents the mean for each method and the shaded area under the curve represents … Conversation Several formulas have been proposed for heart rate corrections of QT intervals each with limitations. For example the Bazett method has been reported to over-correct the QT interval at faster heart rates and under-correct at slower rates (12 15 18 27 Conversely the Fridericia method has been shown to do the opposite — under-correct at faster and over-correct at slower rates (12 13 15 Our data are consistent with these limitations as indicated by negative and positive ideals of the slopes of regression lines for the Bazett and Fridericia QTc-RR plots respectively. However almost all of these studies are limited to adolescents or adults in resting claims with an top limit of heart rates of 100 bpm (12 15 18 27 29 Furthermore use of the terms and in the absence BMS-345541 of an.