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Biomedical subjects

K M Kent

Publications and source records attributed to K M Kent.

At least 127 records · Page 7Linked to original sources
PubMed1996

Intravascular ultrasound findings after excimer laser coronary angioplasty.

Intravascular ultrasound (IVUS) was used to study 104 lesions in 98 patients after excimer laser coronary angioplasty (ELCA). Lesion site external elastic membrane (EEM) and lumen cross-sectional areas (CSA) were measured; plaque+media (P+M = EEM - lumen) CSA and percentage of cross-sectional narrowing (CSN = P+M CSA/EEM CSA) were calculated; and the results were compared to a reference site. The lumen CSA (2.6 +/- 1.0 mm2) averaged 24% larger than the cross-sectional area of the largest laser catheter used, and 64 lesions (62%) fit the definition of arterial expansion (lesion EEM CSA > reference site EEM CSA). The residual percentage of cross-sectional narrowing averaged 83.8 +/- 8.8%. Dissections were present in 44% of lesions, and were more common in lesions with superficial calcium (59%) than in lesions with only deep calcium (31%) or no calcium (20%, P = 0.0102). Dissections of superficial calcified plaque had an unusual "shattered" or "fragmented" appearance. These findings suggest that excimer laser angioplasty causes forced vessel expansion with dissection, but limited atheroablation.

Angioplasty, Balloon, Laser-Assisted↗
PubMed1996

Femoral artery hemostasis using an implantable device (Angio-Seal) after coronary angioplasty.

Coronary catheter interventional procedures are associated with risk of access site complications. We report our experience with Angio-Seal, an implantable hemostasis device, when used in the femoral artery after coronary angioplasty procedures. Sixty-eight patients were studied. Their average age was 63 years; 84% of the patients were male. All had 8 French access sheaths and received bolus heparin (mean dose 12,690 U). The arterial sheaths were removed an average of 455 min after the conclusion of the procedure, when the activated clotting time was 220 +/- 94 sec (range 97-503 sec). The hemostasis device was successfully deployed in 63 patients (93%). The average time to achieve complete arterial hemostasis was 4.4 +/- 8.9 min (range 0-45). Immediate, total hemostasis without requiring any form of external pressure was obtained in 37 of these patients (54%). the incidence of complications was as follows: significant bleeding occurred in 9 patients (13%); there were 2 hematomas (3%); there were no vascular or infectious complications. One device embolization occurred when the connecting suture broke and the intravascular anchor was lost; no clinical sequelae resulted, and manual hemostasis was successful. In four other patients, the device did not deploy and was removed entirely, followed by uneventful manual hemostasis. Follow-up for 2 months revealed no late sequelae in any patient, and complete absorption of the device was documented by ultrasound study in all cases. We conclude that this implantable device can achieve arterial hemostasis quickly and safety when used in anticoagulated patients after coronary interventional procedures.

Aged↗
PubMed1996

Mechanisms and immediate and long-term results of adjunct directional coronary atherectomy after rotational atherectomy.

OBJECTIVES: The purpose of this study was to confirm the mechanisms and the immediate and long-term results of rotational atherectomy and adjunct directional coronary atherectomy. BACKGROUND: Rotational atherectomy is best suited for treating calcific stenoses, but the ability of rotational atherectomy alone to optimize lumen dimensions in large vessels is limited; this is only partly improved by adjunct balloon angioplasty. METHODS: We treated 165 lesions in 163 patients by use of rotational atherectomy and adjunct directional coronary atherectomy. Quantitative angiography and intravascular ultrasound were used for lesion analysis. A matched comparison with 208 lesions treated with rotational atherectomy and adjunct coronary angioplasty was performed. Patients were then followed up for at least 9 months, and target-lesion revascularization was assessed. RESULTS: In the 61 lesions imaged sequentially, lumen area increased from 1.7 +/- 0.8 (mean +/- 1 SD) to 3.9 +/- 1.1 mm(2) after rotational atherectomy, owing to a decrease in plaque plus media area from 16.8 +/- 5.0 to 15.2 +/- 5.2 mm(2) (both p < 0.0001). After adjunct directional coronary atherectomy, lumen area increased even more to 6.7 +/- 2.0 mm(2) (vs. 5.1 +/- 1.4 mm(2) after adjunct coronary angioplasty, p < 0.0001) as a result of both vessel expansion (18.8 +/ 5.3 to 20.8 +/- 5.7 mm(2)) and additional plaque removal (to 14.1 +/- 5.0 mm(2), all p < 0.0001). The total arcs of calcium decreased from 207 +/- 107 degrees to 166 +/- 93 degrees after rotational atherectomy and to 145 +/- 87 degrees after directional coronary atherectomy. Overall, procedural success was 96%, and final diameter stenosis was 15 +/- 17%. Target-lesion revascularization was 23%. The only independent predictor of target-lesion revascularization was a larger overall atherectomy index (84% vs. 59%, p = 0.048). CONCLUSIONS: There is a synergistic relationship between rotational atherectomy and directional coronary atherectomy in the treatment of calcific lesions. The immediate results show a high procedural success--lumen dimensions were larger and late target-lesion revascularization was lower in lesions treated with rotational atherectomy and directional coronary atherectomy than in those treated with rotational atherectomy and adjunct balloon angioplasty.

Aged↗
PubMed1996

Intravascular ultrasound predictors of restenosis after percutaneous transcatheter coronary revascularization.

OBJECTIVES: This study sought to evaluate preintervention and postintervention intravascular ultrasound studies for potential predictors of angiographic restenosis and to use ultrasound predictors of restenosis to enhance our understanding of the pathophysiology of the restenosis disease process. BACKGROUND: Restenosis remains the major limitation of percutaneous transcatheter coronary revascularization. Although its mechanisms remain incompletely understood, numerous studies have identified some of the clinical, anatomic and procedural risk factors for restenosis. Intravascular ultrasound imaging of target lesions before and after catheter-based treatment consistently demonstrates more target lesion calcium, more extensive reference segment atherosclerosis, smaller final lumen dimensions, significant residual plaque burden and a greater degree of tissue trauma than is evident by angiography. METHODS: Intravascular ultrasound studies were performed in 360 nonstented native coronary artery lesions (final diameter stenosis 18 +/- 11%) in 351 patients for whom follow-up angiographic data were available 6.4 +/- 3.6 months later. Hospital charts were reviewed, and qualitative and quantitative coronary angiographic and intravascular ultrasound analyses were performed by independent core laboratories. Four dependent angiographic end points were tested: restenosis as a binary definition (> or = 50% diameter stenosis at follow-up) was the primary end point; follow-up diameter stenosis, late lumen loss and follow-up minimal lumen diameter were the secondary end points. RESULTS: Reference vessel size, the preintervention quantitative coronary angiographic assessment of lesion severity and the postintervention intravascular ultrasound cross-sectional measurements predicted the late angiographic results. In particular, the intravascular ultrasound postintervention cross-sectional narrowing (plaque plus media cross-sectional area divided by external elastic membrane cross-sectional area) predicted the primary end point (restenosis) and two of the three secondary end points (follow-up diameter stenosis and late lumen loss) and was therefore the most consistent predictor of restenosis. CONCLUSIONS: Intravascular ultrasound variables are more powerful and consistent predictors of angiographic restenosis than currently accepted clinical or angiographic risk factors.

Adult↗
PubMed1996

Effect of rotational atherectomy in noncalcified atherosclerotic plaque: a volumetric intravascular ultrasound study.

OBJECTIVES: This study used pre-rotational and post-rotational atherectomy volumetric intravascular ultrasound analysis to determine whether rotational atherectomy causes ablation of non-calcified atherosclerotic plaque. BACKGROUND: Rotational atherectomy is currently the preferred treatment for heavily calcified coronary lesions. However, the mechanism of lumen enlargement in noncalcified lesions has not been studied in detail. Intravascular ultrasound allows detailed, cross-sectional imaging of the coronary arteries in vivo. The normal coronary artery wall, the major components of the atherosclerotic plaque and the quantitative changes in vessel, lumen and plaque cross-sectional areas and volumes that occur as a result of the atherosclerotic disease process and during transcatheter therapy can be studied in a manner otherwise not possible. METHODS: Eighteen noncalcified native vessel lesions in 18 patients were imaged before and after rotational atherectomy using intravascular ultrasound systems incorporating motorized transducer pullback through a stationary imaging sheath. External elastic membrane, lumen and plaque plus media cross-sectional areas were measured every 1 mm of lesion length (for a total of 10 image slices), and external elastic membrane, lumen and plaque plus media volumes were calculated using Simpson's rule. RESULTS: After rotational atherectomy, the minimal lumen cross-sectional area increased from 1.37 +/- 0.50 to 2.99 +/- 0.60 mm2 (mean value +/- 1 SD, p < 0.0001). Lumen volume increased from 23.2 +/- 9.0 to 38.0 +/- 8.0 mm3 (p < 0.0001) as a result of a decrease in plaque plus media volume (from 102.2 +/- 50.9 to 85.8 +/- 47.7 mm3, p < 0.0001), with no change in total vessel (external elastic membrane) volume (125.3 +/- 54.2 to 123.8 +/- 52.9 mm3, p = 0.119). CONCLUSIONS: Rotational atherectomy effectively ablates noncalcified plaque in non-calcium-containing lesions.

Atherectomy, Coronary↗
PubMed1996

Safety and efficacy of elective stent implantation following rotational atherectomy in large calcified coronary arteries.

Rotational atherectomy is an effective transcatheter therapy for calcified coronary lesions. In large (> 3-mm) calcified coronary arteries, stent implantation following rotational atherectomy may further improve acute and especially, long-term benefit. To determine the safety and efficacy of this device synergy approach, we studied 24 consecutive patients undergoing this procedure electively in native coronary arteries. Procedural success was achieved in 100% without any major ischemic complications. There was also no incidence of subacute thrombosis or cardiac event during 30-day follow-up period. Thus, we conclude that elective stent implantation following rotational atherectomy in large, calcified coronary arteries is safe and results in excellent clinical benefit up to 30 days.

Aged↗
PubMed1996

An overview of US coronary stent trials.

Since the introduction of coronary stent procedures in the US there has been a determined effort to understand appropriate clinical applications better through the use of carefully designed prospective clinical trials. These studies fall into the general categories of efficacy studies, pharmacology, studies, intravascular ultrasound studies, adjuvant stent therapy studies, stent versus stent studies and new stent registries. Most of the pivotal clinical trials have been randomized controlled studies, but there have also been several carefully performed registry analyses which have provided useful insights. There are ample data to support the use of stents for abrupt and threatened closure syndrome. STRESS (the STent REStenosis Study) helped to establish the 'anti-restenosis' efficacy of elective Palmaz-Schatz coronary stent placement in native coronary arteries, although secondary complications (subacute stent thrombosis, bleeding and vascular events) were disturbing owing to excessive systemic anticoagulation regimens. Subsequent studies, often using intravascular ultrasound guidance, have clearly indicated that optimal stent implantation requiring post-stent high-pressure dilatations combined with aggressive antiplatelet therapy (aspirin plus ticlopidine) provides the best early and late clinical outcomes. Many of these observations have now been extended to other lesion subsets including saphenous vein grafts. In the future, stent adjuvant therapies will be carefully evaluated, including pharmacological agents, intravascular irradiation, and pre-stent atheroablation. Finally, interstent comparisons of randomized clinical trials are ongoing and there are several new stent registries which will help to extend the frontiers of clinical applications and operator technique.

Angioplasty, Balloon, Coronary↗
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↗