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Biomedical subjects

C W Israel

Publications and source records attributed to C W Israel.

At least 19 recordsLinked to original sources
PubMed1999

Influence of the pacing rate on the atrioventricular conduction time during aerobic and anaerobic exercise: basic concepts for a dromotropically controlled rate responsive pacemaker.

The dromotropic pacemaker concept needs a rate responsive algorithm in which the pacing rate is controlled by the atrioventricular conduction time (AVCT). To develop basic concepts for such a rate responsive algorithm, the influence of the pacing rate on the AVCT was investigated. Seven patients (62 +/- 7.8 years) with sick sinus syndrome and intact atrioventricular conduction underwent two cardiopulmonary exercise tests (CPX) on a treadmill. According to the determination of the anaerobic threshold (AT) and the patients maximum capacity in the first incremental CPX the work rate for two exercise levels below and above the AT were chosen for the second constant workload CPX. The calculation of the optimal pacing rate (HRopt) was based on the oxygen uptake (VO2) during exercise after reaching steady-state conditions. According to the increase of the VO2 from 14.8 +/- 2.3 mL/min per kilogram during aerobic work (38.3 +/- 16.0 W) to 19.4 +/- 4.7 mL/min per kilogram during anaerobic work (80.6 +/- 32.3 W), the HRopt was calculated to be 98.6 +/- 6.9 beats/min and 116.4 +/- 4.7 beats/min. Starting from HRopt, the pacing rate was increased (overpacing) and decreased (underpacing) by about 5 beats/min every minute. At optimal pacing rate the AVCT decreased significantly from 233.0 +/- 30.5 ms during aerobic work and to 226.4 +/- 27.3 ms during anaerobic work (P < 0.05). Whereas overpacing induced a significant prolongation of the AVCT during aerobic work (4.17 +/- 1.78 ms per 10 beats/min) and anaerobic work (3.84 +/- 1.60 ms per 10 beats/min), underpacing yielded a significant shortening of the AVCT by about 4.49 +/- 2.64 ms per 10 beats/min during aerobic work and 4.75 +/- 1.87 ms per 10 beats/min during anaerobic work (P < 0.01). The slopes of the regression lines of the relationship between AVCT and pacing rate were not significantly. different. Based on the reciprocal relationship of heart rate (HR) and AVCT, basic concepts may be established for a dromotropic rate responsive algorithm.

Aged↗
PubMed1999

Relationship between atrioventricular delay and oxygen consumption in patients with sick sinus syndrome: relevance to rate responsive pacing.

To develop a dromotropic-controlled rate adaptive algorithm for patients with sick sinus syndrome (SSS) and intact AV conduction, 14 pace-maker patients with SSS underwent cardiopulmonary exercise testing (CPX). During exercise, the pace-maker was programmed in an AAT mode without rate adaptation, whereby 3 patients developed supraventricular arrhythmia and 11 patients kept sinus rhythm. Chronotropic incompetence (CI) at heart rate (HR) < 95 beats/min at the anaerobic threshold (AT) was found in five patients. In patients with chronotropic competence (CC), the HR increase was significantly greater than in CI patients (rest: 73.2 +/- 12.6 vs. 64.2 +/- 4.0 beats/min;AT:101.2 +/- 6.2 vs. 82.0 +/- 5.1 beats/min;peak: 135.2 +/- 10.7 vs. 103.2 +/- 10.9 beats/min). There was no significant difference in the AVD between CC and CI patients (rest: 167.7 +/- 38.6 vs. 170.8 +/- 22.5 ms, AT: 156.2 +/- 30.7 vs. 163.6 +/- 21.6 ms, peak: 144.7 +/- 29.0 vs. 152.4 +/- 15.0 ms). The correlation coefficient between HR increase and VO2 was +1.0 and between AVD decrease and VO2 - 1.0 in both groups. An increase in pacing rate from 75 beats/min to 120 beats/min without exercise (overpacing) led to a prolongation of the AV interval of about 30.6 +/- 14.2 ms. Based on this closed loop control with negative feedback, a dromotropic rate adaptive algorithm for patients with SSS and intact AV conduction could be developed.

Aged↗
PubMed1999

Results from the use of a preshaped lead for single-pass VDD/DDD stimulation.

Main criticisms about single-pass VDD stimulation in patients with AV block and normal sinus node function concern atrial undersensing in a lead with floating atrial electrodes, and loss of AV synchrony if sinus node dysfunction develops after implantation. We evaluated the concept of a preshaped single-pass lead designed to place the atrial ring electrodes in a constant position close to, or in contact with, the atrial wall. A preshaped lead (Model 2775, Medtronic Inc.) was implanted in 14 patients and followed for up to 2 years. Mean P wave amplitudes (PWAs) were 3.1 mV at implantation, 1.2 mV at predischarge, and 1.3 mV after 12 months. In all patients, minimal PWAs were well above maximal atrial sensitivity of the pacemaker in all body positions during the complete follow-up; atrial undersensing was not observed. Effective atrial stimulation was possible in all patients at implantation (mean stimulation threshold 2.5 V at 0.50 ms), in 11 patients on the first day after implant (mean stimulation threshold 0.22 ms at 5.0 V), in 10 patients after 1 month (mean stimulation threshold 0.57 ms at 5.0 V), and in 10 patients after 1 year (mean stimulation threshold 0.65 ms at 5.0 V). Intermittent phrenic nerve stimulation could be provoked in six patients. In conclusion, the concept of a preshaped single-pass lead facilitated implantation, improved atrial sensing performance, and allowed atrial stimulation in some patients. Still, further improvements are necessary to decrease the atrial stimulation thresholds to acceptable values in all patients.

Aged↗
PubMed1995

[Severe pneumonitis as a complication of low-dose methotrexate therapy in psoriasis-associated polyarthritis].

A 71-year-old woman with psoriasis-associated rheumatoid arthritis had for 15 months been treated with methotrexate (5 mg/week orally). Four weeks before admission she had developed dyspnoea and cough. On admission her axillary temperature was 38.2 degrees C, the white cell count was normal. Erythrocyte sedimentation rate (50/90 mm), lactate dehydrogenase activity (449 U/l) and the creatinine level (1.33 mg/dl) were all elevated. Blood gas analysis revealed partial respiratory impairment (pO2 52 mm Hg), and the chest X-ray demonstrated bilateral interstitial-alveolar changes. Despite antibiotics the temperature continued to rise, and on the 11th day a blood eosinophilia of 4% was noted. The bronchial mucosa was normal on bronchoscopy, and transbronchial biopsy showed only minor interstitial fibrosis, occasional macrophages and lymphocytes. Cultures of the lavage-fluid were negative. As methotrexate pneumonitis was suspected the drug was discontinued and prednisolone administered (50 mg daily for 3 days, gradually reducing over 7 days). The symptoms quickly improved, and blood gas analysis and the X-rays became normal. The patient was discharged symptom-free after 30 days.

Acute Disease↗
PubMed1981

Which pathologic characteristics influence echographic patterns of retinoblastoma?

Disagreement still exists regarding the influence of rosette formation, pseudorosettes, necrotic changes, vascularity, and calcification on the echographic characteristics of retinoblastoma. To further evaluate the echographic pattern of retinoblastoma confirmed by tissue diagnosis, we studied 11 consecutive cases of retinoblastoma and correlated pathologic findings with A- and B-scan echographic findings. In five patients with heavily calcified tumors, the A-scan echograms were more accurate in documenting reflectivity and revealed an extremely highly reflective pattern attenuating the ultrasonic beam substantially and casting characteristic shadows on the sclera. The B-scan echogram revealed a mass attenuating the ultrasound beam. This mass had dense focal echoes persisting at lower sensitivity within the tumor. In five patients with mild calcification on pathological examination, the A-scan echogram showed a highly reflective pattern. In one case with no calcification, the A-scan echogram revealed a medium reflective pattern. The B-scan echogram revealed a well-defined mass in each case. The degree of rosette differentiation, pseudorosettes, or necrosis failed to correlate with A-scan echographic pattern specific for retinoblastoma. No case showed a cystic appearance on B-scan echogram regardless of the degree of necrosis seen in the pathologic specimen. The echographic findings in retinoblastoma depend primarily on the degree of calcification and are not influenced independently by other specific pathologic characteristics of the tumors.

Calcinosis↗
PubMed1979

Conjunctival biopsy in the diagnosis of sarcoidosis.

The diagnosis of sarcoidosis with ocular involvement is often difficult and accompanied by a certain measure of uncertainty due to a paucity of additional physical signs. In the ophthalmic literature, it is controversial as to whether biopsy of a clinically normal conjuctiva should be done if sarcoidosis is suspected. Many authors advocate biopsy only in the presence of conjunctival follicles or nodules. However, a positive biopsy from a clinically normal-appearing conjunctiva has been reported. Recently, we saw a patient with bilateral uveitis, evanescent cranial nerve palsies, and other clinical manifestations suggesting central nervous system and ocular sarcoidosis. Random biopsy of a normal-appearing conjunctiva revealed a noncaseating granuloma consistent with sarcoidosis. Since conjunctival biopsy is a simple office procedure with minimal morbidity, this diagnostic tool should be considered for patients with clinically suspected sarcoidosis, even in the absence of conjunctival follicles or nodules.

Adult↗
PubMed1979

Familial porphyria cutanea tarda in a patient with retinitis pigmentosa.

The patient in this report had typical retinitis pigmentosa which apparently was of recessive inheritance. In addition, she had an exacerbation of porphyria cutanea tarda (PCT) while taking oral contraceptives. In view of the lack of evidence for hereditary transmission of PCT it is also of interest that the patient's mother had an exacerbation of PCT while taking estrogenic medication.

Adult↗
PubMed1977

Swimmer's goggles for keratoconjunctivitis sicca.

Swim goggles with a moist chamber effect have been used successfully in seven patients with severe keratoconjunctivitis sicca unresponsive to the conventional means of therapy including artificial tears, mucolytics, and occlusion of the puncta. The longest follow-up is three years, the shortest six months. There have been no complications, and in all cases the patients have been subjectively and objectively improved.

Aged↗
PubMed1970

Seronegative dementia paralytica: report of a case.

Dementia paralytica may present diagnostic difficulties when routine serological test using a non-treponemal antigen is non-reactive. We present an illustrative demented patient who initially had negative VDRL test both in his serum and cerebrospinal fluid. However, the brain biopsy specimen showed active meningoencephalitis. By special staining technique, a spiral organism was found in the brain exhibiting morphology perfectly compatible with treponema pallidum. Later in the course, the VDRL became reactive in the blood but remained non-reactive in the cerebrospinal fluid. On the basis of the experience of other workers in the field and ours with this patient, we advise the use of FTA-ABS test as a screening procedure in patients with neurological problems of possible syphilitic origin. We urge further research in this field.

Adult↗