Electrocardiographic QRS Axis Shift With Left Anterior Hemiblock

To the Editor.—  This is, indeed, an interesting case. On two occasions their patient had normal conduction in the presence of hyperkalemia and abnormal or slowed conduction through the left anterior-superior division of the left bundle branch resulting in left axis deviation, with normal potassium levels. Later, this same patient showed left axis deviation with hyperkalemia that became normal following dialysis.There is a physiologic basis for decrease conduction with hyperkalemia,¹ and yet on occasion their patient had abnormal conduction through the left anterior superior division of the left bundle (LAH) with normal potassium levels. They conclude that there might be metabolic factors other than hyperkalemia that may account for the conduction delay.The ECGs with left axis deviation occurred when the heart rates were faster. Rate-related bundle branch block is well known,² and rate-related LAH is known to occur (Rosenbaum et al, 1969). A possible explanation for