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PubMed2006

Neurophysiological recordings in freely moving monkeys.

Recordings of neuronal activity in freely moving rats are common in experiments where electrical signals are transmitted using cables. Such techniques are not common in monkeys because their prehensile abilities are thought to preclude such techniques. However, analysis of brain mechanisms underlying spatial navigation and cognition require the subject to walk. We have developed techniques for recordings in freely moving monkeys in two different situations: a 5 x 5 m testing laboratory and in a 50 m2 open field environment. Neuronal signals are sent to amplifiers and data acquisition systems using cables or telemetry. These techniques provide high quality recordings of single neurons during behaviors such as foraging, walking, and the performance of memory tasks and thus provide a unique opportunity to study primate behavior in a semi-natural situation.

Animals↗

PubMed1998

Changes in pacing lead impedance over time predict lead failure.

It has been suggested that a decrease in lead impedance may predict pacing lead failure, but there is limited prospective data about the relation of changes in lead impedance over time to lead performance. We monitored changes in lead impedance through implantable pulse generators with real-time telemetry data capability in 105 patients with Medtronic 4012 leads (n = 38) and Medtronic 4004 leads (n = 67). Pacing lead failure was documented by serial ambulatory electrocardiographic monitoring or intensified pacemaker clinic surveillance. A significant decrease in lead impedance was observed in patients with Medtronic 4012 and Medtronic 4004 leads with documented lead failure, whereas lead impedance remained stable over time in patients without documented lead failure. The sensitivity and specificity of a lead impedance decrease of > or =15% to predict lead failure were 69% and 70%, respectively. The sensitivity and specificity of a lead impedance decrease of > or =30% to predict lead failure were 36% and 90%, respectively. The positive and negative predictive values for a lead impedance decrease of > or =15% were 54% and 81%, respectively, and for a lead impedance decrease of > or = 30% were 65% and 73%, respectively. Thus, small decreases in lead impedance may identify failing leads. Serial measurement of pacing lead impedance over time is a useful tool to monitor pacing lead performance.

Aged↗

PubMed1999

Taking advantage of sophisticated pacemaker diagnostics.

The ever-increasing complexity of pacing systems, combined with functions that vary from one manufacturer to another, can pose challenges during analysis of device function. Standard pacemaker diagnostics are measured data, electrogram telemetry, maker annotations and event counters, albeit with their current limitations. New diagnostic features discussed include time-based diagnostics, histograms of sensed amplitudes, pacing thresholds, or impedance trending. Mode-switching algorithms, combined with diagnostic features, facilitate the use of dual-chamber devices in patients with paroxysmal atrial tachyarrhythmias. The introduction of electrogram storage into pacemakers further improves diagnostic capabilities and allows a permanent validation and optimization of diagnostic and therapeutic algorithms. External diagnostic devices, which provide Holter recordings with continuous marker annotations and patient-triggered diagnostics, are additional features that will become increasingly important.

Arrhythmias, Cardiac↗

PubMed1999

Future of bradyarrhythmia therapy systems: automaticity.

Since the first fixed-rate ventricular pacemaker was introduced in the late 1950s, pacing systems have evolved rapidly. Current developments focus on making devices more sophisticated and less complex--a challenging combination. Automaticity features such as beat-by-beat capture verification, sensitivity threshold adaptation, and algorithms to govern dynamically the maximum sensor rate have either recently been introduced or are likely to be introduced in the near future. Technologic advances are likely to allow meaningful improvements in current drain, battery performance, memory capacity, signal processing, telemetry, and programmer interface. Bradyarrhythmia therapy devices of the future promise to go beyond the pacemaker. Ultimately, pacing systems will become part of integrated cardiac rhythm management systems.

Bradycardia↗

PubMed2000

Comparison of troponin T versus creatine kinase-MB in suspected acute coronary syndromes.

Limitations of creatine kinase-MB (CK-MB) have led to alternative biochemical markers, including troponin T (TnT), to detect myocardial necrosis. Limited data are available regarding the predictive value of this new marker in patients with chest pain of uncertain etiology. Therefore, we prospectively compared CK-MB and TnT in a broad population with suspected acute coronary syndromes, including those admitted to a short-stay chest pain unit. CK-MB, quantitative TnT levels, and a rapid bedside assay were performed at 0, 4, 8, and 16 hours. Adverse events, including infarction, recurrent ischemia, coronary surgery, need for catheterization and/or intervention, stroke, congestive heart failure, or death, were identified by chart review and by follow-up phone call at 6 months. Of 707 patients, 104 were excluded for creatinine >2 mg/dl or incomplete data, leaving a total cohort of 603 patients. Coronary Care Unit admissions were 18%, intermediate care admissions were 14%, telemetry admissions is 21%, and admissions to 24-hour short-stay area were 47%. TnT (at 0.1 ng/ml) and CK-MB were positive in a similar proportion of patients (20.4% and 19.7%, respectively); however, the patients identified by TnT and CK-MB were not identical. In-hospital adverse events occurred in 37.1% with no differences in positive predictive value for the markers (p = NS). If CK-MB and TnT were negative, the early adverse event rate was 27%. No cardiac marker was positive by 16 hours in 54.9% of patients with an adverse event. Six-month follow-up was obtained in 576 of the 603 patients (95.5%). One hundred fifty-five late adverse events occurred in 134 patients (23.3%) at an average of 3.3+/-2.5 months after discharge. If both markers were negative, the late event rate was 20.2% and did not increase in patients with positive CK-MB or TnT >0.2 ng/ml. However, the late event rate was substantially higher (52.9%) in those with intermediate TnT levels of 0.1 to 0.2 ng/ml (p = 0.002). Thus, TnT is a suitable alternative to CK-MB in patients with suspected acute coronary syndromes. The rapid bedside assay is comparable to quantitative TnT and may enable early diagnosis and triage. A negative cardiac marker value (TnT or CK-MB) does not necessarily confer a low risk of complication in patients presenting with acute chest pain to an emergency department.

Adult↗

PubMed1990

Blood pressure measured telemetrically from home throughout pregnancy.

Sixty-eight healthy pregnant women measured their blood pressure at home for 1 day every 4 weeks from 14 weeks' gestation until delivery. Blood pressure measurements were made with the Cambridge blood pressure telemetry system, which was composed of a Dinamap 1846 monitor linked to and controlled by a dedicated microprocessor which communicated transtelephonically with a hospital-based microcomputer. On each measurement day each woman measured her blood pressure five times: on first rising and then at 10 AM, 2 PM, 6 PM and 10 PM. At each measurement session the blood pressure was automatically taken 10 times at 1-minute intervals. A total of 23,790 individual blood pressure measurements were analyzed. Systolic, diastolic, and mean arterial blood pressures were lowest at 18 weeks' gestation, rising slowly thereafter at a rate of 0.4 mm Hg systolic and 0.2 mm Hg diastolic per week. The maternal pulse rate also increased steadily after 18 weeks at a rate of 0.25 beats/min per week. There was a strong correlation between the blood pressures at 18, 26, and 38 weeks. All blood pressure parameters were significantly lower on first rising than at other times of the day, although the differences were small: 5 mm Hg for systolic, 4 mm Hg for mean arterial, and 3 mm Hg for diastolic blood pressure. After 10 AM, however, there was no significant daytime variation in any blood pressure parameter, indicating that for most purposes the time of day at which pressure measurements are made is unimportant.

Adult↗

PubMed1987

The effects of maternal ambulation on the nonstress test.

Using a recently developed noninvasive telemetry device (model 8240A, Hewlett-Packard Co., Palo Alto, California), we studied, under controlled conditions, the effects of maternal ambulation on the nonstress test patterns of 100 near-term high-risk pregnancies, randomly divided into two equal groups who underwent three alternating 30-minute periods of ambulation and bed rest, beginning either with ambulation (group 1) or bed rest (group 2). Fetal heart rate data were captured and analyzed by a programmed microcomputer for group mean 30-minute fetal heart rate baseline rates and variability and incidences and dimensions of fetal heart rate accelerations and decelerations. Both groups were similar for the maternal and perinatal data examined. The fetal heart rate parameters analyzed were similar within and between each group during each 30-minute testing segment. No episodes of sustained tachycardia or bradycardia were observed. Although 13 fetuses in each group exhibited variable or late decelerations, the incidence of decelerations was no different during periods of rest or ambulation. Maternal ambulation does not elicit abnormal fetal heart rate responses in most high-risk fetuses and may be an acceptable alternative to conventional nonstress test conditions.

Female↗

PubMed1998

Daily noninvasive rejection monitoring improves long-term survival in pediatric heart transplantation.

BACKGROUND: Acute rejection episodes and transplant vasculopathy (TVP) account for most of the late deaths after heart transplantation in both adults and children. Accumulating evidence indicates that fatal acute rejection and TVP are related to unrecognized and untreated early and ongoing acute rejection. Day-by-day surveillance of the heart and prompt treatment of any rejection may yield improved long-term survival. METHODS: In almost all patients having transplantation at our institution (978 patients since 1986), the intramyocardial electrogram (IMEG) was recorded routinely every day through a telemetry pacemaker and transmitted to our center by telephone modem. Earlier studies showed a substantial voltage drop in the IMEG QRS complex is highly indicative of acute rejection, including humoral rejection. In this study, we reviewed the data from 69 pediatric patients up to 16 years old for the incidence of acute rejection, TVP, and long-term outcome. Diagnostic endomyocardial biopsies were performed in only 10 patients, and recent coronary angiograms from 29 children were reviewed. RESULTS: In 50 children discharged after heart transplantation, IMEG surveillance data for a mean of 2.9 years indicated 72 acute rejection episodes. During follow-up of 1 month to 10.5 years (mean follow-up, 4.4 years), 2 patients died late of causes unrelated to either rejection or TVP. Another patient died of rejection during unrecognized underimmunosuppression nearly 8 years after transplantation and nearly 31/2 years after discontinuing IMEG recordings. Two patients without IMEG recording died of acute rejection or late TVP. In 1 patient, moderate TVP was seen on an angiogram after 41/2 years (incidence, 2.0%; 5-year incidence, 5.6%). CONCLUSIONS: Daily recording of the IMEG can reliably detect early stages of acute rejection episodes, and immediate rejection treatment seems to keep the incidence of TVP low. The IMEG appears better than all the other rejection monitoring protocols currently in use.

Acute Disease↗

PubMed2001

Corticotropin-releasing factor (CRF) or CRF binding-protein ligand inhibitor administration suppresses food intake in mice and elevates body temperature in rats.

Corticotropin-releasing factor (CRF) receptor agonist and CRF binding-protein (CRF-BP) ligand inhibitor peptides both activate CRF systems but exert very distinct functional profiles in animal models of arousal, energy balance and emotionality. The present studies were designed to extend the dissimilar efficacy profiles of central administration of a CRF agonist, r/h CRF(1-41), versus a CRF-BP ligand inhibitor, r/h CRF(6-33), into mouse and rat models of energy balance in order to further explore in vivo efficacy of these ligands in two separate animal species. In CD-1 mice, food intake was significantly attenuated 3 h after acute administration of CRF(1-41) (0.007-0.2 nmol), but not CRF(6-33). In obese Ob/Ob mice, both CRF(1-41) (0.007-0.2 nmol) and CRF(6-33) (0.02-2.3 nmol) significantly attenuated basal feeding over 3 h following acute peptide administration. In rats, CRF(1-41) (1 nmol) and CRF(6-33) (1.5-7.7 nmol) infusion significantly increased rectal temperature. In studies employing a telemetry apparatus, core temperature was also increased by CRF(1-41) (1 nmol) and CRF(6-33) (1.5 nmol), whereas only CRF(1-41) increased locomotor activity and heart rate. These results suggest that CRF receptor agonist administration is capable of producing a global profile of negative energy balance by reducing food intake in mice and increasing energy expenditure in rats. In contrast, CRF-BP ligand inhibitor administration appears to suppress food intake in a mouse strain selective manner and to elevate rectal and core temperature in rats without accompanying cardiovascular activation.

Amphetamine↗

PubMed2001

Electrophysiological parameters indicative of sudden cardiac death in the dog with chronic complete AV-block.

BACKGROUND: The dog model of chronic complete AV-block (CAVB) demonstrates a considerable incidence of (witnessed) sudden death (16/117 dogs). In this study we tried to: (1) elucidate the mechanisms of sudden death using an ECG telemetry device and (2) identify retrospectively the risk parameters indicative of this arrhythmogenic death. METHODS: Between 1994 and 1998, 78 anesthetized dogs underwent an extensive electrophysiological study including: (1) left- (LV) and right ventricular (RV) monophasic action potential (MAP) recordings to assess Delta MAPD (LV APD minus RV APD) and (2) pacing protocols (PES) to induce torsade de pointes arrhythmias (TdP) at 4--6 weeks CAVB. Eight animals experienced sudden cardiac death (SCD) during the follow-up period (mean 7+/-3 weeks CAVB). Since the response of the CAVB dog to class III drugs is not uniform we also made comparisons among the SCD group, TdP drug responders and non-responders. For this purpose we selected all animals which (1) received almokalant (n=15, 0.12 mg/kg/5 min) or ibutilide (n=9, 0.025 mg/kg/5 min) as an additional challenge to induce TdP and (2) had a follow-up period of at least 4 weeks. RESULTS: Six out of eight SCD dogs showed inducible TdP at baseline. Two of eight dogs had telemetric ECG surveillance and both revealed polymorphic VT as the cause of SCD. Baseline Delta MAPD of the SCD (90+/-15 ms) was significantly higher than the non-SCD group (n=70, 60+/-30 ms). Of the 24 dogs which received class III drugs, 12 belonged to the TdP responder group. Delta MAPD of the TdP responder group (80+/-15 ms) was similar to the SCD group and significantly higher compared to the non-responder group (n=12, 40+/-25 ms). QT-time and cycle length of idioventricular rhythm were not different. CONCLUSION: In the CAVB dog model, SCD is (1) most probably related to TdP while (2) inducible TdP and the measure of Delta MAPD at baseline indicate susceptibility to SCD.

Animals↗

PubMed1984

A computer system for analysis and transmission of spirometry waveforms using volume sampling.

A microprocessor-controlled data gathering system for telemetry and analysis of spirometry waveforms was implemented using a completely digital design. Spirometry waveforms were obtained from an optical shaft encoder attached to a rolling seal spirometer. Time intervals between 10-ml volume changes (volume sampling) were stored. The digital design eliminated problems of analog signal sampling. The system measured flows up to 12 liters/sec with 5% accuracy and volumes up to 10 liters with 1% accuracy. Transmission of 10 waveforms took about 3 min. Error detection assured that no data were lost or distorted during transmission. A pulmonary physician at the central hospital reviewed the volume-time and flow-volume waveforms and interpretations generated by the central computer before forwarding the results and consulting with the rural physician. This system is suitable for use in a major hospital, rural hospital, or small clinic because of the system's simplicity and small size.

Computers↗

PubMed2001

Loads acting in an intramedullary nail during fracture healing in the human femur.

The form and function of the musculo-skeletal system is closely related to the forces acting in its components. Significant forces are present in the long bones, but their magnitudes have so far only been estimated from mathematical models. Fracture fixation by means of metal implants provides an opportunity to measure the implant-born forces and to estimate the long bone forces before healing occurs. The load changes during fracture healing may provide additional information. Therefore, a telemetrized, interlocking femoral nail for wireless transmission of forces and moments acting across the fracture site was developed. The design was based on the geometry and material of a 16 mm AO nail with a circular, closed cross-section allowing full protection of the electronic circuits from the body fluids. After careful testing, it was implanted in a 33-year-old patient who had sustained a multifragmentary fracture of the left femur. Measurements at a rate of approx. 0.4 Hz were performed in different patient postures between the 2nd and 26th postoperative week. Significant axial forces and bending moments were measured during several activities such as sitting, unsupported leg elevation and partial weight bearing in a standing position. Forces orthogonal to the nail axis remained small. The reductions of the implant loads due to fracture consolidation were in the order of 50%. Dynamization of the nail did not change the forces. Even though the telemetry system did not allow for dynamic measurements and the results presented here provide data from one subject only, the new information will be useful with respect to implant design, biomechanics of fracture fixation and evaluation of healing progression.

Adult↗

PubMed1997

Relations between compressive axial forces in an instrumented massive femoral implant, ground reaction forces, and integrated electromyographs from vastus lateralis during various 'osteogenic' exercises.

A subject, who had undergone surgery to replace one hip joint and the proximal half of the femur with an instrumented titanium implant, performed brief exercises whilst simultaneous measurements were made of compressive axial force in the implant using short-range wireless telemetry, ground reactions using a Kistler force plate, and electromyographic activity of the vastus lateralis (VL) and erector spinae (ES) muscles using surface electrodes. Recordings were made barefoot and wearing 'trainers'. The exercises (slow jumping in counter movement style, fast continuous jumping, and jogging on the spot) have been found effective in controlled interventions for increasing bone mineral density in women. The implant forces were 250-400% BW. The values were about twice the magnitude of the ground reaction forces and significantly correlated with them for both peak force and its rate of rise but their relative magnitudes varied depending on mode of activity (jumping or jogging). Implant forces were significantly related to the muscle activity; in multiple regression analysis implant forces during take off from slow jumps VL contributed significantly in addition to the ground reaction (98% total explained variance). There was more activity in VL during jumping than jogging for the same implant force which may explain why jumping appears to be more osteogenic than jogging for the femur. For the same ground reaction, wearing trainers increased both the magnitude of the compressive loading of the femur and its rate of rise.

Analysis of Variance↗

PubMed1987

A unique teletransmission system for extended four-channel esophageal pH monitoring in infants and children.

A new computerized telemetry system for extended esophageal pH monitoring is prospectively evaluated and compared with other diagnostic modalities in 38 pediatric patients suspected of having gastroesophageal reflux (GER). Unique circuitry allows connection of 1.5 mm diameter antimony electrodes to a patient-worn digital recorder that continuously samples pH at four levels from pharynx to distal esophagus. Ambulatory studies in a "physiologic" environment are possible and data is teletransmitted by the satellite computer to the central laboratory for analysis. Of 41 studies completed, four were lost to interpretation because of battery, electrode, or computer failure. Thirty-seven studies could be analyzed in five clinical groups: emesis and failure to thrive; status post esophageal atresia repair; apnea/bradycardia; central nervous system damage; and status post antireflux procedure. Pathologic GER was noted 14 times and an antireflux procedure was clinically required in 13 instances. In five cases the upper GI series failed to detect the GER. Twenty-three studies showed no GER, and the clinical symptoms resolved with appropriate medical therapy in 21 cases. The upper GI series demonstrated GER five times in this group. In the nine instances that esophagoscopy/biopsy was employed, the pH study findings were uniformly confirmed. This computerized system provided a technically complete and interpretable study 90% of the time. Based on patient outcome, the extended pH monitoring was 92% accurate in detecting clinically important GER with a sensitivity of 87% and specificity of 93%. The upper GI series demonstrated a 69% accuracy with a 60% sensitivity and 64% specificity (P = .01).(ABSTRACT TRUNCATED AT 250 WORDS)

Child↗

PubMed2000

Effects of bilateral striatal 6-OHDA lesions on circadian rhythms in the rat: a radiotelemetric study.

The present work aims to document, in a previously described animal model of Parkinson (double bilateral striatal injection of 6-OHDA), the possible modifications of circadian markers rhythms i.e. temperature (T), heart rate (H) and locomotor activity (A) registered continuously by telemetry, in order to evaluate a possible perturbation of the circadian rythmicity. H, T and A were measured by radiotelemetry after surgical implantation of the transmitters (Data Sciences). After a recovery period, the study was divided into a control period (C) for baseline measurements of T, H and A daily rhythms. Then, the stereotaxic 6-OHDA striatal lesion was done to a group of 4 rats while the control rats were injected into striata with saline; a second period of four registration weeks was observed [D 1-7 (W1), D 8-14 (W2), D 15-21 (W3), D 22-28 (W4)]. Finally, at the end of this period the seven rats were decapited in order to determine their striatal dopamine (DA) content. Our data document that the circadian rhythms of H, T and A were differently affected according to time. Thus, a temporary loss of circadian periodicity was observed particularly for heart rate. 6-OHDA-induced modifications of H, T and A circadian rhythm characteristics were also observed: a significant decrease of the mesor was observed for the three rhythms as well as a phase advance. Concerning the amplitude of these rhythms, only H was significantly decreased. These perturbations were observed during the four weeks following the intervention, never reaching the initial control levels. Such observed perturbations would supply a basis for the future study of the chronopharmacology of antiparkinsonian drugs.

Animals↗

PubMed1998

Recording heart rate and blood pressure in rats during parabolic flight.

The way in which the cardiovascular system adapts to weightlessness is still under discussion. No data are yet available on the responses of rats during space flight, although this animal is commonly used in simulation studies. We have designed and tested a protocol to study the short term responses of the cardiovascular system to weightlessness during parabolic flight. A telemetry system was used to measure heart rate (HR) and blood pressure. It was possible to collect and record radio-signals without any interference. Microgravity caused a reduction in HR, an increase in mean arterial pressure (MAP, 7%), and a non-significant decrease in central venous pressure (CVP, 13%). The change in CVP was similar to the decrease observed in human space flight. This type of study may also be feasible for longer exposure of rats to microgravity (space flight).

Animals↗

PubMed1996

Long-term electroencephalographic monitoring for diagnosis and management of seizures.

Long-term electroencephalographic (EEG) monitoring is the process of recording an EEG for a prolonged period in order to document epileptic seizures or other episodic disturbances of neurologic function. Indications for long-term EEG monitoring include diagnosis of a seizure disorder (epilepsy), classification of seizure types in patients with epilepsy, and localization of the epileptogenic region of the brain. Methods used for long-term EEG monitoring include prolonged analog or digital EEG, prolonged analog or digital ambulatory EEG, and prolonged analog or digital video-EEG monitoring with telemetry. Each of these methods has distinct advantages and disadvantages, particularly relative to storage, retrieval, and manipulation of data. Long-term EEG monitoring is useful in the management of patients with epilepsy and in the diagnosis of a seizure disorder. For most patients, inpatient long-term EEG monitoring is best performed in a specialized epilepsy-monitoring unit, which can provide a safe environment and both educational and psychosocial support. The choice of the most appropriate method of long-term monitoring for a specific clinical situation is best made by an epileptologist or a neurologist at an epilepsy center.

Electroencephalography↗

PubMedDate not supplied

High dietary NaCl early in development enhances mean arterial pressure of adult rats.

We investigated the long-term influence of early dietary NaCl on adult mean arterial pressure (MAP) and heart rate (HR), assessed continuously for 7 weeks when fed water and chow containing 1% NaCl (weeks 1, 4, 7), 0% NaCl (weeks 2-3), and 3% NaCl (weeks 5-6) while on a 12:12 light/dark cycle. Subjects were offspring of female Sprague-Dawley rats fed solid chow consisting of either 0.1% (basal), 1% (intermediate), or 3% (high) NaCl throughout pregnancy and lactation. After weaning on postnatal day (PD) 21, offspring were fed the same NaCl diet of their mother until PD 30, at which time all offspring were given Purina 5001 diet (1% NaCl) as their solid chow. On PD 60, 22 adult male offspring (eight basals, six intermediates, eight highs) were implanted with an aortic electronic sensor for transmitting blood-pressure signals by telemetry. MAP and HR varied significantly across the 7-week testing period in association with dietary NaCl levels. The three perinatal salt groups had similar HR levels on normal 1% NaCl chow. However, HR increased in all groups during 0% NaCl and decreased in all groups during 3% NaCl. In contrast, the average MAP levels were significantly greater in the highs compared to both the intermediate and basal groups during both dark and light periods. MAP increased in high and basal groups during both 0% and 3%; however, the increase was more pronounced in the highs. In conclusion, exposure to high levels of dietary NaCl early in development led to a persistent increase in MAP in adulthood.

Animals↗