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Biomedical subjects

D C Miller

Publications and source records attributed to D C Miller.

At least 379 records · Page 21Linked to original sources
PubMed1980

Clinical durability of the Hancock porcine bioprosthetic valve.

The principal feature of the Hancock xenograft bioprosthesis which remains to be completely defined is long-term durability. This report provides extended data regarding valve durability derived from a data base of 1,407 patients (707 aortic [AVR] and 700 mitral [MVR] replacements) who received Hancock bioprostheses between 1971 and 1979; cumulative duration of follow-up was 1,732 patient-years for AVR and 1,843 for MVR patients, with a maximum follow-up duration of 8.4 years. One hundred seventy-nine patients were followed for more than 5 years and 67 for more than 6 years. Valve failure was defined on the basis of one or more of the following criteria: (1) postoperative development of a new regurgitant murmur, (2) thrombotic valvular occlusion, (3) infective endocarditis resulting in reoperation or death, and (4) hemodynamic valvular dysfunction confirmed by catheterization and resulting in reoperation or death. Twenty-one such failures occurred among all AVR patients and 23 among all MVR patients. The actuarial probability of freedom from valve failure (all causes) was 95.4% +/- 1.2% (+/- SEM) for adult AVR patients 5 years postoperatively and 90.9% +/- 2.6% for adult MVR patients 6 years postoperatively. The probability of freedom from primary tissue failure in adults was 99% +/- 1% in AVR patients at 5 years and 94.3% +/- 2.4% in MVR patients at 6 years. The linearized incidence of primary tissue failure in children (< 15 years old) was 9.8% per patient-year (combined AVR and MVR patients), compared to 0.2% per patient-year among all adult patients in the analysis. The combined actuarial incidence of primary tissue failure among adults with AVR and MVR was 98.6% +/- 0.7% at 5 years and 94.2% +/- 2.3% at 6 years; thus there appears to be a slight acceleration in the rate of valve tissue failure between 5 and 6 years after operation. The incidence of failure, however, remains acceptably low through 6 years of follow-up, and continued clinical use of the xenograft bioprosthesis seems warranted.

Actuarial Analysis↗
PubMed1979

Target velocity signals of visual tracking in vermal Purkinje cells of the monkey.

Discharges of Purkinje cells were recorded from the vermis, lobules VI and VII, of a monkey trained to track a visual target. When the monkey tracked a sinusoidally oscillating target, cellular activity changes in phase with the velocity signal of the eye movement. When the monkey fixated a stationary point, almost identical modulation in activity occurred, reflecting the velocity signal of the motion of the retinal image of the target. The data suggest that the vermis participates in the control of smooth pursuit eye movements by providing the oculomotor system with the actual target velocity information which is the sum of eye velocity and retinal image velocity signals.

Action Potentials↗
PubMed1979

Aortic and mitral prosthetic valve reoperations: early and late results.

A total of 232 valvular reoperations (123 mitral valve reoperations [RMVR] and 109 aortic valve reoperations [RAVR] were performed in 194 patients with previously implanted prosthetic valves. Early mortality was 10% (12/123) for the RMVR subgroup and 14% (15/109) for the RAVR subgroup (P = NS). Late mortality was 16% (18/111) for the RMVR subgroup and 25% (23/94) for the RAVR subgroup (P = NS). Patients with prosthetic endocarditis or prosthetic stenosis constituted higher-risk subpopulations. Principal determinants of both operative mortality and late attrition were preoperative cardiac functional status and the nature of the pathology mandating valve replacement. Early prosthetic valve replacement is advocated to correct hemodynamic abnormalities before advanced ventricular decompensation ensues, especially when prosthetic valvular endocarditis or prosthetic stenosis exists.

Aortic Valve↗
PubMed1979

Late right heart reconstruction following repair of tetralogy of Fallot.

Twenty-two symptomatic patients underwent a total of 28 reoperative procedures after initial surgical repair of tetralogy of Fallot. Sixteen of the patients were considered to have unfavorable anatomy of the right ventricular outflow tract (RVOT) or pulmonary artery at the time of initial repair. Pulmonary or tricuspid valve replacement, or replacement of both valves, utilizing a xenograft bioprosthesis was performed in 1 of the 22 initial repairs, 7 of the 22 first reoperations, and 5 of the 6 second reoperations. Ultimately, 14 patients received transannular RVOT patches. The interval between the first and second reoperations for 6 patients who required 2 late reconstructive procedures was 5.8 years. No operative deaths occurred. There were 2 late deaths (1 sudden and 1 due to aspiration). Actuarial survival probability (+/- standard error of the mean) 16 years after initial repair was 72 +/- 21%. Eighteen of the 20 current survivors in the present series are completely asymptomatic without physical restrictions; the other 2 are considered to be in New York Heart Association Functional Class II. No xenograft bioprosthetic dysfunction has occurred to date, but cumulative valve follow-up is limited (13 patient-years). In selected patients, earlier pulmonary or tricuspid valve replacement or replacement of both of these valves can provide some degree of protection against recurrent deterioration.

Adolescent↗
PubMed1979

Fate of the false lumen following surgical repair of aortic dissections: an angiographic study.

Postoperative angiography was performed in 27 patients who had surgical repair for aortic dissections. The ascending aorta was involved in 22 dissections (Type A), while in five dissections it was uninvolved (Type B). Findings were assessed between two weeks and 13 years postoperatively. Despite the primary surgical objective to abolish flow in the false lumen, the majority of patients, whether symptomatic or not, continued to harbor patent distal false channels. In certain cases, one or more vital aortic branches were perfused solely by the false lumen. Initial postoperative angiography is indicated for determined surgical results as well as the functional significance of late angiographic findings, should symptoms recur. Further extension of the initial dissection, redissection, or enlargement of localized saccular aneurysms may mandate late reoperation. These conditions manifest themselves by pain, aortic regurgitation, neurological sequelae, or compromise of blood flow to a vital organ or extremity.

Aortic Dissection↗
PubMed1979

Hepatitis risk in cardiac surgery patients receiving factor IX concentrates.

Experience with the clinical use and hepatitis risks of factor IX concentrate (Proplex) in cardiac surgical patients is presented in this report. Seventy-five patients received the concentrate for severe intraoperative or postoperative hemorrhage and 75 patients constituted matched controls. The incidence of probable type B viral hepatitis in patients receiving factor IX concentrate was 13.8 percent (four of 29) versus zero percent (zero of 29) in control patients (difference not significant). However, there was a greater incidence (p less than 0.05) of anti-HBs in patients receiving factor IX concentrate as compared to control subjects. No hepatitis-associated deaths or major morbidity were noted in these patients. It is confirmed that factor IX concentrate carries an associated significant risk of hepatitis. However, its use is justified in certain severe, acquired coagulopathies in which conventional platelet and fresh-frozen plasma therapy is inadequate.

California↗
PubMed1979

Operative treatment of aortic dissections. Experience with 125 patients over a sixteen-year period.

An unselected, consecutive cohort of 125 patients underwent operative repair of acute and chronic aortic dissections with tubular graft interposition over a 16 year span. The absence of remote geographical referral biases and the unselected nature of this series provided a patient population that was representative of the disease process (as assessed heretofore only from autopsy series). Furthermore, this enabled high-risk subsets to be defined by retrospective analysis. Patients were classified according to whether the ascending aorta was involved (type A with involvement, type B without), irrespective of the site of intimal tear, and according to age of the dissection: Fifty-three patients had acute type A (Ac-A), 29 had chronic type A (Ch-A), 20 had acute type B (Ac-B), and 23 had chronic type B (Ch-B) dissections. Fourteen percent (17/125) of the dissections had ruptured. Concomitant aortic valve replacement (AVR) was performed in 11% (6/53) for Ac-A cases and 38% (11/29) of the Ch-A cases. A total of 391 patient-years of follow-up was analyzed; follow-up averaged 4.5 years and extended to 13.7 years. Over-all operative mortality rate was 34% (18/53) for Ac-A, 14% (4/29) for Ch-A, 45% (9/20) for Ac-B, and 22% (5/23) for Ch-B; during the most recent 5 year interval these figures were lower: 27%, 8%, 20%, and 20%, respectively, N = 50. Multiple preoperative variables were found to correlate significantly with both operative death and long-term survival. Operative survivors generally experienced satisfactory functional benefit. Late attrition averaged 8% per year; 61% of all late deaths were related to cardiac or cerebral causes. Over-all actuarial survival (+/- SEM) for the entire cohort was 54% +/- 5% at 5 years and 26% +/- 7% at 10 years; for the 89 patients surviving operation, these figures were 76% +/- 5% and 37% +/- 10%, respectively. No significant differences in long-term survival were evident between the different subgroups. Whether the primary intimal tear had been resected or concomitant AVR had been performed had no statistically significant bearing on operative mortality, functional result, necessity for late reoperation, or late attrition. The long-term "natural" history of surgically treated patients with aortic dissections, as defined in this study, should facilitate comparison with other treatment modalities. Results of the present analysis support immediate operative intervention for patients with Ac-A dissections and probably for those with Ac-B dissections. Additionally, surgical treatment of patients with symptomatic or enlarging Ch-A and Ch-B dissections provides satisfactory rehabilitation and long-term survival. Finally, we re-emphasize our recommendation for simplified classification of aortic dissections, based solely upon the presence or absence of ascending aortic involvement. Pathophysiology and expected biologic behavior pivot on this feature, and appropriate clinical strategy can thereby be defined.

Adult↗
PubMed1978

A modern view of the surgical treatment of peripheral arterial disease.

As life expectancy increases, more patients will harbor atherosclerotic conditions that portend disability and death. Due basically to a communication gap, sizable numbers of these patients who stand to benefit from vascular reconstruction are not being referred or are being referred too late to vascular surgeons. Vascular surgery currently can save limbs, extend productivity and life expectancy, ameliorate hypertension, and prevent stroke more reliably and with less risk than ever before. As the subspeciality of vascular surgery has matured, has incorporated additional fellowship training, and now approaches potential recognition in some yet to be determined form by The American Board of Surgery, it is incumbent on general physicians and vascular surgeons alike to develop appropriate channels that can transmit clinical concepts, educational information, and clinical results, as well as refer patients.

Abdomen↗
PubMed1978

Localized tamponade of the right atrium and right ventricle: induction of intracardiac right-to-left shunting after the use of a Gott shunt.

After repair of a traumatic tear of the descending aorta, using a Gott shunt between the left ventricle and the distal descending aorta, a patient was readmitted with profound postural cyanosis and dyspnea. Catheterization showed right-to-left shunting at the atrial level caused by extrinsic deformation of the right atrium and right ventricle. Sternotomy showed selective pericardial tamponade on the right side of the heart caused by a localized collection of organizing thrombus and old blood. The previously unsuspected large patent foramen ovale was closed. This complication represents a form of iatrogenic cyanosis tardice and is thought to be attributable to the method of shunting used during the first operation. Moreover, this complication should be easily preventable if the pooled blood and clot in the most dependent portion of the pericardial cavity is adequately evacuated.

Adult↗
PubMed1978

Recurrent mediastinal bronchogenic cyst. Cause of bronchial obstruction and compression of superior vena cava and pulmonary artery.

The recurrence of a benign mediastinal bronchogenic cyst 20 years after partial excision precipitated potentially serious vascular and pulmonary complications. Aggressive total surgical excision should be feasible in the majority of cases. An approach via a median sternotomy offers distinct advantages in certain cases and should be considered. Computerized axial tomographic scanning promises to provide improved definition of mediastinal anatomic features and should be a valuable noninvasive diagnostic method in selected cases.

Bronchial Diseases↗
PubMed1978

Impact of simultaneous myocardial revascularization on operative risk, functional result, and survival following mitral valve replacement.

A cohort of 282 patients who underwent mitral valve replacement with a xenograft bioprosthesis was strictly segregated according to etiology of mitral dysfunction and analyzed regarding the impact of arteriographic coronary artery disease (CAD) and concomitant coronary artery bypass grafting (CABG) on operative risk, functional result, and survival. CAD was present in 21% of the 122 patients with predominant mitral stenosis (MS) and 59% of the 155 patients with mitral regurgitation (MR); moreover, discordance between the presence of angina and anatomic CAD was found in 27% (33 of 122) of the MS subgroup and 36% (56 of 155) of the MR subgroup. Etiology of the valvular dysfunction was rheumatic in 148 patients, myxomatous degeneration in 83, and ischemic in 32. Within these subgroups, 41 patients (27%), 40 patients (48%), and 32 patients (100%), respectively, had CAD. Of those patients with CAD, 85% of the rheumatic subgroup, 90% of the degenerative subgroup, and 81% of the ischemic subgroup underwent concomitant CABG at the time of valve replacement. Within each subgroup no statistically significant (P greater than 0.05) differences in operative mortality rate, perioperative myocardial infarction rate, incidence of late angina or late infarction, or late actuarial survival were evident when compared on the basis of CAD, and/or CABG, with one exception. The exception was the 10% incidence of perioperative myocardial infarction in the rheumatic subgrohp with coronary disease versus 2% in the rheumatic subgroup without coronary disease (P = 0.05). Within the time constraints of this study (mean follow-up = 2.3 years; maximum follow-up = 5.9 years), these results support simultaneous MVR and CABG when hemodynamically appreciable CAD is found. Moreover, the overall 43% incidence of arteriographic CAD warrants routine coronary angiography in most adults undergoing preoperative catheterization for mitral valvular disease.

Adolescent↗
PubMed1978

Treatment of obesity in family practice.

This paper describes the experience of a senior family practice resident in managing obesity using behavior modification techniques. Weight reduction was begun and continued by 9 of 32 identified obese patients. Patients who were successful in losing weight were those who kept accurate intake diaries, returned for follow-up, and had made prior attempts at weight loss. Patients who were unsuccessful in losing weight were those who kept incomplete intake diaries, had no continuing physician-patient relationship with the investigator, and had made no prior attempts at weight loss. The method management described allowed efficient use of physician time so that the time required was well within the limits set by a busy family practice setting.

Adolescent↗