ABC | Volume 110, Nº4, April 2018

Case Report Marinheiro et al Primary ventricular fibrillation in a patient with mild hypercalcemia Arq Bras Cardiol. 2018; 110(4):393-396 Figure 1 – Twelve-lead electrocardiogram (ECG) taken by emergency team before hospital admission demonstrating a corrected QT interval (according to Bazett´s formula) of 349 milliseconds (msec). Figure 2 – Electrocardiogram (ECG) during ventricular fibrillation (VF) episode. After one year, a laboratory study was done once again due to complains of asthenia and anorexia. Serum calcium was 10.2 mg/dL and albumin 3.2 g/dL, corrected calcium was 10,8 mg/dL. Serum phosphorus was 1.8 mg/dL (normal range 2,7 – 4,5 mg/dL). Potassium and magnesium were normal. Based on these results, PTHmeasurement was performed and it was elevated: 344.8 pg/mL (normal range 15 - 68.3 pg/mL) and PHPT was diagnosed. Bone densitometry (DEXA), renal function and urine calcium were normal. The patient was referred to endocrinology surgery but according to the NIH criteria for parathyroidectomy, the surgery was not recommended . She remains asymptomatic with no further VT episodes or frequent PVCs. Discussion VF causes vary according to the age group. In young, it is mostly due to channelopathies, cardiomyopathies, myocarditis and substance abuse, while in patients older than 40 years, CAD is the leading cause. 4 Taking into account the patient´s age, it seemed reasonable to perform coronary angiography. Brugada´s pattern was not evident but regarding intermittent alterations in this syndrome and the good response to isoproterenol, a flecainide test was performed to exclude this diagnosis. Cardiac MRI was also crucial to exclude cardiomyopathy. Although the EPS is not indicated to stratify risk in SQTS since its sensitivity and negative predictive value are low, 5 the SQTS diagnosis was not absolutely certain and so the EPS was performed and it was normal. Since SQTS patients show a reduced adaptation of the QT interval to HR, 6 the patient underwent the treadmill test but she did not reach maximum predicted HR. However, the variation from rest to peak effort of 40 ms is probably attenuated. After excluding all other causes of electric storm, SQTS was considered a reasonable diagnosis based on absence of structural heart disease, normal laboratory values and the presence of a short QT interval in one ECG. Serum calcium was only slightly increased (10,3 mg/dL) so secondary causes of SQTS were considered to be absent. According to the ESC guidelines, a SQTS diagnosis can be made based on a QTc < 360 ms and an episode of VF without structural heart disease. 4 The absence of short QT in the subsequent ECGs as well as the absence of other common electrocardiographic features present in 394