Complications of MI

Question 1

How does cardiac arrest arise due to MI?

Answer 1

• Most commonly occurs due to patients developing ventricular fibrillation
• Most common cause of death following a MI
• Patients are managed as per the ALS protocol with defibrillation.

Question 2

How does cardiogenic shock arise due to MI?

Answer 2

• If a large part of the ventricular myocardium is damaged the ejection fraction of the heart may decrease ==> cardiogenic shock
• Difficult to treat.
• Other causes of cardiogenic shock include the ‘mechanical’ complications such as left ventricular free wall rupture
• Patients may require inotropic support and/or an intra-aortic balloon pump.

Question 3

How does CHF arise from MI?

Answer 3

• If the patient survives the acute phase their ventricular myocardium may be dysfunctional resulting in CHF

Question 4

How do tachyarrhythmias arise due to MI?

Answer 4

• Ventricular fibrillation is the most common cause of death following a MI
• Other common arrhythmias including ventricular tachycardia

Question 5

How do bradyarrhythmias arise due to MI?

Answer 5

Atrioventricular block is more common following inferior myocardial infarctions

Question 6

How does pericarditis arise from MI?

Answer 6

• Pericarditis in the first 48 hours following a transmural MI is common (c. 10% of patients).
• Dressler’s syndrome tends to occur around 2-6 weeks following a MI:
  
  • Autoimmune reaction against antigenic proteins formed as the myocardium recovers
  • Combination of fever, pleuritic pain, pericardial effusion and a raised ESR.
  • Treated with NSAIDs.

Question 7

How does a left ventricular aneurysm occur?

Answer 7

• 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.

Question 8

How does left ventricular free wall rupture arise due to MI?

Answer 8

• Seen in around 3% of MIs and occurs around 1-2 weeks afterwards
• Patients present with AHF secondary to cardiac tamponade (raised JVP, pulsus paradoxus, diminished heart sounds)
• Urgent pericardiocentesis and thoracotomy are required

Question 9

How does ventricular septal defect occur due to MI?

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 ECHO is diagnostic and will exclude acute mitral regurgitation which presents in a similar fashio
• Urgent surgical correction is needed.

Question 10

How does acute mitral regurgitation occur due to MI?

Answer 10

• More common with infero-posterior infarction and may be due to ischaemia or rupture of the papillary muscle
• Features: Acute hypotension and pulmonary oedema
• An early-to-mid systolic murmur is typically heard
• Treated with vasodilator therapy but often require emergency surgical repair

Question 11

What drugs should patients be offered after an MI?

Answer 11

• Dual antiplatelet therapy (aspirin plus a second antiplatelet agent)
• ACE inhibitor
• Beta-blocker
• Statin

Question 12

What is the lifestyle advice given to patients following an MI?

Answer 12

• Diet: advise a Mediterranean style diet, switch butter and cheese for plant oil based products. Do not recommend omega-3 supplements or eating oily fish
• Exercise: advise 20-30 mins a day until patients are ‘slightly breathless’
• Sexual activity may resume 4 weeks after an uncomplicated MI.
• Reassure patients that sex does not increase their likelihood of a further MI. PDE5 inhibitors (e.g, sildenafil) may be used 6 months after a MI.
• They should however be avoided in patient prescribed either nitrates or nicorandil

Question 13

When are aldosterone antagonists used post-STEMI?

Answer 13

• Patients who have had an acute MI and who have symptoms and/or signs of:
  
  • heart failure
  • Left ventricular systolic dysfunction
• Treatment with an aldosterone antagonist licensed for post-MI treatment (e.g. eplerenone) should be initiated within 3-14 days of the MI, preferably after ACE inhibitor therapy

Question 14

When are patients thrombolysed in STEMI?

Answer 14

• Primary percutaneous coronary intervention (PCI) has emerged as the gold-standard treatment for STEMI but is not available in all centres
• Thrombolysis should be performed in patients without access to primary PCI.

Question 15

What thrombolytic agents should be used in STEMI patients?

Answer 15

1. Tissue plasminogen activator (tPA) has been shown to offer clear mortality benefits over streptokinase
2. Yenecteplase is easier to administer and has been shown to have non-inferior efficacy to alteplase with a similar adverse effect profile

Question 16

What should be done post-thrombolysis after an STEMI?

Answer 16

An ECG should be performed 90 minutes following thrombolysis to assess whether there has been a greater than 50% resolution in the ST elevation:

• NO adequate resolution = rescue PCI is superior to repeat thrombolysis
• Adequate resolution = PCI has been shown to be beneficial. The optimal timing of this is still under investigation

Question 17

What is NICE’s guidelines for hyperglyceamic ACS?

Answer 17

• Recommends using a dose-adjusted insulin infusion with regular monitoring of blood glucose levels to glucose below 11.0 mmol/l
• Intensive insulin therapy (an intravenous infusion of insulin and glucose with or without potassium, sometimes referred to as ‘DIGAMI’) regimes are not recommended routinely