Markus K. Heinemann

Inhibition of the fetal stress response improves cardiac output and gas exchange after fetal cardiac bypass

Cardiac bypass in late-gestation fetal lambs causes severe placental vasoconstriction, which leads to fetal death from hypoxemia and respiratory acidosis. This response can be blocked by the administration of indomethacin; however, a fatal metabolic acidosis then gradually develops in the fetus. Because the fetus is known to mount an intensive catecholamine response to stress, and because the fetal myocardium is particularly sensitive to increased afterload, we hypothesized that elevated afterload as a result of fetal stress contributes to diminished cardiac output after bypass. Twenty fetal lambs at 80% gestation underwent 30 minutes of normothermic cardiac bypass at flow rates of 200 to 500 ml/kg per minute. All ewes received general anesthesia with ketamine. In 10 fetuses general anesthesia was specifically designed not to inhibit the release of stress-related catechols (ketamine); the remaining 10 fetuses received a high (cisterna magna) total spinal anesthetic with tetracaine, to block the fetal stress response. In each anesthetic group, 5 of the 10 lambs received indomethacin. During operation, normal hemodynamics were preserved in the spinal anesthetic group. Cardiac output, placental blood flow, and arterial carbon dioxide tension were all improved relative to results in the ketamine group. When spinal anesthesia and indomethacin are both given, hemodynamics also approach normal after bypass, and gas exchange is further improved. These data suggest that the inhibition of the stress response by spinal anesthesia improves the hemodynamic status of the fetus during operation and, in combination with indomethacin, allows maintenance of near-normal placental function after fetal cardiac bypass. Similar responses may also be possible in human fetuses with use of a high-dose narcotic technique.

Total anomalous pulmonary venous drainage in newborns with visceral heterotaxy

Children with visceral heterotaxy often present with total anomalous pulmonary venous drainage (TAPVD) associated with univentricular congenital heart disease. We reviewed our experience with the primary surgical management of this lesion under these circumstances. Over a recent 10-year span, 38 patients within the first 3 days of life were admitted to our institution and underwent primary palliation. Twenty-one of them had TAPVD, 18 to a systemic vein. Twelve (67%) of these 18 were seen with obstruction of the anomalous connection and underwent emergency operation. In 7 patients, repair of TAPVD was combined with a systemic-pulmonary artery shunt because of additional obstruction of the pulmonary blood supply, with two deaths. One patient had primary shunting and then repair of TAPVD. Four patients underwent repair of TAPVD alone. Two of them then showed signs of insufficient pulmonary blood flow, received a shunt in a second procedure, and subsequently died. Early mortality in the group with obstructed TAPVD was thus 4 (33%) of 12 patients. Statistical analysis of all 38 patients (univariate analysis, chi 2 testing) showed that neither the presence of TAPVD (p = 0.7) nor TAPVD repair alone (p = 0.8) or with shunting (p = 0.8) was a definite risk factor for early death. The performance of a shunt during the first operation, however, was associated with lower early mortality (p = 0.03). Total anomalous pulmonary venous drainage is a common finding in newborns with visceral heterotaxy. Its presence and its subsequent early repair (requiring cardiopulmonary bypass) do not increase the mortality risk. The need of a concomitant shunt in obstructed TAPVD can initially be underestimated.

Fibrin sealant, aprotinin, and immune response in children undergoing operations for congenital heart disease

OBJECTIVEnMost commercially available fibrin sealants contain aprotinin in doses of 1500 kallikrein inactivator units per milliliter. They are used in many operative disciplines. An elevated risk of hypersensitivity reactions exists at reexposure to aprotinin. Our aim was to examine the immunogenic potency of aprotinin as a fibrin sealant content.nnnMETHODSnWe investigated 49 children with operatively treated congenital heart disease. All patients received aprotinin only topically as contained in fibrin sealant. Serum samples were drawn preoperatively, 1 week, 2 weeks, 6 weeks, and approximately 1 year after operation. They were analyzed for aprotinin-specific immunoglobulin G antibodies with a standard enzyme-linked immunosorbent assay and a fluorescence enzyme immunoassay for aprotinin-specific immunoglobulin E antibodies.nnnRESULTSnAt 1 week, 2 weeks, 6 weeks, and 1 year, we found prevalences of 8% (2 of 26), 8% (2 of 24), 6% (3 of 49), and 0% for aprotinin-specific Immunoglobulin E, and for aprotinin-specific immunoglobulin G 8% (2 of 26), 17% (4 of 24), 39% (19 of 49), and 12% (5 of 41). The doses of aprotinin given did not differ significantly in antibody-negative and antibody-positive patients; no significant factors could predict the immune response.nnnCONCLUSIONSnOur findings show the existence of a subgroup of patients who had aprotinin-specific antibodies develop after topical aprotinin application. Any use of aprotinin must be carefully documented. If aprotinin use is planned in patients who previously underwent a surgical procedure, preexposure to aprotinin in any form must be sought to avoid unexpected anaphylactic reactions. The necessity itself and alternatives for aprotinin as a stabilizing agent in fibrin sealants merit consideration.

Fate of small homograft conduits after early repair of truncus arteriosus

Neonatal repair of truncus arteriosus is being performed in a number of centers, often with the use of small homograft conduits. The fate of the homograft and the risk of replacement were the subjects of this study. Between January 1987 and October 1991, 43 infants aged less than 3 months (range, 3 to 90 days) underwent primary repair of truncus arteriosus including implantation of a valved homograft conduit (diameter, 7 to 12 mm). Twenty-nine had follow-up of more than 6 months (range, 6 to 65 months; mean, 21.9 months). After a mean period of 31 months (range, 8 to 65 months), 7 patients showed obstruction with right ventricular pressures at least 75% systemic and underwent either a conduit change (n = 5) or a patch augmentation (n = 2). Mean cardiopulmonary bypass time at reoperation was 99 minutes; mortality was zero. Five other children are known to have a right ventricular pressure of 50% to 60% systemic, 2 having undergone balloon dilation. Statistical comparison of the patients with conduit reoperation or high right ventricular pressure (n = 12) with the rest of the population (n = 17) revealed an elevated pulmonary artery to right ventricular pullback gradient on postoperative day 1 after the repair (7.7 versus 1.3 mm Hg; p = 0.001) and choice of an aortic over a pulmonary homograft (100% versus 64.7%; p = 0.065) as significant risk factors. Age and weight at repair, postoperative pulmonary artery pressure, length of follow-up, and size of the homograft showed no significant differences between the two groups.(ABSTRACT TRUNCATED AT 250 WORDS)

DDD pacemaker implantation after Fontan-type operations.

HEINEMANN, M.K., et al.: DDD Pacemaker Implantation After Fontan‐Type Operations. Bradyarrhythmias developing after Fontan‐type operations impair the function of the univentricular heart causing fatigue, headaches, ascites, and protein‐losing enteropathy (PLE). Transvenous inaccessibility, requiring epicardial implantation, accounts for the reluctance to implant a pacemaker (PM). Between 1997 and 2000, 24 patients (mean age 9.5 years, range 6 months to 19 years) with Fontan‐type operations received DDD pacing systems with atrial steroid‐eluting stitch‐on electrodes (mean capture threshold 1.9 V/0.5 ms, range 0.4–3.5 V) and ventricular screw‐in electrodes (mean capture threshold 1.7 V/0.5 ms, range 0.1–3 V). The systems were implanted at the time of conversion from atrio‐ to cavopulmonary connections in 5 patients, at the time of a total cavopulmonary Fontan operation in 6, and 1–50 months thereafter (mean = 18) in 13 patients. A right ventricular anatomy was present in 13 (54%) of 24 of PM recipients, versus 35% of the overall population. After a mean follow‐up of 3.5 years, the PM were functioning in DDD mode in 23 of the 24 patients. Length of hospital stay in the ten patients who underwent repeat sternotomy was 5 days, without procedure related complications. In three children a repeat sternotomy was avoided by implanting the atrial electrodes during the Fontan operation. All patients improved clinically, including resolution of PLE in four patients. Bradyarrhythmias may lead to significant morbidity after Fontan‐type operations. Electrophysiological evaluation is advised at follow‐up. The indication for implantation of a DDD pacemaker system should be liberal. Placing atrial electrodes during the Fontan operation, especially in the presence of a right ventricular anatomy, avoids repeat sternotomy. (PACE 2003; 26[Pt. II]:492–495)

Long-term survivors of fetal cardiac bypass in lambs

The initial experience with cardiac bypass in fetal lambs resulted in early fetal death from placental insufficiency. Subsequent work in our laboratory indicated that vasoactive cyclooxygenase products were released as mediators of this response. The placental dysfunction could be blocked by the administration of indomethacin, allowing longer fetal survival. This unmasked a more subacute (but fatal) problem: fetal surgical stress resulted in diminished fetal cardiac output and progressive metabolic acidosis and contributed to the placental vasoconstriction. In acute studies, when indomethacin was given and the stress response was inhibited by the use of total spinal anesthesia, the fetus maintained normal blood gas levels, cardiac output, placental blood flow, and acid-base status for several hours after bypass. We hypothesized that beyond this point, no further fetal or placental compromise would occur and that this management technique would thus allow long-term fetal survival. With the use of total spinal anesthesia and sterile technique for long-term study, 12 fetal lambs at 120 days (80%) gestation underwent exposure, line placement, and cannulation for fetal cardiac bypass. Indomethacin was given intravenously on obtaining venous access. After 20 minutes of normothermic cardiac bypass at flow rates of 250 to 300 ml/kg/min, the fetus was weaned from bypass, the cannulas and lines were removed, the uterus and abdomen were closed, and the ewe and fetus were allowed to recover. There was one maternal death (pneumonia) and one early abortion (of twins); the remaining 10 ewes progressed to term. At term, five healthy lambs that had undergone fetal cardiac bypass were delivered (including one twin), four ewes delivered a mummified study fetus and one or two healthy siblings, and one delivered a dead term fetus. With the use of techniques that inhibit fetal stress and block placental vasoconstriction, cardiac bypass can be performed in single-gestation fetal lambs with a high degree of recovery and survival (80% in this study). The cause of the elevated abortion rate associated with twin gestation is unclear.

Preoperative management of neonatal tetralogy of Fallot with absent pulmonary valve syndrome.

In tetralogy of Fallot with absent pulmonary valve syndrome, aneurysmal enlargement of the central pulmonary arteries can be associated with severe bronchial stenosis and respiratory distress in the neonatal period. The ventilatory status of these patients must be stabilized before diagnostic and therapeutic interventions can be performed. This report describes the experience with prone positioning and emergency sternotomy in the preoperative care of a neonate.

Successful weaning of a transplanted heart from biventricular assist device

Exceptionally few cases worldwide have survived weaning from a biventricular assist device following heart transplantation in contrast to those who underwent early retransplantation. We present a successful outcome after biventricular assist device implantation following initial biventricular failure after heart transplantation. Weaning could be performed after 1 week, although pulmonary vascular resistance remained markedly elevated.