Introduction
An obstructive lesion of the left main coronary artery (LMCA) has
typically been described on the electrocardiogram (ECG) as a generalised
ST segment depression (SST) (maximum in V4-V6) associated with inverted
T waves in the same leads and elevation. of the SST in aVR1. Likewise, elevated SST in aVR is associated with
multivessel coronary artery disease 1. The presence of
these findings, together with an adequate clinical correlation, should
alert medical personnel to promptly rule out these conditions and
prevent possible adverse outcomes.
However, these electrocardiographic changes are not 100% specific for
an obstructive lesion of the LMCA, since elevated SST in AVR could be
observed in multivessel coronary disease (three or more vessels),
occlusion of the proximal segment of the anterior descending artery, and
diffuse subendocardial ischemia 2.
Regarding the pathophysiology of hypokalemia, at the level of the
cardiomyocytes, an increase in the resting membrane potential is
generated, and the duration of the action potential and the refractory
period increase. Changes that are potentially arrhythmogenic, such as ST
segment depression, T wave flattening, and prominent U waves, which have
been described as a “hallmark” of hypokalemia 3.
However, an elevation of the SST in AVR simulating an LMCA lesion is a
rare finding within the electrocardiographic alterations described in
hypokalemia, which include: premature atrial and ventricular complexes,
sinus bradycardia, prolonged QTc, junctional tachycardia, AV block,
ventricular tachyarrhythmias, as well as SST depression, with a decrease
in the amplitude and inversion of the T wave and an increase in the
amplitude of the U wave, usually from V4 to V6 4.
Below, we describe a clinical case of severe hypokalemia simulating on
an ECG an obstructive lesion pattern of the LMCA.