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Biomedical subjects

M B Leon

Publications and source records attributed to M B Leon.

At least 181 records · Page 10Linked to original sources
PubMed1997

Overestimation of acute lumen gain and late lumen loss by quantitative coronary angiography (compared with intravascular ultrasound) in stented lesions.

The accurate measurement of lumen dimensions is essential for guidance of interventional procedures and the assessment of acute and late results. This study compared intravascular ultrasound (IVUS) with quantitative coronary angiography (QCA) in the assessment of lumen dimensions before and after intervention, and at follow-up. Two hundred thirty-one consecutive patients treated with Palmaz-Schatz stents and evaluated using serial (before and after intervention, and follow-up) IVUS and QCA were screened. Because IVUS cannot measure dimensions smaller than the imaging catheter, patients having an angiographic minimal lumen diameter (MLD) less than the IVUS catheter (1.0 mm) during any study were excluded, leaving 71 patients in the final study group. IVUS and QCA measurements (reference dimensions and MLD) and calculations (percent diameter stenosis, acute lumen gain, late lumen loss, loss index, and restenosis rates) were compared. Correlation coefficients ranged from 0.641 to 0.816 for measured variables and from 0.280 to 0.680 for calculated variables. Reference lumen dimensions were consistently larger by IVUS than by QCA: 0.50 +/- 0.52 mm before intervention (p <0.0001), 0.46 +/- 0.45 mm after intervention (p <0.0001), and 0.38 +/- 0.53 mm at follow-up (p <0.0001). MLDs measured by IVUS were larger before intervention (0.17 +/- 0.28 mm, p <0.0001), smaller after intervention (0.17 +/- 0.34 mm, p <0.0001), and larger at follow-up (0.14 +/- 0.41 mm, p <0.0001). This resulted in a smaller acute gain and late loss measured by IVUS (0.33 +/- 0.39 and 0.30 +/- 0.47 mm, respectively, both p <0.0001). Although measures of restenosis (i.e., loss index and restenosis rates) were similar, the classification of lesions in individual patients (as restenotic vs nonrestenotic) was significantly different (p = 0.002, concordance rate = 73%). There are systematic differences between IVUS and QCA in the measurement of reference and lesion lumen dimensions. Although indexes of restenosis were similar, classification of lesions in individual patients was different.

Aged↗
PubMed1997

Treatment of in-stent restenosis with excimer laser coronary angioplasty: mechanisms and results compared with PTCA alone.

BACKGROUND: This study determined the clinical safety, mechanisms, and 6-month results of excimer laser angioplasty (ELCA)+adjunct PTCA for the treatment of in-stent restenosis and (via lesion matching) compared the results of ELCA+PTCA to PTCA alone. METHODS AND RESULTS: Using quantitative angiography (QCA) and intravascular ultrasound (IVUS), we studied 107 restenotic previously stented lesions in 98 patients before and after intervention. QCA measurements included minimum lumen diameter (MLD) and diameter stenosis (DS). IVUS measurements included stent, lumen, and intimal hyperplasia (IH=stent-lumen) cross-sectional areas (CSA) and volumes. In the 54 lesions treated with ELCA+PTCA, the MLD increased from 0.73+/-0.38 mm before ELCA to 2.10+/-0.47 mm after ELCA+PTCA (P<.0001); the DS decreased from 70+/-14% to 25+/-12% (P<.0001). By IVUS, the minimum lumen CSA increased from 1.58+/-0.78 mm2 before ELCA to 6.34+/-1.75 mm2 after ELCA+PTCA (P<.0001) as a result of an increase in minimum stent CSA from 7.70+/-2.41 to 9.10+/-2.60 mm2 (P<.0001) and a decrease in IH CSA from 5.25+/-2.84 to 2.63+/-1.41 mm2 (P<.0001). Volumetric analysis showed that tissue ablation (during ELCA) contributed 29+/-15%, tissue extrusion (during adjunct PTCA) contributed 31+/-14%, and additional stent expansion (during adjunct PTCA) contributed 40+/-16% to the overall lumen gain. There were no ELCA-related complications. Matched to lesions treated with PTCA alone, ELCA+PTCA resulted in greater lumen gain, more IH ablation/extrusion, larger final lumen CSA (IVUS), and a tendency for less frequent need for subsequent target vessel revascularization (TVR, 21% versus 38%, P=.0823). CONCLUSIONS: ELCA safely and effectively ablates in-stent neointimal tissue. Adjunct PTCA extrudes neointimal tissue out of the stent and also further expands the stent. Compared with PTCA alone, ELCA+PTCA achieves better short-term and, potentially, better long-term results.

Angioplasty, Balloon, Coronary↗
PubMed1997

Late clinical outcomes of cordis tantalum coronary stenting without anticoagulation.

This study was performed to evaluate clinical and angiographic restenosis rates after successful Cordis coronary stent implantation and intravascular ultrasound images were acquired to compare results with quantitative angiographic findings in a subgroup of patients. We conclude that (1) the angiographic restenosis rate of Cordis stent was 19%, which was comparable to that of other slotted-tube stents, and (2) the quantitative coronary angiographic calliper method is reliable for assessing Cordis in-stent restenosis, especially diffuse in-stent restenosis.

Coronary Angiography↗
PubMed1997

Stent placement compared with balloon angioplasty for obstructed coronary bypass grafts. Saphenous Vein De Novo Trial Investigators.

BACKGROUND: Treatment of stenosis in saphenous-vein grafts after coronary-artery bypass surgery is a difficult challenge. The purpose of this study was to compare the effects of stent placement with those of balloon angioplasty on clinical and angiographic outcomes in patients with obstructive disease of saphenous-vein grafts. METHODS: A total of 220 patients with new lesions in aortocoronary-venous bypass grafts were randomly assigned to placement of Palmaz-Schatz stents or standard balloon angioplasty. Coronary angiography was performed during the index procedure and six months later. RESULTS: As compared with the patients assigned to angioplasty, those assigned to stenting had a higher rate of procedural efficacy, defined as a reduction in stenosis to less than 50 percent of the vessel diameter without a major cardiac complication (92 percent vs. 69 percent, P<0.001), but they had more frequent hemorrhagic complications (17 percent vs. 5 percent, P<0.01). Patients in the stent group had a larger mean (+/-SD) increase in luminal diameter immediately after the procedure (1.92+/-0.30 mm, as compared with 1.21+/-0.37 mm in the angioplasty group; P<0.001) and a greater mean net gain in luminal diameter at six months (0.85+/-0.96 vs. 0.54+/-0.91 mm, P=0.002). Restenosis occurred in 37 percent of the patients in the stent group and in 46 percent of the patients in the angioplasty group (P=0.24). The outcome in terms of freedom from death, myocardial infarction, repeated bypass surgery, or revascularization of the target lesion was significantly better in the stent group (73 percent vs. 58 percent, P = 0.03). CONCLUSIONS: As compared with balloon angioplasty, stenting of selected venous bypass-graft lesions resulted in superior procedural outcomes, a larger gain in luminal diameter, and a reduction in major cardiac events. However, there was no significant benefit in the rate of angiographic restenosis, which was the primary end point of the study.

Aged↗
PubMed1997

Remodeling of human coronary arteries undergoing coronary angioplasty or atherectomy.

BACKGROUND: Recently, long-term constriction of the vessel has been suggested as an alternative mechanism of restenosis after coronary angioplasty. METHODS AND RESULTS: To understand remodeling of human coronary arteries undergoing coronary angioplasty or atherectomy, serial intravascular ultrasonographic examinations were performed at preintervention and postintervention examinations and at 24 hours, 1 month, and 6 months. Complete serial data were obtained in 61 lesions (balloon angioplasty, 35 lesions; directional atherectomy, 26 lesions). Lumen area improved from 6.81+/-2.24 mm2 after intervention to 8.22+/-2.79 mm2 at 1 month (P=.0001) and decreased to 4.88+/-2.86 mm2 at 6 months (P=.0001). Vessel area enlarged from 17.32+/-5.35 mm2 after intervention to 19.39+/-5.33 mm2 at 1 month (P=.0001) and decreased to 16.33+/-5.54 mm2 at 6 months (P=.0001). Plaque+media area increased significantly from postintervention examination to 24 hours (10.51+/-4.38 versus 10.96+/-4.49 mm2, P=.0008) and from 24 hours to 6 months (10.96+/-4.49 versus 11.45+/-4.45 mm2, P=.03). Changes in lumen area in each study interval correlated more closely with changes in vessel area than with changes in plaque+media area. Restenotic lesions compared with nonrestenotic lesions had a greater decrease in the vessel area between 1 month and 6 months (-4.33+/-2.73 versus -2.49+/-2.15 mm2, P=.006) and greater increase in the plaque+media area both within 24 hours (0.84+/-1.22 versus 0.27+/-0.38 mm2, P=.04) and between 24 hours and 6 months (1.19+/-2.19 versus 0.18+/-1.46 mm2, P=.04). CONCLUSIONS; Remodeling after coronary angioplasty or atherectomy was characterized by early adaptive enlargement and late constriction of the vessel.

Aged↗
PubMed1997

Comparison of men versus women in cross-sectional area luminal narrowing, quantity of plaque, presence of calcium in plaque, and lumen location in coronary arteries by intravascular ultrasound in patients with stable angina pectoris.

Women have an increased mortality after coronary interventions compared with men, which may be partly explained by differences in comorbid clinical conditions. However, whether women also have quantitative differences in coronary atherosclerosis is not known. Preinterventional intravascular ultrasound (IVUS) was used to study de novo, nonostial native coronary lesions in 169 women and 549 men with chronic angina. The external elastic membrane (EEM), lumen, and plaque + media (P + M) areas, plaque burden, plaque eccentricity, and calcium were measured at the target lesion and at a proximal reference site. All cross-sectional IVUS measures were also corrected for body surface area. Results are reported as mean +/- 1 SD. Women had significantly smaller reference site EEM (16.5 +/- 5.3 vs 19.4 +/- 6.3 mm2, p <0.0001), lumen (8.7 +/- 3.0 vs 9.9 +/- 4.0 mm2, p = 0.0020), and P + M areas (7.8 +/- 3.7 vs 9.5 +/- 4.2 mm2, p = 0.0001). Women also had significantly smaller lesion site EEM (16.2 +/- 5.9 vs 18.3 +/- 6.7 mm2, p = 0.0028), lumen (2.4 +/- 1.7 vs 2.9 +/- 2.6 mm2, p = 0.0273), and P + M areas (13.6 +/- 5.7 vs 15.3 +/- 6.4 mm2, p = 0.0112). However, when corrected for BSA, these differences were no longer significant. Women and men also had similar reference and lesion plaque burden, eccentricity, and calcium. Preinterventional IVUS analysis failed to detect any quantitative or qualitative differences in coronary atherosclerosis in men compared with women.

Aged↗
PubMed1997

Catheter-based radiotherapy to inhibit restenosis after coronary stenting.

BACKGROUND: In animal models of coronary restenosis, intracoronary radiotherapy has been shown to reduce the intimal hyperplasia that is a part of restenosis. We studied the safety and efficacy of catheter-based intracoronary gamma radiation plus stenting to reduce coronary restenosis in patients with previous restenosis. METHODS: Patients with restenosis underwent coronary stenting, as required, and balloon dilation and were then randomly assigned to receive catheter-based irradiation with iridium-192 or placebo. Clinical follow-up was performed, with quantitative coronary angiographic and intravascular ultrasonographic measurements at six months. RESULTS: Fifty-five patients were enrolled; 26 were assigned to the iridium-192 group and 29 to the placebo group. Angiographic studies were performed in 53 patients (96 percent) at a mean (+/-SD) of 6.7+/-2.2 months. The mean minimal luminal diameter at follow-up was larger in the iridium-192 group than in the placebo group (2.43+/-0.78 mm vs. 1.85+/-0.89 mm, P=0.02). Late luminal loss was significantly lower in the iridium-192 group than in the placebo group (0.38+/-1.06 mm vs. 1.03+/-0.97 mm, P=0.03). Angiographically identified restenosis (stenosis of 50 percent or more of the luminal diameter at follow-up) occurred in 17 percent of the patients in the iridium-192 group, as compared with 54 percent of those in the placebo group (P= 0.01). There were no apparent complications of the treatment. CONCLUSIONS: In this preliminary, short-term study of patients with previous coronary restenosis, coronary stenting followed by catheter-based intracoronary radiotherapy substantially reduced the rate of subsequent restenosis.

Aged↗
PubMed1997

Serial intravascular ultrasound predictors of restenosis at the margins of Palmaz-Schatz stents.

To evaluate predictors of restenosis at margins of Palmaz-Schatz stents, intravascular ultrasound studies were performed after intervention and at follow-up (5.4 months) in 161 stented lesions. Of 301 stent margins, 77 (26%) were restenotic at follow-up (>50% late lumen loss). Intimal hyperplasia was greater for restenotic than for nonrestenotic stents margins. The dominant periprocedural predictor of stent margin restenosis was the plaque burden of the continuous reference segment.

Coronary Disease↗
PubMed1997

Contribution of inadequate arterial remodeling to the development of focal coronary artery stenoses. An intravascular ultrasound study.

BACKGROUND: Adaptive remodeling occurs to compensate for the accumulation of atherosclerotic plaque. Lumen reduction depends on the relative rates of plaque deposition and adaptive remodeling responses. Intravascular ultrasound permits detailed, high-quality, cross-sectional imaging of the coronary arteries in vivo. METHODS AND RESULTS: Preintervention intravascular ultrasound was used to study 603 focal, new, nonostial significant coronary artery stenoses in patients with chronic stable angina. Measurements of the target lesion of the external elastic membrane (EEM), lumen, and plaque plus media (P&M; P&M = EEM - Lumen) cross-sectional areas (CSAs) were compared with a proximal reference segment (most normal-looking cross section within 10 mm proximal to the lesion but distal to any side branch). Inadequate remodeling was defined as lesion/ reference EEM CSA that exceeded the upper limits of normal arterial tapering (lesion/reference EEM CSA ratio < or = 0.78 or a 21% reduction in EEM CSA per 10-mm length). Overall, the lesion/reference EEM CSA ratio was 1.00 +/- 0.22; 15% of lesions had inadequate remodeling, and 37% of the 603 lesions had less plaque than expected. This represented a lesion-specific response. The only predictor of inadequate remodeling was the arc of superficial lesion calcium. CONCLUSIONS: Inadequate remodeling is present in at least 15% of chronic, focal, new coronary arterial stenoses in patients with stable angina. The magnitude of arterial remodeling appears to be a lesion-specific response.

Adaptation, Physiological↗
PubMed1997

Increased restenosis in diabetes mellitus after coronary interventions is due to exaggerated intimal hyperplasia. A serial intravascular ultrasound study.

BACKGROUND: The increased risk of restenosis after catheter-based coronary interventions in diabetic patients has not been determined. Intravascular ultrasound (IVUS) has shown that the decrease in arterial area is responsible for most of the late lumen loss in nonstented lesions and that intimal hyperplasia is responsible for all of the late lumen loss in stented lesions. METHODS AND RESULTS: Serial (postintervention and follow-up at 5.6 +/- 3.3 months) IVUS was used to study 251 native coronary lesions in 241 patients; 63 patients had treated diabetes mellitus (oral hypoglycemic drugs or insulin). Interventional procedures included percutaneous transluminal coronary angioplasty, directional or rotational atherectomy, excimer laser angioplasty, or Palmaz-Schatz stents. The external elastic membrane (EEM), stent, and lumen areas were measured. The plaque+media (P+M) area in nonstented lesions was calculated as EEM minus lumen area, and the intimal hyperplasia (IH) area in stented lesions was calculated as stent minus lumen area. The anatomic slice selected for serial analysis had an axial location within the target lesion at the smallest follow-up lumen area. Nonstented lesions in diabetics and nondiabetics had a similar decrease in EEM cross-sectional area (CSA; 1.9 +/- 2.8 versus 1.8 +/- 4.2 mm2; P = .6350). However, nonstented lesions in diabetics had a greater increase in P+M CSA (1.3 +/- 2.8 versus 0.6 +/- 2.5 mm2, P = .0720), and the increase in P+M CSA contributed a greater percentage to the decrease in lumen CSA. In stented lesions, the decrease in lumen CSA (5.2 +/- 2.5 versus 2.0 +/- 2.3 mm2) and the increase in IH CSA (5.0 +/- 2.8 versus 1.8 +/- 2.0 mm2) were greater in diabetics than nondiabetics (P = .0009 and P = .0007, respectively). These findings were even more striking in (nonstented and stented) restenotic lesions. CONCLUSIONS: Serial IVUS analysis showed that the main reason for increased restenosis in diabetes mellitus was exaggerated intimal hyperplasia in both stented and nonstented lesions.

Aged↗
PubMed1997

Influence of guiding catheter selection on the measurement of coronary flow reserve.

The impact of guiding catheter selection on the measurement of coronary flow reserve was assessed by injecting increasing doses of adenosine through 3 different catheters often used during coronary interventions. When guiding catheters with side holes were used, an approximate doubling of the adenosine dose was required to produce a coronary flow reserve response similar to a 12-micrograms dose of adenosine injected through guiding catheters without side holes.

Adenosine↗
PubMed1997

Continuous subcutaneous angiopeptin treatment significantly reduces neointimal hyperplasia in a porcine coronary in-stent restenosis model.

BACKGROUND: In-stent restenosis results primarily from neointimal hyperplasia. This study evaluated the efficacy and the optimal mode of administration of angiopeptin, a somatostatin analogue with antiproliferative activity, in a porcine coronary in-stent restenosis model. METHODS AND RESULTS: Forty pigs were randomly assigned to one of four groups (n = 10 per group): (1) controls receiving saline infusion at the site of stent implantation via a local delivery catheter, (2) local treatment group receiving one-time treatment (200 (micrograms angiopeptin) at the site of stent placement, (3) systemic treatment group receiving continuous angiopeptin over a 1-week period via a subcutaneous osmotic pump (200 micrograms/kg total dose) and (4) combined local and systemic treatment group. Then, one oversized Palmaz-Schatz stent (mean ratio of stent to artery diameters, 1.3:1) was implanted in the left anterior descending coronary artery. The degree of neointimal reaction was evaluated 4 weeks later by angiography (maximal percent diameter stenosis), intravascular ultrasound (total in-stent neointimal volume), and histology (maximal area stenosis). Systemic treatment produced the least neointimal hyperplasia and significantly reduced in-stent restenosis compared with the control group by all end points, despite similar degrees of injury. Angiography showed 25 +/- 17% versus 50 +/- 17% diameter stenosis in the systemic angiopeptin group versus the control group (P < .0001), intravascular ultrasound revealed 23 +/- 10 versus 58 +/- 27 mm3 neointimal volume in the systemic angiopeptin versus control group (P = .0002), and histology showed 41 +/- 16% versus 69 +/- 18% area stenosis (P = .0016) in the systemic angiopeptin versus control group. Plasma angiopeptin levels revealed rapid clearance (within 6 hours) after local therapy, whereas the levels persisted for up to 2 weeks in the systemic group. CONCLUSIONS: This study shows that continuous subcutaneous treatment with angiopeptin after stent implantation significantly reduces in-stent restenosis by inhibiting neointimal hyperplasia.

Animals↗
PubMed1997

Comparison of stenting and balloon angioplasty for narrowings in aortocoronary saphenous vein conduits in place for more than five years.

To compare the 1 year outcome of Palmaz-Schatz stent implantation versus balloon angioplasty for treatment of obstructive lesions in saphenous vein grafts, we combined databases from the Palmaz-Schatz vein graft stent registry and the coronary angioplasty arm of the Coronary Angioplasty Versus Excisional Atherectomy Trial II (CAVEAT II) for comparison of baseline characteristics, procedural variables, in-hospital events and 1-year composite end point of death, Q-wave myocardial infarction, and repeat target vessel revascularization. De novo graft lesions not involving the ostia were treated with stent implantation in 377 patients and with coronary angioplasty in 156 patients. The patients were comparable in age, coronary risk profile, interval from bypass surgery (9 +/- 4 years), and reference vessel diameter. The in-hospital composite end point of death, myocardial infarction, and emergency revascularization was lower in the stent group (10%) than in the angioplasty cohort (17%) (p = 0.059). At 1 year, the patients in the stent group had a markedly lower incidence of the composite end point of death, myocardial infarction, or revascularization (23% vs 45%, p <0.001). In this nonrandomized comparison with balloon angioplasty, the treatment of lesions in saphenous vein grafts appears to be favorably influenced by Palmaz-Schatz stent implantation, in terms of in-hospital events and clinical restenosis at 1 year follow-up.

Aged↗
PubMed1997

Feasibility and efficacy of locally delivered enoxaparin via the Channeled Balloon catheter on smooth muscle cell proliferation following balloon injury in rabbits.

To determine the potential utility of local treatment of enoxaparin on restenosis, four groups of rabbits underwent balloon injury of bilateral iliac arteries with the Channeled Balloon (balloon/artery = 1.1), followed by assigned treatment (5 controls received local saline, 7 local-treatment rabbits received a one-time local delivery of 10 mg/kg of enoxaparin, 5 systemic-treatment rabbits received 10 mg/kg of enoxaparin subcutaneously once daily for 1 wk, and 5 combined-treatment rabbits received both local and systemic enoxaparin). The percentage of nuclei positive for proliferating cell nuclear antigen/microns2 of media 1 wk later was 1.97 +/- 2.01 for the control group, 2.68 +/- 2.52 for the local group, 0.22 +/- 0.32 for the systemic group, and 0.07 +/- 0.09 for the combined group (P < 0.0001 by Kruskal-Wallis test, with P < 0.05 for combined treatment group vs. controls or local treatment group and systemic vs. local groups). Feasibility study with 3H-enoxaparin showed intramural retention of 0.1-0.2% of locally delivered amount for 24 h. We conclude that one-time local delivery of enoxaparin following angioplasty is ineffective in inhibiting medial smooth muscle cell proliferation, most likely due to low efficiency. Only sustained treatment resulted in significant reduction.

Angioplasty, Balloon↗
PubMed1997

Health after coronary stenting or balloon angioplasty: results from the Stent Restenosis Study.

This study was designed to compare health-related quality of life (HRQOL) in patients undergoing coronary stenting or balloon angioplasty in the randomized Stent Restenosis Study. The study sample was drawn from patients at nine U.S. clinical sites of the Stent Restenosis Study, a randomized trial comparing Palmaz-Schatz coronary stent implantation with conventional balloon angioplasty. One hundred ninety-nine consecutive patients were sent surveys 6 to 18 months after enrollment and 160 (80%) were returned. The survey sent to the patients included the Medical Outcomes Study 36-Item Short-Form Health Survey, the Canadian Cardiovascular Society Classification, and the Duke Activity Status Index. Although patients who underwent stenting had less angiographic restenosis and a tendency for fewer ischemic events, there were few differences in HRQOL after a mean of 456 days after randomization. The group that underwent stenting reported significantly less bodily pain than the group that underwent angioplasty (p = 0.02). Otherwise, there were no significant differences in generic or disease-specific measures. In a rating of their overall health, 47% of the group that underwent stenting and 45% of the group that underwent percutaneous transluminal coronary angioplasty reported very good or excellent health. In each group, 60% of the patients reported being symptom free from a cardiovascular perspective. This survey revealed no marked differences in long-term HRQOL between patients who underwent Palmaz-Schatz coronary stenting compared with those who underwent conventional angioplasty.

Aged↗
PubMed1997

Intravascular ultrasound insights into mechanisms of stenosis formation and restenosis.

Using intravascular ultrasound (IVUS), stenosis formation and restenosis (or late lumen loss following coronary angioplasty procedures) can be subdivided into two distinct underlying components: tissue accumulation and arterial remodeling. Arterial remodeling is defined as a change in total arterial cross-sectional area over time; it can be adaptive (an increase in arterial cross-sectional area as a compensatory response to plaque accumulation) or pathologic (a decrease in arterial cross-sectional area or chronic arterial shrinkage). Adaptive arterial remodeling can delay the development of coronary artery stenoses and prevent restenosis; pathologic remodeling can contribute to de novo lesion formation and has been shown to be the dominant mechanism of restenosis following coronary intervention. Serial IVUS studies have also been used to study the natural history of the restenosis process; adaptive remodeling occurs early (within 1 month) and pathologic remodeling occurs late (between 1 and 6 months) after intervention. The residual plaque burden postintervention acts as an amplifier in this process.

Animals↗