The Significance of the Posteriorly Oriented QRS sE Loop in Congenital Heart Disease

A Potential Source of Error in the Electrorardiographic Diagnosis of Ventricular Hypertrophy

¹ Department of Pathology, Charles T. Miller Hospital, St. Paul, Minnesota
² Department of Medicine, University of Minnesota, Minneapolis
³ Department of Pediatrics, University of Minnesota, Minneapolis
⁴ Department of Pediatrics, University of Florida College of Medicine, Gainesville, Florida

In 15 necropsy-proved cases with various congenital cardiac malformations, potential sources of error were present when utilizing conventional electrocardiographic criteria to determine ventricular hypertrophy.

These potential sources of error were the ultimate result of three types of posteriorly oriented QRS sE loops, with the culminative electrical forces in all cases resulting in rS complexes in lead V₁, and deep S complexes in lead V₆.

Type I QRS sE loops were oriented right and posterior. Each case at necropsy showed isolated right ventricular hypertrophy. The proper electrocardiographic interpretation of right ventricular hypertrophy is aided by a predominant R wave in lead V₄R and marked right axis deviation in the frontal plane, even though an rS or QS wave is present in lead V₁.

Type II QRS sE loops were positioned directly posterior, with little rightward or leftward projection, producing sterotype rS complexes in all precordial leads, including lead V₄R. This type of QRS loop is present in malformations with distortions on their conduction system.

Type III QRS sE loops, positioned posterior, leftward, and superior, also have rS complexes in V₁. By conventional electrocardiographic criteria each case had left ventricular hypertrophy, confirmed in all at necropsy.

In addition, however, relatively deep S waves and tall R waves were present in V₆ and aVR, respectively. These patterns might suggest additional right ventricular hypertrophy—a supposition unconfirmed at necropsy. Thus we interpret these patterns as a manifestation of marked left ventricular hypertrophy, even though the terminal portion of the QRS sE loop is rightward and posterior. The association of marked left axis deviation and a decrease in the size of the S wave in lead V₇ aids in the proper diagnosis of isolated left ventricular hypertrophy.