Acute Inferior Infarct – L Circumflex Occlusion

Report:

Sinus tachycardia 112/min

Acute inferolateral infarction

Comment:

This trace has three major criteria favouring left circumflex artery over RCA as the culprit vessel.

The reciprocal changes in aVL but not in 1 denote the left circumflex as the culprit artery. In RCA blocks, both 1 and aVL show reciprocal changes. Reciprocal ST segment depression in both V1 and V2 is also typical, but less diagnostic. Elevation in V1 is, on the other hand, diagnostic of RCA occlusion as the cause of inferior (and, in that case, right ventricular) infarction: there is no need for V4R if ST is elevated in V1 and depressed in V2. A new criterion, ST depression in aVR > 0.5 mm, strongly suggests circumflex occlusion74.

About 80% of inferior infarcts are due to RCA blocks. For urgent PTCA it is of value to know which artery to open first (or exclusively) in patients with combined circumflex/RCA disease. Stenting a chronic lesion may do nothing for the acutely infarcted myocardium.

Below (Fig 99a) is a later trace, taken at 34oC. It shows an atrial rhythm 40/min, with modest hypothermic humps and markedly prolonged QTc (0.54”). There is no tremor. The patient could be among 10% whose ECGs do not show muscle tremor in hypothermia. Alternatively, he could be brain dead already, but then the rate should be somewhat faster, since brain death takes away the vagal nuclei in the brainstem. In this case, neither: I paralysed him by vecuronium specifically to prevent shivering. Needless to say, the patient has to be adequately sedated for this – to preserve the myocardium as well as for for ethical reasons that should be obvious.