Individual-Specific QT Interval Correction for Drugs With Substantial Heart Rate Effect Using Holter ECGs Extracted Over a Wide Range of Heart Rates

2018 ◽  
Vol 58 (8) ◽  
pp. 1013-1019 ◽  
Author(s):  
Gopi Krishna Panicker ◽  
Pramod Kadam ◽  
Saikat Chakraborty ◽  
Snehal Kothari ◽  
J. Rick Turner ◽  
...  
Keyword(s):  
Heart Rate ◽  
Qt Interval ◽  
Rate Effect ◽  
Heart Rates ◽  
Wide Range ◽  
Heart Rate Effect

Beat-by-beat modulation of AV conduction. I. Heart rate and respiratory influences

1986 ◽  
Vol 251 (6) ◽  
pp. H1126-H1133 ◽  
Author(s):  
M. R. Warner ◽  
J. M. Loeb
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Oscillatory Activity ◽  
Conduction Time ◽  
Atrial Pacing ◽  
Sinus Arrhythmia ◽  
Heart Rates ◽  
Av Conduction ◽  
Wide Range ◽  
Cyclic Changes

We examined the integration of heart rate and neural influences at the atrioventricular (AV) node in conscious dogs. Animals were anesthetized and, under sterile conditions, instrumented to chronically record atrial and ventricular electrograms and blood pressure. In the conscious state, electrocardiogram (ECG), respiration, blood pressure, and electrograms were recorded on a beat-by-beat basis, and heart rate and AV interval were plotted graphically as a function of time. Resting animals exhibited both respiratory sinus arrhythmia and marked oscillations in AV conduction time associated with respiration. During inspiration AV interval was shortened, and during expiration AV interval was prolonged. To obviate the effect of cyclic changes in heart rate, atrial pacing was used to increase heart rate over a wide range both abruptly and linearly. Regardless of the pattern of heart rate change, AV interval oscillated at the respiratory frequency at pacing rates 10-100 beats/min above control. Higher levels of atrial pacing resulted in AV conduction patterns that were correlated with changes in blood pressure. Thus in the conscious dog variations in AV conduction time occur on a beat-by-beat basis in conjunction with respiration; oscillatory activity of AV conduction is not dependent on simultaneous changes in heart rate; and during atrial pacing, autonomic neural activity associated with respiration and blood pressure appears to dynamically modulate AV conduction with respiratory effects predominating at low heart rates and blood pressure effects at high heart rates.

scholarly journals Problems with Bazett QTc correction in paediatric screening of prolonged QTc interval

2020 ◽  
Vol 20 (1) ◽  
Author(s):  
Irena Andršová ◽  
Katerina Hnatkova ◽  
Kateřina Helánová ◽  
Martina Šišáková ◽  
Tomáš Novotný ◽  
...  
Keyword(s):  
Heart Rate ◽  
Supine Position ◽  
Qt Interval ◽  
Qtc Interval ◽  
Healthy Children ◽  
Long Qt ◽  
Normal Children ◽  
Heart Rates ◽  
Qt Intervals ◽  
Qt Syndrome

Abstract Background Bazett formula is frequently used in paediatric screening for the long QT syndrome (LQTS) and proposals exist that using standing rather than supine electrocardiograms (ECG) improves the sensitivity of LQTS diagnosis. Nevertheless, compared to adults, children have higher heart rates (especially during postural provocations) and Bazett correction is also known to lead to artificially prolonged QTc values at increased heart rates. This study assessed the incidence of erroneously increased QTc values in normal children without QT abnormalities. Methods Continuous 12-lead ECGs were recorded in 332 healthy children (166 girls) aged 10.7 ± 2.6 years while they performed postural manoeuvring consisting of episodes (in the following order) of supine, sitting, standing, supine, standing, sitting, and supine positions, each lasting 10 min. Detailed analyses of QT/RR profiles confirmed the absence of prolonged individually corrected QTc interval in each child. Heart rate and QT intervals were measured in 10-s ECG segments and in each segment, QTc intervals were obtained using Bazett, Fridericia, and Framingham formulas. In each child, the heart rates and QTc values obtained during supine, sitting and standing positions were averaged. QTc durations by the three formulas were classified to < 440 ms, 440–460 ms, 460–480 ms, and > 480 ms. Results At supine position, averaged heart rate was 77.5 ± 10.5 beat per minute (bpm) and Bazett, Fridericia and Framingham QTc intervals were 425.3 ± 15.8, 407.8 ± 13.9, and 408.2 ± 13.1 ms, respectively. At sitting and standing, averaged heart rate increased to 90.9 ± 10.1 and 100.9 ± 10.5 bpm, respectively. While Fridericia and Framingham formulas showed only minimal QTc changes, Bazett correction led to QTc increases to 435 ± 15.1 and 444.9 ± 15.9 ms at sitting and standing, respectively. At sitting, Bazett correction identified 51, 4, and 0 children as having the QTc intervals 440–460, 460–480, and > 480 ms, respectively. At sitting, these numbers increased to 118, 11, and 1, while on standing these numbers were 151, 45, and 5, respectively. Irrespective of the postural position, Fridericia and Framingham formulas identified only a small number (< 7) of children with QT interval between 440 and 460 ms and no children with longer QTc. Conclusion During screening for LQTS in children, the use of Bazett formula leads to a high number of false positive cases especially if the heart rates are increased (e.g. by postural manoeuvring). The use of Fridericia formula can be recommended to replace the Bazett correction not only for adult but also for paediatric ECGs.

Optimal Electrocardiographic Pulsing Windows and Heart Rate: Effect on Image Quality and Radiation Exposure at Dual-Source Coronary CT Angiography

Radiology ◽  
2008 ◽  
Vol 248 (3) ◽  
pp. 792-798 ◽  
Author(s):  
Annick C. Weustink ◽  
Nico R. Mollet ◽  
Francesca Pugliese ◽  
Willem B. Meijboom ◽  
Koen Nieman ◽  
...  
Keyword(s):  
Heart Rate ◽  
Image Quality ◽  
Radiation Exposure ◽  
Ct Angiography ◽  
Coronary Ct Angiography ◽  
Rate Effect ◽  
Coronary Ct ◽  
Dual Source ◽  
Heart Rate Effect

Heart rates of muskrats diving under simulated field conditions: persistence of the bradycardia response and factors modifying its expression

1989 ◽  
Vol 67 (7) ◽  
pp. 1783-1792 ◽  
Author(s):  
Robert A. MacArthur ◽  
Cindy M. Karpan
Keyword(s):  
Heart Rate ◽  
Body Temperature ◽  
Motor Activity ◽  
Water Temperature ◽  
Field Conditions ◽  
Diving Response ◽  
Heart Rates ◽  
Feeding Station ◽  
Wide Range ◽  
Simulated Field

A marked, rapidly deployed bradycardia accompanied every voluntary dive by muskrats diving under a wide range of simulated field conditions in the laboratory. Telemetered heart rates were typically stable during submergence, with little evidence of postdive tachycardia or anticipatory changes in cardiac frequency prior to onset or termination of spontaneous dives. The extent of bradycardia varied with the type of dive; heart rate was highest during foraging trips and lowest during escape dives provoked by the investigators. Diving heart rate was positively correlated with the predive rate in escape dives but not foraging or exploratory dives. In animals trained to swim an underwater maze separating a simulated lodge from a feeding station, the extent of bradycardia increased with the period of submergence. This relationship was strongest for escape dives and was attributed mainly to a reduction in motor activity with time submerged. Several escape dives more than 3 min in duration were documented in both field and laboratory and all were characterized by prolonged periods of inactivity underwater. Heart rate during exploratory and foraging dives varied positively with both water (4–30 °C) and telemetered abdominal (30–38.4 °C) temperature. Type of dive, body temperature, and water temperature accounted for 31% of the variance in heart rate of diving muskrats. These results suggest that while the classic diving response is largely preserved in freely diving muskrats, the extent of bradycardia varies with the nature of the dive and is subject to cortical and thermal influences.

Voluntary control of human heart rate: Effect on reaction to aversive stimulation.

1974 ◽  
Vol 83 (3) ◽  
pp. 261-267 ◽  
Author(s):  
Alan D. Sirota ◽  
Gary E. Schwartz ◽  
David Shapiro
Keyword(s):  
Heart Rate ◽  
Human Heart ◽  
Aversive Stimulation ◽  
Rate Effect ◽  
Voluntary Control ◽  
Heart Rate Effect

scholarly journals Problems with Bazett QTc Correction in Paediatric Screening of Prolonged QTc Interval

2020 ◽  
Author(s):  
Irena Andršová ◽  
Katerina Hnatkova ◽  
Kateřina Helánová ◽  
Martina Šišáková ◽  
Tomáš Novotný ◽  
...  
Keyword(s):  
Heart Rate ◽  
Supine Position ◽  
Qt Interval ◽  
Qtc Interval ◽  
Healthy Children ◽  
Long Qt ◽  
Normal Children ◽  
Heart Rates ◽  
Qt Intervals ◽  
Qt Syndrome

Abstract BackgroundBazett formula is frequently used in paediatric screening for the long QT syndrome (LQTS) and proposals exist that using standing rather than supine electrocardiograms (ECG) improves the sensitivity of LQTS diagnosis. Nevertheless, compared to adults, children have higher heart rates (especially during postural provocations) and Bazett correction is also known to lead to artificially prolonged QTc values at increased heart rates. This study assessed the incidence of erroneously increased QTc values in normal children without QT abnormalities.MethodsContinuous 12-lead ECGs were recorded in 332 healthy children (166 girls) aged 10.7±2.6 years while they performed postural manoeuvring consisting of episodes (in the following order) of supine, sitting, standing, supine, standing, sitting, and supine positions, each lasting 10 minutes. Detailed analyses of QT/RR profiles confirmed the absence of prolonged individually corrected QTc interval in each child. Heart rate and QT intervals were measured in 10-second ECG segments and in each segment, QTc intervals were obtained using Bazett, Fridericia, and Framingham formulas. In each child, the heart rates and QTc values obtained during supine, sitting and standing positions were averaged. QTc durations by the three formulas were classified to <440 ms, 440-460 ms, 460-480 ms, and >480 ms. ResultsAt supine position, averaged heart rate was 77.5±10.5 beat per minute (bpm) and Bazett, Fridericia and Framingham QTc intervals were 425.3±15.8, 407.8±13.9, and 408.2±13.1 ms, respectively. At sitting and standing, averaged heart rate increased to 90.9±10.1 and 100.9±10.5 bpm, respectively. While Fridericia and Framingham formulas showed only minimal QTc changes, Bazett correction led to QTc increases to 435±15.1 and 444.9±15.9 ms at sitting and standing, respectively. At sitting, Bazett correction identified 51, 4, and 0 children as having the QTc intervals 440-460, 460-480, and >480 ms, respectively. At sitting, these numbers increased to 118, 11, and 1, while on standing these numbers were 151, 45, and 5, respectively. Irrespective of the postural position, Fridericia and Framingham formulas identified only a small number (<7) of children with QT interval between 440 and 460 ms and no children with longer QTc.ConclusionDuring screening for LQTS in children, the use of Bazett formula leads to a high number of false positive cases especially if the heart rates are increased (e.g. by postural manoeuvring). The use of Fridericia formula can be recommended to replace the Bazett correction not only for adult but also for paediatric ECGs.

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