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Biomedical subjects

D S Baim

Publications and source records attributed to D S Baim.

At least 109 records · Page 6Linked to original sources
PubMed1994

Effects of cocaine on carotid vascular reactivity in swine after balloon vascular injury.

BACKGROUND AND PURPOSE: The use of cocaine has been associated with stroke. To evaluate carotid vasospasm as a potential mechanism of cocaine-induced stroke, we studied 12 swine immediately and 10 weeks after angioplasty. METHODS: We compared the short- and long-term vasoconstrictor responses of normal and injured arterial segments to nitroglycerin, histamine, and cocaine in vivo by carotid angiography. We also compared the isometric contractile force responses to different vasoactive substances in normal and injured vascular rings in vivo, and we tested the direct action of cocaine on both arterial segments. RESULTS: In in vivo studies, immediately after angioplasty, luminal diameter in the control segment decreased by 30% with histamine 30 micrograms/kg and by 23% with cocaine 10 mg/kg (P < .001). In contrast, neither histamine nor cocaine produced vasoconstriction in the angioplasty segment. Thus, a transient loss of vasoconstriction occurred at the angioplasty site. Ten weeks later, histamine 30 micrograms/kg significantly (P < .001) decreased luminal diameter by 34% in the control and by 33% in the angioplasty segment; similarly, cocaine 10 mg/kg significantly (P < .001) decreased luminal diameter by 26% in the control and by 34% in the angioplasty segment. Thus, 10 weeks after angioplasty, the transitory loss of carotid vasoconstriction in response to histamine and cocaine reverted, and a moderate generalized vasoconstriction occurred in both segments without localized vasospasm. In vitro, the maximal isometric tension responses to KCl, acetylcholine, histamine, and phenylephrine were similar in vascular rings from normal and angioplasty segments. The median effective doses to histamine and phenylephrine were similar. In contrast, cocaine in concentrations from 10(-7) to 10(-3) mol/L failed to produce any isometric contraction in vitro. CONCLUSIONS: Cocaine in vivo produced a generalized carotid vasoconstriction without evidence of localized vasospasm; since there was no response to cocaine in vitro, the in vivo effect was most likely mediated by neurohumoral factors rather than by a direct action of cocaine on vascular smooth muscle.

Angioplasty, Balloon↗
PubMed1993

Coronary revascularization after myocardial infarction in the very elderly: outcomes and long-term follow-up.

OBJECTIVE: To determine the outcome of very elderly patients who had coronary revascularization during hospitalization for an acute myocardial infarction. DESIGN: Retrospective cohort study. SETTING: Community-based tertiary-care teaching hospital. PATIENTS: A total of 1215 consecutive patients 80 years and older were hospitalized with a myocardial infarction between 1985 and 1990. The study sample included all 93 patients (8%) who had cardiac catheterization before discharge and had not been excluded from study because of the following: severe valvular disease, absence of significant coronary disease, or death before a decision about revascularization could be made. MEASUREMENTS: Survival, quality of life, and functional status at least 1 year after discharge. RESULTS: After catheterization, 41 patients had angioplasty, 18 had coronary artery bypass surgery, and 34 did not have revascularization. Among the patients alive at discharge, those who had revascularization had a high likelihood of achieving a good or excellent quality of life (angioplasty, 86% [31 of 36]; surgery, 89% [16 of 18]; medical therapy, 44% [11 of 25]) and of being able to care for themselves (angioplasty, 89% [32 of 36], surgery, 89% [16 of 18], medical therapy, 52% [13 of 25]). Mortality rates at 1 year were 24% (95% CI, 15% to 47%) for the angioplasty group, 6% (CI, 0% to 27%) for the surgery group, and 44% (CI, 27% to 62%) for the medical therapy group. In a Cox proportional hazards model that adjusted for clinical, demographic, hemodynamic, and anatomic differences between the groups, the performance of coronary revascularization was associated with increased survival (hazard ratio, 0.42; CI, 0.18 to 0.98). CONCLUSIONS: A small percentage of very elderly patients with complicated acute myocardial infarctions, selected by their physicians for invasive cardiovascular procedures, can tolerate these procedures, avoid serious complications, return to independent living, and have excellent probability of survival. Although our results suggest that coronary revascularization may have benefited these patients, the study design did not permit definite conclusions, and future studies are needed to resolve this important question.

Aged↗
PubMed1993

Results of directional coronary atherectomy during multicenter preapproval testing. The US Directional Coronary Atherectomy Investigator Group.

Between 1988 and 1990, clinical testing was performed at 12 US institutions using the Simpson Coronary AtheroCath under an Investigational Device Exemption. Data on 1,069 lesions (873 patients) were analyzed and presented to the Food and Drug Administration (FDA) advisory panel in the summer of 1990, forming the basis for approval of this device in September 1990. Analysis of these preapproval data shows a primary success rate of 85% (defined as tissue removal, > or = 20% reduction in stenosis, < 50% residual stenosis after directional atherectomy, and no major complication), with somewhat higher primary success in prior restenosis and noncalcified lesions. Including the use of conventional angioplasty performed after atherectomy, the overall success rate was 92%. One or more major complications occurred in 4.9% of procedures, and included death (0.5%), nonfatal Q-wave myocardial infarction (0.9%), and emergency bypass surgery (4.0%). These complications were more frequent in right coronary, de novo, and diffuse (> 20-mm length) lesions. Six-month angiography results were available in 384 (77%) of 498 lesions eligible for follow-up when the registry closed and showed a restenosis rate (late stenosis > 50%) of 42%. The restenosis rate in both native vessels (30 vs 46%) and bypass grafts (31 vs 68%) was lower in primary (de novo) lesions compared with lesions that had developed restenosis after a prior intervention. Despite the use of prototype atherectomy catheters and still evolving procedural technique, this preapproval experience provided an important initial indication of the situations in which directional coronary atherectomy was most useful and helped set clear standards for performance of this procedure following FDA approval.

Atherectomy, Coronary↗
PubMed1993

Directional coronary atherectomy of saphenous vein graft narrowings: multicenter investigational experience.

Directional coronary atherectomy (DCA) of saphenous vein graft lesions was performed at 21 centers between June 1988 and September 1990, which represents the multicenter investigational experience. A total of 318 procedures were performed and 363 vein graft lesions were treated. Angiographic success with DCA was achieved in 86% of lesions and clinical success was achieved in 85% (269 of 318) of patients. Major complications occurred in 2.5% of patients, with Q wave myocardial infarction (MI) in 1.3%, death in 0.9%, and urgent bypass surgery in 0.9%. Other complications included non-Q wave MI in 4.4%, distal embolization in 7.2%, coronary occlusion in 1.9%, and vessel perforation in 0.6%. Although there was a trend toward lower success rates with ostial vein graft lesions (82% vs 88% for other graft sites) and with diffuse (length > 20 mm) graft lesions (75% vs 87% for shorter lesions), the differences were not significant. Baseline clinical and angiographic factors did not identify predictors of lower success or more frequent complications in the study group. Overall restenosis rate in the 149 patients with angiographic restudy was 57%. The restenosis rate was significantly lower with primary vein graft lesions (38%) compared with a 75% restenosis rate for grafts with prior restenosis, p < 0.001. This initial multicenter investigational experience indicates that directional coronary atherectomy is a safe and effective therapy for selected saphenous vein graft disease. Although the overall restenosis rate is relatively high, the restenosis rate following DCA of primary vein graft lesions is significantly lower than for vein grafts having had prior intervention.(ABSTRACT TRUNCATED AT 250 WORDS)

Atherectomy, Coronary↗
PubMed1993

Specific indications for directional coronary atherectomy: origin left anterior descending coronary artery and bifurcation lesions.

Directional coronary atherectomy is emerging as the treatment of choice for many patients with significant lesions involving left anterior descending coronary artery origin or vessel bifurcations. It offers the potential advantages of safe, reliable, and predictable treatment of these selected complex lesions. Future modifications and improvements in the design of the atherectomy device (AtheroCath; Devices for Vascular Intervention, Redwood City, CA) may further expand its application to smaller and calcified vessels.

Angioplasty, Balloon, Coronary↗
PubMed1993

Complications of directional coronary atherectomy: incidence, causes, and management.

An assessment of complications is essential to the evaluation of directional coronary atherectomy. Major complications--such as death, Q wave myocardial infarction, or the need for emergency bypass surgery to correct acute vessel closure--result from a variety of familiar mechanisms, including dissection, thrombosis, or guiding catheter injury. In addition, unique complications of this device, such as catheter nose cone injury or vascular perforation, may also result in severe ischemia. With prompt recognition of the cause, most ischemic complications can be successfully treated in the catheterization laboratory. Less severe complications, such as femoral vascular injury, also require recognition and appropriate treatment in order to minimize sequelae. Although several large series have now documented that the overall incidence of atherectomy complications appears similar to that reported for conventional balloon angioplasty, no direct comparisons can be made until randomized trials (such as Coronary Angioplasty Versus Excisional Atherectomy Trial [CAVEAT]) are analyzed, to control for potential demographic or lesion-specific influences on complication rates.

Atherectomy, Coronary↗
PubMed1993

Directional coronary atherectomy: how much lumen enlargement is optimal?

Until recently, it has not been clear how much of the effect of directional coronary atherectomy is due to tissue removal per se, and whether the long-term results of the procedure are helped or harmed when the operator attempts to obtain the "near zero percent" residual stenosis of which this technique is capable. This article summarizes the findings of a series of studies that have addressed these important questions and proposes a prescription for the optimal performance of directional atherectomy. Analysis of retrieved tissue weights compared with measured increases in luminal volume shows that about half of the improvement seen after directional atherectomy results from mechanical dilation. Because this "facilitated" dilation appears to take place within the bases of the trenches created by atherectomy cuts (rather than being randomly distributed in fractures throughout the plaque substance), a larger and smoother lumen is possible compared with that seen after conventional balloon dilation. Although the recovery of deep vessel wall components (media and even adventitia) is common, it generally does not cause either acute complications (i.e., perforation) or increase the probability of subsequent restenosis. Rather, reduction in the probability of late restenosis appears to be most directly related to the ability of directional atherectomy to provide the largest acute luminal diameter safely possible, thus providing better tolerance of subsequent intimal hyperplasia before hemodynamically significant renarrowing results at the treatment site.

Angioplasty, Balloon, Coronary↗
PubMed1993

Balloon postdilation can safely improve the results of successful (but suboptimal) directional coronary atherectomy.

This study investigates whether adjunctive balloon angioplasty can be safely used to improve acute results in cases where directional coronary atherectomy alone has provided a successful (but suboptimal) outcome. Between October 1, 1990, and October 1, 1992, directional coronary atherectomy was performed successfully in 198 of 228 lesions. Individual operators believed that most acute results were satisfactory after atherectomy alone (group I, n = 115) with a minimal lumen diameter that increased from 0.82 +/- 0.45 to 3.21 +/- 0.65 mm after atherectomy, for an acute gain in lumen diameter of 2.39 +/- 0.73 mm and a residual stenosis of 6 +/- 13%. In 42% of lesions (group II, n = 83), however, results were considered suboptimal after atherectomy alone, with a minimal lumen diameter that increased from 0.85 +/- 0.45 to 2.83 +/- 0.64 mm, a smaller acute gain of 1.96 +/- 0.72 mm, and a mean residual stenosis of 17 +/- 14% (although all residual stenoses were < 50%, 19% had a residual stenosis > 30%). Adjunctive balloon angioplasty in these group II lesions provided an additional gain of 0.34 +/- 0.38 mm, bringing the total acute gain for group II lesions to 2.32 +/- 0.78 mm and the residual stenosis to 9 +/- 13%, similar to that of group I patients who underwent atherectomy alone. This strategy resulted in a 7 +/- 13% overall residual stenosis for the study population, with no higher incidence of periprocedural complications or adverse late clinical outcomes in group II patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Angioplasty, Balloon, Coronary↗
PubMed1993

Histologic analysis of directional coronary atherectomy samples. A review of findings and their clinical relevance.

Histologic analysis of atherectomy samples from > 400 patients who received directional coronary atherectomy at 3 separate institutions disclosed 2 major categories of tissue: atherosclerotic plaque (with or without thrombus) and intimal proliferation (hyperplasia, with or without thrombus). The predominant tissue type in atherectomy samples from native, primary, or de novo coronary artery stenoses was atherosclerotic plaque. The predominant tissue type in atherectomy samples from restenosis lesions (prior balloon angioplasty, atherectomy, or both) was intimal proliferation with variable amounts of atherosclerotic plaques (with or without thrombus). Deep vessel wall components (media, adventitia) were identified at varying frequencies. The clinical relevance of atherectomy tissue is reviewed.

Atherectomy, Coronary↗
PubMed1993

New devices for coronary revascularization.

A variety of instruments, including atherectomy catheters, intra-arterial stents, and lasers, have been developed in order to outdo balloon angioplasty with regard to procedural success, complications, and restenosis. Controlled trials are needed to assess the newcomers, but it is likely that each type of device will find its own clinical niche rather than supersede the others.

Angioplasty, Balloon, Coronary↗
PubMed1993

Frequency and consequences of intimal hyperplasia in specimens retrieved by directional atherectomy of native primary coronary artery stenoses and subsequent restenoses.

Although intimal hyperplasia is a frequent occurrence after arterial interventional procedures, the overall frequency and significance of intimal hyperplasia in primary coronary lesions has not been previously addressed. The incidence of intimal hyperplasia was therefore examined using standard light microscopy in specimens obtained from native coronary arteries of patients undergoing directional coronary atherectomy. The associated clinical history, angiographic results and clinical outcomes were also tabulated. Intimal hyperplasia was identified in 51 of 55 patients (93%) treated with directional coronary atherectomy for restenosis after a prior intervention. These restenosis lesions had less acute gain in lumen diameter after directional coronary atherectomy, a smaller late lumen diameter, more severe late stenosis (p < 0.04), and tended to have more restenosis defined as late stenosis > or = 50% (restenosis rate 40% for prior restenosis vs 26% for primary lesions). Surprisingly, however, intimal hyperplasia was also identified in 45 of 102 (44%) primary stenoses. Primary lesions (n = 45) with intimal hyperplasia were more likely to occur in younger patients and in the left anterior descending artery than were either primary lesions without intimal hyperplasia (n = 57) or prior restenosis lesions. There were otherwise no differences in the baseline characteristics, angiographic findings or clinical outcome of primary lesions with or without intimal hyperplasia (restenosis rate 28 and 24%, respectively). The event-free survival (72% at 12 months) was similar in all 3 groups. Thus, even though intimal hyperplasia is an almost universal finding in restenosis lesions, intimal hyperplasia is not specific for restenosis since histologically identical hyperplasia may be found in nearly half of primary coronary artery stenoses.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Relation between activated smooth-muscle cells in coronary-artery lesions and restenosis after atherectomy.

BACKGROUND: Neointimal proliferation leading to restenosis frequently develops after coronary angioplasty. This process is associated with a change in vascular smooth-muscle cells from a contractile (quiescent) phenotype to a synthetic or proliferating (activated) one. We investigated whether the presence of activated smooth-muscle cells in coronary lesions at the time of coronary atherectomy predisposes patients to subsequent restenosis. METHODS: We used in situ hybridization to study the expression of messenger RNA in coronary-atherectomy specimens from 20 patients. Plaque material was hybridized with a probe for the B isoform of human nonmuscle myosin heavy chain, a major nonmuscle myosin isoform in activated, but not quiescent, smooth-muscle cells. Angiographic follow-up data were obtained a mean (+/- SD) of 174 +/- 54 days after atherectomy in 16 of the 20 patients, and the extent of recurrent luminal narrowing was analyzed quantitatively. The presence of restenosis was assessed by exercise thallium scintigraphy in the other four patients. RESULTS: Atherectomy specimens from 10 of the 20 patients showed hybridization with the probe, defined as the clustering of more than 20 silver grains per cell nucleus in more than 10 nuclei in five high-power fields (x250); specimens from the other 10 patients showed no such hybridization. At follow-up, restenosis had developed in 8 of the 10 patients with positive hybridization results, but was absent in 9 of the 10 patients with negative results (P = 0.007). The degree of late loss in luminal diameter was significantly higher in patients with positive hybridization results than in those with negative results (ratio of late loss to immediate gain after atherectomy, 0.76 +/- 0.3 vs. 0.36 +/- 0.3; P < 0.001). CONCLUSIONS: We conclude that the expression of the B isoform of nonmuscle myosin heavy chain is increased in some coronary atherosclerotic plaques and that this increase in expression identifies a group of lesions at high risk for restenosis after atherectomy.

Adult↗
PubMed1993

Restenosis after arterial injury caused by coronary stenting in patients with diabetes mellitus.

OBJECTIVE: To determine whether diabetic patients, when compared with nondiabetic patients, have a higher incidence of restenosis after coronary stenting, and, if so, whether restenosis is attributable to lesion or procedural differences or to a greater biologic tendency for late loss of minimum diameter in diabetic patients. DESIGN: Case series. SETTING: Tertiary care referral center. PATIENTS: Two hundred twenty consecutive patients with coronary artery disease who were referred for placement of a Palmaz-Schatz stent in either a native coronary artery or a saphenous vein graft. RESULTS: Based on a traditional dichotomous definition of restenosis (> or = 50% stenosis at follow-up), lesions in diabetic patients had a significantly greater restenosis rate (55%) than lesions in nondiabetic patients (20%; P = 0.001). Vessel size, lesion length, pre-procedure lesion severity, procedural outcome, and acute gain (the difference between minimum lumen diameter before and after the procedure) were similar in the diabetic and nondiabetic groups. However, at follow-up, stents in diabetic patients had a smaller lumen diameter (1.66 +/- 1.18 mm) compared with those in nondiabetic patients (2.24 +/- 0.93 mm; P = 0.004), as well as a greater percent stenosis (49% compared with 32%; P = 0.002). Thus, the increased restenosis rate in stents in diabetic patients (55% compared with 20%; P = 0.001) is secondary to increased late loss of minimum lumen diameter (1.66 +/- 1.28 mm compared with 1.23 +/- 0.97 mm; P = 0.04). CONCLUSIONS: After arterial injury produced by stent placement, diabetic patients have a significantly greater incidence of restenosis because of greater late loss at the treatment site. Because elastic recoil or vasospasm contributes little to stent restenosis, the increased late loss of minimum lumen diameter in diabetic patients suggests that they have a greater predisposition to intimal hyperplasia.

Aged↗
PubMed1993

Mechanisms of restenosis and redilation within coronary stents--quantitative angiographic assessment.

OBJECTIVES: This study was designed to assess the relative contributions of intimal hyperplasia and stent compression to the lumen narrowing seen after intracoronary stenting and to determine whether the lumen enlargement produced by angioplasty of in-stent restenosis results primarily from compression or extrusion of intimal hyperplasia through the stent or from additional stent expansion. BACKGROUND: Palmaz-Schatz stent placement outwardly displaces plaque and eliminates elastic vessel recoil to provide a large and smooth lumen. Some degree of late lumen narrowing occurs within each stent and causes significant restenosis (> or = 50% stenosis) in 25% to 30% of treated lesions. It has not been clear, however, whether this narrowing results from stent compression (crush) or from in-stent intimal hyperplasia. Because the Palmaz-Schatz stent has a distinct radiographic shadow, it is possible to determine the late diameter of both the stent and the enclosed vessel lumen to assess the relative contributions of these two processes. METHODS: From cineangiograms, initial (after stenting) and late (follow-up) lumen and stent diameters were examined in 55 patients (59 stents, group I) who had both immediate and 6-month (192 +/- 117 days) angiography. Lumen and stent diameter were also examined before and after dilation in 30 patients (30 stents, group II) who underwent angioplasty of severe in-stent restenosis. RESULTS: Late loss in minimal lumen diameter was 0.99 +/- 0.87 mm for group I despite only a slight (0.03 +/- 0.23-mm) reduction in the corresponding stent diameter. After redilation for in-stent restenosis, the acute gain in minimal lumen diameter was 1.51 +/- 0.82 mm for group II, again without appreciable increase (0.06 +/- 0.20 mm) in stent diameter. CONCLUSIONS: Restenosis after intracoronary Palmaz-Schatz stenting appears to be due predominantly to lumen encroachment by intimal hyperplasia within the stent, with minimal contribution of stent compression. Lumen enlargement after coronary angioplasty of in-stent restenosis appears to be due primarily to compression or extrusion of intimal hyperplasia through the stent, or both, rather than to further stent expansion.

Aged↗