Comparison Between Echocardiographic Subtraction Method and First-Pass Radionuclide Ventriculography for Measuring Right Ventricular Volume After Operative “Repair” of Patients With Tetralogy of Fallot

A of right ventricular (RV) function is clinically relevant in following various forms of repaired congenital heart disease.1–5 Unfortunately, the irregular crescent shape of the right ventricle does not allow application of the simple echocardiographic methods available for evaluating the left ventricle. Recently, Tomita et al6 described a modification of the Krebs’ echocardiographic subtraction method7 showing a very good correlation both experimentally and clinically in an adult population. With this method, the RV volume is measured by subtracting the entire left ventricular volume (septum and free wall included) from that of the sum of the left ventricle, septum, and right ventricle, based on echocardiographic apical 2and 4-chamber views by means of the area-length formula (Figure 1). This study assesses the efficacy of Tomita’s method in evaluating RV volume and function in children after repair of tetralogy of Fallot, comparing it, as the gold standard, to firstpass radionuclide ventriculography.8 • • • Forty patients (15 boys and 25 girls) who had undergone complete repair of tetralogy of Fallot at a mean age of 14 6 12 months (range 2 to 58) were studied with 2-dimensional Doppler echocardiography and radionuclide first-pass ventriculography. Mean age at follow-up was 74 6 41 months (range 20 to 167) and the mean follow-up period was 60 6 33 months (range 13 to 140). Twenty-one babies had had transventricular and 19 transatrial repair. RV outflow tract augmentation had been obtained by means of a transannular patch in 26 cases, and transinfundibular in 4. In 4 patients, a previous Blalock-Taussig shunt had been performed. All patients were in New York Heart Association functional class I, showing no hemodynamically relevant residual lesion during complete echocardiographic evaluation. A control group consisting of 36 healthy children matched for age, sex, and body surface area was studied with 2-dimensional echocardiography. The intraand interobserver variability was assessed by the intraclass correlation coefficient in 15 unselected normal and pathologic patients by 3 of us (OM, SS, GSM) in 2 different sets of examinations.9 Two-dimensional echo studies were performed using a Sonos 1500 ultrasonographer (Hewlett-Packard, Andover Massachusetts) with 5and 3.5-MHz transducers. Images for analysis were acquired from apical 4and 2-chamber views at end-diastole (which falls on the peak of the R wave of the referring electrocardiogram) and at end-systole, the frame immediately preceding the atrioventricular valve opening, usually at the end of the T wave. RV end-diastolic and endsystolic volumes were measured on 3 different cardiac cycles as previously described by Tomita, using the formula: