Figure 1: Normal ECG with no ischemic changes
He was diagnosed with acute exacerbation of dyspepsia and treated with a single 8mg dose of ondansetron intravenously. Within a few seconds after taking around 0.5ml (2mg) of ondansetron, the patient developed chest tightness, redness and burning sensation around the injection site along with urticaria, hypotension and bronchospasm. He was immediately treated with hydrocortisone 100 mg intravenously, and the reaction resolved within a few minutes. His vital signs were as follows: body temperature, 36.2°C; blood pressure, 90/60 mmHg; respiratory rate,20 breaths/min; heart rate, 94 beats/min; and oxygen saturation, 88% on room air.
An ECG was obtained 15 minutes after administration of ondansetron which showed no change from the baseline ECG. However, the patient’s cardiac troponin T levels had elevated to 812ng/L, a 42x increase from his previous levels. The patient was followed-up 15 minute later following the reaction, where he complained of severe headache, dizziness and fatigue. It was noted that the other symptoms had subsided. He was given once-off aspirin loading dose of 312 mg orally. A subsequent ECG and cardiac troponin was repeated every 6 hours and showed normal ECG and serial drop in troponin levels of 231ng/L,178ng/L,128ng/L and 78ng/L}. On follow-up, we inquired about his previous usage of ondansetron and reported no history of drug or food allergies and no previous exposure to ondansetron. Additionally, he does not have a history of surgery or chemotherapy.
He was then referred to the cardiac center for complete cardiac evaluation. An echocardiogram demonstrated mild left ventricular hypertrophy with normal ejection fraction with no ischemic changes. He also underwent a cardiac stress test and had no chest pain or ECG changes. There was no indication for cardiac catheterization and the patient was discharged. It was concluded that the sudden cardiac event was most likely ondansetron-induced coronary spasm that resolved spontaneously. Based on the allergic reaction that ensued prior to these presentations, Kounis syndrome was suspected as a probable cause.