ABC | Volume 110, Nº4, April 2018

Case Report Primary Ventricular Fibrillation in a Patient with Mild Hypercalcemia Rita Marinheiro, Leonor Parreira, Pedro Amador, Francisco Sardinha, Sara Gonçalves, Sónia Serra Centro Hospitalar de Setúbal, Setúbal, Lisboa – Portugal Mailing Address: Rita Marinheiro • Rua Camilo Castelo Branco, 2910-446. 2900, Setúbal – Portugal E-mail: ritamarinheiro@gmail.com , ritamarinheiro@gmail.com Manuscript received October 10, 2016, revised manuscript April 04, 2017, accepted July 06, 2017 Keywords Ventricular Fibrillation; Shock, Cardiogenic; Hypercalcemia; Syncope; Unconsciousness. DOI: 10.5935/abc.20180059 Introduction An abnormally short QT interval can be caused by several situations such as hypercalcemia, hyperkalemia, acidosis, hyperthermia, effects of drugs like digitalis or congenital short QT syndrome (SQTS). 1 Primary hyperparathyroidism (PHPT) can ultimately cause short QT interval since overproduction of parathyroid hormone (PTH) causes hypercalcemia. However, cardiac arrhythmias are uncommon and electrical stormhas been rarely described in patients with hypercalcemia. 2 Secondary causes of short QT must be ruled out before considering the diagnosis of SQTS. 3 First described in 2000, SQTS is a congenital primary electric disorder characterized by abnormally short corrected QT interval (QTc) on the surface electrocardiogram (ECG) that is associated with sudden cardiac death (SCD) in individuals with structurally normal heart. According to 2015 ESC Guidelines for the management of patients with ventricular arrhythmias, 4 SQTS is diagnosed in the presence of a QTc ≤ 330 msec or it can be diagnosed in the presence of a QTc < 360 ms and one or more of the following factors: pathogenic mutation, family history of SQTS, family history of sudden death before 40 years old and/or survival of a ventricular tacchycardia (VT)/ ventricular fibrillation (VF) episode in the absence of heart disease. The authors present a case of an electrical storm due to polymorphicVT suspected tobe causedby SQTS. However, PHPT was diagnosed one year later andmild hypercalcemiawas thought to have been the cause or a contributor for the electrical storm. Case Report A previous healthy 44-year-old woman was brought to the emergency room after an unwitnessed fall followed by extreme anxiety. She had no respiratory distress or others symptoms; she denied cardiovascular risk factors or alcohol and drugs consumption. Her family history was irrelevant. On physical examination, she was calm, apyretic, hemodynamically stable and her neurological exam and cardiac and pulmonary auscultations were normal. Her blood pressure was 90/61mmHg and heart rate (HR) was 114 beats per minute (bpm). While she was under observation, she  lost consciousness. Cardiac monitoring confirmed a VF episode and the patient was shocked and recovered. Her laboratory values were normal, including hemogram, electrolytes, renal function, thyroid hormones, cardiac enzymes and serum D-dimer. Her total calciumwas 9.3 mg/dL and albumin was 3.0 g/dl (normal range 3.5 – 5.0 g/dL). The corrected calcium for hypoalbuminemia was 10.3 mg/dL (normal range 8.4 - 10.2 mg/dL). She had an ECG taken by emergency team before hospital admission (Figure 1) that showed a sinus rhythm at a HR of 75 bpm, normal PR interval (160ms) and QRS duration (90 bpm), no ST changes and a QTc of 349ms (according to Bazett´s formula). T peak - T end interval (0.50 msec) and T peak  - T end / QT ratio (0.18) were not prolonged. Short QT interval was not detected in the subsequent ECGs, including in the one performed after the first shock. In the next hours, cardiac monitoring demonstrated premature ventricular contractions (PVC) with distinct morphologies and R-on-T phenomenon, which was responsible for polymorphic VT that degenerated to VF (Figure 2). Ten external shocks were applied and treatment with amiodarone and beta‑blockers was ineffective. Sedation and orotracheal intubation were decided due to the requirement of successive shocks. Emergency coronary angiography excluded coronary artery disease (CAD). Since paroxysmal VTwere presumably caused by PVCwith short coupling intervals (“R-on-T” extrasystoles falling on the peak of the T wave), isoproterenol infusion was started (0.08 mg/h). HR increased and arrhythmic episodes disappeared. Twenty‑four hours later this treatment was stopped and no more arrhythmias were detected. A comprehensive approach was performed. During hospitalization, successive ECGs did not show short QTc interval or other alterations. PVCs were noted in some instances on ECGs but they had different morphologies and only a few of them had a short coupling interval. Laboratory values remain normal. Transthoracic echocardiogram was normal and cardiac magnetic resonance imaging (MRI) did not visualize late enhancement or other changes. Flecainide test was negative and electrophysiologic study (EPS) was normal with no arrhythmia induction. The treadmill test (Bruce protocol) was performed. In rest, her QT interval was 320 ms and HR 90 bpm (QTc = 392 ms); in peak effort (HR = 134 bpm), QT was 280ms (QTc = 418 ms). She requested to terminate the test in stage 1 (1.7 mph at 10% grade) since she was very tired. Further investigation for SQTS as the cause of VF was not performed and a single chamber implantable cardioverter‑defibrillator (ICD) (ProtectaVR D364VRM, Medtronic  ) was implanted for secondary prevention. The patient was dischargedwith nomedical therapy. Fifteen days later, the patient complained of palpitations and the ICD interrogation demonstrated non-sustained VT initiated by PVC with short coupling intervals. Quinidine was initiated and symptoms as well as non-sustained VT episodes disappeared. 393