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L W Klein

Publications and source records attributed to L W Klein.

At least 37 records · Page 2Linked to original sources
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↗
PubMed1997

Does low individual operator coronary interventional procedural volume correlate with worse institutional procedural outcome?

OBJECTIVES: To assess the relation between individual operator coronary interventional volume and incidence of complications, the in-hospital outcome at a single, moderate volume urban academic center was prospectively collected over a 3-year period. BACKGROUND: A minimum of 75 coronary interventions/operator per year may be required in the future to obtain formal certification. However, few data exist regarding individual operator volumes and procedural outcome. METHODS: Between January 1993 and December 1995, 1,389 consecutive procedures were performed or supervised by nine geographic full-time operators: 171 (12.3%) utilized various devices, and 350 (25.2%) involved multivessel coronary intervention. Left ventricular ejection fraction was 59 +/- 15% (mean +/- SD), and there were 1.7 +/- 0.7 vessels diseased (with > or = 70% stenosis). Clinical indications included stable angina in 22.5% of cases, unstable angina in 31.9%, acute myocardial infarction (MI) in 2.9%, post MI in 20.6%, shock or acute heart failure in 3.0% and restenosis in 19.1%. In the last consecutive 857 lesions in 655 cases, 20.7% type A, 55.5% type B and 23.8% type C lesions were categorized before coronary intervention. RESULTS: Average yearly operator volume ranged from 26 to 83 cases (mean 51 +/- 26). Each operator has performed a total of 590 +/- 268 coronary interventions, with 10.0 +/- 4.3 years of coronary interventional experience. The mean angioplasty volume rating for the nine operators was 180 +/- 37 (> 170 considered adequate). The in-hospital major complication rate was 1.4% (95% confidence interval 0.7% to 1.893%) for all coronary interventions, including death in 3 patients, bypass surgery in 13, arrhythmia in 3 and Q wave MI in 2. To ascertain how these outcomes compared with standard measures of coronary interventional outcome, four previously published registries were reanalyzed in a similar manner. The rate of complications in the present study was found to be significantly lower than that of the 1992-1993 Society for Cardiac Angiography and Intervention registry (1.9%, n = 19,594, p < 0.05 [excludes ventricular arrhythmias]), the 1994 American College of Cardiology database (3.9%, n = 38,963, p = 0.001), the Mid-America Heart Institute outcome in 1988 (2.3%, n = 5,413, p = 0.02) and the 1985-1986 National Heart, Lung, and Blood Institute Registry (7.2%, n = 1,801, p = 0.001). Odds ratios and 95% confidence intervals showed the outcome in the current study to be at least comparable to the standard registries. CONCLUSIONS: Despite individual operator volumes below those currently being considered for credentialing, the overall institutional outcome was excellent in a diverse and complex patient population.

Academic Medical Centers↗
PubMed1996

When we "act" on ACT levels: activated clotting time measurements to guide heparin administration during and after interventional procedures.

The establishment and monitoring of anticoagulation before, during, and after interventional and invasive procedures are crucial responsibilities. However, few prospective studies exist to rationally guide us in how and when to "act" in response to ACT values in specific clinical situations. Definitive studies to reach a uniform and safe ++approach are needed. The articles published in this issue of Catheterization and Cardiovascular Diagnosis represent an important step in understanding the role and value of ACT levels.

Angioplasty, Balloon, Coronary↗
PubMed1995

Utility of various clinical, noninvasive, and invasive procedures for determining the causes of recurrence of myocardial ischemia or infarction > or = 1 year after percutaneous transluminal coronary angioplasty.

In patients with recurrent symptoms > or = 1 year after successful percutaneous transluminal coronary angioplasty (PTCA), the decision of whether to proceed directly with coronary angiography or to evaluate the patient noninvasively can be difficult. To determine which demographic, historical, clinical, and laboratory factors are useful in helping to make this decision, 76 consecutive patients who presented > 1 year (768 +/- 309 days) after successful PTCA with resolution of symptoms were studied. The initial PTCA successfully treated all stenoses (except chronically occluded vessels) in all major vessels and segments. The patient group was predominantly men (68%), with a mean age of 64 +/- 10 years. A prior myocardial infarction was present in 39 patients (51%), and there was a mean of 2.8 risk factors per patient. In patients who presented with recurrent symptoms, the Canadian Cardiovascular Society functional class was 2.0 +/- 0.9; 2 patients presented with acute infarctions, 57 were admitted to the hospital with unstable angina, and 17 had stable angina. New electrocardiographic changes at rest were found in 19 of 74 patients (26%) with recurrent angina. A thallium stress test was performed in 40 patients (53%), with a sensitivity of 77% and a specificity of 36% for the presence of a significant stenosis. No nonangiographic variable was predictive of angiographic findings. At angiography, the number of coronary arteries with > or = 50% diameter narrowing was 1.4 +/- 1.0. Forty-two patients had stenosis at a new site, 7 had restenosis, and 27 had no new stenoses.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1995

Risk stratification in unstable angina. Prospective validation of the Braunwald classification.

OBJECTIVES: To validate the Braunwald classification of unstable angina as a predictor of in-hospital cardiac complications; to determine which factors of the Braunwald classification contributed significantly to this prediction; and to devise a method of combining these predictive factors into an overall odds ratio for complications. DESIGN: A validation cohort of consecutive patients followed prospectively for in-hospital cardiac complications including myocardial infarction and death. SETTING: A community-based academic medical center. PATIENTS: A total of 393 patients admitted consecutively to the coronary care and intermediate care units with unstable angina. MAIN OUTCOME MEASURES: Major cardiac complications including death, myocardial infarction, congestive heart failure, cardiogenic shock, and severe ventricular dysrhythmias. RESULTS: Multiple logistic regression analysis identified four clinical factors used in the Braunwald classification that predicted the in-hospital occurrence of major cardiac complications: (1) myocardial infarction within less than 14 days (odds ratio [OR], 5.72; 95% confidence interval [CI], 1.92 to 16.97); (2) need for intravenous nitroglycerin (OR, 2.33; 95% CI, 1.31 to 4.17); (3) lack of beta-blocker or calcium channel blocker prior to admission (OR, 3.83; 95% CI, 1.55 to 9.42); and (4) baseline ST depression (OR, 2.81; 95% CI, 1.45 to 5.47). Two other clinical factors, diabetes and age, were also significant predictors. Validation of this model using parametric and nonparametric bootstrap techniques revealed excellent agreement between the CIs for adjusted ORs derived from the multiple logistic regression and those derived from the bootstrap. CONCLUSIONS: The classification of unstable angina proposed by Braunwald includes four factors that predict risk of major in-hospital cardiac complications. Specific factors used in this classification can be combined with diabetes and age to better stratify risk of major cardiac complications in this disorder using a simpler model.

Age Factors↗
PubMed1995

Six month outcome and determinants of adverse clinical events after successful excimer laser coronary angioplasty. ELCA A.I.S. Multicenter Registry.

OBJECTIVE: To describe the six month outcome and predictors of adverse clinical events following successful excimer laser coronary angioplasty (ELCA). DESIGN: Retrospective analysis of comprehensive data collected at time of initial procedure and during planned follow-up intervals. SETTING: There were 35 participating institutions throughout the United States. PATIENTS: The study population was comprised of 3,069 patients who had successful ELCA and completed follow-up at 6 months, representing 91% of eligible cases. Forty percent had prior balloon angioplasty and 34% had prior bypass surgery. MEASUREMENTS: Patient symptomatology was assessed by Canadian Cardiovascular Society functional (CCSF) class. Interim adverse clinical events [death, Q wave myocardial infarction (QMI), repeat intervention, bypass surgery, and a composite end-point] were tracked. Twenty-six pre-ELCA clinical, angiographic and procedural variables were evaluated to assess their ability to predict outcome. RESULTS: At 6 months, there was 2.8% mortality, 2.5% incidence of QMI, and 28.7% required either repeat intervention or bypass surgery. Overall, 69.2% of patients had no adverse event. In this cohort, the pre-ELCA CCSF class grade was 2.7 +/- 1.2, but at 6 months, it was 0.7 +/- 1.1 (p < 0.001). The multivariate predictors of the composite end point were gender, stenosis location, and rest and unstable angina. CONCLUSIONS: There is an excellent 6 month outcome after successful ELCA in this selected population with complex coronary artery disease. The majority of patients without interim events enjoy significant alleviation of symptoms. The predictors of adverse events are clinical rather than angiographic.

Angioplasty, Balloon, Laser-Assisted↗
PubMed1994

Morphological and quantitative angiographic analyses of progression of coronary stenoses. A comparison of Q-wave and non-Q-wave myocardial infarction.

BACKGROUND: The purpose of this study was to determine differences in coronary stenosis severity and morphology and time course of progression between Q-wave and non-Q-wave myocardial infarction (MI). METHODS AND RESULTS: We studied 32 patients with new Q-wave MI and 38 patients with new non-Q-wave MI who underwent coronary angiography both before and after MI without interval revascularization procedures. Quantitative coronary angiographic analysis was performed by the caliper method, and morphological analysis of coronary angiograms was obtained before and soon after acute MI. Before infarction, the stenosis severity at the site of future MI was worse in Q-wave (44 +/- 25%) versus non-Q-wave (23 +/- 35%) MI patients (P < .01). Eccentric and irregular plaques were more common in Q-wave MI patients (18 of 32, 56%, versus 5 of 38, 13%; P < .001). Non-Q-wave MI patients were more frequently found to have significant collaterals after MI compared with Q-wave MI patients (18 of 38, 47%, versus 1 of 32, 3%; P < .001) despite no difference in post-MI stenosis severity. Analysis according to time interval after pre-MI angiography showed that 9 of 11 patients (82%) with Q-wave MI < 18 months later had a stenosis of > or = 50% versus 7 of 21 (33%) with an interval > 18 months (P < .05). By comparison, non-Q-wave MI patients tended to fall into two categories regardless of time of progression: Either minimal or no stenosis (< 20%) or else a severe stenosis (> 70%) was typically present. CONCLUSIONS: The atheromatous plaque substrate is different in Q-wave and non-Q-wave MI. Non-Q-wave MI occurs typically at a site shown by pre-MI angiography to involve either minimal luminal narrowing or a severe stenosis before MI, which is usually nonulcerated. By comparison, Q-wave MI follows a moderate stenosis in which the plaque is eccentric and ulcerated. Such differences culminate in differences in thrombus lability and collateral development and consequently in different clinical profiles.

Adult↗