Irregular Narrow Complex Tachycardia in a 29-Year-Old Woman.

A 29-year-old woman without known medical illness was evaluated for incessant palpitations. She presented to an emergency department multiple times, where various diagnoses were made, including junctional tachycardia, atrial tachycardia, and atrial fibrillation. Therapy with propafenone, metoprolol, and rivaroxaban was initiated, but her symptoms continued. Echocardiography did not show evidence of structural heart disease. The patient was then referred to our hospital for further treatment and potential ablation for atrial fibrillation. At her clinic visit, a 12ECG revealed an irregular narrow complex tachycardia with group beating pattern (Figure 1). What is the rhythm shown in Figure 1? Please turn the page to read the diagnosis. Niyada Naksuk, MD J. William Schleifer, MD Abhishek J. Deshmukh, MBBS Malini Madhavan, MBBS Irregular Narrow Complex Tachycardia in a 29-Year-Old Woman