Eberhard Mühler

Twenty years experience with pediatric pacing: epicardial and transvenous stimulation

OBJECTIVE Permanent cardiac pacing in children and adolescents is rare and often occurs by means of epicardial pacing. Based on two decades of experience, operative and postoperative data of patients with epicardial and transvenous pacing were analyzed retrospectively. METHODS Between October 1979 and December 1998, 71 patients (mean age, 5.3+/-4.2, range, 1 day-16.2 years; mean body weight, 18+/-12; range, 8-56 kg) underwent permanent pacemaker implantation. Indications were sinus node dysfunction and atrio-ventricular block following surgery for congenital heart disease (69%), or congenital atrioventricular block (31%). Pacing was purely atrial (1.4%), purely ventricular (73%), ventricular with atrial synchronization (5. 6%), or atrioventricular synchronized (20%). Epicardial pacing was established in 49 (69%), transvenous in 22 (31%) patients. Follow-up was 3.4+/-3.8 years (epicardial) and 3.0+/-4.0 years (transvenous). RESULTS Epicardial leads were implanted in younger patients (mean age: 4.5 vs. 7.0 years, P<0.05) and preferably after surgery induced atrioventricular block (78 vs. 46%, P<0.05). The youngest patient with transvenous pacing was 1.3 years old (weight, 8.5 kg). At implantation epicardial ventricular stimulation threshold at 1.0 ms was 1.07+/-0.46 vs. 0.53+/-0.31 V (transvenous) (P<0.05). The age-adjusted rate of lead-related reoperations was significantly higher in patients with epicardial leads (P<0.05), mainly due to increasing chronic stimulation thresholds resulting in early battery depletion. In three patients who received steroid-eluting epicardial leads initial low thresholds persisted after five month to one years. In two patients with recurrent epicardial threshold increase, steroid-eluting epicardial leads led to good acute and chronic thresholds after nine to 15 month. Two post-operative death (2.8%) were probably due to a dysfunction of the (epicardial) pacing system. CONCLUSIONS Transvenous pacing in the pediatric population is associated with a lower acute stimulation threshold and a lower rate of lead-related complications. If epicardial pacing is necessary (e. g. small body weight, special intracardiac anatomy (e.g. Fontan), impossible access to superior caval vein), steroid-eluting leads may be considered.

Cardiac involvement in tuberous sclerosis.

OBJECTIVE--To assess the incidence, importance, and history of cardiac involvement in infants and children with tuberous sclerosis. DESIGN--Prospective study; clinical examination, sector and Doppler echocardiography, standard and ambulatory electrocardiography. SETTING--A tertiary referral centre. PATIENTS--21 patients with tuberous sclerosis aged 1 day to 16 years (mean 6.3 years); follow up investigations were available in 14 cases (10 retrospective, 4 prospective; mean follow up 4.3 years). RESULTS--Multiple cardiac rhabdomyomas in the right ventricle (11) and left ventricle (14) as well as in the right atrium (1) were present in 14/21 patients. Two of them had obstruction of the left ventricular inflow and outflow tract related to a tumour. In the remaining 7 patients, echocardiography was normal in 4 and equivocal in 3 cases. The standard electrocardiogram (n = 20) showed ventricular hypertrophy (2), ventricular pre-excitation (1), arrhythmias (2), and repolarisation disturbances (4) in 7/13 patients with rhabdomyomas but was normal in all patients with a normal or equivocal echocardiogram. The ambulatory electrocardiogram (n = 19) showed frequent premature atrial (2) and polymorphous ventricular (2) contractions. The polymorphous ventricular contractions coexisted with rhabdomyomas. No arrhythmias that needed medical treatment were found. Follow up investigations showed return to a normal standard electrocardiogram in 3 patients. Definite regression or complete disappearance of the tumour occurred in 6 infants. CONCLUSIONS--Cardiac rhabdomyomas, although often present in these patients with tuberous sclerosis, caused neither major arrhythmias nor haemodynamic obstruction except in the neonatal period. The indication for operation is limited to cases with life threatening obstruction or arrhythmias refractory to medical treatment.

Evaluation of aortic coarctation after surgical repair: role of magnetic resonance imaging and Doppler ultrasound.

OBJECTIVE--To compare the usefulness of magnetic resonance imaging (MRI) and Doppler ultrasound with that of cross sectional echocardiography and oscillometric blood pressure measurement for the evaluation of aortic coarctation after surgical repair. DESIGN--Prospective study. Aortic diameters measured by cross sectional echocardiography, MRI, and angiography (selected cases) and functional data determined by physical examination, oscillometric blood pressure measurement, and continuous wave Doppler. SETTING--Tertiary referral centre. PATIENTS--40 patients aged 2-28 years (mean 10.6 years) who had had surgical correction of aortic coarctation (mean follow up 5.7 years). RESULTS--In all patients MRI gave diameter measurements of the aortic arch and the thoracic aorta whereas in half of them cross sectional echocardiographic measurement of the isthmic region failed. The correlation coefficient for aortic diameters measured by MRI and angiography was 0.97 and that between MRI and echocardiography was 0.89. Peak velocities in the descending aorta correlated better with residual narrowing of the aortic isthmus or distal aortic arch or both than systolic blood pressure gradients between the upper and lower limbs. A peak velocity of < 2 m/s in the descending aorta during systole excluded important restenosis. Prolongation of anterograde blood flow during diastole always indicated a morphological abnormality--either important restenosis or aneurysmal dilatation. CONCLUSIONS--MRI was better than cross sectional echocardiography for imaging the aortic arch after coarctation repair and measuring its diameter. Peak velocity in the descending aorta correlated better with residual stenosis than did the systolic blood pressure gradient between the upper and lower limbs and this index could be used to indicate a need for MRI.

Surgical correction of coarctation in early infancy: Does surgical technique influence the result?

Between 1979 and 1988, a total of 53 infants less than 1 year of age underwent repair of coarctation. Thirty-seven patients (70%) were younger than 3 months. Median age was 0.9 month. Four different surgical techniques were used: resection with end-to-end anastomosis, patch enlargement, subclavian flap aortoplasty, and subclavian displacement aortoplasty (Meier-Mendonca technique). Hospital mortality was 7.5% and was limited to patients with additional complex intracardiac defects. Neither age nor surgical technique had an influence on the operative risk. Follow-up averaged 15 to 43 months for the four different groups. Restenosis developed in 9 (19%) of 47 patients regularly followed up, 5 (11%) of whom have had reoperation. Age at operation was not a predictor for restenosis, which occurred in 17.4% of patients less than 1 month and 20.8% of those greater than 1 month of age at operation. Patch enlargement and the subclavian displacement technique demonstrated the highest restenosis rates (42% and 43%, respectively). However, patients who underwent patch enlargement had less favorable pathological conditions. It is concluded that results of coarctation repair in early infancy do not depend as much on the operative method itself as on the specific pathological aspect, which largely determines the method of treatment. Some reservation must be made in regard to the subclavian displacement technique.

Detection of abnormal aortic elastic properties in asymptomatic patients with Marfan syndrome by combined transoesophageal echocardiography and acoustic quantification.

OBJECTIVE: To evaluate the potential value of transoesophageal echocardiography combined with automated border detection and acoustic quantification for the assessment of elastic properties of the thoracic aorta in patients with Marfan syndrome. SUBJECTS: 16 patients with Marfan syndrome and 12 age matched normal controls. METHODS: Transoesophageal echocardiography was performed in all subjects. Minimum and maximum diameters of the descending thoracic aorta were obtained from M mode images and acoustic quantification was used for the on-line evaluation of cross sectional aortic area and peak positive area changes over time. Compliance, distensibility, and stiffness index were calculated using M mode data and non-invasively measured blood pressure and were compared with the indices derived from acoustic quantification. RESULTS: Aortic dimensions normalised for body surface area were not statistically different between patients and normal controls, but there were significant differences for all elasticity indices except compliance. Marfan patients had a lower distensibility [4.2 (SD 1.8) v 5.8 (2.1) cm2/dyn, P < 0.05] and a higher stiffness index [9.7 (3.0) v 7.1 (1.8), P < 0.05]. The dynamic indices derived from the acoustic quantification were significantly smaller in Marfan patients [peak positive area change: 5.1 (1.0) v 7.7 (1.7) cm2/s; P < 0.001; and normalised peak positive area change: 2.5 (1.2) v 4.0 (0.8) cm2/s respectively, P < 0.001] and were suitable to discriminate between normal and abnormal elastic properties. CONCLUSIONS: In Marfan syndrome elastic properties of the descending aorta are significantly different from normal controls, even in the absence of vessel dilatation. In addition to established static indices, indices derived from acoustic quantification reflect dynamic changes of the cross sectional area for the evaluation of regional vessel mechanics. The on-line assessment of peak positive area change allows differentiation from normal individuals and may be more accurate than standard M mode measurements.

Cardiac hypertrophy secondary to ACTH treatment in children.

The usefulness of ACTH in the treatment of childhood epilepsy is assessed by improvement in the EEG and in the clinical condition. However, pronounced side effects, even serious ones, must be encountered. The most common complications are Cushing syndrome, infections, and arterial hypertension. We report on seven patients with infantile myoclonic seizures, who exhibited myocardial hypertrophy with increased left ventricular function during ACTH treatment. These changes were detected and followed by serial echocardiographic investigations. Within a period of 5 months after the termination of ACTH therapy the abnormal echocardiographic findings disappeared. We believe that the cardiac hypertrophy is ACTH-induced. Based on the various biological effects of ACTH different explanations are proposed: oedema or deposition of glycogen in the myocardial tissue, hyperinsulinism, arterial hypertension and increased inotropic stimulus. Because of our observations, we suggest careful monitoring of children treated with ACTH by performing serial echocardiographic investigations.

Anatomically positioned aorta ascending-descending bypass grafting via left posterolateral thoracotomy for reoperation of aortic coarctation.

OBJECTIVE Operation for aortic recoarctation and/or residual hypoplastic arch represents a surgical challenge because of surrounding scar tissue in the coarctation area, hazard of spinal cord ischemia due to aortic cross-clamping, laceration of the recurrent nerve, and the choice of the best approach. We demonstrate the first results of an anatomically guided technique via the prior left thoracotomy approach without establishment of cardiopulmonary bypass. METHODS Since 1989, five patients underwent anatomically positioned ascending-descending bypass grafting for treatment of recoarctation. Indication was a non-dilatable hypoplastic aortic arch segment; in two cases an additional isthmic restenosis was present. Inclusion criteria for our technique was an aorta ascending diameter large enough to allow partial clamping. Primary repair of aortic coarctation was end-to-end anastomosis in four patients and patch angioplasty in one. Mean age at primary repair was 5.5 years and at reoperation 16.1 years. Systolic pressure gradients at rest ranged from 35 to 70 mmHg; upper extremity hypertension was present in all patients. Operative technique consisted of performing a dacron or PTFE aorta ascending-descending bypass graft parallel to the aortic arch, size 18 or 20 mm in diameter, via the prior left thoracotomy. RESULTS There were no intraoperative complications and all patients survived. Postoperative complications were left lung atelectasis with necessity of reintubation, pericardial effusion, and transient left diaphragm elevation, each in one patient. After 7-90 months all patients are free of symptoms, have normal blood pressure (with two patients being under anti-hypertensive medication), and have no echocardiographically measurable pressure gradients. CONCLUSIONS Anatomically positioned aorta ascending-descending bypass grafting via the prior left posterolateral thoracotomy without cardiopulmonary bypass is a safe and efficient method for operation of complex recoarctation in patients with an acceptable size of the aorta ascendens.

Comparison of the 6-minute walk test with established parameters for assessment of cardiopulmonary capacity in adults with complex congenital cardiac disease

BACKGROUND Objective assessment of the cardiopulmonary capacity in patients with complex congenital cardiac disease often remains difficult in clinical practice. The cardiopulmonary exercise test and determination of the levels of brain natriuretic peptide in the plasma are established tests, but expensive. The 6-minute walk test is also validated, but has not often been used in patients with heart failure due to congenital heart disease, nor compared with other tests. We sought to compare its value with the results of cardiopulmonary exercise testing and measuring the levels of brain natriuretic peptide in the plasma. METHODS We carried out a standardized 6-minute walk test in 31 patients with complex congenital cardiac disease on the same day that they underwent cardiopulmonary exercise testing and determination of levels of brain natriuretic peptide in the plasma. Of the patients, 7 had functionally univentricular hearts, 9 had transposition, 9 had tetralogy of Fallot, 3 had common arterial trunk, and 3 had pulmonary atresia with intact interventricular septum. Uptakes of oxygen at peak exercise, and at the anaerobic threshold, were determined using cardiopulmonary exercise testing, and classified as suggested by Weber. The 6-minute walk test was performed according to a standard protocol. RESULTS There was a significant correlation between brain natriuretic peptide, oxygen uptakes at peak exercise and 6-minute walk. The correlation between the 6-minute walk test and oxygen uptakes at the anaerobic threshold, however, was not significant. CONCLUSIONS The 6-minute walk test can be performed easily, is inexpensive, widely available, and correlates well with measurements of brain natriuretic peptide and cardiopulmonary exercise testing, even in patients with corrected or palliated congenital cardiac malformations. A cut-off value of 450 metres in the 6-minute walk test allows a semi-quantitative classification in analogy to the classification suggested by Weber for cardiopulmonary exercise testing, and to a level of brain natriuretic peptide in the plasma of less or more than 100 picograms per millilitre.

Low to Medium WU-Virus Titers in Young Children with Lower Respiratory Tract Infections

The WU-virus (WUV), a novel polyomavirus, has recently been recovered from respiratory tract samples. Within a study collective of children with severe lower respiratory tract disease, 3% of the patients tested WUV positive. Viral loads ranged from 5 × 102 copies/ml to 1 × 104 copies/ml. The WUV genome-positive patients did not display specific clinical or radiological characteristics to be distinguished from other respiratory tract infections.

Successful Thrombolysis of Inferior Vena Cava Thrombosis in a Preterm Neonate

I nferior vena cava thrombosis accounts for an important percentage of neonatal venous thrombosesl-3 and is associated with various risk factors, such as use of central venous catheters, hereditary thrombophilia, low cardiac output, cardiac catheterization, asphyxia, infection, and hemolysis, elevated liver enzymes, and low platelet count (HELLP) syndrome. Although there may be a high risk for persisting venous occlusion and obstruction,3 guidelines for thrombolysis of neonatal inferior vena