A 31-year-old patient previously underwent a Mustard operation presented with palpitations. Atrial tachycardia and paroxysmal atrial fibrillation were documented on the surface electrocardiogram. Under the guidance of a three-dimensional electroanatomic mapping system, ablation of the isolated left-sided pulmonary vein and a cavo-tricuspid isthmus-dependent intra-atrial macro re-entry circuit eliminated atrial tachycardia and paroxysmal atrial fibrillation without the recurrence of atrial tachyarrhythmia.

Background: At present, a considerable number of patients survive who underwent an atrial switch operation for correction of complete transposition. Our study aimed to assess their long-term exercise performance and the serial evolution of cardiac function. Methods: We studied 22 patients 5 to 17 years after an atrial switch operation, and followed them serially for 3.5 ± 2 years after the first evaluation. Cardiorespiratory exercise function was assessed by analysis of gas exhange and by determination of the ventilatory anaerobic threshold. Echocardiography was performed on all evaluations. Results: All patients were in Class I of the classification of the New York Heart Association at all assessments. Ventilatory anaerobic threshold, however, was significantly lower than normal. It averaged 77.9% ± 13.7 of the normal mean value at the initial evaluation, and remained stable when re-evaluated later (76.2 ± 13.7%). At the initial study, the increase in oxygen uptake during graded exercise was below the 95% confidence limit in 6 of the patients, and was below this level in 10 patients at re-assessment. The subnormal values for oxygen uptake during submaximal exercise were associated with moderate to severe haemodynamic dysfunction. At echocardiography, 15 of 17 patients studied twice had mild to moderate right ventricular dilation and tricuspidregurgiation, which remained virtually the same at reasssesment. A stable sinus rhythm was initially present in 17 patients, and persisted in 15 patients during follow-up. Conclusion: At medium term follow-up, cardiorespiratory exercise performance remains stable in patients after atrial switch repair. Serial exercise testing appears useful, because in individual patients in the present study, a decreasing exercise tolerance correlated with development of haemodynamic sequels.

Long-term follow-up studies after intraatrial repair for complete transposition have shown postoperative morphologic and hemodynamic abnormalities in many patients which often require reevaluation and therapeutic intervention. The purpose of this study was to assess, using magnetic resonance imaging, the presence and extent of late postoperative complications in a large cohort of 44 patients undergoing repair with the Mustard procedure. Of these 34 had an intact ventricular septum with or without obstruction of the left ventricular outflow tract, while 10 had an associated ventricular septal defect. Transverse spin-echo and gradient-echo images were acquired of the entire heart from the diaphragm to the bifurcation of the pulmonary trunk. Additional oblique images were acquired for better visualization of venous connections. Abnormal findings were diagnosed by visual inspection of spin-echo and gradient-echo images, and diagnoses were compared to previous findings at cardiac catheterization. On magnetic resonance imaging, a baffle leak was seen in eight patients, two had pulmonary venous obstruction, four had obstruction at the caval veins, 23 had obstruction of the left ventricular outflow tract and 18 had tricuspid regurgitation. Cardiac catheterization showed a leak across the baffle in 16, pulmonary venous obstruction in two, obstruction at the caval veins in four, obstruction of the left ventricular outflow tract in nine, and tricuspid regurgitation in nine. We conclude that combined spin-echo and gradient-echo magnetic resonance imaging provides extensive noninvasive assessment of postoperative sequels and residuals in patients after the Mustard procedure for complete transposition.

Stenoses of the systemic venous pathways are a potentially dangerous complication after the Mustard operation. The acute and intermediate-term efficacy of balloon dilation of these stenoses has not previously been studied in a large group of patients. A retrospective analysis of clinical and angiographic data, with prospective clinical and echocardiographic follow-up, was performed in a consecutive group of 25 patients (17 male, 8 female) who underwent balloon dilation of the superior or inferior caval venous pathways. For 17 dilations of stenoses in the superior pathway, the mean pressure gradient decreased from 9.1±5.7 to 3.4±2.3 mm Hg (p<0.01), while the diameter of the stenosis increased from 5.9±2.9 to 11.2±3.0 mm (p<0.01). For 25 dilations of the inferior pathway, the mean gradient decreased from 4.3±1.8 to 1.4±1.1 mm Hg (p<0.01), while the diameter of the stenosis increased from 7.3±1.5 to 10.6±2.3 mm (p<0.01). Over a median follow-up of 3.5 years, 16 patients have been without symptoms or signs suggestive of recurrence of stenoses. In the remaining nine patients, 11 further procedures were performed at a median of 3.1 years after initial dilation. In five patients who had previously undergone dilation of the superior (3), inferior (1) or both (1) pathways, further dilations of the same pathway(s) and/or stent implantations were performed. Three patients, including one in whom superior caval venous stenosis had recurred, had developed a new stenosis of a previously undilated pathway, while in two patients no further dilations were required. Balloon dilation offers an alternative to reoperation for stenoses of the systemic venous pathways after the Mustard operation, and appears to provide satisfactory intermediate-term palliation. Recurrences of stenoses in previously dilated pathways, and new stenoses in previously unobstructed pathways, are commonly seen at follow-up. Alternative measures, such as placement of stents, need to be considered in the long-term management of these patients.

Atrial correction for complete transposition involves a potential risk of later development of right ventricular dysfunction. To determine the reasons contributing to such systemic ventricular failure, radioisotope first-pass and SPECT perfusion studies at rest after one dose of Technetium-99m MIBI were performed in 26 asymptomatic patients, 5.9±2.7 years after a Mustard or Senning repair. Mean age at operation was 4.3±4.3 years. All patients were followed with 24-hour Holter monitoring and echocardiography. Normal perfusion was observed in 11 patients with a mean age at operation of 2.25±1.8 years and mean right ventricular ejection fraction of 49.0±8.7%. Perfusion defects were found in 15 patients with a mean age at operation 5.8±4.8 years (p<0.05) and mean right ventricular ejection fraction of 43.2±9.3% (NS). In the group of older patients, 10 had extensive perfusion defects with significantly lower right ventricular ejection fraction (39.7±9.3%, p<0.05) and even older mean age at the surgery (7.1±5.6 years p<0.02). Mild or moderate tricuspid regurgitation was found significantly more frequently in those patients with perfusion defects (73%) than in the group of younger patients (36.3%), p<0.05. There was no difference in the frequency and type of arrhythmias, nor in the extent of follow-up, between the two groups. We conclude that, in patients undergoing surgery at an older age, it is more common to find perfusion defects and, often, lower right ventricular ejection fraction. Perfusion abnormalities found in such asymptomatic patients may be a result of several factors: impaired right ventricular function as a consequence of pressure and volume overload, enhanced myocardial fibrosis, or long-lasting preoperative hypoxemia and tricuspid valvar dysfunction secondary to ventricular dilation. We suggest that the perfusion defects observed in this study may be a better indicator of systemic ventricular impairment.