ami
acute myocardial infarction (AMI/STEMI/NSTEMI)
Pre-hospital Mx of AMI
1 in 300 patients with acute ischaemic chest pain transported to hospital via private car will have a cardiac arrest en route
if ambulances have access to 12 lead ECG's then direct communication with an angiography lab potentially bypassing ED may be the most expeditious Mx once AMI has been diagnosed on the ECG.
if 12 lead ECG is not available, then ambulance protocols usually consist of:
oxygen if hypoxic or in shock
cardiac monitor, aspirin 300mg o, GTN s/lingual and immediate transfer to an ED, preferably at a hospital with interventional angiography services.
ED Mx of AMI
initial diagnosis and Mx
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oxygen if SaO2 < 93% or if in shock (oxygen is no longer advised to be given routinely!)
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iv access, bloods sent for FBE, U&E, glucose, CK, troponin +/- clotting
avoid excessive venipunctures which may cause problems after thrombolysis - take blood at time of cannulation
with-hold all caffeine-containing foods (may worsen ischaemia via tachycardia and interfere with thallium scans, etc)
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in particular, look for:
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ECG Diagnosis of AMI - particularly RV infarct which may C/I GTN Rx and may require iv fluid Rx to maintain BP.
if anterior MI:
if inferior MI:
be prepared for temporary AV block:
with-hold verapamil, diltiazem, mibeframil, beta blockers, digoxin
may need atropine, isoprenaline or temporary pacemaker
if complete heart block with idioventricular escape rhythm:
DO NOT give lignocaine as may cause asystole!
if rate < 40 or compromised then try atropine 0.6-1.2mg
if rate still < 40 try isoprenaline boluses +/- infusion (avoid causing tachycardia if possible)
if no success then:
look for RV involvement (30-50% of inf. AMIs; do right side ECG leads, JVP often high):
look for posterior involvement:
rapid history and examination to help exclude confounding diagnoses or complications of AMI:
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aim to maintain systolic BP > 90mmHg
GTN - sublingual +/- patch +/- infusion if ongoing pain
C/I to GTN includes:
RV infarct
hypotension
recent Viagra use
iv
morphine titrated in 2.5mg doses for pain relief
CXR - to further exclude chest pathologies such as dissection, pneumonia, LVF and as a baseline
ST elevation on ECG or new LBBB with cardiac chest pain > 20min, or cardiogenic shock/APO with acute infarct
if < 12hrs since onset of maximal pain, consider either:
if > 12hrs, or C/I to the above, then Mx as for non-ST elevation myocardial infarct (NSTEMI)
no ST elevation and no new LBBB but raised troponin (NSTEMI)
early discussion with cardiology to decide on medical Mx or early angiography
anti-thrombotic agents as per cardiology, eg:
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if ongoing pain and chance of early angiography then
heparin, otherwise use
enoxaparin - may need initial iv dose then sc - reduce dose in elderly and those with impaired creatinine clearance.
commence a statin if not already on one, eg.
atorvastatin 80mg daily
consider oral
beta adrenergic blockers (NOT iv unless severe HT or arrhythmia!!) in the 1st 24 hours (no hurry) unless C/I
(level I evidence, grade A recommendation)
contra-indications to beta blockers in acute coronary syndromes:
if angiogram shows normal vessels, consider:
role of anticoagulation post-AMI:
adjunctive Rx for coronary re-perfusion
prevention of extension of thrombosis in NSTEMI / unstable angina patients
prevention of re-occlusion of coronary vessels
DVT prophylaxis
prevention of cerebral emboli:
Transmural anterior infarcts:
A large proportion of pts with transmural anterior infarcts develop mural thrombi which are the cause of 90% of cerebral emboli in patients post-AMI (overall incidence post-AMI is 3-4%).
Most cerebral emboli post-AMI occur in the 1st 3months.
Other risk factors for cerebral emboli post-AMI are:
Thus, pts with transmural anterior infarcts are often anticoagulated with full doses of heparin, followed by Rx with warfarin for 3mths.
Atrial fibrillation:
ami.txt · Last modified: 2020/06/07 22:29 by wh