Tac(hy)rolimus: A Case of Tacrolimus-induced Tachycardia

The Editor, The case involves a 35-year-old female patient who had end-stage renal disease due to IgA nephropathy and was planned for a kidney transplant with her mother as the donor. She was started on tacrolimus 4 mg/day on postoperative day-2 (POD-2) as a part of the pretransplant regimen. Approximately 1 h after receiving the medication, she developed palpitations, and her heart rate increased to 134/min from the baseline of 78/min. The symptoms resolved spontaneously after 5–6 h, and further doses of tacrolimus were not given pretransplant. However, again, after the introduction of tacrolimus posttransplant on the first POD, the patient developed tachycardia [Figure 1], palpitations, and shortness of breath 45 min later. An electrocardiogram revealed sinus tachycardia, and echocardiogram was normal. The patient’s troponin I levels remained normal, and there were no serial ST-T changes observed. Her serum electrolytes such as sodium, potassium, calcium, and magnesium were also normal. Tacrolimus was stopped; however, the levels were not checked, and the patient continued with cyclosporine, mycophenolate mofetil, and steroid. Holter monitoring was conducted, which was normal. No active bleeding, fever, or other offending drugs were found. The patient was doing well at 5 months posttransplant, with a creatinine level of 1.2 mg/dl. The tachycardia was presumed to be a side effect of tacrolimus due to the temporal relationship and reproducibility with rechallenges.Figure 1: Electrocardiogram showing sinus tachycardiaTacrolimus is an immunosuppressive agent that is used to prevent organ rejection after transplantation. However, its use has been associated with various cardiovascular complications, including tachycardia and arrhythmias. In a case report by Erdoğan et al., a 13-year-old boy who underwent kidney transplantation developed sinus tachycardia after receiving tacrolimus.[1] The authors noted that tacrolimus-induced sinus tachycardia is a common finding in kidney transplant recipients, particularly in the early posttransplant period. However, the exact mechanism of tacrolimus-induced tachycardia is not clear. It is believed to be related to the drug’s effect on the autonomic nervous system, leading to sympathetic activation and increased heart rate. The authors suggested that careful monitoring of heart rate and blood pressure is essential in patients receiving tacrolimus.[1] In another case report by Kim et al., a 36-year-old male who underwent kidney transplantation developed supraventricular arrhythmia after receiving tacrolimus.[2] The authors noted that tacrolimus-induced arrhythmias are rare but can be life-threatening. Finally, Hodak et al. reported a case of QT prolongation and near-fatal cardiac arrhythmia after intravenous administration of tacrolimus in a liver transplant recipient. The authors suggested that tacrolimus-induced QT prolongation may be related to the drug’s effect on ion channels in cardiac myocytes.[3] In conclusion, tacrolimus-induced tachycardia and arrhythmias are rare but potentially life-threatening complications of transplantation. The exact mechanism of these complications is not clear but may be related to the drug’s effect on the autonomic nervous system, calcium signaling, ion channels, and mitochondrial function. In this case, the patient developed tachycardia and palpitations approximately an hour after receiving tacrolimus during the pretransplant regimen. Although the symptoms resolved spontaneously after 5–6 h, tacrolimus was discontinued pretransplant. When tacrolimus was reintroduced posttransplant, there was recurrence of tachycardia and palpitations. Tacrolimus was stopped, and the patient continued with cyclosporine, mycophenolate mofetil, and steroid, which resulted in a favorable outcome. Declaration of patient consent The authors certify that patient consent has been taken for participation in the study and for publication of clinical details and images. Patients understand that the names and initials would not be published, and all standard protocols will be followed to conceal their identity. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.