CONGENITAL HEART DISEASE Assessment of left ventricular contractile state after anatomic correction of transposition of the great arteries

When compared with intra-atrial baffle repairs for D-transposition of the great arteries (TGA), anatomic correction offers the theoretic advantage that it results in the use of the left ventricle (LV) as the systemic ventricle. Although the long-term success of this procedure depends on the function of the LV, little is known regarding LV postoperative contractile state. The LV end-systolic pressure-dimension and wall stress-shortening (%AD) relationships, sensitive indexes of contractility, were studied during methoxamine-induced increases in afterload in eight patients with TGA and intact ventricular septa and in four patients with TGA and associated lesions. The patients with TGA and intact ventricular septa underwent pulmonary artery banding when they were between the ages 0.1 and 1.1 years (mean 0.4) to prepare the LV for anatomic correction. Age at repair ranged from 0.3 to 1.8 years (mean 1.0) and that at study from 1.7 to 6.7 years (mean 3.3). The interval from correction to study was 0.4 to 4.8 years (mean 2.3). End-systolic pressure was estimated from a calibrated suprasternal notch tracing. End-systolic dimension, wall thickness, and %zXD were determined by M mode and two-dimensional echocardiography, and end-systolic wall stress was then calculated. Results were compared with previously reported normal values. The pressure-dimension and wall stress-%AD relationships were normal in 10 of 12 TGA patients. The two patients with abnormal study results had TGA with intact ventricular septa and they underwent correction after 1.5 years of age. There was no relationship between contractile state and either interval from repair to study or age at study. Thus, LV contractility is normal in most patients with TGA who undergo anatomic correction. Circulation 69, No. 1, 106-112, 1984. WHEN COMPARED with the Mustard or Senning repairs for D-transposition of the great arteries (TGA), anatomic correction at the arterial level offers the advantage of normalizing the reversed role of the two ventricles.' 2 The importance of this advantage depends on the assumption that the left ventricle (LV) in transposition is normal before surgery and is not affected by the operative procedures. To date, the validity of these assumptions has not been adequately tested. We believe, therefore, that it is essential to critically evaluate LV contractility after anatomic correction. Recently the noninvasively determined slope value of the endsystolic pressure (Pes)-dimension (Des) relationship and the position of the end-systolic wall stress (ces)From the Division of Cardiovascular Surgery, Harefield Hospital, Harefield, Middlesex, England, and the Department of Cardiology, Children's Hospital Medical Center, the Cardiovascular Division Brigham and Women's Hospital, and the Departments of Medicine and Pediatrics, Harvard Medical School, Boston. Address for correspondence: M. H. Yacoub, F.R.C.S., Consultant Cardiac Surgeon, Harefield Hospital, Harefield, Middlesex, England. Received May 3, 1983; revision accepted Sept. 8, 1983. 106 shortening (%AD) relationship, as determined by methoxamine challenge, have been proposed to be sensitive indexes of LV contractile state in man.'4 This method has been used to detect preclinical abnormalities in children at risk for LV dysfunction.5-' The purpose of this article is to report on the use of this noninvasive method to evaluate LV contractile state after anatomic correction of TGA. Patients and methods Our patient population consisted of 12 children (10 boys and two girls) who had undergone anatomic correction for TGA (table 1). Only patients in close geographic proximity to the study site in Harefield, England were evaluated. Before surgery eight children had TGA with intact interventricular septa (IVSs) and four had additional defects (large ventricular septal defects in three, and aortopulmonary window in one). All of the children with TGA/IVSs underwent two-stage repair with initial pulmonary artery banding performed when they were from 0.1 to 1.1 years of age (mean 0.4). The patients' ages at repair ranged from 0.3 to 1.8 years (mean 1.0), and their ages at postoperative study ranged from 1.7 to 6.7 years (mean 3.3); the interval between definitive repair and study ranged from 0.4 to 4.8 years (mean 2.3). The technique used for anatomic correcCIRCULATION by gest on N ovem er 6, 2017 http://ciajournals.org/ D ow nladed from THERAPY AND PREVENTION-CONGENITAL HEART DISEASE TABLE 1 Data profile of study patients Duration Age at Interval, Age Age at of anatomic correction at Patient banding banding correction to study study (yr) (yr) (yr) (yr) (yr) 1 0.1 0.6 0.7 1.0 1.7 2A 0.3 1.4 1.7 3A 0.3 1.5 1.8 4 0.7 0.9 1.6 0.4 2.0 5 0.4 0.4 0.8 1.3 2.1 6 0.1 0.5 0.6 1.4 2.0 7 0.3 0.5 0.8 2.0 2.8 8 0.4 0.6 1.0 1.8 2.8 9' 0.2 4.8 5.0 10 0.1 0.7 0.8 4.4 5.2 1 1 1.1 0.7 1.8 3.4 5.2 12'\ 2.9 3.8 6.7 Mean 0.4 0.6 1.0 2.3 3.3 SD 0.4 0.2 0.8 1.4 1.8 AAssociated lesion present. tion has been described previously' 2 and consists of switchover anastomoses of the aorta and pulmonary arteries with transfer of the coronary ostia to the future systemic great artery. There was no evidence of LV or right ventricular outflow tract obstruction on physical examination, two-dimensional echocardiographic study, or postoperative cardiac catheterization in any of the patients. The nine control subjects ranged in age from 6 to 15 years (mean 9). They had normal cardiac examination results, electrocardiograms (ECGs), and intracardiac anatomy, as determined by M mode and two-dimensional echocardiography. Informed consent was obtained from the parents of each child studied. Experimental protocol. The experimental protocol was similar to that reported previously.3-7 A Cambridge medical instrument and Smith-Kline model E-20A ultrasound module with a 3.5 MHz transducer were used for M mode echocardiographic recordings. Two-dimensional echocardiographic imaging was performed with an Advanced Technical Laboratories model No. 851B real-time digital scanner. An external microphone was placed at the right upper sternal border area for phonocardiographic recording. Peak systolic and diastolic blood pressure measurements were made with the Dinamap 845 vital signs monitor (Critikon, Inc., Tampa, FL). This instrument can accurately estimate central aortic pressures over a wide range of systolic and diastolic values in both children and adults. 8 Subjects under 6 years of age were given light sedation with oral trimeprazine (2.5 mg/kg) followed in 1 hr by an intramuscular injection of papaveretum (0.33 mg/kg) and scopolamine (0.0067 mg/kg). All patients were premedicated with intravenous atropine (0.01 mg/kg) to abolish reflex cardiac slowing. Each subject underwent simultaneous recordings of systolic and diastolic blood pressures, anM mode echocardiogram of the left ventricle, a phonocardiogram, an indirect carotid or suprasternal notch pulse tracing, and an ECG under baseline conditions. Blood pressure was then elevated by the intravenous infusion of methoxamine beginning at 25 ,ug/kg/min and titrating upward to achieve the desired systolic blood pressure effect. The LV response to the methoxamine was assessed by repeating the recordings every 1 to 2 min during the infusion. When peak systolic pressure had increased by 30 to 60 mm Hg above baseline, the methoxamine infusion was discontinued. Peak pressure effect lasted 2 to 3 min. Parasternal long-axis and short-axis as well as subxiphoid views of the LV were obtained before initiation and immediately after cessation of the methoxamine infusion. Data points were excluded when heart rate varied by more than 10 beats/min from baseline. The LV enddiastolic dimension (Ded) was measured from the M mode echocardiogram at the onset of the Q wave of the ECG while the Des and wall thickness (hes) were measured at the first highfrequency component of the second heart sound. The measurements for Ded, Des, and hes were determined as the mean values for five cardiac cycles. LV %AD was calculated as: