Myocardial Infarction Flashcards
How does a Myocardial Infarction present?
- Central Crushing chest pain
- Radiation to shoulder
- Sweaty
- Vomiting
How are patient managed presenting with symptoms of MI when <12hrs, 12-72hrs, and >72 hrs?
<12 hours: Emergency Admission
12-72hrs: Refer to hospital for same day assessment if between
>72hrs: Perform a full assessment with ECG and troponin measure before deciding on further action
What are examination finding of an MI?
Hands
- Check pulse rate, Nicotine staining fingers, Check blood pressure
Face and Neck
- JVP may be raised in cardiac failure or right ventricular infarction
- Look for Arcus Senilis and Xanthelasma in eyes
Auscultation
- Fourth heart sound
- Pericardial rub
- Pansystolic murmur of papillary muscle dysfunction
- Chest for crackles and pleural effusion
Abdomen and Legs
- Abdomen for tender liver of cardiac failure
- Check legs for DVT and Peripheral Pulses
What are investigations for a Myocardial Infarction?
- ECG within 10 minutes of admittance
- Check the troponin levels with blood tests
What is the immediate management of an MI?
- Aspirin 300 mg
- Clopidogrel/Ticagrelor
- Unfractionated heparin if PCI
- Oxygen given only if hypoxic. Different requirement for people with COPD
- Nitrates can be given to relieve ischaemic pain
- Slow IV morphine can be given with metoclopramide hydrochloride
What is the definitive management of an MI?
- PCI is the gold standard. Use of glycoprotein 2b/2a inhibitor
- If no access to PCI within 120 minutes then thrombolytic drugs can be given. LMWH heparin should be given with this.
Which trhombolytc drugs can be given?
Tenecteplase
What has to be done following Thrombolysis?
An ECG should be performed 90 minutes following thrombolysis to assess greater than 50% resolution in the ST elevation
- If there has not been adequate resolution then rescue PCI is superior to repeat thrombolysis
- For patients successfully treated with thrombolysis, PCI has been shown to be beneficial. The optimal timing of this is still under investigation
What are ECG changes required to attempt PCI or thrombolysis?
- ST elevation of > 2mm (2 small squares) in 2 or more consecutive anterior leads (V1-V6) OR
- ST elevation of greater than 1mm (1 small square) in greater than 2 consecutive inferior leads (II, III, avF, avL) OR
- New Left bundle branch block
What is the longer term management of patients who have been treated for MI?
- Aspirin with Clopidogrel (warfarin used if not tolerated)
- Beta blockers
- Statins
- ACE inhibitors (ang2 receptor antagonists)
- Nitrates for angina
- Epleronone in those with LVD and evidence of heart failure
How are diabetics with Myocardial Infarctions managed?
- Recommend using dose-adjusted insulin infusion with regular monitoring of blood glucose level to glucose below 11.0 mmol/l
- Intensive insulin therapy regimes not recommended routinely
Which artery is affected when V1-V4 show ECG changes in an MI?
Anteroseptal
- Left anterior descending artery
Which artery is affected when leads II, III, aVF show ECG changes in an MI?
Inferior MI
- Right coronary
Which artery is affected when leads V4-6, I, aVL show ECG changes in an MI?
Anterolateral
- Left anterior descending artery or
- Left circumflex artery
Which artery is affected when leads I, aVL +/- V5-6 show ECG changes in an MI?
Lateral
- Left circumflex artery
Which artery is affected when leads Tall R waves V1-2 show ECG changes in an MI?
Posterior
- Left circumflex, also
- Right coronary (causes ST depression)
What are examples of complications of Myocardial infarctions?
- Cardiac arrest
- Acute mitral regurgitation
- Cardiogenic shock
- Chronic heart failure
- Tachyarrhythmias
- Bradyarrhythmias
- Pericarditis
- Left ventricular aneurysm
- Left ventricular free wall rupture
- Ventricular septal defect
What some reversible causes of Cardiac Arrest?
These can be remembered by the 4Hs and 4Ts:
- Hypothermia
- Hypoxia
- Hypovolaemia
- Hypokalaemia /hyperkalaemia / hypoglycaemia
- Tension pneumothorax
- Toxins
- Tamponade
- Thrombosis
How does Cardiac Arrest occur post MI?
- Most commonly occurs due to patients developing Ventricular Fibrillation and is the most common cause of death following a MI.
- Patients are managed as per the ALS protocol with defibrillation.
How does Cardiogenic shock occur post MI and how is it treated?
- Large part of the ventricular myocardium is damaged in the infarction so ejection fraction of the heart may decrease to the point that the patient develops cardiogenic shock. This is difficult to treat.
- Other causes of cardiogenic shock include the ‘mechanical’ complications such as left ventricular free wall rupture as listed below.
- Patients may require inotropic support and/or an intra-aortic balloon pump.
How does Chronic Heart Failure occur post MI and how is it treated?
- Patient survives the acute phase but their ventricular myocardium may be dysfunctional resulting in chronic heart failure.
- Loop diuretics such as Furosemide will decrease fluid overload.
- Both ACE-inhibitors and beta-blockers have been shown to improve the long-term prognosis of patients with chronic heart failure.
How do Tachyarrythmias occur post MI and how is it treated?
- Ventricular fibrillation is the most common cause of death following a MI.
- Other common arrhythmias including ventricular tachycardia.
Treated with DC shock
How do Bradyarrythmias occur post MI?
Atrioventricular block is more common following inferior myocardial infarctions.
What are syndromes of pericarditis that can occur post MI?
- Acute Pericarditis in the first 48 hours
- Dressler’s syndrome tends to occur around 2-6 weeks following a MI.
How does a left ventricular aneurysm occur post MI and how is it treated?
- The ischaemic damage sustained may weaken the myocardium resulting in aneurysm formation.
- Associated with persistent ST elevation and left ventricular failure.
- Thrombus may form within the aneurysm increasing the risk of stroke. Patients are therefore anticoagulated.
How does Pericarditis occur post MI and how is it treated?
- Acute pericarditis follow a transmural MI is common (c. 10% of patients).
- The pain is typical for pericarditis (worse on lying flat etc), a pericardial rub may be heard, and a pericardial effusion may be demonstrated with an echocardiogram.
- The underlying pathophysiology of Dressler’s syndrome is thought to be an autoimmune reaction against antigenic proteins formed as the myocardium recovers. It is characterised by a combination of fever, pleuritic pain, pericardial effusion and a raised ESR. It is treated with NSAIDs.
How does Left ventricular wall rupture occur post MI and how is it treated?
- Seen in around 3% of MIs and occurs around 1-2 weeks afterwards.
- Patients present with acute heart failure secondary to Cardiac Tamponade (raised JVP, pulsus paradoxus, diminished heart sounds).
- Urgent Pericardiocentesis and Thoracotomy are required.
How does Ventricular Septal Defect occur post MI and how is it treated?
- Rupture of the interventricular septum usually occurs in the first week and is seen in around 1-2% of patients.
- Features: Acute heart failure associated with a pan-systolic murmur.
- An echocardiogram is diagnostic and will exclude acute mitral regurgitation which presents in a similar fashion. Urgent surgical correction is needed.
How does Acute Mitral Regurgitation occur post MI and how is it treated?
- More common with infero-posterior infarction and may be due to ischaemia or rupture of the papillary muscle.
- Early-to-mid systolic murmur is typically heard.
- Patients are treated with vasodilator therapy but often require emergency surgical repair.
