Myocardial Ischemia

Question 1

What is myocardial ischemia?

Answer 1

Myocardial ischemia occurs when myocardial oxygen requirements exceed myocardial oxygen supply.

Question 2

What is myocardial infarction?

Answer 2

Myocardial infarction is myocardial necrosis in the clinical setting of ischemia.

Question 3

What are the clinical features of myocardial ischemia?

Answer 3

1. Asymptomatic (especially if under general anesthesia)
2. Symptoms - angina, dypsnea, diaphoresis, nausea, syncope, altered mental status
3. Hypertension, hypotension
4. ECG changes (ST-T changes, new LBBB, arrhythmias)
5. Echocardiography - new regional wall motion abnormality
6. Blood tests - elevated troponin I or T

Question 4

What is the differential diagnosis when clinical features are suspicious for myocardial ischemia?

Answer 4

1. Cardiac
   - plaque rupture causing partial or complete coronary artery occlusion
   - due to increased O2 demand or decreased supply (spasm, embolism, anemia, arrhythmia, HTN, HoTN)
2. Other cardiac - Ao dissection, pericarditis
3. Chest wall trauma
4. Pulmonary embolism
5. Severe asthma
6. Esophagitis

Question 5

What is the management of myocardial ischemia/infarction?

Answer 5

1. Assess need for airway management and initiation of CPR
2. If during surgery, consider risk/benefit of aborting procedure
3. Restore coronary oxygen supply by supplemental O2, treat anemia, optimize blood pressure, optimize HR/rhythm
4. Decrease coronary O2 demand using analgesia, nitrates, beta-blockers.
5. Monitor ECG, consider invasive monitors
6. Consider ASA/anticoagulants if appropriate
7. Cardiology consultation re: thrombolytic therapy,coronary angiography/angioplasty, emergency cardiac surgery
8. Postcardiac arrest - therapeutic hypothermia

Question 6

What measures can one use to restore coronary oxygen supply during myocardial ischemia infarction?

Answer 6

supplemental O2
treat anemia
optimize blood pressure, HR, rhythm

Question 7

What measures can one use to decrease coronary oxygen demand during myocardial ischemia infarction?

Answer 7

Analgesia
Nitrates
Beta-blockers
Optimize blood pressure, heart rate/rhythm

Question 8

What might a cardiology consultation offer for perioperative treatment of MI?

Answer 8

Thrombolytic therapy
Coronary angiography/angioplasty
Referral for emergency cardiac surgery