Comparison of the cardiac output and stroke volume response to upright exercise in children with valvular and subvalvular aortic stenosis.

Cardiac output and stroke volume were evaluated in 17 children (mean age 11.5 +/- 3 years) with discrete, membranous subvalvular (Group I, n = 7) and valvular (Group II, n = 10) aortic stenosis during submaximal and maximal (greater than 75% predicted maximal oxygen consumption) upright cycle ergometry. Patients with valvular aortic stenosis were further subdivided on the basis of their aortic valve gradient at rest determined by cardiac catheterization (Group IIA, gradient less than 40 mm Hg; Group IIB, gradient greater than or equal to 40 mm Hg). These patients were matched with 17 control subjects on the basis of age, sex, height and intensity of exercise during maximal exertion. Cardiac and stroke indexes were determined by the acetylene rebreathing method at each exercise level. Stroke volume index in Group I was significantly greater at rest when compared with that in control subjects (69 +/- 13 versus 53 +/- 11 ml/m2, alpha = 0.01, p less than 0.05) and that in patients in Group II (69 +/- 13 versus 47 +/- 12 ml/m2, alpha = 0.01, p less than 0.05). Patients with subvalvular aortic stenosis were unable to increase their stroke volume index from rest to submaximal exercise and also decreased their stroke volume index at maximal exercise levels. In contrast, patients with mild valvular aortic stenosis (Group IIA) displayed a normal exercise response. Patients with severe valvular aortic stenosis (Group IIB) had a blunted stroke volume response at rest and at each level of exercise, as well as signs of myocardial ischemia (ST segment depression) during maximal exercise.(ABSTRACT TRUNCATED AT 250 WORDS)

Discrepancies in aortic growth explain aortic arch gradients during exercise.

OBJECTIVES: This study was conducted to evaluate the incidence and etiology of hypertension and aortic arch gradients during exercise in patients who have apparent good coarctation repair assessed at rest. BACKGROUND: The reported incidence of recurrent aortic arch obstruction (rest gradient > 20 mm Hg) after previous successful surgical repair varies from 0% to 60% and usually is associated with recurrent stenosis at the site of surgical repair. METHODS: Maximal treadmill exercise with Doppler echocardiographic gradient estimation was performed in 28 patients with a good coarctation repair at rest (normal blood pressure and arch gradient < 20 mm Hg) who had isolated coarctation repair a mean of 7.8 years previously. RESULTS: Eight (29%) developed systolic hypertension for age and a mean Doppler gradient of 45 +/- 13 mm Hg. At cardiac catheterization, the rest peak to peak systolic gradient (6 +/- 6 to 28 +/- 7 mm Hg, p < 0.001), peak systolic instantaneous gradient (16 +/- 11 to 48 +/- 9 mm Hg, p < 0.01) and cardiac index (3.5 +/- 0.7 to 5.9 +/- 1.1 liters/m per m2, p < 0.001) all increased during isoproterenol infusion. Angiographic systolic aortic arch measurements proximal to the innominate artery, left common carotid artery, left subclavian artery and the narrowest dimension at the coarctation repair site demonstrated hypoplasia at the left common carotid artery (11.8 +/- 1.7 vs. 16.7 +/- 2.9 mm/m2, p < 0.01) and left subclavian artery (11.6 +/- 1.7 vs. 15.4 +/- 3.1 mm/m2, p < 0.05) compared with findings in 10 patients with normal aortograms. Transverse aortic arch ratios were also smaller in the eight patients with abnormal findings. Preoperative angiographic ratios were not predictive of late postoperative findings. CONCLUSIONS: Exercise testing detects hypertension and arch gradients in patients with a good coarctation repair as assessed at rest. The hypertension and arch "obstruction" appear to be related to discrepancies in the growth of the transverse aortic arch proximal to the repair site, rather than a "recoarctation" of the aorta.

The Fontan operation in infants less than 2 years of age.

Young age remains a reported risk factor for a successful Fontan operation despite improved survival rates. Since March 1978, the Fontan operation has been performed in 47 patients. To avoid a primary or secondary palliative shunt, an early Fontan procedure (Group 1: mean age 1.5 +/- 0.5 years, range 0.6 to 2) has been performed in 17 children with the outcome similar to that of the remaining 30 older patients (Group 2: mean age 7.5 +/- 5 years, range 2.4 to 23 years). Preoperatively both groups had acceptable hemodynamic status for a successful Fontan result. Operative variables including cardiopulmonary bypass time, aortic cross-clamp time and core temperature were similar between groups and did not affect mortality. The postoperative mortality rate including early surgical (0% vs. 13%, respectively), late (18% vs. 12%) and total (18% vs. 23%) was similar between Groups 1 and 2 (p greater than 0.05). Immediate postoperative arrhythmias were more frequent in Group 1 (71% vs. 25%, p less than 0.01) with no related mortality, while late arrhythmias occurred with equal frequency (29% vs. 39%, p greater than 0.05). Group 1 infants required a longer hospital stay (22 +/- 9 vs. 14 +/- 5 days, p less than 0.01). Thus, young age is not a risk factor for successful outcome of the Fontan operation in patients with acceptable preoperative hemodynamic status. An early Fontan operation may also avoid prolonged palliative procedures and their potential deleterious effects.

Role of balloon atrial septostomy before early arterial switch repair of transposition of the great arteries.

Preoperative balloon atrial septostomy is the standard therapy for babies with uncomplicated cyanotic dextrotransposition of the great arteries despite the effectiveness of prostaglandin E1 infusion in alleviating systemic hypoxemia and the reported success of arterial switch repair during the 1st weeks after birth. The clinical records and echocardiographic findings of 23 infants (mean birth weight +/- SD 3.3 +/- 0.5 kg) with uncomplicated transposition of the great arteries were analyzed. Fifteen infants (Group I) did not undergo septostomy, and 8 (Group II) underwent septostomy. Before prostaglandin infusion, mean arterial oxygen tension (Po2) in Group I (26 mm Hg) did not differ from that in Group II. After prostaglandin infusion, Po2 increased significantly in Group I (43 +/- 8 mm Hg, p less than 0.001) but not in Group II despite a widely patent ductus and predominant left to right ductal shunt in all. After septostomy, Po2 increased significantly (43 +/- 4 mm Hg, p less than 0.03), and did not differ from that in Group I. Echocardiographic features generally demonstrated a nonrestrictive foramen ovale in Group I and a restrictive foramen ovale in Group II. The latter was associated with persistent hypoxemia after prostaglandin. Thus, the diameter of the foramen ovale was the primary factor influencing arterial oxygenation during prostaglandin infusion. Babies underwent the arterial switch operation at a mean age of 70 +/- 65 h with an overall survival rate of 96%; there was only one postoperative death (Group II). Absence of septostomy had no negative influence on any postoperative variable, including duration of ventilatory and inotropic support, time to discharge, or mortality.(ABSTRACT TRUNCATED AT 250 WORDS)

Effectiveness of an umbilical artery "snare assisted" approach for critical pulmonary valve stenosis or atresia in the neonate.

Thirteen neonates with critical pulmonary valve stenosis/atresia underwent successful transcatheter balloon valvuloplasty using an umbilical artery "snare assisted" approach. This technique simplifies the procedure and avoids femoral artery injury by using the umbilical artery, reduces fluoroscopy exposure, and eliminates the need for a gradational approach which reduces costs.

Transvenous "snare-assisted" coil occlusion of patent ductus arteriosus.

Sixty consecutive patients underwent successful transcatheter closure of patent ductus arteriosus without morbidity using a modified transvenous "snare-assisted" approach and a single elongated Gianturco coil. This technique ensures complete occlusion and avoids inadvertent embolization of the coil to undesirable sites, making transcatheter occlusion a viable alternative to surgical ligation.

Initial results and clinical follow-up after balloon angioplasty for native coarctation.

This study describes the initial hemodynamic results and early to late clinical follow-up, including magnetic resonance imaging and exercise testing, following balloon angioplasty for native coarctation of the aorta. We advocate this approach as an alternative to surgical intervention in select patients based on age, aortic arch anatomy, or in those patients who have coexisting cardiac defects that are amenable to transcatheter intervention.

Transvenous approach to coronary angiography in infants with tetralogy of Fallot.

A new technique is offered for selective imaging of the coronary arterial system from a transvenous approach in patients with tetralogy of Fallot as an alternative to other traditional approaches. This technique should identify important coronary anomalies while avoiding femoral arterial cannulation and compromise.

Efficacy of intraoperative transesophageal echocardiography in children with congenital heart disease.

The feasibility and potential adverse effects of using intraoperative transesophageal echocardiography (TEE) in 19 children ages 7.5 to 16 years undergoing surgical repair of a variety of congenital heart defects were evaluated. The ability of TEE to assess the adequacy of surgical repair as well as left ventricular function and wall motion abnormalities in this setting was also examined. Intraoperative transesophageal 2-dimensional and Doppler evaluation, and, in selected patients, echo-contrast and color flow imaging, were performed with either a 3.5- or 5.0-MHz phased array probe mounted within the tip of a flexible gastroscope. Probe insertion was successful in 18 of 19 patients. Fiberoptic endoscopy (9 patients) and autopsy (1 patient--cardiac donor) performed within 24 hours of surgery demonstrated no significant esophageal abnormalities. Intraoperative wall motion abnormalities were identified in 8 patients but did not persist after the operation. An adequate surgical repair was demonstrated by contrast and color flow imaging in most patients. Microcavitation was detected in 6 patients for greater than 5 minutes after a standard debubbling procedure. No patient displayed any adverse neurologic effects. It is concluded that, with the currently available probes, intraoperative TEE can be performed safely and reliably in children as young as 7.5 years of age. The procedure provides valuable information regarding wall motion abnormalities, cardiac function and the adequacy of surgical repair.

Aortic "recoarctation" at rest versus at exercise in children as evaluated by stress Doppler echocardiography after a "good" operative result.

The mechanism for exercise systolic hypertension after a "good" operative repair of coarctation of the aorta remains speculative. Twenty-four children (mean age +/- SD 10.3 +/- 3.8 years) were studied with continuous-wave Doppler echocardiography while they performed continuous, graded, maximal treadmill exercise. Patients were free of "recoarctation" based on conventional resting echocardiography. Measurements of ascending and descending aortic peak instantaneous systolic velocity were obtained at rest, throughout exercise and during recovery. Results were compared with 24 age- and gender-matched control subjects. Fifteen patients were normotensive (group 1) (peak systolic blood pressure, 147 +/- 21 mm Hg) and 9 developed systolic hypertension during exercise (group 2) (196 +/- 32 mm Hg) (p < 0.05) (control subjects, 143 +/- 21 mm Hg). Descending aortic peak systolic velocity at rest ranged from 1.50 +/- 0.27 m/s in the control group to 2.57 +/- 0.57 m/s (group 1) and 2.93 +/- 0.43 m/s (group 2) (p < 0.05, group 2 vs control). Differences were amplified at peak exercise with systolic velocity increasing to 4.26 +/- 0.61 m/s in group 2 but only to 3.61 +/- 0.70 m/s in group 1 and 2.26 +/- 0.38 m/s in control subjects (p < 0.05, group 2 vs group 1 and control). Seven patients developed a descending aortic diastolic velocity during exercise. Stepwise linear regression analysis identified 2 variables to be significant determinants of peak exercise systolic blood pressure in the "total" patient group: (1) age at exercise testing, and (2) descending aortic peak systolic velocity at peak exercise (r2 = 0.88, p < 0.001) (group 2, alone - r2 = 0.98, p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

The Norwood operation and subsequent Fontan operation in infants with complex congenital heart disease.

From April 1987 to September 1993, 60 infants underwent a Norwood operation for complex congenital heart disease including hypoplastic left heart syndrome (n = 41), ventricular septal defect and subaortic stenosis with aortic arch interruption/severe coarctation (n = 7), complex single right ventricle with subaortic stenosis (n = 8), critical aortic stenosis with endocardial fibroelastosis (n = 2), and malaligned primum atrial septal defect with coarctation (n = 2). Age at operation ranged from 1 day to 3.9 months (mean 9 days, median 3.5 days). The operative mortality (< 30 days) was 33% (20 patients). Late mortality was 17% (10 patients). Nine of the 20 (45%) operative deaths occurred during the first 2 days after the operation as a result of sudden hemodynamic instability. All four infants with premature closure of the foramen ovale had pulmonary lymphangiectasia and died of pulmonary failure. Seven operative deaths have occurred in 36 patients since 1990 (19%); in the past 2 years, no operative deaths have occurred in 22 patients. Overall, there are 30 long-term survivors (50%). Twenty-one of these 30 infants have undergone a two-stage repair with a modified Fontan operation at 7.3 to 27.6 months of age (mean 18.1 months) with no mortality. Six patients have entered a three-stage repair strategy by undergoing a hemi-Fontan procedure at 6.8 to 23.0 months (mean 8.8 months) with no mortality, and two of these patients have now had their modified Fontan operation at 23.0 to 46.7 months of age with no mortality (four are still awaiting surgery). Two patients have undergone a two-ventricle repair with a Rastelli procedure, with no mortality at 7.4 and 14.1 months of age. Early in our experience, infants undergoing the Norwood operation had a high early mortality most often related to sudden hemodynamic instability. After we instituted a protocol that adds carbon dioxide to the inspired gas during postoperative mechanical ventilation, the postoperative course became more stable and there have been no operative deaths. In summary, the operative mortality for the Norwood operation continues to improve. A subsequent Fontan operation can be performed with excellent clinical results.

Results of surgical repair of congenital supravalvular aortic stenosis.

Our experience with congenital supravalvular aortic stenosis dates from 1977 to 1991. Thirteen patients, aged 2 days to 38 years (mean 7.6 years, median 3.8 years), had surgical repair of the lesion. The preoperative peak-to-peak systolic gradients ranged from 25 to 110 mm Hg (mean 64 mm Hg). Four patients had trace to mild aortic insufficiency. Surgical repair was accomplished by several techniques that have evolved over time. There was one death in a 2-day-old neonate who also had severe hypertrophic cardiomyopathy. The 12 survivors had postoperative gradients of 0 to 30 mm Hg (mean 10 mm Hg) in the supravalvular region. The mean reduction in gradient was 48 mm Hg. A new technique employing all autologous aortic tissue is described.

Surgical management of coronary insufficiency in a child with Kawasaki's disease: use of bilateral internal mammary arteries.

Coronary insufficiency is an important sequela of Kawasaki's disease. Successful myocardial revascularization with saphenous vein grafts and, more recently, with internal mammary artery grafts has been performed. We report a case of Kawasaki's disease with chronic coronary insufficiency in which complete myocardial revascularization was accomplished using bilateral internal mammary arteries, and we present a review of the literature.

Application of intraoperative transesophageal echocardiography in infants and small children.

Intraoperative echocardiography is gaining increasing acceptance in the assessment of the surgical repair of congenital heart defects. Because of its ideal imaging location, intraoperative transesophageal echocardiography (TEE) has been especially helpful in evaluating pulmonary venous return and the integrity of the left atrioventricular valve following mitral valvuloplasty, complete atrioventricular valve repair and correction of complex congenital heart disease. It has not been routinely used in infants and small children because of a prohibitively large probe size. We report the successful use of a recently developed "pediatric" TEE probe capable of Doppler and color flow imaging in two patients less than 7 years of age. No complications were encountered. Recommendations regarding optimal probe imaging positions in infants are provided.

Spontaneous-onset atrial fibrillation in a toddler with review of mechanisms and etiologies.

Atrial fibrillation is a relatively rare form of arrhythmia in the pediatric population. When it is seen in an infant or child, it is often associated with a structural heart abnormality, particularly after surgical repair or palliation of congenital heart disease. Other episodes may be associated with metabolic derangements. This report discusses the unique case of a toddler with new-onset atrial fibrillation that was devoid of a readily identifiable etiology. It also reviews the literature and the implications of such a case for the primary care practitioner.

Pulmonary artery growth fails to match the increase in body surface area after the Fontan operation.

OBJECTIVE: To evaluate the growth of the pulmonary arteries after a Fontan procedure. DESIGN: Retrospective review. SETTING: Two paediatric cardiology tertiary care centres. PATIENTS: 61 children who underwent a modified Fontan operation and had angiography suitable for assessment of pulmonary artery size before the Fontan procedure and during long term follow up. An atriopulmonary connection (APC) was present in 23 patients (37.7%) and a total cavopulmonary connection (TCPC) was present in 38 (62.3%). Postoperative angiograms were performed 0.5-121 months (median 19 months) after the Fontan operation. MAIN OUTCOME MEASURE: Growth of each pulmonary artery measured just before the first branching point. The diameter was expressed as a z score with established nomograms used to standardise for body surface area. RESULTS: The mean change in the preoperative to postoperative z scores of the right pulmonary artery was -1.06 (p = 0.004). The mean change in the preoperative to postoperative z scores of the left pulmonary artery was -0.88 (p = 0.003). Changes in the preoperative to postoperative z scores were more pronounced in the patients undergoing APC than TCPC, especially for the right pulmonary artery. CONCLUSION: After the Fontan operation, growth of the pulmonary arteries often fails to match the increase in body surface area.

Coarctation of the aorta in the adolescent and adult: echocardiographic evaluation prior to and following surgical repair.

The combination of two-dimensional and continuous-wave (CW) Doppler echocardiographic imaging forms the cornerstone of diagnostic imaging in pre- or postoperative coarctation of the aorta. Because of the frequent association of other congenital heart defects, e.g., bicuspid aortic valve, a segmental imaging approach with multiple image planes should be used. CW Doppler examination from the suprasternal notch should be utilized to assess the degree of obstruction at the coarctation site in all patients. This enhances diagnostic sensitivity. CW Doppler examination can also be applied throughout exercise. Such application allows detection of relative degrees of aortic obstruction following surgical repair of coarctation that may only manifest at elevated levels of cardiac output, e.g., exercise. It aids in the identification of individuals with exercise related systolic hypertension following "successful" coarctectomy and provides a rationale for treatment with beta blockade. The methodology for applying this relatively new technique is discussed.

Developmental differences in the response of cytosolic free calcium to potassium depolarization and cardioplegia in cardiac myocytes.

Several biochemical and functional characteristics of immature myocardium suggest a diminished capacity to regulate intracellular Ca2+ during stress. In particular, cellular calcium overload has been postulated as an important pathogenetic mechanism accounting for suboptimal functional recovery following cardioplegia in immature myocardium. Using intracellular Fura-2 fluorescence as Ca2+ indicator, we measured cytosolic free calcium ([Cai]) in single myocytes and cell suspensions derived from both juvenile (4 weeks post-partum) and mature (6-12 months post-partum) New Zealand white rabbits. Resting [Cai] in juvenile heart cells (26 +/- 3 nM) were approximately 50% of that found in adult myocytes (55 +/- 5 nM). In addition, on exposure to increasing concentrations of extracellular potassium ([Kex]), adult but not juvenile myocytes exhibited increases in [Cai]. These two observations underscore developmental differences in intracellular Ca2+ homeostasis. Of particular clinical relevance is the [Cai] response to cardioplegia containing 16 mM [Kex]: neither group demonstrated the expected [Cai] increase in response to potassium depolarization. The lack of [Cai] response to cardioplegia was most likely due to the high levels of Mg2+ (32 mM) contained in cardioplegic solutions. We conclude that cellular calcium overload does not occur following exposure to cardioplegia alone. Accordingly, these findings do not account for recognized developmental differences in functional recovery from "myocardial protection".