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Biomedical subjects

A D Pichard

Publications and source records attributed to A D Pichard.

At least 19 recordsLinked to original sources
PubMed1995

Mechanisms of lumen enlargement after excimer laser coronary angioplasty. An intravascular ultrasound study.

BACKGROUND: The mechanisms of excimer laser coronary angioplasty (ELCA) have never been studied in human coronary arteries in vivo. METHODS AND RESULTS: ELCA was used to treat 202 lesions in 190 patients. Forty-nine lesions in 48 patients were studied by use of sequential (before and after ELCA and after adjunctive device therapy) intravascular ultrasound (IVUS). External elastic membrane (EEM), lumen, and plaque+media (P+M = EEM-lumen) cross-sectional areas (CSAs) and lesion arcs of calcium were measured before and after ELCA and after adjunct device use. Lumen improvement after ELCA (1.4 +/- 0.5 to 2.7 +/- 0.8 mm2) was the result of both tissue ablation (decrease in P+M CSA from 16.8 +/- 7.1 to 15.9 +/- 6.7 mm2, P < .0001) and vessel expansion (increase in EEM CSA from 18.2 +/- 7.1 to 18.6 +/- 6.8 mm2, P = .0245), with no change in calcium. The decrease in P+M CSA was 39% of the CSA of the laser catheter used. Dissections were present in 39% of lesions, 84% within superficial calcium; fibrocalcific deposits developed a "fragmented" appearance. CONCLUSIONS: ELCA increased lumen CSA by both atheroablation and vessel expansion without calcium ablation. Superficial fibrocalcific deposits developed a characteristic fragmented appearance. These findings support both photoablation and forced vessel expansion as mechanisms of lumen enlargement and plaque dissection after ELCA.

Angioplasty, Balloon, Coronary↗
PubMed1995

Patterns of calcification in coronary artery disease. A statistical analysis of intravascular ultrasound and coronary angiography in 1155 lesions.

BACKGROUND: Target lesion calcium is a marker for significant coronary artery disease and a determinant of the success of transcatheter therapy. METHODS AND RESULTS: Eleven hundred fifty-five native vessel target lesions in 1117 patients were studied by intravascular ultrasound (IVUS) and coronary angiography. The presence, magnitude, location, and distribution of IVUS calcium were analyzed and compared with the detection and classification (none/mild, moderate, and severe) by angiography. Angiography detected calcium in 440 of 1155 lesions (38%): 306 (26%) moderate calcium and 134 (12%) severe. IVUS detected lesion calcium in 841 of 1155 (73%, P < .0001 versus angiography). The mean arc of lesion calcium measured 115 +/- 110 degrees; the mean length measured 3.5 +/- 3.7 mm. Target lesion calcium was only superficial in 48%, only deep in 28%, and both superficial and deep in 24%. The mean arc of superficial calcium measured 85 +/- 108 degrees; the mean length measured 2.4 +/- 3.4 mm. Three hundred seventy-three of 1155 reference segments (32%) contained calcium (P < .0001 compared with lesion site). The mean arc of reference calcium measured 42 +/- 80 degrees; the mean length measured 1.7 +/- 3.6 mm. Only 44 (4%) had reference calcium in the absence of lesion calcium. Angiographic detection and classification of calcium depended on arcs, lengths, location, and distribution of lesion and reference segment calcium. By discriminant analysis, the classification function for predicting angiographic calcium included the arc of target lesion calcium, the arc of superficial calcium, the length of reference segment calcium, and the location of calcium within the lesion. This model correctly predicted the angiographic detection of calcification in 74.4% of lesions and the angiographic classification (none/moderate/severe) of calcium in 62.8% of lesions. CONCLUSIONS: IVUS detected calcium in > 70% of lesions, significantly more often than standard angiography. Although angiography is moderately sensitive for the detection of extensive lesion calcium (sensitivity, 60% and 85% for three- and four-quadrant calcium, respectively), it is less sensitive for the presence of milder degrees.

Calcinosis↗
PubMed1995

Comparison of clinical and angiographic outcomes after saphenous vein graft angioplasty using coronary versus 'biliary' tubular slotted stents.

BACKGROUND: Saphenous vein graft (SVG) angioplasty using 15-mm articulated, tubular slotted stents results in low (0% to 20%) residual diameter stenoses and infrequent (< 5%) major complications. A "biliary" stent design with greater radial compressive strength, enhanced visibility, and more variable sizing (diameter and length) has been approved for noncoronary indications. A comparison of outcomes after coronary versus biliary stent placement in SVG stenoses has not been performed. The purpose of this study was to compare the angiographic and clinical results after SVG angioplasty using these two balloon-expandable, tubular slotted stent designs. METHODS AND RESULTS: During a 3-year period, 231 patients with 305 SVG lesions were treated using Palmaz-Schatz coronary (n = 108) or biliary (n = 123) stents. Cineangiograms were reviewed using qualitative morphological and quantitative angiographic methods. Time-dependent clinical outcome (freedom from death, Q-wave myocardial infarction, or the need for repeat coronary bypass surgery or SVG angioplasty) was assessed using Kaplan-Meier life-table methods. Unstable angina (P < .001) and recent myocardial infarction (P = .001) were present more often in patients undergoing biliary stent versus coronary stent placement. Biliary stent-treated SVG lesions were more frequently de novo (P = .001), ostial in location (P = .002), > or = 10 mm in length (P = .009), thrombus containing (P = .001), and ulcerated (P < .001) than coronary stent-treated SVG lesions. Angiographically, biliary stent-treated lesions had larger reference vessel diameter (3.43 +/- 0.59 mm versus 3.10 +/- 0.64 mm, P < .001), higher balloon-to-artery ratio (1.15 +/- 0.16 mm versus 1.07 +/- 0.19, P = .0001), and lower residual diameter stenosis (6 +/- 17% versus 14 +/- 11% in coronary stent-treated patients; P < .001). Procedural success rates were high (95%), in-hospital major complications were uncommon (< 3%), and follow-up clinical outcomes were favorable (6-month event-free survival approximately 80%) in both groups. CONCLUSIONS: Despite frequent short-term ischemic syndromes and unfavorable lesion characteristics, both biliary and coronary cohorts have similarly favorable short-term procedural results and long-term clinical outcomes. The increased strut thickness of the biliary stent confers greater fluoroscopic visibility and radial compressive strength in exchange for decreased stent flexibility and added technical demand in stent deployment. Extreme caution is recommended with biliary stent placement in the treatment of SVG lesions as clinical results are highly operator dependent.

Aged↗
PubMed1995

Can coronary flow parameters after stent placement predict restenosis?

Intracoronary stent was used to treat a dissection resulting from balloon angioplasty. Coronary flow parameters measured with Doppler Flowire pre- and post-stenting suggested abnormal coronary flow even after stenting. The patient returned 4 months later with an instent restenosis. This case suggests the intriguing possibility of coronary flow parameters obtained immediately after new device angioplasty in predicting restenosis.

Aortic Dissection↗
PubMed1995

Coronary artery morphologic features after coronary rotational atherectomy: insights into mechanisms of lumen enlargement and embolization.

The coronary arteries and myocardium from two patients who died after coronary rotational atherectomy were analyzed to gain insights into the mechanisms of lumen enlargement and to document embolization of calcified plaque. Rotational atherectomy resulted in sharp cuts in plaque, producing a relatively smooth luminal surface. When extensive nodular calcific atherosclerosis was present, the luminal surface was focally uneven with exposure of jagged calcified plaque to blood flow. Deep plaque fissures and medial dissections were also seen. These fissures may have been created by the rotoblator or by adjunctive balloon angioplasty. Multiple calcific atheroemboli were present after rotoblator use in plaques containing extensive nodular calcification; in moderately calcified plaque only one small atheroembolus was found. Thus embolization of calcified plaque can occur after rotational atherectomy and may correlate with the severity of plaque calcification. Rotational atherectomy produces a focally smooth, sharp-edged, luminal surface, a lumen enlargement mechanism different from balloon angioplasty.

Aged↗
PubMed1995

Multivariate predictors of intravascular ultrasound end points after directional coronary atherectomy.

OBJECTIVES: This study attempted to identify the clinical, angiographic, procedural and intravascular ultrasound predictors of directional atherectomy results assessed by intravascular ultrasound. BACKGROUND: Several angiographic and intravascular ultrasound variables have been associated with the outcome of directional coronary atherectomy. No study has incorporated both modalities into a predictive model. METHODS: One hundred seventy patients were analyzed using preintervention and postintervention intravascular ultrasound and quantitative angiography. Clinical and procedural variables were collected by independent chart review. Quantitative and qualitative angiographic analysis was performed by a core laboratory in blinded manner. Intravascular ultrasound was performed using a transducer-tipped catheter, rotating within a stationary imaging sheath, and withdrawn automatically at 0.5 mm/s. Clinical, procedural, angiographic and ultrasound variables were tested in a multivariate linear regression model. Dependent ultrasound variables included postatherectomy lumen cross-sectional area and percent cross-sectional narrowing (plaque plus media/external elastic membrane cross-sectional area) and, in a subgroup of 47 patients studied using volumetric analysis, percent plaque volume removal. RESULTS: By multivariate stepwise linear regression analysis, predictors of residual lumen cross-sectional area (correcting for reference lumen area) included arc of calcium and preatherectomy plaque plus media cross-sectional area; predictors of residual cross-sectional narrowing were arc of calcium, preatherectomy plaque plus media cross-sectional area and lesion length; and predictors of percent plaque volume removal were arc of calcium and atherectomy device size. CONCLUSIONS: The preintervention lesion arc of calcium measured by intravascular ultrasound is the most consistent predictor of the effectiveness and results of directional coronary atherectomy.

Atherectomy, Coronary↗
PubMed1995

Atherosclerosis in angiographically "normal" coronary artery reference segments: an intravascular ultrasound study with clinical correlations.

OBJECTIVES: This study evaluated the magnitude, patterns and clinical correlates of atherosclerosis in angiographically "normal" reference segments in patients undergoing transcatheter therapy for symptomatic coronary artery disease. BACKGROUND: Pathologic studies indicate that the extent of coronary atherosclerosis is underestimated by visual analysis of angiographically normal coronary artery segments. Intravascular ultrasound allows detailed, high quality cross-sectional imaging of the coronary arteries in vivo. METHODS: Intravascular ultrasound was used to study angiographically normal coronary artery reference segments in 884 patients evaluated for transcatheter therapy for symptomatic native coronary artery disease. The reference segment was the most visually normal intravascular ultrasound cross section within 10 mm proximal to the target lesion but distal to any major side branch. Results are presented as mean value +/- 1 SD. RESULTS: Only 60 (6.8%) of 884 angiographically normal reference segments were normal by intravascular ultrasound. Reference segment percent cross-sectional narrowing measured 51 +/- 13% and correlated poorly with the target lesion percent cross-sectional narrowing (r = 0.166, p < 0.0001). Reference segments contained less calcific and dense fibrotic plaque and proportionately more soft plaque elements. Independent predictors of reference segment percent cross-sectional narrowing were male gender, patient age, diabetes mellitus, hypercholesterolemia and presence of multivessel disease. Independent predictors of reference segment calcification were patient age and serum creatinine levels. Reference segment percent cross-sectional narrowing in 723 patients undergoing transcatheter therapy was similar to that in patients studied for diagnostic purposes; however, reference segment arc of calcium was greater in treated patients (43 +/- 81 vs. 25 +/- 57, p = 0.015). Reference segment disease was not an independent predictor of subsequent angiographic restenosis or clinical events within 12 months of follow-up. CONCLUSIONS: Atherosclerosis is ubiquitous in angiographically normal coronary artery reference segments. Reference segment disease parallels the severity of target lesion disease and is associated with many of the conventional risk factors for coronary artery disease. Because of its sensitivity in detecting atherosclerosis in angiographically normal reference segments, intravascular ultrasound should enhance the study of risk factors for atherosclerosis and the results of therapies to control disease progression.

Age Factors↗
PubMed1995

Small stent size and intimal hyperplasia contribute to restenosis: a volumetric intravascular ultrasound analysis.

OBJECTIVES: The purpose of this study was to use volumetric intravascular ultrasound analysis of Palmaz-Schatz stents to assess the in-stent restenotic process. BACKGROUND: By reducing lesion elastic recoil and chronic arterial remodeling, stents improve the long-term results of coronary angioplasty. However, stents are prone to the development of neointimal hyperplasia. Angiographic studies of stent restenosis have suggested that these hyperplastic responses are the cause of in-stent restenosis; however, it is difficult to visualize the radiolucent Palmaz-Schatz stent by angiography. Intravascular ultrasound provides detailed cross-sectional imaging of the coronary arteries, especially the intense metallic reflection of endovascular stents. METHODS: Forty-four patients with 60 Palmaz-Schatz stents underwent intravascular ultrasound imaging at follow-up ([mean +/- SD] 8.8 +/- 7.2 months after implantation). Thirty-four stents were placed in saphenous vein grafts and 26 in native coronary arteries; 30 were placed in restenotic lesions. Intravascular ultrasound with automatic transducer pullback at 0.5 mm/s allowed measurement of stent, lumen and intimal hyperplasia cross-sectional areas at 1-mm axial increments within the stents. Using Simpson's rule, stent, lumen and intimal hyperplasia volumes were calculated. Patterns of in-stent restenosis were then identified. RESULTS: Restenotic stents had smaller stent volumes (120 +/- 41 vs. 147 +/- 43 mm3, p = 0.016) and lumen volumes (62 +/- 28 vs. 118 +/- 42 mm3, p < 0.0001) but larger intimal hyperplasia volumes (58 +/- 36 vs. 29 +/- 18 mm3, p < 0.001) than nonrestenotic stents. A focal restenosis pattern was more common (20 [77%] of 26) than a diffuse restenosis pattern (6 [23%] of 26). Stents with focal restenosis and stents with diffuse restenosis had equally small stent volumes (120 +/- 44 vs. 120 +/- 31 mm3, respectively, p = NS); however, stents with diffuse restenosis had larger intimal hyperplasia volumes (84 +/- 30 vs. 50 +/- 34 mm3, p < 0.05). Focal restenosis was most commonly located at the central articulation (45%); the location of focal restenosis was related to the focal accumulation of neointimal tissue. CONCLUSIONS: Stent volume and magnitude and distribution of intimal hyperplasia are important in the development of in-stent restenosis. Stent volume was smaller and intimal hyperplasia volume greater in restenotic stents. Stent restenosis is more commonly focal in nature and located at the central articulation.

Aged↗
PubMed1995

A modified directional atherectomy catheter for resection of calcified atherosclerotic plaques.

BACKGROUND: The purpose of this study was to determine the feasibility of resecting calcified atherosclerotic plaques in human cadaveric vessels by using a modified directional coronary atherectomy catheter and to correlate these results with bench tests using an in-vitro sea coral model. METHODS: The conventional directional coronary atherectomy catheter was modified by changing the cutter blade to a tungsten carbide material and by increasing the torsional strength of the drive cable. The performance of the modified directional coronary atherectomy (DCA) catheter was compared with the conventional catheter using a sea coral model to simulate calcified material. Then, 10 human ex-vivo arteries (eight with calcification) were treated with both conventional and modified catheters, and the results studied with intravascular ultrasound and confirmed by histologic examination. RESULTS: Using the modified directional coronary atherectomy catheter it was possible to perform effective and consistent longitudinal cutting, and to resect a significantly larger amount of coral (1.0 +/- 0.1 mm2 versus 0.2 +/- 0.1 mm2 with conventional cutter, P < 0.0001). In heavily calcified ex-vivo arteries, the modified catheter was more effective in removing calcified plaques (13 +/- 11 mg versus 3.7 +/- 1.4 mg with conventional cutter, P = 0.07). Intravascular ultrasound confirmed the effective atherectomy (residual area stenosis 28 +/- 16% versus 47 +/- 10% with the conventional device, P < 0.05), and histologic examination showed calcified nodules in the atherectomy samples obtained with the modified cutter (area of calcium 1.43 +/- 0.89 mm2 versus 0.93 +/- 0.83 mm2 with the conventional cutter). CONCLUSIONS: The modified directional coronary atherectomy catheter effectively removed both non-calcified and calcified plaques in the ex-vivo human cadaveric arteries, thus demonstrating the feasibility of directional coronary atherectomy of calcified plaques. This modified device shows promise for treating calcified coronary lesions, especially in larger vessels.

Animals↗
PubMed1994

The contribution of tissue removal to lumen improvement after directional coronary atherectomy.

The contribution of tissue removal to lumen improvement after directional coronary atherectomy remains controversial. The purpose of this study was to validate the intravascular ultrasound measurement of plaque volume and use it to study the contribution of tissue removal to lumen improvement after directional coronary atherectomy. With use of intravascular ultrasound, 12 human coronary vessels were imaged in vitro. With use of computer-assisted planimetry, the external elastic membrane and lumen cross-sectional areas were manually traced and the plaque+media area was calculated at 1 mm axial intervals. Then, plaque+media volume was calculated by Simpson's rule. After imaging, ultrasound measurements of plaque+media volume were compared with histologic measurements. Similarly, volumetric intravascular ultrasound imaging was performed before and after directional atherectomy in 47 patients. In vitro, the mean plaque+media volume measured by intravascular ultrasound was 134.0 +/- 94.8 mm3 and compared well with that derived by histology (187.4 +/- 128.8 mm3, r = 0.96, p < 0.001). In vivo, the lumen volume increased from 27.2 +/- 12.3 to 58.7 +/- 30.3 mm3, and the mean plaque+media volume decreased from 122.0 +/- 74.0 to 97.5 +/- 63.5 mm3. The mean intravascular ultrasound atherectomy index was 76 +/- 23%. In 11 of the 47 patients (23.4%), tissue removal alone accounted for lumen improvement. Volumetric intravascular ultrasound image analysis indicates that the mechanism of directional coronary atherectomy primarily is tissue removal. As a result, the contribution of arterial remodeling (expansion and dissection) probably is less important.

Aged↗
PubMed1994

Limitations of angiography for analyzing coronary atherosclerosis progression or regression.

PURPOSE: To analyze the utility and limitations of serial coronary angiography for determining atherosclerosis progression and regression. DATA SOURCES: A MEDLINE search of the English-language literature (1966 to January 1994) using the keywords atherosclerosis regression, atherosclerosis progression, lipid reduction therapy, and coronary angiography. STUDY SELECTION: Selected articles on the effects of cholesterol reduction and lifestyle modification on angiographic coronary artery disease, on the animal models of atherosclerosis progression and regression, and on the limitations of coronary angiography. DATA EXTRACTION: Independent extraction by two authors. RESULTS: Although several studies have reported that the rate of atherosclerosis progression, defined by serial coronary angiography, can be reduced and that luminal diameter can be improved somewhat by aggressive lipid modification, the reported changes are small (0.3 mm or 10% change) and have required a prolonged study duration (range, 1 to 10 years). More importantly, angiography simply does not measure atherosclerosis and cannot assess lesion composition. Angiography also underestimates the extent of atherosclerosis, especially in angiographically normal segments. In addition, difficulties with data acquisition, such as substantial variabilities in serial measurements of percent diameter stenosis and minimal luminal diameters, require large sample sizes to show statistically significant regression, even with computerized quantification. CONCLUSIONS: Given its current limitations, serial coronary angiography is not a satisfactory means of detecting atherosclerosis progression or regression.

Anticholesteremic Agents↗