Effect of outflow level and maximum graft diameter on the velocity parameters of reversed vein bypass grafts. (73/4477)

OBJECTIVE: The objective of this study was to define a normal range of distal graft velocity (DGV) and peak systolic velocity (PSV) on the basis of outflow level and maximum graft diameter for infrainguinal reversed vein bypass grafting (RVG). METHODS: This study was designed as a prospective study of consecutive patients who underwent infrainguinal RVG from 1994 to 1997 in a university hospital and university-affiliated teaching hospital. All patients who underwent infrainguinal bypass grafting from 1994 to 1997 were placed in a prospective protocol with duplex scanning to better define the hemodynamics of normally functioning RVG. Graft revisions were performed for patients with velocity ratios of more than 2.5. One hundred twenty-one patients were entered into this protocol, and 114 were followed more than 3 months after RVG. Seven patients were excluded: five for death within 3 months, one for graft infection, and one for graft occlusion before the baseline duplex scanning. DGV and PSV were determined for each type of outflow (popliteal, crural, and pedal) and for ranges of maximum graft diameter. These then were correlated with subsequent graft occlusion or graft revision (graft failure). RESULTS: Grafts with larger diameters were associated with lower DGVs (P <.001), and more proximal outflow arteries were associated with higher DGVs (popliteal, 75 cm/s; crural, 50 cm/s; and pedal, 40 cm/s; P <.01). The mean PSVs were 150, 140, and 122 cm/s for popliteal, crural, and pedal grafts, respectively, but the difference was not statistically significant. The assisted primary patency rates for the grafts in this series were 99%, 92%, and 92% at 1, 2, and 3 years. CONCLUSION: Graft diameter and location of the distal anastomosis significantly affect the flow velocity in RVG. Other variables did not influence these parameters. Currently established criteria for arteriography or graft repair on the basis of graft velocity parameters may be improved if they can be modified depending on diameter and outflow.  (+info)

Vascular surgery and the Internet: a poor source of patient-oriented information. (74/4477)

OBJECTIVE: Increasing numbers of patients use the Internet to obtain medical information. The Internet is easily accessible, but available information is under no guidelines or regulations. We sought to evaluate the type, quality, and focus of vascular disease information presented on the Internet and the role in patient education with simple search techniques. METHODS: The arbitrarily chosen search phrases "abdominal aortic aneurysm (AAA)," "carotid surgery (CEA)," "claudication surgery," and "leg gangrene surgery" were entered into five common Internet search engines. No attempt was made to refine searches. As indicated by the search engines, the 50 most commonly encountered web sites for both AAA and CEA were reviewed. The first 25 claudication sites and the first 25 gangrene sites were combined for a total of 50 leg ischemia (LIS) sites. An information score (IS) was developed as a weighted score ranging from 0 (poor) to 100 (outstanding) and was designed to assess how well the web page educated the patient about the disease, the treatment options, and the medical and surgical complications. Each vascular surgery web site was classified according to the author, the referenced information source, and the therapeutic recommendations. This was followed by an evaluation of each web site with the IS independently scored by two observers. RESULTS: Of the 150 web sites, 146 were accessible. Ninety-six sites (65.8%) had no useful patient-oriented information (IS < 10). The mean IS and the ranges were: AAA, 14.9 (0 to 72.0); CEA, 17.5 (0 to 77.0); and LIS, 12.2 (0 to 44.5; P =.9). The mean IS of the 59 sites with scores of more than 10 were: AAA, 39.8 (n = 17); CEA, 44.8 (n = 19); and LIS, 24.8 (n = 23; P <.01, as compared with LIS scores). Differences in IS between observers were not significant (P =.9). Misleading or unconventional care recommendations were recognized in one AAA site (1 of 47, 2.1%), two CEA sites (2 of 49, 4.1%), and 13 LIS sites (13 of 50, 26.0%). The Joint Vascular Societies web page was identified only as a tertiary link. CONCLUSION: Patient-oriented vascular surgery information, for common vascular diseases, is difficult to find on the Internet. The overall quality is poor, and information is difficult to obtain in part because of the large number of irrelevant sites. Of the sites that were relevant to patient education (33%), one third presented information that was classified by the authors as misleading or unconventional. This was most apparent in the leg ischemia sites. The Internet is a poor overall source of patient-oriented vascular surgery information and education. Focused and refined searches and improvements in search engines and educational web sites may yield improved information. Public and medical community awareness needs to be improved regarding the severe limitations of the Internet as an information resource.  (+info)

Do residual arteriovenous fistulae after in situ saphenous vein bypass grafting influence patency? (75/4477)

PURPOSE: The purpose of this study was to evaluate the influence on patency of residual arteriovenous fistulae (AVF) after in situ saphenous vein bypass grafting. METHODS: Between January 1, 1994, and December 31, 1996, 98 in situ saphenous vein bypass grafting procedures were performed in 94 patients. Patency was evaluated with duplex scanning after operation and at 1, 3, 6, 9, and 12 months. RESULTS: The indications for operation were intermittent claudication in two patients and critical leg ischemia in 92 patients. Two above-knee and 48 below-knee femoropopliteal and 48 femorocrural in situ saphenous vein bypass grafting procedures were performed. The median follow-up period was 9 months (range, 1.5 to 12.5 months). There were no residual AVF in 45 veins (44%; group 1), but 110 residual AVF were found in 53 veins (56%; group 2). In group 2, 36 AVF in 18 veins were surgically or radiologically occluded mainly as a result of a flow velocity decrease distal to the AVF, but the remaining 74 AVF were treated conservatively. The 1-year cumulative primary patency rates were 68% in group 1 and 74% in group 2 (log-rank test, 0.47; degree of freedom = 1; P =.52). The 1-year cumulative assisted primary patency rates were 68% in group 1 and 81% in group 2 (log-rank test, 2.19; degree of freedom = 1; P =. 14). CONCLUSION: Residual AVF after in situ bypass grafting without influence on bypass graft hemodynamics do not compromise patency and thrombose spontaneously.  (+info)

Prediction of imminent amputation in patients with non-reconstructible leg ischemia by means of microcirculatory investigations. (76/4477)

PURPOSE: We investigated the usefulness of skin microcirculatory investigations to predict imminent major amputation in patients with non-reconstructible critical limb ischemia. METHODS: One hundred eleven patients with non-reconstructible chronic rest pain or small ulcers and an ankle blood pressure of 50 mm Hg or less or an ankle-to-brachial pressure index of 0.35 or less were included. Nailfold capillary microscopy (CM; big toe, sitting), transcutaneous oxygen pressure (TcpO2; forefoot, supine; 44 degrees C), and laser Doppler perfusion measurements (LD; pulp of big toe, supine) were performed at rest and during reactive hyperemia. Patients were classified according to their skin microcirculatory status just before the start of the treatment in three groups: those with a "good," "intermediate," or "poor" microcirculation, according to a combination of predefined cutoff values (Poor: capillary density less than 20/mm2, absent reactive hyperemia in CM and LD, TcpO2 less than 10 mm Hg; good: capillary density of 20/mm2 or more, present reactive hyperemia in CM and LD, TcpO 2 of 30 mm Hg or more). Subsequently, patients received maximum conservative therapy from the surgeon, who was unaware of the microcirculatory results. After a follow-up period of as long as 36 months, limb survival and disposing factors were analyzed and compared with the initial microcirculatory status. RESULTS: Cox regression analysis showed a significant prognostic value of the microcirculatory classification (hazard ratio = 0.28, P <.0001), but not of the Fontaine stage, ankle blood pressure, or the presence of diabetes mellitus for the occurrence of an amputation. Positive and negative predictive values were 73% and 67%, respectively. The cumulative limb survival at 6 and 12 months was 42% and 17% in the poor microcirculatory group, 80% and 63% in the intermediate microcirculatory group, and 88% and 88% in the good microcirculatory group ( P <.0001, log-rank). CONCLUSION: Microcirculatory screening and classification is useful in detecting non-reconstructible critical ischemia that requires amputation, which is not detectable by means of the clinical stage or blood pressure parameters. Most of the poor patient group will require amputation. In the intermediate and good groups, nonsurgical treatment appears sufficient for limb salvage.  (+info)

Response of anterior parietal cortex to cutaneous flutter versus vibration. (77/4477)

The response of anesthetized squirrel monkey anterior parietal (SI) cortex to 25 or 200 Hz sinusoidal vertical skin displacement stimulation was studied using the method of optical intrinsic signal (OIS) imaging. Twenty-five-Hertz ("flutter") stimulation of a discrete skin site on either the hindlimb or forelimb for 3-30 s evoked a prominent increase in absorbance within cytoarchitectonic areas 3b and 1 in the contralateral hemisphere. This response was confined to those area 3b/1 regions occupied by neurons with a receptive field (RF) that includes the stimulated skin site. In contrast, same-site 200-Hz stimulation ("vibration") for 3-30 s evoked a decrease in absorbance in a much larger territory (most frequently involving areas 3b, 1, and area 3a, but in some subjects area 2 as well) than the region that undergoes an increase in absorbance during 25-Hz flutter stimulation. The increase in absorbance evoked by 25-Hz flutter developed quickly and remained relatively constant for as long as stimulation continued (stimulus duration never exceeded 30 s). At 1-3 s after stimulus onset, the response to 200-Hz stimulation, like the response to 25-Hz flutter, consisted of a localized increase in absorbance limited to the topographically appropriate region of area 3b and/or area 1. With continuing 200-Hz stimulation, however, the early response declined, and by 4-6 s after stimulus onset, it was replaced by a prominent and spatially extensive decrease in absorbance. The spike train responses of single quickly adapting (QA) neurons were recorded extracellularly during microelectrode penetrations that traverse the optically responding regions of areas 3b and 1. Onset of either 25- or 200-Hz stimulation at a site within the cutaneous RF of a QA neuron was accompanied by a substantial increase in mean spike firing rate. With continued 200-Hz stimulation, however, QA neuron mean firing rate declined rapidly (typically within 0.5-1.0 s) to a level below that recorded at the same time after onset of same-site 25-Hz stimulation. For some neurons, the mean firing rate after the initial 0.5-1 s of an exposure to 200-Hz stimulation of the RF decreased to a level below the level of background ("spontaneous") activity. The decline in both the stimulus-evoked increases in absorbance in areas 3b/1 and spike discharge activity of area 3b/1 neurons within only a few seconds of the onset of 200-Hz skin stimulation raised the possibility that the predominant effect of continuous 200-Hz stimulation for >3 s is inhibition of area 3b/1 QA neurons. This possibility was evaluated at the neuronal population level by comparing the intrinsic signal evoked in areas 3b/1 by 25-Hz skin stimulation to the intrinsic signal evoked by a same-site skin stimulus containing both 25- and 200-Hz sinusoidal components (a "complex waveform stimulus"). Such experiments revealed that the increase in absorbance evoked in areas 3b/1 by a stimulus having both 25- and 200-Hz components was substantially smaller (especially at times >3 s after stimulus onset) than the increase in absorbance evoked by "pure" 25-Hz stimulation of the same skin site. It is concluded that within a brief time (within 1-3 s) after stimulus onset, 200-Hz skin stimulation elicits a powerful inhibitory action on area 3b/1 QA neurons. The findings appear generally consistent with the suggestion that the activity of neurons in cortical regions other than areas 3b and 1 play the leading role in the processing of high-frequency (>/=200 Hz) vibrotactile stimuli.  (+info)

Limb blood flow and vascular conductance are reduced with age in healthy humans: relation to elevations in sympathetic nerve activity and declines in oxygen demand. (78/4477)

BACKGROUND: We tested the hypothesis that basal (resting) limb blood flow and vascular conductance are reduced with age in adult humans and that these changes are related to elevations in sympathetic vasoconstrictor nerve activity and reductions in limb oxygen demand. METHODS AND RESULTS: Sixteen young (28+/-1 years; mean+/-SEM) and 15 older (63+/-1 years) healthy normotensive adult men were studied. Diastolic blood pressure and body fat were higher (P<0.005) in the older men, but there were no other age-related differences in subject characteristics. Femoral artery blood flow (Doppler ultrasound) was 26% lower in the older men (P<0.005), despite similar levels of cardiac output (systemic arterial blood flow) in the 2 groups. Femoral artery vascular conductance was 32% lower and femoral vascular resistance was 45% higher in the older men (P<0. 005). Muscle sympathetic nerve activity (peroneal microneurography) was 74% higher in the older men (P<0.001) and correlated with femoral artery blood flow (r=-0.55, P<0.005), vascular conductance (r=-0.65, P<0.001), and vascular resistance (r=0.61, P<0.001). The age-related differences in femoral hemodynamics were no longer significant after correction for the influence of muscle sympathetic nerve activity. There were no significant age-group differences in leg tissue mass (by dual-energy x-ray absorptiometry), but estimated leg oxygen consumption was 15% lower in the older men (P<0.001). Femoral artery blood flow was directly related to estimated leg oxygen consumption (r=0.78, P<0.001). The age-group differences in femoral artery blood flow were no longer significant after correction for estimated leg oxygen consumption by ANCOVA. CONCLUSIONS: (1) Basal whole-leg arterial blood flow and vascular conductance are reduced with age in healthy adult men; (2) these changes are associated with elevations in sympathetic vasoconstrictor nerve activity; and (3) the lower whole-limb blood flow is related to a lower oxygen demand that is independent of tissue mass.  (+info)

PDH activation by dichloroacetate reduces TCA cycle intermediates at rest but not during exercise in humans. (79/4477)

We hypothesized that dichloroacetate (DCA), which stimulates the pyruvate dehydrogenase complex (PDH), would attenuate the increase in muscle tricarboxylic acid cycle intermediates (TCAI) during exercise by increasing the oxidative disposal of pyruvate and attenuating the flux through anaplerotic pathways. Six subjects were infused with either saline (Con) or DCA (100 mg/kg body mass) and then performed a moderate leg kicking exercise for 15 min, followed immediately by intense exercise until exhaustion (Exh; approximately 4 min). Resting active fraction of PDH (PDH(a)) was markedly increased (P +info)

Muscle net glucose uptake and glucose kinetics after endurance training in men. (80/4477)

We evaluated the hypotheses that alterations in glucose disposal rate (R(d)) due to endurance training are the result of changed net glucose uptake by active muscle and that blood glucose is shunted to working muscle during exercise requiring high relative power output. We studied leg net glucose uptake during 1 h of cycle ergometry at two intensities before training [45 and 65% of peak rate of oxygen consumption (VO(2 peak))] and after training [65% pretraining VO(2 peak), same absolute workload (ABT), and 65% posttraining VO(2 peak), same relative workload (RLT)]. Nine male subjects (178.1 +/- 2.5 cm, 81.8 +/- 3.3 kg, 27.4 +/- 2.0 yr) were tested before and after 9 wk of cycle ergometer training, five times a week at 75% VO(2 peak). The power output that elicited 66.0 +/- 1.1% of VO(2 peak) before training elicited 54.0 +/- 1.7% after training. Whole body glucose R(d) decreased posttraining at ABT (5.45 +/- 0.31 mg. kg(-1). min(-1) at 65% pretraining to 4.36 +/- 0.44 mg. kg(-1). min(-1)) but not at RLT (5.94 +/- 0.47 mg. kg(-1). min(-1)). Net glucose uptake was attenuated posttraining at ABT (1.87 +/- 0.42 mmol/min at 65% pretraining and 0.54 +/- 0.33 mmol/min) but not at RLT (2.25 +/- 0. 81 mmol/min). The decrease in leg net glucose uptake at ABT was of similar magnitude as the drop in glucose R(d) and thus could explain dampened glucose flux after training. Glycogen degradation also decreased posttraining at ABT but not RLT. Leg net glucose uptake accounted for 61% of blood glucose flux before training and 81% after training at the same relative (65% VO(2 peak)) workload and only 38% after training at ABT. We conclude that 1) alterations in active muscle glucose uptake with training determine changes in whole body glucose kinetics; 2) muscle glucose uptake decreases for a given, moderate intensity task after training; and 3) hard exercise (65% VO(2 peak)) promotes a glucose shunt from inactive tissues to active muscle.  (+info)