Pathophysiology and Natural History Congenital Heart Disease

Fifty-one patients with uncomplicated transposition of the great arteries (TGA) and normal pulmonary pressure who were 10 to 20 years old and 69 normal subjects matched for age were studied by M mode echocardiography. Left ventricular internal dimensions and posterior wall thickness showed positive correlation with the body surface area in the TGA as well as in the control groups. Values for these parameters in the TGA group were generally smaller than those in the normal population. Septal thickness of patients with TGA (5.9 ± 1 mm) was also smaller than that in the control group (6.6 ± 1 mm) (p < .0 1). Septal motion was normal in 1 1 patients with TGA and paradoxical in 19 patients in this group. In the other 21 patients the septum was flat. The following systolic time intervals of the left ventricle were found for patients with TGA: preejection period (PEP) 64 + 11 msec, ejection time (ET) 310 + 37 msec, and PEP/ET 0.21 ± 0.04. These values were significantly different from those of the right ventricle for the normal population: PEP 77 + 12 (p < .01), ET 327 + 25 (p < .05), and PEP/ET 0.24 + 0.03 (p < .01). Shortening fraction and mean velocity of circumferential fiber shortening (49 + 7% and 1.6 + 0.3 circ/sec, respectively) were also significantly higher (p < .01) in patients with TGA than in the control group (33 + 4% and 1. 1 + 0.2 circ/sec). These data should help achieve reliable quantitative and qualitative interpretations of echocardiograms of patients with TGA. Circulation 73, No. 4, 622-627, 1986. IN THE GREAT MAJORITY of patients with simple transposition of the great arteries (TGA) and normal pressure in the pulmonary circulation the disorder is corrected by surgical rerouting of the venous returns. One of the consequences of this approach is that the left ventricle maintains, throughout life, its anatomic relationship with the pulmonary circulation. This should influence not only the muscular growth but also the general dynamics of the ventricular walls. Indeed, in a previous report it has been shown that wall thickness and cavity dimensions of the left ventricles of patients with uncomplicated TGA are different from From the Cardiology Division, Department of Pediatrics, l'Hopital Sainte-Justine, Montreal, and The Hospital for Sick Children, Toronto, l'H6pital d'Enfants de Brabois, CHU de Nancy, France, and the Department of Mathematics and Statistics, University of Montreal. Address for correspondence: Jean-Claude Fouron, M.D., H6pital Sainte-Justine, 3175, C6te Ste-Catherine, Montreal, Quebec H3T 1C5, Canada. Received Sept. 30, 1985; revision accepted Dec. 12, 1985. those of normal children when they are as young as 7 to 10 months of age.' The population of this study was from 1 day to 10 years old. Data on the influence of the aging process on the same echocardiographic parameters later on in life are, to our knowledge, not available, even though the number of patients with TGA who are older than 10 is constantly increasing. Studies of anatomic specimens have all been carried out in younger subjects.2` To be able to achieve a reliable quantitative assessment of left ventricular function in patients with TGA older than 10 years of age, a reference table of values in patients with uncomplicated disease is indispensable. This collaborative study was planned to fulfill this need. Materials and methods Subjects. The study population consisted of 51 patients treated at two Canadian centers (H6pital Sainte-Justine, Montreal, and The Hospital for Sick Children, Toronto) and at the H6pital CIRCULATION 622 by gest on A ril 8, 2017 http://ciajournals.org/ D ow nladed from PATHOPHYSIOLOGY AND NATURAL HISTORY-CONGENITAL HEART DISEASE d'Enfants, Nancy, France. In all cases, the following criteria were met as conditions for inclusion in the study: uncomplicated and asymptomatic TGA, age from 10 to 20 years, and normal pressure in the pulmonary circulatory system verified by postoperative hemodynamic investigation and defined as a left ventricular systolic pressure less than 40 mm Hg. When cardiac catheterization was performed more than 1 year before the present echocardiographic study, noninvasive criteria for normal pulmonary pressures had to be satisfied.6 Patients with a gradient of 20 mm Hg or less in the left ventricular outflow tract were included in the study. All 51 patients had undergone surgical correction by either Mustard or Senning procedure. Their mean age was 14 years at the time of the echocardiographic study. In this group, the anatomic left and right ventricles refer to the venous and systemic ventricles, respectively. Another group of 69 normal subjects, matched for age, served as the control group. Echocardiographic technique. Each subject was represented by one echocardiographic study to avoid undue influence of individual cases on the data for the group. Echocardiograms were recorded and interpreted according to the technique previously described.' The following left ventricular parameters were measured: posterior wall (LVPW) and septal thickness (IVS), cavity dimensions at end-systole (LVIDs) and end-diastole (LVIDd), preejection period (PEP), ejection time (ET), shortening fraction, and mean velocity of circumferential fiber shortening (mean Vcf). Septal motion was classified as normal, flat, or paradoxical. Because of technical difficulties in complete identification of the pulmonary valve, systolic time intervals could not be measured in 10 subjects. No attempt was made to calculate the shortening fraction or mean Vcf of patients in whom septal motion was abnormal. Statistical analysis. Covariance analysis was performed to compare the data from the three centers. The analysis was carried out on all parameter values obtained, with age as the covariate. The effects of biological variables (age, height, weight, and body surface area) on the echocardiographic data from the normal group were then studied by regression techniques. For those variables with a high correlation coefficient (r > .5) the analysis was pursued further and the best regressor was sought among the biological variables previously mentioned and some of their transformations. The correlation studies showed that when a parameter was influenced by biological variables, body surface area always had the strongest index of correlation. Therefore, results of data analysis were always expressed in relation to body surface area. Tolerance limits about the regression lines for TGA and control groups were established by + 2 residual SDs. For clinical application, a table was constructed from these regressions giving the mean and the upper tolerance limit. The results for parameters not influenced by the set of biological variables are given as mean + SD. Their values in the TGA group were compared with those in the control group by Student's t test.