The use of antiplatelet agents in acute cardiac care.

Antiplatelet therapy with aspirin has long been established as standard therapy in the management of conditions such as ST-elevation myocardial infarction and the acute coronary syndromes (unstable angina and non-ST-elevation myocardial infarction). Recently, several more potent platelet inhibitors have been developed and tested in randomized clinical trials. This article reviews the current state of the art of antiplatelet therapy.

The intermediate CCU admission: a preliminary study.

In the current health care era, increasing emphasis is being placed on cost reduction. Admitting only high-risk patients to coronary care units (CCU) may reduce hospital costs and charges without adverse clinical outcomes. Recently, guidelines published by the Agency for Healthcare Policy and Research (AHCPR) on suggest that intermediate-risk patients be admitted to an intermediate CCU (ICCU), but the safety and appropriateness of this approach has not been prospectively evaluated. The authors hypothesized that admitting intermediate-risk patients with to an ICCU would be cheaper than admitting to a CCU with comparable safety supporting AHCPR guidelines. To evaluate this, a retrospective cohort study was conducted. Two hundred forty-three intermediate-risk patients consecutively admitted to the CCU (n = 134) and admitted to the ICCU (n = 109) between June 1, 1992 and April 1, 1994 were compared using AHCPR definitions of intermediate risk and a previously published risk prediction model to exclude both very low- and high-risk patients. Extensive demographic, clinical, and diagnostic testing, and treatment, procedural, and outcome data were collected by a trained nurse data collector at the time of admission. Fifty-nine percent of all study patients had at least two coronary risk factors. Twenty-one percent had diabetes. Ninety-eight percent had at least one AHCPR intermediate risk factor for cardiac complications. The two groups (CCU versus ICCU) were quite similar in baseline characteristics: men (56 versus 55%), age (57 +/- 17 versus 60 +/- 17 years), diabetes (22 versus 20%), previous myocardial infarction (30 versus 36%), previous coronary artery surgery (21 versus 21%), and rest pain (78 versus 66%). The use of coronary angiography (44 versus 52%), angioplasty (24 versus 21%), and coronary artery surgery (13 versus 11%) were also similar. The incidence of myocardial infarction or death was similar (3 versus 5%), and length of stay was also similar between groups (6.7 +/- 4.2 versus 6.5 +/- 4.1 days), but cost was less for patients admitted to the ICCU ($13,481 +/- 9,450 versus $10,619 +/- 8,732, P < 0.015). These preliminary data suggest intermediate-risk patients, as identified by AHCPR guidelines, can be treated in an ICCU at lower cost than in a CCU, with reasonable safety. A small incidence of myocardial infarction in ICCU-admitted patients occurs, requiring availability of cardiac resuscitation and continued monitoring of electrocardiographic and enzymatic abnormalities. Admission to ICCU poses no barrier to recommended patient evaluation and management.

Validated risk stratification model accurately predicts low risk in patients with unstable angina.

BACKGROUND: In the mid 1990s, two unstable angina risk prediction models were proposed but neither has been validated on separate population or compared. OBJECTIVES: The purpose of this study was to compare patient outcome among high, medium and low risk unstable angina patients defined by the Agency for Health Care Policy and Research (AHCPR) guideline to similar risk groups defined by a validated model from our institution (RUSH). METHODS: Four hundred sixteen patients consecutively admitted to the hospital with unstable angina between January 1, 1995, and December 31, 1997, were prospectively evaluated for risk factors. The presence of major adverse events such as myocardial infarction (MI), death and heart failure was assessed for each patient by chart review. RESULTS: The composite end point of heart failure, MI or death occurred in 3% and 5% of the RUSH and AHCPR low risk categories, respectively, and in 8% and 10% of AHCPR and RUSH high risk categories, respectively. Recurrent ischemic events were best predicted by the RUSH model (high: 24% vs. medium: 12% and low: 10%, p = 0.029), but not by the AHCPR model (high: 14% vs. medium: 13% and low: 9%, p = 0.876). The RUSH model identified five times more low risk patients than the AHCPR model. CONCLUSIONS: Both models identify patients with low and high event rates of MI, death or heart failure. However, the RUSH model allowed for five times more patients to be candidates for outpatient evaluation (low risk) with a similar observed event rate to the AHCPR model; also, the RUSH model more successfully predicted ischemic complications. We conclude that the RUSH model can be used clinically to identify patients for early noninvasive evaluation, thereby improving cost effectiveness of care.

Utilization of coronary angiography and revascularization after acute myocardial infarction in men and women risk stratified by the American College of Cardiology/American Heart Association guidelines.

OBJECTIVES: We sought to determine whether men and women are equally likely to receive coronary angiography and revascularization after acute myocardial infarction (AMI) when they are risk stratified according to American College of Cardiology/American Heart Association (ACC/AHA) practice guidelines for post-MI care. BACKGROUND: Several previous studies have suggested that women may undergo angiography and revascularization procedures less frequently than men. METHODS: In 439 consecutive patients admitted to a public hospital with AMI, rates of coronary angiography and revascularization were compared in men and women categorized, according to ACC/AHA practice guidelines, as having strong (class I or IIa) or weaker (class IIb) indications for angiography. RESULTS: Women were older and more likely to be diabetic or hypertensive, but men and women were equally likely to meet class I/IIa criteria for post-MI angiography (both 51%). Angiography rates were nearly identical in men and women overall (63% vs. 64%), as well as in patients in class I/IIa (80% vs. 82%) and class IIb (46% vs. 46%) (all p > 0.80, with >80% power to detect important differences); the only multivariate predictors of post-MI angiography were age and ACC/AHA class. Significant coronary artery disease was equally prevalent in men and women undergoing angiography, and men and women were equally likely to undergo revascularization, whether they were in class I/IIa (both 55%, p = 0.90) or class IIb (59% vs. 58%, p = 0.88). No significant differences in mortality were noted between men and women. CONCLUSIONS: Despite being older and having more risk factors than men, women were equally likely to undergo coronary angiography and revascularization procedures after AMI, and they had in-hospital clinical outcomes that were at least as favorable.

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.

The incidence of major morbidity in critically ill patients managed with pulmonary artery catheters: a meta-analysis.

INTRODUCTION: The impact of pulmonary artery (PA) catheters on patient outcome has been questioned and their usage has become controversial. Meta-analysis on mortality has shown a trend for improved survival with PA catheter-guided therapy. We now perform a meta-analysis on morbidity from PA catheters in the published literature. METHODS: We did a search of the medical database (Medline) from 1970 through 1996, using the headings "pulmonary artery catheterization," "Swan-Ganz catheterization" and "right heart catheterization," and restricting the results to "effectiveness" and "usefulness." We also consulted with other experts regarding published randomized controlled trials (RCTs). This yielded 16 RCTs addressing the question of effectiveness of PA catheter-guided treatment. Of these, 12 were found to include data on morbidity. Major morbidity, defined as organ failures as per the American College of Chest Physicians/Society of Critical Care Medicine Consensus Conference criteria, from these trials was entered into a formal meta-analysis. RESULTS: A total of 1,610 patients from the 12 trials were analyzed. Morbidity events were observed in 62.77% of the PA catheter treatment group, and in 74.34% of the control group. A relative risk ratio of 0.78074 was obtained, with a 95% confidence interval of 0.6459-0.94374 and a corresponding p of .0168, a lower morbidity in the PA catheter treatment group. Those with PA catheter-guided treatment had a mean protective effect of 21.9% for risk of morbidity. Other important covariates such as acuity of illness, quality score of trials, year of publication, type of PA catheter-guided treatment used (PA catheter vs. no PA catheter, or PA catheter vs. PA catheter for supranormal hemodynamic values), and surgical or mixed patient population, all increased variability and were not statistically significant predictors for risk ratio of morbidity. CONCLUSIONS: Meta-analysis of RCTs included in this study shows that there is a statistically significant reduction in morbidity using PA catheter-guided strategies.

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.

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.

Unstable angina: pathogenetic mechanisms, coronary angiographic observations, risk stratification, and therapeutic implications.

The acute coronary syndromes, which include unstable angina (UA) and non-Q-wave (NQMI) and Q wave myocardial infarction (MI), constitute the most frequent acute clinical manifestations of coronary artery disease. Unstable angina and NQMI are clinically distinct syndromes of acute ischemia, implying the presence of further jeopardized myocardium. Regardless of whether a small degree of myocardial necrosis has occurred (as measured by the release of creatine kinase and MB isoenzyme in the blood), both diagnoses have in common the likely potential for recurrent angina and infarction. Hence, these entities uniquely suggest the possibility of further hazard rather than the necessity of accepting and managing the consequences of loss of function. The appropriate diagnostic and therapeutic approaches are governed by these characteristics. Only during the last 15 years has coronary angiography been routinely performed in patients with acutely unstable coronary syndromes. This has led to the subsequent development of new insights into pathogenesis. In addition, new treatment modalities are now available.

The use of APACHE II scores to select candidates for left ventricular assist device placement. Acute Physiology and Chronic Health Evaluation.

BACKGROUND: The growth in left ventricular assist device (LVAD) use has been hampered by high morbidity and mortality rates and cost. The purpose of this study was to help improve patient selection for LVAD placement by determining whether the Acute Physiology and Chronic Health Evaluation II (APACHE II) scoring system, a multiparameter, physiology-based predictor of outcome, could be used to predict outcome after LVAD placement and thus help determine optimum timing of LVAD placement. METHODS: This was a retrospective analysis of a prospective cohort observational study consisting of 2 groups: (1) 50 patients with severe heart failure who did not receive LVAD placement after initial evaluation and (2) 31 patients who did receive LVAD placement. Patients included in the study were in severe heart failure on the basis of 3 of the following: lung crackles, S3, peripheral edema, ejection fraction < 0.30, systolic blood pressure < 80 mm Hg, progressive prerenal azotemia, altered level of consciousness, gastrointestinal ischemia or congestion, or persistent although reversible pulmonary hypertension in spite of maximal medical therapy, including intravenous inotropes. The decision for LVAD placement was at the discretion of the attending physician. RESULTS: Both LVAD- and non-LVAD-treated patients were similar in cause of heart failure, APACHE II scores, and other baseline laboratory parameters. Survival time with a log-logistic model was better for LVAD-treated patients, p=.0266. Although Kaplan Meier analysis showed a trend toward better survival rates in the LVAD-treated patient, the Cox proportional hazards revealed that LVAD-treated patients had better survival (relative risk ratio, 95% confidence interval=0.305, 0.110 to 0.892; p=.0219) after adjustment for APACHE II score. Each unit increase in APACHE II independently predicted death (relative risk ratios, 95% confidence interval=1.139, 1.055 to 1.231; p=.0009). Patients with medium APACHE II (11 to 20) scores in particular benefitted from LVAD treatment. CONCLUSION: LVAD placement for severe heart failure (not restricted to cardiogenic shock) improves survival. APACHE II can aid in deciding the timing of LVAD placement in patients with heart failure who may not have attained conventional hemodynamic criteria for LVAD placement. Patients who had APACHE II scores between 11 and 20 derived the greatest benefit from LVAD placement.

Improved risk stratification in unstable angina: identification of patients at low risk for in-hospital cardiac events by admission echocardiography.

BACKGROUND: Current protocols for risk stratification of patients with acute chest pain syndromes rely on clinical parameters and are oriented toward identification of patients at high risk for adverse cardiac events; however, this paradigm for risk stratification does not adequately address the observation that adverse cardiac events are relatively uncommon in this population. In an era of cost containment, consideration also should be given to identification of patients at low risk for adverse cardiac events, who may be safely discharged without expensive inpatient hospitalization. HYPOTHESIS: The purpose of this study was to develop echocardiographic predictors that identify unstable angina patients at low risk for adverse cardiac events and that discriminate between low- and high-risk patients. METHODS: The predictive accuracy of retrospectively determined echocardiographic predictors were compared in a population-based sample of 66 consecutive unstable angina patients undergoing echocardiography within 24 h of admission. RESULTS: Echocardiographic predictors of adverse events included wall motion score index > or = 0.2, ejection fraction < or = 40%, and mitral regurgitation severity > 2. One or more echocardiographic predictors of adverse events were present in 32 patients (48%). A composite echocardiographic predictor of adverse events was specific, had a high positive predictive value for the identification of high-risk patients, and discriminated between unstable angina patients at high and low risk for adverse cardiac events. CONCLUSION: Echocardiographic predictors of adverse events are specific and discriminate between unstable angina patients at high and low risk for adverse cardiac events.

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.

Understanding articles describing clinical prediction tools. Evidence Based Medicine in Critical Care Group.

OBJECTIVES: Clinical prediction rules and models are developed by applying statistical techniques to find combinations of predictors that categorize a heterogeneous group of patients into subgroups of risk. Our goal is to teach clinicians how to evaluate the validity, results, and applicability of articles describing clinical prediction tools. CLINICAL EXAMPLE: An article describing a rule to predict the need for intensive care unit care admission in patients presenting to the emergency room with chest pain. RECOMMENDATIONS: Valid clinical prediction tools are developed by completely following up a representative group of patients, by evaluating all potential predictors and testing the independent contribution of each predictor variable, and by ensuring that the outcomes were independent of the predictors. To evaluate the results of an article describing a clinical prediction tool, clinicians need to know what the prediction tool is, how well it categorizes patients into different levels of risk, and what the confidence intervals are around the risk estimates. Valid prediction tools are not applicable in every patient population. Before patient care application, the clinician should ensure that the tool maintains its prediction power in a new sample of patients, that the patients are similar to patients used to test the tool, and that the tool has been shown to improve clinical decision-making. CONCLUSIONS: There has been an increase in the development and validation of clinical prediction rules and models. It is important to evaluate the validity and reliability of these prediction tools before application.

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.