Evaluation of a novel ECG lead placement method in telemetered freely moving cynomolgus monkeys: assessment of an intravascular biopotential lead.

INTRODUCTION: ECG is considered as a critical biomarker of cardiac safety pharmacology. ECG signal quality is essential for accurate interval quantification and automated arrhythmia detection. METHODS: We evaluated ECG signal quality over a 6 month period from 15 cynomolgus monkeys with radiotelemetry transmitters using biopotential leads where the negative lead was inserted in the jugular vein and advanced to the superior vena cava (intravascular lead) and the positive lead was placed on the diaphragm at the apex of the heart (diaphragmatic lead). Signal noise and signal-to-noise ratio from this implantation methodology were compared with signals obtained from animals with subcutaneous ECG lead. Macroscopic pathology and histopathology associated with the intravascular lead were evaluated at 6 months post-implantation in six monkeys. RESULTS: The ECG morphology obtained with the intravascular/diaphragmatic lead placement was comparable to conventional subcutaneous ECG (emulating Lead II) but presented higher amplitudes (P-wave +50.0%; R-wave +30.0%). Signal noise showed a circadian cycle of changes in magnitude for subcutaneous ECG leads that was not observed with this method. The intravascular/diaphragmatic lead placement presented a higher signal-to-noise ratio than subcutaneous ECG leads. No macroscopic abnormality was observed to be associated with the intravascular lead. Mild thickening of the intima/subintima with mild intimal proliferation of the cranial vena cava surrounding the intravascular lead were noted at histopathological examination. DISCUSSION: The intravascular/diaphragmatic ECG lead placement in cynomolgus monkeys provided reduced signal noise and elevated P-QRS-T amplitudes. The intravascular lead was well tolerated and appeared suitable for chronically instrumented cardiovascular safety pharmacology studies. Further assessments would be warranted to evaluate the potential of this methodology in other species.

Combined cardiopulmonary assessments with implantable telemetry device in conscious freely moving cynomolgus monkeys.

Female cynomolgus monkeys were surgically implanted with telemetry transmitters recording ECG (DII), arterial pressure, physical activity, body temperature, and tidal volume. Respiratory rate (RR) and tidal volume (TV) were monitored simultaneously with the telemetry transmitter using impedance. Impedance-based monitoring of RR and TV by telemetry correlated with controlled TV and with pneumotachometer (>98%) in restrained animals. Control drugs with cardiovascular and respiratory effects, including saline, medetomidine (0.01, 0.02 and 0.04mg/kg) and cocaine (0.5, 1.0 and 1.5mg/kg) were administered intravenously. An averaging epoch of 5min was used for analysis of respiratory data. Medetomidine induced significant respiratory depression with decrease in RR and TV in freely moving animals while cocaine increased TV, RR and minute ventilation (MV) with concomitant increase in heart rate when compared with time matched values from saline-treated animals. The onset, duration and magnitude of cardiovascular and respiratory changes were correlated. This highlights the dependency of the cardiovascular and respiratory systems. The use of cardiopulmonary monitoring can allow continuous monitoring including during night time when variability of respiratory parameters is lower. Monitoring of cardiovascular and respiratory parameters in the same animals could also help to decrease the number of animals used in research.

Relationships among self-efficacy, outcome expectancy, and postoperative behaviors in total joint replacement patients.

PURPOSE: To determine whether self-efficacy and outcome expectancy predicted performance of postoperative leg exercises and ambulation among persons recovering from total hip or total knee replacement. DESIGN: Descriptive correlational. SAMPLE: 50 subjects recovering from their first unilateral total hip or total knee replacement at a large midwestern hospital who had completed a preoperative education course. METHODS: On postoperative day 1, subjects who correctly performed leg exercises and could properly ambulate with a walker were administered the Self-Efficacy Scale and the Outcome Expectancy Scale. On postoperative day 2, frequency and repetitions of leg exercises were measured by self-report. Ambulation was measured by distance walked in feet. FINDINGS: Self-efficacy was the sole predictor of the dependent variables, accounting for 8% to 33% of the variance. Higher levels of self-efficacy were correlated with longer distances in ambulation and with higher frequency and more repetitions of leg exercises. IMPLICATIONS FOR NURSING PRACTICE: Solely providing a preoperative education course is not sufficient to ensure performance of postoperative behaviors in total joint replacement patients. Patients' self-efficacy beliefs may need to be considered when planning a preoperative educational program for patients undergoing total joint replacement surgery. This study's situation-specific measure of self-efficacy could be used in the clinical setting to identify patients with low levels of self-efficacy who may be less likely to perform preventive postoperative behaviors.

Nine months in space: effects on human autonomic cardiovascular regulation.

We studied three Russian cosmonauts to better understand how long-term exposure to microgravity affects autonomic cardiovascular control. We recorded the electrocardiogram, finger photoplethysmographic pressure, and respiratory flow before, during, and after two 9-mo missions to the Russian space station Mir. Measurements were made during four modes of breathing: 1) uncontrolled spontaneous breathing; 2) stepwise breathing at six different frequencies; 3) fixed-frequency breathing; and 4) random-frequency breathing. R wave-to-R wave (R-R) interval standard deviations decreased in all and respiratory frequency R-R interval spectral power decreased in two cosmonauts in space. Two weeks after the cosmonauts returned to Earth, R-R interval spectral power was decreased, and systolic pressure spectral power was increased in all. The transfer function between systolic pressures and R-R intervals was reduced in-flight, was reduced further the day after landing, and had not returned to preflight levels by 14 days after landing. Our results suggest that long-duration spaceflight reduces vagal-cardiac nerve traffic and decreases vagal baroreflex gain and that these changes may persist as long as 2 wk after return to Earth.

Increased incidence of adenocarcinoma of uterine cervix.

A greater than expected incidence of adenocaricinoma of the uterine cervix is reported. Among 41 cases of cervical carcinoma, 14 (34%) were adenocarcinoma. Clinicopathologic data for these cases are summarized. Eleven of the 14 cases were pure adenocarcinomas; 3 were mixed adenosquamous carcinoma. The value of cytopathology is demonstrated in the 7 of 9 pretreatment cervical cytologies whereby adenocarcinoma was indicated (an accuracy rate of 78%). The other 2 revealed abnormal cells in which malignancy was a possibility. Three cases clinically were initially considered endometrial adenocarcinoma, but by our classification criteria, including Alcian blue staining for cervical mucin content of acid mucopolysaccharide, they were more specifically identified as primary endocervical in origin.