Electroanatomic Relationships in Patients With Primum Atrioventricular Septal Defect

Abstract

Abnormality in the position of the papillary muscles changes continuously with the abnormality of the QRS axis. Understanding the electroanatomic relationships provides important insight into developmental relationships between the conduction system and the trabecular structures in primum AVSD patients. These results may provide insights in understanding the continuity of primum AVSD abnormality, in estimating the best surgical approach, and predicting the prognosis of primum AVSD patients.

The comparative relationships between locations of the papillary muscles and electrophysiologic QRS axis in patients with atrioventricular septal defect and common as opposed to separate orifices in the valve guarding the common atrioventricular junction

“…Data concerning QRS axis and position of papillary muscles in patients with atrioventricular septal defect permitting only atrial shunting, and of normal subjects, were extracted from the population assessed in our previous study. 4 The patients with primum defects had been diagnosed and followed up at the Duke University Medical Center from 1996 until 2007. Echocardiographic images were reviewed independently by an investigator and an echo expert to confirm the presence of the shunting through the atrioventricular septal defect at the atrial level only.…”

“…Such a deviation in the location of the papillary muscles is known to be a feature of patients with atrioventricular septal defect in the setting of a common atrioventricular junction. [3][4][5] This cohort, therefore, provides a unique model for studying electrophysiologic-anatomic relationships in the heart. This has been prominently considered as in the so-called "ostium primum" defect, in which shunting across the septal defect occurs only at the atrial level, left ventricular activation is known to be typically directed leftward and superiorly compared with normal, with a mean frontal plane QRS axis between −60 and −130°.…”

“…That study also documented a significant correlation between the locations of the papillary muscles and the degree of leftward deviation of the QRS axis. 4 In our current study, we have also included patients having the so-called "complete" variant of atrioventricular septal defect, the significant feature of this group being that shunting across the defect occurs at both atrial and ventricular levels, such shunting being exclusively at atrial level in those with the primum defect. We hypothesised, therefore, that the QRS axis would differ between the two types of atrioventricular septal defect, as shunting at only the atrial level causes only a volume, and hence diastolic, overload for the right ventricle, whereas shunting at the ventricular level would cause both volume and pressure, or systolic, right ventricular overloads.…”

Electrophysiology Follows Anatomy?⁎⁎Editorials published in JACC: Cardiovascular Imaging reflect the views of the authors and do not necessarily represent the views of JACC: Cardiovascular Imaging or the American College of Cardiology.

“…The study by Hakacova et al (5) was based on 2 assumptions: 1) the positions of the left ventricular papillary muscles between the interventricular septum and the left ventricular free wall localize the lateral borders of the fascicular fen, and therefore localize 2 of the starting points of left ventricular activation; and 2) an anterior papillary muscle that is closer to the septum than the posterior papillary muscle results in delayed activation of the anterior left ventricular free wall and in leftward deviation of the QRS axis. The objective of the study by Hakacova et al (5) was to test the hypothesis that in primum AVSDs, an anatomic imbalance in the positions of left ventricular papillary muscles correlates with leftward deviation of the QRS axis.…”

“…Why then did Hakacova et al (5), in this issue of iJACC, propose a new explanation, namely that leftward deviation of the QRS axis in AVSDs is the result of (correlates with) an imbalance in the positions of left ventricular papillary muscles? Papillary muscle locations relative to the interventricular septum and left ventricular free wall are examples of recent clinical interest in the positions of these structures.…”