The mechanism of "silent [myocardial] ischemia"

[E.S.Prakash]

What is the mechanism of silent ischemia? Why doesn't it result in
pain? Is it that it happen suddenly like the thrombus suddenly occlude
the coronary artery completely? Or is it because the atherosclerotic
process blocks the sensory nerve supply of the blood vessels that get
occluded?

Lim Wei Yuan
Second Year Medical Student

[E.S.Prakash]

Lim Wei Yuan: 

Silent (myocardial) ischemia is diagnosed when there is objective evidence of myocardial ischemia in the form of ECG changes suggestive of myocardial ischemia, raised troponin levels but without angina pectoris (chest pain) or equivalents of angina (such as breathlessness). 

Proposed mechanisms of silent ischemia include higher pain threshold, autonomic neuropathy, an excess of endogenous endorphins. 

See http://clinical.diabetesjournals.org/content/21/1/5.full

E.S.Prakash

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[E.S.Prakash]

According to an article [1], silent ischemia is probably due to
abnormal central processing of pain signals from the heart. The
"activation" of various parts of MI patients' brains is recorded by
observing regional blood flow changes of brain during myocardial
ischemia. The researchers think silent ischemia isn't caused by
peripheral nerve dysfunction because both thalami of silent ischemia
patients are activated during MI. Comparing with normal myocardia
ischemia patients, patients with silent ischemia were having
incomplete frontal cortical activation, this might affect their
perception of pain.

Below is the link to the article [1] http://www.annals.org/content/124/11/939.abstract

Please correct me if I am wrong. Thank you.

Chan Zi Yin
MBBS Batch 14
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