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Biomedical subjects

A Starr

Publications and source records attributed to A Starr.

At least 289 records · Page 16Linked to original sources
PubMed1977

Myocardial revascularization and carotid endarterectomy: a combined approach.

The approach to the patient with combined carotid and coronary artery occlusive disease has been evolving since corornary bypass procedures became feasible. When neurological and cardiac symptoms are remote, sequential procedures are adequate. Neurological symptoms or severe carotid stenoses (or both) appearing simultaneously with symptoms of myocardial ischemia present a more difficult problem. Simultaneous operation has been performed in 16 patients with 1 early death (low output) and 2 cerebral complications (1 patient with residual hand weakness and 1 without neurological risidua). The morbidity and mortality seemed unrelated to the fact that procedures were done at one operation. Therapy, however, must be tailored to the individual patient.

Acute Disease↗
PubMed1977

The Starr-Edwards model 6000 valve. A fifteen-year follow-up of the first successful mitral prosthesis.

The Starr-Edwards model 6000 mitral valve was the first successful mitral prosthesis. A fifteen year follow-up of 110 patients undergoing isolated mitral valve replacement with this prosthesis from 1960 to 1966 is presented. There were 22 (20%) operative and 37 (42%) late deaths at a mean of 8.6 years postoperatively. Preoperative variables leading to late death and thromboembolism are analyzed. Seventeen of 25 operative survivors had improvement in their NYHA Functional Class status and eight other remained unchanged an average of 13.1 years after surgery. There are 5000 patients world-wide currently relying on this prosthesis. Despite a high rate of thromboembolism in the past, elective replacement is not recommended except in selected patients.

Aged↗
PubMed1977

Effects of infusion of cardiotomy suction blood during extracorporeal circulation for coronary artery bypass surgery.

The effects of infusion of cardiotomy suction blood during extracorporeal circulation were evaluated in 15 patients undergoing coronary artery bypass surgery without the use of a left ventricular vent. In Group I all cardiotomy suction blood was discarded. In Groups II and III cardiotomy suction blood was reinfused without and with Dacron wool filtration, respectively. Marked hematologic changes were noted in the pericardial samples which also were reflected in oxygenator samples obtained at the end of bypass. Although postoperative bleeding was significantly greater in patients from Group II as compared to Group I, no differences were seen in total intraoperative and postoperative transfusion requirements. No patient required reoperation for bleeding. Recirculation of larger volumes of cardiotomy suction blood potentially could contribute to bleeding problems in the immediate postoperative period.

Blood↗
PubMed1977

Development of auditory function in newborn infants revealed by auditory brainstem potentials.

Auditory brainstem potentials were recorded from scalp electrodes in 42 infants ranging in gestational age from 25 to 44 weeks. The latencies of the various potential components decreased with maturation. Wave V, evoked by 65-dB sensation level clicks, changed in latency from 9.9 msec at 26 weeks of gestation of 6.9 msec at 40 weeks of gestation. Central conduction times in the auditory pathway also decreased with maturation from 7.2 msec at 26 weeks to 5.2 msec at 40 weeks. The effects of brainstem and cochlear disorders on auditory brainstem potentials were noted in several abnormal infants. The application of all of these techniques could permit an objective definition of both normal and abnormal sensory processes in newborn infants.

Action Potentials↗
PubMed1977

Prognosis of patients after open mitral commissurotomy. Actuarial analysis of late results in 100 patients.

The continuing controversy between proponents of open and closed commissurotomy might be clarified by analysis of late follow-up with modern actuarial techniques that provide a true perspective of patient risk. We have used open mitral commissurotomy exclusively for 15 years in 100 patients. There was one operative death from pancreatitis and one late death from cancer; the actuarially projected survival rate (+/- the standard error) at 10 years is 97 per cent (+/- 2). Thirteen patients had preoperative emboli, 6 of whom were in sinus rhythm and 7 in atrial fibrillation. Two patients had postoperative emboli, both in sinus rhythm. The actuarial chance of remaining free of embolism at 10 years is 97 per cent (+/- 2). Sixteen patients required reoperation on the mitral valve for functional deterioration. The remaining survivors were in Class I or II when last seen. The actuarial chance of not requiring a reoperation after 5 years is 91 per cent (+/- 4) and at 10 years, 38 per cent(+/- 16). Results in different centers are difficult to compare for many reasons, but imprecise statistical methods further obscure such comparisons. The use of actuarial techniques may help to define the role of open mitral commissurotomy.

Adult↗
PubMed1977

Aortic valve replacement: a ten-year follow-up of non-cloth-covered vs cloth-covered caged-ball prostheses.

From 1965 to 1976, 721 isolated aortic valve replacements were performed at the University of Oregon hospitals, utilizing Starr-Edwards caged-ball prostheses. Three models of aortic prostheses were introduced during this period: a non-cloth-covered model has been in continuous use since 1965; a cloth-covered model was begun in 1968 and has been supplanted by the modified composite-strut or "track" model since 1972. The 5-year actuarial survival rate for operative survivors is about 80% for both non-cloth-covered and cloth-covered valves, while the 10-year survival is 61%, based on the older model only. The actuarially-determined percentages of patients experiencing significant thromboembolic episodes (i.e., all except transient ischemic episodes) at 5 years are 7% for the cloth-covered and 9% for the non-cloth-covered model. If transient ischemic attacks are included, the cloth-covered model has only an 8% incidence at 5 years compared to a 22% incidence for the older model. However, the cloth-covered valves are subject to a higher risk of reoperation because of the possibility of cloth injury. The "track" valve, therefore, was designed with exposed metal on the inner surface of each strut to prevent ball-cloth contact. In 107 patients (mean follow-up period 1 year) receiving anticoagulation, this prosthesis has maintained the same low incidence of thromboembolism as the previous cloth-covered model, with no reoperations for valve failure.

Aortic Valve↗
PubMed1976

Correlation between confirmed sites of neurological lesions and abnormalities of far-field auditory brainstem responses.

Far-field auditory brainstem responses were recorded in ten patients in whom the distribution of pathology was defined at autopsy or at operation. The response normally consists of seven components in the initial 10 msec following click signals. Interruption of audiotory pathway at the junction of VII nerve with brainstem results in loss of response components after Wave I. Interruption of auditory pathway at the midbrain results in loss of response components after Wave III. We conclude that Wave I reflects activity of VIII nerve, Waves II and III reflect activity of cochlear nucleus, trapezoid body, and superior olive and Waves IV and V reflect activity of lateral lemniscus and inferior colliculus. The generators of Waves VI and VII were not defined.

Acoustic Stimulation↗
PubMed1976

Improvement in forward coronary blood flow by using a reversed saphenous vein with a competent valve.

Reversed segments of saphenous vein have been the grafts of choice for aortocoronary bypass (ACB). Internal mammary arteries and free radial autografts have recently been shown to have a higher ppatency rate, but flow is usually lower. Normally forward coronary blood flow ceases and retrograde flow occurs during cardiac systole. Prevention of retrograde flow with a rapidly acting valve proximal to the coronary artery anastomosis should improve forward coronary blood flow. Thirty-nine reversed saphenous veins containing a competent valve were implanted in 32 patients undergoing ACB. After accurate zero flow was determined and a resting state achieved, mean (22 veins) and pulsatile (17 veins) flows were measured distal to the valve with the valve competent and temporarily incompetent. A competent valve in 10 right coronary artery vein grafts increased mean flow by 29.7% (+41 ml/min; p less than 0.005) and pulsatile flow in 6 veins by 17.7% (p less than 0.001). A competent valve in 12 left coronary artery vein grafts increased mean flow by 31.3% (+34 ml/min; p less than 0.01) and pulsatile flow in 11 veins by 13.7% (p less than 0.001). This study suggests that a portion of reversed saphenous vein containing a competent valve provides greater coronary artery blood flow than veins without valves and may be the conduit of choice for coronary artery revascularization.

Blood Flow Velocity↗
PubMed1976

Auditory brain-stem responses in brain death.

Auditory brain-stem responses were measured by far-field recording techniques in 27 patients fulfilling the criteria of brain death. The responses were either absent or consisted of the presence of just the initial component (Wave I). Wave I, when present, was of normal amplitude but prolonged in latency. Four patients were followed over several days from a state of coma with evidence of preserved brain-stem and cerebral functions to a clinical state compatible with brain death. Auditory brain-stem responses were initially intact and then showed a decrease in amplitude and a prolongation of latency of the later components until finally Wave I was alone. Auditory brain-stem responses are an objective measure of one of the sensory pathways traversing the brain-stem and can be used to evaluate the functional states of the brain-stem in patients in whom the question of brain death has been raised.

Adult↗
PubMed1976

Synaptic events and discharge patterns of cochlear nucleus cells. I. Steady-frequency tone bursts.

Unitary discharge patterns (peristimulus time histograms or PSTH) and synaptic events were studies with intracellular recording techniques in 164 cat cochlear nucleus cells to steady-frequency tone bursts 250 ms in duration. There were four response types defined on the basis of the shape of the discharge patterns to tones at the characteristic or best frequency. Primarylike units resemble eighth nerve fibres and have a maximum discharge at tone onset, followed by a smooth decline to a steady level of activity. Buildup units have a transient response at tone onset, followed a period of little or not activity before gradually increasing their discharge rate for the remainder of the tone burst. Onset units have an initial burst of spikes at the onset, with little or no activity for the remainder of the tone burst. Pause units have a long latency (10-30 ms) between tone onset and the appearance of low levels of unit activity, which then gradually increase in rate for the remainder of the tone burst. Changes in signal frequency or intensity within the excitatory response area did not modify response patterns of primarylike and onset units, but could evoke primarylike patterns in buildup and pause units. Inhibition manifested by suppression of spontaneous activity and membrane hyperpolarization were of three kinds: 1) in response to signals at the edges of the excitatory response area (i.e., the inhibitory surround) and detected in onset buildup, and pause units but not in primarylike units; 2) occurring at the offset of tones in the excitatory response area and detected in all four types of cochlear nucleus cells; 3) during excitatory tone bursts in onset and buildup units associated with the periods of suppressed unit activity. Membrane hyperpolarization did not accompany the delay in unit activity after tone onset in pause units. Inhibitory events in cochlear nucleus cells provide mechanisms for producing diversity in the temporal pattern of discharges to acoustic signals which may underly the encoding of complex features of sounds.

Acoustic Stimulation↗
PubMed1976

Synaptic events and discharge patterns of cochlear nucleus cells. II. Frequency-modulated tones.

Responses of 99 cochlear nucleus cells and 24 cochlear nerve fibers were studied with FM signals; 14 cochlear nerve fibers and 57 cochlear nucleus cells were studied at four rates of modulation and several signal intensities. Classification of FM response patterns as symmetrical, asymmetrical, or unidirectional was based on the calculation of a symmetry factor (S), which compared the number of discharges evoked by the ascending and by the descending phases of the FM sweep. Certain FM response patterns could not adequately be described by the symmetry factor along and variables of modulation rate and signal intensity had significant influence. A correspondence was found between the four response classes evoked by a steady-frequency tone burst (primarylike, buildup, onset, and pause) and the FM response pattern. Cochlear nerve fibers showed symmetrical response patterns to FM stimulation. Primarylike units were similar to eighth nerve fibers and generally showed symmetrical FM responses. Occasional eighth nerve fibers and primarylike cells developed asymmetry at the fastest rate of modulation (50 sps). Buildup units showed a variety of response patterns to FM signals. Onset units generally showed asymmetrical response patterns with the greater response occurring to the ascending than to the descending phase of the FM sweep. Pause units showed a characteristic inhibition of activity at 5 sps (rate-dependent inhibition). Of the 57 cochlear nuclear cells studied in response to FM signals, 16 were symmetrical, another 16 were symmetrical except at the fastest modulation rate, 12 were asymmetrical, 3 were unidirectional, and 10 showed complex responses to certain signal rates or intensities. It is clear the the cat cochlear with its complex cytoarchitecture is involved in the recoding of acoustic information. Some units in cochlear nucleus demonstrate differential responses to the direction and to the rate of frequency movement. Other cochlear nucleus cells respond as eighth nerve fibers and may serve as simple "relays" in transmitting information from the cochlea to higher auditory centers.

Acoustic Stimulation↗
PubMed1976

Statistical analysis of pacemaker follow-up data. Rate stability and reliability.

In a rate-stable pacemaker, pacemaker rate reflects battery voltage level and should remain constant or be slightly depleted with time in a linear fashion until failure occurs. Linear regression techniques are therefore particularly suited to the analysis of pacemaker rate data. Data on model 8114/8114A Starr-Edwards pacemakers followed at the University of Oregon Health Sciences Center were studied. For a given pacemaker both the slope of the regression line and the standard deviation about the regression line are proportional to the original rate. Natural indices of rate depletion and rate stability for each pacemaker can therefore be calculated by dividing the slope and the standard deviation, respectively, by the inpercept of the corresponding regression line. This model pacemaker has a small average standard deviation so that significant variations from the line of regression, indicating impending pulse generator failure, can be detected in spite of random fluctuations. Emergency and prophylactic replacements can therefore be kept to a minimum so that pulse generator lifetime is maximized. Success in extending pulse generator longevity can be measured by actuarial techniques, which show this pacemaker to have a median battery depletion time of 38 months and a median replacement time of 35 months.

Adolescent↗
PubMed1976

Aortico-left ventricular tunnel. Recognition and repair in infancy.

An infant with an aortico-left ventricular tunnel underwent surgery at the age of five months. There was clinical and electrocardiographic improvement, and postoperative cardiac catheterization demonstrated obliteration of the aortic end of the tunnel, normalization of systemic pulse pressure, mild residual aortic valvular insufficiency, and a decrease in the left ventricular end-diastolic volume index. Early surgery may limit the progression of aortic valvular insufficiency secondary to turbulent aortic-root blood flow.

Angiocardiography↗
PubMed1976

Late results of surgery for left ventricular outflow tract obstruction in children.

Forty-four patients, with a mean age at surgery of 10 years, were followed for 5 to 16 years (mean 9.7 years) after relief of left ventricular outflow tract obstruction. There were no early deaths, but 5 late deaths occurred, 3 following reoperation. Twenty-five patients were recatheterized from 1 to 16 years later (mean 6.6 years). In 21 of 32 patients (66 per cent), a new diastolic murmur followed relief of valvular stenosis; 25 (78 per cent) of these patients had a postoperative diastolic murmur. Seventeen of these 25 (68 per cent) were recatheterized, and 11 of the 17 (65 per cent) had moderate-to-severe aortic incompetence on angiography. Eight patients (18 per cent) have undergone reoperation and 9 more (20 per cent) will have to be reoperated upon soon. Although the aortic valve gradient and left ventricular stroke pressure were reduced in all obstructive types after surgery, left ventricular end-diastolic pressure significantly increased and cardiac index decreased after valvotomy. Cardiomegaly and electrocardiographic (ECG) abnormalities were present in 45 and 66 per cent, respectively, of all postoperative patients. Although 93 per cent of patients may be expected to survive and 82 per cent be reoperation free at 10 years, further surgery thereafter becomes increasingly common. Timely relief of obstruction prevents sudden death and produces excellent symptomatic improvement, but the operation is only palliative. Development of a reliable pediatric valve and ventriculo-aortic conduit may encourage earlier and more aggressive therapy.

Abnormalities, Multiple↗
PubMed1976

Thrombotic phenomena with nonanticoagulated, composite-strut aortic prostheses.

Twenty-nine patients received no anticoagulant therapy after aortic valve replacement with a Starr-Edwards Model 2400 prosthesis. Hemodynamic studies were performed at 3 to 26 months (average 12 months) in 18 of 29 patients. Mean aortic valve gradients ranged from 14 to 62 mm. Hg and averaged 34 mm. Hg. Calculated aortic valve area varied from 0.20 to 1.75 sq. cm. and averaged 0.98 sq. cm. Thirteen of 18 patients had critically stenotic valve orifices. At reoperation or autopsy, examination of the prostheses consistently revealed pannus and thrombus which narrowed the inflow orifice and usually extended to the struts. Of the remaining 11 patients, 3 have died (2 suddenly and one after a cerebrovascular accident), 2 have had embolic episodes, and 6 have refused a repeat study but are being given anticoagulant therapy. Clinical examination, serum lactic dehydrogenase (LDH) levels, phonocardiography, echocardiography, and fluoroscopy of the prosthesis were often unrevealing. Cardiac catheterization was the only reliable method for critically evaluating prosthetic function. In conclusion, close follow-up, preferably with cardiac catheterization, is recommended in any patient who received a Starr-Edwards Model 2400 aortic valve prosthesis without anticoagulation. Long-term anticoagulation with sodium warfarin is indicated in all patients with a Model 2400 aortic valve prosthesis unless there is a contraindication to such therapy.

Aortic Valve↗