Stent expansion of restrictive Fontan conduits to nominal diameter and beyond.

BACKGROUND: Mechanical factors may cause bottlenecks in a Fontan circuit. Extracardiac conduits (ECC) are placed at a young age, but the materials do not allow growth. Restriction in ECC dimensions may deteriorate the function of the circuit. AIMS: This study aimed to evaluate the feasibility and safety of stent expansion of an ECC to the nominal dimension at the time of implant and, if possible, beyond nominal. METHODS: Retrospective, single-center observational review of all ECC Fontan patients who received a stent to expand a previously placed surgical conduit. RESULTS: A total of 44 restrictive conduits were stented over a 14-year study period with a median of 11.8 (interquartile ranges [IQR]: 9.1-13.8) years after ECC placement. Cross-sectional areas were a median of 30% (IQR: 21-42) smaller than the originally placed ECC; there was no gradient in 23/44 patients and in 21/44, a minimal gradient of 1.3 ± 0.5 (range 1-3 mmHg). All conduits could be enlarged with a significant (p < 0.0001) increase in diameter from 13.6 ± 1.8 to 19.2 ± 1.2 mm, corresponding to a median cross-sectional area increase of 171% (IQR: 153-220). In three patients where the conduits were not contracted, expansion of between 127% and 165% was obtained. There were no conduit ruptures and only one minor complication. CONCLUSIONS: ECC in some Fontan patients become smaller than nominal over time, usually without overt symptoms. The dimensions of ECC's can be safely and significantly increased to nominal or even beyond employing stenting. It allows adjustment of ECC dimensions to compensate for somatic growth.

Validating the Concept of Mechanical Circulatory Support with a Rotary Blood Pump in the Inferior Vena Cava in an Ovine Fontan Model.

Right-sided mechanical support of the Fontan circulation by existing devices has been compounded by the cross-sectional design of vena cava anastomosis to both pulmonary arteries. Our purpose was to investigate whether increasing inferior vena cava (IVC) flow with a rotary blood pump in the IVC only in an ovine animal model of Fontan would lead to acceptable superior vena cava (SVC) pressure. To achieve this, a Fontan circulation was established in four female sheep by anastomosing the SVC to the main pulmonary artery (MPA) and by interposing a Dacron graft between the IVC and the MPA. A rotary blood pump was then introduced in the graft, and the effect of incremental flows was observed at increasing flow regimen. Additionally, to stimulate increased pulmonary resistance, the experience was repeated in each animal with the placement of a restrictive band on the MPA distally to the SVC and Dacron graft anastomosis. Circulatory support of IVC flow alone increased the systemic cardiac output significantly, both with and without banding, indicating the feasibility of mechanical support of the Fontan circulation by increasing the flow only in the inferior vena cava. The increase in SVC pressure remained within acceptable limits, indicating the potential effectiveness of this mode of support. The findings suggest that increasing the flow only in the inferior vena cava is a feasible method for mechanical support of the Fontan circulation, potentially leading to an increase in cardiac output with acceptable increases in superior vena cava pressure.

Mitral valve replacement in children: balancing durability and risk with mechanical and bioprosthetic valves.

OBJECTIVES: To investigate if there is still a place for bioprosthetic mitral valve replacement in children by comparing the prosthetic durability and transplant-free survival after bioprosthetic and mechanical mitral valve replacement. METHODS: We reviewed all mitral valve replacements in children between 1981 and 2020. Bioprosthetic mitral valve replacement cases were individually matched to mechanical mitral valve replacement cases. The incidence rate of a 2nd replacement was calculated using the cumulative incidence function that considered death or transplantation as a competing risk. RESULTS: The median age at implantation was 3.6 years (interquartile range 0.8-7.9) for the bioprosthetic valve cohort (n = 28) and 3 years (interquartile range 1.3-7.8) for the mechanical valve cohort (n = 28). Seven years after bioprosthetic mitral valve replacement, the cumulative incidence of death or transplantation was 17.9% [95% confidence interval (CI) 6.3-34.1] and the cumulative incidence of a 2nd replacement was 63.6% (95% CI 39.9-80.1). Seven years after mechanical mitral valve replacement, the cumulative incidence of death or transplantation was 28.6% (95% CI 13.3-46) and the cumulative incidence of a 2nd replacement was 10.7% (95% CI 2.6-25.5). Fifteen years after mechanical mitral valve replacement, the cumulative incidence of death or transplantation was 33.6% (95% CI 16.2-52.1) and the cumulative incidence of a 2nd replacement was 41.1% (95% CI 18.4-62.7). The cumulative incidence curves for bioprosthetic and mechanical mitral valve replacement were statistically different for a 2nd valve replacement (P < 0.001) but not for death or transplantation (P = 0.33). CONCLUSIONS: There is no difference in transplant-free survival after bioprosthetic and mechanical mitral valve replacement in children. The lifespan of bioprosthetic mitral valves remains limited in children because of structural valve failure due to calcification. After 15 years, 40% of mechanical valves were replaced, primarily because of patient-prosthesis mismatch related to somatic growth.

The European Registry for Patients with Mechanical Circulatory Support (EUROMACS): fourth Paediatric EUROMACS (Paedi-EUROMACS) report.

OBJECTIVES: The use of ventricular assist devices (VADs) in children is increasing. However, absolute numbers in individual centres and countries remain small. Collaborative efforts such as the Paedi-European Registry for Patients with Mechanical Circulatory Support (EUROMACS) are therefore essential for combining international experience with paediatric VADs. Our goal was to present the results from the fourth Paedi-EUROMACS report. METHODS: All paediatric (<19 years) patients from the EUROMACS database supported by a VAD were included. Patients were stratified into a congenital heart disease (CHD) group and a group with a non-congenital aetiology. End points included mortality, a transplant and recovery. Cox proportional hazard models were used to explore associated factors for mortality, cerebrovascular accident and pump thrombosis. RESULTS: A total of 590 primary implants were included. The congenital group was significantly younger (2.5 vs 8.0 years, respectively, P < 0.001) and was more commonly supported by a pulsatile flow device (73.5% vs 59.9%, P < 0.001). Mortality was significantly higher in the congenital group (30.8% vs 20.4%, P = 0.009) than in the non-congenital group. However, in multivariable analyses, CHD was not significantly associated with mortality [hazard ratio (HR) 1.285; confidence interval (CI) 0.8111-2.036, P = 0.740]. Pump thrombosis was the most frequently reported adverse event (377 events in 132 patients; 0.925 events per patient-year) and was significantly associated with body surface area (HR 0.524, CI 0.333-0.823, P = 0.005), CHD (HR 1.641, CI 1.054-2.555, P = 0.028) and pulsatile flow support (HR 2.345, CI 1.406-3.910, P = 0.001) in multivariable analyses. CONCLUSIONS: This fourth Paedi-EUROMACS report highlights the increasing use of paediatric VADs. The patient populations with congenital and non-congenital aetiologies exhibit distinct characteristics and clinical outcomes.

Reversal of Right Ventricular Remodeling After Correction of Pulmonary Regurgitation in Tetralogy of Fallot.

In the sheep model with pathophysiologic changes similar to patients with repaired TOF, severe PR leads to fibrotic changes in the RV. Pulmonary valve replacement reverses these fibrotic changes. Early valve replacement led to a quick RV recovery, and in time there was no difference in outcome between early and late valve replacement. These data support the benefit of valve replacement for RV function and suggest that there is a margin in the timing of the surgery. The fibrotic changes correlated well with the circulating biomarker PICP, which can have an added value in the clinical follow-up of patients with repaired TOF.

Heartmate 3 implantation in small patients: CT-guided chest diameter assessment.

In recent years, the Heartmate 3 (HM3) has largely replaced the use of other intracorporeal left ventricular assist devices in the adult field. Because the HM3 is larger than the Heartware Ventricular Assist Device, the general consensus was that for small patients, the Heartware Ventricular Assist Device was the most appropriate implantable device option. Our goal was to describe our experiences with the successful implantation of the HM3 in 2 children, aged 9 and 11. We report on the chest cavity dimensions, as measured on computed tomography, that can be used to assess the feasibility of HM3 implantation in small patients.

Long-term outcomes of atrioventricular septal defect and single ventricle: A multicenter study.

OBJECTIVE: The study objective was to analyze survival and incidence of Fontan completion of patients with single-ventricle and concomitant unbalanced atrioventricular septal defect. METHODS: Data from 4 Dutch and 3 Belgian institutional databases were retrospectively collected. A total of 151 patients with single-ventricle atrioventricular septal defect were selected; 36 patients underwent an atrioventricular valve procedure (valve surgery group). End points were survival, incidence of Fontan completion, and freedom from atrioventricular valve reoperation. RESULTS: Median follow-up was 13.4 years. Cumulative survival was 71.2%, 70%, and 68.5% at 10, 15, and 20 years, respectively. An atrioventricular valve procedure was not a risk factor for mortality. Patients with moderate-severe or severe atrioventricular valve regurgitation at echocardiographic follow-up had a significantly worse 15-year survival (58.3%) compared with patients with no or mild regurgitation (89.2%) and patients with moderate regurgitation (88.6%) (P = .033). Cumulative incidence of Fontan completion was 56.5%, 71%, and 77.6% at 5, 10, and 15 years, respectively. An atrioventricular valve procedure was not associated with the incidence of Fontan completion. In the valve surgery group, freedom from atrioventricular valve reoperation was 85.7% at 1 year and 52.6% at 5 years. CONCLUSIONS: The long-term survival and incidence of Fontan completion in our study were better than previously described for patients with single-ventricle atrioventricular septal defect. A concomitant atrioventricular valve procedure did not increase the mortality rate or decrease the incidence of Fontan completion, whereas patients with moderate-severe or severe valve regurgitation at follow-up had a worse survival. Therefore, in patients with single-ventricle atrioventricular septal defect when atrioventricular valve regurgitation exceeds a moderate degree, the atrioventricular valve should be repaired.

Creation of the Fontan circulation in sheep: a survival model.

OBJECTIVES: Patients with a single ventricle survive thanks to the Fontan palliation. Nevertheless, there is a growing number of Fontan patients with progressive heart failure. To validate therapeutic options in these patients, we developed a chronic Fontan large animal model. METHODS: A Fontan circulation was surgically created in 15 sheep. The superior vena cava was anastomosed end-to-side to the pulmonary artery. The inferior vena cava was connected to the pulmonary artery by an ePTFE conduit, and the inferior vena cava-right atrium junction was ligated. RESULTS: Total cavopulmonary connection was successfully performed in all 15 animals. After creation of the Fontan circulation, central venous pressure increased from 4 [interquartile range (IQR) 3-6] mmHg to 16 (IQR 14-17) mmHg, mean arterial blood pressure decreased from 68 (IQR 54-75) mmHg to 52 (IQR 50-61) mmHg and cardiac output decreased from 5.1 (IQR 4.6-6.8) l/min to 1.7 (IQR 1.3-2.7) l/min. Five animals were electively sacrificed after a follow-up period of 21 weeks. CONCLUSIONS: These results demonstrate that it is feasible to create a chronic animal model with unsupported Fontan circulation. This animal model not only opens perspectives to investigate the pathophysiology of the failing Fontan circulation, but also provides the possibility to study therapeutic options such as the effect of mechanical circulatory support in the failing Fontan physiology.

Sheep can be used as animal model of regional myocardial remodeling and controllable work.

BACKGROUND: Pacing the right heart has been shown to induce reversible conduction delay and subse-quent asymmetric remodeling of the left ventricle (LV) in dogs and pigs. Both species have disadvantages in animal experiments. Therefore the aim of this study was to develop a more feasible and easy-to-use animal model in sheep. METHODS: Dual-chamber (DDD) pacemakers with epicardial leads on the right atrium and right ven-tricular free wall were implanted in 13 sheep. All animals underwent 8 weeks of chronic rapid pacing at 180 bpm. Reported observations were made at 110 bpm. RESULTS: DDD pacing acutely induced a left bundle branch block (LBBB) - like pattern with almost doubling in QRS width and the appearance of a septal flash, indicating mechanical dyssynchrony. Atrial pacing (AAI) resulted in normal ventricular conduction and function. During 8 weeks of rapid DDD pacing, animals developed LV remodeling (confirmed with histology) with septal wall thinning (-30%, p < 0.05), lateral wall thickening (+22%, p < 0.05), LV volume increase (+32%, p < 0.05), decrease of LV ejection fraction (-31%, p < 0.05), and functional mitral regurgitation. After 8 weeks, segmental pressure-strain-loops, representing regional myocardial work, were recorded. Switching from AAI to DDD pacing decreased immediately work in the septum and increased it in the lateral wall (-69 and +41%, respectively, p < 0.05). Global LV stroke work and dP/dtmax decreased (-27% and -25%, respectively, p < 0.05). CONCLUSIONS: This study presents the development a new sheep model with an asymmetrically remod-eled LV. Simple pacemaker programing allows direct modulation of regional myocardial function and work. This animal model provides a new and valuable alternative for canine or porcine models and has the potential to become instrumental for investigating regional function and loading conditions on regional LV remodeling.

A European study on decellularized homografts for pulmonary valve replacement: initial results from the prospective ESPOIR Trial and ESPOIR Registry data†.

OBJECTIVES: Decellularized pulmonary homografts (DPH) have shown excellent results for pulmonary valve replacement. However, controlled multicentre studies are lacking to date. METHODS: Prospective European multicentre trial evaluating DPH for pulmonary valve replacement. Matched comparison of DPH to bovine jugular vein (BJV) conduits and cryopreserved homografts (CH) considering patient age, type of heart defect and previous procedures. RESULTS: In total, 121 patients (59 female) were prospectively enrolled (August 2014-December 2016), age 21.3 ± 14.4 years, DPH diameter 24.4 ± 2.8 mm. No adverse events occurred with respect to surgical handling; there were 2 early deaths (30 + 59 years) due to myocardial failure after multi-valve procedures and no late mortality (1.7% mortality). After a mean follow-up of 2.2 ± 0.6 years, the primary efficacy end points mean peak gradient (16.1 ± 12.1 mmHg) and regurgitation (mean 0.25 ± 0.48, grade 0-3) were excellent. One reoperation was required for recurrent subvalvular stenosis caused by a pericardial patch and 1 balloon dilatation was performed on a previously stented LPA. 100% follow-up for DPH patients operated before or outside the trial (n = 114) included in the ESPOIR Registry, age 16.6 ± 10.4 years, diameter 24.1 ± 4.2 mm, follow-up 5.1 ± 3.0 years. The combined DPH cohort, n = 235, comprising both Trial and Registry data showed significantly better freedom from explantation (DPH 96.7 ± 2.1%, CH 84.4 ± 3.2%, P = 0.029 and BJV 82.7 ± 3.2%, P = 0.012) and less structural valve degeneration at 10 years when matched to CH, n = 235 and BJV, n = 235 (DPH 61.4 ± 6.6%, CH 39.9 ± 4.4%, n.s., BJV 47.5 ± 4.5%, P = 0.029).CONCLUSIONS: Initial results of the prospective multicentre ESPOIR Trial showed DPH to be safe and efficient. Current DPH results including Registry data were superior to BJV and CH.Trial registration clinicaltrials.gov identifier: NCT02035540.

Exercise capacity in left ventricular assist device patients with full and partial support.

Background In the present work, we investigated the exercise capacities of patients with partial flow left ventricular assist devices and its evolution over time. We then compared the exercise capacities of these patients with those of full support ventricular assist device patients. Methods We retrospectively analysed the data of maximal cardiopulmonary exercise tests of ten partial support patients (CircuLite Synergy® Micropump) collected before (PS0), at 3 (PS3) and 6 months (PS6) after implantation. The data were then compared with those of 17 patients (FS6) treated with a full support device (HeartMate II, Thoratec©). For this analysis, we considered the exercise tests performed at 6 months after pump implantation for both groups. Results Peak oxygen uptake evolved in the PS0, PS3 and PS6 groups from 11.5 ± 2.3 to 12.6 ± 2.8 and 12.0 ± 2.7 mL/kg/min, respectively. Heart rate peak increased from PS0 to PS6 (100 ± 17 bpm and 107 ± 22 bpm, p = 0.05). The comparative analysis between PS6 and FS6 groups showed no difference in terms of exercise performance (12.0 ± 2.7 and 13.5 ± 3.0 mL/kg/min, respectively), fatigue perception, ventilation efficiency slope, anaerobic threshold and oxygen uptake efficiency slope. The chronotropic response was also similar in both PS6 and FS6 groups. However, PS6 patients were more often treated with ß-blockers and therefore had lower heart rates at rest and at peak exercise than FS6 patients. Conclusions Exercise performance does not change after partial support implantation and stays stable over time. Partial and full support patients show similar exercise performances that attain 41% and 46% of the expected values, respectively.

Aortic wall thickness in patients with ascending aortic aneurysm versus acute aortic dissection.

OBJECTIVES: Recent studies have shown that aortic diameter alone is an insufficient parameter to identify patients at risk for aortic dissection. The aim of this study was to determine the value of the ratio of aortic diameter to medial wall thickness as a new marker of risk. METHODS: We obtained data from 181 patients with an ascending aortic aneurysm (n = 94) or an acute type A aortic dissection (n = 87), surgically treated at our institution (1996-2012). Measurements of the maximum aortic diameter and the medial wall thickness were conducted by retrospective review of preoperative imaging studies and histological specimens, respectively. RESULTS: Nearly 60% of the dissection patients had aortic diameters smaller than 50 mm. There was a significant negative linear correlation between medial wall thickness and aortic diameter (P = 0.01) in the dissection group only. Among patients with aortic diameters above 50 mm, dissection patients had significantly thinner aortic media (P = 0.04). Among patients with a mildly dilated aorta (>45 mm), the aortic diameter to medial wall thickness ratio was significantly higher in the dissection group (P = 0.04). CONCLUSIONS: Among patients with a dilatation of the ascending aorta of more than 45 and 49 mm, patients experiencing aortic dissection have a significantly higher aortic diameter to wall thickness ratio and a thinner aortic media, respectively. In the subset of patients with mild aortic dilatation, wall thickness might in the future serve as an additional parameter to help identify those patients who would benefit from prophylactic aortic surgery.