Perioperative outcomes and amputation-free survival after lower extremity bypass surgery in California hospitals, 1996-1999, with follow-up through 2004
ABSTRACT There are very few population-based studies of long-term outcomes after lower extremity (LE) bypass graft surgery. This study analyzes perioperative and long-term limb salvage and amputation-free survival outcomes for patients undergoing initial aortoiliac or femoropopliteal bypass graft surgery in California hospitals from 1996 to 1999.
Administrative data with encrypted identifiers were used to identify a chronologically first, index admission of all patients undergoing LE bypass procedures for occlusive disease from 1996 to 1999. A 1993 to 1995 look-back period was used to exclude patients who had undergone prior bypass surgery or amputation procedures. Patients with incident procedures were then followed forward to determine subsequent hospitalizations and vital status through 2004. The study comprised 28,128 patients discharged from 345 California hospitals with a median 61.5-month follow-up. Risk factors included demographic characteristics, comorbid conditions, admission type, gangrene or ulceration, operation level, hospital LE bypass surgery volume, and year of discharge. Logistic regression was used to analyze 30-day outcomes, and Kaplan-Meier analysis and Cox proportional hazard models were used to analyze amputation-free survival.
Overall 30-day mortality was 4.3, and the 30-day major amputation rate was 2.6%. Limb salvage was 81.9% at 5 years and 76.4% at 9 years. Amputation-free survival was 51.5% at 5 years and 34.1% at 9 years. Risk factors were generally similar for both perioperative and late outcomes. Advanced age, higher comorbidity level, gangrene, and emergency or nursing home admission conferred significantly greater risk. Hospital volume was associated with both perioperative and late outcomes. African American and Hispanic patients had much higher amputation rates but did not have higher mortality risk after controlling for baseline severity of illness.
Long-term outcomes of LE bypass surgery were superior for high-volume hospital patients. Graft surveillance and risk factor follow-up care provide a major opportunity for quality improvement efforts. The contrast between traditional limb salvage and amputation-free survival outcomes raises questions about the value of surgical treatment, particularly for patients with limited life expectancy and without coding of tissue loss or critical limb ischemia.
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ABSTRACT: NMR is a rapidly developing modality with proven diagnostic potential. The wealth of information involved suggests that computers can play a valuable role in the analysis of NMR images beyond the common uses of acquisition, reconstruction, storage and display. Applications in the area of relaxation time images, calculated intensity images, flow images and tissue type maps are described.
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ABSTRACT: Log periodic designs are a well established wide-band antenna technology, but one in which the phase center travels along the structure as the frequency varies. When a log periodic antenna is used as a feed for a reflector antenna, the phase center location cannot be maintained at the reflector focus over the frequency range and defocusing results. The purpose of this analysis is to quantify the defocusing loss for a log periodicfed reflector. The analysis presented compares favorably with measured results.IEEE Transactions on Antennas and Propagation 08/1985; DOI:10.1109/TAP.1985.1143659 · 2.46 Impact Factor
Conference Paper: Improved arrival time detection for cardiac pulse transit sonomicrometry[Show abstract] [Hide abstract]
ABSTRACT: Routine pulse transit sonomicrometry uses simple threshold detection to determine ultrasonic signal arrival time. An improved method uses the known shape of the signal's leading edge as a 1.5 to 3 /spl mu/sec template to find the arrival time with a cross-correlation matched energy estimator procedure. Over a sliding window in the received data, the template data and it's Hilbert transform are cross correlated with the received data. The cross correlation generates a likelihood estimate for all possible window position, each corresponding to an arrival time. Waterbath and animal transducer signals were collected using a conventional sonomicrometer connected to a digital oscilloscope and the data analyzed off-line to implement the algorithms. Likelihood estimators behaved as expected and peak detection used on the likelihood estimators gave arrival times uniformly within 100 ns of conventional threshold detection. Various amounts of noise were added to the received signal to evaluate robustness. Even with enough noise that the original signal was barely visible in a time plot, the new likelihood procedure yielded very close arrival times.Computers in Cardiology, 1996; 10/1996