Thalidomide-induced heart block in a dialysis patient.

Abstract

Sir, We report the case of a patient with thalidomide-induced third-degree heart block when used in context of myeloma and acute renal failure. An 88-year-old female patient was commenced on thalidomide 50 mg daily along with pulsed dexamethasone for treatment of newly diagnosed multiple myeloma. After 3 weeks of treatment, the dose of thalidomide was increased to 100 mg daily. Electrocardiogram (ECG) at baseline presentation and on 50 mg od showed normal sinus rhythm with a ventricular rate of 83/min. There was no evidence of delayed atrio-ventricular conduction (PR interval 130 ms) and normal QRS. After 3 days of 100 mg thalidomide, the patient started feeling light-headed on minimal exertion. A repeat ECG showed third-degree heart block with a ventricular rate of 31 beats per minute and left bundle block. The patient had no history of ischaemic heart disease. Serum electrolytes, thyroid function tests, cardiac enzymes and chest x-ray were within normal limits. We observed this patient for 24 h, and the ECG abnormality did not improve. After counselling about the need for ongoing treatment with thalidomide treatment for her myeloma and the risks of infections with a permanent pacemaker, she went on to have a permanent pacemaker fitted. Due to its anti-angiogenesis activity thalidomide has been used for the treatment of multiple myeloma. The combination of thalidomide and dexamethasone, often in combination with cylcophosphamide, is now one of the most common regimens for patients with newly diagnosed multiple myeloma [1]. As thalidomide predominately undergoes pH-dependent spontaneous hydrolysis in all body fluids into multiple metabolites and is passively excreted, its pharmacokinetics are not expected to change in patients with impaired liver or kidney function. Hence, no dose reduction is recommended for patients with renal impairment or those on dialysis. Thalidomide has a number of well-recognized side effects such as teratogenicity, skin rash, peripheral neuropathy, pneumonitis and venous thromboembolism (VTE). However, the incidence of heart block has been rarely reported. There have been similar case reports of conduction abnormalities with thalidomide [2]. We conclude that cardiac monitoring should be instituted and screened for when treating patients with this drug. Regular ECGs should be performed when rate disturbance is noted on this therapy. Conflict of interest statement. None declared.