Michael Huebler

Biventricular Circulatory Support With Two Miniaturized Implantable Assist Devices

Background— Up to 30% of patients with end-stage heart failure experience biventricular failure that requires biventricular mechanical support. For these patients, only bulky extracorporeal or implantable displacement pumps or the total artificial heart have been available to date, which enables only limited quality of life for the patients. It was our goal to evaluate a method that would allow the use of 2 implantable centrifugal left ventricular assist devices as a biventricular assist system. Methods and Results— Seventeen patients have been implanted with 2 HeartWare HVAD pumps, 1 as a left ventricular assist device and 1 as a right ventricular assist device. Seventy-seven percent of the patients had idiopathic dilated or ischemic cardiomyopathy. Their age ranged from 29 to 73 years (mean 51.8±14.5 years), and 11 (64.7%) received intravenous catecholamine support preoperatively. The right ventricular assist device pump was implanted into the right ventricular free wall. The afterload of this pump was artificially increased by local reduction of the outflow graft diameter, and the effective length of its inflow cannula was reduced by the addition of two 5-mm silicon suture rings to the original HVAD implantation ring. All right ventricular assist device devices could be operated in appropriate speed ranges and delivered a flow of between 3.0 and 5.5 L/min. Thirty-day survival was 82%, and 59% of the patients could be discharged home after recovering from the operation. There was no clinically relevant hemolysis in any of the patients. Conclusions— Two HeartWare HVAD pumps can be used as a biventricular assist system. This implantable biventricular support gives the patients more comfort and mobility than usual biventricular ventricular assist devices with large and noisy displacement pumps.

Is Bridge to Recovery More Likely With Pulsatile Left Ventricular Assist Devices Than With Nonpulsatile-Flow Systems?

BACKGROUND Weaning from left ventricular assist devices (LVADs) after myocardial recovery in patients with idiopathic dilated cardiomyopathy is a clinical option. With the broad application of continuous-flow pumps, we observed a decrease in the numbers of possible LVAD explanations due to myocardial recovery in these particular patients. We investigated this phenomenon and its causes. METHODS Between July 1992 and December 2009, 387 patients (age, 0.1 to 82 years) with idiopathic dilated cardiomyopathy underwent LVAD implantation at our institution. Patients were divided into two groups depending on whether they were weaned from the LVAD (group A) or not (group B). Univariate and multivariate analyses were performed on 24 different factors with a possible influence on myocardial recovery. RESULTS In 34 patients, LVAD removal due to myocardial recovery was performed with long-term stable cardiac function (weaning rate, 8.8%). Patients with a pulsatile-flow LVAD had an almost threefold chance for myocardial recovery (odds ratio, 2.719; 95% confidence interval, 1.182 to 6.254) than patients who received continuous-flow devices. Younger patients had significantly higher recovery rates than older patients (odds ratio, 1.036; 95% confidence interval, 1.016 to 1.057). CONCLUSIONS Pulsatile-flow LVADs and young age were important factors for myocardial recovery in idiopathic dilated cardiomyopathy patients in our analysis. Further studies should investigate whether pulsatility in itself or the different degrees of left ventricular unloading by the two types of systems play a role in myocardial recovery.

Relation of cerebral tissue oxygenation index to central venous oxygen saturation in children

ObjectiveTo evaluate the relationship between the cerebral tissue oxygenation index measured by near-infrared spectroscopy and central venous oxygen saturation (SvO2) after corrective surgery of congenital heart defects in children.DesignProspective observational clinical study.SettingA tertiary neonatal and paediatric intensive care unit for paediatric cardiology.PatientsNeonates and children consecutively admitted to the paediatric cardiology intensive care unit after corrective surgery of non-cyanotic congenital heart defects.Measurements and resultsForty-three children were studied. Cerebral tissue oxygenation index, measured non-invasively by near-infrared spectroscopy, was compared to SvO2, measured by a catheter placed in the right atrium, and to haemodynamic and respiratory parameters. Pearson’s correlation coefficients and p values were calculated. Simultaneously measured values for SvO2 (62.2±9.8%, 39.8–80.4%) and cerebral tissue oxygenation index (56.7±8.8%, 35.8–71.2%) showed a significant correlation (r=0.52, p<0.001).ConclusionCerebral tissue oxygenation index and SvO2 are not interchangeable parameters, but cerebral tissue oxygenation index reflects the haemodynamic influence on cerebral oxygenation after cardiovascular surgery. Further work is necessary to confirm the clinical role of continuous non-invasive measurement of cerebral tissue oxygenation index with regard to the variations of global systemic oxygen consumption after cardiac surgery in children.

Autograft Reinforcement to Preserve Autograft Function After the Ross Procedure A Report From the German-Dutch Ross Registry

Background— Autograft reinforcement interventions (R) during the Ross procedure are intended to preserve autograft function and improve durability. The aim of this study is to evaluate this hypothesis. Methods and Results— 1335 adult patients (mean age:43.5±12.0 years) underwent a Ross procedure (subcoronary, SC, n=637; root replacement, Root, n=698). 592 patients received R of the annulus, sinotubular junction, or both. Regular clinical and echocardiographic follow-up was performed (mean:6.09±3.97, range:0.01 to 19.2 years). Longitudinal assessment of autograft function with time was performed using multilevel modeling techniques. The Root without R (Root−R) group was associated with a 6× increased reoperation rate compared to Root with R (Root+R), SC with R (SC+R), and without R (SC-R; 12.9% versus 2.3% versus 2.5%.versus 2.6%, respectively; P<0.001). SC and Root groups had similar rate of aortic regurgitation (AR) development over time. Root+R patients had no progression of AR, whereas Root−R had 6 times higher AR development compared to Root+R. In SC, R had no remarkable effect on the annual AR progression. The SC technique was associated with lower rates of autograft dilatation at all levels of the aortic root compared to the Root techniques. R did not influence autograft dilatation rates in the Root group. Conclusions— For the time period of the study surgical autograft stabilization techniques preserve autograft function and result in significantly lower reoperation rates. The nonreinforced Root was associated with significant adverse outcome. Therefore, surgical stabilization of the autograft is advisable to preserve long-term autograft function, especially in the Root Ross procedure.

Extracorporeal membrane oxygenation for intraoperative cardiac support in children with congenital heart disease

OBJECTIVES Extracorporeal membrane oxygenation (ECMO) is commonly used in children to allow recovery from ischemic injury or cardiac surgery, to support the circulation in case of end-stage cardiomyopathy, as bridge-to-bridge therapy and as bridge to transplantation as well. It has achieved success in providing cardiac support for these kind of patients with expected mortality due to severe myocardial dysfunction. In this modern era, ECMO support should be considered an important option for children with cardiopulmonary failure refractory to medical therapy or resuscitation. We report our experience in pediatric patients supported by ECMO for intraoperative cardiac failure between November 1991 and December 2006. METHODS AND RESULTS Sixty-six patients with a mean age of 5.2+/-4 years (range: 1 day-17 years) and mean weight of 14.3+/-11 kg (range: 2.8-69 kg) had intraoperative ECMO support for failure to wean off cardiopulmonary bypass (n=46, 69.7%), low cardiac output syndrome (n=8, 12.1%), isolated right ventricular failure (n=6, 9.1%), isolated left ventricular failure (n=3, 4.5%), malignant arrhythmia (n=1, 1.5%) and pulmonary hypertension (n=2, 3.1%). Mean duration of ECMO support was 5.1+/-3 days. Overall 30 (45.4%) patients were successfully weaned off ECMO and survived to decannulation. Overall 6 (9.1%) patients were successfully bridged to heart transplantation while on ECMO support. Thirty patients died (54.4%) (16 while on ECMO and 14 after decannulation) because of multi-factorial complications, i.e. cerebral hemorrhage, pulmonary failure, consumption coagulopathy and therapy-resistant myocardial insufficiency, leding to an overall hospital mortality rate of 45.4%. Mean survival time after decannulation was 28+/-16 h. Overall survival rate on ECMO as bridge to recovery and transplantation has been 54.5% with successful hospital discharge of patients. CONCLUSIONS Our experience shows that ECMO support can be offered intraoperatively to any children after palliative or corrective surgery for congenital heart disease with potentially reversible pulmonary, cardiac or cardiopulmonary failure. In the majority of patients who did not survive late after weaning from ECMO support, significant myocardial dysfunction persisted or pulmonary hypertensive events. Nevertheless, an acceptable proportion of patients who were successfully weaned from ECMO ultimately survived to leave the hospital.

The practical clinical value of three-dimensional models of complex congenitally malformed hearts

OBJECTIVE Detailed 3-dimensional anatomic information is essential when planning strategies of surgical treatment for patients with complex congenitally malformed hearts. Current imaging techniques, however, do not always provide all the necessary anatomic information in a user-friendly fashion. We sought to assess the practical clinical value of realistic 3-dimensional models of complex congenitally malformed hearts. METHODS In 11 patients, aged from 0.8 to 27 years, all with complex congenitally malformed hearts, an unequivocal decision regarding the optimum surgical strategy had not been reached when using standard diagnostic tools. Therefore, we constructed 3-dimensional virtual computer and printed cast models of the heart on the basis of high-resolution whole-heart or cine magnetic resonance imaging or computed tomography. Anatomic descriptions were compared with intraoperative findings when surgery was performed. RESULTS Independently of age-related factors, images acquired in all patients using magnetic resonance imaging and computed tomography proved to be of sufficient quality for producing the models without major differences in the postprocessing and revealing the anatomy in an unequivocal 3-dimensional context. Examination of the models provided invaluable additional information that supported the surgical decision-making. The anatomy as shown in the models was confirmed during surgery. Biventricular corrective surgery was achieved in 5 patients, palliative surgery was achieved in 3 patients, and lack of suitable surgical options was confirmed in the remaining 3 patients. CONCLUSION Realistic 3-dimensional modeling of the heart provides a new means for the assessment of complex intracardiac anatomy. We expect this method to change current diagnostic approaches and facilitate preoperative planning.

Major Adverse Cardiac and Cerebrovascular Events After the Ross Procedure A Report From the German-Dutch Ross Registry

Background— The purpose of the study is to report major cardiac and cerebrovascular events after the Ross procedure in the large adult and pediatric population of the German-Dutch Ross registry. These data could provide an additional basis for discussions among physicians and a source of information for patients. Methods and Results— One thousand six hundred twenty patients (1420 adults; 1211 male; mean age, 39.2±16.2 years) underwent a Ross procedure between 1988 and 2008. Follow-up was performed on an annual basis (median, 6.2 years; 10 747 patient-years). Early and late mortality were 1.2% (n=19) and 3.6% (n=58; 0.54%/patient-year), respectively. Ninety-three patients underwent 99 reinterventions on the autograft (0.92%/patient-year); 78 reinterventions in 63 patients on the pulmonary conduit were performed (0.73%/patient-year). Freedom from autograft or pulmonary conduit reoperation was 98.2%, 95.1%, and 89% at 1, 5, and 10 years, respectively. Preoperative aortic regurgitation and the root replacement technique without surgical autograft reinforcement were associated with a greater hazard for autograft reoperation. Major internal or external bleeding occurred in 17 (0.15%/patient-year), and a total of 38 patients had composite end point of thrombosis, embolism, or bleeding (0.35%/patient-year). Late endocarditis with medical (n=16) or surgical treatment (n=29) was observed in 38 patients (0.38%/patient-year). Freedom from any valve-related event was 94.9% at 1 year, 90.7% at 5 years, and 82.5% at 10 years. Conclusions— Although longer follow-up of patients who undergo Ross operation is needed, the present series confirms that the autograft procedure is a valid option to treat aortic valve disease in selected patients. The nonreinforced full root technique and preoperative aortic regurgitation are predictors for autograft failure and warrant further consideration. Clinical Trial Registration— URL: http://www.clinicaltrials.gov. Unique identifier: NCT00708409.

Evaluation of the HeartWare HVAD centrifugal pump for right ventricular assistance in an in vitro model.

We have developed a method that allows the use of a commercially available implantable left ventricular assist device (LVAD; HeartWare HVAD) for right ventricular (RV) assistance. A mock circulation was used to examine the flow characteristics of the system with different outflow diameters (10–4 mm). Furthermore, we looked for a material for safe and satisfactory reduction of the effective length of the inflow cannula for better fitting to the RV dimensions. Reduction of the outflow graft to an inner diameter of ∼5 mm adds as much resistance to the system that in patients with a normal pulmonary resistance, the pump would deliver between 3.5 and 7 L/min. We added two 5 mm silicon suture rings to the systems “apical” sewing ring to reduce the effective length of the inflow cannula. Connection of the pump to the anterior free wall of the right ventricle ensures good orientation of the inflow cannula within the RV cavity, with sufficient space to prevent the inflow cannula from suction to the opposite interventricular septum. The HeartWare LVAD pump seems also to be usable as a right ventricular assist device (RVAD) after a few, but important, modifications of the implant procedure.

Perfusion technique for nonhaemic cardiopulmonary bypass prime in neonates and infants under 6 kg body weight

Background: Cardiopulmonary bypass (CPB) in neonates and infants is associated with significant haemodilution when priming of the CPB circuit is accomplished without transfusion of homologous blood components. The degree of haemodilution and, thus, the requirements for blood transfusion may be reduced when the CPB circuit is miniaturized without compromising patient safety. Method: Between January 2002 and October 2003, selected neonates and small infants were operated on using a nonhaemic prime extracorporeal circuit. CPB priming volume could be reduced from 300 mL to 190 mL by using a dedicated neonatal CPB console with mast-mounted roller pump heads. Reduction of priming volume resulted from shortening of all CPB lines to the minimum, downsizing of all CPB lines, exclusion of unused CPB components, use of vacuum-assisted venous drainage and from close co-operation between the perfusionist, cardiac surgeon and anaesthesiologist. The reduction in priming volume was achieved without eliminating the arterial line filter as safety device. Results: A total of nine patients weighing between 3.2 and 5.9 kg (mean 4.7 kg) and with a body surface area of 0.22 - 0.35m2 (mean 0.29m2) were operated on with the use of the modified neonatal CPB circuit and a nonhaemic prime. Bypass time varied from 38 to 167 min (mean 96 min). The mean haematocrit on CPB was 22.5% with a range of 17 - 29%. The postoperative course of all patients was uneventful. Conclusion: A significant reduction in CPB priming volume makes nonhaemic prime CPB in neonates and small infants undergoing complex repair of congenital heart defects possible.

Blood transfusion determines postoperative morbidity in pediatric cardiac surgery applying a comprehensive blood-sparing approach

OBJECTIVE Recently we suggested a comprehensive blood-sparing approach in pediatric cardiac surgery that resulted in no transfusion in 71 infants (25%), postoperative transfusion only in 68 (24%), and intraoperative transfusion in 149 (52%). We analyzed the effects of transfusion on postoperative morbidity and mortality in the same cohort of patients. METHODS The effect of transfusion on the length of mechanical ventilation and intensive care unit stay was assessed using Kaplan-Meier curves. To assess whether transfusion independently determined the length of mechanical ventilation and length of intensive care unit stay, a multivariate model was applied. Additionally, in the subgroup of transfused infants, the effect of the applied volume of packed red blood cells was assessed. RESULTS The median length of mechanical ventilation was 11 hours (interquartile range, 9-18 hours), 33 hours (interquartile range, 18-80 hours), and 93 hours (interquartile range, 34-161 hours) in the no transfusion, postoperative transfusion only, and intraoperative transfusion groups, respectively (P < .00001). The corresponding median lengths of intensive care unit stay were 1 day (interquartile range, 1-2 days), 3.5 days (interquartile range, 2-5 days), and 8 days (interquartile range, 3-9 days; P < .00001). The multivariate hazard ratio for early extubation was 0.24 (95% confidence interval, 0.16-0.35) and 0.37 (95% confidence interval, 0.25-0.55) for the intraoperative transfusion and postoperative transfusion only groups, respectively (P < .00001). In addition, the cardiopulmonary time, body weight, need for reoperation, and hemoglobin during cardiopulmonary bypass affected the length of mechanical ventilation. Similar results were obtained for the length of intensive care unit stay. In the subgroup of transfused infants, the volume of packed red blood cells also independently affected both the length of mechanical ventilation and the length of intensive care unit stay. CONCLUSIONS The incidence and volume of blood transfusion markedly affects postoperative morbidity in pediatric cardiac surgery. These results, although obtained by retrospective analysis, might stimulate attending physicians to establish stringent blood-sparing approaches in their institutions.