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Left Posterior Fascicular Block Due to High-Dose Interleukin-2

PGY-3 Resident, Department of Internal Medicine, Johns Hopkins University/Sinai Hospital of Baltimore, Baltimore, MD

Samuel R Denmeade, MD

Associate Professor of Oncology and Pharmacology, Department of Oncology, School of Medicine, Johns Hopkins University

Reprints: Dr. Singla, Sinai Hospital of Baltimore, 2401 W. Belvedere Ave., Baltimore, MD 21215, fax 410/601-9601, asingla{at}lifebridge-health.org

OJECTIVE: To report a case of reversible left posterior fascicular block (LPFB) associated with high-dose interleukin-2 (IL-2) therapy.

CASE SUMMARY: A 50-year-old white, nonsmoking male with a history of hypertension, hyperlipidemia, paroxysmal atrial fibrillation, and hypothyroidism had been recently diagnosed with metastatic clear cell–type renal cell carcinoma. He was started on high-dose IL-2 therapy (600,000 IU/kg/dose by 15-min intravenous infusion every 8 h for up to 14 consecutive doses over 5 days, as tolerated). He developed new-onset LPFB after the second dose of IL-2, which was diagnosed electrocardiographically with right axis deviation; deep S waves in lead I; and qR waves in leads II, III, and aVF. He denied chest pain, palpitations, or syncope. The LPFB resolved 18 hours after discontinuation of IL-2 without any potential complications or delay of hospital discharge. The patient completed 9 of 14 doses of IL-2 therapy. Similar electrocardiogram changes were noticed during 2 subsequent cycles of high-dose IL-2 treatment, both of which resolved spontaneously.

DISCUSSION: High-dose IL-2 is a Food and Drug Administration–approved biological agent used as monotherapy for the treatment of metastatic renal cell carcinoma and metastatic melanoma. Capillary leak syndrome has been associated with IL-2 therapy and many of its cardiac and noncardiac toxicities. In our patient, LPFB was observed as a reversible adverse reaction to high-dose IL-2 therapy. The Naranjo probability scale indicates a probable relationship between LPFB and high-dose IL-2 in this patient. LPFB has not previously been reported as an adverse reaction associated with high-dose IL-2 therapy.

CONCLUSIONS: LPFB may be a reversible cardiac complication associated with high-dose IL-2 therapy. Healthcare professionals should be aware of this potential adverse effect.

Key Words: interleukin-2, left posterior fascicular block

Published Online, July 29, 2008. www.theannals.com, DOI 10.1345/aph.1K669