IC6 Acute Myocardial Infarction Flashcards
ACS vs CCS
ACS: STEMI, NSTEACS
- SOB at rest (dyspnea)
CCS: stable angina, stable IHD
- SOB on exertion, relieved with rest
Describe the difference in ECG findings between STEMI and NSTEACS
STEMI: ST elevation
- implies complete blockage of coronary artery
NSTEACS: ST depression/normal/inversion
- implies partial blockage of coronary artery
Describe the difference in troponin levels (hs-trop) in STEMI and NSTEACS
STEMI: because of complete blockage, more muscular death, hence larger amount of troponin release
NSTEACS: partial blockage, lower amount of troponin release
What other conditions may present with troponin rise?
- Myocarditis
- Takotsubo syndrome (heart muscle weakened)
- Congestive heart failure
Besides ECG and troponin, what other lab tests might be done to diagnose ACS?
- Renal function
- Baseline CBC and coagulation panel
- Fasting lipid panel
Which groups of patients may have atypical/silent presentation of MI and why?
What are some examples of atypical symptom presentation?
Diabetics (underlying neuropathy), >=75yo, women, impaired renal function, dementia
- Atypical symptoms include: epigastric pain, indigestion, stabbing, pleuritic chest pain, exertional dyspnea
Differential diagnosis of MI
- GERD: exclude sour taste in mouth, burping
- PUD
- Hypoglycemia: exclude sweating, dizziness
- Pneumonia: exclude fever, cough
What is percutaneous coronary intervention (PCI)?
What is the aim?
PCI - coronary angioplasty used to open clogged arteries
- Catheter with balloon inserted via catheter insertion site (either femoral or radial approach) to open blocked vessel by inflating the balloon that will compress the plaque
AIM: to achieve reperfusion
Types of stents used in PCI, and their thrombogenicity
Bare metal stent
- Highly thrombogenic
1st gen drug-eluting stent
- Paclitaxel, Sirolimus
- More thrombogenic
2nd gen drug-eluting stent
- Everolimus, Zotarolimus
- Less thrombogenic
3rd gen drug-eluting stent
- Use polymer-free stent, or bioresorbable stent, or drugs with high lipophilicity - for faster transfer
Discuss the advantages and disadvantages of drug-eluting stents
Advantage:
- Immunosuppressive and anti-proliferative drugs prevent inflammation from highly thrombogenic stent
- Combat restenosis (prevent cell proliferation and narrowing of the artery)
Disadvantage:
- Longer time to heal => higher bleeding risk
- Therefore although default DAPT for ACS is 12 months, for DES may give for at least 3 months
Difference between in-stent thrombosis and in-stent restenosis
In-stent thrombosis:
- Thrombus form inside stent => risk of another MI
- Therefore, DAPT is indicated to prevent clot formation
In-stent restenosis
- Thrombus forms outside of stent due to the proliferation of endothelial cells
AMI Treatment Algorithm
What is the first line treatment for reperfusion in AMI?
Percutaneous coronary intervention (PCI)
Must be performed within 90min, (at most not exceeding 120min)
AMI Treatment Algorithm
PCI procedure should be accompanied with what first choice of IV anticoagulant?
Describe the dosing and monitoring parameter, as well as any drug it might be used in combi with.
If previous LMWH or heparin was used, what should be done?
IV Bolus UFH 2000-5000 units should be administered to achieve activated clotting time (ACT) of 250-300 seconds; repeat bolus up 10000 units as needed to maintain ACT throughout PCI
If IV GP IIb/IIIa inhibitor (Eptifibatide) is used, repeat bolus of UFH up to max 7000 units as needed to maintain ACT throughout PCI
If previous LMWH or heparin was used, check ACT prior to bolus; if ACS >2000 secs, do not use bolus
AMI Treatment Algorithm
Activated clotting time targets for UFH during PCI
Guidelines recommend target ACT values within 200 to 250 s with planned use of glycoprotein IIb/IIIa inhibitors for the guidance of UFH therapy during primary PCI procedures
Eptifibatide half life and renal adjustment
Short half-life (2-4h) therefore needs to be infused for 72h
Renal dose adjustment when CrCL <50ml/min; not to be used in ESRD
AMI Treatment Algorithm
PCI procedure can be accompanied with what other IV anticoagulant?
Any monitoring parameters?
IV LMWH (Enoxaparin) is only used for PCI if last SQ LMWH is within specific timeframe of 8-12h before PCI procedure
Anti-Xa levels may be measured in renally impaired, or pregnant patients
AMI Treatment Algorithm
What is the role of anticoagulants during PCI in AMI?
Anticoagulants combat thrombus expansion
AMI Treatment Algorithm
In the event that PCI cannot be done, what should be done?
Start Tenecteplase for reperfusion in AMI
- dosed by body weight
- administered as single intravenous bolus over 5-10s
AMI Treatment Algorithm
In what situations might Fibrinolysis be done instead of PCI
- Primary PCI is delayed >120min
- Contraindications to receiving contrast dye
AMI Treatment Algorithm
What are some contraindications to the use of Fibrinolytics?
Absolute CI:
- ischemic stroke within past 3 months (except onset in past 4.5h)
- hemorrhagic stroke
- severe uncontrolled HTN
- intracranial or intraspinal surgery within 2m
Relative CI:
- recent major surgery (<3 weeks)
- active peptic ulcer
- pregnancy
AMI Treatment Algorithm
Describe the choice of P2Y12 inhibitor and duration of DAPT treatment in MI
Ticagrelor - ACS x 12m
Clopidogrel - CCS x 6m
Followed by lifelong SAPT
*If patient has high bleeding risk may consider shorter duration of DAPT (e.g., 3m)
AMI Treatment Algorithm
If patient has high bleeding risk and ACS, what DAPT treatment should be used?
(a) shorten DAPT (ticagrelor) duration to only 3m;
OR
(b) use clopidogrel as the P2Y12i right from the outset;
OR
(c) de-escalate from DAPT (ticagrelor) to DAPT (clopidogrel) to complete the recommended 12 months.
AMI Treatment Algorithm
Loading and maintenance doses of Ticagrelor, Clopidogrel, Aspirin
Ticagrelor: 180mg LD, 90mg BD
Clopidogrel: 300/600mg LD, 75mg OD
Aspirin: 300mg LD, 100mg OD
AMI Treatment Algorithm
When might Clopidogrel 300mg or 600mg loading dose be considered?
600mg: stable CAD pt undergoing coronary stent implantation
300mg: pt =<75yo, received thrombolysis
*300-600mg for CCS; 300mg for ACS
FYI: Clopidogrel may be used as monotherapy for PAD: 75mg
