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Biomedical subjects

M McPharlin

Publications and source records attributed to M McPharlin.

5 recordsLinked to original sources
PubMed1993

Outpatient duplex scanning for deep vein thrombosis: parameters predictive of a negative study result.

PURPOSE: Although clinical examination has been reported to be unreliable in the diagnosis of deep vein thrombosis (DVT), this conclusion has often been derived from hospitalized patients (HP) and may not be applicable in an outpatient setting. This study was undertaken to define clinical parameters that might predict the diagnostic value of emergency venous duplex scanning (VDS). METHODS: Venous duplex scans performed over a 9-month period (interval I) in 154 outpatients (154 limbs) and 145 HP (145 limbs) with suspected DVT were reviewed. RESULTS: Eighteen percent of scans of outpatients and 31% of scans of HP were interpreted as positive for lower extremity DVT. With stepwise logistic regression analysis, criteria predictive of a negative result of outpatient VDS included (1) duration of symptoms greater than 7 days (p = 0.003), (2) thigh circumference difference relative to the uninvolved side of less than 3 cm (p = 0.001), and (3) no history of neoplasia (p = 0.03). This model, when applied prospectively to 68 outpatients (68 limbs) over the next 5 months (interval II), yielded a negative predictive value (NPV) of 96.7% (sensitivity 90.9%, specificity 50.9%, positive predictive value 26.3%). Of the 222 outpatients examined during intervals I and II, 98 (44%) met these three clinical criteria. Three of these 98 outpatients had DVT on VDS and thus would have been misclassified as having a negative result. With a similar logistic regression analysis for HP, clinical criteria achieved an NPV of only 75% (sensitivity 36%, specificity 90%, positive predictive value 62%). CONCLUSION: Clinical assessment is unreliable in the diagnostic evaluation of HP with suspected DVT. In an outpatient population, however, clinical evaluation with the above criteria achieved an NPV of 96.7% in the diagnosis of DVT. These parameters may be useful as guidelines in determining the appropriateness of emergency outpatient VDS.

Ambulatory Care↗
PubMed1990

Pitfalls in lower extremity venous duplex scanning.

Results of scans performed on 1074 patients over an 18-month period were evaluated to define the limitations of lower extremity venous duplex scanning. Eighty-four patients had confirmatory phlebography performed within 24 hours of their venous duplex scanning. In 71 patients scans were considered diagnostic (sensitivity 91%, specificity 95%). Eighteen studies (13 equivocal, 5 misinterpretations) were scrutinized to determine the limitations of venous duplex scanning compared to phlebography and are the focus of this analysis. Seven patients had phlebograms documenting only infrapopliteal thrombus, seven had normal phlebographic findings, and four had findings consistent with chronic thrombosis. In the seven patients with infrapopliteal thrombus, four had normal imaging outcomes but abnormal Doppler flow patterns, whereas three had both normal imaging results and flow patterns. All four patients with chronic thrombosis had identifiable thrombus and abnormal flow patterns by venous duplex scanning, but in each case thrombus age was indeterminate. Of the seven patients with normal phlebographic results, five had incompressible segments of the superficial femoral vein on imaging, one had abnormal Doppler flow without visualized thrombus and without apparent reason, one had venous duplex scanning visualized thrombus with a normal outcome on phlebography. These data suggest that the diagnostic yield of lower extremity venous duplex scanning may be improved by (1) meticulous infrapopliteal vein examination, (2) better estimation of the age of the thrombotic process, and (3) recognizing segmental incompressibility of the superficial femoral vein within the adductor canal as a normal finding especially in the absence of abnormal Doppler flow or imaged thrombus.

Chronic Disease↗
PubMed1986

A thirty-year survey of the reconstructive surgical treatment of aortoiliac occlusive disease.

With the view of assessing functional durability and the factors that influence or determine it, we reviewed the clinical course of 1748 reconstructive operations performed between Jan. 1, 1954, and Dec. 31, 1983 in the treatment of 1647 patients with aortoiliac occlusive disease (AIOD). Disabling intermittent claudication (in 65.6%), ischemic rest pain and/ or pregangrene (in 20.7%), and ischemic gangrene (in 13.7%) were the operative indications. Patency proven by angiography was the criterion of success. Follow-up was continuous and endless and 94% successful over a period of 30 years. Twenty-five percent of the patients were followed up for 11 to 30 years. The incidence of severe degree of occlusive involvement increased significantly from the first (9.3%) to the third (17.1%) decade of observation, whereas the perioperative mortality rate improved markedly from the first (7.4%) to the third (2.5%) decade. The aortobifemoral bypass (AF2B) procedure remained the most popular type of repair (with a perioperative patency rate of 91.4%) throughout, but both it and unilateral reconstructions lost some ground to remote (extra-anatomic) bypasses in the third decade. Atherosclerotic heart disease remained the most common cause of perioperative (50%) and late (60.2%) death. Among the early postoperative local complications graft thrombosis improved markedly from the first (8.3%) to the third (3.2%) decade. Graft infection remained rare (1.6% to 0.8%). The incidence of the most common late wound complication, anastomotic aneurysm at the common femoral level, remained relatively constant (5.7% per anastomosis), but it responded very well to surgical correction. The partial or complete secondary repair of all late complications (26.0%) improved the cumulative late patency rate in the AF2B procedures by 2% to 12% during 20 years of observation. The perioperative (97.3%), 5-year (76.6%), 10-year (76.6%), 15-year (72.5%), and 20-year (67.5%) cumulative patency rates of AF2B operations were highly satisfactory. The postoperative late survival rate of patients with AIOD declined rapidly (59% at 5, 33% at 10, 14% at 15 years). The cause of late death in 60.2% of the cases was atherosclerotic heart disease.

Aortic Diseases↗
PubMed1986

Limitations of the femoral artery pulsatility index with aortoiliac artery stenosis: an experimental study.

Relationships between femoral artery pulsatility index (PI) (a number calculated from Doppler-derived arterial blood velocity waveforms) and three directly measured physiologic parameters (proximal artery stenosis, blood pressure index (BPI), and blood flow) were studied in a canine model. All combinations of stenoses were constructed, including 0%, 25%, 50%, 75%, and 90% reduction in a cross-sectional area in the infrarenal aorta and/or left common iliac artery of 14 animals. PIs, BPIs, and mean blood flows were measured for each stenosis pattern at both the right (control) and left femoral arteries. Three groups were studied--group I, the left femoral artery remained open; group II, the left femoral artery was ligated; and group III, a left femoral arteriovenous fistula was constructed. Correlations between reductions in femoral artery PI and increasing arterial stenosis as well as decreasing BPI and blood flow were obtained. However, positive correlations were weak and only recognized when high-grade stenoses were present. Moreover, these correlations were further influenced by the multiplicity of stenoses present as well as flow velocity into the distal arterial bed. These data suggest that PI lacks the sensitivity to be a clinically useful diagnostic test.

Animals↗