日本小児循環器学会雑誌 Pediatric Cardiology and Cardiac Surgery

Background: In recent years, atrial septal defect has been the most common congenital heart disease discovered during school heart disease screening. Therefore, we carefully examine the electrocardiogram (ECG) of incomplete right bundle branch block (IRBBB) pattern in lead V₁, particularly the rsR′ type. The rsR′ pattern, however, frequently disappeared at the secondary screening. The presence of a deep Q wave in lead V₆ (QV₆), which is a screening criterion for heart disease, occasionally disappeared at the secondary screening. The findings were investigated because they were thought to be the lead misplacement.

Methods: The subjects included 14 students who showed rsR′ pattern in lead V₁ and 3 students who had an ECG finding of deep QV₆ (≧0.5 mV). Their ECGs were recorded in both the standard and upward displaced positions on the chest. Furthermore, synthesized vectorcardiography was simultaneously recorded.

Results: At the secondary screening, the finding of IRBBB pattern of rsR′ type had vanished in 14 students and an atypical IRBBB pattern or normal wave form was discovered. When the chest leads were displaced to the upper position, the rsR′ pattern appeared. At the secondary screening, deep QV₆ amplitude decreased to ＜0.5 mV in 3 students. When the chest electrodes were positioned upward by one intercostal space, deep QV₆ appeared.

Conclusions: These findings were thought to be the result of precordial lead displacement. They could be because the amplitude of waves in unipolar leads changed in inverse proportion to the square of the distance between an electrode and the heart.