Natural stimuli evoking somatosensory potentials.
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Ankle Joint↗
Biomedical subjects
A Starr
Publications and source records attributed to A Starr.
Common pulmonary vein atresia: Importance of immediate recognition and surgical intervention.
Common pulmonary vein atresia is a rare congenital anomaly; all four pulmonary veins drain into a common dilated chamber with no direct connections to the heart or systemic venous system. Since its first description in 1962, 16 cases have been reported. Only four patients were surgically managed and none survived. This communication presents the seventeenth reported case of common pulmonary vein atresia and the only patient whose anomaly was suspected early enough to demand immediate surgical management, with gratifying long-term success. The literature on the subject is reviewed and common features of the anomaly are emphasized to facilitate precise diagnosis, so that a futile search for a nonexistent communicating vein is avoided at the time of operation. This approach has led to the first successful surgical management of this otherwise fatal lesion.
Heart Atria↗
Endogenous late positive component of the evoked potential in cats corresponding to P300 in humans.
A long-latency component of the averaged evoked potential recorded from cats was present only when the evoking stimulus was relevant to the task. The amplitude of this component varied inversely with stimulus probability and was independent of stimulus modality.
Animals↗
Binaural interaction in human auditory brainstem evoked potentials.
Binaural interaction was examined by recording human auditory brainstem responses to clicks from scalp electrodes. Deviations of binaurally evoked responses from the sum of monaurally evoked potentials were observed during waves IV through VI. Amplitude and latency of the interactions depended on click polarity: condensation clicks produced interactions of larger magnitude and longer latency than did rarefaction clicks. Latency differences cannot be accounted for by small latency shifts of the components of monaurally or binaurally evoked potentials resulting from changes in click polarity. Binaural interaction amplitude decreased as click intensity decreased and interaural delay increased. Attenuation of binaural interaction with interaural time differences was maximal at an interaural delay of 900 microseconds. Latency of interaction was prolonged in one subject with low- and high-frequency hearing loss; latency of binaural interaction in subjects with only high-frequency hearing loss was normal. These results suggest that binaural interaction in these potentials reflects binaural processing of low-frequency acoustic stimulation.
Acoustic Stimulation↗
Preoperative criteria predictive of late survival following valve replacement for severe aortic regurgitation.
Forty-five patients underwent aortic valve replacement (AVR) for severe isolated aortic regurgitation from 1973 to 1979. There were two (4.4%) hospital deaths, both functional class IV. Six patients with mechanical prosthesis not receiving anticoagulants were excluded from further analysis. These data relate to 39 patients; the two operative deaths, 35 patients with mechanical prosthesis receiving anticoagulants, and two with bioprosthesis. There were three late cardiac deaths with 5-year survival 85%; average annual mortality rate of 3%. The 5-year survival with pre-AVR left ventricular (LV) ejection fraction greater than or equal to 0.45 was 87% vs 54% less than 0.45, (p less than 0.04); cardiac index greater than or equal to 2.5 L/min/m2 92% vs 66% less than 2.5 (p less than 0.04); mean VCF greater than or equal to 0.75 vs less than 0.75 circ/sec (p less than 0.09); end-diastolic pressure less than or equal to 20 vs greater than 20 mm Hg (p less than 0.08). Late survival was not significantly different between pre-AVR functional class I and II vs class III and IV; LV end-diastolic volume index greater than or equal to 210 vs less than 210 ml/m2; LV end-systolic volume index greater than or equal to 110 vs less than 110 ml/m2; and LV mass greater than or equal to 240 vs less than 240 gm/m2. With ejection fraction greater than or equal to 0.50 there was only one operative death (functional class IV) and no late cardiac deaths. Thus late survival following aortic valve replacement for severe isolated aortic regurgitation is better predicted preoperatively by the LV systolic pump function variables of ejection fraction and cardiac index than by LV diastolic parameters and clinical status.
Adolescent↗
Mechanically and electrically evoked somatosensory potentials in human: scalp and neck distributions of short latency components.
Short latency somatosensory potentials evoked by electrical stimulation of the median nerve as well as by mechanical stimulation on the nail of the index finger were recorded from 10 normal adults using a noncephalic reference (the forearm contralateral to the stimulus). Potentials were recorded from 15 electrode locations extending from the level of the 4th thoracic through the 7th, 4th and 2nd cervical vertebrae to the scalp at Oz, P4, P3, A2, A1, C4, Cz, C3, F4, F3 and Fpz. In general, all the components of potentials evoked by mechanical stimulation had electrically evoked counterparts with comparable surface distributions and variations between subjects. Some of the electrically evoked components, which were low in amplitude and variable in occurrence between subjects, did not have mechanically evoked counterparts. Possible generators of the components detected are discussed based on their surface distribution and polarity reversals. A comparable study on patients with well localized lesions must be performed in order to support or disprove the generators proposed.
Adolescent↗
The ultimate prognosis after valve replacement: an assessment at twenty years.
Our experience over a 20-year period consists of 2,135 patients with initial caged-ball valve replacement: 52% aortic, 34% mitral, 12% double, and 2% triple-valve replacements, with 59.2, 39.8, 10.3, and 2.7 patient-centuries of follow-up, respectively. Fifteen-year actuarial survival (+/- standard error) was 43 +/- 2% for aortic and 44 +/- 3% for mitral valve replacement, and 27 +/- 5% for double-valve and 23 +/- 7% for triple-valve replacement. Restricting attention to patients operated on since 1973 divides the series almost in half and does not dramatically improve the 5-year actuarial survival (from 66 +/- 2% to 71 +/- 3% and from 70 +/- 2% to 78 +/- 3% for aortic valve replacement and mitral valve replacement, respectively). There was some alteration in the causes of late death: the largest percentage of deaths in both the earlier and current groups, 52%, was cardiac related whereas only 24% and 13%, respectively, were valve related. Over the past two decades operative mortality has declined and, to a lesser extent, late survival after mitral valve replacement has improved. The incidence of embolism has decreased significantly, most notably with the Silastic ball valves. Dramatic improvements in late results will occur primarily by modifying the cardiac-related death rate through earlier operation and improvements in the medical management of postoperative arrhythmias and congestive heart failure.
Actuarial Analysis↗
Cardiac valve replacement in patients over 75 years of age.
Elderly patients with symptomatic cardiac valvular malfunction have a grave prognosis if managed medically but can be offered a reasonable chance for long-term survival and a good chance for improvement by replacement of the malfunctioning valve. A series of patients 75 years of age and older who underwent aortic valve replacement (31 patients) mitral valve replacement (9 patients), or combined valve replacement (on patient) has been reviewed. The overall operative mortality for aortic valve replacement was 23% (17% over the past 5 years) and the 5-year actuarial survival was 54 +/- 11%. The operative mortality for mitral replacement was 11% and the 5-year actuarial survival was 55 +/- 21%. The average hospital stay for survivors was 19 days after aortic valve replacement. Four patients have had embolic events since valve replacement, 3 after aortic and one after mitral valve replacement. The addition of coronary artery bypass surgery to the valve replacement procedure is becoming more frequent and may have contributed to improved operative survival. A literature review of reported clinical experience shows that the advancement of cardiac surgery has permitted a redefining of the group thought as "elderly", and that this group has an improved operative survival with the improvements in cardiac valve surgery.
Age Factors↗
Cerebral potentials evoked by muscle stretch in man.
The cerebral potentials evoked by passive plantar flexion movements of the ankle were recorded by scalp electrodes in normal human subjects. The potential consisted of a biphasic positive wave (P45, P65), a prominent negative wave (N90), and a subsequent positive-negative-positive complex (P120, N145, P190). The components of the potential were of largest amplitude at the vertex, small displacements of the active recording electrode resulting in a marked decrease in amplitudes. The amplitudes of the components were also profoundly affected by changes in the repetition rate of the stimulus and by changes in the acceleration of the stretching movements; they were little affected by changes in the extent or peak velocity of stretch provided that acceleration remained constant. Potentials of similar morphology but of slightly shorter latency could be evoked by percussion of the tendon of tibialis anterior and by electrical simuli delivered through a microelectrode inserted into a pure muscle nerve fascicle of the peroneal nerve innervating one of the pretibial flexor muscles. The results of nerve block experiments (ischaemic/pressure block above the ankle; pressure block and local anaesthetic block of the peroneal nerve at the fibular head) suggest that the afferents responsible for evoking the cerebral potential arose from muscle mechanoreceptors. It is concluded that information about muscle stretch arising from muscle mechanoreceptors (probably muscle spindle endings) reaches the cerebral hemispheres of man at short latency and that the resulting potentials can be readily detected using scalp electrodes.
Adult↗
Assessment of sensory function in the operating room utilizing cerebral evoked potentials: a study of fifty-six surgically anesthetized patients.
Sensory evoked potentials (visual, auditory, and somatosensory) were recorded from 56 patients at the time of surgery to monitor neural function during critical portions of the operation. Fluctuations in latency and amplitude of the components occurred with changes in depth of anesthesia, blood pressure, irrigation, and neural tissue manipulation. Most of these changes were only transient. Permanent changes in evoked potentials occurred with decompression of neural tissue and prolonged retraction. Transient changes were not associated with any change in postoperative neurological function whereas changes in evoked potentials that persisted through the operation were highly likely to be associated with a postoperative change.
Adolescent↗
Short latency mechanically evoked peripheral nerve and somatosensory potentials in newborn infants.
Mechanically evoked short-latency potentials were recorded from ten newborn infants ranging in gestational age from 36 to 42 wk and from a 3-month-old infant during natural sleep. Potentials were recorded from four electrode configurations: (1) over the peripheral nerve at the wrist: distal-proximal; (2) over the peripheral nerve at the axilla-deltoid insertion; (3) over the cervical spinal cord and cerebrum: CII-Fpz; and (4) over the cerebrum: C4-Fpz. All subjects produced clear potentials from configurations 1, 2 and 3. Configuration 4 produced reliable potentials only in one newborn who was large for gestational age (42 wk) and the 3-month-old infant. Average peripheral nerve conduction velocities were 26 m/sec from wrist to axilla and 29 m/sec from axilla to neck. No significant correlation was found between conceptional age and nerve conduction velocity. The application of this technique could allow lesion localization in peripheral as well as central portions of the somatosensory pathway of newborns.
Brain↗
Evaluation of somatosensory pathway by short latency evoked potentials in patients with end-stage renal disease maintained on hemodialysis.
Somatosensory evoked potentials and peripheral nerve conduction velocity were studied on 10 patients with end-stage renal failure maintained on hemodialysis treatment. None of the patients had symptomatic neuropathy and the only abnormal finding on neurological examination was absent ankle jerk in 7 of the 10 patients. Nerve conduction velocities and intercomponent conduction times of the somatosensory evoked potential were determined using electrical stimulation of nerve trunks and mechanical stimulation of the finger. Nerve ending conduction times was determined using a combination of the two stimuli and found to be abnormal in 8 patients. All 10 patients had slowed sensory conduction velocities at some segment of the tested peripheral nerve. Intercomponent time differences in the somatosensory evoked potentials could not be defined in the majority of our patients due to the absence of many of the components, making it impossible to distinguish whether the changes in somatosensory evoked potentials were due to impaired peripheral input, or to changes in the somatosensory pathway.
Adult↗
Severe aortic stenosis in patients 60 years of age or older: left ventricular function and 10-year survival after valve replacement.
From 1962-1977, 99 patients, mean age 65 +/- 0.5 years (range 60-81 years) underwent valve replacement for severe calcific aortic valve stenosis. Ninety-three percent of the patients were in New York Heart Association functional class III or IV. The aortic valve gradient was 76 +/- 3 mm Hg and the aortic valve area index was 0.34 +/- 0.01 cm2/m2. Left ventricular systolic pressure was 207 +/- 4 mm Hg, cardiac index was 2.5 +/- 0.1 l/min/m2, left ventricular ejection fraction was 0.57 +/- 0.02 and left ventricular end-diastolic volume index was 108 +/- 60 ml/m2; left ventricular ejection fraction and end-diastolic volume were normal in 63% of the patients. The operative mortality was 16%. Mean follow-up is 55 +/- 4 months. Using life-table analysis, the 10-year survival, excluding cardiac deaths, is 57.5 +/- 7%. Ninety-one percent of the survivors are in functional class I or II. We conclude that the left ventricular function is normal in two-thirds of elderly patients with severe aortic valve stenosis. After valve replacement, the 10-year survival is most encouraging and most of the survivors are functionally improved.
Aged↗
Early results with composite strut caged ball prostheses.
The Starr-Edwards model 6400/10 mitral and 2400/10 aortic valve prostheses incorporate metallic tracks on the inner aspects of cloth-covered struts in an attempt to preserve the favorable thromboembolic performance of cloth-covered valves while avoiding the risk of cloth wear. Two hundred severity operative survivors of mitral valve replacement with the model 6400/10 prosthesis, all on continuous anticoagulant therapy, have been followed up for a mean period of 2.3 (maximal 6) years. The late survival rate is 91 percent and the removal-free rate is 94 percent at 5 years. The rate of embolism (mean +/- standard error of the mean) is 4.6 +/- 0.9 percent per patient-year. Significant bleeding complications occurred at a rate of 1.0 +/- 0.2 percent per patient-year; there were no deaths. Two hundred forty operative survivors of aortic valve replacement with a model 2400/10 prosthesis, all on continuous anticoagulant therapy, have been followed up for a mean of 2.0 (maximal 7) years. The 5 year survival rate is 84 percent and the removal-free rate is 98 percent. Embolism occurred at a rate of 3.3 +/- 0.8 percnet per patient-year. Hemorrhagic complications occurred at a rate of 2.1 +/- 0.6 percent per patient-year; there were three families. Cloth wear and hemolysis have not been significant problems with this prosthesis, and the rates of thromboembolism are comparable with those reported for xenograft bioprostheses. The composite strut (track) valve prosthesis is a durable alternative to tissue valves in patients who are able to tolerate anticoagulant therapy.
Aortic Valve↗
Mechanically and electrically evoked somatosensory potentials in humans: effects of stimulus presentation rate.
Somatosensory evoked potentials were recorded in response to: (1) electrical stimulation of the median nerve at the wrist; (2) electrical stimulation of the index finger; (3) mechanical stimulation of the index fingernail. Stimuli were presented at rates of 2, 4, 8, 16 and 32/sec, and the effects of presentation rate on components of the evoked potentials were evaluated. The effect of varying the duration of the mechanical stimulus was also observed. The findings suggest that stimulus rates of up to 8/sec can be used without significant loss in detectability of most of the components. The potentials recorded in response to a short duration mechanical stimulus were essentially identical to those evoked by the long duration stimulus. The findings of this study are consistent with a peripheral nerve generator for the Erb's point recorded component, a postsynaptic generator for the upper neck recorded component, and in general with a larger number of synapses leading to the generators of the later components than to earlier ones.
Adult↗
Auditory brain stem responses in the cat. I. Intracranial and extracranial recordings.
A spatial and temporal analysis of auditory evoked potentials within the brain stem were performed in cats to determine the areas of the brain stem having large amplitude voltage fields, corresponding in latency to each of the components of the scalp-recorded auditory brain stem response (ABR). On the basis of this criterion, the first few components (occurring within 2 msec post-stimulus) were attributed to activity in a single structure, the eighth nerve. In contrast, each of the other components was correlated with large amplitude fields in at least two sites within the brain stem auditory pathways. The findings demonstrate a complex spatial and temporal distribution of electrical events within the auditory brain stem pathways, which preclude any simple one-to-one relationship between a given anatomical site and a particular component of the ABR. The possibility that the determination of the generators might be influenced by filtering of the evoked potentials was also examined. High-pass filtering of the evoked potentials resulted in a modification of the defined generators for only one of the components studied (P4). Filtering had little effect on the components of the scalp-recorded ABR.
Animals↗
Auditory brain stem responses in the cat. II. Effects of lesions.
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Animals↗
The use of time-interrelated covariates to predict survival following aortic valve replacement.
One hundred four patients survived isolated aortic valve replacement with the model 1200 prosthesis between 1965 and 1968, with a 12-year survival of 64%. Multiple regression survival analysis was employed in an attempt to determine which of 26 preoperative variables affected late survival and to devise a formula to predict survival for a given individual. The most important variables in the regression equation were right atrial mean pressure, etiology, and sex. The effect of the last two were found to vary with time over the 12-year post-operative period. An extension of the standard regression analysis technique was developed to incorporate time-related cofactors into the model. Based on the multiple regression model, 12-year survival was estimated to range from 92% to 14% for the best and worst combinations, respectively, of the three significant variables. The advantages of the regression method are outlined and the findings of other studies with regard to factors affecting survival after aortic valve replacement are summarized and discussed.
Adult↗