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Biomedical subjects

G L Grunkemeier

Publications and source records attributed to G L Grunkemeier.

At least 55 records · Page 3Linked to original sources
PubMed1996

Clinical experience with the Björk-Shiley Delrin tilting disc heart valve.

BACKGROUND AND AIMS OF THE STUDY: The Björk-Shiley Delrin (BSD) disc heart valve was first used clinically in 1969. We estimate that as of January 1996, no more than 7,000 patients may be alive with the BSD valve. METHODS: We reviewed the published reports of clinical experience with the BSD valve in addition to the records regarding BSD valves returned to Shiley Incorporated. Measurements of the maximum radial gap, static leak flow rate and inspection of the Delrin disc for wear were obtained. RESULTS AND CONCLUSIONS: We concluded that clinically important regurgitation, due to disc wear, was rare but may occur. Larger prostheses, in general, showed greater disc wear than smaller sized valves. There were no reports of fracture of the Delrin disc. Two cases of inlet strut fracture were reported. Late disc embolization, in the absence of inlet strut fracture, occurred in two patients following surgical manipulation. Disc wear did not cause abnormal valve opening or closing although increased regurgitation may occur.

Anticoagulants↗
PubMed1995

Up to thirty-year survival after aortic valve replacement in the small aortic root.

Aortic valve replacement (AVR) in the small aortic root has been reported to be associated with obstruction of left ventricular output. This study was designed to investigate the determinants of long-term survival after the implantation of small size prostheses. From September 1961 to December 1993, 2,977 patients underwent isolated aortic valve replacement at our institution. Of these patients, 447 who were older than 18 years received small size (21 mm or less) prostheses. Long-term survival was investigated in the 404 patients who survived operation (more than 30 days) with 92% follow-up completeness (mean +/- deviation 7.1 +/- 6.4; maximum, 31 years). The age was younger than 50 years in 62 patients, 50 to 59 years in 60, 60 to 69 years in 99, 70 to 79 years in 138, and 80 to 94 years in 45; 67% were men. Thirty patients (7%) had previous AVR. Prosthesis usage included early Starr-Edwards models in 130 (32%), current Starr-Edwards (model 1260 since 1969) in 50 (12%), Carpentier-Edwards (porcine) in 113 (28%), and other prostheses in 111 patients (27%). One hundred sixteen patients (26%) had concomitant coronary artery bypass grafting (CABG). Eleven variables (age divided as above, sex, preoperative functional class, body surface area [BSA], small BSA [less than 1.6, 1.7, 1.8, or 1.9 m2], period of operation, previous AVR, type of prosthesis, size of prosthesis, concomitant CABG, and re-replacement) were investigated with regard to the long-term survival by the Kaplan-Meier method, and age, concomitant CABG, and type of prosthesis were significant.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1995

Double-valve replacement with Medtronic-Hall or St. Jude valve.

To define better the performance of the bileaflet St. Jude and the tilting-disc Medtronic-Hall valves, we retrospectively analyzed 122 patients (St. Jude, 80 patients; Medtronic-Hall, 42 patients) who received simultaneous aortic and mitral replacement from May 1984 until June 1994. The two groups were not different with respect to preoperative clinical and hemodynamic parameters and New York Heart Association functional class. The hospital mortality and late mortality were not significantly different. Risk analysis identified advanced age and previous myocardial revascularization as predictors of operative death. Follow-up was complete in 96 of 103 hospital survivors (93%) and was similar in both groups. The actuarial survival, linearized rates of valve-related complications, and actuarial freedom from valve-related complications were similar in both cohorts. The presence of coronary artery disease negatively influenced the actuarial survival after simultaneous aortic and mitral valve replacement. Postoperative New York Heart Association functional class was not significantly different in either group. These data indicate that the Medtronic-Hall and St. Jude prostheses are not significantly different with respect to their clinical performance and valve-related complications for simultaneous double-valve replacement.

Aortic Valve↗
PubMed1995

Passive surveillance of heart valve devices: Björk-Shiley outlet strut fracture rates.

The Björk-Shiley Convexo-Concave heart valve has a mechanical failure mode called outlet strut fracture (OSF). Previous analyses have found that the hazard function for OSF is constant over time. This article uses the valve manufacturers implant database to examine the shape of the hazard function over time, employing a previously developed model to impute patient survival times. Decisions about patient management (e.g., elective explant) are based on projecting this risk into the future. An analysis that incorporates the decrement of patients at risk due to death and explant provides estimates of the actual occurrences of OSF over calendar time.

Adult↗
PubMed1995

Measuring the success of treatment in patient terms.

Measuring the success of major surgeries such as total hip and total knee replacement is important for both case selection and public policy. Patients, purchasers, and practitioners must choose among clinical scoring systems, health status measures, and patient satisfaction ratings to monitor performance and ensure appropriate use of costly procedures. The present study compares results from the Medical Outcomes Study Short Form 36 (SF-36) Health Status Survey and clinical scoring systems to direct patient ratings of success. Data come from a study of 128 total knee-replacement procedure and 211 total hip replacements. Analyses indicate that for both hip and knee patients, success is related closely to posttreatment physical function and bodily pain. Patient ratings of success also are related to the clinical scores used by physicians. Success is related less to change from pretreatment function for knee patients than for hip patients. Although patient ratings of success are generally consistent with other outcome measures, their relationship to patient expectations, satisfaction, and attributions need to be understood before they can become a useful tool for performance monitoring and case selection.

Activities of Daily Living↗
PubMed1995

Comparative assessment of bioprosthesis durability in the aortic position.

Published durability results of porcine and pericardial bioprostheses in the aortic position have been reviewed for the purpose of a qualitative comparison between these valve types, and also with previously reviewed series of homograft valves. Porcine bioprostheses exhibit a wide range of failure curves, with a characteristic Weibull-shaped pattern. Patient characteristics must account for the majority of differences seen among the series. Newer series generally contain older patients and have better results. A second generation pericardial valve has distinctly better durability than a previously discontinued pericardial model, and appears to be as durable as that of the best porcine valve series. Homograft valves using cold antibiotic storage have durability results approximately equal to porcine valves, but with younger patients on the average. The results with cryopreserved valves may be comparable, but insufficient long term information is available. To make these qualitative comparisons quantitative would require a formal analysis which takes age and other patient-related characteristics into account.

Aortic Valve↗
PubMed1994

Actuarial versus actual risk of porcine structural valve deterioration.

Actuarial analysis, using nonparametric (e.g., life table or Kaplan-Meier) or parametric (statistical modeling) methods, is used to describe and compare survival probabilities by allowing for partial survival times (censoring). Although devised to describe freedom from death, this method has been extended to nonfatal complications, such as freedom from tissue valve failure. However, the risk described for nonfatal events is that which a patient would experience provided he were immortal. And patients with valve disease have a relatively high risk of dying, generating the question: "What is the chance the valve will fail before the patient dies?" To answer this more practical (for individual patient management and population resource allocation) question requires an estimate of what we call actual failure, that is, the percentage of patients whose valve will actually fail before they die. This risk is less than the risk which the usual actuarial curve describes. This difference increases with patient age, because older patients have a lower risk of tissue failure and a higher risk of death than younger patients.

Actuarial Analysis↗
PubMed1994

Comparison of structural valve failure among different 'models' of homograft valves.

Aortic homograft valves are accepted as excellent valve substitutes in the aortic position. Compared to stented bioprostheses, they are considered to have better hemodynamics and a zero or negligible thrombogenicity. Their perceived major single shortcoming is limited durability, but there is apparent broad variation within published data in this respect. Study of the relevant literature reveals important differences between procurement, sterilization and preservation of the individual series refuting any attempt at making a scientifically valid comparison of overall performances. Surgical method and patient selection are further sources of variation among reported long term results. Nevertheless, it appears that (a) cryopreservation produces results at least as good as those of other preservation methods, and (b) the worst results are those of series with the longest follow up. However, the good results with cryopreserved valves are reported in series with limited length of follow up. Because of the many variable factors associated with the use of homograft valves, a comprehensive set of definitions should be introduced, accepted and adhered to in reporting results.

Aortic Valve↗
PubMed1994

Sample size requirements for evaluating heart valves with constant risk events.

A method is described for computing sample size requirements for a clinical study of a new heart valve, according to the guidance document recently revised by the FDA. The FDA requirements specify a one-sample hypothesis test in which the complication rates for the study valve are compared to fixed values determined from previous experience with approved devices. These values, which can differ for different complications and for mechanical or tissue valve types, are called OPC's (Objective Performance Criteria). The method described, using the Poisson distribution, provides a simple formula for computing the valve-years required corresponding to any OPC. At the OPC level required by the FDA guidelines (1.2%/year), the minimum follow-up necessary is about 800 valve-years.

Guidelines as Topic↗
PubMed1993

Survival 15 to 20 years after coronary bypass surgery for angina.

OBJECTIVES: The aim of this study was to determine the 15- to 20-year outcome of coronary bypass surgery in patients with angina. BACKGROUND: Coronary bypass surgery has been performed for > 20 years; we need to know the expected outcome of a very long-term follow-up. METHODS: Using actuarial techniques, we determined the outcome of coronary bypass surgery performed for chronic stable and unstable angina in 7,529 patients from 1969 to 1988. RESULTS: The 5-, 10-, 15- and 20-year survival rates (mean +/- SE) were 88 +/- 1, 73 +/- 1, 53 +/- 1 and 38 +/- 3%, respectively, for the whole group. Compared with patients operated on in 1974 to 1988 (n = 7,026), patients operated on in 1969 to 1973 (n = 503) were younger and had less coronary artery disease but had a higher operative mortality rate and a shorter long-term survival time; 15- and 20-year survival of the 1969 to 1973 cohort was 47 +/- 2% and 33 +/- 3%, respectively. The 1974 to 1988 cohort of patients had a 2.1% operative mortality rate and a 10- and 15-year survival probability of 74 +/- 1% and 55 +/- 2%, respectively. For 2,128 patients with "normal" left ventricular function, the 10- and 15-year survival probability was 82 +/- 1% and 64 +/- 3%, respectively, and for 2,413 patients with "abnormal" left ventricular function, it was 66 +/- 1% and 47 +/- 3%, respectively (p < 0.0001); for men it was 74 +/- 1% and 56 +/- 2%, respectively, and for women, 70 +/- 2% and 52 +/- 5%, respectively, p < 0.05. The actuarial percentages of reoperation and myocardial infarction at 15 years were 33 +/- 2% and 26 +/- 2%, respectively; these values did not differ significantly between men and women. There was a significant (p < 0.001) difference between men and women in angina status; 81% of the men versus 74% of the women had no angina or mild angina at the most recent follow-up study. CONCLUSIONS: Coronary bypass surgery is an effective form of therapy for angina (for 15 to 20 years) in both men and women.

Age Factors↗
PubMed1993

Survival at 15 to 18 years after coronary bypass surgery for angina in women.

BACKGROUND: Coronary bypass surgery in women is associated with lower survival than in men. We need to know whether this is because of patient-related factors and whether the lower survival is present in all subgroups of patients and for all time periods during which the surgery was performed. METHODS AND RESULTS: Using actuarial techniques, we determined the outcome of coronary bypass surgery performed for chronic stable and unstable angina in 1979 women and 6927 men. The operative mortality was 2.7% for women and 1.9% for men (P = .02). The higher operative mortality in women was seen in those with three-vessel disease or greater and abnormal left ventricular function (5.4% versus 2.8%, P = .009) and those with stable angina (2.6% versus 1.5%, P = .006). The 5-, 10-, 15-, and 18-year survival for women was 86 +/- 0.9%, 70 +/- 1.5%, 50 +/- 2.5%, and 37 +/- 6.4%, respectively, and for men, 88 +/- 0.4%, 73 +/- 0.7%, 54 +/- 1.2%, and 42 +/- 1.9%, respectively (P = .03). The lower survival in women compared with men was seen in those with three-vessel disease or greater and abnormal left ventricular function (at 10 years, 69 +/- 1.8% versus 73 +/- 0.8%, P = .005). At 15 years, the incidence of reoperation was 26 +/- 2.4% versus 28 +/- 1.2% and of myocardial infarction, 30 +/- 2.8% versus 32 +/- 1.3%, P = NS for either. The incidence of no angina or mild angina was 70% in women and 78% in men, P < .0001. The operative mortality and late survival of those operated on in different time periods for either women or men was not significantly different. Women were older (64 +/- 9.4 versus 61 +/- 9.9 years, P < .0001) and smaller (body surface area, 2.0 +/- 0.2 versus 1.7 +/- 0.2 m2, P < .0001), had a higher incidence of diabetes, systemic hypertension, and unstable angina, and had a smaller lumen of the left anterior descending coronary artery (1.7 +/- 0.4 versus 1.9 +/- 0.4 mm, P < .0001), right coronary artery, and diagonal arteries. More men were smokers, and men had a higher incidence of prior myocardial infarction, previous coronary bypass surgery, and extent of coronary disease and of abnormal left ventricular function. The Cox regression model of survival showed that independent risk factors for lower survival were older age, previous coronary bypass surgery, previous myocardial infarction, and diabetes. Sex was not an independent risk factor for poorer survival. CONCLUSIONS: Women have a higher operative mortality and lower long-term survival than men after coronary bypass surgery for angina. However, the differences are small, even if statistically significant. Importantly, patient-related factors and not sex are independent predictors of poorer survival. Therefore, coronary bypass surgery should not be delayed or denied to women who have the usual indications for surgery.

Actuarial Analysis↗
PubMed1993

Utilization of manufacturers' implant card data to estimate heart valve failure.

Heart valve manufacturers possess the most complete inventory of world-wide mechanical valve failures, but to convert failures to time-related risks requires estimates of patient follow up. Since manufacturers did not actively track patients, they needed a model that incorporates an assumed death rate to decrease the numbers of patients at risk. We present a method for using a manufacturer's implant card database to estimate time-related complication rates for patient subsets, and illustrate its use by examining the risk of outlet strut fracture (OSF) with the Björk-Shiley 60 degrees Convexo-Concave valve (CC60). We developed a parametric model for valve patient survival based on actively followed valve patients from three centers using only variables typically available from implant cards. Using this survival model, a simulated lifetime was produced for each valve in the CC60 implant database for which the required covariates were known. These lifetimes were then used to analyze OSF as if they were true follow up times. This allowed the use of conventional methods of univariate and multivariate analysis for OSF, including parametric statistical models. According to the approximate linearity of the cumulative hazard functions, OSF risk over time appeared to be fairly constant. Several risk factors were identified, including valve size, patient age at implant and valve position. Using parametric models for both patient survival and OSF permits the estimation of the probability of OSF before death for an individual patient (as opposed to the usual actuarial probability of OSF given that the patient does not die). Because the patient may die before his valve would have failed, this cumulative incidence of OSF is always less than the actuarial risk. For all but the very highest risk patients, the cumulative incidence over their relatively short remaining lifetimes is very small.

Actuarial Analysis↗