Types of Myocardial Infarction

Types of Myocardial Infarction (MI)

1. Which type of myocardial infarction is caused by plaque rupture with thrombus formation?

A. Type 1
B. Type 2
C. Type 3
D. Type 4a
✅ Answer: A. Type 1

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2. Type 2 MI is primarily caused by which of the following?

A. Coronary artery spasm only
B. Oxygen supply-demand mismatch
C. Coronary artery embolism
D. Aneurysmal rupture
✅ Answer: B. Oxygen supply-demand mismatch

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3. Which type of MI is associated with death occurring before biomarkers can be measured?

A. Type 1
B. Type 2
C. Type 3
D. Type 4b
✅ Answer: C. Type 3

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4. Myocardial infarction related to percutaneous coronary intervention (PCI) is classified as:

A. Type 1 MI
B. Type 2 MI
C. Type 4a MI
D. Type 5 MI
✅ Answer: C. Type 4a MI

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5. Type 4b MI refers to:

A. MI due to balloon angioplasty
B. MI due to stent thrombosis
C. MI during CABG
D. Spontaneous MI
✅ Answer: B. MI due to stent thrombosis

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6. Type 5 MI is associated with which procedure?

A. PCI
B. Defibrillation
C. CABG
D. Cardiac biopsy
✅ Answer: C. CABG

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7. A patient with severe anemia and no coronary thrombosis develops myocardial ischemia. This is most likely:

A. Type 1 MI
B. Type 2 MI
C. Type 3 MI
D. Type 4c MI
✅ Answer: B. Type 2 MI

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8. Which of the following is a procedure-related MI subtype?

A. Type 1
B. Type 3
C. Type 4a
D. Type 2
✅ Answer: C. Type 4a

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9. What distinguishes Type 1 from Type 2 MI?

A. Location of infarct
B. Age of patient
C. Presence of coronary atherothrombosis
D. Presence of troponin elevation
✅ Answer: C. Presence of coronary atherothrombosis

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10. Type 4c MI is due to:

A. CABG-related ischemia
B. Restenosis without thrombosis
C. Embolism in coronary arteries
D. Pulmonary embolism
✅ Answer: B. Restenosis without thrombosis

Type	Name	Description
Type 1	Spontaneous MI	Caused by acute atherothrombotic events such as plaque rupture, ulceration, or erosion with thrombus formation in a coronary artery.
Type 2	MI secondary to ischemic imbalance	Caused by a mismatch between oxygen supply and demand (e.g., tachycardia, hypotension, anemia, spasm) without acute plaque rupture.
Type 3	Sudden cardiac death MI	Cardiac death with suspected ischemia, but biomarker evidence is unavailable (e.g., death occurs before troponin levels rise or can be measured).
Type 4a	MI related to PCI	Myocardial infarction associated with percutaneous coronary intervention (PCI) (e.g., stent placement).
Type 4b	MI related to stent thrombosis	MI resulting from thrombosis of a previously implanted coronary stent, confirmed by angiography or autopsy.
Type 4c	MI related to restenosis	MI due to mechanical restenosis (narrowing) of a previously treated lesion, not due to thrombosis.
Type 5	MI related to CABG	Myocardial infarction associated with coronary artery bypass grafting (CABG) surgery.

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🔍 Notes

• Type 1 and 2 MIs are most common in clinical practice.
• Type 2 MI can be challenging to diagnose due to non-coronary causes of ischemia.
• Type 4 and 5 MIs are procedure-related and require specific biomarker and ECG criteria for diagnosis.

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1. Which of the following best characterizes Type 2 MI compared to Type 1 MI?

A. Always associated with plaque rupture
B. Occurs due to oxygen supply-demand mismatch without acute coronary thrombosis
C. Involves stent thrombosis
D. Requires CABG for diagnosis
✅ Answer: B
Explanation: Type 2 MI is due to an imbalance between myocardial oxygen supply and demand without acute plaque rupture or thrombosis, unlike Type 1 which involves atherothrombotic events.

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2. A post-operative patient develops chest pain and ST elevation 24 hours after PCI. Troponin is elevated. What type of MI is most likely?

A. Type 1
B. Type 2
C. Type 4a
D. Type 5
✅ Answer: C
Explanation: MI occurring within 48 hours of PCI with ECG changes and biomarker elevation is classified as Type 4a MI.

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3. Which of the following best defines Type 3 MI?

A. MI confirmed by high troponin without ECG changes
B. MI diagnosed only post-mortem or suspected due to clinical and ECG signs before biomarker confirmation
C. MI associated with a stent restenosis
D. MI caused by spasm of coronary artery
✅ Answer: B
Explanation: Type 3 MI is sudden cardiac death with symptoms or ECG suggestive of MI but without biomarker evidence due to rapid death.

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4. What is the major distinguishing feature of Type 4b MI?

A. Associated with coronary spasm
B. Related to PCI without complications
C. Caused by acute stent thrombosis
D. Due to bypass graft occlusion
✅ Answer: C
Explanation: Type 4b MI specifically involves thrombosis of a previously placed coronary stent, usually diagnosed via angiography or autopsy.

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5. Which of the following best describes Type 5 MI criteria?

A. Rise in troponin >10x URL within 24 hrs of CABG with new Q waves or angiographic findings
B. Any troponin rise with CABG
C. Only ECG changes post-CABG
D. MI due to thrombosis in bypass graft
✅ Answer: A
Explanation: Type 5 MI is defined as troponin elevation >10x upper reference limit (URL) within 48 hours of CABG, along with new Q waves or new graft occlusion.

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6. A patient with sepsis and no coronary disease shows elevated troponin. Which MI type is most consistent?

A. Type 1
B. Type 2
C. Type 3
D. No MI
✅ Answer: B
Explanation: Systemic conditions like sepsis can cause supply-demand mismatch, resulting in Type 2 MI without underlying coronary thrombosis.

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7. Which of the following is true about Type 4c MI?

A. It occurs after CABG
B. It is caused by stent thrombosis
C. It is due to restenosis without thrombus
D. It involves myocardial infarction without ischemia
✅ Answer: C
Explanation: Type 4c MI refers to restenosis of a previously treated lesion without associated thrombus formation.

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8. Which biomarker is essential in diagnosing all types of MI (except Type 3)?

A. BNP
B. CK-MB
C. Troponin
D. Myoglobin
✅ Answer: C
Explanation: Cardiac troponins (cTnI or cTnT) are the most specific and sensitive biomarkers used in diagnosing myocardial infarction.

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9. How does the management of Type 2 MI differ from Type 1 MI?

A. Always includes dual antiplatelet therapy
B. Focuses on correcting the underlying imbalance rather than revascularization
C. Requires emergent angiography in all cases
D. Always involves stent placement
✅ Answer: B
Explanation: Type 2 MI is typically managed by addressing the underlying cause of oxygen imbalance, not primarily by revascularization.

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10. A patient collapses during exercise. ECG shows ST elevation, but the patient dies before labs are drawn. Autopsy reveals myocardial necrosis. What type of MI is this?

A. Type 1
B. Type 2
C. Type 3
D. Type 5
✅ Answer: C
Explanation: This is classic Type 3 MI—sudden cardiac death with evidence of ischemia and necrosis before biomarkers can be measured.

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