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Biomedical subjects

A Starr

Publications and source records attributed to A Starr.

At least 217 records · Page 12Linked to original sources
PubMed1983

Papillary muscle rupture complicating acute myocardial infarction. Treatment with mitral valve replacement and coronary bypass surgery.

Six cases of complete or partial rupture of the papillary muscle after acute myocardial infarction are presented. All cases were treated by mitral valve replacement and concomitant coronary bypass surgery. An average delay of 3 days between rupture and operation occurred in the four patients with rupture of the main muscle trunk. The operative mortality rate was 50 percent. Such patients present with acute, florid left ventricular failure secondary to the severe mechanical burden imposed on the newly infarcted heart. The resulting valvular incompetence must be corrected by urgent mitral valve replacement if survival is to be lengthened. Patients with partial or apical head ruptures have a lesser degree of regurgitation and symptoms are largely dependent on intrinsic ventricular function. Both of our patients with partial muscle rupture presented with severe heart failure 2 to 4 months later, and both did well postoperatively. We believe that prompt operation without prolonged attempts at medical stabilization is the key to decreasing operative mortality, especially in instances of complete muscle rupture. Since ischemic heart disease remains the leading cause of death in such patients, coronary artery bypass surgery should be performed in conjunction with valve replacement.

Aged↗
PubMed1983

Generation of auditory brain stem responses (ABRs). I. Effects of injection of a local anesthetic (procaine HCI) into the trapezoid body of guinea pigs and cat.

Auditory brain stem potentials were recorded between the skull and a non-cephalic reference electrode in anesthetized guinea pigs before and after the injection of a local anesthetic agent (procaine HCI) into the trapezoid body from a ventral approach. All components except P1, N1 and P2 were affected; N2 was delayed; P3 and N3 were lost; P4 was both broadened in duration and shortened in latency; N4 was attenuated in amplitude. All of these changes were temporary and recovery of the components occurred. Identification of the altered components was aided by their latency and amplitude changes as a function of both stimulus intensity and rate. This study implicates the trapezoid body as contributing to the generation of auditory brain stem components beginning with N2.

Animals↗
PubMed1983

Generation of auditory brain stem responses (ABRs). II. Effects of surgical section of the trapezoid body on the ABR in guinea pigs and cat.

Auditory brain stem potentials were recorded between the skull and a non-cephalic reference electrode in guinea pig and cat before and after midline section of the trapezoid body from a ventral approach. The ABR after complete section was altered: N2 was delayed, P3 and N3 were lost, P4 and N4 were shortened in latency but only N4 was attenuated in amplitude. With partial section of the trapezoid body the amplitude of P3 was linearly related to the extent of the section. Recordings from the surface of the trapezoid body before and after section revealed a loss of activity contralateral to the ear stimulated and a preservation of activity ipsilateral to the section. Binaural interaction in P4 and N4 was attenuated in a linear manner as a function of the extent of trapezoid body section. This study suggests that auditory brain stem structures contralateral to the midline of the trapezoid body generate components N2, P3, N3, N4, whereas auditory structures ipsilateral to the midline generate components P1, N1, P2 and P4.

Animals↗
PubMed1983

Generation of auditory brain stem responses (ABRs). III. Effects of lesions of the superior olive, lateral lemniscus and inferior colliculus on the ABR in guinea pig.

Auditory brain stem potentials were recorded between the skull (vertex) and a non-cephalic reference in guinea pig before and after making discrete lesions of the auditory pathway in the pons and midbrain. Lesions of the superior olivary complex were accompanied by attenuation of P3 and N3 to contralateral input. Lesions of the lateral lemniscus were accompanied by attenuation of N3 to contralateral input. Lesions of the lateral portion of the pons adjacent to the lateral superior olivary nucleus were accompanied by attenuation of P4 to ipsilateral input. Lesions of the inferior colliculus were without effect on the ABR. These data are interpreted as supporting the hypothesis that each component of the ABR arises from a focal region of the brain stem auditory pathway.

Animals↗
PubMed1983

Variations in early and late event-related components of the auditory evoked potential with task difficulty.

A variation in the difficulty of an auditory discrimination was used to investigate the relationship between the event-related P165, N2 and P3 components of the auditory evoked potential. Equivalent increases in the latencies of all 3 components were found with increased task difficulty. The P165 component, however, could be differentiated from the two later components since it increased in amplitude with increased task demands while the N2 and P3 amplitudes remained constant. It is suggested that the P165, N2 and P3 components comprise a functional sequence in the processing of rare events and possibly involved in a subject's preparations for the future.

Adult↗
PubMed1983

Middle and long latency auditory evoked potentials in cat. I. Component definition and dependence on behavioral factors.

Middle (10-50 ms) and long (50-600 ms) latency auditory evoked potentials (AEPs) were investigated in artificially respired, muscle-paralyzed cats. Similarity to human potentials of comparable latencies was examined in two ways: (1) the similarity of waveform features such as peak amplitude, polarity and latency, and (2) the effects of task-related variables on these various waveform features. Four behavioral variations of a classical pupillary conditioning paradigm were used to vary attention and arousal. Twelve peaks and troughs were identified in the AEP: P10, N13, P17, N22, P31, N41, P55, N70, N100, N140, P260 and N520. Principal components analysis (PCA) defined 7 AEP components, some of which spanned several peaks. Analysis both of peak latencies and amplitudes, and of principal component scores, revealed differential effects of the behavioral manipulations on these components: those with latencies longer than 50 ms were strongly influenced by behavioral variations, while earlier components were relatively immune to these effects. On the basis of these findings, several relationships between cat and human AEP components were suggested. Specifically, peaks P10-P41 in the cat were thought related to human middle latency components, cat P55 to human P50, cat N140 to human N300, and cat P260 to human P300. Cat N520 was comparable to several long latency components in humans. No obvious correspondences between cat AEP components and human N90 and P170 were identified.

Acoustic Stimulation↗
PubMed1983

Middle and long latency auditory evoked potentials in cat. II. Component distributions and dependence on stimulus factors.

The middle (10-50 ms) and long (50-600 ms) latency periods of the auditory evoked potential (AEP) were investigated in muscle-paralyzed, artificially respired cats with respect to two issues: (1) the distribution of components across the skull, and (2) the effects of changing stimulus intensity on component latencies and amplitudes. The distributional data were gathered during a behavioral study in which four behavioral tasks related to classical pupillary conditioning were used to vary attentional and arousal processes. The distributions across the skull surface (averaged across tasks) of 12 peaks and troughs (P10, N13, P17, N22, P31, N41, P55, N70, N100, N140, P260 and N520) and seven principal components derived from the set of waveforms collected during this experiment are reported. Both peak amplitudes and principal component scores were distributed differentially across the skull surface. In the second experiment, acoustic stimulus intensity was varied, and AEPs collected from a vertex and temporal electrode site. In general, increasing stimulus intensity had a stronger influence on the earlier portions of the AEP, where increased amplitude and decreased latency was the rule, than on later ones. The relationships between cat and human AEP components were discussed based on both the data presented in this paper and in previous papers.

Acoustic Stimulation↗
PubMed1983

Effect of verapamil on basal and pentagastrin-stimulated gastric acid secretion.

The role of calcium in gastric acid secretion is still uncertain. The effect of verapamil on basal and pentagastrin-stimulated gastric acid secretion was evaluated in eight normal men. Submaximal pentagastrin tests (2 micrograms/kg/hr) were performed after pretreatment with intravenous verapamil at a concentration of 0.1 mg/kg and followed 1 hr later with a second bolus injection of 0.15 mg/kg. On a separate day, subjects received a placebo injection of saline solution at the same designated times as the verapamil. Verapamil did not alter basal or stimulated gastric acid secretion. All subjects showed ECG evidence of significant calcium-channel blocking (i.e., prolongation of PR interval). Data indicate that therapeutic doses of a calcium slow-channel antagonist do not alter gastric acid secretion in normal subjects. Results support the concept that in vivo, secretory function of the human parietal cell is not affected by alteration in cellular calcium flux.

Adolescent↗
PubMed1983

Focal facial spasm.

An unusual case of focal facial spasm modified by factors affecting the peripheral facial nerve was investigated in a 32-year-old woman with involuntary contractions at the left mouth and nasal area. Voluntary facial movements were normal. The involuntary spasms ceased with digital pressure over the facial nerve in the left stylomastoid area. A difference between voluntary and these involuntary facial movements occurred both with local anesthetic blockade and with crushing of the facial nerve. Blink reflexes demonstrated unilateral left synkinesis, and facial EMG showed clonic discharges and individual motor units that discharged rapidly (200 Hz). Treatment with diphenylhydantoin, carbamazepine, and prednisone was ineffective. Neurolysis of the peripheral facial nerve resulted in temporary relief, whereas biofeedback controlled the spasms. Focal facial spasms may represent a disorder of the facial nucleus influenced by both peripheral and central mechanisms.

Adult↗
PubMed1983

Sequential changes in the P3 component of the auditory evoked potential in confusional states and dementing illnesses.

The P3 component of the auditory evoked potential has been shown to reflect "endogenous" processes related to cognition. This component was measured serially in seven patients who had confusional states or dementing illnesses that fluctuated in severity over time. The latency of P3 component reflected the clinical impression of changes in mental function for each of the patients. These results suggest that the P3 component of the auditory evoked potential provides an objective serial measure of cognitive state that may be useful in following patients with dementing illnesses and in evaluating the effectiveness of any specific therapy.

Adult↗
PubMed1983

Coronary bypass operation following acute complicated myocardial infarction.

The indications for operation to correct acute mechanical defects after myocardial infarction are clearly established. Less clear is the use of surgical procedures for nonmechanical complications such as persistent ischemia or circulatory collapse. Between 1974 and 1981, 80 patients underwent coronary artery bypass grafting (CABG) within 2 weeks of infarction. Continued pain was the indication in 83% and cardiogenic shock in 17%. Seventeen patients were operated upon within 24 hours of infarction, 35 from 1 to 7 days, and 28 from 8 to 14 days. Eighty-one percent were men; mean age was 58 years. In 39% of patients the infarction was the premier symptom of coronary artery disease. Sixty-two percent had impaired left ventricular function as judged by left ventricular end-diastolic pressure greater than 15 mm Hg or abnormal wall motion seen on ventriculogram. Overall operative mortality was 5.0%; early mortality by indication was 3.0% for pain and 14.3% for shock. Operation for pain carried a 7.7% mortality if done within 48 hours of infarction and was 0% for those patients operated upon after that time. The status of 90% of all patients was known as of December, 1981, with a mean follow-up of 2.9 years. Life-table analysis demonstrates a 5 year survival rate of 85% +/- 6% in the group operated upon for pain. CABG in the immediate postinfarction period can be done safely with a 5 year survival in patients without hemodynamic compromise comparable to that of patients with chronic angina undergoing elective operation. These results should encourage the application of early postinfarction CABG in other high-risk subgroups of patients.

Angina Pectoris↗
PubMed1983

Aortic valve replacement with coronary bypass grafting. Significant determinants of ten-year survival.

Concomitant aortic valve replacement (AVR) and myocardial revascularization were performed on 197 patients between 1969 and 1981. Operative mortality during the period 1969 to 1975 was 15.6% compared to 5.0% for the years 1976 to 1981 (p less than 0.02). The incidence of perioperative myocardial infarction (PMI) declined over the same period from 14.2% to 2.0% (p less than .01). Functional class and left ventricular end-diastolic pressure significantly influenced mortality, whereas age, sex, duration of symptoms, cardiac index, wall motion abnormality, type of valve lesion, and completeness of revascularization did not. Type of myocardial preservation did not significantly affect operative mortality, although a trend favoring either cardioplegia or continuous perfusion of both coronary ostia and grafts was observed. Life-table analysis shows a survival rate during the 10 year follow-up period equal to that of patients undergoing isolated AVR. Cornary bypass grafting (CABG) returns patients with combined aortic valve (AVD) and coronary artery disease (CAD) to a prognostic curve determined by their valvular disease alone.

Adult↗
PubMed1983

Mitral repair in complete atrioventricular canal. Ease of correction in early infancy.

During the past 5 years all patients with complete atrioventricular (AV) were subjected to surgical correction regardless of age. Thus we were able to assess the ease and reliability of mitral repair in early infancy. Key features of operation include division of bridging leaflets when indicated, selection of a patch sufficiently small to prevent postoperative annular dilation, attachment of the leaflets to the patch with continuous nonpledget-supported sutures at a level determined by the chordal structure, and, based on the size of the mural leaflet, construction of a bicuspid or tricuspid mitral valve. Operative mortality and postoperative morbidity were no greater in patients under 6 months of age than in older patients. Reoperation for mitral regurgitation was required in three patients. In all of them, the primary reason for the failure of repair was that the mitral valve had been left tricuspid; in two of them, the mitral anulus was dilated, as well. Repair was uniformly accomplished by bicuspidization, combined in two instances with a Wooler-type annuloplasty and shortening of the free margin of the aortic leaflet. The absence of secondary scarring of the leaflets in the patients under 6 months of age facilitated repair in this age group. Early repair is possible, and preferable, provided that meticulous attention is paid to the technical features of the repair and a proper decision is made with regard to treatment of the mitral "cleft."

Aging↗
PubMed1982

Auditory brain stem responses in chronic alcoholic patients.

Auditory brain stem responses (ABRs) were obtained from 66 chronic alcoholic patients. Forty-one percent of the patients had abnormal ABR indicated by prolonged interwave intervals. The incidence of brain stem abnormalities was related to age, the type and number of alcoholic neurological complications, and cerebral atrophy in computerized tomographic (CT) scan. There was a progressive increase in the incidence of abnormal ABRs with age and the number of alcoholic neurological diseases. Among the neurological complications of alcoholism, patients with cerebellar degeneration had the highest incidence of abnormal ABRs (83%). There was a high correlation between cerebral atrophy in CT scan and abnormal ABRs. The data suggest that laboratory methods such as the ABR and CT scan are useful in evaluating the extent of CNS abnormalities in alcoholic patients.

Adolescent↗
PubMed1982

Chemoprophylaxis in cardiac and orthopedic surgery: comparison of cephalothin and cephapirin.

In a retrospective sequential study we determined the rate of infection occurring despite cephalothin or cephapirin chemoprophylaxis in orthopedic and cardiac surgery done from 1973 to 1977. The incidence of infection after prosthetic hip placement or open reduction of hip fracture was 3.4% and 1.0% in patients receiving cephalothin or cephapirin, respectively. The infection rate after prosthetic heart valve implantation was 3.5% in those receiving cephalothin and 1.6% in those receiving cephapirin. There was no significant difference in infection rate, duration of fever greater than or equal to 38.0 C, or length of postoperative hospitalization. The efficacy of selected antistaphylococcal antibiotics in preventing colonization of human fibrin clots by staphylococci was studied. Although cephapirin was effective at lower concentration, the activity of cephalothin and cephapirin was comparable. Cephalothin and cephapirin have equivalent chemoprophylactic activity by clinical and microbiological criteria, permitting cost to be used as a basis for choosing between these antibiotics.

Cardiac Surgical Procedures↗
PubMed1982

Distribution of auditory brainstem potentials over the scalp and nasopharynx in humans.

Auditory brainstem potentials were recorded from various scalp and nasopharyngeal sites referenced both to a noncephalic site and to certain scalp locations in normal humans. The distribution of amplitudes and latencies of the components were defined. There were significant amplitude, polarity, and latency asymmetries over the scalp in both referential and differential recordings. The data indicated that several of the ABR components have generator sources that are lateralized and move through the brainstem in particular orientations.

Adult↗