Vectorcardiographic Investigation of Brugada ECG Unmasked by Recording at Higher Intercostal Space

Aims: Brugada syndrome is characterised by ST segment elevation in right precordial leads and associated sometimes with idiopathic ventricular fibrillation leading to sudden cardiac death. Although ECG recording at higher intercostal space unmasks Brugada syndrome, the vectorcardiographic (VCG) mechanisms of this unmasking remain unknown.

Place and Duration of Study: Noninvasive ECG laboratory of Heart Center, Kyushu University Hospital, Fukuoka, Japan, from November 2013 to April 2015.

Methodology: Twelve-lead digital ECG was recorded at standard (4th) and higher (3rd and 2nd) intercostal space in 5 patients with Brugada syndrome. The ECG data were transformed automatically to the VCG data based on the corrected three orthogonal Frank leads (X, Y and Z) and three vector loops of P, QRS and T waves were constructed and projected to the three (horizontal, frontal and right sagittal) orthogonal planes.

Results: ST elevation in the standard right precordial leads (V1 to V3) was augmented by the 12-lead ECG recorded at higher intercostal space. Saddle back ST elevation was often converted to coved type ST elevation by this invent. QRS loop was open in all 5 patients, and the maximum J-point vector showed right anterosuperior direction, whereas T loop showed left anteroinferior direction. The J-point vector faced toward and the maximum T vector faced backward the right precordial ECG electrodes, which was accentuated by shifting them to the higher intercostal space.

Conclusion: Unmasking of Brugada ECG was explained well even in this small-sample study by the spatial relationship between the orientations of ST-T vector and the standard right precordial ECG electrodes positioned at the higher intercostal space.