- 下壁梗塞佔了所有 MI 的40-50%
- 40% 下壁梗塞合併 RV infarction
- 20% 下壁梗塞合併 bradycardia due to 2 or 3 degree AV block
- STE or Q over leads II, III and aVF
Reciprocal STD in aVL (± lead I) ( 下外下, 前下 )
下壁梗塞 can result from occlusion of
all 3 coronary arteries :
- RCA : 80%, lead III > lead II
- LCx : 18% , STE in the lateral leads I and V5-6 ( 較合併側壁 )
- Wraparound ( 前 +下 ) : 較少見
* RCA occlusion :
- STE in lead III > lead II
- Presence of reciprocal STD in lead I
- Signs of RV infarction: STE in V1 and V4R
* Circumflex occlusion :
- STE in lead II = lead III
- Absence of reciprocal ST depression in lead I
- Signs of lateral infarction -
STE in the lateral leads I and aVL or V5-6
Massive inferolateral STEMI :
- Marked STE in II, III and aVF with a tombstone morphology.
- Reciprocal change in aVL.
- STE is also present in the lateral leads V5-6,
indicating an extensive infarct of the inferior and lateral walls.
Inferior leads hyperacute T waves with "T wave inversion in aVL"
which is a clue suggestive of RCA occlusion.
Inferior hyperacute T-waves. The clue is T-wave inversion in aVL.
其實就是 RCA 的下壁梗塞
比較會在 aVL 有 reciprocal change
20% 下壁梗塞合併 bradycardia
due to 2 or 3 degree AV block, may also manifest signs of sinus node dysfunction
Bradyarrhythmias and AV block in the context of inferior STEMI
are usually transient (lasting hours to days)
respond well to atropine and do not require permanent pacing.
原因 :
- Ischaemia of the AV node : impaired blood flow via the AV nodal artery.
This artery arises from the RCA 80% of the time
- Bezold-Jarisch reflex = increased vagal tone secondary to ischaemia.
RV infarction
- Isolated RV infarction is extremely uncommon.
- 40% 下壁梗塞合併 RV infarction
- Poor RV contractility -> preload sensitive
and can develop severe hypotension in response to nitrates
* The first step to spotting RV infarction is
to suspect it… in all patients with inferior STEMI! *
* 一些懷疑 RV infarction 的 hints :
- STE in V1 – the only standard ECG lead that looks directly at RV
- STE in lead III > II
- STE in V1 > V2
- STE in V1 + STD in V2 (highly specific for RV MI)
Isoelectric ST segment in V1 with marked ST depression in V2.
The most useful lead is V4R ~
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