In patients with congenitally corrected transposition of the great arteries (ccTGA) and hemodynamically significant concomitant lesions, physiologic repair may be undertaken, in which the circulation is septated but the morphologic right ventricle (RV) remains the systemic ventricle. Patients without significant concomitant lesions may be observed without surgery, with a similar physiologic result. We compared cardiovascular magnetic resonance measures of ventricular size and function in patients with physiologically repaired and unrepaired ccTGA. Patients with ccTGA who underwent cardiovascular magnetic resonance at our center between September 2007 and July 2019 were analyzed. In 38 patients identified (12, physiologically repaired; 26, unrepaired; mean age 34.5 [18.7 to 52.0] years), there was a higher proportion of RV ejection fraction ≤45% in physiologically repaired (75% vs unrepaired 35%, p = 0.02). Physiologically repaired patients had worse left ventricle global longitudinal strain (−14.9% ± 5.0% vs unrepaired patients −18.4% ± 2.7%, p = 0.04). The difference in tricuspid regurgitant fraction between groups did not achieve statistical significance (physiologically repaired 27.4 ± 11.1% vs unrepaired patients 19.2 ± 13.0%, p = 0.08). Evaluation for late gadolinium enhancement was more commonly undertaken in physiologically repaired patients (8 of 12 vs unrepaired 7 of 26, p = 0.03) and present more frequently in the left ventricle in physiologically repaired patients in patients evaluated (6 of 8 vs unrepaired 0 of 7, p = 0.01). In conclusion, ventricular function is decreased in patients with ccTGA undergoing physiologic repair compared with those without previous surgery. These cohorts should be considered separately when using ventricular function as an outcome. RV dysfunction is concerning for long-term outcomes following physiologic repair.
Congenitally corrected transposition of the great arteries (ccTGA) is defined by atrioventricular discordance and ventriculoarterial discordance such that the morphologic right ventricle (RV) is the systemic ventricle. Over time, the RV may become dilated and dysfunctional, leading to tricuspid valve regurgitation, arrhythmia, and heart failure. Management strategies are variable. For patients with concomitant structural cardiovascular abnormalities, physiologic repair may be undertaken, in which structural lesions are repaired but the RV is maintained as the systemic ventricle. For patients without additional significant structural abnormalities, monitoring without intervention may be offered. Finally, an anatomic repair can be performed; with this strategy, venous return and outflows are arranged such that the morphologic left ventricle (LV) becomes the systemic ventricle and the RV the subpulmonary ventricle. Differences in outcomes between patients who underwent anatomic and physiologic repair have been studied; however, it is not well-known to what extent ventricular function differs in patients who underwent physiologic repair compared with those without previous surgery. , Moreover, these patients are often grouped in cohorts used for comparisons. In this study, we compared cardiovascular magnetic resonance (CMR) measures of ventricular size and function between patients with physiologically repaired and unrepaired ccTGA. We hypothesized that patients who underwent physiologic repair would have decreased RV function and increased tricuspid regurgitation.
Methods
Patients with ccTGA who underwent CMR at our center between September 2007 and July 2019 were identified. Patients were excluded from analysis if they underwent anatomic repair, single ventricle palliation, only pulmonary artery band or shunt placement as surgical interventions at the time of CMR, received the CMR as a preoperative study before anatomic repair or were <4 years of age at the time of CMR. Patients <4 years of age were excluded as we sought to evaluate the long-term effect of interventional strategies on ventricular function. If multiple CMR studies were performed on a patient, only the most recent study was selected for analysis. This study was approved by the institutional review board, and the requirement for informed consent was waived for this retrospective study.
All CMRs were completed on a 1.5 Tesla MRI scanner (Achieva or Ingenia; Philips, Best, the Netherlands). Breath-hold,electrocardiogram-gated, steady-state free-precession cine sequences were obtained. Standard cine imaging obtained in all patients included a 4-chamber stack, a short axis stack through the ventricles, and 2-chamber views of the systemic venous atrium and LV and the pulmonary venous atrium and RV, with additional imaging obtained as required to evaluate the clinical questions posed. Thirty heart phases were acquired for each cine sequence. Ventricular volumes and mass were measured using the short axis stack, using QMass software (Medis, Leiden, The Netherlands), with the ventricular septum included in the mass measurement of the morphologic RV. For patients who were evaluated for late gadolinium enhancement (LGE), 0.2 mmol/kg of gadoteridol, with maximum of 40 mL (ProHance; Bracco, Monroe Township, New Jersey) was administered, and LGE images were obtained using a breath-hold, phase-sensitive inversion recovery sequence in the 4-chamber and short-axis planes beginning 12 to 15 minutes after contrast was administered.
Patients were divided into 2 groups: those who had undergone physiologic repair and those who had not received any previous cardiovascular surgical intervention. Physiologic repair was defined as the operation undertaken to separate the systemic and pulmonary circulations or to address hemodynamically significant lesions, resulting in maintenance of the RV as the systemic ventricle, independent of whether an individual patient had a previous palliative intervention such as a systemic to pulmonary artery shunt. Baseline anthropomorphic data were collected for each group. Measures of ventricular size and function were recorded from CMR reports. Correlation between LV and RV EF was evaluated for each group. Reported quantitative measures of tricuspid regurgitation, aortic regurgitation, and pulmonary (including conduit) regurgitation were recorded. For patients with tricuspid regurgitant fraction calculated using 2 methodologies (e.g., by comparing RV stroke volume to aortic outflow, or by comparing tricuspid inflow to aortic outflow), an average was taken of the 2 reported regurgitant fractions and used as the patient’s measured regurgitant fraction. Patients with >10% difference in the measured tricuspid regurgitant fraction if measured by 2 techniques were noted. The presence of LGE was recorded in patients who underwent LGE imaging and LGE location was categorized as occurring within the LV myocardium, RV myocardium, or ventricular septum. When present, LGE of ventricular trabeculations was not considered to represent LGE of the ventricular myocardium. For patients in whom contrast was not administered during the most recent CMR, previous studies were reviewed. If a previous CMR was obtained during which LGE was assessed, then this study was included for comparative analysis of the presence and location of LGE between groups. The presence of residual or native unrepaired shunting lesions and the ratio of pulmonary to systemic blood flow were recorded from the CMR report for each patient as available. For physiologically repaired patients, the date and procedural detail of the initial physiologic repair were recorded along with additional operations performed before this study CMR.
Strain was calculated by a single user Hunter C. Wilson, (HCW) using tissue tracking software (cvi42, Circle Cardiovascular Imaging, Calgary, Alberta, Canada), as described by Truong et al. Longitudinal strain was calculated by drawing contours around the LV and RV endocardium and epicardium in diastole from sequences in the cine 4-chamber stack, with care taken to avoid trabeculations ( Figure 1 ). Circumferential strain was similarly calculated by drawing contours around the LV and RV endocardium and epicardium in diastole from sequences in the short axis stack so that the entire ventricle was covered. The ventricular septum was included with the morphologic LV for strain calculations. Tissue tracking was qualitatively assessed for each patient to ensure adequate tracking of the endocardial and epicardial contours.
Data are reported as frequency with percentage for categorical variables and median with interquartile range (IQR) or mean±standard deviation for continuous variables. Univariate comparisons were made between physiologically repaired and unrepaired patients using chi-square test or Fisher’s exact test for categorical variables and Wilcoxon rank sum test or 2-sample t test for continuous variables. Correlation between LV and RV EF was evaluated for each group using Pearson correlation coefficient, r. A p value <0.05 was considered statistically significant. All analyses were performed using SAS version 9.4 (SAS Institute, Cary, North Carolina).
Results
A total of 38 patients were included, 12 of whom underwent physiologic repair and 26 of whom had no previous cardiovascular surgical intervention. Group characteristics were similar at baseline ( Table 1 ). For patients in the physiologically repaired group, the median age at initial repair was 4.3 (IQR 1.6 to 6.3) years. The most common initial operation performed for physiologic repair was ventricular septal defect (VSD) repair with placement of a left ventricle pulmonary artery (LV-PA) conduit ( Table 2 ). A total of 7 of 12 patients underwent surgical reintervention at a median of 9.9 (IQR 2.9 to 13.4) years following physiologic repair. Each of these patients had at a minimum replacement of their LV-PA conduit as their subsequent operation.
| Characteristics | Repaired(N=12) | Unrepaired(N=26) | P -value * |
|---|---|---|---|
| Male | 6 (50%) | 12 (46%) | 0.83 |
| White | 12 (100%) | 23 (89%) | 0.54 |
| Age at CMR (years) | 33 (24-42) | 35 (17-54) | 0.80 |
| Weight at CMR (kg) | 78 ± 23 | 74 ± 35 | 0.68 |
| Height at CMR (cm) | 168 ± 12 | 164 ± 17 | 0.43 |
| Body surface area at CMR (m 2 ) | 1.89 ± 0.30 | 1.80 ± 0.48 | 0.53 |
⁎ p value derived from chi-square test or Fisher’s exact test for categorical variables and Wilcoxon rank sum test or two-sample t test for continuous variables. Data are presented as n (%) for categorical variables and median (interquartile range) or mean ± standard deviation for continuous variables. CMR = cardiovascular magnetic resonance imaging.
| Patient | Sex | Age at Repair (years) | Operation |
|---|---|---|---|
| 1 | M | 0.6 | VSD repair + LV-PA conduit + tricuspid valve repair |
| 2 | M | 0.6 | VSD repair + LV-PA conduit |
| 3 | F | 1.2 | VSD repair + LV-PA conduit + ASD repair |
| 4 | F | 2.1 | VSD repair + LV-PA conduit + ASD repair |
| 5 | M | 2.9 | VSD repair + LV-PA conduit |
| 6 | M | 4.0 | VSD repair + LV-PA conduit |
| 7 | M | 4.6 | VSD repair + LV-PA conduit |
| 8 | F | 6.0 | VSD repair + LV-PA conduit + ASD repair + LPA angioplasty |
| 9 | M | 6.2 | VSD repair + LV-PA conduit |
| 10 | F | 6.4 | VSD repair + LV-PA conduit + ASD repair |
| 11 | F | 20.9 | VSD repair + LV-PA conduit |
| 12 | F | 53.7 | Tricuspid valve replacement |
Table 3 lists comparisons of RV and LV size and function measurements between groups. A higher proportion of physiologically repaired patients had an abnormal RV EF, with a lower mean RV EF also noted, although this difference did not achieve statistical significance. RV longitudinal and circumferential strain were not significantly different between groups. LV circumferential strain was similar between groups; however, LV longitudinal strain was worse in physiologically repaired patients. There was a significant correlation between LV and RV EF in unrepaired patients (r = 0.67, p = 0.0002), although no such correlation was identified in physiologically repaired patients (r = 0.22, p = 0.49).
