Surgical treatment of apical muscular ventricular septal defects

We recently received the December 1999 issue of the European Journal of Cardio-thoracic Surgery and read the case report by Dr. Pretre concerning surgical closure of apical muscular ventricular septal defects via an incision in the left ventricle [1]. In describing their successful case, the authors made very interesting points such as the precise localization of the incision and the modification of it, due to the peculiar coronary artery pattern and the tailoring of the patch, that has been done ad hoc, so as to prevent geometrical deformity of the left ventricle and to preserve ventricular performance.

Closure of this kind of ventricular septal defect is known to be difficult and frequently suboptimal; the surgical approach via a right atriotomy, through the tricuspid valve, is often not possible because of the peculiar position of this defects, far away from the tricuspid valve plane, distal to the moderator band, often hidden by multiple muscular trabeculations, which prevent the surgeon from identifying the anatomical borders of the defect. An incision on the left ventricular myocardium, such as that proposed by Pretre et al., exposes clearly the defect in the smooth left surface of the interventricular septum. However, it has been widely proven to damage irreversibly the left ventricular myocardial structure, jeopardizing the ventricular function in the long term. Furthermore, the scarring tissue at the incision level is often responsible for triggering arrhythmic episodes that influence negatively the clinical result of surgery [2]. We have recently published our experience with apical muscular ventricular septal defects [3], in which we proposed a longitudinal incision of 10–15 mm into the infundibular apical free wall, on the right of and parallel to the distal part of the left anterior descending coronary artery. This surgical access exposes a region of the right ventricular septal surface that is called the apex of the infundibulum [4], and in which apical muscular ventricular septal defects are usually located. Through this incision, the identification of the defect has been extremely easy. Our positive experience with 100% survival and 0% of residual shunt convince us of the effectiveness of this approach.

Recently, Geva et al. [5] reported a combined echocardiographic and magnetic resonance imaging study on 31 normal individuals about regional differences in right systolic function. They demonstrated that the right ventricular inlet (or right ventricular sinus) made up 81±6% of the combined right ventricular end diastolic volume and 87±4% of the combined stroke volume. The infundibulum accounted for the remaining 19±6 and 13±4%, respectively (P≪0.0001). The conclusions of this interesting study could possibly support the goodness and safety of a right ventricular apical infundibulotomy, which affects only the less ‘noble’ component of the right ventricle.

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