Right Ventricular Outflow Tract Position Research Articles

Conduits for Right Ventricular Outflow Tract Reconstruction in Infants and Young Children.

Purpose of Review: Right ventricular outflow tract (RVOT) reconstruction remains a challenge due to the lack of an ideal conduit. Data and experience are accumulating with each passing day. Therefore, it is necessary to review this topic from time to time. This is a 2021 update review focused on the history, evolution, and current situation of small-sized conduits (≤ 16 mm) for RVOT reconstruction in infants and young children.Recent Findings: Currently, the available small-sized (≤16 mm) conduits can meet most clinical needs. Homograft is still a reliable choice for infants and young children validated by a half-century clinical experience. As an alternative material, bovine jugular vein conduit (BJVC) has at least comparable durability with that of homograft. The performance of expanded polytetrafluoroethylene (ePTFE) is amazing in RVOT position according to limited published data. The past century has witnessed much progress in the materials for RVOT reconstruction. However, lack of growth potential is the dilemma for small-sized conduits. Tissue-engineering based on cell-free scaffolds is the most promising technology to obtain the ideal conduit.Summary: No conduit has proved to have lifelong durability in RVOT position. We are far from the ideal, but we are not in a state of emergency. In-depth clinical research as well as innovation in material science are needed to help improve the durability of the conduits used in infants and young children.

Outcomes of Pregnancy After Right Ventricular Outflow Tract Reconstruction With an Allograft Conduit

BackgroundThere is no published evidence on pregnancy after right ventricular outflow tract (RVOT) reconstruction with an allograft. ObjectivesThe aim of this study was to describe pregnancy outcomes in women with allografts in the RVOT position. MethodsA retrospective cohort study of consecutive female patients who received allografts in the RVOT position was conducted. All patients between 18 and 50 years of age were screened for cardiac, obstetric, and fetal outcomes of completed (≥20 weeks’ gestation) pregnancies. ResultsIn total, 196 women met the inclusion criteria, of whom 56 had 89 completed pregnancies. Information could be retrieved in 84 cases (94.4%). Mean maternal age was 29.6 ± 4.3 years, with 80 patients (95.2%) in New York Heart Association functional class I or II. The most common diagnosis was tetralogy of Fallot. All women survived pregnancy. There were 2 cases (2.4%) of heart failure (arrhythmic and diastolic dysfunction), 1 case (1.2%) of infection (chorioamnionitis), and 3 cases (3.6%) of pre-eclampsia. No other cardiac or obstetric events were reported. All children were born alive at a median gestational age of 38.4 weeks (interquartile range: 36.9 to 39.6 weeks), with a median birthweight of 2,930 g (interquartile range: 2,535 to 3,385 g). Seventeen (20.2%) were small for gestational age, and 20 (23.8%) were premature. Neonatal death was reported in 2 children (2.5%). Preconception pulmonary regurgitation was associated with an increased probability of pre-term labor (odds ratio: 2.610; 95% confidence interval: 1.318 to 5.172). Compared with the general Dutch population, pre-term delivery (25.0% vs. 7.4%, p < 0.001) and children small for gestational age (20.2% vs. 10.0%, p = 0.002) were more common. ConclusionsWomen in good cardiac health after RVOT reconstruction with allografts can safely experience pregnancy and labor. The higher incidence of pre-term delivery and children small for gestational age warrants special attention.

23 Right ventricular outflow tract elan conduit: the five year scotland experience

Background The management of the right ventricular outflow tract (RVOT) is a common feature in congenital cardiac surgery. A number of valved conduits are available. We reviewed the outcomes of the Vascutek RVOT Elan Conduit in patients from a specialist congenital surgical centre. Methods Between 2010 and 2011, 25 patients (13 male, mean age: 25.5 years) received an Elan conduit in the RVOT position. 24 reported previous open cardiac surgery. Most common diagnosis was Tetralogy of Fallot (n=19 (76%)). Results The mean follow up period was 4.96 years. 24 (96%) patients were alive at the time of censorship. 16 adverse events were noted and defined as haemodynamically significant conduit and/or valve stenosis (n=12), death (n=1) and bacterial endocarditis (n=3). 12 (48%) patients required re-intervention (10 transcatheter pulmonary valve replacements [8 Medtronic Melody and 2 Edwards Sapien] and 2 surgical pulmonary homografts). Mean time to re-intervention 1.7 years (range 0.25 – 4.36 years) Conclusion This review of RVOT Elan conduits demonstrates that in a significant proportion of patients there is short interval to re-intervention due to haemodynamically significant conduit and/or valve stenosis. (Figures 1 and 2) The conduit was technically attractive for transcatheter intervention. Other centres have published favourable results in the first 12 months after surgery. There are no other reported outcomes after this period. Our review suggests that ongoing frequent clinical assessment is required and should continue beyond the first 12 months. The Elan conduit is no longer in production and the search for the ideal valved RVOT conduit continues at a time when homograft availability is becoming an increasing challenge.

Inadequacy of fluoroscopy and electrocardiogram in predicting septal position in RVOT pacing – Validation with cardiac computed tomography

BackgroundElectrocardiographic (ECG) and fluoroscopic criteria, which are the only available guides to achieve a true septal position during right ventricular outflow tract (RVOT) pacing, have been infrequently validated. We sought to validate these using cardiac computed tomographic angiography (CTA) to confirm lead position within the RVOT septum. MethodsForty-four patients with permanent pacemaker leads in the RVOT position underwent CTA. Lead positions in RVOT were classified as anterior, free wall, or septal location. Fluoroscopic images were obtained in 4 standard views. ResultsOnly 19 (43%) patients had lead in true septal position within the RVOT in CTA while 25 patients (57%) were found to have an anterior lead location. Mean QRS axis, QRS duration, negative QRS in lead I, and notching in inferior leads were not significantly different between the two groups. The standard fluoroscopic LAO view showed a rightward-directed lead not only in all 19 patients with septal location, but also in 14/25 patients in the anterior location (p=0.22), and thus had a sensitivity of 100% but specificity of only 16% in predicting true septal position. The posteriorly directed lead in left lateral view was more accurate in predicting true septal position with good sensitivity (73.7%) and excellent specificity (80%). ConclusionsThis study, using validation with CTA, showed that conventional ECG criteria and fluoroscopy are inaccurate in differentiating septal from anterior RVOT pacing. The fluoroscopic lateral view, as corroborated by CTA, is more reliable than the LAO view in predicting septal lead placement.

Comparison between homografts and Freestyle(R) bioprosthesis for right ventricular outflow tract replacement in Ross procedures

Although data from large series indicate the satisfactory performance of bioprosthetic valves in the right ventricular outflow tract (RVOT), replacement of the pulmonary valve in adult patients undergoing the Ross procedure is usually performed with pulmonary allografts. We evaluated the outcomes of homografts vs. bioprosthetic RVOT replacement after the Ross procedure in adults. Between 1996 and 2011, a total of 186 adult patients (141 male; mean age 44 ± 10 years) underwent aortic root replacement with a pulmonary autograft. The RVOT was replaced with a homograft in 113 patients and with stentless bioprostheses (Medtronic Freestyle(®)) in 73. Patients were followed for a mean of 6 years (range 1-15 years; 1106 patient years). Twelve patients required reintervention owing to dysfunction of the RVOT replacement, which was caused by endocarditis (n = 4), degeneration (n = 2) or stricture at the proximal suture line (n = 6). For homografts, the incidence of reintervention was 1 in 150 patient years, compared with 1 in 36 patient years for stentless bioprostheses (P = 0.007). The median gradient was 15 mmHg for the homograft group and 24 mmHg for bioprosthesis (P < 0.0001). The incidence of gradients >40 mmHg was 10-fold higher in the bioprosthetic group. Patients with bioprostheses in the RVOT position after the Ross procedure showed a significantly higher risk of reintervention or pulmonary valve dysfunction. The main problem, early development of a stricture at the proximal suture line, has to be solved to achieve satisfactory bioprosthetic function in the RVOT.

The Stentless Porcine Aortic Root for Reconstruction of Right Ventricular Outflow Tract

There are various congenital cardiac diseases that require repeat reconstruction of the right ventricular outflow tract (RVOT). Several options are available for RVOT reconstruction. We present the technique of utilizing the stentless porcine aortic root (Prima; Edwards Lifesciences, Irvine, CA; Freestyle; Medtronic, Minneapolis, MN) for RVOT reconstruction. The porcine aortic root was initially developed for replacement and reconstruction of the aortic root. However, it was subsequently recognized to be versatile enough for RVOT reconstruction. 1 There are 2 commercially available porcine aortic roots, the Freestyle (available in diameters 19‐29 mm) and Prima (available in diameters 21‐29 mm). WeroutinelyusetheFreestyle19-mmconduit,andPrimafor all other size conduits larger than 19 mm. Patients with tetralogy of Fallot, truncus arteriosus, as well as those undergoingaRossprocedure,arecandidatesforthisconduit.Itcan be used for replacement of stenotic and calcified conduits, and also to provide a competent pulmonary valve in the RVOT position in patients who have had a previous transannular patch. We use published nomograms to determine the size of pulmonary valve required by body surface area and then try to upsize it up to a Z-score 2 (range 1t o 3). We do not upsize it larger than a Z-score 3 because this has the potential for sternal compression and valve failure. 2 The reoperative techniques are standardized. We obtain preoperative echocardiogram and either a cardiac catheterization or a magnetic resonance imaging scan. These studies help us determine any additional procedures that might need to be done at the time of the conduit replacement. The groin vesselsarealsoevaluatedwithduplexstudies.Thepositionof the current conduit in relationship to the sternum is also noted.

192 Right ventricular septal pacing – success rate and influence to LV electrical activation

Right ventricular (RV) apex pacing is associated with LV dyssynchrony. Alternate RV pacing sites (mid RV septum; the RV outflow tract (RVOT)) were considered, with no clear benefit. The aim of this study is to find a reliable method of septal lead placement ant to identify those pacing sites which provide a better LV electrical activation. 50 consecutive patients reffered for pacemaker implants due to AV block were included. Patients with history of heart failure or LVEF<50% at implant were excluded. All patients had RV leads placed in septal position. RV septum and RVOT were mapped during implant searching for the narrowest paced QRS with an axis as close to normal as possible. Pacing lead position was evaluated during implant using fluoroscopy (AP and LAO 40°) and than by 12 lead ECG and echo. Intra LV dyssinchrony was evaluated during pacing using SPWMD in parasternal short axis view and TDI septal to lateral t. Paced QRS duration and axis were also recorded. A correlation was sought between lead position evaluated by Rx and by echo and between paced QRS duration and axis and LV dyssunchrony. 92%(46) of the patients had the RV lead in septal position (32 in mid RV and 14 in RVOT) while 8% (4 pts) had the RV lead on the RVOT free wall as shown by echo. An anteriorly oriented lead in the left anterior oblique fluoroscopic projection was specific for free wall position while a positive QRS in DI in RVOT position was suggestive for free wall position on the ECG. No correlation was made between paced QRS axis and LV dyssinchron. A QRS duration of>160 ms was associated with significant LV dyssinchrony (SPWMD>130 ms and septal to lateral t>70 ms). RV lead placement on the RV septum can be reliably achieved using a specialy shaped stilet and LAO projection for confirmation. A wide paced QRS is correlated with significant intra LV dyssinchrony and therefore the pacing site with the narrowest QRS should be sought.

Inaccuracy of radiological and ECG criteria for right ventricular outflow tract implantation of pacemaker leads

We present three cases of active fixation pacemaker lead implantation, where the leads were believed to be inserted in the right ventricular outflow tract (RVOT) septal position, using established radiological criteria. However, when the exact location of the leads was documented by three-dimensional echocardiography, true septal RVOT position was achieved in only one patient. In the other two patients, the leads were, in fact, implanted into the RVOT anterior free wall. The electrocardiogram criteria were not able to identify the septal position from the anterior RVOT free wall position.

Randomized comparison of defibrillation thresholds from the right ventricular apex and outflow tract

Implantable cardioverter-defibrillator (ICD) leads are traditionally placed in the right ventricular apex (RVA), in part because this is considered the preferred vector for minimizing defibrillation threshold (DFT). However, if adequate DFT safety margins are attainable, ICD leads placed in the right ventricular outflow tract (RVOT) might confer advantages if frequent ventricular pacing is anticipated. The purpose of this study was to compare RVA with RVOT transvenous ICD lead position on DFT. This was a prospective, randomized, crossover study of RVA versus RVOT DFT in 33 patients undergoing left pectoral ICD placement. A binary search algorithm was used to measure DFT, with initial lead position tested in randomized order. The relationship between RVOT position and DFT was assessed by evaluation of the distance between RVA and RVOT. The study population had a mean age of 59 ± 12 years and ejection fraction of 33% ± 14%. Mean DFT in the RVA was 9.8 ± 7.3 J versus 10.8 ± 7.2 J in the RVOT (P = .53), with no correlation between RVOT location and DFT. The study found no evidence that ICD lead placement in the RVOT is associated with significantly higher DFT than lead placement in the RVA.