Accelerated cardiac protocols in emergency laboratory medicine: four case studies.

Abstract

1. Wayne Gade, PhD MT(ASCP)[⇑][1] 1. is assistant Professor of Clinical Laboratory Science, University of Illinois at Springfield, Springfield IL 2. Charis Hainaut, CLS(NCA) 1. is a CLS in the Clinical Laboratory, Decatur Memorial Hospital, Decatur IL 3. Jean Gade, MS RN 1. is an Instructor in the Chemistry Department, Northern Kentucky University, Highland Heights, KY 1. Address for correspondence: Wayne Gade PhD MT(ASCP) Clinical Laboratory Science Program, HSB 314, University of Illinois at Springfield, Springfield, IL 62703-5407. (217) 206-7349. After reading the following articles, the reader will demonstrate his/her understanding of the material by achieving the following: 1. Describe the biochemistry of the BNP and the other natriuretic peptides. 2. Describe the major physiologic responses to the elevation of BNP levels. 3. Discuss the mechanism by which the binding of BNP to the target cell results in alteration of Na+ and water reabsorption. 4. Describe the formation of arterial plaque and the development of coronary artery disease and acute coronary syndromes (ACS). 5. Describe the physiological conditions that develop into CHF and cause the release of BNP. 6. Describe and interpret the diagnostic accuracy, sensitivity, specificity, and negative predictive values reported for rapid BNP assays. 7. Describe the trend toward “accelerated cardiac protocols,” including which markers are suggested, and the suggested time-course of sequential testing. 8. Evaluate patient data and derive appropriate diagnostic conclusions. 9. Discuss the use of BNP for prognosis and screening of patients for LV dysfunction. 10. Discuss the interpretations of slightly elevated levels of troponin and C - reactive protein (CRP) as they relate to ACS and risk analysis. This paper illustrates the diagnostic dilemmas in a small hospital emergency department when four patients present with similar symptoms of dyspnea, angina, and edema. These cases illustrate a new role for the clinical laboratory, as the new cardiac markers and protocols help overcome the ambiguity of symptoms, delays in diagnosis, and high costs of imaging tests that may be unavailable in many small hospitals. Frequently, dyspnea and chest pain are associated with cardiac disorders such as congestive heart failure (CHF), unstable angina, and acute myocardial infarction (MI). However, these same presenting symptoms may also be seen in obstructive pulmonary disorders, pulmonary embolism, pneumonia, and non-pulmonary disorders as diverse as anemia and anxiety. The recent addition of troponin and myoglobin to cardiac panels and the increasing use of accelerated cardiac protocols have improved speed and accuracy in the diagnosis of MI. While certain aspects of the interpretation of troponin data remain controversial, the use of accelerated testing protocols is gaining acceptance, following the recommendations of the National Academy of Clinical Biochemistry in 1999. With the introduction of rapid laboratory testing for B-type natriuretic peptide (BNP) in 2000, the diagnosis of CHF has also become faster, easier, and more reliable. A companion paper in this issue reviews plaque development, acute coronary syndromes (ACS), and pathophysiology of CHF.1 In addition, the biochemistry and physiology of BNP, and the clinical evidence supporting its use in the diagnosis, risk stratification, staging, and therapeutic monitoring of CHF patients are also reviewed. Rapid BNP assays and high… ABBREVIATIONS: ABG = arterial blood gas; ACS = acute coronary syndromes; BNP = B-type natriuretic peptide; CBC = complete blood count; CHD = coronary heart disease; CHF = congestive heart failure; CLS = clinical laboratory science; CMP = comprehensive metabolic profile; COPD = chronic obstructive pulmonary disease; ECG = electrocardiogram; ED = emergency department; EMT = emergency medical technician; hsCRP = high sensitivity C-reative protein; MI = myocardial infarction; NPV = negative predictive value; RAAS = renin-angiotensin-aldosterone system; UA = urinalysis; WBC = white blood count;. After reading the following articles, the reader will demonstrate his/her understanding of the material by achieving the following: 1. Describe the biochemistry of the BNP and the other natriuretic peptides. 2. Describe the major physiologic responses to the elevation of BNP levels. 3. Discuss the mechanism by which the binding of BNP to the target cell results in alteration of Na+ and water reabsorption. 4. Describe the formation of arterial plaque and the development of coronary artery disease and acute coronary syndromes (ACS). 5. Describe the physiological conditions that develop into CHF and cause the release of BNP. 6. Describe and interpret the diagnostic accuracy, sensitivity, specificity, and negative predictive values reported for rapid BNP assays. 7. Describe the trend toward “accelerated cardiac protocols,” including which markers are suggested, and the suggested time-course of sequential testing. 8. Evaluate patient data and derive appropriate diagnostic conclusions. 9. Discuss the use of BNP for prognosis and screening of patients for LV dysfunction. 10. Discuss the interpretations of slightly elevated levels of troponin and C - reactive protein (CRP) as they relate to ACS and risk analysis. [1]: #corresp-1