4. Cardiac causes of cardiac arrest Flashcards
types of ACS?
STEMI
NSTE ACS (NSTEMI, unstable angina)
ACS in most cases results from ___ ___ disease, and is initiated by the rupture of erosion of an ____ ____ within a coronary artery
coronary artery
atherosclerotic plaque
describe the sequentia of events that leads to ACS then an atherosclerotic plaque within a coronary artery erodes/ ruptures?
1) acute thrombosis within the vessel lumen
2) contraction of smooth muscle cells in the artery wall resulting in vasoconstriction that reduces the lumen of the artery
3) associated partial or complete obstruction of the lumen, often with embolism of thrombus into the distal part of the vessel
all leads to sudden and critical reduction in blood flow to the myocardium
T/F: you may see ECG changes in unstable angina
true- may be evidence of acute myocardial ischaemia (usually ST-segment depression) or show non-specific abnormalities (e.g. T wave inversion)
all pts with unstable angina should have their risk assessed with an established risk calculator e.g.
GRACE
what ECG findings are suggestive of STEMI?
ST segment elevation or new LBBB
T/F: the amount of troponin released reflects the amount of myocardium damaged
true
left untreated, a STEMI will lead to the development of __ waves on the ECG
Q
T/F: confirmation of elevated troponin is required to make the initial diagnosis of STEMI
False
clinical signs on examination of aortic dissection?
hypotension, loss of peripheral pulse, R-R delay, aortic regurgitation, signs of stroke from carotid artery involvement
treatment of STEMI?
reperfusion therapy
ideally PCI
if that can’t be achieved within 120 minutes of onset of CP, fibrinolytic therapy should be considered
anteroseptal infarction - which ECG leads and which coronary artery?
V1-4 (extension to V5-6, I and aVL indicates anterolateral)
LAD
an ANTERIOR/LATERAL/INFERIOR infarct has a worse prognosis
anterior
inferior infarction - which ECG leads and which coronary artery?
II, III and aVF
Right coronary or, less commonly, the circumflex artery
lateral infarction - which ECG leads and which coronary artery?
V5-6, and/ or I/ aVL
Circumflex artery or diagnoal branch of the LAD
posterior infarction - which ECG leads and which coronary artery?
reciprocal ST-segment depression in the anterior leads
Most often right coronary artery but can also be a dominant circumflex artery
what ECG changes reflect posterior Q wave development?
development of a dominant R wave in V1-V2 (reflects posterior Q wave development
suspicion of posterior ECG can be confirmed by repeating the ECG with what change?
addition of posterior leads (V7-10)
Right ventricular infarction may be present in up to one third of patients with ____ and ____ STEMI
inferior and posterior
a diagnosis of extensive RV infarction is suggested by what clinical signs?
fluid responsive hypotension and signs of high systemic venous pressure (e.g. jugular venous distension) without pulmonary congestion
extensive RV infarction may be seen on an ECG when ST-segment elevation in what lead accompanies an inferior or posterior STEMI?
V1
the ECGs of people with SAH or TBI can show ECG changes including…
ST segment depression or elevation, or T-wave inversion
what ECG changes can happen in people with major PE?
T wave inversion in leads V1-4
T/F: the greater the troponin, the greater the risk of a further event or death
true
what other life threatening conditions presenting with chest pain can have elevated troponins?
including PE, aortic dissection and myocarditis
what other conditions can present with elevated troponin?
acute or chronic heart failure, arrhythmias, chronic renal failure and acute sepsis
what additional ECG leads can be helpful in detected an right ventricular infarction?
right precordial leads, esp V4R
T/F: the ST-segment depression and T wave inversion that may occur in NSTEMI are less clearly related to the site of myocardial damage than the changes in STEMI
true
What is the most important non-invasive imaging modality in the acute setting for ACS?
ECHO (left ventricular systolic function is directly related to prognosis and, in someone with acute chest pain, regional wall motion abnormalities increase the likelihood of an ACS)
ECHO can be used to diagnose complications of an acute MI such as (1) or (2), both of which require urgent surgical correction
1) ventricular septal defect
2) severe mitral regurgitation
most accurate risk stratification score, both on admission and over 6 months?
GRACE
What variables increase risk of major bleeding following ACS treatment?
increased age
known bleeding complications
renal impairment
low body weight
immediate treatment for ACS?
MONA
Morphine (IV opiates given with antiemetic)
Oxygen (only if sats <94%)
Nitrates (sublingual GTN - unless hypotensive)
Aspirin 300mg oral (crushed or chewed)
Treatment options for STEMI (or AMI with new LBBB)
if within 12 hr symptom onset, mechanical or pharmacological reperfusion without delay
- PPCI (preferred method)
- fibrinolytic therapy
T/F: emergency PCI may be considered >12hr from symptom onset
true - if clinical or ECG evidence of ongoing ischaemia
what is the target ‘call-to-balloon’ time in a STEMI?
<120mins (if PPCI can’t be achieved in this timeframe, consider fibrinolytic therapy)
in addition to aspirin, all pts should be given one of the platelet ADP receptor blockers prior to PPCI e.g.
clopidogrel 600mg
prasugrel 60mg
ticarelor 180mg
What antithrombotic therapy is contraindicated if >75y/o, <60kg or history of bleeding or stroke
prasugrel
T/F: fibrinolytic therapy is less effective than PPCI in a STEMI
true
all pts receiving a fibrinolytic agent for STEMI must receive: ___ 300mg and ___ 180mg
also antithrombin therapy (to minimise risk of further occlusion) e.g.
aspirin 300
ticagleror 180 (or clopidogrel 300 if high bleeding risk)
antithrombin therapy > LMWH OR unfractioned heparin OR fondaparinux
Typical indication for immediate fibrinolytic therapy for acute myocardial infarction
1) presentation within __ hours of onset cardiac CP and PCI not possible within ___ minutes
AND
2) ST segment elevation >__ small box(es) in 2 adjacent chest leads
OR
3) >___ small box(es) in 2 or more adjacent limb leads
OR
4) dominant R waves and ST depression in ___ - ___ (posterior infarct)
OR
5) new onset ____
1) 12, 120
2) 2
3) 1
4) V1-3
5) LBBB
absolute contraindications for fibrinolytic therapy
prev. haemorrhagic stroke
ischaemic stroke during past 6 months
CNS damage or neoplasm
recent (3week) major surgery, HI, or other major trauma
active internal bleeding or GI bleeding within the past month
known or suspected aortic dissection
known bleeding disorder
T/F: in 5% of pts receiving fibrinolysis for STEMI, reperfusion is not achieved
false- 10-30%
Failure of ST-segment elevation to resolve by more than __% compared to pre-treatment ECG suggests that fibrinolytic therapy has failed to re-open the culprit artery
50
(symptoms are not a reliable guide to reperfusion- many pts will have had opiate analgesia)
What to do in cases of failed reperfusion (or re-occlusion and further infarction with recurrent of ST-segment elevation?
transfer without delay to a cardiac catheter lab for PCI (“rescue PCI”)
T/F: there is no evidence of benefot from immediate reperfusion therapy in most patients with NSTE ACS
true - there is no role for fibrinolytic therapy in these patients
1) to prevent further thrombus formation following initial treatment in NSTE ACS, given ___ 2.5mg daily + ___ 75mg daily after the initial 300mg loading dose
2) in addition to aspirin, pts with elevated trop (NSTEMI) or are planned for angiography +/- revascularisation should be given one of the platelet ADP receptor blockers e.g. ____ 60mg, _____ 180mg or ____ 300mg
1) fondaparinux 2.5mg
aspirin 75mg
2) prasugrel 60mg
ticagrelor 180mg
clopidogrel 300mg
Prasugrel contraindications
> 75 years
<60kg
history of bleeding or stroke
in certain high-risk pts with NSTE-ACS, if early PCI is planned, a _____ inhibitor may be considered
glycoprotein IIb/IIIa
Treatments to reduce myocardial oxygen demand in NSTE ACS?
1) start ______ (consider diltiazem if contraindicated)
2) avoid ______ e.g. nifedipine
3) consider IV _____ infusion if angina persists or recurs after s/l
4) consider early introduction of _______, esp if there is LVSD/ heart failure
1) beta blocker
2) dihydropyridine CCBs
3) nitrate
4) ACEI
1) Patients with suspected unstable angina without high risk features (ECG and trop normal, low GRACE score) should undergo further risk assessment by what means?
2) what about pts with UA and high risk features or NSTEMI?
1) non-invasive imaging
2) consider for early investigation by percutaneous coronary angiography
NSTEMI: require assessment by coronary angiography within ___ hours of presentation
72
What measures are included in secondary prevention for ACS?
- antithrombotic therapy (aspirin 75mg OD for life + clopidogrel 75mg OD/prasugrel 10mg OC/ ticagrelor 90mg BD for at least a year if undergoing PCI
- preservation of LV function with use of an ACEI (+aldosterone antagonist for those with HF with reduced LVEF)
- beta blockade (reduces mortality + size of subsequent MI)
- high dose statin for cholesterol reduction (+low fat, high fibre diet and regular exercise)
- smoking cesssation
- antihypertensive treatment
T/F: if an arrhythmia (inc VF/pVT) occurs within 24-48hrs of confirmed ACS, an implantable ICD is indicated
false - NOT indicated unless the pt has persistent severely impaired LV function at least 4 weeks post ACS
(ICD normally indicated if the arrhythmia occurred >24-48hr after an ACS)
What arrhythmia on an ECG is commonly seen after reperfusion and may provide strong indication that thrombolysis has been achieved
accelerated idioventricular rhythm (often transient and don’t require treatment)
AV block in the context of an inferior acute MI
inferior
treat symptomatic bradycardia with atropine, consider temporary pacing only if bradycardia and hypotension persist after atropine
T/F: AV block in the context of acute inferior AMI usually implies extensive myocardial injury and poor prognosis
false- usually transient in the context of INFERIOR AMI, treat with atropine and consider pacing only if bradycardia persists after atropine
AV block in acute ANTERIOR AMI usually implies extensive myocardial injury and poor prognosis - often atropine resistant, do not delay pacing
management of VF/VT cardiac arrest that occurs in the cath lab?
up to 3 stacked shocks should be attempted - if there’s no ROSC, commence the standard ALS algorithm
Treatment of patients presenting with heart failure complicating AMI?
1) for immediate symptomatic treatment
2) to maintain symptom control
3) for patients with heart failure or significant LV systolic impairment (EF <40%)
1) loop diuretic e.g. furosemide and/or GTN for
2) regular loop diuretic, ACEI titrated as tolerated (ARB if not tolerated), beta-blocker
3) aldosterone antagonist (eplerenone or spironolactone)
how does cardiogenic shock present
hypotension with poor peripheral perfusin, often with pulmonary oedema, drowsiness/ confusion, oliguria
very high mortality
T/F: syncope that occurs during exertion is a reassuring feature
false - exertional syncope should raise concern ?cardiac cause
In many people with a long QT syndrome, ____ blockage may be the only treatment needed to reduce risk of SCD to a minimum
beta (ICD may be needed if this is insufficient)
What intervention restores life expectancy to normal in complete AV block?
pacemaker implantation
