Asymmetric distribution of the pulmonary blood flow between the right and left lungs in d-transposition of the great arteries

Pediatric three-dimensional quantitative cardiovascular computed tomography

High-resolution, isotropic, 3-dimensional (D) data from pediatric cardiovascular computed tomography (CT) offer great potential for the accurate quantitative evaluation of pediatric cardiovascular and pulmonary vascular diseases. Recent pilot studies using pediatric 3-D cardiovascular CT have shown promising results in assessing cardiac function in conditions such as tetralogy of Fallot, cardiac defects with a hypoplastic ventricle, Ebstein anomaly, and in quantifying myocardial mass. In addition, the quantitative assessment of pulmonary vascularity is useful for evaluating differential right-to-left pulmonary vascular volume ratio, the effectiveness of pulmonary angioplasty, and predicting pulmonary hypertension. These initial experiences could broaden the role of pediatric cardiovascular CT in clinical practice. Furthermore, the current barriers to its widespread use, pertinent solutions to these problems, and new applications are discussed. In this review, the 3-D quantitative evaluations of cardiac function and pulmonary vascularity using high-resolution pediatric cardiovascular CT data are illustrated.

Automated analysis method to assess pulmonary blood flow distribution using conventional X-ray angiography

Quantitative assessment of the right-to-left ratio of pulmonary blood flow distribution is important for determining the clinical indications for treating pulmonary arterial branch stenosis. A novel theory was recently proposed that can be used to quantitatively assess the right-to-left ratio on conventional X-ray angiography images. In the proposal, further developments were indicated, especially automated calculation. In this study, a new automated algorithm was developed. In the X-ray image, regions of interest were set in right and left lung, and time-signal intensity curves were measured. The new automated algorithm is applied to determine the optimal time window for the analysis of the time-signal intensity curve and to calculate the slope of the curve in the optimized time window. The right-to-left ratios in seven consecutive patients calculated by the new automated algorithm were compared to those calculated by lung perfusion scintigraphy. The ratios were in good agreement with linear regression with a slope of 1.27 and a Pearson correlation coefficient of 0.95. The processing time was less than 10 s, which is one-eighth of the manual processing time. The new automated algorithm is accurate, stable, and fast enough for clinical use in the real world.

The behavior of residual pulmonary artery gradient after arterial switch operation: A longitudinal data analysis

OBJECTIVE

The arterial switch operation (ASO) is the standard treatment for the transposition of the great arteries. The timely variation in the residual pressure gradient across the pulmonary arteries is ill-defined. This study is aimed to study the progressive changes in the pressure gradient across the pulmonary valve and pulmonary arteries after ASO.

METHODS

All eligible patients for this study who underwent ASO between 2000 and 2019 were reviewed. Transthoracic echocardiography was used to estimate the peak pressure gradient across the pulmonary artery and its branches. The primary outcome was the total peak pressure gradient (TPG) which is the sum of peak pressure gradients across the main pulmonary artery and pulmonary artery branches. Furthermore, longitudinal data analyses with mixed-effect modeling were used to determine the independent predictors for the changes in the pressure gradient.

RESULTS

Three hundred and nine patients were included in the study. Over a 17-year follow-up, the freedom from pulmonary stenosis reintervention was 95% (16 out of the 309 patients underwent reintervention = 5%). The longitudinal data analyses of serial 1844 echocardiographic studies for the included patients revealed that the TPG recorded in the first postoperative echocardiogram across pulmonary valve, right and left pulmonary artery branches was the most significant predictor for reintervention.

CONCLUSION

The total peak gradient measured in the first postoperative echocardiogram is the most important predictor for reintervention. We propose that a total peak gradient in the first postoperative echocardiography of 55 mm Hg or more is a predictor for reintervention.

Improved systemic saturation after ventricular assist device implantation in a patient with decompensated dextro-transposition of the great arteries after the Fontan procedure

We report the successful implantation of a HeartMate II left ventricular assist device after a failed Fontan procedure in a patient with dextro-transposition of the great arteries. The patient had developed significant intrapulmonary arteriovenous shunting. Despite the theoretical risk of worsening intrapulmonary shunting due to the decrease in systemic vascular resistance after device implantation, our patient did well. He was discharged from the hospital in stable condition and had better oxygen saturation than before the device was implanted. To our knowledge, ours is the 2nd report of the use of a ventricular assist device after the failure of a Fontan procedure, and the first report concerning the effect of ventricular assist device implantation on intrapulmonary shunting.

Comparison of bilateral pulmonary arterial level and diameter in transposition of the great arteries

In normal anatomy, the left pulmonary artery (LPA) is usually situated higher than the right pulmonary artery (RPA); however, transposition of the great arteries (TGA), the LPA is not always situated higher than the RPA. This study was performed to clarify the relative position of the RPA and the LPA in transposition of the great arteries (TGA) as well as the implications. We reviewed 101 angiograms of patients with TGA (age 4.1 ± 1.2 months). The width of the RPA, the LPA, and the pulmonary trunk (PT) were measured just before their first branch in the frontal view. They were classified into four groups according to the ratio between the RPA and the PT (RPA/PT). The initial courses of the LPA and the RPA were compared and defined according to their height in the frontal view, and the preferential flow (or not) to the RPA was recorded. The equation of hydrodynamics was applied to evaluate the bifurcation angle. Both PAs were the same size in all cases. Forty-eight patients (47.5 %) had a RPA/PT diameter ratio < 0.49. The LPA coursed higher than the RPA in the majority of cases (81 [80.2 %]); in a minority of cases the LPA and RPA were at the same level (6 [5.9 %]); and in some cases the RPA coursed higher than the LPA (14 [13.9 %]). Patients with a high degree of PA hypoplasia tended to have both PAs at the same level or a higher-positioned RPA. Autopsy (1 of 3 cases) showed a posterior ridge against the bronchus in the higher RPA. Hydrodynamic calculation showed that the greater the angle between the RPA/PT, the greater the preferential flow. Preferential flow to the RPA in TGA did not necessarily result in LPA hypoplasia before its first branch. Higher RPA position relative to the LPA was associated with greater flow in it against the posterior bronchus. This situation was more prevalent in patients with severe PA hypoplasia.

Pulmonary venous flow index as a predictor of pulmonary vascular resistance variability in congenital heart disease with increased pulmonary flow: a comparative study before and after oxygen inhalation

AIMS

There is no definitive and reliable echocardiographic method for estimating the pulmonary vascular resistance (PVR) to differentiate persistent vascular disease from dynamic pulmonary hypertension. The aim of this study was to analyze the relationship between the pulmonary venous blood flow velocity-time integral (VTIpv) and PVR.

METHODS AND RESULTS

Eighteen patients (10 females; 4 months to 22 years of age) with congenital heart disease and left to right shunt were studied. They underwent complete cardiac catheterization, including measurements of the PVR and Qp:Qs ratio, before and after 100% oxygen inhalation. Simultaneous left inferior pulmonary venous flow VTIpv was obtained by Doppler echocardiography. The PVR decreased significantly from 5.0 ± 2.6 W to 2.8 ± 2.2 W (P = 0.0001) with a significant increase in the Qp:Qs ratio, from 3.2 ± 1.4 to 4.9 ± 2.4 (P = 0.0008), and the VTIpv increased significantly from 22.6 ± 4.7 cm to 28.1 ± 6.2 cm (P = 0.0002) after 100% oxygen inhalation. VTIpv correlated well with the PVR and Qp:Qs ratio (r = -0.74 and 0.72, respectively). Diagnostic indexes indicated a sensitivity of 86%, specificity of 75%, accuracy of 83%, a positive predictive value of 92% and a negative predictive value of 60%.

CONCLUSION

The VTIpv correlated well with the PVR. The measurement of this index before and after oxygen inhalation may become a useful noninvasive test for differentiating persistent vascular disease from dynamic and flow-related pulmonary hypertension.

Catheters, wires, tubes and drains on postoperative radiographs of pediatric cardiac patients: the whys and wherefores

Surgical treatment of congenital heart disease has advanced dramatically since the first intracardiac repairs in the mid-20th century. Previously inoperable lesions have become the focus of routine surgery and patients are managed successfully in intensive care units around the world. As a result, increasing numbers of postoperative images are processed by departments of radiology in children's hospitals. It is important that the radiologist accurately documents and describes the catheters, wires, tubes and drains that are present on the chest radiograph. This article reviews the reasons for the placement and positioning of perioperative equipment in children who have surgical repair of atrial septal defect, ventricular septal defect or transposition of the great arteries. Also included are a brief synopsis of each cardiac anomaly, the surgical procedure for its correction, and an in-depth discussion of the postoperative chest radiograph including illustrations of catheters, wires, tubes and drains.

Morphologic Substrates for First-Branch Pulmonary Arterial Hypoplasia in Transposition of the Great Arteries

BACKGROUND

Distal right-sided outflow obstruction remains a problem after arterial switch operation. We studied the anatomical features of the pulmonary trunk (PT) and its branches that are susceptible to right and left pulmonary arterial (RPA and LPA) hypoplasia in transposition of the great arteries (TGA).

METHODS

One hundred and one angiograms of TGA performed between 1981 and 1996 were viewed, and Polaroid photos were taken at end-systole. The diameters of RPA, LPA, PT, duct, ascending aorta, and angles between PA and PT were measured, and the ductal flow direction was recorded.

RESULTS

Forty-eight cases (47.5%) had a PA/PT diameter ratio (both PAs had same size) below 0.49. A smaller PA/PT was significantly related to posterior inclination of the proximal PT [narrower right (r = 0.50, p < 0.00001) and left (r = 0.48, p < 0.00001) PA-PT angle in lateral view] and a larger duct (r = 0.37, p < 0.0001). Eighteen patients had a follow-up angiogram after a mean period of 8.5 months. Those with a closed duct had evident PA growth (n = 12, 0.51 +/- 0.09 to 0.74 +/- 0.17, p < 0.0001), but four patients with an attenuated duct had no significant change (0.58 +/- 0.06 to 0.68 +/- 0.08, p = NS), and one with a persistent large duct had even regression of PA/PT (0.36-0.19). The direction of ductal flow was toward the aorta during early systole on cineangiogram.

CONCLUSIONS

First-branch PA hypoplasia, which is frequently seen in TGA, was related to the right-to-left shunt through a duct resulting in hemodynamic starvation, and to posterior inclination of the proximal PT in this setting. Natural regression of the duct facilitated PA growth.

Arterial switch procedure for D-transposition of the great arteries: quantitative midterm evaluation of hemodynamic changes with cine MR imaging and phase-shift velocity mapping-initial experience

PURPOSE

To evaluate cine magnetic resonance (MR) imaging and phase-shift velocity mapping for assessment of the hemodynamic relevance of stenotic segments or specific hemodynamic changes in the great vessels after an arterial switch procedure for correction of D-transposition of the great arteries.

MATERIALS AND METHODS

Twenty consecutive patients (age range, 2-17 years) with an acoustic window that was insufficient for Doppler transthoracic echocardiography were included in the study. Flow and diameter measurements of the pulmonary arterial trunk and its primary branches were performed with phase-shift velocity mapping and cine MR imaging.

RESULTS

There were good correlations between pressure gradients in the pulmonary arteries estimated with MR imaging and those measured with Doppler echocardiography (r = 0.83, n = 15) and cardiac catheterization (r = 0.90, n = 13). Cine MR imaging revealed that the diameters of the right and left pulmonary arteries decreased with the expansion of the aorta during systole, which increased the peak velocity. This temporary stenosis was more severe in the right than in the left pulmonary artery and was accompanied by a significantly (P <.05) lower volume flow in the right artery.

CONCLUSION

The anatomic situation after arterial switch repair tended to produce temporary stenoses in the primary pulmonary arterial branches, with significant changes in hemodynamics. These changes may affect the long-term outcome and go undetected with other imaging modalities.

Late onset of pulmonary hypertension after successful Mustard surgery for d-transposition of the great arteries

Late-onset pulmonary hypertension is a serious complication of Mustard repair for d-transposition of the great arteries. This debilitating complication occurs in 7% of patients who survive to adulthood, even in the face of normal or near-normal postoperative pulmonary pressure.

Heart rate and oxygen uptake response to exercise in children with low peak exercise heart rate

Normal children achieve the same increase of oxygen uptake (VO2) in response to exercise even though resting and submaximal exercise heart rates vary greatly as a function of age, body size and physical conditioning. To determine whether the VO2 response to exercise is altered when heart rate is significantly reduced by heart disease, we compared 78 children who achieved a peak exercise heart rate of less than or equal to 150 beats/min to 201 controls of similar body size and normal peak exercise heart rates of greater than or equal to 180 beats/min. All performed incremental (16.4 Watts/min) maximal cycle exercise. Separate analysis of males and females included heart rate, power (kg-m/min, Watts/kg), VO2 (ml/min, ml/min per kg), O2 pulse (VO2/heart beat), VE (l/min) and R (VCO2/VO2) at rest and during the 1st, 4th and last minute of exercise. Patients with low peak exercise heart rates had also lower resting submaximal exercise heart rates than controls. VO2 at comparable exercise levels did not differ from controls and consequently O2 pulse was greater in the patients than controls at rest and at all levels of exercise. A consistent gender difference was only found in controls where males achieved a higher VO2 and lower heart rates at comparable levels of exercise. The data show a normal exercise VO2 despite significantly lower heart rates. These findings cannot be explained by an increased arteriovenous difference alone and suggest that the patients retained the ability to effectively modulate stroke volume.

Fate of long-term survivors of Mustard procedure (inflow repair) for simple and complex transposition of the great arteries

Between 1967 and 1976, 106 children with transposition of the great arteries (TGA) (55 simple, 51 complex) survived the Mustard procedure. Late death occurred in 8 patients (1 simple, 7 complex TGA). Cardiac arrhythmia developed in 31 patients, 6 of whom required a permanent pacemaker. Postoperative cardiac catheterization showed mild superior vena cava obstruction in 4 patients, mild pulmonary venous obstruction in 3, and baffle leak in 4. Only 1 of these patients underwent reoperation elsewhere for a baffle leak. Two other patients had reoperation for subpulmonary stenosis and 1, for tricuspid regurgitation. The actuarial survival at 18 years is 92 +/- 2.3%, and the event-free survival is 83 +/- 3.8% (95% confidence limits). Eighty-seven patients are in New York Heart Association Functional Class I, and 3 are in Class II. The results of this study show that the long-term survival and event-free survival have been satisfactory. Late death was significantly higher in patients with complex TGA (p = .027). Postoperative arrhythmia was common, but only 6 patients required permanent pacemakers and the incidence of late complications and reoperation has been low.

Left pulmonary vein stenosis associated with transposition of the great arteries

Two patients with unilateral left pulmonary vein stenosis associated with dextrotransposition of the great arteries and intact ventricular septum are described. Excessive preferential pulmonary artery blood flow to the unaffected side is diagnostic. Awareness and recognition of this rare association is important and the obstruction can be managed with excision of the diaphragm and venoatrioplasty when needed during a Senning or Mustard repair.

Steady flow velocity measurements in a pulmonary artery model with varying degrees of pulmonic stenosis

Velocity and flow visualization studies were conducted in an adult size pulmonary artery model with varying degrees of valvular stenosis, using a two dimensional laser Doppler anemometer system. Velocity measurements in the main, left and right branches of the pulmonary artery revealed that as the degree of pulmonic stenosis increased, the jet type flow created by the valve hit the distal wall of the LPA farther downstream from the junction of the bifurcation. This in turn led to higher levels of turbulent and disturbed flow, and larger secondary flow motion in the LPA compared to the RPA. The high levels of turbulence measured in the main and left pulmonary arteries with the stenotic valves, could lead to the clinically observed phenomenon of post stenotic dilatation in the MPA extending into the LPA.

Hemoptysis following Mustard repair: a late complication

Hemoptysis was the presenting symptom in a 4-year, 11-month-old male who had had a Mustard operation for hemodynamic correction of transposition of the great vessels at the age of five months. Chest roentgenography demonstrated hyperlucency of the left lung and tomography showed compression and narrowing of left main stem bronchus. Angiography documented the absence of antegrade flow in the left pulmonary artery and no pulmonary venous drainage on the left. The left lung was supplied by bronchial collateral arteries which drained by retrograde filling of the left pulmonary artery. It is surmised that pulmonary venous drainage on the left was compromised at surgery and that the dilated main pulmonary artery compressed the left main stem bronchus. This combination promoted bronchial collateral ingrowth. Hemoptysis is a complication of enlargement of bronchial collateral vessels.

Congenital unilateral pulmonary vein stenosis complicating transposition of the great arteries

Four patients with transposition of the great arteries and unilateral pulmonary vein (PV) stenosis, all left-sided, were studied. Two patients had an intact ventricular septum (1 with a patent ductus arteriosus), 1 patient had a ventricular septal defect and 1 had a ventricular septal defect with pulmonary stenosis. Clinical signs, such as recurrent pneumonia, unilateral pulmonary edema and pleural effusion, were present preoperatively in 2 patients. Diagnosis was made at cardiac catheterization by cineangiography in 2 patients and at Mustard operation when the PV orifices were inspected in the other 2. PV dilatation was attempted in 3 patients, 1 before correction (age 6 months), 1 during and after it (ages 1 and 3 years, respectively) and 1 during corrective surgery (age 15 months). In the fourth patient only the intracardiac baffle was enlarged near the left PV orifices. In the first patient, at Mustard operation (age 18 months), only a fibrotic PV without an orifice was found; this patient died after surgery. The mean follow-up in the 3 survivors was 3.2 years (range 2 months to 7.6 years). All have severe residual PV obstruction documented by technetium-99m lung perfusion scans that show decreased flow to the left lung (0 to 16% total counts; normal 45%); 2 have unilateral pulmonary edema and 1 has pulmonary artery pressure at systemic level. It is believed that in patients with transposition of the great arteries, left-sided unilateral PV stenosis is a congenital anomaly that becomes progressive as a result of postnatal preferential flow to the right lung.

Transposition of the great arteries and ventricular septal defect: results with the Senning operation and closure of the ventricular septal defect in infants

From May, 1978, to July, 1982, 46 infants ranging in age from 12 days to 12 months and in weight from 2.1 to 8.4 kg underwent repair of dextrotransposition of the great arteries (D-TGA) and ventricular septal defect (VSD) using a Senning repair and closure of the VSD. Ventricular septal defects were classified as membranous (47.8%), malaligned (28.3%), atrioventricular (AV) canal type (13.0%), subarterial (2.2%), muscular (2.2%), and multiple (6.5%). Hospital mortality was 15.2% and late mortality, 5.1%. Postoperative complications included tricuspid regurgitation (mild in 3 and severe, requiring tricuspid valve replacement, in 3), residual VSD (pulmonary/systemic flow ratio of greater than 2:1) in 3 patients (2, AV canal type and 1, multiple VSDs), pulmonary venous obstruction in 3 patients, and permanent complete heart block in 4 patients (2, AV canal type of VSD also requiring tricuspid valve replacement). Lung biopsy studies showed reversible Heath-Edwards and morphometric changes. No patient was seen with Heath-Edwards III or greater changes. In 10 patients, right ventricular end-diastolic pressures and pulmonary artery pressures at rest were within normal limits one year after operation. As the operative mortality of atrial inversion and arterial switch operations for D-TGA with VSD tends to become comparable, more extensive follow-up data, including cardiac catheterization and coronary arteriography in a large number of patients, will be necessary to establish the superiority of one approach over the other.

Unequal pressures in the central pulmonary arterial branches in patients with pulmonary stenosis. The influence of blood velocity and anatomy

Significantly different pressures in the right (RPA) and left (LPA) pulmonary artery were observed at catheterization in patients with pulmonary valvar stenosis and no branch stenosis. The lower pressures in the RPA showed a "valley" during systole and were similar in contour and amplitude to the main pulmonary arterial (MPA) pressure; the LPA pressure, however, had a normal contour, and the peak systolic and mean pressures were higher than those in the MPA and RPA. Angiocardiograms, phonograms, and a simple analysis of fluid mechanics suggest that this pressure pattern is related to (1) the high-velocity jet in the MPA and (2) the anatomy of the central pulmonary arterial branches (bifurcation), the LPA originating more distally than the RPA. The high-velocity jet bypasses the origin of the RPA and breaks up in the distal MPA near the origin of the LPA. The kinetic energy is then reconverted into pressure, causing the higher LPA pressures. In patients with transposition of the great arteries and subvalvar pulmonary stenosis, the anatomy of the main pulmonary arterial bifurcation is different from normal, the RPA originating more distally than the LPA. The high-velocity jet may bypass the origin of the LPA and break up near the more distal origin of RPA, and the pressures in the RPA can be higher than those in the MPA and LPA.

Anatomic correction of transposition of the great arteries: pre- and postoperative cardiac catheterization, with angiocardiography in five patients

Six of eight patients survived anatomic correction of transposition of the great arteries and repair of associated cardiovascular anomalies at the Hospital for Sick Children, Toronto, Canada. Two of the six survivors also had tricuspid atresia, and continuity between the right atrium and the subaortic outlet chamber in these patients was provided by a valved external conduit, in addition to the arterial switch and coronary artery reimplantation. Five of the six patients have undergone complete postoperative clinical, hemodynamic and angiocardiographic investigation and form the basis of this communication. Our present indications for anatomic repair are discussed.

Lung biopsy specimens in the evaluation of pulmonary vascular disease

Open lung biopsy specimens in 72 patients were submitted for evaluation of pulmonary vascular disease. In nine instances, the specimens were inadequate for this purpose. Essentially, there were three indications for taking a lung biopsy specimen. The first was unexplained pulmonary hypertension with 40 patients in this category; plexogenic pulmonary arteriopathy was diagnosed in 14, and chronic pulmonary thromboembolism in 12. Others included pulmonary venoocclusive disease in two patients; two other patients had pulmonary vascular lesions in their lung biopsy specimens, indicative of chronic hypoxic pulmonary hypertension; and ten patients had severe arterial as well as venous alterations that could have been caused by obstruction to pulmonary venous flow as well as by fibrosis of lung tissue. Since we realized this possible source of error, we have submitted these two alternative possibilities to the clinician. In a heterogeneous group of eight patients, the nature of acquired or congenital heart disease remained doubtful in spite of extensive clinical investigation. In several instances, the biopsy specimen contributed to establishing the diagnosis of the cardiac condition. Finally, in a group of 15 patients with known congenital cardiac disease and pulmonary hypertension, whose state of pulmonary vasculature was considered borderline as far as the possibility of corrective surgery of the cardiac defect was concerned, lung biopsy specimens helped to determine the feasibility of surgery. The results show that in a restricted group of patients with pulmonary vascular disease, a biopsy of the lung has a place in establishing the nature and severity of the vascular alterations.

Radionuclide scintiphotography in defining postoperative pulmonary vasoconstriction. Succesful results after tolazoline administration in a four-month-old infant with congenital heart disease

99mTechnetium macroaggregated albumin has successfully been used to define severe postoperative pulmonary vasoconstriction in a four-month-old boy with D-transposition of the great vessels who had undergone a Blalock-Hanlon surgical atrial septectomy. Radionuclide imaging documented clinically suspected pulmonary vasoconstriction and led to the successful use of tolazoline (Priscoline) to reverse the vasoconstriction with improved pulmonary blood flow patterns.

Lung biopsy in congenital heart disease: a morphometric approach to pulmonary vascular disease

Fifty patients with congenital heart disease, ages 2 days-30 years (median 12 months) at cardiac surgery, underwent lung biopsy to assess pulmonary vascular disease (PVD). Twenty-six had ventricular septal defects (VSD), 17 d-transposition of the great arteries (D-TGA), and seven, defects of the atrioventricular canal (AVC). Quantitative morphologic data was correlated with hemodynamic data. Three new grades of PVD were observed. Abnormal extension of muscle into peripheral arteries (grade A) was found in all patients; all had increased pulmonary blood flow. In addition, 38 of 50 patients had an increase in percentage arterial wall thickness (grade B); this correlated with elevation in pulmonary artery (PA) pressure (r = 0.59). Another 10 of 50 patients had, in addition to A and B, a reduction in the number of small arteries (grade C); nine of 10 were patients with elevated PA resistance greater than 3.5 mu/m2 (P less than 0.005). All three patients with Heath-Edwards changes of grade III or worse also had grade C. Reduction in peripheral arterial number probably precedes obliterative PVD and may identify those patients in whom, despite corrective surgery, PVD will progress.