- Email: [email protected]
Evaluation of Respiratory Inductive Plethysmography using the EMKABelt (Jacket) system in the conscious beagle dog
Abstracts
Comparison of cardiac electrophysiological and mechanical effects of torsadogens in the isolated normal and failing rabbit hearts Anusak Kijtawornrata, Suwanakiet Sawangkoona, Carlos Del Riob, Robert L. Hamlinc
183
that are considered. The increase in respiration rate by drug B was identified using both methods. It is concluded that respiration rate can be assessed using HRV analysis from ECG obtained in dog telemetry studies.
a
Department of Physiology, Faculty of Veterinary Science, Chulalongkorn University, Bangkok, Thailand b QTest Labs, LLC. Columbus, OH, United States c Department of Veterinary Biosciences, The Ohio State University and QTest Labs, Columbus, OH, United States Lengthening of QTc is the usual signal to indicate torsadogenic potential of therapeutic agent. However from experience with pentobarbital and amiodarone, both of which lengthen QTc dramatically but seldom produce torsades de pointes (TdP), it is clear that QTc—or even IC50 for hERG physiology—is not a perfect predictor. Thus this feasibility study was conducted to determine if known torsadogens (cisapride, dofetilide, and quinidine), might actually produce TdP in Langendorff preparation of a failing heart compared with normal healthy heart. Heart failure was induced by ligation of LAD and descending branch of LC coronary arteries. After one month of coronary artery ligation, all rabbits were anesthetized with ketamine/xylazine, the hearts were removed quickly, and they were perfused with normal Krebs solution in a Langendorff preparation to which escalating concentrations of torsadogens were added. RR, QT, and QTc(F) were longer, at rest, for failing hearts than for normals. In response to all three torsadogens, RR, QT and QTc lengthened similarly in a dose–response manner in both the failing and normal hearts. Neither the failing nor the normal hearts developed TdP. Compared to normal hearts, the failing isolated perfused heart produced clear differences in electrophysiological and mechanical properties. Langendorff-perfused hearts from rabbits with failing hearts (i.e., with already prolonged QTc), appear to develop less lengthening of RR, QT, and QTc than in normals. Langendorff preparations of failing hearts do not appear to be more permissive to developing TdP.
doi:10.1016/j.vascn.2012.08.085
doi:10.1016/j.vascn.2012.08.086
Effects of autonomic interventions on heart rate variability in ambulatory, telemetrized dogs Susan R. Arthur, Brenda L. Lehman, Jun Cao, James K. Hennan Bristol-Myers Squibb, Princeton, NJ, United States Clinical evidence demonstrates the importance of the autonomic nervous system (ANS) in triggering and/or sustaining ventricular arrhythmias. Sympathetic stimulation may reduce ventricular refractory period and fibrillation threshold, enhancing automaticity and promoting arrhythmia, while vagal stimulation prolongs refractoriness, reducing automaticity. Heart rate variability (HRV) evaluation utilizing time (T) and frequency (F) domain analyses may be used to assess drug-related effects on the ANS. Cardiovascular data were evaluated in 4 chronically instrumented telemetrized dogs before and after single autonomic blockade (30 min IV infusions) with atropine (competitive muscarinic antagonist, 20 mg/kg), or propranolol (non- selective ßadrenergic antagonist, 1 mg/kg), and the two combined, as compared to 0.9% saline vehicle. Beat-to-beat variability was assessed via Kubios HRV©. Data were expressed in 30- and 60-min periods. Atropine alone or with propranolol decreased RR and T variables (SDNN, RMSS and NN50%) for 2.5 h compared to vehicle infusion. Low F increased for 1.5 h, High F decreased for 1 h, and LF/HF increased during the 2nd 30-min period postdose. Propranolol alone had minimal effect on T and F variables but HR declined over 1.5 h. Atropine and propranolol together minimized negative inotropic effects and abolished chronotropic effects observed with propranolol alone. Parasympathetic inhibition (atropine) had greater effects on HRV with minimal effect from sympathetic blockade. Parasympathetic/vagal tone contributes more significantly to HRV in the dog.
Respiration rate derived from ECG in dogs Rikard Pehrson, Aliaksandr Bulhak
doi:10.1016/j.vascn.2012.08.087
AstraZeneca, Södertälje, Sweden
Evaluation of Respiratory Inductive Plethysmography using the EMKABelt (Jacket) system in the conscious beagle dog Stuart Purbrick, Stephen Jordan, Simon Moore, David Butler, Adam French, Deborah Jones, Emma Peake, Victoria Milner, Peter Davies, Ken Meecham
The heart rhythm in dogs displays sinus arrhythmia mainly due to respiration. This arrhythmia can be studied using software that transforms ECG RR intervals into frequency/variability relationship (i.e. heart rate variability—HRV). We investigated if ECG RR intervals could be used as a surrogate marker for respiration rate. Respiration rate, measured by face mask, was compared to the results obtained from HRV sinus arrhythmia. Twelve male beagle dogs were used. ECG was measured by means of telemetry (DataSci). Data was obtained from prior to dosing and up to 1 h after dosing, from three studies. Study I: vehicle or drug M given intravenously, study II: vehicle or drug A (3 doses) and study III: vehicle or drug B (3 doses) (both dosed by inhalation). Respiration rate was measured in 5-minute sections using the mask, and ECG RR intervals were obtained from the same period and analysed (http:// kubios.uku.fi/) and for each segment the frequency (above 0.15 Hz) with the top variability was extracted. The two methods were compared statistically using the Bland and Altman method for assessing agreement between methods. As a result, 110 of 114 comparisons were within the 95% agreement limit. This shows good agreement between the two methods for the range of measurements
Huntingdon Life Sciences Ltd, Alconbury, Cambs, United Kingdom To date, respiratory measurements are typically obtained from conscious animals using a pneumotachograph attached to a face mask. However, this method requires restraint of the animals, restricts measurements to a relatively short time and recordings cannot be performed during inhalation administration of test substances. Respiratory Inductive Plethysmography (RIP) is reported to allow accurate measurement of ventilatory parameters in freely moving animals. The purpose of this study was to evaluate the data obtained from the noninvasive telemetry EMKABelt (jacket) RIP system to that obtained using the face mask and pneumotachograph system. Four beagle dogs implanted with DSI™ telemetry transmitters were habituated to EMKABelt jackets and face masks over 14 days. Preliminary respiratory recordings were obtained in order to evaluate the most appropriate restrained posture (standing or sitting) for
184
Abstracts
calibration of the EMKABelt system with the pneumotach/mask system. Respiratory recordings from both mask and RIP were obtained prior to and following CO2 (via a re-breath manoeuvre), Doxapram (5 mg/kg, i.v.) or inhaled Methacholine (19.3 μg/kg over 5 min). Cardiovascular parameters were monitored by telemetry during all procedures. The data obtained showed a high degree of correlation between the EMKABelt system and the pneumotach/mask system. The EMKABelt (jacket) system provides viable respiratory data and has the potential to be used on stand-alone safety pharmacology studies or as a functional end point on toxicology studies. doi:10.1016/j.vascn.2012.08.088
Comparison of surgical techniques for implanted telemetry monitoring of cardiorespiratory parameters in three species David S. Moddrelle, Kyle O'Donahue, Travis Denton, Eric Herrmann, Jill Dalton, David Gauvin, Theodore J. Baird MPI Research, Inc., Mattawan, MI, United States The use of telemetry for the collection of cardiovascular parameters is well established. While respiratory rate may be monitored continuously and for extended periods via diaphragmatic EMG or pleural pressure, tidal volume has not been as easily or reliably accessible. The present study was designed to evaluate surgical methods of an impedance technique for telemetric respiratory data collection in three commonly used species (canine, macaque, miniature swine). DSI PCT-R transmitters were implanted (n= 5/species) for acquisition of epicardial ECG, blood pressure, core body temp and respiration parameters. Left lateral thoracotomies were performed for the epicardial lead placements resulting in either a base/apex lead configuration or a modification of the procedure to accentuate p wave morphology. In the primate, the respiratory impedance leads were placed bilaterally in parallel with the xyphoid process and the iliac crest. For the dog and the Gottengen mini-pig the impedance leads were placed bilaterally in line with the xyphoid process and midway between the spine and the sternum. The position of the respiratory lead array was manipulated until an optimal impedance signal was captured. All animals recovered well without complications, with differences in the surgical approach for each species having no effect on signal quality data subsequently collected. Although there were some minor differences in lead placement, a very similar final orientation was successfully utilized for each species, in spite of apparent differences in mechanics characterizing the respiratory cycle. doi:10.1016/j.vascn.2012.08.089
A modified left thoracotomy approach for enhancing ECG P-wave detection in the cynomolgus monkey David S. Moddrelle, Jen Ward, Kyle O'Donohue, Theodore Baird MPI Research, Inc., Mattawan, MI, United States Epicardial placement of telemetry bio-potential leads has become widely accepted for high quality, noise free, chronic recording of base/apex electrocardiograms (ECGs). In multiple species, it has been shown that a complete ECG (PQRST) may be acquired via this method with R wave amplitudes ranging from 5 to 10 mV. However, in the primate, cardiac orientation (mean electrical axis) and absolute heart mass may contribute to difficulty in routinely acquiring a detectable P wave with this technique. Accordingly, we have developed a surgical procedure to optimize P wave amplitude. An off-midline laparotomy was performed to enable placement of the transmitter and pressure
catheter. The thoracotomy was performed to allow epicardial lead placement. Initially, the standard base/apex approach yielded a success rate of 65.1% (21/31) with 34.9% (10/31) of animals exhibiting either absent or low-amplitude P waves undetectable by software integration. Surgical modification of the epicardial placement was then performed by blunt dissection of tissues superior to the pericardium, without disrupting the mediastinum, until the right atrium could be visualized. At this point, the negative lead was iteratively placed in discrete locations until the ECG exhibited a visually and electronically discernable P wave. Following completion of the procedure, all animals recovered normally, with no post-surgical complications. This modification allowed for a 100% improvement on P wave detection acutely, with signal quality persisting for at least 12 months post-surgery.
doi:10.1016/j.vascn.2012.08.090
Assessment of the relationship between core body temperature and QT/QTc in the minipig using Dihydrocapsaicin Hai Ming Tanga, Martin Sandersa, Theodore Bairdc, Andrea Greiter-Wilkeb a
Hoffmann-La Roche Inc., Nutley, NJ, United States F Hoffmann-La Roche Ltd., Basel, Switzerland c MPI Research, Inc., Mattawan, MI, United States b
Background: Hypothermia has been linked to QTc prolongation both in clinic and animal species (e.g. dogs). However, the relation between core body temperature (BTc) and QTc interval in conscious pigs has not been determined. The purpose of this study was to evaluate such relationship in Göttingen minipigs to provide a context for evaluation of drug effects on electrocardiography (ECG) via hypothermia. Methods: Dihydrocapsaicin (DHC), a transient receptor potential vanilloid type 1 (TRPV1) agonist, was used to induce hypothermia via intravenous infusion. Five Göttingen minipigs (3 males and 2 females) were restrained in a sling prior to, during, and following the intravenous infusion of DHC via a vascular access port. Blood pressure, heart rate, BTc and ECG were monitored continuously during the course of the study using telemetry. Above parameters were recorded for 1 h prior to dosing, 4 h during intravenous infusion, and 1 h during the recovery period. The dose rate for DHC was set to 1.8 mg/kg/h, but was modulated such that it was maintained at 25% (0–30 min), 50% (30– 60 min), and 100% (2–4 h) of target infusion volume rate. Results: DHC induced a mean decrease in BTc of approximately 2.5 °C (38.5 to 36 °C) over 3.5 h. BTc immediately began to recover upon termination of the DHC infusion and returned to baseline within 1 h. The hypothermia was accompanied by QTc interval increases in all animals and the average increase in QTc interval was 18 ms with one degree (°C) of decrease in BTc. Conclusion: As also reported for various species including canines and humans, there exists an inverse relation between BTc and QTc in conscious Göttingen minipigs. On average, the change in QTc with per °C decrease in BTc was approximately 18 ms over the range of BTc obtained in the present study. When evaluated over a 24 h period in a group of vehicle-control minipigs (n = 34) in a different study, a similar inverse relation between BTc and QTc of approximately 15– 18 ms per °C decrease was found. The results from the present study are consistent with these historic data for Gottingen minipigs and suggest that an individual temperature correction factor should be applied to the QTc interval in cases of BTc changes when using this species in cardiovascular Safety Pharmacology studies.
doi:10.1016/j.vascn.2012.08.091
Comparison of cardiac electrophysiological and mechanical effects of torsadogens in the isolated normal and failing rabbit hearts Anusak Kijtawornrata, Suwanakiet Sawangkoona, Carlos Del Riob, Robert L. Hamlinc
183
that are considered. The increase in respiration rate by drug B was identified using both methods. It is concluded that respiration rate can be assessed using HRV analysis from ECG obtained in dog telemetry studies.
a
Department of Physiology, Faculty of Veterinary Science, Chulalongkorn University, Bangkok, Thailand b QTest Labs, LLC. Columbus, OH, United States c Department of Veterinary Biosciences, The Ohio State University and QTest Labs, Columbus, OH, United States Lengthening of QTc is the usual signal to indicate torsadogenic potential of therapeutic agent. However from experience with pentobarbital and amiodarone, both of which lengthen QTc dramatically but seldom produce torsades de pointes (TdP), it is clear that QTc—or even IC50 for hERG physiology—is not a perfect predictor. Thus this feasibility study was conducted to determine if known torsadogens (cisapride, dofetilide, and quinidine), might actually produce TdP in Langendorff preparation of a failing heart compared with normal healthy heart. Heart failure was induced by ligation of LAD and descending branch of LC coronary arteries. After one month of coronary artery ligation, all rabbits were anesthetized with ketamine/xylazine, the hearts were removed quickly, and they were perfused with normal Krebs solution in a Langendorff preparation to which escalating concentrations of torsadogens were added. RR, QT, and QTc(F) were longer, at rest, for failing hearts than for normals. In response to all three torsadogens, RR, QT and QTc lengthened similarly in a dose–response manner in both the failing and normal hearts. Neither the failing nor the normal hearts developed TdP. Compared to normal hearts, the failing isolated perfused heart produced clear differences in electrophysiological and mechanical properties. Langendorff-perfused hearts from rabbits with failing hearts (i.e., with already prolonged QTc), appear to develop less lengthening of RR, QT, and QTc than in normals. Langendorff preparations of failing hearts do not appear to be more permissive to developing TdP.
doi:10.1016/j.vascn.2012.08.085
doi:10.1016/j.vascn.2012.08.086
Effects of autonomic interventions on heart rate variability in ambulatory, telemetrized dogs Susan R. Arthur, Brenda L. Lehman, Jun Cao, James K. Hennan Bristol-Myers Squibb, Princeton, NJ, United States Clinical evidence demonstrates the importance of the autonomic nervous system (ANS) in triggering and/or sustaining ventricular arrhythmias. Sympathetic stimulation may reduce ventricular refractory period and fibrillation threshold, enhancing automaticity and promoting arrhythmia, while vagal stimulation prolongs refractoriness, reducing automaticity. Heart rate variability (HRV) evaluation utilizing time (T) and frequency (F) domain analyses may be used to assess drug-related effects on the ANS. Cardiovascular data were evaluated in 4 chronically instrumented telemetrized dogs before and after single autonomic blockade (30 min IV infusions) with atropine (competitive muscarinic antagonist, 20 mg/kg), or propranolol (non- selective ßadrenergic antagonist, 1 mg/kg), and the two combined, as compared to 0.9% saline vehicle. Beat-to-beat variability was assessed via Kubios HRV©. Data were expressed in 30- and 60-min periods. Atropine alone or with propranolol decreased RR and T variables (SDNN, RMSS and NN50%) for 2.5 h compared to vehicle infusion. Low F increased for 1.5 h, High F decreased for 1 h, and LF/HF increased during the 2nd 30-min period postdose. Propranolol alone had minimal effect on T and F variables but HR declined over 1.5 h. Atropine and propranolol together minimized negative inotropic effects and abolished chronotropic effects observed with propranolol alone. Parasympathetic inhibition (atropine) had greater effects on HRV with minimal effect from sympathetic blockade. Parasympathetic/vagal tone contributes more significantly to HRV in the dog.
Respiration rate derived from ECG in dogs Rikard Pehrson, Aliaksandr Bulhak
doi:10.1016/j.vascn.2012.08.087
AstraZeneca, Södertälje, Sweden
Evaluation of Respiratory Inductive Plethysmography using the EMKABelt (Jacket) system in the conscious beagle dog Stuart Purbrick, Stephen Jordan, Simon Moore, David Butler, Adam French, Deborah Jones, Emma Peake, Victoria Milner, Peter Davies, Ken Meecham
The heart rhythm in dogs displays sinus arrhythmia mainly due to respiration. This arrhythmia can be studied using software that transforms ECG RR intervals into frequency/variability relationship (i.e. heart rate variability—HRV). We investigated if ECG RR intervals could be used as a surrogate marker for respiration rate. Respiration rate, measured by face mask, was compared to the results obtained from HRV sinus arrhythmia. Twelve male beagle dogs were used. ECG was measured by means of telemetry (DataSci). Data was obtained from prior to dosing and up to 1 h after dosing, from three studies. Study I: vehicle or drug M given intravenously, study II: vehicle or drug A (3 doses) and study III: vehicle or drug B (3 doses) (both dosed by inhalation). Respiration rate was measured in 5-minute sections using the mask, and ECG RR intervals were obtained from the same period and analysed (http:// kubios.uku.fi/) and for each segment the frequency (above 0.15 Hz) with the top variability was extracted. The two methods were compared statistically using the Bland and Altman method for assessing agreement between methods. As a result, 110 of 114 comparisons were within the 95% agreement limit. This shows good agreement between the two methods for the range of measurements
Huntingdon Life Sciences Ltd, Alconbury, Cambs, United Kingdom To date, respiratory measurements are typically obtained from conscious animals using a pneumotachograph attached to a face mask. However, this method requires restraint of the animals, restricts measurements to a relatively short time and recordings cannot be performed during inhalation administration of test substances. Respiratory Inductive Plethysmography (RIP) is reported to allow accurate measurement of ventilatory parameters in freely moving animals. The purpose of this study was to evaluate the data obtained from the noninvasive telemetry EMKABelt (jacket) RIP system to that obtained using the face mask and pneumotachograph system. Four beagle dogs implanted with DSI™ telemetry transmitters were habituated to EMKABelt jackets and face masks over 14 days. Preliminary respiratory recordings were obtained in order to evaluate the most appropriate restrained posture (standing or sitting) for
184
Abstracts
calibration of the EMKABelt system with the pneumotach/mask system. Respiratory recordings from both mask and RIP were obtained prior to and following CO2 (via a re-breath manoeuvre), Doxapram (5 mg/kg, i.v.) or inhaled Methacholine (19.3 μg/kg over 5 min). Cardiovascular parameters were monitored by telemetry during all procedures. The data obtained showed a high degree of correlation between the EMKABelt system and the pneumotach/mask system. The EMKABelt (jacket) system provides viable respiratory data and has the potential to be used on stand-alone safety pharmacology studies or as a functional end point on toxicology studies. doi:10.1016/j.vascn.2012.08.088
Comparison of surgical techniques for implanted telemetry monitoring of cardiorespiratory parameters in three species David S. Moddrelle, Kyle O'Donahue, Travis Denton, Eric Herrmann, Jill Dalton, David Gauvin, Theodore J. Baird MPI Research, Inc., Mattawan, MI, United States The use of telemetry for the collection of cardiovascular parameters is well established. While respiratory rate may be monitored continuously and for extended periods via diaphragmatic EMG or pleural pressure, tidal volume has not been as easily or reliably accessible. The present study was designed to evaluate surgical methods of an impedance technique for telemetric respiratory data collection in three commonly used species (canine, macaque, miniature swine). DSI PCT-R transmitters were implanted (n= 5/species) for acquisition of epicardial ECG, blood pressure, core body temp and respiration parameters. Left lateral thoracotomies were performed for the epicardial lead placements resulting in either a base/apex lead configuration or a modification of the procedure to accentuate p wave morphology. In the primate, the respiratory impedance leads were placed bilaterally in parallel with the xyphoid process and the iliac crest. For the dog and the Gottengen mini-pig the impedance leads were placed bilaterally in line with the xyphoid process and midway between the spine and the sternum. The position of the respiratory lead array was manipulated until an optimal impedance signal was captured. All animals recovered well without complications, with differences in the surgical approach for each species having no effect on signal quality data subsequently collected. Although there were some minor differences in lead placement, a very similar final orientation was successfully utilized for each species, in spite of apparent differences in mechanics characterizing the respiratory cycle. doi:10.1016/j.vascn.2012.08.089
A modified left thoracotomy approach for enhancing ECG P-wave detection in the cynomolgus monkey David S. Moddrelle, Jen Ward, Kyle O'Donohue, Theodore Baird MPI Research, Inc., Mattawan, MI, United States Epicardial placement of telemetry bio-potential leads has become widely accepted for high quality, noise free, chronic recording of base/apex electrocardiograms (ECGs). In multiple species, it has been shown that a complete ECG (PQRST) may be acquired via this method with R wave amplitudes ranging from 5 to 10 mV. However, in the primate, cardiac orientation (mean electrical axis) and absolute heart mass may contribute to difficulty in routinely acquiring a detectable P wave with this technique. Accordingly, we have developed a surgical procedure to optimize P wave amplitude. An off-midline laparotomy was performed to enable placement of the transmitter and pressure
catheter. The thoracotomy was performed to allow epicardial lead placement. Initially, the standard base/apex approach yielded a success rate of 65.1% (21/31) with 34.9% (10/31) of animals exhibiting either absent or low-amplitude P waves undetectable by software integration. Surgical modification of the epicardial placement was then performed by blunt dissection of tissues superior to the pericardium, without disrupting the mediastinum, until the right atrium could be visualized. At this point, the negative lead was iteratively placed in discrete locations until the ECG exhibited a visually and electronically discernable P wave. Following completion of the procedure, all animals recovered normally, with no post-surgical complications. This modification allowed for a 100% improvement on P wave detection acutely, with signal quality persisting for at least 12 months post-surgery.
doi:10.1016/j.vascn.2012.08.090
Assessment of the relationship between core body temperature and QT/QTc in the minipig using Dihydrocapsaicin Hai Ming Tanga, Martin Sandersa, Theodore Bairdc, Andrea Greiter-Wilkeb a
Hoffmann-La Roche Inc., Nutley, NJ, United States F Hoffmann-La Roche Ltd., Basel, Switzerland c MPI Research, Inc., Mattawan, MI, United States b
Background: Hypothermia has been linked to QTc prolongation both in clinic and animal species (e.g. dogs). However, the relation between core body temperature (BTc) and QTc interval in conscious pigs has not been determined. The purpose of this study was to evaluate such relationship in Göttingen minipigs to provide a context for evaluation of drug effects on electrocardiography (ECG) via hypothermia. Methods: Dihydrocapsaicin (DHC), a transient receptor potential vanilloid type 1 (TRPV1) agonist, was used to induce hypothermia via intravenous infusion. Five Göttingen minipigs (3 males and 2 females) were restrained in a sling prior to, during, and following the intravenous infusion of DHC via a vascular access port. Blood pressure, heart rate, BTc and ECG were monitored continuously during the course of the study using telemetry. Above parameters were recorded for 1 h prior to dosing, 4 h during intravenous infusion, and 1 h during the recovery period. The dose rate for DHC was set to 1.8 mg/kg/h, but was modulated such that it was maintained at 25% (0–30 min), 50% (30– 60 min), and 100% (2–4 h) of target infusion volume rate. Results: DHC induced a mean decrease in BTc of approximately 2.5 °C (38.5 to 36 °C) over 3.5 h. BTc immediately began to recover upon termination of the DHC infusion and returned to baseline within 1 h. The hypothermia was accompanied by QTc interval increases in all animals and the average increase in QTc interval was 18 ms with one degree (°C) of decrease in BTc. Conclusion: As also reported for various species including canines and humans, there exists an inverse relation between BTc and QTc in conscious Göttingen minipigs. On average, the change in QTc with per °C decrease in BTc was approximately 18 ms over the range of BTc obtained in the present study. When evaluated over a 24 h period in a group of vehicle-control minipigs (n = 34) in a different study, a similar inverse relation between BTc and QTc of approximately 15– 18 ms per °C decrease was found. The results from the present study are consistent with these historic data for Gottingen minipigs and suggest that an individual temperature correction factor should be applied to the QTc interval in cases of BTc changes when using this species in cardiovascular Safety Pharmacology studies.
doi:10.1016/j.vascn.2012.08.091