Myocardial infarction: complications

Question 1

Cardiac arrest?

Answer 1

• This 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.

Question 2

Cardiogenic shock?

Answer 2

• If a large part of the ventricular myocardium is damaged in the infarction the 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.

Question 3

Chronic heart failure?

Answer 3

• If the patient survives the acute phase 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.

Question 4

Tachyarrhythmias?

Answer 4

• Ventricular fibrillation, as mentioned above, is the most common cause of death following a MI.
• Other common arrhythmias including ventricular tachycardia.

Question 5

Bradyarrhythmias?

Answer 5

• Atrioventricular block is more common following inferior myocardial infarctions.

Question 6

Pericarditis?

Answer 6

• Pericarditis in the first 48 hours following 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.
• Dressler’s syndrome tends to occur around 2-6 weeks following a MI.
• The underlying pathophysiology 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.

Question 7

Left ventricular aneurysm?

Answer 7

• The ischaemic damage sustained may weaken the myocardium resulting in aneurysm formation.
• This is typically associated with persistent ST elevation and left ventricular failure.
• Thrombus may form within the aneurysm increasing the risk of stroke. Patients are therefore anticoagulated.

Question 8

Left ventricular free wall rupture?

Answer 8

• This is 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.

Question 9

Ventricular septal defect?

Answer 9

• 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.

Question 10

Acute mitral regurgitation?

Answer 10

• More common with infero-posterior infarction and may be due to ischaemia or rupture of the papillary muscle.
• An early-to-mid systolic murmur is typically heard. Patients are treated with vasodilator therapy but often require emergency surgical repair.