B P5 C39 Non ST Elevation Acute Coronary Syndromes Flashcards
The pathogenesis of NSTE-ACS involves five processes operating singly or in various combinations:
(1) Disruption of an unstable atheromatous plaque
(2) Erosion of an atheromatous plaque
(3) Coronary arterial vasoconstriction
(4) Gradual intraluminal narrowing of an epicardial coronary artery caused by progressive atherosclerosis or restenosis after percutaneous coronary intervention (PCI)
(5) Oxygen supply-demand mismatch
Three mechanisms may lead to plaque disruption:
Most common mechanism of ACS?
Plaque fissure with inflammation
Plaque fissure without inflammation
Plaque erosion
Plaque rupture - most common
Plaque erosion - 40% of ACS cases
_________________ characteristically have large lipid pools with foam cells and a thin fibrous cap.
Plaques that rupture
The key steps in thrombus formation include _____.
(1) Adhesion of platelets to the arterial wall
(2) Platelet activation
(3) Platelet degranulation and further activation
(4) Parallel expression of tissue factor with activation of the coagulation cascade.
Four observations support the central role of coronary artery thrombosis in the pathogenesis of NSTE-ACS:
(1) Autopsy findings of thrombi in the coronary arteries typically localized to a ruptured or eroded atherosclerotic plaque
(2) Visualization by optical coherence tomography (OCT), invasive coronary arteriography, or coronary computed tomographic angiography (CCTA) of plaque ulceration and/or irregularities in the fibrous cap of atherosclerotic plaque, consistent with plaque rupture and thrombus formation;
(3) Elevation of serum markers of platelet activity, thrombin generation, and fibrin formation;
(4) Improvement in clinical outcome with antiplatelet and anticoagulant therapies.
Vasoconstriction causing dynamic obstruction of coronary arterial flow may result from _________________ or from ________________________
Spasm of epicardial coronary arteries (Prinzmetal’s vasospastic angina)
Constriction of small, intramural muscular coronary arteries (vasoconstrictors released by platelets, from endothelial dysfunction)
Atypical manifestations, such as dyspnea without chest discomfort and pain limited to the epigastrium or indigestion, represent “anginal equivalents.”
These atypical findings are more prevalent in _____ and can lead to under recognition, undertreatment, and worse outcomes
Women
Older adults
Diabetes mellitus (DM)
CKD
Dementia
Characteristics of plaque rupture
Lipid rich
Collagen poor, thin fibrous cap
Interstitial collagen breakdown
Abundant inflammation
Smoot muscle cell apoptosis
Macrophage predominance
Less expression of hyaluronidase-2 and hyaluronan-receptor CD 44
Large number of nonculprit plaques and grater panvascular instability
Male predominance
High level of LDL-C
Characteristic of plaque erosion
Lipid poor
PG and GSG rich
Nonfibrillar collagen breakdown
Few inflammatory cells
Endothelial cell apoptosis
Secondary neutrophil involvement
Profound alteration of hyaluronan metabolism resulting in hyaluronan accumulation
Smaller number of nonculprit plaques and less panvascular instability
Female predominance
High level ot TG
The most common abnormalities on the 12-lead ECG are _______________________, which are more likely to be present while the patient is symptomatic.
ST-segment depression and T wave inversion
If possible, comparison with a recent ECG is important because dynamic ST-segment depression as little as 0.05 mV is a sensitive (but not specific) marker for NSTE-ACS. Deep (>0.2 mV) T wave inversions are compatible with, but not necessarily diagnostic of, NSTE-ACS,
Transient ST-segment elevation lasting less than 20 minutes occurs in up to ______ of patients and suggests either UA or coronary vasospasm.
10%
Transient ST-segment elevation lasting less than 20 minutes occurs in up to 10% of patients and suggests either UA or coronary vasospasm.
__________________ are the biomarkers of choice to identify myocardial injury, thus distinguishing between NSTE-ACS and UA.
Cardiacspecific troponins I (cTnI) and T (cTnT)
Role of noninvasive testing in patients with established or suspected NSTE-ACS
(1) establishing the presence (or absence) of significant CAD
(2) diagnosing CAD as the cause of cTn elevation in patients who may have other explanations (see previous section)
(3) evaluating the extent of residual ischemia after initiation of medical therapy to guide management
(4) localizing the territory of ischemia before revascularization in patients with multivessel disease
(5) assessing left ventricular (LV) function.
The safety of early stress testing in patients with NSTE-ACS has been debated, but symptom-limited or pharmacologic stress testing appears to be safe after ______________ of stabilization without symptoms of active ischemia or other signs of hemodynamic or electrical instability.
at least 24 hours
For most patients, electrocardiographic exercise stress testing is recommended if the ECG at rest _______________________
lacks significant baseline abnormalities (e.g., ST depressions, bundle-branch block, electronic pacing)
If significant baseline ECG abnormalities are present, ________________________ should be performed before and immediately after exercise.
Stress perfusion or echocardiographic imaging
High-risk findings on the stress test:
Severe ischemia as reflected by ST-segment depression ≥0.2 mV before stage 3
Hypotension with exercise, ventricular tachyarrhythmia
New or worsening LV dysfunction
Recommended imaging in the ED in patients with chest discomfort and suspected ACS who are at low risk at presentation
CCTA
CCTA in patients with or suspected of having NSTE-ACS can help to (1) recognize or exclude the presence of epicardial CAD, (2) identify which vessel(s) have obstruction, and (3) assist in risk stratification and prognosis
CCTA in patients with or suspected of having NSTE-ACS can help to _____.
(1) recognize or exclude the presence of epicardial CAD
(2) identify which vessel(s) have obstruction
(3) assist in risk stratification and prognosis
_________can provide precise measurements of ventricular volumes and function, detect and assess ventricular wall edema, identify areas of infarcted versus viable hibernating myocardium, establish the presence of myocardial perfusion, quantify wall motion, and identify myocardium at risk in patients with NSTE-ACS
CMR
Addition of high-resolution late gadolinium enhanced imaging can help provide this information when CMR alone is inconclusive.
Features suggesting thrombus include
Lobular intraluminal masses with a rounded or polypoid shape;“haziness” of a lesion
Approximately ______ of patients with a clinical diagnosis of NSTEACS have significant coronary obstruction
% obstructive disease in multiple epicardial arteries
LM with multivessel disease _____
3VD _____
2VD _____
1VD _____
No obstruction _____
90%
LM with multivessel disease 10%
3VD 35%
2VD 25%
1VD 20%
No obstruction 10%
In the clinical setting, __________ are used most commonly to guide coronary stent placement
IVUS or OCT
Risk assessment scores in NSTE ACS
TIMI risk score
GRACE score
TIMI risk score
AAA B CC D
Age ≥65 yr
Prior aspirin
≥2 anginal episodes in prior 24 hr
↑ Cardiac markers
≥3 CAD risk factors
Known CAD (>50% stenosis)
ST deviation ≥0.5 mm of initial ECG
Appropriate indications for CCTA in patients with acute chest pain
Electrocardiogram negative or indeterminate for myocardial ischemia
Low-intermediate pretest likelihood by risk stratification tools
TIMI risk score of 0-2 (low risk) ideal or TIMI score of 3-4 (intermediate) in some cases
HEART score <3
At least 1 negative troponin value, including point-of-care assays
Equivocal or inadequate previous functional testing during index ED or within previous 6 months
Relative contraindications of CCTA in patients with acute chest pain
History of allergic reaction to iodinated contrast
eGFR 30 to <60 mL/min/1.73 m2
Factors likely to lead to nondiagnostic scans; specific will vary with scanner technology and site capabilities
Heart rate greater than site maximum for reliably diagnostic scans after beta blockers (usually 70-80 beats/min)
Contraindications to beta blockers and heart rate not controlled Atrial fibrillation or other markedly irregular rhythm
Body mass index >39 kg/m2
Absolute contraindications of CCTA in patients with acute chest pain
Known acute coronary syndromes
eGFR <30 unless on long-term dialysis
Previous anaphylaxis after iodinated contrast administration
Previous episode of contrast allergy after adequate steroid/antihistamine preparation
Pregnancy or uncertain pregnancy status in premenopausal women
_________________ vasodilators that increase myocardial blood flow and reduce myocardial oxygen requirements by lowering cardiac preload (systemic venodilation) and afterload (systemic arterial dilation), thereby diminishing ventricular wall stress, and they may have a mild antiplatelet effect
Nitrates
_____________ to nitrates may develop within 12 to 24 hours and can be mitigated by nitrate-free intervals or increasing the dose if symptoms persist. A
Tolerance
Important contraindications to nitrates include
Hypotension and use within 24 hours of a phosphodiesterase type 5 (PDE-5) inhibitor, sildenafil or vardenafil, or tadalafil within 48 hours
Relative contraindications to nitrates include hypotension (SBP <90 mm Hg), severe obstruction to LV outflow, large right ventricular infarction, or hemodynamically significant pulmonary embolism.
______________ inhibit the O 2oxygen consumption by lowering heart rate, BP, and myocardial contractility
Beta blockers
Beta blockers should be avoided in patients with
(1) acute or severe HF
(2) low cardiac output
(3) hypotension
(4) contraindications to beta blocker therapy (e.g., high-degree AV block, active bronchospasm)
(5) coronary vasospasm or acute intoxication with cocaine or methamphetamine because unopposed alpha-mediated coronary vasoconstriction may occur, worsening coronary spasm.
Data suggest that coadministration of _____and clopidogrel may blunt the antiplatelet effect of clopidogrel and is associated with an increase short- term risk of ischemic events.
Morphine
Morphine may act as both an analgesic and an anxiolytic; its ____ effects may be beneficial by reducing preload (particularly in patients who have experienced acute pulmonary edema), and _____ by increasing vagal tone.
Venodilator
Mildly reduces heart rate and BP
__________ effective in reducing ischemia in patients with NSTE-ACS and persistent ischemia despite treatment with full-dose nitrates and beta blockers, as well as in patients with contraindications to beta blockers and in patients with hypertension
CCBs
Contraindications to nondihydropyridine CCBs include
Significant LV dysfunction
Increased risk of cardiogenic shock
PR interval longer than 0.24 second
High-degree AV block
The short-acting formulation of the dihydropyridine nifedipine, which accelerates heart rate, can cause harm in patients with ACS when not co-administered with a beta blocker and should be avoided
Clinical effects of new and experimental therapies in NSTE_ACS
Ranolazine
Decreases recurrent ischemia and arrhythmias
Trimetazidine
Decreases short-term mortality
Nicorandil
Decreases arrhythmias and transient ischemia
Activates ATP-sensitive K + channels and dilates arterioles; may have ischemic precondition-like effec
Nicorandil
_________ acetylates platelet c genase 1 (COX-1), thereby blocking the synthesis and release of thromboxane A 2 (TxA2 ), a platelet activator, and reducing platelet aggregation and arterial thrombus formation.
Antiplatelet effects last for the lifetime of the platelets, approximately ____________
ASA
7 to 10 days
It is a cornerstone of antiplatelet therapy in patients with all forms of ACS, as well as those with chronic CAD.
Contraindications to ASA include _____.
Documented allergy (e.g., ASA- induced asthma)
Nasal polyps
Active bleeding
Known platelet disorder
Management of ACS now routinely includes dual-antiplatelet therapy (DAPT) consisting of both ASA and a P2Y12 inhibitor, which blocks the P2Y12 receptor and blocks adenosine diphosphate (ADP) binding to the surface of the platelets. The latter includes the oral thienopyridines _____, which are irreversible blockers, as well as a cyclopentyltriazolopyrimidine _____, which is a reversible P2Y12 inhibitor.
Clopidogrel, prasugrel - irreversible
Ticagrelor - reversible
_______________ the first thienopyridine to be widely studied in patients with CAD, NSTE-ACS, and patients undergoing PCI
Trial in NSTE ACS __________
Clopidogrel
CURE trial
Current guidelines recommend clopidogrel ( _________________ dose) in addition to aspirin in patients with NSTE-ACS who cannot receive ticagrelor or prasugrel (e.g., due to intolerance or very high risk of bleeding due to a prior intracranial hemorrhage or indication for full-dose oral anticoagulation or cost)
600 mg loading dose, 75 mg daily maintenance dose
Use of a 600-mg loading dose achieves a steady-state level of platelet inhibition after ___________
2 hours
Identify 2 treatment strategies of Clopidogrel in NSTE ACS
Preferred?
Two strategies for initiating clopidogrel therapy in patients with NSTE-ACS have evolved:
(1) starting clopidogrel at arrival or hospital admission or
(2) delaying treatment with clopidogrel until after coronary angiography and then administering the drug on the catheterization table if PCI is to be performed.
Initial strategy not preferred no longer recommended in patients in whom the coronary anatomy is not known and an early invasive approach is planned. 1
Formation of the active metabolite of ____________ requires only one step and is generated within 30 minutes of ingestion.
Trial?
Prasugrel
TRITON-TIMI 38 trial
The primary composite of CV death, MI, or stroke was reduced significantly by 19% in the patients randomized to prasugrel through 15 months of follow-up.This benefit was driven by a significant 24% reduction in MI and was particularly striking in patients with diabetes (30% reduction).
In addition, prasugrel markedly reduced the rate of definite or probable stent thrombosis (by 52%), particularly in patients with drug-eluting stents (DESs) (64%); thus prasugrel should be considered in patients who present with stent thrombosis despite compliance with clopidogrel therapy.
Patients with NSTE-ACS (<75 years of age) selected for medical management without revascularization (n = 7,243) were randomized within 10 days of the index event to prasugrel 10 mg daily versus clopidogrel 75 mg daily (patients <60 kg received prasugrel 5 mg daily.) In addition, NSTE-ACS patients ≥75 years of age (n = 2,083) were randomized to prasugrel 5 mg daily versus clopidogrel 75 mg daily.
Among patients with NSTE-ACS selected for medical management without revascularization, the long-term use of prasugrel did not reduce adverse outcomes compared with clopidogrel. Major bleeding was similar between groups; however, major or minor bleeding appeared increased with prasugrel.
TRILOGY ACS (Targeted Platelet Inhibition to Clarify the Optimal Strategy to Medically Manage Acute Coronary Syndromes)
These results differ from a clear benefit of prasugrel over clopidogrel in reducing cardiovascular events in patients with planned PCI seen in the TRITON-TIMI 38 trial.