MI complications

Question 1

quickly outline the main complications of MI

[death passing praaed close]

Answer 1

death

pump failure

pericarditis

rupture: myomaalcia cordis

arrhythmia

aneurysm

systemic embolism

dressler’s syndrome:pleuro-pericarditis

Question 2

death

Answer 2

VF, LVF, CVA causing cardiac arrest

Cardiac arrest

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.

Cardiogenic shock

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

pericarditis

Answer 3

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.

Features

• chest pain: may be pleuritic. Is often relieved by sitting forwards
• other symptoms include non-productive cough, dyspnoea and flu-like symptoms
• pericardial rub
• tachypnoea
• tachycardia

Causes

• viral infections (Coxsackie)
• tuberculosis
• uraemia (causes ‘fibrinous’ pericarditis)
• trauma
• post-myocardial infarction, Dressler’s syndrome
• connective tissue disease
• hypothyroidism

ECG changes

widespread ‘saddle-shaped’ ST elevation

PR depression: most specific ECG marker for pericarditis

Rx:

1. NSAIDS- ibuprofen
2. and/or echo to exclude effusion

Question 4

rupture: myomalaxia cordis

Answer 4

Left ventricular free wall rupture

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.

Ventricular septal defect

• Rupture of the interventricular septum usually occurs in the first week
• seen in around 1-2% of patients.
• Features: acute heart failure 9eg. raised JVP) associated with a PSM
• An echocardiogram is diagnostic and will exclude acute MR which presents in a similar fashion.
• Urgent surgical correction is needed.

Acute mitral regurgitation

• 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.

Question 5

arrhythmias

Answer 5

Tachyarrhythmias
SVT :

• sinus tachy- give o2 and analgesia
• AF or atrial flutter: (compromised= DC cardioversion; otherwise rate control= digoxin + Bb)

Ventricular:
VF, is the most common cause of death following a MI.

• compromised = DC cardioversion
• else= amiodarone
• may need pacing

Other common arrhythmias including VT

• early <48hrs= reperfusion = good prog
• late >48hrs= extensive heart damage
• rx: DC shock

Bradyarrhythmias

1. Atrioventricular block is more common following inferior myocardial infarctions.= rx: pace mobitz II [has high risk of suddenly developing AVblock]

2. sinus brady [esp in inf MI] rx: atropine
3. ventricular brady [suggests SA + AV node damage]

Question 6

Left ventricular aneurysm

Answer 6

LONG TERM COMPLICATION! OCCURS LATER, 4-6 WEEKS POST MI

The ischaemic damage sustained may weaken the myocardium resulting in aneurysm formation.

s/s:

• LVF
• angina
• recurrent VT
• systemic emboli

ECG: persistent ST elevation and left ventricular failure.

Thrombus may form within the aneurysm increasing the risk of stroke.

Patients are therefore anticoagulated.

Question 7

systemic emboli

Answer 7

arise from LV mural thrombosis

consider warfarin for 3mo after large anterior MI

risk of DVT + PE ===> pt’s prophalactically heparinized till fully mobile.

Question 8

Dressler’s syndrome

Answer 8

ANOTHER LONG TERM COMPLICATION!

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 [recurrent pericarditis
• raised ESR.

It is treated with NSAIDs. steroids if severe.

Question 9

Chronic heart failure

Answer 9

As described above, 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.