STEPUP Cardiovascular System: Ischemic Heart Disease - Unstable Angina Pectoris Flashcards
What is the pathophysiology of unstable angina pectoris? Why is USA significant? What may it lead to?
1) With USA, oxygen demand is unchanged. Supply is decreased secondary to reduced resting coronary flow. This is in contrast to stable angina, which is due to increased demand
2) It indicates stenosis that has enlarged via thrombosis, hemorrhage, or plaque rupture
3) It may lead to total occlusion of a coronary vessel
Which patients are described to have USA?
1) Patients with chronic angina with increasing frequency, duration, or intensity of chest pain
2) Patients with new-onset angina that is severe and worsening
3) Patients with angina at rest
How do you distinguish between USA and NSTEMI?
It is based entirely on cardiac enzymes. The latter has elevation of troponin or creatine kinase-MB (CK-MB). Both USA and NSTEMI lack ST segment elevations and pathologic Q waves
What should you rule out when diagnosing USA? What should you watch out for during diagnosis?
1) Perform a diagnostic workup to exclude MI in all patients
2) Patients with USA have a higher risk of adverse events during stress testing. These patients should be stabilized with medical management before stress testing or should undergo cardiac catheterization initially
What are the components of acute treatment for USA?
1) Hospital admission on a floor with continuous cardiac monitoring
2) Aggressive medical management
3) Cardiac catheterization/resvascularization
What should be given during hospital admission for USA?
1) Continuous cardiac monitoring
2) Establish IV access and give supplemental oxygen
3) Provide pain control with nitrates and morphine
What does aggressive medical management for USA include?
Treat as in MI except for fibrinolysis
1) Aspirin
2) Clopidogrel
3) Beta blockers - first-line therapy if there are no contraindications
4) Low-molecular-weight heparin (LMWH) is superior to unfractionated heparin
5) Nitrates are first-line therapy
6) Oxygen if patient is hypoxic
7) Glycoprotein IIb/IIIa inhibitors (abciximab, tirofiban) can be helpful adjuncts in USA, especially if patient is undergoing PTCA or stenting
8) Morphine is controversial - provides good pain relief but may mask worsening symptoms
9) Replacement of deficient electrolytes, especially K+ and Mg2+
What did the CURE trial show for clopidogrel? How long should patients with USA be treated with clopidogrel for?
1) Shown to reduce the incidence of MI in patients with USA compared with aspirin alone in the CURE trial. This benefit persists whether the patient undergoes revascularization with PCI or not
2) Patients presenting with USA should generally be treated with aspirin and clopidogrel for 9 to 12 months, in accordance with the CURE trial. This may be altered however, according to the bleeding risk of each patient
What is the goal of Low-molecular-weight heparin treatment in unstable angina? How long should it be continued for? What is the drug of choice?
Goal is to prevent progression or development of a clot
1) Should be continued for at least 2 days
2) Enoxaparin is the drug of choice based on clinical trials (ESSENCE trial)
What percentage of patients with USA improve with aggressive medical management?
More than 90% within 1 to 2 days
Why is the choice of invasive management (early catheterization/revascularization within 48 hours) versus conservative management (catheterization/revascularization only if medical therapy fails) controversial? What should you do next if a patient with unstable angina responds to medical therapy? What is medical therapy fails to improve unstable angina and/or if ECG changes indicative of ischemia persist after 48 hours? What can the TIMI risk score be used for?
1) No study has shown a significant difference in outcomes between these two approaches
2) If patient responds to medical therapy, perform a stress ECG to assess need for catheterization/revascularization. Many patients with USA that is controlled with medical therapy eventually require revascularization
3) If medical therapy fails to improve symptoms and/or ECG changes indicative of ischemia persist after 48 hours, then proceed directly to catheterization/revascularization. Additional indications for PCI include hemodynamic instabiliy, ventricular arrhythmias, and new mitral regurgitation (MR) or new septal defect
4) The TIMI risk score can be used to guide the decision on conservative versus more aggressive treatment
What should be done after acute treatment of USA for management?
1) Continue aspirin (or other antiplatelet therapy), beta blockers (atenolol or metoprolol), and nitrates
2) Reduce risk factors:
a) Smoking cessation, weight loss
b) Treat diabetes, HTN
c) Treat hyperlipidemia - patients with any form of CAD (stable angina, USA, NSTEMI, STEMI) should be started on an HMG-CoA reductase inhibitor regardless of LDL level. Clinical trials of statins have shown the efficacy of such therapy for secondary prevention in CAD
What is acute coronary syndrome (ACS) a result of? What conditions are included under ACS?
1) The clinical manifestations of atherosclerotic plaque rupture and coronary occlusion
2) USA, NSTEMI, or STEMI
What can stress testing only detect? What does this mean for risk of MI?
1) Stress testing only detects flow-limiting high-grade lesions
2) Thus, can still have MI despite negative stress test because mechanism of MI is acute plaque rupture onto a moderate lesion
Why are USA and NSTEMI often considered together?
Because it is very difficult to distinguish the two based on patient presentation. If cardiac enzymes are elevated, then the patient has non-ST segment elevation MI
