Pathophysiology and Natural History Congenital Heart Disease

The prolate ellipsoid geometry of the left ventricle with normally related great arteries minimizes wall tension and functionally commits the ventricular septum to the systemic ventricle. Ageand pressure-dependent changes in angiographically determined left ventricular volume and mass measurements have been reported in patients with d-transposition of the great arteries and intact interventricular septum. The objective of this study was to evaluate the changes in left ventricular geometry in this lesion during infancy by means of subxiphoid two-dimensional echocardiography. Left ventricular geometry in the transverse equatorial plane of the ventricle was evaluated in 19 neonates within 24 hr of initial cardiac catheterization, in 16 of 19 within 24 hr of cardiac catheterization before performance of Senning'sprocedure, and in five of 19 after postoperative catheterization. Ventricular geometry was qualitatively evaluated according to ventricular septal orientation and quantitatively by correlation of the left and right ventricular systolic pressure ratio with the transverse minor axis ratio. Qualitative changes in left ventricular geometry during infancy and after intra-atrial baffle procedure were demonstrated by subxiphoid two-dimensional echocardiography. The end-systolic transverse minor axis ratio showed significant correlation (r = .58, p < .001) with the peak systolic pressure ratio. The evolution of dynamic left ventricular outflow stenosis in patients with d-transposition of the great arteries and intact interventricular septum was related to, but not solely determined by, the progressive change in left ventricular geometry. Changes in left ventricular geometry in d-transposition of the great arteries with intact ventricular septum may have functional implications regarding angiographic volume determinations and timing of arterial "switch" procedures. Circulation 68, No. 4, 733-739, 1983. THE SYSTEMIC LEFT VENTRICLE is a prolate ellipsoid with circular geometry in the transverse equatorial plane.' 2 This configuration minimizes wall tension and functionally commits the interventricular septum (IVS) to the left ventricle.3 Two-dimensional echocardiography has demonstrated changes in left ventricular geometry caused by volume overload of the right ventricle.4 Pressure-dependent changes in left ventricular geometry in d-transposition of the great arteries (d-TGA) and intact IVS have been observed by means ofM mode echocardiography.S 6 Hemodynamic problems associated with switching ventriculoarterial attachments in this lesion have been attributed to poor left ventricular function related to decreased From the Department of Cardiology, the Children's Hospital Medical Center, Boston. Funded in part by a research fellowship sponsored by the Canadian Heart Foundation. Address for correspondence: Nicolaas H. van Doesburg, M.D., Ultrasonic Laboratory, Section of Cardiology, Sainte-Justine Hospital, 3175, Ch. Cote Ste.-Catherine, Montreal, Quebec, Canada H3T IC5. Received Sept. 5, 1982; revision accepted May 26, 1983. Vol. 68, No. 4, October 1983 mass.7'8 Lev et al.,9 however, using postmortem morphometrics, reported that the left ventricular mass in dTGA with intact IVS was normal during the first 3 months of life. Others have reported ageand pressuredependent increase in angiographically determined diastolic volume and mass.'0'" The objective of this study was to evaluate left ventricular geometry in patients with d-TGA and intact IVS and the relationship of any changes in left ventricular afterload, preload, and dynamic outflow tract obstruction to previously reported angiographic volume/mass measurements. Materials and methods Subxiphoid two-dimensional echocardiograms were obtained from 19 neonates with d-TGA and intact IVS at 1 to 6 days of age within 24 hr before balloon atrial septostomy. Repeat echograms were obtained within 24 hr of cardiac catheterization before performance of Senning's procedure in 16 of 19 infants 3 to 9.5 months of age (median 6). Repeat measurements were obtained at postoperative catheterization in five of 19, 5.5 to 22 months of age. Long axial oblique left ventricular cineangiography was used to exclude neonates with fixed subpulmonic stenosis. 12. 13 Intraventricular and intravascular pressures were 733 by gest on M ay 0, 2017 http://ciajournals.org/ D ow nladed from