Search PubMed⌕ Search

Biomedical subjects

A Starr

Publications and source records attributed to A Starr.

At least 181 records · Page 10Linked to original sources
PubMed1986

Ten year survival after coronary artery bypass surgery for angina in patients aged 65 years and older.

We have assessed the long-term results of coronary bypass surgery for angina from 1974 to 1983 in 1304 patients aged 65 years and older (group 1). Using actuarial techniques, we determined that the 5 year and 10 year survival rates for patients 65 years old or older were 81 +/- 2% and 65 +/- 3% (mean +/- SE), respectively. The patients aged 65 years and older were further subdivided into those aged 65 to 74 years (group 1a) and 75 to 84 years (group 1b) and were compared with 1700 patients aged 55 to 64 years (group 2). The operative mortality in the three subgroups was 3%, 3%, and 2%, respectively (p = NS). For coronary bypass surgery, the duration of hospital stay was significantly longer (p less than .0001) by a mean of 1 to 2 days for group 1 patients and the cost of hospitalization was higher by a mean of $ 700 (p = .25). The cost of hospitalization was significantly higher only for group 1b patients (p = .005). The 5 year survival rates for the three subgroups (1a, 1b, and 2) were 83 +/- 2%, 73 +/- 5%, and 91 +/- 1%, respectively, and the 10 year survival rates were 66 +/- 3%, 65 +/- 7% (7 year rate for subgroup 1b), and 77 +/- 2%, respectively. The lower survival rates for subgroups 1a and 1b were significant (p less than .001); however, this lower survival was only seen in men.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1986

Late ball variance with the Model 1000 Starr-Edwards aortic valve prosthesis. Risk analysis and strategy of operative management.

The first generation of aortic ball-valve prostheses, used until 1965, was associated with poppet damage owing to fatty infiltration of the silicone rubber ball, a phenomenon termed ball variance. For the Model 1000 Starr-Edwards valves, almost all cases were discovered before 8 years. However, a review of our patients still at risk with the original valve and poppet, prompted by other recent reports of late ball variance, has shown that severe variance can exist up to 20 years after implantation. There is a relationship between the year of valve implantation and the timing and severity of ball variance for the overall series of patients surviving operation, but for the subgroup currently at risk the sample sizes are too small to detect any difference, if one still exists. Only three of 12 patients in the current subset were found to have severe variance. Simple ball change has been the operation of choice. Prophylactic reoperation is not indicated in the current subset, but patients require careful follow-up and should be considered for reoperation should symptoms develop.

Adult↗
PubMed1986

Somatosensory evoked potentials to muscle percussion in humans: upper extremity.

Cortical as well as presumably subcortical potentials were recorded from 20 normal subjects in response to mechanical percussion of the thenar eminence. Nuchal-to-frontal recordings detected an initial negative component at 21 msec, followed by positivities at 29 and 36 msec. C-prime to frontal recordings produced prominent positivities at 29 and 44 msec. Recordings over the peripheral nerve did not reveal consistent potentials. Control experiments indicate that potentials are initiated by fast-adapting muscle receptors. If additional control experiments continue to support these findings, yet another constituent of electrically evoked somatosensory potentials--which may prove useful in the definition of muscle innervation disorders--will have been identified.

Adolescent↗
PubMed1986

Effect of initial reperfusion temperature on myocardial preservation.

The effect of initial postischemic reperfusion temperature on myocardial preservation was studied in the isolated working rat heart model. After baseline measurement of aortic flow rate, coronary flow rate, and heart rate, 40 hearts were subjected to 60 minutes of ischemic arrest at 15 degrees C induced with a single dose of cold potassium cardioplegic solution. Hearts were then revived with a 10 minute period of nonworking reperfusion at 28 degrees, 31 degrees, 34 degrees, or 37 degrees C (10 hearts each), followed by 5 minutes of nonworking reperfusion at normothermia, followed by 30 minutes of working perfusion. Repeat measurements of function were obtained and postischemic release of creatine kinase into coronary effluent was determined. Recovery of aortic flow was significantly reduced at lower initial reperfusion temperatures (75% at 28 degrees C versus 88% at 37 degrees C) and the effect was approximately linear throughout the range studied (p less than 0.05). Release of creatine kinase into coronary effluent was greater at lower initial reperfusion temperatures (421 ImU/min/gm wet weight at 28 degrees C versus 115 ImU/min/gm wet weight at 37 degrees C), also in a linear manner (p less than 0.05). In this model, initial postischemic hypothermic reperfusion is deleterious to cellular integrity and functional recovery of the preserved myocardium. Studies in higher animals and humans are warranted to further evaluate the effect of initial reperfusion temperature on myocardial preservation.

Animals↗
PubMed1985

'Gating' of somatosensory evoked potentials begins before the onset of voluntary movement in man.

The inflow of somatosensory information to the cerebral cortex is modified before and during active movement in animals. This phenomenon has been termed 'gating' and occurs at several levels of the sensory pathway. We studied somatosensory evoked potentials (SEPs) to stimulation of the median nerve at the wrist during voluntary movement of the ipsilateral thumb in man. Results indicate that SEPs are attenuated shortly after a command to move (approximately 100 ms before the onset of the electromyogram (EMG)), become maximally attenuated with maximum EMG and return to normal size when movement is finished.

Adolescent↗
PubMed1985

Intracranial potentials correlated with an event-related potential, P300, in the cat.

Intracranial recordings of long-latency, event-related potentials were obtained from paralyzed, artificially respirated cats. A modified oddball paradigm was employed in which cats were presented with a randomized series of two tones, a 'frequent' 4 kHz stimulus and a 'rare' 1 kHz stimulus. A tail shock was administered 700 ms after onset of the rare tone. Under these circumstances the stimulus elicited a positive component at the vertex similar to the human P300. Intracranial potentials associated with the rare tone usually manifested components of greater amplitude than did potentials associated with the frequent tone. A positive component occurring in latency between 200 and 350 ms only accompanied the presentation of the rare stimulus. The P300 component, which was positive at the dura, appeared as a negative component within a few millimeters of the surface over a wide area of the marginal and suprasylvian gyri. Changing the probability of the rare stimulus resulted in a reduction in the amplitudes of both the intracranial negative component and the P300 recorded at the skull. Components of large amplitude associated with the rare stimulus were obtained from the region of the hippocampus. These components reversed polarity, sometimes more than once, as the electrode was advanced. Substantial latency differences were often observed between the P300 recorded at the skull and P300-like intracranial components associated with the rare stimulus. These results suggest that the cortices of the marginal and suprasylvian gyri and the hippocampal region contribute to the generation of the cat P300.

Animals↗
PubMed1985

Cognitive evoked potentials (P300) in early Huntington's disease.

The P3 component of both auditory-event- and visual-event-related potentials of 13 patients with Huntington's disease was studied and compared with the P3 component of normal patients. The latencies of the patients' P3 components were compared with the latency-age regression lines generated by the normal population in both modalities. A P3 latency was considered abnormal if it fell above the 2-SE limit for the latency-age regression line. The incidence of normal or abnormal P3 latencies in the two modalities was compared with the results of computed tomography, electroencephalography, and neuropsychological testing. Nine patients had abnormal P3 latencies and ten patients had abnormal visual P3 latencies, with seven having abnormal latencies on both tests and 12 having abnormal latencies on one of the two tests. An abnormal P3 latency in one modality did not imply an abnormal P3 latency in the other. An abnormality of the P3 latency did not correlate with an abnormality in results from computed tomography, electroencephalography, or neuropsychological testing.

Adult↗
PubMed1985

About the origin of cerebral somatosensory potentials evoked by Achilles tendon taps in humans.

This study examines the effects of ischemic hypoxia and cooling of the leg, muscle contraction and vibration on cerebral potentials evoked by Achilles tendon taps and posterior tibial nerve stimulation to obtain indirect evidence leading to the identification of receptors activated by tendon taps. Experiments performed during ischemia of the leg showed that these receptors lie between the ankle and the knee. Cooling of the leg showed that they are located deep in muscles or bone. Experiments performed during vibration and muscle contraction suggest that muscle stretch receptors provide the afferent input responsible for Achilles tendon tap evoked potentials. All of these experiments point to primary muscle spindles in the proximal gastrocnemius-soleus muscle belly as the main source of afferent input for evoking cerebral potentials to Achilles tendon taps in humans.

Achilles Tendon↗
PubMed1985

Stimulus frequency and masking as determinants of P300 latency in event-related potentials from auditory stimuli.

The effects of target tone frequency, presence of a masking stimulus, and subject sex on the auditory ERP were studied with an 'oddball' paradigm. P300 latency became shorter (about 15 msec) as the difference between the standard (1000 Hz) and target tone frequency increased (1500, 2000, 4000 Hz) but became longer (about 10 msec) with the presence of a white noise masking stimulus. Similar results were obtained for both the P3a and P3b subcomponents of the P300 potential. No significant differences between the adult male and female subjects were observed. The role of stimulus parameters in applied testing situations is discussed.

Acoustic Stimulation↗
PubMed1985

Late results of combined mitral valve replacement and coronary bypass surgery.

The incremental risk of coronary bypass surgery was analyzed in 718 patients undergoing mitral valve replacement between 1971 and 1983. Ninety-eight patients (14%) had significant coronary artery disease requiring coronary bypass surgery. In 70 of these patients, the origin of the mitral valve disease was nonischemic, whereas 28 patients had ischemic mitral regurgitation unsuitable for conservative valve surgery. There were six operative deaths (9%) and four perioperative myocardial infarctions (6%) after mitral valve replacement and coronary bypass surgery for nonischemic mitral valve disease. Operative mortality was related to low output cardiac failure before operation or perioperative myocardial infarction. Actuarial curves predict survival (+/- standard error) of 55 +/- 7% at 5 years and 43 +/- 8% at 10 years. Preoperative functional class was the only significant predictor of long-term survival in this group (p less than 0.05). The actuarial survival of the 620 patients without coronary artery disease who underwent mitral valve replacement alone was 63 +/- 3% at 10 years. This was significantly better than that of the 70 patients who underwent mitral valve replacement and coronary bypass surgery for nonischemic mitral valve disease (p less than 0.001). Conversely, 5 year survival of the 28 patients with ischemic mitral regurgitation was 43 +/- 10%. This confirms the negative detrimental effect of an ischemic origin of mitral valve disease on survival after mitral valve replacement and coronary bypass surgery (p less than 0.0001).

Adult↗
PubMed1985

The Starr-Edwards valve.

This report reviews the results obtained with the current models of the Silastic ball valve, classifying the experience with the mitral and aortic models into the periods (formula: see text) before and after 1973. Valve failure is defined according to the Stanford method and includes any valve-related death or complication necessitating valve removal (there have been no mechanical failures). Comparison of the valve model used today with the same model used in the late 1960s shows that the results have improved dramatically, especially with regard to thromboembolism. The results obtained with valves implanted after 1973 compare favorably with those of other contemporary valves introduced in the early 1970s.

Aortic Valve↗
PubMed1985

Cerebral somatosensory potentials evoked by muscle stretch, cutaneous taps and electrical stimulation of peripheral nerves in the lower limbs in man.

Somatosensory cerebral evoked potentials were recorded in man to natural forms of somatosensory stimulation of the lower extremity including stretching of the muscle tendons, tapping on muscle bellies and tapping on cutaneous surfaces. These potentials were compared with those evoked by electrical stimulation of peripheral nerves measuring the amplitudes and latencies of the evoked potential components and defining the effects of stimulus variables on these parameters. Spinal cord potentials could only be detected to electrical stimuli. Mechanical stimulation of tendons and muscle bellies evoked scalp potentials at latencies earlier than those evoked by electrical stimulation of the peripheral nerve and by cutaneous stimulation at the same level of the leg. Muscle receptors, most probably muscle spindles, are the source of the short latency components obtained by the stretching of tendons and tapping on muscle bellies. The proximal location of these receptors as well as very rapid spinal conduction account for the latency difference. The potentials were larger to electrical stimulation of nerve trunks than to mechanical stimulation of tendons or skin, suggesting the asynchronous activation of a smaller number of fibres by the latter. Individuals with the largest potentials to one form of stimulation usually had the largest potentials to the other modes of stimulation. The use of physiological stimuli such as muscle stretch to test the transmission in specific neural pathways might be useful in investigating the processing of relatively selective afferent volleys using noninvasive evoked potential recordings.

Adult↗
PubMed1985

Effects of age on the P300 component of the event-related potential from auditory stimuli: peak definition, variation, and measurement.

An auditory "oddball" paradigm was used to elicit the P300 component of the event-related brain potential (ERP) from a large sample of young (5 to 15 years) and older (20 to 86 years) persons. Distinct P3a and P3b subcomponents of the P300 were observed within individuals and across trial blocks. Age affected P300 latency in a similar fashion for both subcomponents with latency increasing about 65 msec between 20 and 70 years. P300 latency variability also was found to increase somewhat with advanced age. These results confirmed previous age-related ERP changes and extended them to the P3a and P3b subcomponents.

Acoustic Stimulation↗
PubMed1985

Mitral replacement: clinical experience with a ball-valve prosthesis. Twenty-five years later.

The purpose of this report is to review the results of mitral valve replacement since a first report in the Annals of Surgery in 1961, in order to determine the relative importance of new valve designs versus other surgical variables. The continued use of the silastic ball valve in its 1966 configuration (Model 6120), by providing a comparative data base for other new prosthetic valves, allows this analysis. For a valid comparison with the tilting disc (Bjork-Shiley) and the porcine (Hancock and Carpentier-Edwards) valves, only results with the silastic ball valves implanted during comparable time frames should be used. (Formula: see text) Thus, there are no significant differences in the results obtained with the silastic ball valve in time frames comparable to other contemporary valves introduced in the early 1970s. Improved results, therefore, must be non-prosthetic valve related.

Actuarial Analysis↗