Acute coronary syndromes Flashcards
describe the term acute coronary syndromes
This term covers a spectrum of acute cardiac conditions from unstable angina to varying degrees of evolving myocardial infarction (MI)
how is unstable angina diagnosed?
history
ECG
troponin (no significant rise in
unstable angina)
how is unstable angina clinically classified:
*Cardiac chest pain at rest
*Cardiac chest pain with crescendo pattern
*New onset angina
how can acute myocardial infarction be diagnosed- ST elevation?
ST-elevation MI can usually be diagnosed on ECG at presentation
how can acute myocardial infarction be diagnosed- non ST elevation?
*Non-ST-elevation MI is a retrospective diagnosis made after troponin results and sometimes other investigation results are available
how can myocardial infarction be defined?
retrospectively as non-Q wave or Q-wave MI on the basis of whether new pathological Q waves develop on the ECG as a result of it
what are ST MIs and LBBB MIs associated with?
with larger infarcts unless effectively treated (and therefore more likely to lead to pathological Q wave formation, heart failure or death)
symptoms presenting for myocardial infarction
*Cardiac chest pain
* unremitting
*usually severe but may be mild or absent
*occurs at rest
*associated with sweating, breathlessness, nausea and/or vomiting
*one third occur in bed at night
what does myocardial infarction usually cause?
-permanent heart muscle damage although this may not be detectable in small MIs
- early mortality
- late mortality
what is a higher risk of myocardial infarction associated with?
higher age,
diabetes,
renal failure,
left ventricular systolic dysfunction (elevated NT- proBNP level)
and other risk factors
which patients have the highest mortality risk?
Patients presenting with cardiogenic shock or requiring ventilation following out-of-hospital cardiac arrest have the highest mortality risk
how are myocardial infarctions initially managed?
*Get in to hospital quickly – 999 call
*Paramedics – if ST elevation, contact primary PCI centre for transfer for emergency coronary angiography
*Take aspirin 300mg immediately
*Pain relief
what hospital management is done for myocardial infarctions?
*Make diagnosis
*Oxygen therapy only if hypoxic *Pain relief – opiates/ nitrates *Aspirin +/- platelet P2Y12 inhibitor *Consider beta-blocker
*Consider other antianginal therapy
*Consider urgent coronary angiography e.g. if troponin elevated or unstable angina refractory to medical therapy
what are the causes of ACS?
*Rupture of an atherosclerotic plaque and consequent arterial thrombosis is the cause in the majority of cases
*Myocardial infarction due to atherothrombosis is known as ‘type 1’ myocardial infarction
*Other causes of myocardial infarction usually fall under the umbrella of ‘type 2’ myocardial infarction
what are the causes of type 2 MI
- Myocardial oxygen demand/supply mismatch caused by sepsis, acute lung pathology, thyrotoxicosis, pulmonary embolism, anaemia, haemorrhage or other causes of hypotension/hypovolaemia – underlying stable coronary artery disease may or may not be a contributing factor
- coronary vasospasm without plaque rupture
- drug abuse (amphetamines, cocaine)
- dissection of the coronary artery related to defects of the vessel connective tissue
- thoracic aortic dissection
what is tako- tsubo cardiomyopathy?
Stress-induced cardiomyopathy that can masquerade as myocardial infarction.
what causes tako- tsubo cardiomyopathy?
Often caused by acute stress such as extreme emotional distress in susceptible individuals
what does tako- tsubo cardiomyopathy cause?
Causes transient left ventricular systolic dysfunction, typically ballooning of the left ventricular apex during systole that recovers over days or a few weeks with limited or no permanent damage
what is troponin?
A protein complex consisting of troponin C, troponin I and troponin T that regulates actin:myosin contraction.
what are Cardiac-specific isoforms of troponin T and troponin I?
are highly sensitive markers for cardiac muscle injury
what is the Role of soluble platelet agonists in thrombus formation at site of vascular damage?
promote healing
prevent bleeding to death
platelets adhere and secrete agonists to activate other platelets and attract them such as ADP ( ADP is the target of the anti platelet plug)
forma plug in the breech- good when needed but bad when responding to atherosclerotic rupture
fibronyltic system
e
n plasminogen
d I
o I
t I fibrin
h——->tPA—— I I
e Plasmin——–> I
l I
I Fibrin
u degradation products
m
when is P2Y 12 Inhibitors used?
sed in combination with aspirin in
management of ACS = ‘dual antiplatelet therapy’
what are the three oral drugs available of P2Y 12 inhibtors?
*Three oral drugs are available: clopidogrel, prasugrel and ticagrelor
PRASUGREL IS MOST EFFICIENT
describe the effect of Clopidogrel and prasugrel
are thienopyridines that have an irreversible effect on platelets
describe the effect of ticagrelor
Ticagrelor binds reversibly to P2Y12 receptors so has a more rapid offset of effect than thienopyridines
what are the adverse effects common to all of P2Y12 inhibitors ?
- Bleeding e.g. epistaxis, GI bleeds, haematuria * Rash
- GI disturbance
diosyncratic adverse effects of ticagrelor:
- Dyspnoea: usually mild and well-tolerated, but occasionally not tolerated and requires switching to prasugrel or clopidogrel
- Ventricular pauses: usually sinoatrial pauses, may resolve with continued treatment
what are GPIIb/IIIa antagonists used with
*Used in combination with aspirin and oral P2Y12 inhibitors in management of patients undergoing PCI for ACS
what increased risk do GPIIb/IIIa antagonists have?
*Increase risk of major bleeding
what do anticoagulants target
Target formation and/or activity of thrombin
what do anticoagulants inhibit?
- Inhibit both fibrin formation and platelet activation
doses of anticoagulants varying on procedure
Fondaparinux (a pentasaccharide) used in NSTE ACS prior to coronary angiography = safer than heparins as low level of anticoagulation used
* Full-dose anticoagulation used during PCI: options are heparins (usually unfractionated heparin; some centres use enoxaparin, a low-molecular-weight heparin) or the direct thrombin inhibitor bivalirudin (expensive, little used now)
* High dose heparin used during cardiopulmonary bypass for CABG surgery
what is given for initial pain relief in ACS?
morphine + metoclopramide, nitrates
- Initial pain relief if necessary – morphine + metoclopramide, nitrates
- Aspirin and P2Y12 inhibitor combination (assuming no contraindications
and confirmed diagnosis) - Anticoagulant: fondaparinux or heparin
- Consider intravenous glycoprotein IIb/IIIa antagonists for STEMI patient undergoing primary PCI
- Anti-anginal therapy – beta blocker, nitrates, calcium antagonist
- Secondary prevention – statins, ACEI, beta blocker, other antihypertensive
therapy - Heart failure patients – diuretic, ACEI, beta blocker, aldosterone antagonist (spironolactone, epleronone)
- Fibrinolytic therapy may be used for acute STEMI if primary PCI not available
when is coronary angiography usually performed?
for patients with troponin elevation or unstable angina refractory to medical therapy
what is the most frequent revascularisation procedure?
PCI
Why may some patients have no obstructive coronary artery disease?
- Actual diagnosis not ACS
- Plaque rupture without significant stenosis and resolution of
obstructive thrombus by the time of angiography - Stress-induced (Tako-Tsubo) cardiomyopathy without obstructive coronary artery disease
