Ability of troponins to predict adverse outcomes in patients with renal insufficiency and suspected acute coronary syndromes: a case-matched study.

OBJECTIVES: The purpose of this study was to investigate the utility of cardiac troponin T and troponin I for predicting outcomes in patients presenting with suspected acute coronary syndromes and renal insufficiency relative to that observed in similar patients without renal disease. BACKGROUND: Cardiac troponin T and troponin I have shown promise as tools for risk stratification of patients with acute coronary syndromes. However, there is uncertainty regarding their cardiac specificity and utility in patients with renal disease. METHODS: We measured troponin T, troponin I and creatine kinase MB in 51 patients presenting with suspected acute coronary syndromes and renal insufficiency and in 102 patients without evidence of renal disease matched for the same peak troponin T or I value, selected from a larger patient cohort. Blood samples were obtained at presentation to an emergency room 4 hours, 8 hours and 16 hours later. The ability of biochemical markers to predict adverse outcomes in both groups including infarction, recurrent ischemia, bypass surgery, heart failure, stroke, death or positive angiography/angioplasty during hospitalization and at six months was assessed by receiver-operator curve analysis. The performance of both troponins was compared between groups. RESULTS: Thirty-five percent of patients in the renal group and 45% of patients in the nonrenal group experienced an adverse initial outcome; over 50% of patients in all groups had experienced an adverse outcome by 6 months, but these differences were not significant. The area under the curve (AUC) for the ROC curve for troponin T as predictor of initial outcomes was significantly lower in the renal group than in the nonrenal group: 0.56+/-0.07 and 0.75+/-0.07, respectively. The area under the curve was also significantly lower in the renal group compared with the nonrenal group for troponin T as predictor of six month outcomes: 0.59+/-0.07 and 0.74+/-0.07, respectively. The area under the curve was also significantly lower in the renal group compared to the nonrenal group for troponin I as predictor of both initial and six month outcomes: 0.54+/-0.06 vs. 0.71+/-0.07 and 0.53+/- 0.06 vs. 0.65+/-0.07, respectively. The sensitivity of troponin T for both initial and six month adverse outcomes was significantly lower in the renal group than in the nonrenal group at a similar level of specificity (0.87): 0.29 vs. 0.60 and 0.45 vs. 0.56, respectively. Troponin I also exhibited similar differences in sensitivity in the renal group (0.29 vs. 0.50 and 0.33 vs. 0.40, respectively). CONCLUSIONS: The ability of cardiac troponin T and troponin I to predict risk for subsequent adverse outcomes in patients presenting with suspected acute coronary syndromes is reduced in the presence of renal insufficiency.

Comparison of troponin T versus creatine kinase-MB in suspected acute coronary syndromes.

Limitations of creatine kinase-MB (CK-MB) have led to alternative biochemical markers, including troponin T (TnT), to detect myocardial necrosis. Limited data are available regarding the predictive value of this new marker in patients with chest pain of uncertain etiology. Therefore, we prospectively compared CK-MB and TnT in a broad population with suspected acute coronary syndromes, including those admitted to a short-stay chest pain unit. CK-MB, quantitative TnT levels, and a rapid bedside assay were performed at 0, 4, 8, and 16 hours. Adverse events, including infarction, recurrent ischemia, coronary surgery, need for catheterization and/or intervention, stroke, congestive heart failure, or death, were identified by chart review and by follow-up phone call at 6 months. Of 707 patients, 104 were excluded for creatinine >2 mg/dl or incomplete data, leaving a total cohort of 603 patients. Coronary Care Unit admissions were 18%, intermediate care admissions were 14%, telemetry admissions is 21%, and admissions to 24-hour short-stay area were 47%. TnT (at 0.1 ng/ml) and CK-MB were positive in a similar proportion of patients (20.4% and 19.7%, respectively); however, the patients identified by TnT and CK-MB were not identical. In-hospital adverse events occurred in 37.1% with no differences in positive predictive value for the markers (p = NS). If CK-MB and TnT were negative, the early adverse event rate was 27%. No cardiac marker was positive by 16 hours in 54.9% of patients with an adverse event. Six-month follow-up was obtained in 576 of the 603 patients (95.5%). One hundred fifty-five late adverse events occurred in 134 patients (23.3%) at an average of 3.3+/-2.5 months after discharge. If both markers were negative, the late event rate was 20.2% and did not increase in patients with positive CK-MB or TnT >0.2 ng/ml. However, the late event rate was substantially higher (52.9%) in those with intermediate TnT levels of 0.1 to 0.2 ng/ml (p = 0.002). Thus, TnT is a suitable alternative to CK-MB in patients with suspected acute coronary syndromes. The rapid bedside assay is comparable to quantitative TnT and may enable early diagnosis and triage. A negative cardiac marker value (TnT or CK-MB) does not necessarily confer a low risk of complication in patients presenting with acute chest pain to an emergency department.

Normal CK, elevated MB predicts complications in acute coronary syndromes.

The implications of an elevated Creatine kinase (CK)-MB isoenzyme (MB) in suspected acute coronary syndromes, with a normal total CK, is not well established. Despite many guidelines on managing patients with acute coronary ischemia, none indicates strategies for patients with elevated MB and with a normal CK. The outcome consequence of this result is not firmly established. Our objective was to prospectively evaluate outcomes in patients with suspected acute coronary syndromes, normal initial total CK, and increased MB. All Emergency Department patients with suspected acute coronary syndromes and creatinine < 2.0 mg/dL were eligible for study entry. Serial CK and MB fractions were measured on arrival in the Emergency Department, then 8 and 16 h postpresentation. A composite outcome of death, Q-wave myocardial infarction, or revascularization was defined at the index visit and 6 months later. Outcomes were determined by blinded record review and by telephone contact. In the 698 patients entered, the acute composite outcome rate was 25% (175) and 6.3% (44) at 6 months. Acute and 6 month adverse outcome rates were statistically the same for all patients with an elevated MB fraction, regardless of the total CK level. An elevated MB conferred a higher event rate than did a normal MB. We conclude that the adverse event rate for patients with suspected acute coronary syndromes and an elevated MB is the same whether or not the total CK is elevated. These patients should be considered as having had an acute coronary syndrome.

Percutaneous cardiopulmonary bypass support: a new approach to high-risk angioplasty.

Percutaneous cardiopulmonary bypass is a new technique for supporting systemic blood flow during high-risk coronary angioplasty procedures. This mechanical alternative, unlike traditional methods, is not limited by dependency on adequate left ventricular stroke volume. Percutaneous cardiopulmonary bypass support offers new and demanding challenges in the care of this high-risk group of patients.

Dual-chamber pacing.

Dual-chamber pacing has been available since the early 1980s, yet it is a topic with which critical care nurses consistently have difficulty. New advances in pacemaker technology have built on the principles inherent in dual-chamber pacing, making it imperative that practitioners have a basic understanding of dual-chamber pacemaker function. With dwindling clinical resources, the responsibility of the bedside nurse to evaluate appropriate pacemaker function and identify the patient's response to pacemaker therapy has increased.

Thrombolytic therapy versus primary angioplasty in the treatment of acute myocardial infarction.

The quest to identify the acute interventional approach that will achieve the lowest mortality rate with the fewest adverse events has led to a continued controversy surrounding the relative merits of thrombolytic therapy compared with primary angioplasty in the setting of acute myocardial infarction. This article summarizes the benefits and limitations of each reperfusion strategy and highlights adjunctive therapies that will enhance either treatment strategy.

The vulnerable coronary plaque.

Vulnerable coronary plaques are asymptomatic atherosclerotic lesions with the tendency to rupture. Plaque rupture is the initiating event in most acute coronary syndromes including sudden cardiac death, acute myocardial infarction, and unstable angina. Vulnerable plaques are commonly found in coronary arteries at autopsy but are virtually undetectable by standard diagnostic techniques such as stress testing and coronary angiography. Using new imaging techniques, in particular intravascular ultrasound and magnetic resonance imaging (MRI), scientists are now able to identify these plaques in vivo. A better understanding of the pathophysiology of plaque vulnerability and rupture will eventually lead to the therapeutic goal of plaque stabilization in the prevention of acute coronary syndromes. This article reviews the role of plaque vulnerability in coronary artery disease. The anatomy and pathophysiology of vulnerable plaques as well as diagnostic and therapeutic implication will be described.

The Maze procedure: a new treatment for atrial fibrillation.

Atrial fibrillation is a dysrhythmia with lethal complications afflicting thousands of people each year. Unfortunately, atrial fibrillation is frequently resistant to medical therapy and other nonsurgical treatments, such as cardioversion and catheter ablation. Past surgical procedures to correct the dysrhythmia have also proved ineffective. A surgical procedure has been developed in which multiple incisions are made in the atrium, creating an electrical maze. The maze procedure restores atrioventricular synchrony while simultaneously preventing macroreentry within the atria. It thereby eliminates the clinical sequelae often associated with atrial fibrillation and improves the quality of life for those patients refractory to current methods of treatment.

Prediction of short- and long-term outcomes by troponin T levels in low-risk patients evaluated for acute coronary syndromes.

STUDY OBJECTIVE: Recent reports suggest a short series of cardiac troponin (cTnT) testing effectively identifies patients at risk for cardiac events. However, there are few studies validating this strategy. The purpose of this study was to determine the ability of cTnT levels to predict short- and long-term outcomes in low-risk patients with suspected acute coronary syndromes. METHODS: This prospective longitudinal study was conducted in a 20-bed emergency department observation unit. Patients at low risk for acute coronary ischemia, with a normal creatine kinase-isoenzyme subunit MB (CKMB) index, were admitted to an observation unit for chest pain evaluation. Serum cTnT levels were measured at baseline and at 4, 8, and 16 hours after admission. The main outcome measures were adverse cardiac events (death, acute myocardial infarction, unstable angina, revascularization) during the index visit and within 6 months after discharge. Using manufacturer's recommendations, the cTnT level was considered abnormal if it exceeded 0.2 microg/L. RESULTS: Two hundred sixty-six patients were evaluated. Twenty-one (7.9%) had an adverse event during their index hospitalization. Troponin testing identified only 2 (9.5%) of these patients. Twenty (7.5%) had a cardiac event within 6 months; none were identified by cTnT testing. The sensitivity and specificity were 9.5% and 99.2%, respectively, at the index visit, and 0% and 98.4% at 6 months. The positive and negative predictive values were 50% and 93%, respectively, at the index visit; and 0% and 92% at 6 months. CONCLUSION: Determination of troponin T levels has a low sensitivity and high specificity for predicting outcomes in low-risk patients evaluated for suspected acute coronary syndromes. This study does not support a strategy of relying solely on troponin testing for disposition decisions.