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Abstract
RATIONALE A hemodynamic relationship of pulmonary artery pressure (PAP) to pulmonary acceleration time (PAcT) has not yet been explicitly presented. OBJECTIVE We employed a logistic-based systolic model with a subtle modification for pulmonary circulation and provided a logical ground for the relationship between systolic PAP and PAcT using transthoracic echocardiography. Additionally, the logistic-based PAP estimation equation was deduced from the model to relate systolic PAP and PAcT. METHODS AND RESULTS This equation was statistically tested in comparison to existing PAP estimation equations. Results showed that the logistic-based PAP estimation equation was at least as accurate as previous equations with respect to previously published mean PAP versus PAcT values. After the subtle pulmonary modification of the model, the pulmonary blood flow velocity and pressure not only well reflected the underlying pulmonary circulation physiology, but could also be presented in harmony with systemic circulation physiology. CONCLUSIONS A future clinical study with actual systolic PAP versus PAcT measurements is needed to test the application of the logistic-based PAP estimation equation.
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Affiliation(s)
- Hyunsuk Frank Roh
- Department of Biomedical Science, Hanyang University College of Medicine and Graduate School of Biomedical Science and Engineering, Seoul, South Korea.
| | - Jung Mogg Kim
- Department of Microbiology and Biomedical Science, Hanyang University College of Medicine and Graduate School of Biomedical Science and Engineering, Seoul, South Korea.
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Vargas HM, Bass AS, Koerner J, Matis-Mitchell S, Pugsley MK, Skinner M, Burnham M, Bridgland-Taylor M, Pettit S, Valentin JP. Evaluation of drug-induced QT interval prolongation in animal and human studies: a literature review of concordance. Br J Pharmacol 2015; 172:4002-11. [PMID: 26031452 PMCID: PMC4543608 DOI: 10.1111/bph.13207] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2014] [Revised: 04/22/2015] [Accepted: 05/20/2015] [Indexed: 01/10/2023] Open
Abstract
Evaluating whether a new medication prolongs QT intervals is a critical safety activity that is conducted in a sensitive animal model during non-clinical drug development. The importance of QT liability detection has been reinforced by non-clinical [International Conference on Harmonization (ICH) S7B] and clinical (ICH E14) regulatory guidance from the International Conference on Harmonization. A key challenge for the cardiovascular safety community is to understand how the finding from a non-clinical in vivo QT assay in animals predicts the outcomes of a clinical QT evaluation in humans. The Health and Environmental Sciences Institute Pro-Arrhythmia Working Group performed a literature search (1960–2011) to identify both human and non-rodent animal studies that assessed QT signal concordance between species and identified drugs that prolonged or did not prolong the QT interval. The main finding was the excellent agreement between QT results in humans and non-rodent animals. Ninety-one percent (21 of 23) of drugs that prolonged the QT interval in humans also did so in animals, and 88% (15 of 17) of drugs that did not prolong the QT interval in humans had no effect on animals. This suggests that QT interval data derived from relevant non-rodent models has a 90% chance of predicting QT findings in humans. Disagreement can occur, but in the limited cases of QT discordance we identified, there appeared to be plausible explanations for the underlying disconnect between the human and non-rodent animal QT outcomes.
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Affiliation(s)
- Hugo M Vargas
- Integrated Discovery and Safety Pharmacology, Amgen, Inc., Thousand Oaks, CA, USA
| | - Alan S Bass
- Safety Assessment, Merck Research Laboratories, Boston, MA, USA
| | - John Koerner
- Center for Drug Evaluation and Research, U.S. Food and Drug Administration, Silver Spring, MD, USA
| | | | | | | | | | | | - Syril Pettit
- Health and Environmental Sciences Institute, Washington, DC, USA
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Oliveira MS, Muzzi RA, Muzzi LA, Cherem M, Mantovani MM. QT interval in healthy dogs: which method of correcting the QT interval in dogs is appropriate for use in small animal clinics? PESQUISA VETERINARIA BRASILEIRA 2014. [DOI: 10.1590/s0100-736x2014000500014] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The electrocardiography (ECG) QT interval is influenced by fluctuations in heart rate (HR) what may lead to misinterpretation of its length. Considering that alterations in QT interval length reflect abnormalities of the ventricular repolarisation which predispose to occurrence of arrhythmias, this variable must be properly evaluated. The aim of this work is to determine which method of correcting the QT interval is the most appropriate for dogs regarding different ranges of normal HR (different breeds). Healthy adult dogs (n=130; German Shepherd, Boxer, Pit Bull Terrier, and Poodle) were submitted to ECG examination and QT intervals were determined in triplicates from the bipolar limb II lead and corrected for the effects of HR through the application of three published formulae involving quadratic, cubic or linear regression. The mean corrected QT values (QTc) obtained using the diverse formulae were significantly different (ρ<0.05), while those derived according to the equation QTcV = QT + 0.087(1- RR) were the most consistent (linear regression). QTcV values were strongly correlated (r=0.83) with the QT interval and showed a coefficient of variation of 8.37% and a 95% confidence interval of 0.22-0.23 s. Owing to its simplicity and reliability, the QTcV was considered the most appropriate to be used for the correction of QT interval in dogs.
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Holzgrefe H, Ferber G, Champeroux P, Gill M, Honda M, Greiter-Wilke A, Baird T, Meyer O, Saulnier M. Preclinical QT safety assessment: Cross-species comparisons and human translation from an industry consortium. J Pharmacol Toxicol Methods 2014; 69:61-101. [DOI: 10.1016/j.vascn.2013.05.004] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2013] [Revised: 05/08/2013] [Accepted: 05/09/2013] [Indexed: 01/10/2023]
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Aylott M, Bate S, Collins S, Jarvis P, Saul J. Review of the statistical analysis of the dog telemetry study. Pharm Stat 2010; 10:236-49. [DOI: 10.1002/pst.454] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Kijtawornrat A, Panyasing Y, del Rio C, Hamlin RL. Assessment of ECG interval and restitution parameters in the canine model of short QT syndrome. J Pharmacol Toxicol Methods 2010; 61:231-7. [DOI: 10.1016/j.vascn.2010.02.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2009] [Accepted: 02/01/2010] [Indexed: 11/17/2022]
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Bavegems V, Duchateau L, Ham LV, Rick AD, Sys SU. Electrocardiographic reference values in whippets. Vet J 2009; 182:59-66. [PMID: 19524205 DOI: 10.1016/j.tvjl.2008.05.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2006] [Revised: 04/23/2008] [Accepted: 05/01/2008] [Indexed: 10/20/2022]
Abstract
The aim of this study was to determine the electrocardiographic characteristics of whippets and to compare the results with published reference values for a general dog population. Electrocardiographic parameters from 105 healthy whippets were used to establish reference values for the breed. The most important differences compared to published reference values were the higher median R-wave amplitudes in leads II, CV(6)LL and CV(6)LU. For some parameters (P-wave amplitude, ST-segment deflection and T-wave amplitude in lead II; R-wave amplitude in CV(5)RL), a marked percentage of the whippet values were above the published maximum reference data. The results confirmed that whippets have electrocardiographic characteristics similar to those reported in athletic heart syndrome in humans. Some of these characteristics could be erroneously taken as evidence of cardiac disease and clinicians should be aware of these factors to prevent unnecessary investigations in healthy dogs.
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Affiliation(s)
- Valérie Bavegems
- Department of Medicine and Clinical Biology of Small Animals, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820 Merelbeke, Belgium.
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8
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Chui RW, Fosdick A, Conner R, Jiang J, Bruenner BA, Vargas HM. Assessment of two external telemetry systems (PhysioJacket™ and JET™) in beagle dogs with telemetry implants. J Pharmacol Toxicol Methods 2009; 60:58-68. [DOI: 10.1016/j.vascn.2009.04.196] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2009] [Accepted: 04/28/2009] [Indexed: 10/20/2022]
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9
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Chui RW, Vargas HM. A comparison of three software platforms for automated ECG analysis. J Pharmacol Toxicol Methods 2009; 60:28-38. [DOI: 10.1016/j.vascn.2009.05.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2009] [Accepted: 05/10/2009] [Indexed: 10/20/2022]
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10
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Fossa AA. Assessing QT prolongation in conscious dogs: Validation of a beat-to-beat method. Pharmacol Ther 2008; 119:133-40. [DOI: 10.1016/j.pharmthera.2008.02.013] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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11
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Fossa AA. Assessing QT prolongation in conscious dogs: Validation of a beat-to-beat method. Pharmacol Ther 2008; 118:231-8. [DOI: 10.1016/j.pharmthera.2008.02.006] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2008] [Accepted: 02/22/2008] [Indexed: 11/15/2022]
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Koga T, Kuwano K, Kito G, Kanefuji K. Evaluation of QT interval using a linear model in individual cynomolgus monkeys. J Pharmacol Toxicol Methods 2007; 55:248-53. [PMID: 17141531 DOI: 10.1016/j.vascn.2006.10.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2006] [Accepted: 10/16/2006] [Indexed: 10/24/2022]
Abstract
INTRODUCTION The cynomolgus monkey, one of a number of primate species phylogenetically close to humans, is commonly used in cardiovascular research, but a method for determination of the RR interval-corrected QT interval in this species needs greater consideration. The objectives of this study were to determine a method for evaluating QT interval in cynomolgus monkeys individually, disregarding RR interval change artifacts, and to investigate prerequisite information for this method. METHODS The physiological QT-RR relationship for practical evaluation of QT interval was recorded and analyzed by 24-hour telemetric ECG monitoring. A linear model for log-transformed QT and RR intervals was used to correct the QT interval from RR interval change artifacts for each animal. Sample size was also estimated based on the simulation results. RESULTS Histograms showed that both QT and RR intervals had a right-heavy tail distribution. QT interval corrected individually by the linear model formula showed smaller within-animal variability than QTb and QTf, which were corrected by Bazett's formula and Fridericia's formula. The simulation results showed that the individual correction factor, beta(i), could be reliably estimated when at least 24 pairs of QT-RR baseline data were available. DISCUSSION As with humans, QT interval in cynomolgus monkeys varies widely between individuals. Therefore, a method for correcting QT interval individually should be considered, whenever extensive untreated data are available.
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Affiliation(s)
- Tadashi Koga
- Shin Nippon Biomedical Laboratories, Ltd., 2438 Miyanoura, Kagoshima, Kagoshima 891-1394, Japan.
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Cheng HC, Incardona J, McCullough B. Isolated perfused and paced guinea pig heart to test for drug-induced changes of the QT interval. J Pharmacol Toxicol Methods 2006; 54:278-87. [PMID: 16507347 DOI: 10.1016/j.vascn.2006.01.002] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2005] [Accepted: 01/18/2006] [Indexed: 11/25/2022]
Abstract
INTRODUCTION One of the biomarkers for assessing the risk of a cardiac adverse event is drug-induced prolongation of the QT interval. A model is needed for evaluating the potential liability of test compounds on QT interval in vitro. Since QT intervals can be generated from paced or spontaneously beating hearts, data so generated can also be used for validating QT(c) correction equations. METHODS Isolated guinea pig hearts were perfused in Locke's solution according to the Langendorff method. QT intervals were routinely measured from Lead II ECG waveforms. RESULTS Compounds known to inhibit HERG channel, such as dofetilide, prolonged the QT interval in this model. (+/-)Bay K8644, a calcium channel activator, prolonged the QT interval, while verapamil, a calcium channel blocker, shortened it. Procainamide, a sodium channel blocker, also prolonged the QT interval. Many of the compounds, which prolonged the QT interval, also prolonged PR interval, suggesting dual inhibition of the Ikr channel, the rapid component of delayed rectifier potassium channel, and the calcium channel. The QT/RR intervals exhibited a curvilinear relationship, which could be corrected into nearly straight horizontal lines by using correction equations derived from linear, parabolic, and hyperbolic models. However, these correction equations yielded different results on the QT prolongation produced by sotalol, which also slowed down the heart rate. With the data set obtained in this investigation, correction equations derived from linear and parabolic models worked better than the equations derived from the hyperbolic model. The exponential model did not fit at all. CONCLUSION QT intervals obtained under paced conditions provide the most direct and reliable QT information for a drug. The isolated perfused and paced guinea pig heart is a convenient model for studying the effect of compounds on QT interval in vitro.
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Affiliation(s)
- Hsien C Cheng
- Safety Pharmacology, Drug Safety Evaluation, Sanofi-Aventis, Bridgewater, NJ 08807, USA.
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Chiang AY, Holdsworth DL, Leishman DJ. A one-step approach to the analysis of the QT interval in conscious telemetrized dogs. J Pharmacol Toxicol Methods 2006; 54:183-8. [PMID: 16567113 DOI: 10.1016/j.vascn.2006.02.004] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2006] [Accepted: 02/12/2006] [Indexed: 11/27/2022]
Abstract
INTRODUCTION To account for heart rate-induced changes in the QT interval, correction formulas are generally applied to normalize the QT interval for heart rate. None of these formulas is entirely accurate because correction or normalization of any parameter in biology may introduce an additional source of variation in estimating the parameter. In this article, a one-step approach for the statistical analysis of the QT interval was proposed based on modeling the functional relationship between the QT interval and heart rate. METHODS The QT-HR relationship was incorporated into the statistical analysis to provide a model-based correction. This was accomplished by including HR as a covariate in the QT interval analysis. The approach was demonstrated using data generated from Lilly Research Laboratories. We compared the false positive rate and statistical power of QT, QTcF, and the proposed one-step method. RESULTS We found the one-step method demonstrated the greatest sensitivity in detecting a QT interval change without an increase in the false positive rate. It was shown that the one-step QT analysis could detect a 5%-6% increment of the QT interval. This is approximately equivalent to an increase of 11-13 ms in QT interval in beagle dogs. DISCUSSION Several advantages and unique features of the one-step method are discussed. These include evaluating treatment effect on QT without applying a heart rate correction formula and estimating QT difference flexibly at any selected heart rate. In addition to the linear QT-HR relationship, other functional relationships can be easily implemented to this approach.
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Affiliation(s)
- Alan Y Chiang
- Global Statistical Sciences and Toxicology, Lilly Research Laboratories, Eli Lilly and Company, P.O. Box 708, Greenfield, IN 46140, USA.
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Ollerstam A, Persson AH, Visser SAG, Fredriksson JM, Forsberg T, Nilsson LB, Eklund G, Wiklund SJ, Gabrielsson J, Duker G, Al-Saffar A. A novel approach to data processing of the QT interval response in the conscious telemetered beagle dog. J Pharmacol Toxicol Methods 2006; 55:35-48. [PMID: 16581270 DOI: 10.1016/j.vascn.2006.02.009] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2005] [Accepted: 02/16/2006] [Indexed: 01/10/2023]
Abstract
INTRODUCTION Drug-induced QT interval prolongation may lead to ventricular arrhythmias. The aim of the study was to optimize QT interval data processing to quantify drug-induced QT interval prolongation in the telemetry instrumented conscious dog model. METHODS The test substances cisapride, dofetilide, haloperidol, and terfenadine and corresponding vehicles were given to male and female beagle dogs during two consecutive 90-min intravenous infusions. Cardiovascular parameters were recorded for 24 h and exposure to the drugs was measured. The delayed response in the QT interval after an abrupt change in heart rate was investigated. Eight mathematical models to describe the QT interval-heart rate relationship were compared and different sets of covariates were used to quantify the drug-induced effect on the QT interval. RESULTS After an abrupt decrease in heart rate, a 75% adaptation of the QT interval was reached after 54+/-9 s. A linear model was preferred to correct the drug-induced effect on the QT interval for heart rate, vehicle effect, serial correlation, plasma concentration and time of day. All test substances significantly prolonged the QT interval. DISCUSSION To optimize the processing of QT interval data, the delay in QT interval response after an abrupt change in heart rate should be considered. The QT interval-heart rate relationship and vehicle response were individual-specific and corrections were therefore made individually. When estimating the drug-induced effect on the QT interval it is considered advantageous to use plasma concentration as a covariate, as well as adjusting for vehicle effect and serial correlation in measurements. The conscious dog model detected significant increases in the QT interval for all test substances investigated.
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Affiliation(s)
- Anna Ollerstam
- AstraZeneca R&D Södertälje, SE-151 85 Södertälje, Sweden.
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Fossa AA, Wisialowski T, Crimin K. QT Prolongation Modifies Dynamic Restitution and Hysteresis of the Beat-to-Beat QT-TQ Interval Relationship during Normal Sinus Rhythm under Varying States of Repolarization. J Pharmacol Exp Ther 2005; 316:498-506. [PMID: 16204470 DOI: 10.1124/jpet.105.095471] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The analysis of cardiac electrical restitution (the relationship between an action potential duration and its preceding diastolic interval) has been used to predict arrhythmia liability. However, the procedure to measure restitution is invasive and disrupts normal physiological autonomic balance. Dynamic analysis of sequential beat-to-beat ECG data was used to study restitution under normal sinus rhythm and to quantify changes in temporal hysteresis with heart rate acceleration/deceleration during QT prolongation. Congenital long QT (LQT) 1 and LQT2 syndromes during sympathetic stimulation were modeled because of their association with increased risk of ventricular arrhythmia. Temporal heterogeneity and hysteresis of restitution were examined in the conscious dog under varying conditions of delayed repolarization using either the selective inhibitors of the slowly activating delayed rectifier potassium current (R)-2-(4-trifluoromethyl)-N-[2-oxo-5-phenyl-1-(2,2,2-trifluoroethyl)-2,3-dihydro-1H-benzo[e][1,4]diazepin-3-yl]acetamide (L-768,673); the rapidly activating delayed rectifier potassium current (1-[2-(6-methyl-2-pyridyl)ethyl]-4-methyl-sulfonylaminobenzoyl)-piperidine (E-4031); or a combination of both at rest and during heart rate acceleration with sympathetic stimulation using isoproterenol challenges. Impaired repolarization with the combination of E-4031 and L-768,673 increased heterogeneity of restitution at rest 55 to 91%, increased hysteresis during heart rate acceleration after isoproterenol challenge by approximately 40 to 60%, and dramatically reduced the minimum TQ interval by 72% to only 28 ms. Impaired repolarization alters restitution during normal sinus rhythm and increases hysteresis/heterogeneity during heart rate acceleration following sympathetic stimulation. Thus, dynamic beat-to-beat measurements of restitution could lead to clinically applicable ECG obtained biomarkers for assessment of changes associated with arrhythmogenic risk.
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Affiliation(s)
- Anthony A Fossa
- Pfizer Global Research and Development, Groton, CT 06340, USA.
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Ollerstam A, Visser SAG, Persson AH, Eklund G, Nilsson LB, Forsberg T, Wiklund SJ, Gabrielsson J, Duker G, Al-Saffar A. Pharmacokinetic-pharmacodynamic modeling of drug-induced effect on the QT interval in conscious telemetered dogs. J Pharmacol Toxicol Methods 2005; 53:174-83. [PMID: 16140023 DOI: 10.1016/j.vascn.2005.07.002] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2005] [Accepted: 07/04/2005] [Indexed: 11/27/2022]
Abstract
INTRODUCTION To assure drug safety, the investigation of the relationship between plasma concentration and drug-induced prolongation of the QT interval of the ECG is a challenge in drug discovery. For this purpose, dofetilide was utilized to demonstrate the benefits of characterizing the complete time course of concentrations and effect in conscious beagle dogs in the assessment of drug safety. METHOD On two separate occasions, four male and two female beagle dogs were given vehicle or the test substance, dofetilide (0.25 mumol/kg), over a 3-h intravenous infusion. Cardiovascular parameters, including QT intervals, were recorded for 24-h using radiotelemetry. The QT interval was corrected individually for heart rate, vehicle treatment, and serial correlation (QT(c)). Exposure (plasma concentration) to dofetilide was measured and described by a two-compartment model. The individual concentration-time course of dofetilide was linked to the QT(c) interval via an effect compartment and a pharmacodynamic E(max) model, to account for the observed hysteresis. RESULTS Dofetilide induced a concentration-dependent increase in the QT(c) interval, with an EC(50) of 9 nM (3-30 nM, 95% C.I.) and an E(max) of 59+/-9 ms. A hysteresis loop was observed by plotting plasma concentrations vs. QT interval in time order, indicating a delay in onset of effect. It was found to have an equilibrium half-life of 11+/-8 min. Based on the parameters potency and E(max), a representation was made of the drug-induced changes to the QT interval. DISCUSSION An effect compartment model was found to accurately mimic the QT interval prolongation following administration of the test substance, dofetilide. The assessment of the individual concentration-effect relationship and confounding factors such as hysteresis might provide a better prediction of the safety profiles of new drug candidates.
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Affiliation(s)
- Anna Ollerstam
- AstraZeneca R&D Södertälje, SE-151 85 Södertälje, Sweden.
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Hamlin RL, Kijtawornrat A, Keene BW. How many cardiac cycles must be measured to permit accurate RR, QT, and QTc estimates in conscious dogs? J Pharmacol Toxicol Methods 2005; 50:103-8. [PMID: 15385084 DOI: 10.1016/j.vascn.2004.03.013] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2003] [Accepted: 03/05/2004] [Indexed: 11/20/2022]
Abstract
INTRODUCTION Electrocardiography is an essential tool to assess the liability of test articles to produce torsade de pointes. The number of cardiac cycles that must be measured from a dog to accurately characterize the relationship between RR and QT intervals, and thus assess this liability, is unknown. METHODS In this study, electrocardiograms (ECGs) were obtained from 12 conscious dogs with sinus rhythm. In each dog, RR and QT intervals were measured for 12 cardiac cycles. Measurements for each were then averaged over all 12 cycles, and those results compared to the average of both the initial 6 and 3 cycles, as well as to the middle cycle alone, for 12, 6, and 4 of the dogs. QTc was calculated by dividing each QT by the cube root of the preceding RR interval. RESULTS We found no significant differences in the results of measurements of RR, QT, or QTc obtained from 12, 6, 3, or 1 cycle, whether from 12, 6, or 4 dogs. Intraobserver variability of ECG measurements was tested by having a single observer measure 10 copies of 12 different ECGs. The greatest coefficient of variation (S.D./mean) for the measurement of any ECG parameter was less than 2.5%. DISCUSSION We conclude that measurements of RR and QT intervals made by a trained observer from 1 cardiac cycle accurately reflect those that are averaged from 3, 6, or 12 cycles whether the number of dogs per group is 12, 6, or 4.
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Affiliation(s)
- Robert L Hamlin
- Department of Veterinary Biosciences, The Ohio State University, VMAB 480, 1900 Coffey Road, Columbus, OH 43210-1093, USA.
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Ferasin L, Faena M, Henderson SM, Langford K, Darke PGG. Use of a multi-stage exercise test to assess the responsiveness of rate-adaptive pacemakers in dogs. J Small Anim Pract 2005; 46:115-20. [PMID: 15789806 DOI: 10.1111/j.1748-5827.2005.tb00301.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
OBJECTIVES To assess the ventricular rate response of rate-adaptive (VVIR) pacemakers in dogs using a multi-stage exercise test. METHODS The rate-responsiveness of VVIR pacemakers was assessed in seven dogs with complete atrioventricular (AV) block and implanted with various models of pulse generators (six motion sensors and one automatic dual-sensor rate-response pacemaker). Response activity was assessed with a multi-stage exercise test on a treadmill. Atrial and ventricular rate were analysed retrospectively at the end of the test and the AV ratio was calculated after each minute of exercise. RESULTS During exercise, the mean (sd) AV ratio recorded in all paced dogs was 1.7 (0.5) (expected physiological ratio 1.0), although a variety of individual performances was observed. A poor response (AV ratio 2.8 [0.2]) was obtained with the automatic dual-sensor pacemaker, suggesting that this type of rate-responsive device may not be indicated for implantation in dogs with complete AV block. The overall AV ratio for the six dogs implanted with motion sensors was 1.4 (0.2), showing a better performance of these pacemakers during exercise. CLINICAL SIGNIFICANCE This multi-stage exercise test represents an easy and repeatable method for assessing the accuracy of rate-responsive sensors and offers valuable information for the correct setting of VVIR pacemakers in dogs.
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Affiliation(s)
- L Ferasin
- University of Bristol, Department of Clinical Veterinary Science, Division of Companion Animals, Langford House, Langford, Bristol BS40 5DU
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Miyazaki H, Watanabe H, Kitayama T, Nishida M, Nishi Y, Sekiya K, Suganami H, Yamamoto K. QT PRODACT: Sensitivity and Specificity of the Canine Telemetry Assay for Detecting Drug-Induced QT Interval Prolongation. J Pharmacol Sci 2005; 99:523-9. [PMID: 16493192 DOI: 10.1254/jphs.qt-c9] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
Abstract
The purpose of this investigation was to define the sensitivity and specificity of the canine telemetry assay for detecting drug-induced QT interval prolongation. Data from twelve studies generated in the QT PRODACT project were used in this investigation. The study design was a 4x4 Latin square cross-over design and included the following drugs: MK-499, E-4031, terfenadine, haloperidol, cisapride, bepridil, propranolol, diphenhydramine, captopril, verapamil, amoxicillin, and ciprofloxacin. The estimated root squared error of the model, which estimated the slope of the QT-RR relationships for each animal, for all dogs during the pre-dosing period was 5.45%. Using the QT-RR model, the sensitivity and specificity in each cutoff value that judges QT prolongation were estimated based on the experiment errors and measurement errors in the 12 studies. When the cutoff value was 5%, the sensitivity in 10% prolongation was 0.978 and the specificity in 0% was 0.996. In conclusion, it was judged that a 5% cutoff value for changes in heart rate corrected QT interval using the canine telemetry assay is practical, and the sensitivity and specificity of the telemetry assay are very high when using the analytical method presented here. Based upon this information, the canine telemetry assay using the individual subject heart rate correction model is recommended as a sensitive test system for the in vivo assessment of risk for QT interval prolongation.
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Affiliation(s)
- Hiroyasu Miyazaki
- Japan Pharmaceutical Manufacturers Association (JPMA)/QT PRODACT, Tokyo, Japan.
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Toyoshima S, Kanno A, Kitayama T, Sekiya K, Nakai K, Haruna M, Mino T, Miyazaki H, Yano K, Yamamoto K. QT PRODACT: In Vivo QT Assay in the Conscious Dog for Assessing the Potential for QT Interval Prolongation by Human Pharmaceuticals. J Pharmacol Sci 2005; 99:459-71. [PMID: 16493187 DOI: 10.1254/jphs.qt-a2] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
Abstract
The goal of the present study was to examine the utility of the conscious dog model by assessing the QT-interval-prolonging potential of ten positive compounds that have been reported to induce QT interval prolongation in clinical use and seven negative compounds considered not to have such an effect. Three doses of test compounds or vehicle were administered orally to male beagle dogs (n=4), and telemetry signals were recorded for 24 h after administration. All positive compounds (astemizole, bepridil, cisapride, E-4031, haloperidol, MK-499, pimozide, quinidine, terfenadine, and thioridazine) caused a significant increase in the corrected QT (QTc) interval, with a greater than 10% increase achieved at high doses. In contrast, administration of negative compounds (amoxicillin, captopril, ciprofloxacin, diphenhydramine, nifedipine, propranolol, and verapamil) did not produce any significant change in the QTc interval, with the exception of nifedipine that may have produced an overcorrection of the QTc interval due to increased heart rate. The estimated plasma concentrations of the positive compounds that caused a 10% increase in the QTc interval were in good agreement with the plasma/serum concentrations achieved in humans who developed prolonged QT interval or torsade de pointes (TdP). Although careful consideration should be given to the interpretation of QT data with marked heart rate change, these data suggest that an in vivo QT assay using the conscious dog is a useful model for the assessment of QT interval prolongation by human pharmaceuticals.
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Affiliation(s)
- Shigeki Toyoshima
- Japan Pharmaceutical Manufacturers Association (JPMA)/QT PRODACT, Tokyo, Japan.
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Ando K, Hombo T, Kanno A, Ikeda H, Imaizumi M, Shimizu N, Sakamoto K, Kitani SI, Yamamoto Y, Hizume S, Nakai K, Kitayama T, Yamamoto K. QT PRODACT: In Vivo QT Assay With a Conscious Monkey for Assessment of the Potential for Drug-Induced QT Interval Prolongation. J Pharmacol Sci 2005; 99:487-500. [PMID: 16493189 DOI: 10.1254/jphs.qt-a4] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
Abstract
In safety pharmacology studies, the effects on the QT interval of electrocardiograms are routinely assessed using a telemetry system in cynomolgus monkeys. However, there is a lack of integrated databases concerning in vivo QT assays in conscious monkeys. As part of QT Interval Prolongation: Project for Database Construction (QT PRODACT), the present study examined 10 positive compounds with the potential to prolong the QT interval and 6 negative compounds considered to have no such effect on humans. The experiments were conducted at 7 facilities in accordance with a standard protocol established by QT PRODACT. The vehicle or 3 doses of each test compound were administered orally to male cynomolgus monkeys (n=3-4), and telemetry signals were recorded for 24 h. None of the negative compounds prolonged the corrected QT using Bazett's formula (QTcB) interval. On the other hand, almost all of the positive compounds prolonged the QTcB interval, but haloperidol, terfenadine, and thioridazine did not. The failure to detect the QTcB interval prolongation appeared to be attributable for the differences in metabolism between species and/or disagreement with Bazett's formula for tachycardia. In the cynomolgus monkeys, astemizole induced Torsade de Pointes and cisapride caused tachyarrhythmia at lower plasma concentrations than those observed in humans and dogs. These results suggest that in vivo QT assays in conscious monkeys represent a useful model for assessing the risks of drug-induced QT interval prolongation.
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Affiliation(s)
- Kentaro Ando
- Japan Pharmaceutical Manufacturers Association (JPMA)/QT PRODACT, Tokyo, Japan.
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23
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Fossa AA, Wisialowski T, Magnano A, Wolfgang E, Winslow R, Gorczyca W, Crimin K, Raunig DL. Dynamic Beat-to-Beat Modeling of the QT-RR Interval Relationship: Analysis of QT Prolongation during Alterations of Autonomic State versus Human Ether a-go-go-Related Gene Inhibition. J Pharmacol Exp Ther 2004; 312:1-11. [PMID: 15306635 DOI: 10.1124/jpet.104.073288] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Methods to correct the QT interval for heart rate are often in disagreement and may be further confounded by changes in autonomic state. This can be problematic when trying to distinguish the changes in QT interval by either drug-induced delayed repolarization or from autonomic-mediated physiological responses. Assessment of the canine dynamic QT-RR interval relationship was visualized by novel programming of the dynamic beat-to-beat confluence of data or "clouds". To represent the nonuniformity of the clouds, a bootstrap sampling method that computes the mathematical center of the uncorrected beat-to-beat QT value (QTbtb) with upper 95% confidence bounds was adopted and compared with corrected QT (QTc) using standard correction factors. Nitroprusside-induced reflex tachycardia reduced QTbtb by 43 ms, whereas an increase of 55 and 16 ms was obtained using the Bazett (QTcB) and Fridericia (QTcF) formulae, respectively. Phenylephrine-induced reflex bradycardia increased QTbtb by 3 ms but decreased QTcB by 20 ms and QTcF by 12 ms. Delayed repolarization with E-4031 (1-[2-(6-methyl-2-pyridyl)ethyl]-4-methylsulfonylaminobenzoyl)-piperidine), an inhibitor of rectifier potassium current, increased QTbtb by 26 ms but QT prolongation calculations using QTcF and QTcB were between 12 and 52% less, respectively, when small decreases in heart rate (5-8 beats per minute) were apparent. Dynamic assessment of beat-to-beat data, using the bootstrap method, allows quantification of QT interval changes under varying conditions of heart rate, autonomic tone, and direct repolarization that may not be distinguishable with use of standard correction factors.
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Affiliation(s)
- Anthony A Fossa
- Pfizer Global Research and Development, Eastern Point Rd., Bldg. 118, MS 4036, Groton, CT 06340, USA.
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24
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Guth BD, Germeyer S, Kolb W, Markert M. Developing a strategy for the nonclinical assessment of proarrhythmic risk of pharmaceuticals due to prolonged ventricular repolarization. J Pharmacol Toxicol Methods 2004; 49:159-69. [PMID: 15172012 DOI: 10.1016/j.vascn.2004.02.006] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2004] [Accepted: 02/20/2004] [Indexed: 10/26/2022]
Abstract
The aspects for developing a strategy for the preclinical testing of drug candidates for proarrhythmic potential are presented. The rationale for such a strategy reflects primarily the needs for efficient and scientifically based drug development and also attempts to anticipate the possible outcomes of the currently ongoing regulatory activity (ICH S7b and E14). Whereas a wealth of new data have emerged over the past few years, demonstrating the utility of test systems for detecting drug effects on myocardial repolarization, the current regulatory trend appears to not use such data for the clinical trial design or risk assessment. Nevertheless, certain types of preclinical tests are highly recommended for optimizing drug development, despite their still questionable regulatory acceptance. This includes (1) testing for blockade of I(Kr) or hERG-mediated potassium current in heterologous cell systems, (2) measurement of effects on the myocardial action potential in vitro; and (3) assessment of effects on the ECG in a well-conducted in vivo study. Due to their requirement for little compound, the first two in vitro tests lend themselves for early safety testing of drug candidates still in the lead optimization phase of drug discovery; together, they form a useful and predictive in vitro assessment. This strategy is not new but reflects what was initially suggested by the Committee for Proprietary Medicinal Products (CPMP) some years ago. However, the validation of such a strategy and its utility in drug development is now well established and recommended, independent from future regulatory requirements.
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Affiliation(s)
- Brian D Guth
- Department of Drug Discovery Support, Boehringer Ingelheim Pharma GmbH and Co. KG, Birkendorferstrasse 65, D-88397 Biberach an der Riss, Germany.
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Tracey WR, Allen MC, Frazier DE, Fossa AA, Johnson CG, Marala RB, Knight DR, Guzman-Perez A. Zoniporide: a potent and selective inhibitor of the human sodium-hydrogen exchanger isoform 1 (NHE-1). CARDIOVASCULAR DRUG REVIEWS 2003; 21:17-32. [PMID: 12595915 DOI: 10.1111/j.1527-3466.2003.tb00103.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The sodium-hydrogen exchanger isoform-1 (NHE-1) plays an important role in the myocardial response to ischemia-reperfusion; inhibition of this exchanger protects against ischemic injury, including reduction in infarct size. Herein we describe a novel, potent, and highly selective NHE-1 inhibitor, zoniporide (CP-597,396; [1-(quinolin-5-yl)-5-cyclopropyl-1H-pyrazole-4-carbonyl] guanidine). Zoniporide inhibits human NHE-1 with an IC(50) of 14 nM, has >150-fold selectivity vs. other NHE isoforms, and potently inhibits ex vivo NHE-1-dependent swelling of human platelets. This compound is well tolerated in preclinical animal models, exhibits moderate plasma protein binding, has a t(1/2) of 1.5 h in monkeys, and has one major active metabolite. In both in vitro and in vivo rabbit models of myocardial ischemia-reperfusion injury, zoniporide markedly reduced infarct size without adversely affecting hemodynamics or cardiac function. In the isolated heart (Langendorff), zoniporide elicited a concentration-dependent reduction in infarct size (EC(50) = 0.25 nM). At 50 nM it reduced infarct size by 83%. This compound was 2.5-20-fold more potent than either eniporide or cariporide (EC(50)s of 0.69 and 5.11 nM, respectively), and reduced infarct size to a greater extent than eniporide. In open chest, anesthetized rabbits, zoniporide also elicited a dose-dependent reduction in infarct size (ED(50) = 0.45 mg/kg/h) and inhibited NHE-1-mediated platelet swelling (93% inhibition at 4 mg/kg/h). Furthermore, zoniporide attenuated postischemic cardiac contractile dysfunction in conscious primates, and reduced both the incidence and duration of ischemia-reperfusion-induced ventricular fibrillation in rats. Zoniporide represents a novel class of potent and selective human NHE-1 inhibitors with potential utility for providing cardioprotection in a clinical setting.
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Affiliation(s)
- W Ross Tracey
- Pfizer Global Research and Development, Groton, CT 06340, USA.
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Finley MR, Lillich JD, Gilmour RF, Freeman LC. Structural and functional basis for the long QT syndrome: relevance to veterinary patients. J Vet Intern Med 2003; 17:473-88. [PMID: 12892298 DOI: 10.1111/j.1939-1676.2003.tb02468.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Long QT syndrome (LQTS) is a condition characterized by prolongation of ventricular repolarization and is manifested clinically by lengthening of the QT interval on the surface ECG. Whereas inherited forms of LQTS associated with mutations in the genes that encode ion channel proteins are identified only in humans, the acquired form of LQTS occurs in humans and companion animal species. Often, acquired LQTS is associated with drug-induced block of the cardiac K+ current designated I(Kr). However, not all drugs that induce potentially fatal ventricular arrhythmias antagonize I(Kr), and not all drugs that block I(Kr), are associated with ventricular arrhythmias. In clinical practice, the extent of QT interval prolongation and risk of ventricular arrhythmia associated with antagonism of I(Kr) are modulated by pharmacokinetic and pharmacodynamic variables. Veterinarians can influence some of the potential risk factors (eg, drug dosage, route of drug administration, presence or absence of concurrent drug therapy, and patient electrolyte status) but not all (eg, patient gender/genetic background). Veterinarians need to be aware of the potential for acquired LQTS during therapy with drugs identified as blockers of HERG channels and I(Kr).
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Affiliation(s)
- Melissa R Finley
- Department of Anatomy and Physiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506-5802, USA
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Fossa AA, DePasquale MJ, Raunig DL, Avery MJ, Leishman DJ. The relationship of clinical QT prolongation to outcome in the conscious dog using a beat-to-beat QT-RR interval assessment. J Pharmacol Exp Ther 2002; 302:828-33. [PMID: 12130750 DOI: 10.1124/jpet.102.035220] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
QT interval prolongation of the electrocardiogram has been associated with the occurrence of life-threatening fatal ventricular arrhythmias. To understand the relationship between preclinical cardiac conduction assessment to clinical outcome, comparisons of free (unbound)-plasma drug concentrations and their associated effects in the conscious mongrel dog were made to the free plasma concentrations in humans reported to produce QT prolongation. E-4031 (an experimental class III antiarrhythmic), cisapride, terfenadine, terodiline, and verapamil all affect cardiac repolarization and can produce QT prolongation in humans. In the conscious dog, the QT interval was assessed on a beat-to-beat basis in relation to each preceding RR interval at concentrations approximating the same unbound human concentrations. E-4031, cisapride and terodiline statistically increased the QT(RR1000) interval [the QT interval at a 60 beats/min (bpm) heart rate] 23, 8, and 9 ms, respectively, at concentrations 0.3 to 15.8 times their relevant clinical level. Increases were not observed for terfenadine or verapamil (p > 0.05 at all doses). Inspection of individual dog QT versus RR interval relationships showed clear QT interval responses specific to each treatment but not readily apparent when data are averaged at a heart rate of 60 bpm. For specific rectifier K(+) current (IKr) blockers, robust effects on mean QT prolongation can be detected. However, for drugs that affect repolarization through multiple channels, the effect on the mean QT interval may be more difficult to detect. Inspection of the beat-to-beat QT-RR interval relationship in an individual animal can increase the sensitivity for more accurate clinical prediction.
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Affiliation(s)
- Anthony A Fossa
- Pfizer Global Research and Development, Eastern Point Road, Building 118, MS 4036, Groton, CT 06340, USA.
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Batey AJ, Doe CPA. A method for QT correction based on beat-to-beat analysis of the QT/RR interval relationship in conscious telemetred beagle dogs. J Pharmacol Toxicol Methods 2002; 48:11-9. [PMID: 12750037 DOI: 10.1016/s1056-8719(03)00009-1] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
INTRODUCTION Drug-induced QT prolongation is a major clinical risk factor for arrhythmia induction, particularly torsades de pointes. QT interval is rate dependent, and many formulae exist that attempt to correct QT for changes in heart rate. Most correction factors are acknowledged to overcorrect at high heart rates, undercorrect at low heart rates, and tend to be species specific. Data collected from computerised data acquisition systems are normally reported as means over a given logging period, and so extremes of heart rate are averaged out. Therefore, the aim of this study was to develop a technique for assessing drug-induced changes in the QT/RR relationship, which is simple, suitable for small group sizes, and better able to determine rate-dependent effects of drugs. METHODS Telemetred beagle dogs (n=4) instrumented for the measurement of electrocardiogram (ECG) were monitored for four separate 20-h periods to define the control QT/RR relationship. Data were binned by RR interval, in 10 ms bins, to produce a control curve. Each dog was treated with vehicle and sotalol (4, 8, 32 mg/kg) in a crossover design to determine whether drug-induced changes in the QT/RR relationship could be detected using the data binning technique. RESULTS The control QT/RR relationship was curvilinear with a steep section for RR intervals below 580 ms, and was much less steep after this point. Sotalol produced QT prolongation and bradycardia-Fridericia's correction (QTf) reduced the magnitude of this prolongation. The data analysed by the binning technique showed a larger prolongation in QT than was suggested by QTf, and an inverse frequency-dependent response. DISCUSSION Beat-to-beat analysis and binning allows accurate determination of the QT/RR relationship and assessment of QT prolongation without recourse to mathematical modelling. It also highlights the importance of assessing QT effects in well-trained animals over a range of heart rates.
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Affiliation(s)
- Andrew J Batey
- Safety Pharmacology, GlaxoSmithKline, The Frythe, Welwyn, Herts AL6 9AR, UK.
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Curtis MJ. Focused section on QT correction for heart rate. J Pharmacol Toxicol Methods 2002; 48:1. [PMID: 12750035 DOI: 10.1016/s1056-8719(03)00007-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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