Unveiling electrocardiographic mysteries

Abstract

I read with interest the letter from Dewilde and Desmet [1] on mysterious electrocardiographic arrhythmia in an old woman presenting irregular heart rhythm, characterized by idioventricular rhythmic bigeminy with left bundle branch block pattern, and cardiac dysfunction underlying severe hyperkalemia. Hyperkalemia has been known for a long time to be associated to abnormal impulse formation manifested by either acceleration of normal pacemaker or emergence of ectopic pacemakers [2] in atria and ventricles. In limited series studies, conduction disturbances presenting with right bundle branch block (roughly 25% prevalence) are slightly more prevalent than left bundle branch block (17% prevalence) [3–5]. Impulse formation and conduction may co-exist among electrocardiographic findings of hyperkalemia [3,6], determining junctional rhythm with bundle branch block pattern. However, association of abnormal idioventricular rhythm and overt heart failure represents a medical emergency [6], making cardiac life support mandatory on presentation, and perhaps retarding a more accurate diagnostic procedure. Additionally, association of angiotensin II blockers and potassium-sparing diuretics increases the risk of hyperkalemia [7], especially in elderly due to age-related depressed renal function. Finally, disopyramide has been known to be a potent cardiac depressant [8] with negative dromotropic effect and administration to patients with left ventricular systolic dysfunction must be made with extreme caution [8]. In