Background:  Cardiac arrhythmias are considered as one of the most important causes of mortality in patients on hemodialysis. Arrhythmias frequently occur in patients with chronic renal failure on regular hemodialysis with reported incidences varying from 30–48% of patients. These abnormalities can span from supraventricular to severe ventricular arrhythmia. There is an increased frequency of occurrence and clustering of arrhythmias around the dialysis time. Aim of the study: To detect the difference between acetate and bicarbonate dialysis as regard to the type and frequency of arrhythmia in those patients. Study design: This study was done on 20 male patients age 51–73, all have history of heart disease. Patients were divided into 2 equal groups using acetate in group 1 and bicarbonate in group 2. All patients were on regular hemodialysis (4 hours, thrice weekly). Careful history and clinical examination were done. Pre‐dialysis investigations included serum creatinine, blood urea nitrogen, serum sodium, potassium, calcium and phosphorus, serum albumin, hemoglobin, and arterial blood gases. Post‐dialysis serum potassium and arterial blood gases were measured. ECG and forty‐eight hours ambulatory monitor (Holter monitor)(before, during, and after hemodialysis, till the end of the dialysis day and throughout the following day) were performed. Results: Group 1 showed significantly less post‐dialysis supraventricular arrhythmias than in dialysis day (210.9 ± 236 and 62.3 ± 14.4), respectively. Significantly less ventricular arrhythmias in post‐dialysis than in dialysis day (30.7 ± 50.4, and 106.2 ± 128.4), respectively. While in Group 2 there were insignificant differences regarding supraventricular arrhythmias (21.9 ± 28.9 and 16.6 ± 36.3) and ventricular arrhythmias (22.9 + 7.8 and 29.6 + 12.8) in dialysis day than in post‐dialysis day. There was significantly higher frequency of supraventricular and ventricular arrhythmias in the dialysis day in acetate hemodialysis in comparison to bicarbonate hemodialysis. Conclusion: Bicarbonate hemodialysis is less arrhythmogenic in comparison to acetate hemodialysis and has better effect on the blood pH and greater degree of base repletion. Continuous ambulatory ECG recording (Holter) is a useful tool in detecting arrhythmias in dialysis patients.

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