SUN-805 - A Case of Sustained Ventricular Tachycardia Soon after Initiation of Teriparatide

Background: Teriparatide (rhPTH1-34) is an anabolic agent used to treat osteoporosis. Prior analyses have shown that teriparatide use is associated with transient increases in heart rate and, without a statistically significant increase in major adverse cardiovascular events or heart failure. 

Clinical

Case:

A 73-year-old woman with a history of severe postmenopausal osteoporosis diagnosed eight years prior and treated with multiple doses of zoledronic acid, was referred to endocrinology for continued bone mineral density decline. After evaluation, she was prescribed teriparatide.

She had a pertinent medical history of atrial fibrillation, mitral valve prolapse, coronary artery disease, heart failure with mid-range ejection fraction, and anxiety. Her medication regimen included trazodone, hydroxyzine, amitriptyline, and cyclobenzaprine, all of which have been associated with QT prolongation and ventricular arrythmias. Additionally, she had an episode of syncope a few weeks prior and episodes of dizziness and malaise through the past year.

Upon initiating teriparatide, she reported mild dyspnea and felt unwell. She stopped the medication after four days and symptoms improved. She resumed teriparatide three days later and developed acute onset palpitations and dyspnea the following afternoon. She presented to the hospital and was found to have an elevated blood pressure of 166/35 mmHg and tachypnea. ECG revealed ventricular tachycardia. After two amiodarone boluses and one defibrillation shock, she converted to sinus rhythm. Teriparatide was discontinued.

Transient hypercalcemia, a common adverse event of teriparatide, could cause ventricular arrhythmias in severe cases. However, at hospital admission, her serum calcium was 10.2 mg/dL, within normal limits. Left heart catheterization ruled out obstructive coronary artery disease, and echocardiogram displayed a low normal ejection fraction of 50%. Due to the episode of sustained VT, a single-chamber Medtronic AICD was implanted. One month later, she sustained a comminuted fracture of the right humerus after a fall from standing height.

Conclusion: It is unlikely that teriparatide increases risk of ventricular tachycardia. While atrial arrhythmias are associated with teriparatide use, ventricular arrhythmias due to treatment have not been reported. Thus, underlying predisposing cardiovascular conditions or cardiotoxic medications should be investigated in patients with major cardiac adverse events. Monitoring calcium levels in patients treated with teriparatide is recommended, including those with cardiovascular risk factors. Patients at high risk for fractures who receive teriparatide remain vulnerable to fracture if treatment is interrupted.

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