Subpulmonary Left Ventricle Research Articles

Diffuse fibrosis is common in the left, but not in the right ventricle in patients with transposition of the great arteries late after atrial switch operation.

In adult patients with transposition of the great arteries (TGA) late after atrial switch operation (AtSO), each of the ventricles is faced with a profoundly different pressure regimen from the one they are meant to support in normal conditions. The extent of diffuse fibrosis of the right ventricle (RV) and left ventricle (LV) in these patients remains incompletely investigated. Aim of this study was to quantify the degree of fibrosis of the unloaded LV and of the overloaded RV by determining the myocardial extracellular volume (ECV) with non-invasive techniques as T1 mapping. We determined ECV by cardiac magnetic resonance (CMR) in 10 patients (36.8 ± 5.3years old) with TGA late after AtSO, without relevant pulmonary stenosis, by acquiring T1-maps of the myocardium before and 10min after injection of Gadolinium-based contrast agent. ECV of the inferior wall (36% (33-41%)) and of the lateral wall (37% (35-39%)) of the LV was significantly increased compared to the ECV of the RV (27% (25-29%)), in both comparisons P < 0.0001. Long-time LV unloading following atrial switch procedures leads to severe myocardial fibrosis of the subpulmonary LV. T1 mapping CMR might be useful for selection of patients with atrial switch operation, in whom reestablishment of the LV as a systemic ventricle by staged arterial switch operation is planned. However larger studies and newer higher resolution methods for T1-mapping are needed to determine the role of ECV in the decision of a surgical intervention in this kind of population.

The paradox of choice in the surgical management of congenitally corrected transposition: what should we do with all of these options supported by little evidence?

Despite the conceptually proper physiology consisting of independent in-series pulmonary and systemic circuits, the prognosis in patients with unoperated congenitally corrected transposition of the great arteries (ccTGA) is reserved, even in the absence of associated defects. This is attributable to several factors. Although reports have described unoperated patients with normal or near-normal systemic right ventricular (RV) function in their 60s and beyond (1,2), it is the exception rather than the rule. Faced with a systemic circulation, the morphologic RV fails in one third of patients with no associated lesions by the fifth decade of life, and in two thirds with prior surgery for concomitant defects by 45 years of age (3). When confronted with chronic pressure overload, the systemic RV invariably undergoes hypertrophic remodelling. Owing to its limited coronary reserve from the concordant predominantly single right coronary circulation, myocardial oxygen/supply mismatch can promote subendocardial ischemia, progressive fibrosis, and ultimately, overt heart failure (4-6). Second, the tricuspid valve, again part of the systemic circulation, frequently displays Ebsteinoid features with propensity for regurgitation. While the direction of the causal relationship between tricuspid insufficiency and RV dysfunction remains debated, RV failure often follows systemic atrioventricular (AV) regurgitation (7,8). Incompetence of the tricuspid valve correlates with excess mortality, with poorer outcomes following AV valve replacement when the pre-operative RV ejection fraction is ≤40% (9). In addition, the AV conduction system is displaced and susceptible to AV block (10,11). Longterm studies report a prevalence of complete AV block of 24–39% (3,12), with an annual incidence estimated to be approximately 2% per year (13). Pacemakers are, therefore, frequently indicated. In the absence of cardiac resynchronization therapy, pacing of the subpulmonary left ventricle can alter the ventricular depolarization pattern thereby precipitating systemic AV valve regurgitation and heart failure (14). This confluence of factors contributes to the risk for ventricular arrhythmias and sudden death (15).

Acute and Midterm Outcomes of Transcatheter Pulmonary Valve Replacement for Treatment of Dysfunctional Left Ventricular Outflow Tract Conduits in Patients With Aortopulmonary Transposition and a Systemic Right Ventricle.

Transcatheter pulmonary valve replacement (TPVR) is an established therapy for dysfunctional right ventricular (RV) outflow tract conduits. TPVR in patients with congenitally corrected transposition of the great arteries, subpulmonary left ventricle, and left ventricular outflow tract (LVOT) conduit dysfunction has not been studied. Unique anatomic and physiological aspects of this population may contribute to distinct risks and outcomes. Across 10 US centers, 27 patients with a dysfunctional LVOT conduit were evaluated in the catheterization laboratory between December 2008 and August 2015 with the intent to perform TPVR. TPVR was successful in 23 patients (85%). Five serious adverse events occurred in 4 cases (15%), including pulmonary hemorrhage, hypotension requiring vasoactive support, conduit disruption requiring covered stent (n=2), and acute RV dysfunction with flash pulmonary edema. After TPVR, the LVOT peak systolic ejection gradient decreased from median of 35 to 17 mm Hg (P<0.001); pulmonary insufficiency was trivial/none in all but 1 patient, where it was mild. Worsening of systemic RV dysfunction or tricuspid regurgitation was seen in 12 patients (57%) and was associated with a significantly lower post-TPVR LVOT peak systolic ejection gradient (median 17 versus 21 mm Hg; P=0.02) and higher post-TPVR RV sphericity index (median 0.88 versus 0.52; P=0.004). Post-TPVR, there were 2 late deaths because of RV failure and 1 cardiac transplantation because of progressive RV dysfunction and tricuspid regurgitation. TPVR in dysfunctional LVOT conduits is feasible but associated with an important rate of TPV nonimplantation and procedural serious adverse events. Worsening systemic RV function and tricuspid regurgitation may develop after LVOT TPVR.

Left ventricular outflow tract obstruction and its impact on systolic ventricular function and exercise capacity in adults with a subaortic right ventricle

BackgroundIn biventricular hearts the filling and contractility of one ventricle affects the performance of the other. In this study, we compared right ventricular systolic function and exercise capacity in patients with a subaortic right ventricle (RV) in relation to the presence of a left ventricular outflow tract obstruction (LVOTO). MethodsRetrospective chart review of adults with congenitally corrected transposition of the great arteries (ccTGA) or with a previous atrial switch procedure for complete TGA (D-TGA). A LVOTO was defined by a peak instantaneous systolic gradient>20mmHg. Right and left ventricular ejection fraction (EF) were measured by cardiac magnetic resonance imaging (CMR), and exercise capacity as the predicted peak oxygen consumption (peak VO2) on a cycle ergometer. ResultsWe identified 79 clinically stable adults (age 33±10years, 70% male). Nine patients (11%) had cc-TGA and 70 patients had (89%) D-TGA. Thirteen patients (16%) had a LVOTO with a mean peak instantaneous systolic gradient of 43±22mmHg. Patients with a LVOTO had higher left (68±7% vs. 60±9%, p=0.01) and right ventricular EF (52±8 vs. 46±9%, p=0.05) by CMR compared to patients without LVOTO. In a multivariate regression analysis with left ventricular EF and LVOTO as predictors, only left ventricular EF was independently associated with right ventricular EF (correlation coefficient 0.41, p<0.01). The presence of a LVOTO was not associated with improved exercise capacity. ConclusionsIn adults with a subaortic RV, a pressure loaded subpulmonary left ventricle has a beneficial effect on systemic right ventricular EF.

NT-proBNP predicts mortality in adults with transposition of the great arteries late after Mustard or Senning correction.

The patients after Mustard and Senning corrections of transposition of the great arteries (TGA) are at an increased risk of unexpected death. The aim of this study was to identify markers allowing risk stratification of patients after atrial switch correction of TGA to provide them with optimum care. In this study, 87 patients were retrospectively evaluated after atrial switch correction of TGA followed-up between 2005 and 2015. The mortality during the follow-up was 9% (8 cardiac deaths). Markers significantly predictive of death using univariable Cox proportional hazard ratio survival analysis were: N-terminal pro-B-type natriuretic peptide (NT-proBNP), ejection fraction and end-diastolic dimension of the systemic right ventricle, mitral E, e', and s'. Surprisingly, the Doppler parameters of mitral valve in subpulmonary ventricle were more important for prognosis than those of systemic tricuspid valve. In multivariable analysis, the only independent predictors of mortality were NT-proBNP (P = .00048; AUC 0.97) and the velocity of early diastolic filling (mitral E) in subpulmonary ventricle (P = .01815; AUC 0.81). According to Kaplan-Meier survival analysis, patients with NT-proBNP > 1000 pg/ml are at high risk of death. Patients with mitral E < 68 cm/s are also at an increased risk of death. NT-proBNP is the most reliable prognostic mortality factor and should be measured regularly in TGA patients after Mustard or Senning correction. Diastolic filling velocity of the subpulmonary left ventricle (mitral E) may be more important for prognosis than systolic function of the systemic right ventricle.

Assessment of myocardial function using MRI-based feature tracking in adults after atrial repair of transposition of the great arteries: Reference values and clinical utility

BackgroundEchocardiographic parameters of ventricular deformation of the systemic right ventricle (sRV) predict adverse clinical outcome in patients after atrial repair of transposition of the great arteries (TGA). We assessed myocardial deformation on cardiac MRI (CMR) and correlated these with clinical and conventional CMR parameters in TGA patients. MethodsRetrospective analysis of CMR studies in 91 TGA patients (66% male; mean age 30.1±5.1years) at two tertiary adult congenital heart centers was conducted. Myocardial deformation was assessed by CMR-based feature tracking (FT), providing longitudinal (LS), radial (RS), and circumferential (CS) global strain for the sRV and the subpulmonary left ventricle. A subgroup of optimal TGA was defined (NYHA class I, NT-proBNP <300pg/ml, max. exercise work load ≥100watt, no significant clinical events) as a reference cohort. ResultsThere was a significant correlation between FT and conventional CMR parameters. Left ventricular ejection fraction (LVEF) correlated significantly with LV LS, RS, and CS (r between 0.24 and 0.34, p values between 0.03 and 0.005). sRVEF correlated with RV CS (r=0.56, p<0.001), and RV RS (r=0.32, p=0.007). QRS duration showed a negative correlation with RV CS (r=−0.53, p<0.001), LV RS (r=−0.34, p=0.008), and LV CS (r=−0.34, p=0.006). Reference values for the novel FT method in clinically optimal TGA patients are provided. ConclusionAssessment of myocardial function using CMR-based FT is feasible in TGA patients. FT measurements related to important prognostic clinical parameters. Furthermore, we provide for the first time reference values for TGA patients in an optimal clinical status.

Left ventricular regression after balloon atrial septostomy in d-transposition of the great arteries.

Balloon atrial septostomy (BAS) is an effective palliative procedure in children with transposition of the great arteries and poor intercirculatory mixing. While the subpulmonary left ventricle (LV) is known to regress with time in these newborns due to the declining afterload, it has not been studied how it behaves following BAS and a consequent decrease in preload. The study was designed to examine the effects of BAS on the LV in infants with simple d-transposition of the great arteries by serial 2D echocardiographic monitoring. This was a prospective echocardiographic follow-up study of all consecutive children with simple d-transposition of the great arteries who underwent BAS for restrictive interatrial communication and oxygen saturation below 75% between January 2014 and June 2015. Left ventricular mass estimation was done by M-mode transthoracic echocardiography before balloon septostomy and serially on follow-up till surgery. The median age of the 25 children studied was 4 days (1-95 days) when they underwent BAS. Twenty patients underwent arterial switch operation at a mean of 9 days from balloon septostomy. The mean baseline left ventricular mass was 47.9 g/m2, which decreased to 38.5, 36.2, 32.1, 32.4, 25.7 and 25.2 g/m2 on Days 1, 3, 6, 9, 12 and 15, respectively. The left ventricular mass decreased by 1.5 g/m2 every day during the first 2 weeks following balloon septostomy adjusted for the age of the child in days. Children who underwent BAS beyond 3 weeks of life had faster LV regression than those who underwent the procedure earlier (unstandardized regression coefficient β 0.892, P < 0.001). BAS is associated with accelerated regression of the LV in infants with simple d-transposition of the great arteries in the first 2 weeks after the procedure. Regression of the LV is faster in children who underwent BAS after 3 weeks of age.

P26 A baffle leak is a bonus?

Background There is a significant body of adult congenital patients born with transposition of the great arteries (TGA) who have undergone Mustard or Senning procedures requiring follow up. Long-term complications relating to the intra atrial baffles are frequent and baffle leaks may cause significant desaturation, exercise intolerance and increased risk of paradoxical emboli. However the clinical consequence of a baffle leak is often poorly understood and in some cases their presence may prove beneficial to the patient. We describe four cases in whom the decision to eliminate an atrial baffle leak was not clear-cut. Findings Four male patients, mean age 27 years, with a history of TGA underwent a Senning procedure in infancy (mean age 8 months). All patients were NYHA class 1, in sinus rhythm with no history of embolic events. Significant baffle leaks were identified on MRI and confirmed at cardiac catheterisation. Calculated Qp:Qs ranged from 1.5–3:1. Pulmonary artery pressure was normal in all cases. All 4 patients had a dilated left ventricle with well-preserved function and, interestingly, had a systemic right ventricle of relatively normal size with good function. Discussion A significant baffle leak, which behaves like an atrial septal defect, places a volume load on the posterior subpulmonary left ventricle. We postulate that this may actually be beneficial in supporting systemic right ventricular function. For a subset of patients intervention to abolish the leak could potentially precipitate right ventricular dysfunction. This must be offset against the potential implications of a significant left to right shunt. Careful investigation is required to appropriately diagnose, counsel and follow this patient group.

Criss-cross heart: Twisted anatomy by cardiovascular magnetic resonance

h o s c D a v A 27-year-old male with known congenitally corrected transposition of the great arteries was referred for further workup due to increasing arrhythmias. Cardiovascular magnetic resonance (CMR) showed situs solitus and atrioventricular (AV) and ventriculoarterial (VA) discordance, with the aorta lying anteriorly and to the right of the pulmonary trunk (Figure 1). An unusual alignment was found, with the right and left ventricular inflow tracts aligned almost perpendicular to one another, precluding imaging all four chambers in one plane. The systemic right ventricle was relatively hypoplastic and lay superior to the subpulmonary left ventricle. The findings were typical of a previously unnoticed criss-cross atrioventricular arrangement. A large nonrestrictive ventricular septal defect and severe pulmonary stenosis were also present;

Echocardiographic Determinants of the Clinical Condition in Patients with a Systemic Right Ventricle

Ventricular systolic and diastolic function, as measured by echocardiography, are diminished in patients with a systemic right ventricle (RV). As the clinical implications of these finding remained unknown, we aimed to identify echocardiographic parameters of systolic and diastolic ventricular function that are independent determinants of the clinical condition in these patients. Forty-six adult patients (61% male; mean age 33 [range 18-69] years) with a systemic RV underwent echocardiography to assess qualitative and quantitative systolic and diastolic function of the systemic RV and the subpulmonary left ventricle (LV). Uni- and multivariate linear regression analyses were performed to identify independent echocardiographic determinants for NYHA class, maximal exercise capacity (V'O(2peak)) and NT-proBNP levels. We found qualitative assessment of RV and LV function to be significantly associated with NYHA class (RV: β= 0.26; P = 0.05 and LV: β= 0.82; P < 0.01), V'O(2peak) (RV: β=-10.4; P < 0.05 and LV: β=-18.4; P < 0.05) and NT-proBNP levels (RV: β= 0.58; P < 0.01 and LV: β= 1.40; P < 0.001). Tricuspid annulus plane systolic excursion (TAPSE) was significantly associated with NYHA class (β=-0.92; P = 0.001), V'O(2peak) (β= 18.5; P = 0.05), and serum NT-proBNP levels (β=-1.00; P < 0.05). Associations between quantitative parameters of systolic subpulmonary LV function and clinical parameters were less distinct. We found no associations between RV and LV diastolic function and clinical parameters. Qualitative function of the systemic RV and the subpulmonary LV, and TAPSE, are determinants of clinical condition in patients with a systemic RV. These patients' clinical condition could not be determined by echocardiographically measured diastolic RV function, and systolic and diastolic LV function.

Left Ventricular Function in Patients with Transposition of the Great Arteries Operated with Atrial Switch

In patients operated with atrial switch for transposition of the great arteries (TGA), the left ventricle (LV) supports the pulmonary circulation and is thus pressure unloaded. Evaluation of LV function in this setting is of importance, as LV functional abnormalities have been documented and might contribute to development of symptoms. The ventricular contraction pattern in 14 Senning-operated TGA patients and 14 healthy controls was studied using tissue Doppler and magnetic resonance imaging. In the subpulmonary LV free wall, longitudinal strain was greater than circumferential strain (-23.6 +/- 3.6% vs. -19.1 +/- 3.2%, p = 0.002) as in the normal right ventricle (RV) (-30.7 +/- 3.3% vs. -15.8 +/- 1.3%, p < 0.001), but opposite to findings in the normal LV (-16.5 +/- 1.7% vs. -25.7 +/- 3.1%, p < 0.001). Subpulmonary strain and strain rate values were intermediate between those in the normal LV and RV. Ventricular free-wall torsion was reduced in the subpulmonary LV compared with both the normal LV (5.7 +/- 3.2 degrees vs. 16.7 +/- 5.6 degrees , p < 0.001) and RV (5.7 +/- 3.2 degrees vs. 11.4 +/- 2.6 degrees , p < 0.05). Furthermore, early diastolic filling of the subpulmonary LV differed from that of the normal LV. The subpulmonary LV displayed predominantly longitudinal shortening, as did its functional counterpart, the normal RV. However, the degree and rate of both longitudinal and circumferential shortening were intermediate between those of the normal LV and RV. This could represent a partial adaptation to the reduced pressure load. Decreased ventricular torsion and diastolic abnormalities might indicate subclinical ventricular dysfunction.

Cardiac defibrillation therapy for at risk patients with systemic right ventricular dysfunction secondary to atrial redirection surgery for dextro-transposition of the great arteries

To review techniques of implantable cardioverter-defibrillators (ICD) in patients after Mustard surgery for arterial transposition. Retrospective analysis of all Mustard patients receiving ICDs at our institution. Five patients (median age 24 years, range 19-35, 3 male) with systemic right ventricular dysfunction (sRV) dysfunction and New York Heart Association (NYHA) II and III, received ICDs. Implantation was performed transvenously in three patients, epicardial patches and subcutaneous arrays at surgery in two patients. Two patients required lead extraction and baffle stent angioplasty before ICD implantation. Defibrillation vectors incorporating the anterior sRV mass [i.e., sub-pulmonary left ventricle (pLV) to generator can, and between epicardial defibrillator patches], consistently achieved a minimum 10 joule(J) safety margin during defibrillation threshold (DFT) testing. Subcutaneous arrays and endocardial vectors that included a superior vena cava (SVC) electrode were less effective. One patient developed pulmonary oedema post-procedure. At a median 20 months, all patients were alive and in NYHA class II. Follow-up over 24 months documented multiple non-sustained ventricular tachycardia (VT) in the group and one patient had recurrent VT with aborted device therapy. Defibrillator implantation in Mustard patients is challenging. Sub-optimal defibrillation should be anticipated and can be overcome using vectors which integrate the RV mass and high-energy devices. A staged procedure involving pre-implant interventions or separate DFT tests, where indicated, may be better tolerated by patients.

Arterial switch operation after mustard procedures in adult patients with transposition of the great arteries: is it time to revise our strategy?

Background After the Mustard or Senning procedure, adults with transposition of the great arteries may have right ventricular failure and require consideration of new therapies. A 2-stage arterial switch operation (ASO) may be performed as an alternative to heart transplantation. This procedure is relatively successful in children, but little is known about the 2-stage ASO in adults. We report our experience in adults undergoing pulmonary arterial banding as the first stage of a planned 2-stage arterial switch procedure after a failed Mustard operation. Methods and results Three adult patients with systemic right ventricular failure late after Mustard procedures embarked, through pulmonary artery banding, on a course toward a 2-stage arterial switch at the Toronto General Hospital. Baseline clinical characteristics as well as preoperative hemodynamics were reviewed. Immediate perioperative and postoperative events, hemodynamic measurements, and clinical outcomes were also recorded. Two patients were banded acutely such that their morphologic left ventricular to right ventricular (LV/RV) systolic pressure ratios were >0.65 after the initial banding procedure. The subpulmonary left ventricle failed in both cases. In contrast, the third patient had a more gradual approach to pulmonary artery banding (PAB), with an initial LV/RV pressure ratio of 0.5, which eventually led to a successful conversion to an arterial switch procedure. Conclusions Our evidence suggests that in adult patients expected to undergo a 2-stage arterial switch procedure after a failed Mustard operation, acute PAB achieving near-systemic subpulmonary LV pressure leads rapidly to ventricular failure and failure of this treatment strategy. A more gradual approach to PAB may be required to achieve a successful outcome.