Respiratory Rates Derived From Arterial Blood Pressure Waveforms in Telemetered Dogs.

The objective of this study was to extract low frequency respiratory "artifacts" from a standard arterial blood pressure (ABP) waveform to simultaneously derive reliable breathing rates (BR). Arterial blood pressure derived BR values were characterized against respiratory rates simultaneously obtained from the Respiratory Inductive Plethysmography (RIP) system (EMKA). Reference compounds were introduced to evaluate responsiveness of the derived measures to respiratory depressants and stimulants. Male beagle dogs (n = 3) were instrumented with minimally invasive telemetry devices for measurements of ABP and heart rate. The RIP system was utilized simultaneously to collect respiratory rate, tidal volume, and minute volume of each animal following pharmacological challenges. Early results revealed the derived BR's from ABP waveforms did not correlate well with those measured from the RIP system. Post study X-ray visualization revealed suboptimal catheter positioning, causing poor concordance of BR tallied from the ABP waveforms. Follow-up evaluations were conducted using additional animals instrumented with the ABP catheter tip placement advanced proximal to the thoracic diaphragm. Preliminary data from this subset of animals significantly improved the correlation of BR derived from ABP and respiratory rates recorded by the RIP. This proof of concept investigation was intended to evaluate an algorithm designed to extract additional data from routine cardiac waveforms. We clearly demonstrated that with optimal blood pressure catheter placement and acquisition algorithm, a reliable breathing rate can also be extracted from safety studies without the need for additional studies/animals to capture those respiratory end points.

The incidence of spontaneous arrhythmias in telemetered beagle dogs, Göttingen Minipigs and Cynomolgus non-human primates: A HESI consortium retrospective analysis.

INTRODUCTION: Characterization of the incidence of spontaneous arrhythmias to identify possible drug-related effects is often an important part of the analysis in safety pharmacology studies using telemetry. METHODS: A retrospective analysis in non-clinical species with and without telemetry transmitters was conducted. Electrocardiograms (24 h) from male and female beagle dogs (n = 131), Göttingen minipigs (n = 108) and cynomolgus non-human primates (NHP; n = 78) were analyzed. RESULTS: Ventricular tachycardia (VT) was observed in 3% of the dogs but was absent in minipigs and NHPs. Ventricular fibrillation (VF) was not observed in the 3 species. Ventricular premature beats (VPBs) were more frequent during daytime and atrioventricular blocks (AVBs) were more frequent at night in all species. A limited number of animals exhibited a high arrhythmia frequency and there was no correlation between animals with higher frequency of an arrhythmia type and the frequency of other arrythmias in the same animals. Clinical chemistry or hematology parameters were not different with or without telemetry devices. NHP with a transmural left ventricular pressure (LVP) catheter exhibited a greater incidence of VPBs and PJCs compared to telemetry animals without LVP. DISCUSSION: All species were similar with regards to the frequency of ventricular ectopic beats (26-46%) while the dog seemed to have more frequent junctional complexes and AVB compared to NHP and minipigs. Arrhythmia screening may be considered during pre-study evaluations, to exclude animals with abnormally high arrhythmia incidence.

Translational assessment of cardiac contractility by echocardiography in the telemetered rat.

INTRODUCTION: Cardiac contractility was evaluated using standard inotropic agents in rats. We compared indices of cardiac contractility, i.e. LV dP/dt max from telemetry while simultaneously collecting EF (ejection fraction) and FS (fractional shortening) measures from echocardiography. METHODS: Male Wistar rats were instrumented with telemetry devices for measurements of blood pressure and left ventricular pressure. Milrinone (PDE III inhibitor) and verapamil (L-type calcium channel blocker) at doses of 0, 3, 10, and 30 mg/kg were administered orally using a 4 × 4 Latin square crossover study design. Telemetry data were recorded at predose and continuously for 24h post-dose. Echocardiographic evaluations were conducted once at predose and at 1 and 2h after milrinone or verapamil administration, respectively. During the recording of echocardiograms, telemetry data were collected simultaneously. Blood samples were also collected to confirm plasma drug exposure. RESULTS: As expected, milrinone increased LV dP/dt max, EF and FS while verapamil decreased LV dP/dt max, EF and FS. Linear regression analysis showed a positive correlation between LV dP/dt max and EF or FS (P<0.001) with both test agents. A change in LV dP/dt max of 1000 mmHg/s was found to correspond with a change in EF and FS of 13 and 16%, respectively, in the telemetered rat. DISCUSSION: The correlation between contractility indices assessed by telemetry and echocardiographic methods in rat models has not received much attention to date. Our results with two reference compounds demonstrate that both methods are sensitive to alterations in contractility induced by inotropic agents administered to rats. The high degree of correlation between changes in LV dP/dt max and EF or FS in the rat enables a translational-element of clinical relevance following changes in contractility indices when measured with telemetry devices in preclinical studies.