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Biomedical subjects

D C Miller

Publications and source records attributed to D C Miller.

At least 307 records · Page 17Linked to original sources
PubMed1986

Significant patient-related determinants of prosthetic valve performance.

With rare exception, the bulk of out knowledge concerning the performance of any particular valve substitute originates from one institution; thus, if valve-related complications are more a function of the patient substrate undergoing operation than the prosthesis per se, the usefulness of inter-institutional comparisons would be severely limited. To address this question, the outcome of 2,719 patients after mitral or aortic valve replacement over 12,955 patient-years of follow-up was analyzed by time-dependent multivariate statistical methods with respect to thromboembolic events, anticoagulant-related hemorrhage, valve failure, fatal valve failure, all valve-related morbidity and mortality, necessity for reoperation, and late survival. Many patient-related factors were significant predictors of the probability of certain patient groups for sustaining these valve-related complications. Hence, comparisons of results of valve performance from different institutions may be misleading unless patient populations are comparable.

Adolescent↗
PubMed1986

Naturally corrected double-outlet right ventricle with biventricular outflow tract obstruction.

A 5-year-old girl had presyncopal episodes associated with exertion. Diagnostic evaluation revealed a combination of congenital abnormalities: double-outlet right ventricle with apparent "natural correction" of a large subaortic ventricular septal defect and severe biventricular outflow tract obstruction. Intraoperative and postoperative studies confirmed satisfactory relief of the biventricular outflow tract obstruction.

Child, Preschool↗
PubMed1986

Timing of abnormal interventricular septal motion after cardiopulmonary bypass operations. Lack of injury proved by preoperative, intraoperative, and postoperative echocardiography.

Abnormal interventricular septal motion after cardiopulmonary bypass is a widely known occurrence. The cause and exact timing of this phenomenon remain unclear. We have studied 21 patients prospectively with preoperative, intraoperative, and postoperative two-dimensional and M-mode echocardiograms. Intraoperative studies were obtained with the pericardium closed and open and after completion of procedures performed with cardiopulmonary bypass. Fourteen patients had coronary artery bypass graft operations alone. Six patients had valve replacement with or without coronary bypass, and one patient had removal of a left atrial myxoma. All patients had normal interventricular septal motion before the operation, and none had abnormal septal motion intraoperatively. Four to eight days postoperatively, the septum still thickened normally in all patients, with five patients having normal, nine patients abnormal, and seven patients paradoxical interventricular septal motion. Studies in 11 patients 1 to 4 months postoperatively showed no change from the early postoperative study. The pericardium was left open postoperatively in all patients. Six patients were studied a few hours after sternal closure and all had abnormal interventricular septal motion. We conclude that abnormal interventricular septal motion after cardiac operations is not due to injury of the septum, adhesion formation, or loss of pericardial constraint. Closure of the chest wall itself, with the pericardium left open, is associated with this abnormality.

Cardiomyopathies↗
PubMed1985

Acute traumatic midbrain hemorrhage.

A syndrome resulting from traumatic midbrain hemorrhage is described in 5 patients, 3 of whom had intracranial pressure measurements and 2 of whom had pathological examinations. The major clinical signs, evident immediately after injury, are coma, dilated (4 to 8 mm diameter) pupils that are fixed to light and dark, diminished limb tone, and impaired horizontal eye movements. The hemorrhages are single and linear or oval-shaped in the midsagittal rostral midbrain, extending several millimeters bilaterally. The appearance of the hematoma may be delayed on computed tomographic scanning, but early abnormalities of wave V of the brainstem auditory evoked potentials aid in diagnosis. Pathological features suggest that secondary brainstem distortion occurred soon after injury, perhaps resulting from a transiently raised intracranial pressure, but shearing injuries caused by acceleration-deceleration forces were also found.

Accidents, Traffic↗
PubMed1985

Structural requirements for specific inhibition of microsomal aminopeptidase by mercaptoamines.

L-Leucinthiol, a synthetic derivative of mercaptoethylamine with a hydrophobic side chain, was recently reported to be a potent inhibitor of microsomal aminopeptidase. The structural features necessary for interaction of mercaptoamines with this enzyme have now been explored more systematically. Optimal binding requires a primary amine linked to the mercapto group via two carbon atoms. Only a substituent with L-configuration at the 1 position increased the affinity toward the enzyme. The high degree of specificity and other evidence suggest that the mode of binding of these inhibitors is similar to that of substrates. Comparison of leucinthiol with other amino compounds suggest that the mercapto group makes a much greater contribution to the binding than the hydrophobic side chain. L-Leucinthiol is fairly specific for aminopeptidase although some inhibition of thermolysin and carboxypeptidase A is observed.

Aminopeptidases↗
PubMed1985

Valve replacement in patients with native valve endocarditis: what really determines operative outcome?

The influence of 27 variables on operative mortality and late complications (defined as residual or recurrent endocarditis or late bland periprosthetic leak) was determined using discriminant analysis for 108 patients undergoing valve replacement for native valve endocarditis at Stanford University Medical Center from March, 1964, to January, 1983. Congestive heart failure was the indication for valve replacement in 86% of patients. Aortic valve replacement was required in 68% and mitral valve replacement, in 26%. Patients were arbitrarily defined as having active (58%) or healed (42%) endocarditis. Follow-up included 515 patient-years and extended to a maximum of 19 years. Operative mortality was 15 +/- 4%, and 17 patients had late complications (linearized rate, 3.3% per patient-year). Seven variables were significantly related to operative mortality in the univariate analysis, but only organism (Staphylococcus aureus versus all others, p = 0.0302) was a significant independent predictor of operative mortality. For late complications, only 2 of 7 significant univariate covariates proved to be significant independent determinants: organisms on valve culture or gram stain and the presence of annular abscess. Patients with S. aureus endocarditis not showing prompt response to antibiotic treatment must be considered for early operation. Similarly, timely operative intervention for patients with annular abscess will be essential in decreasing late valve infections and perivalvular leaks.

Actuarial Analysis↗
PubMed1985

Phrenic nerve injury complicating closed cardiovascular surgical procedures for congenital heart disease.

Phrenic nerve injury (PNI) with resulting hemidiaphragmatic paralysis occurred in 19 (2.1 +/- 0.5%) of 891 closed cardiac surgical procedures during a twenty-three-year period. Diagnosis was confirmed by standard radiographic criteria. Phrenic nerve injury was most commonly noted following systemic-pulmonary artery anastomosis, ligation of persistent ductus arteriosus plus pulmonary artery banding, and atrial septectomy. Most patients were managed conservatively (nasotracheal or orotracheal intubation and positive end-expiratory pressure). Although no deaths were a direct result of PNI, major complications occurred in 15 of the 19 instances of PNI (79% +/- 10%). The serious morbidity and the hospital costs associated with this complication, however, underscore the cardinal importance of prevention. If injury does occur, early surgical intervention (diaphragmatic plication) in very young infants may reduce the attendant morbidity, but the complete role of diaphragmatic plication remains to be defined.

Adolescent↗
PubMed1985

Flow determination using computed tomography: application to aortic dissection. Part II.

Dynamic CT is not only useful in imaging an aortic dissection but may provide additional information concerning the hemodynamic significance of differing flow patterns in the false channel compared with the true channel. Once validated, the computed tomographic (CT) method of flow determination (See Part I) was applied to an experimental animal model with a surgically created aortic dissection. Good correlation was obtained for the flow estimates of cardiac output derived for the true and false channel (r = .82). The shapes of the curves, however, were distinct, reflecting different flow patterns for the true and false channels. Curve parameters, such as peak CT number (P = .0001), variance (P = .006), and, in particular, the number of mixers (a parameter used to quantify the degree of mixing) (P = .0001), demonstrated significant differences between the two channels of the dissection. The curve parameters derived can therefore be used to differentiate the true and false channels and may then predict the long-term outcome of the false channel, and the aortic branches derived from it.

Aortic Dissection↗
PubMed1985

Independence of left ventricular pressure-volume ratio from preload in man early after coronary artery bypass graft surgery.

The response of the maximum value of the left ventricular pressure-volume ratio to preload augmentation by blood or plasma expanders was studied in 11 patients during the first 24 hr after coronary artery bypass graft surgery. Increasing the mean left atrial pressure from 10 to 15 and 20 mm Hg resulted in no change in the maximum pressure-volume ratio in the group as a whole. In certain individual patients, however, the maximum pressure-volume ratio changed with volume infusion, and these changes were accompanied by simultaneous changes in afterload. The observed changes in pressure-volume ratio were in the same direction as the changes in afterload (systolic pressure), suggesting a dependence of maximum pressure-volume ratio on afterload. These results show that the maximum pressure-volume ratio is independent of preload in the first 24 hr after coronary artery bypass graft surgery with the pericardium open; thus the maximum pressure-volume ratio is a useful index of postoperative left ventricular function when afterload is unchanged. However, because this ratio (a single-point assessment of the pressure-volume relationship) may not be a good estimate of Emax, we recommend a more complete determination of the locus of the "upper left corners" of the pressure-volume loops for measurement of Emax to provide a more accurate indicator of the myocardial contractile state.

Adult↗
PubMed1985

Bronchoalveolar lavage in ponies with recurrent airway obstruction (heaves).

We performed bronchoalveolar lavage (BAL) in 2 groups of ponies. Principal ponies had a history of heaves, a disease characterized by recurrent airway obstruction and airway hyperreactivity when ponies are housed in a barn and fed hay; control ponies had no history of airway obstruction. Ponies were paired (principal and control), and BAL was performed after 2 months of being pastured when principal ponies were in clinical remission (Period A), after barn housing when principal ponies had acute airway obstruction (Period B), and after a 1- and a 2-wk recovery phase of pasture grazing (Periods C and D). At Periods A, C, and D, white blood cell counts and immunoglobulin/albumin ratios in peripheral blood and BAL fluid of principal and control animals did not differ. Peripheral blood white cell counts and immunoglobulin/albumin ratios were unaffected by barn exposure and return to pasture. However, at Period B, neutrophil numbers in the BAL fluid were increased in the principal but not in the control animals. The IgG/albumin ratio of the principal animals increased at Period C. We conclude that in ponies with a history of heaves, barn exposure results in increased neutrophils in BAL fluid. In this pony model of lung disease, pulmonary leukostasis follows a time course similar to that of airway obstruction and airway hyperreactivity.

Albumins↗
PubMed1985

Chronic encephalitis possibly due to herpes simplex virus: two cases.

Two patients had clinical findings of encephalopathy that progressed in 4 to 5 months. One patient had headache, fatigue, lethargy, hemiparesis, and a seizure. The second patient had only forgetfulness, confusion, and lethargy without focal signs. Herpes simplex virus was grown from brain biopsy in the first patient and from CSF in the second patient. These cases suggest that herpes simplex virus caused the encephalitis and that it should be considered in the differential diagnosis of chronic encephalopathy.

Adolescent↗
PubMed1985

Estrogen and progestin binding by cytosolic and nuclear fractions of human meningiomas.

Frozen tissue samples were obtained from meningiomas in 42 patients. Both cytosolic and nuclear fractions were tested for estradiol and progestin binding using equilibrium binding assays. The results were correlated with the age of the patient and the histological type and cellular density of the tumor. Cytosolic estradiol binding was noted in 25 (60%) of 42 tumors, with eight (19%) of the 42 having levels over 10 femtomoles (fM)/mg protein. Nuclear estradiol binding was detected in 16 (57%) of 28 tumors, with six (21%) of the 28 having levels over 10 fM/mg protein. Cytosolic progestin binding was noted in 16 (73%) of 22 samples, with levels in nine (41%) of 22 being greater than 10 fM/mg protein. There was no correlation between the level of cytoplasmic progestin binding and either the level of cytoplasmic estradiol binding or the level of nuclear estradiol binding. In several specimens, level of cytoplasmic progestin binding in excess of 100 fM/mg protein were found in tissues demonstrating little or no estradiol binding by either the nucleus or the cytosol. This discrepancy differs from the situation found in other hormonally responsive tissues such as breast or uterus, and suggests either a possible derangement of the normal cellular hormonal control mechanism or that the measured hormone binder is a molecule other than a classical hormone receptor.

Adult↗
PubMed1985

Benign metastasizing meningioma. Case report.

A patient with a histologically benign intracranial meningioma was found, at the time of initial presentation, also to have a pulmonary tumor. Fine-needle aspiration cytology of the lung mass was consistent with metastatic meningioma. When resected, the pulmonary tumor was found to be histologically benign. The patient has remained well and disease-free for 28 months. Only four other patients with apparently benign metastasizing meningiomas have been described previously.

Humans↗
PubMed1985

Neuro-ophthalmological findings with neuropathological correlation in bilateral thalamic-mesencephalic infarction.

A 91-year-old man presented with the sudden onset of coma, vertical gaze paresis, and transient disturbance of horizontal gaze, with fixed but unequal pupils. Both cranial computed tomography and postmortem study documented infarction of the paramedian thalamus bilaterally and of the ventral mesencephalon, accounted for by presumably embolic occlusion of a single artery. This artery arose as an unpaired perforating artery originating from the proximal segment of one posterior cerebral artery and thus conformed to the variant anatomic configuration associated with such infarcts as described by Percheron.

Aged↗
PubMed1985

Effect of early postoperative volume loading on left ventricular systolic function (including left ventricular ejection fraction determined by myocardial marker) after myocardial revascularization.

The effects of early volume loading in terms of isovolumetric-phase and ejection-phase indexes of left ventricular systolic function were studied in 12 patients 5 hr after myocardial revascularization, with myocardial markers used to measure left ventricular volume directly and with simultaneous transmural left ventricular pressure measurements by micromanometers. Volume loading (increasing transmural left ventricular end-diastolic pressure from 11 +/- 4 to 15 +/- 5 mm Hg) induced a significant 14% increase in left ventricular end-diastolic volume index (LVEDVI), which was associated (as expected) with significant (p less than .005) augmentation of stroke work (+26%), left ventricular pressure-volume loop area (+35%), and stroke volume index (+22%) and with increments in left ventricular dP/dt and mean velocity of circumferential fiber shortening despite a simultaneous increase in left ventricular afterload. In contrast to previous radionuclide studies, however, left ventricular ejection fraction increased significantly (+9%) and the left ventricular end-systolic pressure-volume ratio did not fall. The relative change in ejection fraction was directly proportional to the increment in LVEDVI (r = .54, p = .03) and inversely related to the change in left ventricular end-systolic volume index (r = -.71, p = .0005). Patients who demonstrated a small or no increase in ejection fraction generally had a larger simultaneous increase in afterload, but one patient exhibited exhaustion of preload reserve. Ejection fraction, as an ejection-phase index of left ventricular performance, is highly dependent on afterload; therefore, interpretation of postoperative changes in ejection fraction must be undertaken only with strict caution.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac Output↗
PubMed1985

Acute and chronic aortic dissections--determinants of long-term outcome for operative survivors.

A total of 135 survivors of surgical treatment of aortic dissection was followed for up to 15 years after surgery. Actuarial survival rates were 82 +/- 4% at 5 years and 64 +/- 6% at 10 years. There were no significant differences in long-term survival rates of patients in four subsets based on type and acuity of dissections. The incidence of late reoperation (dissection-related) was 13 +/- 4% at 5 years and 23 +/- 6% at 10 years; again, there was no significant difference among patients with different types or acuity of dissection. Multiple variables were investigated by multivariate discriminant analysis. Significant independent risk factors for late death included stroke, chronic renal dysfunction, remote myocardial infarction, and operation in the early years of this study. Younger age, site of intimal tear (arch), and cardiac tamponade portended a significantly higher likelihood of late reoperation. Except for stroke, no complication of the dissection or intraoperative factor significantly influenced late survival. Patients in whom the intimal tear was located in the aortic arch had the highest probability of late reoperation. Thus, dissection type, acuity, and distal extent, whether or not the tear was resected or concomitant aortic valve replacement performed, and a host of patient-related characteristics had no significant influence on the generally excellent long-term prognosis after surgical treatment. Indefinite surveillance of the remaining natural aorta is imperative (with reoperation when indicated) to attain such results.

Actuarial Analysis↗
PubMed1985

Surgical repair of tetralogy of Fallot. Long-term follow-up with particular emphasis on late death and reoperation.

Early and late results in 309 patients undergoing repair of tetralogy of Fallot between 1960 and 1982 were analyzed with respect to independent determinants of operative mortality, late reoperation, and late death. Follow-up extended to 22 years and totaled 2,743 patient-years. The operative mortality rate was 4.9% +/- 1.3%. Multivariate logistic regression analysis revealed that only young age, long cardiopulmonary bypass time, and (probably) extent of right ventricular outflow tract patch were independent significant determinants of operative mortality. Patients who required a transannular right ventricular outflow tract patch and those who underwent repair without any outflow tract patch were at higher risk than those who received a separate right ventricular and/or pulmonary artery patch. The long-term results were highly satisfactory: Only 15% +/- 3% of patients required reoperation 13 years postoperatively, and 85% +/- 4% of discharged patients were alive 16 years later. Time-dependent linear stepwise multivariate discriminant analysis showed that extent of right ventricular outflow tract patch (transannular greater than none greater than right ventricular and/or [separate] pulmonary arterial), longer ischemic arrest time, previous palliative shunt, and primary suture closure of the ventricular septal defect were the only covariates that independently portended a higher likelihood of reoperation. Similarly, only older age, absence of hypoxic spells, and reoperation were significantly and independently related to the probability of late death. The results of these analyses demonstrate that intracardiac repair of tetralogy is a durable procedure for upwards of 20 years; however, high-risk subsets of patients can be identified in terms of operative mortality, reoperation, and late death. Thus, there is still a need for improvement, particularly future research devoted to better understanding of the electrophysiological mechanisms responsible for arrhythmias, electrosurgical and medical arrhythmia therapy, and right and left ventricular mechanics after repair of tetralogy of Fallot.

Actuarial Analysis↗