Myocardial infarction complications

Question 1

What is the most common cause of death post MI and why does it occur?

Answer 1

Cardiac arrest due to patients developing vent fib

Patients managed as per the ALS protocol with defib

Question 2

Why can a patient develop cardiogenic shock post MI?

Answer 2

1. 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.
2. Difficult to treat
3. Other causes of cardiogenic shock include the ‘mechanical’ complications such as left ventricular free wall rupture
4. Patients may require inotropic support and/or an intra-aortic balloon pump.

Question 3

Why can a patient develop chronic heart failure post MI and how can this be managed?

Answer 3

1. If the patient survives the acute phase their ventricular myocardium may be dysfunctional resulting in chronic heart failure.
2. Loop diuretics such as furosemide will decrease fluid overload.
3. Both ACE-inhibitors and beta-blockers have been shown to improve the long-term prognosis of patients with chronic heart failure.

Question 4

What arrhythmic abnormalities may occur post MI?

Answer 4

Tachyarrhythmias :- vent fib most common (80% within 12 hrs). Rx: DC shock
Vent tachy is another common arrythmia

Bradyarrhythmias - AV block is more common following inferior MI.

Question 5

What is the common timeframe for pericarditis to occur post transmural MI?

Answer 5

First 48 hrs (in 10% of patients)

Question 6

How may pericarditis present post MI?

Answer 6

Pain typical of pericarditis - worse on lying flat etc

Pericardial rub may be heard

Pericardial effusion may be demonstrated with an echocardiogram.

ECG: saddle shaped ST elevation

Treatment - NSAIDs

Question 7

What is Dressler’s syndrome and what is the underlying pathophysiology?

Answer 7

1. Dressler’s syndrome tends to occur around 2-6 weeks following a MI.
2. It is characterised by a combination of fever, pleuritic pain, pericardial effusion and a raised ESR.
3. It is treated with NSAIDs; steroids if severe
4. The underlying pathophysiology is thought to be an autoimmune reaction against antigenic proteins formed as the myocardium recovers.

Question 8

Why does left vent aneurysm develop post MI?

Answer 8

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 9

How does a patient with left vent aneurysm present and when do they classically present post MI?

Answer 9

Occurs late (4-6 weeks post MI)

Presents with LVF, angina, recurrent VT or systemic embolism

ECG: persistent ST segment elevation

Treatment: anticoagulate, consider excision

Question 10

How does a patient with left vent free wall rupture present and when do they classically present post MI?

Answer 10

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 11

A patient presents with acute heart failure associated with a pan-systolic murmur, 1 week after their MI. Diagnosis?

Answer 11

Ventricular septal defect due to rupture of the interventricular septum.

Also raised JVP

Echo is diagnostic and will exclude acute mitral regurg

Urgent surgical correction

Question 12

How does acute mitral regurgitation present post MI? Whats the DDx?

Answer 12

More common with infero posterior infarcts and may be due to ischaemia or rupture of papillary muscle.

Presentation - pulmonary oedema

Early to mid diastolic murmur

Pts treated with vasodilator therapy but often require emergency surgical repair

DDx- VSD due to rupture of interventricular septum

Question 13

How does RVF present post MI?

Answer 13

Low CO and raised JVP

Fluid is key; avoid vasodilators (e.g. nitrates) and inotropes

Question 14

What are the salient features in the presentation of a cardiac tamponade?

Answer 14

1. Low cardiac output
2. Pulsus paradoxus => drop in BP with inspiration
3. Kussmaul’s sign => JVP rises with inspiration
4. Muffled heart sounds

Diagnosis: Echo

Treatment: pericardial aspiration (provides temporary relief); surgery

Question 15

What is the role of aldosterone antagonists like eplerenone post MI?

Answer 15

Acute MI + symptoms and/or signs of HF and left ventricular systolic dysfunction = treatment with an aldosterone antagonist (e.g. eplerenone)

Should be initiated within 3-14 days of the MI, preferably after ACE inhibitor therapy