J.M. Parsons

Influence of anatomic correction for transposition of the great arteries on myocardial perfusion: Radionuclide imaging with technetium-99m 2-methoxy isobutyl isonitrile

OBJECTIVES We sought to determine the incidence of late perfusion defects attributable to coronary artery mobilization in patients undergoing anatomic correction for complete transposition of the great arteries. BACKGROUND Anatomic correction (arterial switch procedure) is currently the surgical treatment of choice for complete transposition. From its conception, there has been concern about the impact on myocardial perfusion of the coronary artery mobilization and reimplantation involved in the correction. Previous studies have demonstrated myocardial perfusion defects in patients after correction, although a causal relation between coronary mobilization, and perfusion abnormality has not been established. METHODS In a case-comparison study designed to test this hypothesis, 29 children underwent imaging with technetium-99m 2-methoxy isobutyl isonitrile (technetium-99m mibi). Ten had undergone anatomic correction (arterial switch group; interval from operation 6.9 +/- 1.42 years [range 4.9 to 9.1]); 9 had required noncoronary open heart surgery for other cardiac lesions (post-bypass group; interval from operation 5.6 +/- 3.6 years [range 1.0 to 13.25]); and 10 had had no surgical procedure (control group). The latter group comprised children with atrial or ventricular septal defects who required a radionuclide study for shunt calculation. Planar studies were performed in all 29 children, and additional tomographic acquisition was achieved in 25. To assess reversibility of perfusion defects both an exercise and a rest planar study were performed in the arterial switch group. RESULTS Perfusion abnormalities were observed in seven of the nine children in the postbypass group and in all 10 children in the arterial switch group. The frequency of perfusion defects in these two groups was similar, with at least 25% of the tomographic segments reported being abnormal. The control group had significantly fewer defects than the other two groups (p = 0.02), with only 8% of the tomographic segments judged to be abnormal. In all except one patient in the arterial switch group, the segments reported as abnormal on the planar exercise study were either abnormal or equivocal on the rest study, indicating a fixed abnormality. CONCLUSIONS Although the precise etiology of these perfusion abnormalities cannot be defined from this study, these data suggest that their origin is related more to the insult of open heart surgery itself than to the coronary manipulation involved in the arterial switch procedure. The functional importance requires further study.

Determinants of hemodynamic results of balloon dilation of aortic recoarctation

Between October 1982 and May 1990, balloon dilation of aortic recoarctation was attempted in 27 patients. In 1 case dilation was not performed owing to suspected aortic perforation. The remaining 26 patients had 30 procedures. The age at the first dilation ranged between 2.6 months and 18.3 years. After dilation, systolic gradient decreased from 49 +/- 17 mm Hg to 20 +/- 17 mm Hg (p less than 0.001). A reduction of gradient to less than or equal to 20 mm Hg occurred after the first dilation in 17 of 26 (65%) patients. Residual gradients between 25 and 80 mm Hg were present in the remaining 9 patients. During follow-up of 2 months to 6.7 years, 5 of 17 patients with a good initial result developed further recoarctation (2 had successful redilation, 2 had reoperation, and 1 is awaiting repeat dilation). Of 9 patients with gradients greater than 20 mm Hg after the first dilation, 1 had successful redilation and 3 had reoperation. The remaining 5 patients are being managed conservatively. 2 patients developed aneurysms after dilation (1 immediately and the other at 2 months). In all, 15 patients (58%) had a good, and 11 (42%) a poor late hemodynamic result. Aortic diameters at different levels of the aortic arch and at the reconstructed isthmus (normalized to the aorta at the level of the diaphragm) were significantly higher in the group with a good late result than in that with a poor one. Balloon/aortic diameter ratio at diaphragm level also had a significant influence on the late results.

Double-outlet right ventricle: morphologic demonstration using nuclear magnetic resonance imaging.

Sixteen patients with double-outlet right ventricle, aged 1 week to 29 years (median 5 months), were studied with a 1.5 tesla nuclear magnetic resonance (NMR) imaging scanner. Two-dimensional echocardiography was performed in all patients. Thirteen patients underwent angiography, including nine who underwent subsequent surgical correction. Three patients underwent postmortem examination. Small children and infants were scanned inside a 32 cm diameter proton head coil. Multiple 5 mm thick sections separated by 0.5 mm and gated to the patients electrocardiogram were acquired with a spin-echo sequence and an echo time of 30 ms. A combination of standard and oblique imaging planes was used. Imaging times were less than 90 min. The NMR images were technically unsuitable in one patient because of excessive motion artifact. In the remaining patients, the diagnosis of double outlet right ventricle was confirmed and correlated with surgical and postmortem findings. The NMR images were particularly valuable in demonstrating the interrelations between the great arteries and the anatomy of the outlet septum and the spatial relations between the ventricular septal defect and the great arteries. Although the atrioventricular (AV) valves were not consistently demonstrated, NMR imaging in two patients identified abnormalities of the mitral valve that were not seen with two-dimensional echocardiography. In one patient who had a superoinferior arrangement of the ventricles, NMR imaging was the most useful imaging technique for demonstrating the anatomy. In patients with double-outlet right ventricle, NMR imaging can provide clinically relevant and accurate morphologic information that may contribute to future improvement in patient management.

Evaluation of pulmonary artery anatomy using magnetic resonance: The importance of multiplanar and oblique imaging

SummaryPulmonary artery anatomy was studied in 36 patients (age range 12 days to 12.83 years, mean 2.9 years) with right ventricular outflow tract obstruction over a 3-year period using a 1.5 Tesla Magnetic Resonance system. Gated spin-echo sequences were obtained in each patient. Image planes used were straight and oblique transverse, oblique coronal, and oblique sagittal. The studies were analyzed retrospectively and comparative angiographic, surgical, and postmortem data was available in all cases. As previously noted with other imaging modalities, multiple views and oblique cuts were found to increase significantly the quality and accuracy of the information acquired. In 12 of the 15 patients who had axial and coronal imaging of both branch pulmonary arteries, the pulmonary arteries were unequivocally demonstrated to at least the first hilar branch. However, early in our experience we missed a number of branch stenoses that developed following surgical anastomoses. These mistakes were caused by inadequate or inappropriate slice acquisition. Magnetic resonance is an important technique for imaging pulmonary arteries. Careful use of the appropriate imaging planes is essential for accurate demonstration of the anatomy.

The use of magnetic resonance imaging in the investigation of infants and children with congenital heart disease: current status and future prospects

This review concentrates predominantly on aspects of cardiac imaging, since this is the major application of the technique at the current time, but also mentions some of the areas where the additional magnetic resonance techniques have been used or may be of potential benefit

Recurrence of aortic coarctation following repair by re-implantation of the subclavian artery

Four patients mean age six months, range 11 days to 2 years, underwent repair of aortic coarctation by the technique of reimplantation of the subclavian artery (Mendonca repair). All developed re-coarctation within six months of an initially successful repair.

Doppler evaluation of superior caval venous pathways after Mustard and Senning operations

Doppler waveforms from the superior caval vein were analysed to evaluate the patency of superior caval venous pathways following venous redirection (Mustard and Senning) operations for complete transposition. The group consisted of 26 unselected survivors of Mustard (9 patients) and Senning operations (17 patients). Patients were examined a mean of 5.9 (range 0.1-15.3) years following operation and their age at study ranged from 0.4-25.3 years, mean 7.3 years. Doppler waveforms were correlated with digital subtraction angiograms, which were performed in every patient within 24 hours of the Doppler study. Totally occluded superior caval venous pathways were identified in 3 patients with digital subtraction angiography. The remaining patients had angiographically patent pathways. In the 23 patients with patent pathways, Doppler waveforms demonstrated an initial systolic peak smaller than a second diastolic peak. In the 3 patients with totally occluded pathways, the pattern of the waveform was reversed, with the systolic larger than the diastolic peak. Doppler examination of the superior caval vein is a quick and simple bedside method of accurately determining patency of superior caval venous pathways after atrial redirection procedures for complete transposition.

Hypercyanotic spells caused by antegrade catheterization of the pulmonary arteries in tetralogy of Fallot: fact or fiction?

Between January 1985 and March 1990, 66 children with the tetralogy of Fallot underwent 85 cardiac catheterization procedures. The mean age at first procedure was 2.5 years (range 0.1–;14.4 years) and the mean weight was 10.4 kg ( range 2.4–36.0 kg). Diagnostic cardiac catheterization was performed in 60 procedures and balloon dilatation in 25. Hypercyanotic spells had occurred prior to 24 (28%) of the procedures (all the patients being on propranolol) and a systemic-to-pulmonary arterial shunt had been constructed before 28 (33%) procedures. Of the procedures, 54 (64%) were performed under local and 31(36%) under general anesthesia. The pulmonary trunk was entered antegradely in 52 procedures, retrogradely through a shunt in 6 and not entered in 27. Balloon dilatation was performed under general anesthesia on 25 occasions. No procedure was abandoned because of a cyanotic spell. Nine (11%) spells occurred during 86 procedures, one of the procedures being postponed because ofa spell occurring after premedication, the procedure and not, therefore, continuing to catheterization. Five spells occurred before the catheter was positioned in the heart, 2 spells occurred during catheterization. Of the spells, eight occurred during procedures in children who had not had previous shunts. Antegrade entry into the pulmonary trunk in the group with shunts was associated with no spells compared with 6/38 (18%) in the group not having undergone surgery (p

Dangerous recurrence of arrhythmia following withdrawal of flecainide

Abstract We report the case of a five-year-old boy who developed sustained supraventricular tachycardia associated with collapse and hypotension 9 days after withdrawal of flecainide.

Palliation of tetralogy of fallot by balloon dilation: Efficacy and safety

Seventeen patients with tetralogy of Fallot (TOF) were palliated by balloon dilation of the right ventricular outflow tract (RVOT). Their mean age was 9.8 months and mean weight 6.7 kg. Nine had hypercyanotic spells and eight had worsening cyanosis and polycythaemia. Successful dilation was achieved in 16 patients. The mean pulmonary valve annulus diameter measured angiographically was 8.8 mm and the mean balloon/annulus ratio was 1.5. Aortic oxygen saturation increased from mean (±SD) of 79(12)% before to 90(7)%. Pulmonary artery saturation rose from 64(12)% to 80(6)%. The systolic pressure gradient across the RVOT fell from 72.7(18.6) to 59.7(20.4) mmHg. One patient had a cardiac arrest prior to dilation and died shortly after the procedure. Four patients had cyanotic spells on induction of anaesthetic and one during the procedure. One patient had infundibular perforation by guide wire without any adverse sequelae and a Blalock-Taussig (BT) shunt was performed electively.Follow-up has ranged from 6–19 months with adequate palliation in all but five requiring a second procedure and one subsequently a third. Seven have undergone surgical correction and two patients unsuitable for correction had a BT shunt. In conclusion, balloon dilation of RVOT offers adequate palliation prior to surgery.