Mild hyperkalaemia does not typically cause cardiac symptoms. However, for an elderly patient on atrio-ventricular (AV) nodal blocker, even mild hyperkalaemia may result in disastrous outcome. We report a case of persistent bradyarrythmia caused by iatrogenic hyperkalaemia in a patient who had concomitant use of AV nodal medication. An 81-year-old lady with multiple comorbidities and a long list of medications presented with symptomatic bradyarrhythmia. She, in fact, had two AV nodal blockers in her prescription, a beta-blocker and amiodarone. Her potassium level was found to be mildly elevated due to acute renal failure. She remained bradycardic despite initial treatment and was subsequently dependant on intravenous isoproterenol until her renal function improved. This case highlights the different threshold for manifestation of hyperkalaemic symptoms in a growing group of patients: elderly patients with multiple comorbidities and polypharmacy.

Current selection guideline for CRT uses broad QRS duration (>120 ms) as a marker for ventricular dyssynchrony. However, more recent data supports mechanical marker specifically measured by Tissue Doppler Imaging (TDI) as a better criterion to predict response to CRT. Sixty seven patients with significant left ventricular dysfunction (EF less than 40%) and narrow QRS complex were prospectively enrolled. They underwent Tissue Doppler Imaging (TDI) study to evaluate intraventricular mechanical dyssynchrony. Dyssynchrony index which is defined as standard deviation of time to peak systolic velocity in twelve ventricular segments was measured. A value greater than 32.6 is taken to reflect significant ventricular dyssynchrony. Overall 38 patients (56.7%) demonstrated significant dyssynchrony. There was no significant correlation between QRS duration and the Ts-SD-12 (r = 0.14, p = 0.11). Ventricular mechanical dyssynchrony is common in patients with normal QRS duration. Therefore, QRS duration alone will miss a substantial proportion of suitable patients for CRT and therefore deny them this adjunct therapy. We propose echocardiographic parameters, specifically TDI, to be included in patient selection criteria for CRT.