The consequences of a failed femoropopliteal bypass grafting: comparison of saphenous vein and PTFE grafts.

OBJECTIVES: Although there are numerous reports comparing saphenous vein (SV) and polytetrafluoroethylene (PTFE) with respect to the patency rates for femoropopliteal bypass grafts, the clinical consequences of failed grafts are not as well described. This study compares the outcomes of failed SV and PTFE grafts with a specific emphasis on the degree of acute limb ischemia caused by graft occlusion. METHODS: Over a 6-year period, 718 infrainguinal revascularization procedures were performed, of which 189 were femoropopliteal bypass grafts (SV, 108; PTFE, 81). Society for Vascular Surgery/International Society for Cardiovascular Surgery (SVS/ISCVS) standardized runoff scores were calculated from preoperative arteriograms. Clinical categories of acute limb ischemia resulting from graft occlusion were graded according to SVS/ISCVS standards (I, viable; II, threatened; III, irreversible). Primary graft patency and limb salvage rates at 48 months were calculated according to the Kaplan-Meier method. RESULTS: Patients were well matched for age, sex, and comorbidities. Chronic critical ischemia was the operative indication in most cases (SV, 82%; PTFE, 80%; P =.85). Runoff scores and preoperative ankle-brachial index measurements were similar for the two groups (SV, 6.0 +/- 2.5 [SD] and 0.51 +/- 0.29; PTFE, 5.3 +/- 2.8 and 0.45 +/- 0.20; P =.06 and P =.12). The distal anastomosis was made below the knee in 60% of SV grafts and 16% of PTFE grafts (P <.001). Grade II ischemia was more likely to occur after occlusion of PTFE grafts (78%) than after occlusion of SV grafts (21%; P =.001). Emergency revascularization after graft occlusion was required for 28% of PTFE failures but only 3% of SV graft failures (P <.001). Primary graft patency at 48 months was 58% for SV grafts and 32% for PTFE grafts (P =.008). Limb salvage was achieved in 81% of SV grafts but only 56% of PTFE grafts (P =.019). CONCLUSIONS: Patients undergoing femoropopliteal bypass grafting with PTFE are at greater risk of ischemic complications from graft occlusion and more frequently require emergency limb revascularization as a result of graft occlusion than patients receiving SV grafts. Graft patency and limb salvage are superior with SV in comparison with PTFE in patients undergoing femoropopliteal bypass grafting.

Extracellular ATP increases cytosolic calcium in cultured rat renal arterial smooth muscle cells.

1. Experiments were conducted on cultured renal arterial smooth muscle cells to determine the ability of extracellular ATP to alter cytosolic calcium concentration and to determine the mechanisms by which this effect occurs. 2. ATP (100 mumol/L) caused the fluorescence ratio of fura-2 to increase from a control value of 1.06 +/- 0.05 to 2.06 +/- 0.13 (P < 0.01) before stabilizing at a sustained level of 1.35 +/- 0.04 (n = 8; P < 0.05). 3. Removal of extracellular calcium from the bathing medium resulted in an attenuation of the initial response to 100 mumol/L ATP with cell fluorescence increasing from 1.16 +/- 0.18 to 1.44 +/- 0.18 ratio units (n = 5). Furthermore, the initial increase in fluorescence ratio rapidly declined to 1.02 +/- 0.06, indicating that an influx of extracellular calcium is required to sustain the increase in fura-2 fluorescence. 4. Depletion of intracellular calcium pools with thapsigargin prevented the increase in fura-2 fluorescence evoked by ATP. 5. These data suggest that ATP-mediated increases in cytosolic calcium in cultured renal arterial smooth muscle cells involve calcium release from the thapsigargin-sensitive, intracellular pool in conjunction with calcium influx from the extracellular medium.

Calcium activation mechanisms in the renal microvascular response to extracellular ATP.

Previous studies have suggested a paracrine role for extracellular ATP in the regulation of afferent arteriolar tone. The current study was conducted to determine the dependence of this response on calcium entry mechanisms. Experiments were performed in vitro using the blood-perfused juxtamedullary nephron technique combined with video microscopy. The afferent arteriolar response to alpha, beta-methylene ATP was determined before and after treatment with the calcium channel blockers, diltiazem or felodipine. alpha, beta-Methylene ATP was used to obviate concerns over responses being elicited by ATP or by ATP hydrolysis products such as adenosine. Previous studies have shown that afferent arteriolar responses to alpha, beta-methylene ATP are comparable to those elicited by ATP. alpha, beta-Methylene ATP (1.0 microM) induced a rapid initial afferent vasoconstriction of 72.5 +/- 10.6%, which partially recovered to a stable diameter 11.3 +/- 1.7% smaller than control (P < 0.01 vs control). Afferent diameter returned to control diameter on removal of ATP from the bath. Diltiazem or felodipine treatment significantly increased afferent diameter by 5.6 +/- 2.3 and 16.4 +/- 4.6%, respectively (P < 0.05). In the presence of either diltiazem or felodipine, the initial vasoconstriction to alpha, beta-methylene ATP was attenuated, and the sustained vasoconstriction was completely blocked. Removal of calcium from the extracellular medium completely abolished both the initial and sustained vasoconstrictor response.(ABSTRACT TRUNCATED AT 250 WORDS)