The relationship between blood calcium levels and clinical success of diltiazem used in atrial fibrillation/flutter rate control and treatment of other supraventricular tachycardias in emergency department

Diltiazem is an anti-arrhythmic drug widely used in the treatment of narrow QRS complex tachycardias and decreases the cytosolic calcium level by inhibiting the calcium influx from the extracellular space into the cell with L-type calcium channel blockade. The relationship between the effectiveness of iv diltiazem and serum calcium is a subject that has not been investigated in vivo. The first aim of this study was to investigate the relationship between the efficacy of iv diltiazem and blood calcium levels, and the second was to determine the effects of diltiazem used in rate control prophylaxis on blood calcium levels. The data of 383 patients who applied to the emergency department with narrow QRS complex tachycardia were evaluated retrospectively. The median age of the patients was 74. 55% of the patients were female and 45% male. The pre-treatment rhythm was AF in 91.1%, atrial flutter in 2.9%, and other SVT rhythms in 6.0% of patients. The treatment success rate was 68.9%. The median of ionized calcium values was 1.14 mmol/L (IQR: 0.12) in patients who responded to diltiazem treatment, and 1.10 mmol/L (IQR: 0.12) in patients who did not, but it was not statistically significant (p=0.298). In subgroup analyzes, treatment success was 63.1% in patients with low ionized calcium, 73.3% in patients with normal value of ionized calcium, and 40% in patients with high ionized calcium, and this difference was significant (p=0.002). The highest success rate with diltiazem was seen in patients with ionized calcium within normal limits. The median serum ionized calcium levels were 1.17 mmol/L (IQR:0.11) in patients using prophylactic CCBs, and 1.12 mmol/L (IQR:0.15) in non-users, and the difference was significant (p=0.009). This information can guide clinicians in the selection of drugs for the treatment of patients who present to the emergency department with narrow QRS complex tachycardia and whose serum calcium levels have changed.