Biomedical subjects

Peter Gaccione

Publications and source records attributed to Peter Gaccione.

6 recordsLinked to original sources

PubMed2006

Early biomechanical changes in lower extremity vein grafts--distinct temporal phases of remodeling and wall stiffness.

BACKGROUND: The geometric and biomechanical changes that contribute to vein graft remodeling are not well established. We sought to measure patterns of adaptation in lower extremity vein grafts and assess their correlation with clinical outcomes. METHODS: We conducted a prospective, longitudinal study of patients undergoing infrainguinal reconstruction with autogenous conduit. In addition to standard duplex surveillance, lumen diameter (of a defined index segment of the conduit) and pulse wave velocity (PWV) were assessed by ultrasound imaging at surgery and at 1, 3, and 6 months postoperatively. Graft dimensions and wall stiffness were correlated with clinical outcomes. RESULTS: There were 92 patients and 96 limbs in this study. On average, vein graft lumen diameter increased during the first month of implantation from 0.37 +/- .01 cm to 0.45 +/- 0.02 cm (mean +/- SEM; P = .002), representing a relative change of +21.6% (median +/- 14%; range, -31 to +67%) during this period. Of the entire cohort, 72% of grafts demonstrated appreciable dilation of the index segment during the first month. Index segment lumen diameter did not change appreciably beyond 1 month, with the notable exception of arm vein conduits, which showed continued tendency to dilate. PWV increased during the first 6 months (17.2 +/- 1.2 m/s to 23.2 +/- 2.4 m/s; P = .008), reflecting a nearly 40% increase in conduit stiffness (2.0 +/- .6 Mdynes/cm to 3.3 +/- .8 Mdynes/cm, P = .01). The greatest relative increase (25%) in PWV occurred from months 1 to 3. Loss of primary patency occurred in 24 cases (19 revisions, 5 occlusions), with a mean reintervention time of 7.6 months. Grafts that demonstrated early positive remodeling (lumen dilatation) had a trend of increased primary patency (P = .08, log rank). Among the grafts that failed, a trend was noted toward greater wall stiffness at 1 month, 2.7 vs 1.5 Mdynes (P = .08). CONCLUSION: Vein graft remodeling appears to involve at least two distinct temporal phases. Outward remodeling of the lumen occurs early, and wall stiffness changes occur in a more delayed fashion. Early outward remodeling may be important for successful vein graft adaptation.

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PubMed2006

Selection and plan switching behavior.

A majority of employees can choose among health insurance plans of varying generosity. They may switch plans if prices, information, or their health status change. This paper analyzes switching behavior presumptively caused by changes in health status. We show that people who move to a less generous plan have lower medical spending prior to the switch than the average for the generous plan in which they started, while those who move to a more generous plan appear to anticipate higher spending, which they delay until after the switch. This transfer of costs from a less to a more generous plan increases the burden of adverse selection. Our data suggest that switching may be more important to the level of premiums than previously documented.

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PubMed2004

Early adaptation of human lower extremity vein grafts: wall stiffness changes accompany geometric remodeling.

OBJECTIVE: To quantitatively describe the temporal changes in elastic properties and wall dimensions in lower-extremity vein grafts after implantation. DESIGN OF STUDY: This is a prospective study of patients (N = 38) undergoing lower extremity bypass grafts (N = 41) with autologous veins. Pulse wave velocity (PWV), luminal diameter, and wall thickness measurements were obtained by duplex ultrasound scan intraoperatively and at 1, 3, and 6 months postoperatively for assessment of graft dimensions and wall stiffness. RESULTS: Lower extremity vein grafts showed an increase in PWV (from 16 +/- 1 to 21 +/- 3 cm/s; mean +/- SEM; P =.08), reflecting an increase in wall stiffness (from 1.2 +/- 0.2 to 2.5 +/- 0.7 x 10(6) dynes/cm; P =.02) and wall thickness (from 0.47 +/- 0.03 to 0.61 +/- 0.004 mm; P =.04) over the first 6 months after implantation. Changes in lumen diameter were positively correlated with changes in external graft diameter (P <.01) and negatively correlated with initial lumen diameter (P <.01) but not with changes in the wall thickness. CONCLUSIONS: These results suggest complex remodeling of vein grafts during the first several months after implantation, with increased wall thickness occurring independent of variable changes in lumen diameter. Simultaneously, a marked increase in wall stiffness over this interval suggests a likely role for collagen deposition.

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PubMed2003

Preoperative risk factors for carotid endarterectomy: defining the patient at high risk.

PURPOSE: The efficacy of carotid endarterectomy (CEA) for prevention of stroke has been demonstrated in randomized trials; however, the optimal approach in patients excluded from these trials or who have other significant comorbid conditions remains controversial, particularly with the advent of percutaneous interventions. We examined the influence of putative risk factors on outcome of CEA in a single-center experience. METHODS: A retrospective analysis of 1370 consecutive CEA performed from 1990 to 1999 was undertaken. Preoperative risk factors examined included age older than 80 years, congestive heart failure, chronic obstructive pulmonary disease, renal failure (serum creatinine concentration > 2.0 mg/dL), contralateral carotid artery occlusion, recurrent ipsilateral carotid artery stenosis, ipsilateral hemispheric symptoms within 6 weeks, and recent coronary bypass grafting (CABG). The Fisher exact test was used to identify baseline variables associated with perioperative (30 days) risk for stroke or death. Multivariate analysis with Poisson regression was used to study the effect of all univariate criteria in combination. RESULTS: In the overall cohort, there were 32 adverse events (2.3%), including 11 deaths (0.8%), 6 disabling strokes (0.4%), and 10 nondisabling strokes (0.7%). There was no significant difference in incidence of perioperative stroke or death between patients with one or more risk factors (n = 689) and those with no risk factors (low risk, n = 681). Thirty-day mortality was significantly greater in patients with two or more risk factors compared with patients with no risk factors (2.8% vs 0.3%; P =.04), but no significant difference was noted in perioperative stroke rate (2.3% vs 1.0%). Univariate analysis demonstrated that contralateral carotid occlusion (n = 75) was the only significant predictor of adverse outcome (5 events, 6.7%) among the variables tested; this was confirmed with multivariate analysis (relative risk, 4.3; 95% confidence interval, 1.2-12.3; P =.01). Five-year survival for patients with two or more risk factors was notably diminished compared with that for patients with no risk factors (38.7% +/- 5.9% vs 75.0% +/- 2.6%; P <.001). Contralateral occlusion was also associated with reduced 5-year survival (38 +/- 11% vs 67 +/- 2%; P <.004). CONCLUSION: CEA can be safely performed in patients deemed at high risk, including those aged 80 years or older and others with significant comorbid conditions, with combined stroke and mortality rates comparable to those found in randomized trials, ie, the Asymptomatic Carotid Atherosclerosis Study and the North American Symptomatic Carotid Endarterectomy Trial. Contralateral occlusion may be a predictor for moderately increased perioperative risk and for reduced long-term survival. Caution may be warranted in asymptomatic patients with multiple risk factors, in whom presumed long-term benefit of CEA may be compromised by markedly reduced 5-year survival.

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PubMed2002

Specialty of ambulatory care physicians and mortality among elderly patients after myocardial infarction.

BACKGROUND: The outcome after myocardial infarction may be influenced by the type of physician providing ambulatory care. METHODS: We studied 35,520 patients 65 years of age or older who were hospitalized for myocardial infarction in seven states during 1994 and 1995 and who survived for at least three months after discharge. From Medicare claims, we identified ambulatory visits to cardiologists, internists, and family practitioners. Using propensity scores to adjust for demographic, clinical, and hospital characteristics, we analyzed treatment and mortality at two years among patients matched according to their estimated propensity to receive care from a cardiologist within three months after discharge. RESULTS: As compared with patients who saw only an internist or a family practitioner in the three months after discharge, patients who saw a cardiologist were younger, were more likely to be white, were more likely to be male, had fewer coexisting conditions, and were more likely to have undergone invasive cardiac procedures while hospitalized (P<0.01 for all comparisons). Patients who saw a cardiologist were more likely to undergo cardiac procedures and rehabilitation after discharge. Patients who saw a cardiologist had a lower two-year mortality rate than matched patients who saw only an internist or a family practitioner (14.6 percent vs. 18.3 percent, P<0.001). Patients who saw both a cardiologist and an internist or a family practitioner had a lower mortality rate than matched patients who saw only a cardiologist (11.1 percent vs. 12.1 percent, P=0.02). CONCLUSIONS: Ambulatory visits to cardiologists were associated with greater use of cardiac procedures and decreased mortality after myocardial infarction. Concurrent care by an internist or a family practitioner was associated with a further reduction in mortality.

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PubMedDate not supplied

Does reimbursement influence chemotherapy treatment for cancer patients?

Before the Medicare Prescription Drug, Improvement, and Modernization Act (MMA) of 2003, Medicare reimbursed physicians for chemotherapy drugs at rates that greatly exceeded physicians' costs for those drugs. We examined the effect of physician reimbursement on chemotherapy treatment of Medicare beneficiaries older than age sixty-five with metastatic lung, breast, colorectal, or other gastrointestinal cancers between 1995 and 1998 (9,357 patients). A physician's decision to administer chemotherapy to metastatic cancer patients was not measurably affected by higher reimbursement. Providers who were more generously reimbursed, however, prescribed more-costly chemotherapy regimens to metastatic breast, colorectal, and lung cancer patients.

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