Download Management of Acute Myocardial Infarction

Intensive Care Unit, Prince of Wales Hospital, Chinese University of Hong Kong
MANAGEMENT OF ACUTE MYOCARDIAL INFARCTION
Diagnosis of MI (WHO definition) is based on the presence of at least 2 of the
following 3 criteria:
1. A clinical history of ischaemic-type chest discomfort
2. Changes on serially obtained ECG tracings
3. A rise and fall in serum cardiac markers
Aim of initial management
1. Identify true ST-elevation infarcts early
2. Provide early aggressive reperfusion
3. Monitor for complications of AMI (cardiogenic shock, APO, arrhythmias)
Note: thrombolytic therapy is highly effective in patients with ST elevation or
presumably new LBBB (obscures the ECG diagnosis of MI). However,
thrombolytic therapy is ineffective and possibly even harmful in unstable
angina (ST depression presentation) and non-ST-elevation MI (NSTEMI)
Patients who are referred to the ICU with AMI invariably have complications as a
direct result of the MI or have other conditions warranting ICU care (eg.
concurrent sepsis, other organ dysfunction, peri-operative AMI requiring a period
of observation)
General measures
• Oxygen therapy
• Pain relief
• Avoid valsalva manoeuvres
• Select ECG monitoring based on infarct location and rhythm
Investigations and Monitoring
• 12-lead ECG done on presentation or ICU admission. Non-diagnostic ECG
should be repeated at 15-30 min interval followed by every 6 hourly for
the first 24 hours of admission
• 2 sets of cardiac Troponin T. First set should be done on presentation
and if normal, do 2nd set at > 6 hours apart
• CPK daily for 3 days
• Other routine bloods including clotting profile
• CXR
• Intra-arterial pressure monitoring
• CVP if haemodynamic iunstable or need inotropic agents or vasopressors
• Indications fo Swan Ganz – severe or progressive CHF or pulmonary
oedema; cardiogenic shock or progressive hypotension; suspected
mechanical complications of acute infarction ie VSD, papillary muscle
rupture or pericardial tamponade
Page 1 of 5
Intensive Care Unit, Prince of Wales Hospital, Chinese University of Hong Kong
Drug therapy
Aspirin – give stat 320 mg on day of AMI. Then 160 mg daily
Nitroglycerin
Indications
For first 24-48 hours in patients with Ami and CHF, large anterior
infarction, persistent ischaemia or hypertension
Continued use beyond 48 hours in patients with recurrent angina or
persistent pulmonary congestion
Contraindications
Initial systolic BP < 90 mmHg
Marked bradycardia (< 50bpm) or tachycardia
Suspected RV infarction
Thrombolysis – see below for more details
Heparin
Indications
IV unfractionated heparin (UH) for patients post thrombolysis with
rt-PA – see PWH thrombolysis protocol
IV UH for patients undergoing primary percutaneous coronary
intervention (PCI)
LMWH SC for patients with NSTEMI (enoxaparine 1 mg/kg bd) not
given thrombolysis and with no contraindications to heparin
Beta-blockers
Indications
Start within 12 hours post AMI if no contraindication irrespective of
concomitant thrombolysis or primary PCI
Continuing or recurrent ischaemic pain
Tachyarrhythmias, eg rapid AF
NSTEMI
ACEI
Indications
Within first 24 hours of a suspected AMI with clinical heart failure in
absence of hypotension (SBP>100 mmHg)
AMi with LV ejection fraction < 40% or patients with clinical heart
failure during and after convalescence from AMI
Statins
Evidence show that starting statin early (eg atorvastatin) beneficial. Can
start even when patient still in ICU
Intra-aortic Balloon Counterpulsation
Indications for placement
1. Cardiogenic shock not quickly reversed with pharmacological
therapy as a stabilizing measure for angiography and prompt
revascularization
Page 2 of 5
Intensive Care Unit, Prince of Wales Hospital, Chinese University of Hong Kong
2. Acute mitral regurgitation or VSD complicationg MI as a stabilizing
therapy for angiography and repair/revasculariztion
3. Recurrent intractable ventricular arrhythmias with haemodynamic
instability
4. Refractory post-MI angina as a bridge to angiography and
revascularization
Consult cardiologist for all patients requiring IABP. However, in our unit, if
patients are going for prompt surgical revascularization or if patient belongs to
the cardiac surgical unit, the cardiac surgeons will insert the IABP.
Thrombolysis
Decision for thrombolysis should be discussed with the on-call ICU senior and oncall cardiologist
Who should be thrombolysed?
• Typical chest pain lasting more than 30 minutes
• ST elevation (greater than 0.2 mV, in 2 or more contiguous leads),
</= 12 hours from AMI, age between 21 and 75 years (age >75
years, overall risk of mortality is high with or without therapy.
Relative benefit of therapy is reduced. However, can still be
considered on individual basis)
• LBBB and history suggesting AMI
• Benefit less for inferior AMI, except for subgroup of RV infarction
(ST elevation RV-4) or anterior-segment depression indicative of a
posterior current of injury (occlusion of a large circumflex
coronary artery)
PWH CCU Guidelines on thrombolysis
Which thrombolytic regimens?
1. Streptokinase 1.5 million units in 100 mls NS infused over 1 hour
2. Accelerating rt-PA (more effective, but more expensive and carry
more risk of intracranial haemorrhage)
15 mg bolus
0.75 mg/kg over 30 mins (max 50mg)
0.5 mg/kg over next 60 mins (max 35 mg)
Total dose <100 mg
IV heparin (4000 units IVI bolus at the 3rd hour ie 1 and ½
hours after completion of rt-PA; keep ACT < 300, then 800
units /hour to keep APTT 2x control or 60-85 seconds for 48
hours)
Who should not be given thrombolysis (but fulfill criteria for thrombolysis)?
• Pregnant patient
• Currently menstruating
Page 3 of 5
Intensive Care Unit, Prince of Wales Hospital, Chinese University of Hong Kong
•
•
Post-traumatic CPR
Known bleeding disorders (CVA < 3 months, history of intracerebral
hemorrhage, GU bleeding < 3 months, other bleeding tendency…, on
warfarin)
• Recent brain or abdominal surgery within 2 weeks
• Active pancreatitis
• Uncontrolled hypertension BP > 200/100 mmHg
• Diabetic retinopathy
• Aortic dissection
• Clotting time > 9 minutes
How would you know if thrombolysis is effective? Some indications from
1. free of chest pain
2. ECG normalized
3. Early flush of cardiac enzymes
4. Reperfusion arrhythmia
Management of complications from Acute Myocardial Infarction
Left ventricular dysfunction with (see chapter on management of heart failure)
Acute pulmonary oedema – oxygenate, diuresis, GTN, ACEI
Cardiogenic shock – noradrenaline, dobutamine, IABP, PCI or CABG
Arrhythmias (see relevant chapter)
Vast majority of post MI VT and VF occur within the first 48 hours of MI.
Right ventricular infarction and dysfunction
Deserves some mention as RV infarction accompanying inferior MI is associated
with a significantly higher mortality (25 – 30 %
To diagnose: demonstrate 1 mm ST segment elevation in right precordial lead
V4R
Management:
Avoid nitrates and diuretics
Volume loading
Initiate inotropic support (dobutamine) promptly if cardiac output fails to
improve after 0.5 to 1 litre of fluid
Maintain AV synchrony – cardiovert AF
Thrombolytic therapy, PCI
Page 4 of 5
Intensive Care Unit, Prince of Wales Hospital, Chinese University of Hong Kong
Acute Coronary Symdromes
Ischaemic Discomfort
ST Elevation
No ST Elevation
Unstable Angina
Non Q-wave MI
Page 5 of 5
Q-wave MI
Q-wave MI
Non-Q-wave M