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Biomedical subjects

V Parsonnet

Publications and source records attributed to V Parsonnet.

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

Identification of preoperative variables needed for risk adjustment of short-term mortality after coronary artery bypass graft surgery. The Working Group Panel on the Cooperative CABG Database Project.

OBJECTIVES: The purpose of this consensus effort was to define and prioritize the importance of a set of clinical variables useful for monitoring and improving the short-term mortality of patients undergoing coronary artery bypass graft surgery (CABG). BACKGROUND: Despite widespread use of data bases to monitor the outcome of patients undergoing CABG, no consistent set of clinical variables has been defined for risk adjustment of observed outcomes for baseline differences in disease severity among patients. METHODS: Experts with a background in epidemiology, biostatistics and clinical care with an interest in assessing outcomes of CABG derived from previous work with professional societies, government or academic institutions volunteered to participate in this unsponsored consensus process. Two meetings of this ad hoc working group were required to define and prioritize clinical variables into core, level 1 or level 2 groupings to reflect their importance for relating to short-term mortality after CABG. Definitions of these 44 variables were simple and specific to enhance objectivity of the 7 core, 13 level 1 and 24 level 2 variables. Core and level 1 variables were evaluated using data from five existing data bases, and core variables only were examined in an additional two data bases to confirm the consensus opinion of the relative prognostic power of each variable. RESULTS: Multivariable logistic regression models of the seven core variables showed all to be predictive of bypass surgery mortality in some of the seven existing data sets. Variables relating to acuteness, age and previous operation proved to be the most important in all data sets tested. Variables describing coronary anatomy appeared to be least significant. Models including both the 7 core and 13 level 1 variables in five of the seven data sets showed the core variables to reflect 45% to 83% of the predictive information. However, some level 1 variables were stronger than some core variables in some data sets. CONCLUSIONS: A relatively small number of clinical variables provide a large amount of prognostic information in patients undergoing CABG.

Coronary Artery Bypass↗
PubMed1996

Survey of cardiac pacing and defibrillation in the United States in 1993.

A survey of implanters of permanent cardiac pacemakers and implanted cardioverter-defibrillators (ICDs) in the United States during 1993 was conducted to identify present and changing patterns in indications for pacing implantation techniques, pacing-mode selection, follow-up, and opinions regarding pacing-and ICD-related issues. Five major pacemaker manufacturers also provided estimates of the numbers of pacemakers and ICDs implanted in the United States from 1990 through 1993. In 1993 approximately 133,000 new rhythm-management devices, including 112,000 primary pacing systems and 16,000 ICDs, were implanted, an increase of 18% for pacemakers and 113% for ICDs since 1990. In 1993, pacemaker implantations were performed by about 8,700 physicians working in 3,300 hospitals and 1,000 independent "surgi-centers." Since the last survey, which addressed pacing practices in 1989, respondents' use of dual-chamber pacemakers increased from 32% to 68% of the total, and adaptive-rate systems from 29% to 48%. Significant differences (p <0.05) were found among subcategories of implanters and among complications encountered in different circumstances. Surgeons tended be the older and more experienced implanters, but used a smaller proportion of active-fixation leads, dual-chamber systems, and adaptive-rate pulse generators, and tended to rely more heavily on a pacemaker manufacturer's representative in operative and follow-up procedures. Complications were more common with bipolar leads, with leads implanted by means of an introducer, and with passive-fixation ventricular leads. The survey provided useful insights into trends and differences in pacemaker and defibrillator practice. Future surveys would be facilitated if a standardized implant registry such as that used in Europe were established in the United States.

Cardiac Pacing, Artificial↗
PubMed1996

Clinical usefulness of risk-stratified outcome analysis in cardiac surgery in New Jersey.

BACKGROUND: The results of aortocoronary bypass grafting are under increasing scrutiny by the Health Care Financing Agency, health maintenance organizations, and the news media. Surgeons and hospital administrators are concerned that erroneous conclusions may be drawn from raw outcome data, which do not reflect the patient's preoperative condition. It is our contention that any realistic comparison of results among surgeons or institutions must take that condition into account through a process of risk management. METHODS: We have developed a statistical model for risk stratification based on data compiled systematically at the Newark Beth Israel Medical Center since 1980. Univariate analysis and stepwise logistic regression are used to identify the most significant risk factors and determine the appropriate weight for each. Our original risk stratification system has now been updated by eliminating the optional fields and reweighting the variables. This has reduced the subjective input and improved the accuracy. RESULTS: Use of the modified system shows good correlation between expected and observed outcomes at our institution and in other cases reported to the New Jersey Department of Health. It has improved the results especially in high-risk cases: in total, a group of 5,336 patients have been assessed by the modified system: the expected mortality overall was 7.2% and the observed mortality was 5.4%. In 1,280 high-risk patients, ie, those with an expected mortality of greater than 11%, the expected mortality was 16.2% and the observed mortality was 12.3%. CONCLUSIONS: Our results suggest a decline in length of hospital stay and beneficial changes in operative procedures. They also indicate that exclusion of high-risk cases will result in only minimal financial savings, perhaps less than 2%.

Analysis of Variance↗
PubMed1996

The effect of thrombus on the vascular endothelium of arterialized vein grafts.

BACKGROUND: It is known that vein grafts can be salvaged by clot removal, but patency rates are diminished. This study was designed to determine the effects of thrombus on vascular endothelium and the ability of the endothelium to recover normal function. METHODS: Thirty external jugular vein grafts were placed as bilateral femoral artery interposition grafts in 15 mongrel dogs and allowed to arterialize for a period of at least 12 weeks. Six control grafts were not exposed to thrombus (C-NT). Six other control grafts were exposed to thrombus for 7 days and removed, ie, allowed no in vivo recovery (C-T). The remaining 18 grafts in 9 canines were exposed to autologous thrombus for 5 days and then flow was restored. The right femoral graft was removed 7 days after thrombectomy and the left removed 30 days after thrombectomy. At the time of removal, the grafts were perfused with a balanced salt solution alone and then with arachidonic acid added to the same volume of the salt solution. Perfusates were collected at 5, 15, and 30 minutes. These perfusates were assayed for the presence of 6-keto-prosglandin F1 alpha (6-keto-PGF1(1 alpha)), a metabolite of prostacyclin (PGI2). Over the 30-day recovery period, the amounts of 6-keto-PGF1(1 alpha) produced with and without arachidonic acid added were compared to assess endothelial response. Electron micrographs of the endothelium of all vein grafts were compared to the assay findings. RESULTS: When arachidonic acid was added to the perfusion system, there was a several fold increase in the production of 6-keto-PGF1(1 alpha) over baseline in all grafts allowed recovery. Grafts (C-T) that were allowed no in vivo recovery had no response to arachidonic acid. Ratios of 6-keto-PGF1(1 alpha) production with arachidonic acid stimulation to 6-keto-PGF1(1 alpha) production without stimulation were calculated to compare endothelial function. The electron micrographs showed the vascular endothelium to be severely injured after contact with thrombus, but recovered by 7 days. CONCLUSIONS: This study suggests that the endothelium of canine vein grafts is injured by contact with thrombus for 5 days but can recover structure and function. This recovery is detectable at 7 days post-thrombectomy.

6-Ketoprostaglandin F1 alpha↗
PubMed1996

Failure rates of leads, pulse generators, and programmers have not diminished over the last 20 years: formal monitoring of performance is still needed. BILITCH Registry and STIMAREC.

Formal Monitoring of Performance is Still Needed. In order to detect trends in the number of device or component failures that have occurred among permanent pacemaker systems since the 1970s, we reviewed the data of the five largest pacemaker manufacturers from the Bilitch Registry of permanent pacemaker pulse generators, the Stimarec failure registry, the general accounting office summaries of the United States Veterans Administration (VA) Registry of Pacemaker Leads, and the Implantable Lead Registry, from the Cleveland Clinic Lead registry, and the recalls and safety alerts issued by the United States Food and Drug Administration (FDA) over the last 20 years. The definition of failure followed the criterion, or criteria, developed within each registry and differed significantly between the registries. The 20-year period between 1976 and 1995 was divided into 5-year quartiles (QT): QT 1 = 1976-1980; QT2 = 1981-1985; QT3 = 1986-1990; and QT4 = 1991-1995. For pulse generators, the number of models with failures in each quartile in the Bilitch Registry were: QT 1 = 9; QT 2 = 11; QT3 = 17; QT4 = 13. In Stimarec, the number of units reported as having reached a dangerous condition were: QT1 = 710; QT2 = 212; QT3 = 114; QT4 = 310. From the FDA reports, the number of units included in recalls or safety alerts were: QT3 = 6,085; QT4 = 135,766. For permanent pacemaker leads, the numbers of failed or dangerous leads recorded in Stimarec were: QT3 = 16; QT4 = 32. In the VA Registry, the number of models having a below average survival was 2/92 (2.7%). In the Implantable Lead Registry, the number of models having a below average survival was 3/21 (14%). In the Cleveland Clinic series, 6/13 (46%) of lead models were recognized to have some failure involving the conductor, insulation, or connector. In the FDA reports, the number of leads involved in either recall or safety alert were: QT3 = 20,354; QT4 = 332,105. For programmers, the number of units involved either in a recall or safety alert were: QT3 = 11,124; QT4 = 3,528. In all of these series, each of the five largest manufacturers had some models or units involved in each time period. This review of programs has revealed: 1. The incidence of failures, recalls, or safety alerts did not decline over time; and 2. Despite changes in technology, formal monitoring of pacemaker systems is still warranted.

Electric Power Supplies↗
PubMed1996

Initial experience with 1.5-mm2 high impedance, steroid-eluting pacing electrodes.

UNLABELLED: In this human study, 21 atrial and 62 ventricular 1.5-mm2 unipolar steroid-eluting pacing electrodes were implanted in 64 patients. Pacing thresholds, lead impedance, and sensing measurements were measured via pacemaker telemetry within 24 hours postimplant, and at 1, 2, 3, 4, 6, 12, 24, and 52 weeks. Acute pacing impedances measured via a pacing systems analyzer were 1,039 +/- 292 (atrial) and 1,268 +/- 313 ohms (ventricular). A 10%-15% decline in the mean telemetered atrial and ventricular pacing impedances was observed at 1 week, but thereafter remained stable. Acute pacing thresholds at 0.5 ms were 0.5 +/- 0.3 V (atrial) and 0.4 +/- 0.1 V (ventricular). Filtered P and R wave amplitudes were 3.7 +/- 2.3 mV and 14.9 +/- 5.9 mV, respectively. In 21 patients, no complications related to the atrial electrode were observed. Of 62 patients with ventricular electrodes, 4 patients (6%) experienced complications and required surgical intervention. On these, causative factors included micro-dislodgment (1 patient), and perforation (1 patient). Sudden unexplained exit block occurred late (> 6 weeks) in two patients. In the remainder of patients, pacing thresholds and sensed electrogram amplitudes remained stable throughout the 52-week follow-up period. CONCLUSIONS: The present study validates that smaller surface (i.e., 1.5 mm2) steroid-eluting electrode designs offer excellent pacing and sensing performance with significantly higher pacing impedances. Although questions remain as to the cause of late exit block in two patients in this series, this relatively small surface electrode design offers promise toward achieving greater pacing efficiency and a theoretical 13%-16% (minimum) enhancement in permanent pacemaker longevity.

Administration, Topical↗
PubMed1995

Transient loss of sensing and capture during coronary angiography in two patients with permanent pacemakers.

Two cases of transient pacemaker failure to sense and capture during angiography are reported. This phenomenon is due to a transient increase in sensing and pacing thresholds beyond the pacemakers programmed settings. The underlying mechanism may be related to blood displacement, the electrochemical properties of the injectate, the high concentration of the contrast media, or a combination of these properties. Even though the chambers in which sensing and pacing loss occurred differed (ventricle in the first and atria in the second), the episode occurred repeatedly after injection of contrast media into the artery supplying the respective electrode-tissue interface. In pacemaker dependent patients, provisions for external pacing should be implemented prior to injection of contrast into the coronary arteries.

Contrast Media↗
PubMed1995

Instantaneous lead entrapment: an unusual complication of nonthoracotomy implantation of an endocardial defibrillation lead.

Nonthoracotomy implantation of implantable cardioverter defibrillators is performed with transvenous leads that are similar to pacemaker leads and are subject to the same potential problems. We report an unusual complication of lead placement in which an electrode immediately became entrapped in the superior rim of the tricuspid valve, resisting all efforts at removal.

Aged↗
PubMed1995

Risk stratification in cardiac surgery: is it worthwhile?

Outcome analysis of many surgical procedures has become increasingly important to surgeons, institutions, and the public. Because there may be wide differences in case mix, outcomes must be evaluated in light of the patient's preoperative status. All relevant preoperative conditions must be identified and weighted, so that when risk factor scores are combined in some fashion, they will provide a single preoperative risk estimate for the individual patient, representing the likelihood of dying as a consequence of the operation. Comparing the mean risk adjusted score of a group of patients undergoing the same procedure with the observed mortality rate for the same group yields an index of the quality of care, provided all preoperative risk scores are calculated with reference to the same benchmark. We question the logic and wisdom of surgical outcome analysis because of the infinitely complex nature of biological and pathological processes, as well as the practical problems of reliable data collection. The assumption of true scientific accuracy may be illusory. Even though risk adjusted outcome analysis has merit in studying trends in therapy, it should be regarded with caution when used as a tool for evaluating quality of care. If publicized at all, the results should not be represented as "hard" scientific fact.

Cardiac Surgical Procedures↗