Myocardial disease : Ischemia and infarction
- 1. Stunned and Hibernating myocardium
- Both stunned and hibernating myocardium represent dysfunctional but still viable myocardium
- a) Stunned myocardium
- “Myocardial stunning” occurs when myocardium exhibits persistent contractile dysfunction after an episode of ischemia, despite restoration of normal perfusion.
- Perfusion (O), Wall motion (X)
- A transient phenomenon that is followed by full functional recovery, usually after no more than several hours.
- b) Hibernating myocardium
- The result of chronically reduced resting perfusion, which can be reversed with restoration of adequate perfusion.
- Perfusion (X), Wall motion (X)
- a) Stunned myocardium
- Both stunned and hibernating myocardium represent dysfunctional but still viable myocardium
2. Myocardial infarction
a) Delayed contrast enhancement on MRI
– 10 to 15 mins after administration of gadolinium ➜ Inversion recovery (T1 time x 0.69) ➜ signal nulling of normal myocardium
– Enhancing portion = Infarcted myocardium (bright is dead)
– Dark signal area inside of enhancing portion = No-reflow zone ; *microvascular obstruction (MVO) ➜ Poor prognosis
– Contrast material in acute intracellular area
b) T2WI
– high signal instensity area = edema or peri-infarct area
What is the mechanism of delayed enhancement in acute myocardial infarction?
Myocyte membrane rupture ➜ Passive diffusion of contrast material into the intracellular space ➜ increased tissue-level contrast agent concentration ➜ delayed hyperenhancement
2-1) Acute myocardial infarction
– Positive remodeling, no wall thinning
– Due to edema DCE area is exaggerated more than myocardial infarction area
– Native T1 value increased (edema)
– “No reflow” zone (microvascular obstruction
2-2) Chronic myocardial infarction
– Increased insterstitial space between collagen fibers in scar tissue
– Wall thinning due to fibrosis or scarring
– Fat deposit
– The margin becomes clearer as it progresses to chronicity, more accurately matching the area of myocardial infarction.
– Contrast material in insterstitial space
Note that dark signal area exists inside of enhancing portion indicates microvascular obstruction(MVO).
Image from radiologyassisstant
suggestive acute myocardial infarction.
Transmural infarction.
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