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Biomedical subjects

L W Klein

Publications and source records attributed to L W Klein.

At least 19 recordsLinked to original sources
PubMed2000

A simplified lesion classification for predicting success and complications of coronary angioplasty. Registry Committee of the Society for Cardiac Angiography and Intervention.

In 1988, the American College of Cardiology/American Heart Association (ACC/AHA) Task Force on Assessment of Diagnostic and Therapeutic Cardiovascular Procedures presented a classification of coronary lesions utilizing 26 lesion features to predict the success and complications of balloon angioplasty. Using data from the Registry of the Society for Cardiac Angiography and Interventions (SCAI) we evaluated the ability of this classification to predict success and complications. Lesion success, death in hospital, emergency cardiac bypass surgery, and major adverse events were evaluated in 41,071 patients who underwent single-vessel angioplasty from January 1993 to June 1996. Logistic models using the ACC/AHA lesion classification, vessel patency, or both, were compared. A new classification based on the interaction of the ACC/AHA classification plus lesion patency was compared with the existing ACC/AHA classification. Vessel patency, added to the ACC/AHA classification, improved prediction of lesion success (p </=0.0001). Class A and patent B lesions had similar success and complication rates, so a simplified classification (SCAI) using only 7 lesion characteristics could be created. This system (I: non-C patent, II: C patent, III: non-C occluded, and IV: C occluded) improved prediction of lesion success compared with the ACC/AHA classification (Bayesian Information Criterion statistic: ACC/AHA 16539, SCAI 15956; and area under the receiver- operating characteristics curve 0.659, 0.693, respectively). The SCAI classification was preferred for predicting major complications and in-hospital death and was similar to the ACC/AHA classification for predicting emergency bypass surgery.

Aged↗
PubMed2000

An unusual mechanism of coronary stent dislodgment and localization.

Stent dislodgment from its delivery catheter is a rare yet clinically important entity in cardiac catheterization. We report a highly unusual case of stent loss and subsequent localization in the guiding catheter. Our hypothesized mechanism of stent dislodgment should be recognized by the medical community.

Aged↗
PubMed2000

The relative influence of lesion length and other stenosis morphologies on procedural success of coronary intervention.

As coronary interventional technology improves, the influence of lesion length (LL) on procedural success and device selection may vary. Thus, the authors prospectively analyzed 957 consecutive coronary interventions (CI) in 1,404 stenoses to ascertain the influence of lesion length on CI outcome. Stenosis morphology was prospectively classified by the AHA/ACC criteria. LL was analyzed both as dichotomous (S: < 10 mm, L: > 10 mm) variables and by the three-tiered AHA/ACC criteria (I: < 10 mm, II: 10-20 mm, III: > 20 mm). There was a significant univariate relationship between CI success and S stenosis (S: 95.8% vs L: 91.8%, p = 0.002 and I: 96.0%, II: 91.7%, III: 89.3%). Numerous interrelationships involving the morphologic characteristics were noted: lesion morphologies associated with S lesions were concentric (p = 0.0001) and had smooth contour (p = 0.0001), ostial location (p = 0.05) and little calcification (p = 0.0007), while irregular contour (p=0.0001), calcification (p=0.0076), eccentric (p=0.0001), thrombus (p = 0.0001), recent (p = 0.0001) or chronic (p = 0.001) total occlusion were associated with L lesions. When these relationships were taken into account by multiple logistic regression analysis, lesion length was not predictive of procedural outcome (p = 0.099). One morphologic type was associated with increased CI success: irregular contour (p = 0.022); recent (p < 0.0001) or chronic (< 0.0001) occlusions were associated with decreased CI success. Another factor considered was device selection: S lesions were associated with greater balloon angioplasty usage (p = 0.002), whereas more coronary stents (p = 0.024) and rotoblator (p = 0.018) devices were used in L lesions. More balloon angioplasty was performed in concentric (p < 0.0001) lesions; interventional devices were employed more often in eccentric (p < 0.0001) and irregular lesions (p < 0.0001). More complications were noted in lesions with thrombus (p = 0.0002), but lesion length was not predictive (p = NS). Lesion length is not a significant predictor of procedural success when adjusted for other lesion morphologies in the modern interventional era. The availability of new devices has improved the results in longer lesions since the AHA/ACC criteria were originally proposed.

Aged↗
PubMed1999

Clinical practice guidelines in unstable angina improve clinical outcomes by assuring early intensive medical treatment.

OBJECTIVES: To determine the influence of clinical practice guidelines on treatment patterns and clinical outcomes in unstable angina and the effectiveness of guideline reminders on implementing practice guidelines, two groups of medium and high risk patients with unstable angina were compared. BACKGROUND: New guidelines have been published by the Agency for Health Care Policy and Research (AHCPR) for evaluating and managing patients with unstable angina. The impact of these guidelines to improve the quality of care has never been tested. METHODS: Group 1 included 338 consecutive medium or high risk patients admitted before publication of the AHCPR guidelines, and group 2 consisted of 181 consecutive similar risk patients admitted after institution of the AHCPR guideline reminders at this institution. Dissemination of clinical practice guidelines was ensured by a grand rounds lecture and by posting guideline reminders on all group 2 patients' charts within 24 h of admission. RESULTS: The two groups were similar in terms of most baseline characteristics, including hypercholesterolemia, diabetes, hypertension, smoking history, baseline ST segment depression and previous coronary artery bypass graft surgery. Group 1 patients were older (68+/-13 vs. 63+/-16 years, p = 0.001) and more frequently had a previous myocardial infarction (39% vs. 22%, p = 0.001). Group 2 patients more frequently required intravenous nitroglycerin to control the index episode of chest pain (43% vs. 34%, p = 0.003). Group 2 patients more frequently received aspirin (96% vs. 88%, p = 0.009) during admission and underwent coronary angiography (71% vs. 58%, p = 0.006). More importantly, group 2 patients received oral beta-blockers (p = 0.008), aspirin and coronary angiography (p = 0.001) earlier than group 1 patients and experienced recurrent angina (29% vs. 54%) and myocardial infarction or death less frequently (3% vs. 9%, p = 0.028). CONCLUSIONS: In unstable angina, clinical practice guidelines were associated with greater use of aspirin and coronary angiography and greater use and earlier administration of beta-blockers. Variation in drug use over time was also reduced. Objective improvement in clinical outcome was also noted. Thus, practice guidelines improve the quality of care of patients with unstable angina.

Adrenergic beta-Antagonists↗
PubMed1999

Simultaneous intracoronary ultrasound and Doppler flow studies distinguish flow-mediated from receptor-mediated endothelial responses.

Abnormalities in vascular endothelial function, which occur early in atherosclerosis, may play an etiologic role in the development of the disease or represent a marker for the extent of atherosclerosis. Endothelial dysfunction, usually characterized by demonstration of decreased endothelium-dependent vasorelaxation, may be a sensitive and specific method to detect vascular disease in its earliest stages. In this context, separation of abnormalities in receptor-mediated and flow-mediated endothelium-dependent vasodilatory responses may allow for the most accurate characterization of endothelial dysfunction. In 35 patients undergoing routine annual cardiac catheterization after heart transplantation, changes in epicardial lumen area and coronary blood flow in response to intracoronary administration of adenosine, acetylcholine, and nitroglycerin were measured simultaneously using an intravascular ultrasound (IVUS) catheter positioned over a Doppler flow wire in the left anterior descending coronary artery. The combination of these techniques allowed for distinction between receptor-mediated and flow-mediated endothelium-dependent vascular responses. Peak flow with the endothelium-independent resistance vessel dilator adenosine occurred at 18+/-2 sec; the maximal lumen area response occurred later, at 43+/-11 sec (P < 0.001). Acetylcholine, an endothelium-dependent small- and large-vessel vasodilator, caused an immediate increase in both flow and lumen area, but a second peak of dilation was observed, and maximal area occurred 46 sec after maximal flow (54+/-14 vs. 100+/-26 sec, P < 0.001). Simultaneous IVUS and Doppler flow measurements after infusion of vasoactive agents allows for distinction between and evaluation of the relative contribution of agonist-mediated and flow-mediated responses, which may offer important and unique insights into coronary endothelial function.

Acetylcholine↗
PubMed1999

Unstable angina and non-Q wave myocardial infarction: does the clinical diagnosis have therapeutic implications?

OBJECTIVES: The goal of this review is to reevaluate the unstable coronary syndromes in the setting of new therapies and biochemical markers. BACKGROUND: Patients with acute coronary syndromes comprise a large subset of many cardiology practices. Patients with unstable angina (UA) and non-Q wave myocardial infarction (NQMI) may sustain a small amount of myocardial loss but have significant amounts of viable, yet ischemic, myocardium, placing them at high risk for future cardiac events. In the past, enzyme differentiation of NQMI from UA was considered important to assess prognosis and direct therapy. METHODS: Manuscripts published in peer-reviewed journals over the past three decades were reviewed and selected for this review. Recent abstracts were also considered and cited where appropriate. RESULTS: In the late 1990's, although UA and NQMI remain parts of a spectrum, it is apparent that the distinction between these two entities is no longer sufficient to identify high risk patients; rather, specific electrocardiographic changes, aspects of the clinical history, newer biochemical markers, and angiographic findings help to better distinguish higher risk individuals from a large patient population with unstable coronary syndromes and these factors usually determine therapy. CONCLUSIONS: Based on these results, it is likely that newer therapies such as glycoprotein IIb/IIIa receptor antagonists, low molecular weight heparins, and coronary stents will be directed toward these high risk patients.

Angina, Unstable↗
PubMed1998

Value of the American College of Cardiology/American Heart Association stenosis morphology classification for coronary interventions in the late 1990s.

The goal of this study was to reassess the accuracy of the American College of Cardiology/American Heart Association (ACC/AHA) stenosis morphology classification for predicting coronary intervention success and complications in the era of new devices. Previous studies performed in the early part of this decade for percutaneous transluminal coronary angioplasty in patients with multivessel coronary artery disease found that these criteria were predictive of success rates but not complication rates. Data for 957 consecutive coronary interventions in 1,404 lesions from June 1994 to October 1996 were prospectively classified according to ACC/AHA guidelines and entered into a database. Ninety-one and 9/10 of coronary interventions were successful, defined as <50% residual stenosis of each vessel attempted in the absence of major in-hospital complications, including Q-wave myocardial infarction, ventricular arrhythmia, need for emergency coronary artery bypass surgery, or death. Success rates did not differ between A (186 of 193, 96.3%), B1 (211 of 221, 95.5%), and B2 (676 of 711, 95.1%) lesions, but each was more successful than C (246 of 279, 88.2%) lesions (p <0.003, p < 0.004, and p = 0.0001, respectively). The class of lesion (A, B, or C) did not predict device (atherectomy, rotablator, and stent) use but specific morphologic characteristics of lesions within these classes were predictive of which device was used. Multiple regression analysis revealed that total occlusion and vessel tortuosity were predictive of procedure failure. Lesion type (A, B, or C) was not predictive of complications, but bifurcation lesions (p = 0.0045), presence of thrombus (p = 0.0001), inability to protect a major side branch (p = 0.0468), and degenerated vein graft lesions (p = 0.0283) were predictive. Thus, the ACC/AHA grading system is predictive of successful coronary intervention outcome, particularly of C-type characteristics, but not of complications or device success rate and selection. Although lesion type (A, B, or C) was not predictive of complications, specific lesion morphologies were predictive of adverse events and device use.

Aged↗
PubMed1998

Clinical predictors easily obtained at presentation predict resource utilization in unstable angina.

OBJECTIVE: To determine if a risk prediction model for patients with unstable angina would predict resource utilization. METHODS AND RESULTS: Four hundred sixty-five consecutive patients admitted for unstable angina to a tertiary care university-based medical center were prospectively evaluated from June 1, 1992, to June 30, 1995. The proportion of patients receiving coronary angiography, coronary angioplasty, and coronary artery bypass grafting were analyzed according to four risk groups on the basis of a previously published model: Group 1, <2% risk of major complication; Group 2, 2.1% to 5% risk; Group 3, 5.1 % to 15% risk; and Group 4, >15.1 % risk. Hospital length of stay and estimated cost of hospitalization based on DRG and specific payer ratio of cost-to-charge were also compared between groups. Multiple linear regression analysis was used to determine the influence of estimated risk and procedures on hospital costs. The four groups were well matched for gender, hypertension, tobacco history, and previous percutaneous transluminal coronary angioplasty and myocardial infarction. Group 4 had a higher incidence of previous coronary bypass grafting (35% vs 10%, p=0.001) and triple vessel or left main coronary artery disease compared with Group 1 (44% vs 13%, p=0.041). Group 4 patients were more likely to be admitted to the coronary care unit compared with Group 2 or Group 1 patients (80% vs Group 1: 51% [p= 0.001]; and vs Group 2: 53% [p=0.001]), more likely to receive heparin (87% vs 71%, p=0.007), and more likely to receive a beta-blocker or calcium channel blocker (89% vs 74%, p=0.008) than Group 1. Coronary angioplasty rates were similar for all groups, but Group 4 patients were more likely to receive coronary bypass grafting than Group 2 or Group 1 (27% vs Group 2: 12%, p=0.004 and vs Group 1: 8%, p=0.002). Hospital length of stay was highest in Group 4 and lowest for Group 1. Average hospital costs were significantly less in Group 3 than in Group 4, but higher than in Group 1. Multivariate analysis determined a dependency of costs on risk group with Group 2 having costs 31.4% (95% CI=9.8 to 57.2), Group 3 46.7% (24, 3 to 73.1), and Group 4 75% (46.9 to 110.7) higher than Group 1. The use of procedures also significantly increased costs, with PTCA-treated patients having a 44.9% (26.7 to 65.7) increase in costs compared with medically treated patients, and surgically treated patients having a 204.7% increase in costs. CONCLUSION: Resource utilization as assessed by the use of revascularization procedures, length of stay, and hospital costs are influenced by patient acuity estimated from a prediction model on the basis of estimated risk of cardiac complications. The model exerts independent influence on cost even after adjustment for various procedures. The use of revascularization procedures, especially coronary artery surgery, remains a large determinant of hospital cost.

Adult↗
PubMed1998

Discordant epicardial and microvascular endothelial responses in heart transplant recipients early after transplantation.

BACKGROUND: Cardiac allograft vasculopathy represents the leading cause of death in heart transplant recipients who survive more than 1 year. Functional endothelial abnormalities are sensitive measures of the early development of cardiac allograft vasculopathy, but the relative importance of large and small coronary vessel abnormalities has not been evaluated. The purpose of the study was to distinguish between large and small coronary endothelial dysfunction in patients early after heart transplantation and to test the hypothesis that microvascular endothelial responses can be preserved in the presence of epicardial endothelial dysfunction. METHODS: Changes in epicardial lumen area and coronary artery blood flow in response to intracoronary administration of adenosine, acetylcholine, and nitroglycerin were measured simultaneously by use of an intravascular ultrasound catheter positioned over a Doppler flow wire in the left anterior descending coronary artery. The combination of these techniques allowed distinction between large and small coronary vascular responses. In 19 patients studied early after transplantation, adenosine (16 and 32 microg), acetylcholine (5.4 and 54 microg), and nitroglycerin (200 microg) were infused, with continuous intravascular ultrasound imaging and Doppler velocity measurements. RESULTS: Acetylcholine induced paradoxical epicardial vasoconstriction in 12 of 19 patients (73% +/- 6% of baseline); vasodilation occurred in 7 (108% +/- 3%). In spite of this constriction, coronary artery flow increased in all 19 patients, to the same extent in patients with constriction and those with dilation (239 +/- 26 vs 193 +/- 20, p = 0.38). Adenosine and nitroglycerin increased area (107% +/- 1% and 112% +/- 3%) and flow (258% +/- 17% and 197% +/- 11%) in all patients. None of the area or flow responses correlated with the degree of intimal thickening. CONCLUSIONS: Acetylcholine increased coronary artery flow early after transplantation, indicating preserved microvascular responses in spite of epicardial vasoconstriction. Simultaneous measurement of area and velocity responses, by permitting evaluation of the relative contribution of epicardial and microvascular vessels, may offer unique insights into coronary endothelial function.

Acetylcholine↗
PubMed1997

Comparison of heparin therapy for < or = 48 hours to > 48 hours in unstable angina pectoris.

Of 450 consecutive patients with unstable angina admitted to a tertiary care, university-based medical center over a 24-month period, 334 were administered heparin and aspirin for some length of time. Two groups of 98 patients matched for acuity and gender at baseline were treated with either < or = 48 hours (group 1) or > 48 hours (group 2) of heparin. The acuity model used in this study incorporates 6 factors: age, recent myocardial infarction, treatment with intravenous nitroglycerin, previous therapy with beta blockers or calcium antagonists, baseline ST depression, and diabetes. Despite similar risks and overall clinical outcome, group 2 had significantly more myocardial infarction or death after 48 hours than group 1 (p = 0.01). In part, this was due to a delay in the performance of coronary angiography (2.8 +/- 1.4 vs 3.5 +/- 15 days, p = 0.01), coronary intervention (2.7 +/- 1.8 vs 5.1 +/- 2.3 days, p = 0.01), and bypass surgery (3.8 +/- 3.6 vs 7.0 +/- 5.6 days, p = 0.02). There was no difference between groups regarding the success of coronary intervention (90% vs 88%, p = NS). Heparin duration was influenced by the finding of intracoronary thrombus or ulceration on angiography before revascularization, as each finding was seen more often in group 2 (thrombus, 12% vs 24%; ulceration, 38% vs 60%). These results suggest that the optimal duration of heparin therapy is up to 48 hours after admission in unstable angina; a longer time period is associated with increased adverse consequences.

Aged↗