Hemodynamic simulation of complete transposition of the great arteries for optimal treatment strategies based on its circulatory physiology

Our study aimed to elucidate the role of different shunts and provide novel insights into optimal treatment approaches for complete transposition of the great arteries (TGA), which is characterized by unique and complicated circulatory dynamics. We constructed a computational cardiovascular TGA model and manipulated cardiovascular parameters, such as atrial septal defect (ASD) and patent ductus arteriosus (PDA) sizes, to quantify their effects on oxygenation and hemodynamics. In addition, ASD flow patterns were investigated as innovative indications for balloon atrial septostomy (BAS). Our model of TGA with an intact ventricular septum (TGA-IVS) showed that a large ASD can achieve sufficient mixing for survival without PDA, and the presence of PDA is detrimental to oxygen delivery. A treatment strategy for TGA-IVS that enlarges the ASD as much as possible by BAS and PDA closure would be desirable. In TGA with a ventricular septal defect (TGA-VSD), the VSD allows for higher oxygenation and reduces the detrimental effects of PDA on systemic circulation. In TGA-VSD, both strategies of enlarging the ASD by BAS with a closed PDA and adjusting the PDA in response to pulmonary vascular resistance (PVR) reduction without BAS may be effective. The simulated ASD flow patterns showed that the sharp peak left-to-right flow pattern in systole (σ-wave) reflected the hemodynamically significant ASD size, independent of PDA, VSD, and PVR. The ASD flow pattern visualized by Doppler echocardiography provides clinical insights into the significance of an ASD and indications for BAS, which are not readily apparent through morphological assessment.NEW & NOTEWORTHY Complete transposition of the great arteries (TGA) represents complex and unique circulation that is dependent on blood mixing through multiple interacting shunts. Consequently, the role of each shunt and the treatment strategy remain unclear. We developed a mathematical model of TGA circulation, revealing the significant influence of atrial septal defect (ASD) on oxygenation and hemodynamics. The blood flow pattern through the ASD reflects its hemodynamic impact and helps determine treatment strategies.

Significance of End-Diastolic Forward Flow in Patients With Repaired Tetralogy of Fallot - Its Interaction With the Left Ventricular Property and End Organ Damage

BACKGROUND

Although right ventricular (RV) enlargement may affect RV diastolic dysfunction assessed by end-diastolic forward flow (EDFF) in patients with repaired tetralogy of Fallot (TOF), EDFF may also be modified by left ventricular (LV) hemodynamics. We hypothesized that EDFF is affected by LV hemodynamics, not limited to RV diastolic stiffening.Methods and Results: Among 145 consecutive patients with repaired TOF who underwent catheterization, hemodynamic properties in 47 with consistent EDFF and 75 without EDFF were analyzed. Compared with patients without EDFF, those with EDFF had a large RV volume with a high regurgitant fraction. Although cardiac index and central venous pressure (CVP) were similar, contrast injection augmented CVP and LV end-diastolic pressure (EDP) in patients with vs. those without EDFF, suggesting compromised diastolic reserve. In patients with EDFF, the velocity-time integral (VTI) of EDFF was positively correlated with LVEDP and systemic vascular resistance, in addition to RV EDP. EDFF-VTI was correlated with hepatic venous wedge pressure and markers of hepatic dysfunction. Subanalysis of the older (≥6 years) half of the study cohort revealed that EDFF was associated with bi-atrial enlargement independent of RV volume, highlighting the pronounced role of EDFF on the diastolic property in the aged cohort.

CONCLUSIONS

EDFF-VTI in patients with repaired TOF reflects RV diastolic dysfunction, affected by the left heart system. EDFF-VTI indicates blood stagnation, which may be attributed to end-organ damage.

Predictors of liver cirrhosis and hepatocellular carcinoma among perioperative survivors of the Fontan operation

OBJECTIVE

Fontan-associated liver disease (FALD) is widely recognised as a common complication in patients long after the Fontan operation. However, data on the predictors of FALD that can guide its screening and management are lacking. The present study aimed to identify the predictors of liver cirrhosis (LC) and hepatocellular carcinoma (HCC) in post-Fontan patients.

METHODS

This was a multi-institutional retrospective cohort study. Clinical data of all perioperative survivors of Fontan operation before 2011 who underwent postoperative catheterisation were collected through a retrospective chart review.

RESULTS

A total of 1117 patients (538 women, 48.2%) underwent their first Fontan operation at a median age of 3.4 years. Postoperative cardiac catheterisation was conducted at a median of 1.0 year. During a median follow-up period of 10.3 years, 67 patients (6.0%) died; 181 (16.2%) were diagnosed with liver fibrosis, 67 (6.0%) with LC, 54 (4.8%) with focal nodular hyperplasia and 7 (0.6%) with HCC. On multivariable analysis, high central venous pressure (CVP) (HR, 1.28 (95% CI 1.01 to 1.63) per 3 mm Hg; p=0.042) and severe atrioventricular valve regurgitation (HR, 6.02 (95% CI 1.53 to 23.77); p=0.010) at the postoperative catheterisation were identified as independent predictors of LC/HCC.

CONCLUSIONS

Patients with high CVP and/or severe atrioventricular valve regurgitation approximately 1 year after the Fontan operation are at increased risk of developing advanced liver disease in the long term. Whether therapeutic interventions to reduce CVP and atrioventricular valve regurgitation decrease the incidence of advanced liver disease requires further elucidation.

Predictors of long-term mortality among perioperative survivors of Fontan operation

AIMS

The criteria for 'good' Fontan haemodynamics have been poorly defined in relation to long-term outcomes. The aim of this study was to identify the risk factors for mortality among haemodynamic parameters obtained early after the Fontan operation.

METHODS AND RESULTS

Clinical data of all perioperative survivors of the Fontan operation performed before 2011, from nine institutions, were collected through a retrospective chart review. In total, 1260 patients were included. The median age at the time of Fontan operation was 3.6 years. Post-operative cardiac catheterization was conducted in 1117 patients at a median period of 1.0 years after the operation. During the median follow-up period of 10.2 years, 107 patients died. The mortality rates at 10, 20, and 25 years after the operation were 5%, 12%, and 22%, respectively. On multivariable analysis, older age at the time of the operation {≥15 years, hazard ratio (HR) [95% confidence interval (CI)]: 3.2 (1.7-5.9)} and haemodynamic parameters obtained at post-operative catheterization, such as low ejection fraction [<30%, HR (95% CI): 7.5 (3.2-18)], low systemic oxygen saturation [<80%, HR (95% CI): 3.8 (1.6-9.1)], high central venous pressure [≥16 mmHg, HR (95% CI): 2.3 (1.3-3.9)], and low mean systemic arterial pressure [<60 mmHg, HR (95% CI): 3.0 (1.4-6.2)] were identified as independent predictors of mortality. The predictive model based on these parameters had a c-index of 0.75 at 10 years.

CONCLUSIONS

Haemodynamic parameters obtained at a median period of 1.0 years, post-operatively, can accurately identify patients with a high mortality risk, who may need intensive management to improve long-term outcomes.

KEY QUESTION

What defines 'worse' Fontan haemodynamics?

KEY FINDING

Older age at Fontan (≥15 years), low ejection fraction (<30%), low oxygen saturation (<80%), high central venous pressure (≥16 mmHg), and low mean systemic arterial pressure (<60 mmHg) were identified as independent predictors of mortality.

TAKE HOME MESSAGE

Haemodynamic parameters obtained at a median period of 1.0 years, post-operatively, can accurately identify patients with a high mortality risk, who may need intensive management to improve long-term outcomes.

Venous Properties in a Fontan Patient with Successful Remission of Protein-Losing Enteropathy

We present the case of a 1-year-old boy who developed protein-losing enteropathy (PLE) within 2 months of a fenestrated Fontan procedure. His fenestration rapidly closed despite bilateral pulmonary stenosis (BPS). Subsequent to PLE onset, both fenestration and the bilateral pulmonary artery were reconstructed, and the patient's PLE had been in remission, with additive use of medications, for more than 2 years. Notably, although fenestration closed again and central venous pressure (CVP) reduction was minimal, the surrogates of venous return resistance were markedly suppressed as shown by increased blood volume, reduced estimated mean circulatory filling pressure, and suppressed CVP augmentation against a contrast agent. Taken together, dynamic characteristics of venous stagnation, rather than the absolute value of CVP, were ameliorated by the pulmonary reconstruction and use of medications, suggesting a significant role of venous property in the physiology of PLE. In addition, simultaneous measures of CVP and ventricular end-diastolic pressure during the abdominal compression procedure suggested a limited therapeutic role of fenestration against PLE in this patient.

Echocardiogram Unmasked Hemodynamic Advantage of Atrial Pacing in Securing Ventricular Preload in a Fontan Patient with Junctional Rhythm

While the advancement of perioperative management has expanded Fontan candidacy, not all patients have a successful postoperative course. Our case was a right isomerism patient who could not leave the ICU due to high central venous pressure and low output syndrome. Initial observation of the monitor ECG showed his rhythm to be supraventricular, however, an echocardiogram indicated simultaneous contraction of the atrium and ventricle, implying a junctional rhythm. While neither central venous pressure nor blood pressure improved with temporary pacing, better central venous and pulmonary venous blood flow patterns during pacing unraveled its positive impact. The patient successfully left the ICU after permanent pacing implantation. Hemodynamic study revealed a beneficial impact of atrial pacing in securing cardiac output and ventricular preload, lowering central venous pressure, and shortening blood transit time, which is partly attributed to the optimization of the fenestration function in reservation of the preload. Our case emphasizes the significant advantage of atrial pacing in a failing Fontan patient with junctional rhythm by reducing venous congestion and maximizing the benefit of fenestration.

Portosystemic shunt with hyperammonemia and high cardiac output as a complication after Fontan surgery

In the late phase after Fontan surgery, organ dysfunction due to high central venous pressure (CVP) is a major clinical problem. We have described the cases of two patients with portosystemic shunts who exhibited hyperammonemia and high cardiac output associated with peripheral vasodilatation after Fontan surgery. A high CVP in these patients may have resulted in the formation of a portosystemic shunt. We performed coil embolization and balloon-occluded retrograde transvenous obliteration for each case. The possibility of a portosystemic shunt as a postoperative complication of Fontan surgery should always be considered. Early detection and therapeutic intervention seem necessary from the viewpoint of stabilizing the Fontan circulation and delaying the progression of liver disorder. <Learning objectives: A portosystemic shunt may develop due to the high central venous pressure after Fontan surgery independent of hepatic disorder and should be considered as a potential cause of unexplained hyperammonemia and high cardiac output status. Transcatheter closure of the portosystemic shunt may improve the clinical status.>.

Steroid-Refractory Protein-Losing Enteropathy with Gastrointestinal Bleeding in a Patient with Fontan Circulation

Protein-losing enteropathy (PLE) is one of the major complications after a Fontan operation. Some PLE patients suffer from concurrent gastrointestinal bleeding. An effective treatment regimen for such patients has not been established yet. Further, it remains unknown whether PLE and gastrointestinal bleeding coexist independently, or protein losing is associated with gastrointestinal bleeding. We report a 7-year-old steroid-refractory post-Fontan PLE case suggesting the latter pathogenesis together with a literature review.

Successful salvage of the left pulmonary artery in a neonate with isolated unilateral absence of the pulmonary artery

Isolated unilateral absence of the pulmonary artery (UAPA) is a congenital anomaly where involution of the extrapulmonary PA is insufficient and the intrapulmonary PA is only fed by the ductus arteriosus. Affected lung disorder causes complications years after ductus closure; thus, early diagnosis is of importance to avoid these complications. Here, we present the case of a male infant who was admitted to the neonatal intensive care unit because of transient tachypnea of the newborn and absence of the left PA (LPA) was indicated. Intensive echocardiography could detect neither the LPA nor the aortopulmonary collateral arteries to the left lung. Although the ductus was orthotopic with the right aortic arch, use of prostaglandin (PG) E1 unmasked the diagnosis of UAPA with bilateral ductus arteriosus. After ductal closure, delineation of the anatomy is not necessarily easy even with catheterization, whereas early use of PGE1 facilitates anatomical understanding by echocardiography, particularly early after birth. <Learning Objectives: While identification of disrupted pulmonary artery is often unsuccessful after ductal closure in the patients with unilateral absence of pulmonary artery, use of prostaglandin in the neonate with right aortic arch and large orthotropic right ductus arteriosus allowed successful recirculation of the disrupted pulmonary artery by reopening closed contralateral ductus arteriosus. Prostaglandin infusion early after birth delineated anatomical diagnosis of unilateral absence of pulmonary artery due to bilateral ductus, and it also made it possible to perform single stage uni-focalization.>.

Prevalence of Short Stature and Growth Hormone Deficiency and Factors Associated With Short Stature After Fontan Surgery

Background: Fontan circulation is characterized by many features commonly observed in heart failure that may affect physical growth regardless of pituitary gland dysfunction status. The aims of the present study were to investigate the prevalence of short stature and growth hormone deficiency (GHD) and determine the factors associated with short stature after Fontan surgery.

Methods and Results: On retrospective evaluation of 47 patients after Fontan surgery, a very high prevalence of short stature was observed (38.3%). In the short stature group, 5 patients were diagnosed with GHD (10.6% of patients after Fontan Surgery), which is much higher than the frequency of 1/10,000 in the general population. Central venous pressure (CVP) was significantly higher (14.6±4.5 vs. 12.2±1.9 mmHg, P<0.05) and the blood pressure and arterial oxygen saturation were significantly lower in the short stature group. Laboratory data also indicated volume retention and congestion in the short stature group. Mean change in stature from catheterization 1 year after Fontan surgery to the most recent visit was significantly lower in the short stature group (−1.1±1.1 SD vs. 0.0±0.8 SD, P<0.05) and significantly negatively correlated with CVP (r=−0.42, P<0.05).

Conclusions: Volume retention and congestion, the prominent features of Fontan circulation, affect physical growth partly due to pituitary gland dysfunction, highlighting the need for the screening for and treatment of this condition after Fontan surgery.

Optimal timing of video-assisted thoracoscopic surgery for patent ductus arteriosus in preterm infants born at ≤ 28 weeks of gestation

BACKGROUND

Video-assisted thoracoscopic surgery for patent ductus arteriosus (VATS-PDA) is an alternative surgical procedure to open chest surgery, even in premature infants. This study investigated whether the timing of VATS-PDA has a prognostic impact in premature infants whose operative indication was determined according to the symptomatic PDA and the ineffectiveness of or contraindication to indomethacine therapy.

METHODS

We studied 49 infants born at or before 28 weeks of gestation who were admitted to the neonatal intensive care unit between January 2004 and June 2016, and who underwent VATS-PDA. The patients were divided into two groups according to median age at the time of surgery (early group, 24 infants who underwent surgery at ≤ 24 days of life; late group, 25 infants who underwent surgery at ≥ 25 days of life).

RESULTS

No significant differences were found in bodyweight at 30 days of age and 40 weeks of corrected gestational age between the groups. The timing of surgery did not affect the operative procedure or postoperative complications. In addition, no differences were observed between the early and late groups in terms of complications associated with prematurity, including intraventricular hemorrhage, incidence and severity of bronchopulmonary dysplasia, and necrotizing enteropathy.

CONCLUSION

Video-assisted thoracoscopic surgery for patent ductus arteriosus can be safely performed in premature infants without a preferential timing for the intervention, suggesting that this procedure allows for an elective basis approach after heart failure management with conservative and/or drug therapy in premature infants with PDA.

Thyroid Function in Patients With a Fontan Circulation

In this study, we tested our hypothesis that thyroid function is impaired and contributes to perturbed hemodynamics in patients after Fontan operation. Cardiac catheterization and blood tests for thyroid function were performed in 37 patients who underwent a Fontan operation. Among them, 12 patients (33%) had subclinical thyroid dysfunction with an elevated thyroid-stimulating hormone level despite normal thyroxine levels. Thyroid-stimulating hormone levels were significantly correlated with central venous pressure (p <0.01, R² = 0.3), and patients with subclinical hypothyroidism showed significantly elevated γ-glutamyltransferase level, an indicator of liver congestion, compared with the other patients (125.6 ± 12.2 vs 67.6 ± 4.6 IU/L, p <0.01). In addition, the levels of free triiodothyronine, an effective thyroid hormone, were significantly lower in patients with subclinical hypothyroidism than in those with normal thyroid function (3.1 ± 0.1 vs 3.5 ± 0.1 pg/dl, p <0.01). The free triiodothyronine level was significantly and negatively correlated with the relaxation time constant (p = 0.03) and brain natriuretic hormone (p <0.01) level and positively correlated with the cardiac index (p = 0.04). In conclusion, venous congestion in Fontan patients may cause thyroid dysfunction, which can be responsible for decreased ventricular function and cardiac output in Fontan patients. Thus, thyroid function should be routinely monitored after Fontan surgery.

Fenestration in the Fontan circulation as a strategy for chronic cardioprotection

Background

Fenestration in the Fontan circulation potentially liberates patients from factors leading to cardiovascular remodelling, through stable haemodynamics with attenuated venous congestion. We hypothesised that a fenestrated Fontan procedure would possess chronic haemodynamic advantages beyond the preload preservation.

Methods

We enrolled 35 patients with fenestrated Fontan with a constructed pressure–volume relationship under dobutamine (DOB) infusion and/or transient fenestration occlusion (TFO). Despite the use of antiplatelets and anticoagulants, natural closure of fenestration was confirmed in 11 patients. Cardiovascular properties in patients with patent fenestration (P-F) were compared with those in patients with naturally closed fenestration (NC-F). To further delineate the roles of fenestration, paired analysis in patients with P-F was performed under DOB or rapid atrial pacing with/without TFO.

Results

As compared with P-F, patients with NC-F had a higher heart rate (HR), smaller ventricular end-diastolic area, better ejection fraction and higher central venous pressure, with higher pulmonary resistance. While this was similarly observed after DOB infusion, DOB markedly augmented diastolic and systolic ventricular stiffness in patients with NC-F compared with patients with P-F. As a mirror image of the relationship between patients with P-F and NC-F, TFO markedly reduced preload, suppressed cardiac output, and augmented afterload and diastolic stiffness. Importantly, rapid atrial pacing compromised these haemodynamic advantages of fenestration.

Conclusions

As compared with patients with NC-F, patients with P-F had robust haemodynamics with secured preload reserve, reduced afterload and a suppressed beta-adrenergic response, along with a lower HR at baseline, although these advantages had been overshadowed, or worsened, by an increased HR.

Modified underlying cardiac disease severity in twin-twin transfusion syndrome

Twin-twin transfusion syndrome or related conditions affect fetal loading. We report monochorionic-diamniotic twins. Twin 1 had Ebstein anomaly with mild tricuspid regurgitation (TR) and slightly thickened tricuspid valve leaflets with plastering. Twin 2 had tricuspid valve dysplasia (with abnormal thickening but without plastering) with moderate TR and mild right atrial dilatation. After birth, the severity of TR was greatly reduced in the recipient but increased in the donor. Therefore, intravascular volume change which was due to twin-twin transfusion syndrome seemed to affect the severity of the valvar disease in fetuses. This case suggests that the intrinsic severity of fetal tricuspid valvular disease may be overestimated in the recipient and underestimated in the donor twin. These factors need to be taken into consideration in clinical decision-making.

Single-Beat Estimation of Right Ventricular Contractility and Its Coupling to Pulmonary Arterial Load in Patients With Pulmonary Hypertension

Background

An accurate assessment of intrinsic right ventricular (RV) contractility and its relation to pulmonary arterial load is essential for the management of pulmonary hypertension. The pressure‐volume relationship with load manipulation is the gold standard assessment used for this purpose, but its clinical application has been hindered by the lack of a single‐beat method that is valid for the human RV. In the present study, we sought to validate a novel single‐beat method to estimate the preload recruitable stroke work (PRSW) and its derivative for ventriculoarterial coupling in the human RV.

Methods and Results

A novel single‐beat slope of the PRSW relationship (M_sw) was derived by calculating the mean ejection pressure when the end‐systolic volume was equal to volume‐axis intercept of the PRSW relationship. In addition, by using a mathematical transformation of the equation representing the linearity of the PRSW relationship, a novel index for ventriculoarterial coupling, M_sw/mean ejection pressure, was developed. RV pressure‐volume relationships were measured in 31 patients (including 23 patients with pulmonary hypertension) who were referred for right‐sided heart catheterization. In this cohort, the single‐beat M_sw was strongly correlated with the multiple‐beat M_sw (r=0.91, P<0.0001). Moreover, a significant correlation was observed between the single‐ and multiple‐beat M_sw/mean ejection pressure (r=0.53, P=0.002), with a stronger correlation in those with greater RV systolic pressure (r=0.70, P=0.003).

Conclusions

The novel single‐beat approach provided an accurate estimation of indexes for the PRSW relationship and ventriculoarterial coupling. It may be particularly useful in assessing RV adaptation to increased pressure overload.

Cardiac Ventricular Contractile Responses to Chronically Increased Afterload Secondary to Right Ventricular Outflow Obstruction in Patients With Tetralogy of Fallot

We examined the adaptive mechanism of the pulmonary ventricle (PV) in response to increased afterload secondary to pulmonary stenosis in tetralogy of Fallot (TOF, n = 47) and congenitally corrected transposition of the great arteries (cCTGA, n = 18), where the PV is morphologically different. We also elucidated the effects of such adaptation on systemic ventricular (SV) function. PV contractility, assessed by dp/dt_max, showed significant positive correlations with PV pressure (r = 0.82, p <0.01 for TOF and r = 0.78, p <0.01 for cCTGA) and pulmonary-to-systemic ventricular pressure ratio (r = 0.70, p <0.01 for TOF and r = 0.76, p <0.01 for cCTGA) in patients with both TOF and cCTGA. Notably, the slopes of these correlations were significantly higher in cCTGA than in TOF (p <0.01), suggesting enhanced contractile responses in cCTGA. Moreover, SV dp/dt_max showed significant positive correlations with PV dp/dt_max in patients with both TOF and cCTGA (r = 0.67, p <0.01 and r = 0.61, p <0.01, respectively), indicating positive ventricular-ventricular interaction. In this relationship, the slopes of correlations were significantly higher in TOF than in cCTGA (p = 0.024). These results, indicating different behaviors of PV contractile physiology and its interaction with the SV, may have important therapeutic implications when considering medical, catheter, and surgical interventions for pulmonary stenosis in these diseases. The results may also offer the potential for a new approach for improvement of prognosis, especially in cCTGA.

M-mode Diagnosis of Tachyarrhythmia Can be Erroneous Owing to "Pseudo 1:1 Atrioventricular Movement" of the Atrial Wall Adjacent to the Atrioventricular Valve Possibly due to Atrioventricular Constraint: A Case of Neonatal Atrial Flutter With 2:1 Atrioventricular Conduction

M-mode echocardiography has been playing an important role in the diagnosis of fetal tachyarrhythmia. We recently encountered a neonatal case of atrial flutter with 2:1 atrioventricular conduction. However, M-mode erroneously indicated 1:1 atrioventricular movement. While the movement of the atrial wall far from the atrioventricular valve was much faster than that of the ventricular wall, the atrial wall adjacent to the atrioventricular valve fully synchronized to that of the ventricular wall. Thus, to avoid this novel pitfall, it would be important to add an additional assessment focusing on the movement of the atrial wall far from the ventricle.

Developmental Changes in Aortic Mechanical Properties in Normal Fetuses and Fetuses with Cardiovascular Disease

BACKGROUND

We hypothesized that fetal aortic mechanical properties assessed by aortic diameter (AoD) and flow show maturational changes during the gestational period, and that these properties are different in fetuses with congenital heart diseases and fetuses with normal development.

METHODS

Phasic changes in ascending AoD along with Doppler flow profile were measured in 84 consecutive normal fetuses (gestational age, 18-36 weeks) and in 30 consecutive fetuses with cardiovascular diseases (gestational age, 22-39 weeks).

RESULTS

AoD and cardiac output significantly increased with gestational age. Fetal aortic compliance (AC), assessed as (maximum AoD - minimum AoD)/stroke volume, significantly decreased with gestational age in normal fetuses, indicating maturational changes in aortic wall properties. Importantly, fetuses with Marfan syndrome and tetralogy of Fallot that exhibit "aortopathy" showed significantly lower AC than normal fetuses of the same gestational age, suggesting intrinsic abnormalities in aortic wall properties in these diseases. Fetuses with trisomy 18 and Noonan syndrome also had AC values below the normal ranges.

CONCLUSION

Measurements of phasic changes in fetal AoD and flow measurements can provide useful information about aortic mechanical properties and may help clarify abnormal arterial hemodynamics in pathologic conditions.

Significance of right atrial tension for the development of complications in patients after atriopulmonary connection Fontan procedure: potential indicator for Fontan conversion

Elevated right atrial (RA) pressure and progressive RA dilation are thought to play pivotal roles in the development of late complications after atriopulmonary connection (APC) Fontan surgery. However, no clear cut-off value for RA pressure or RA volume has been determined for stratifying the risk of developing Fontan complications. We hypothesized that RA tension, which incorporates information about both RA pressure and volume, might help predict the risk of developing complications. We retrospectively studied 51 consecutive APC Fontan patients (median postoperative period 14 years). RA tension was computed from the RA pressure and RA radius, which was calculated from RA volume measured by RA angiography. The correlation between the cardiac catheterization hemodynamic data and the complications of APC Fontan was investigated. Of the 51 patients, 28 had complications, including liver fibrosis (n = 28), arrhythmia (n = 8), protein-losing enteropathy (n = 1), and RA thrombosis (n = 1). Among the hemodynamic data, RA volume and RA tension, but not RA pressure, were significantly higher in patients with complications than in those without (P = 0.004 and P = 0.001, respectively). The cut-off level for RA tension to predict Fontan complications was 26,131 dyne/cm by receiver operating characteristic curve (area under the curve 0.79, sensitivity 71.4%, and specificity 73.9%). The present study demonstrated the significance of RA tension rather than high venous pressure for the development of Fontan complications. Amid the uncertainty about clinical outcomes, the present results, subject to further validation, may contribute to the indications for Fontan conversion.

Assessment of central venous physiology of Fontan circulation using peripheral venous pressure

OBJECTIVE

Elevated central venous pressure is a major cause of morbidity and mortality after the Fontan operation. The difference between mean circulatory filling pressure and central venous pressure, a driving force of venous return, is important in determining dynamic changes in central venous pressure in response to changes in ventricular properties or loading conditions. Thus, noninvasive central venous pressure and mean circulatory filling pressure estimation may contribute to optimal management in patients undergoing the Fontan operation. We tested the hypothesis that central venous pressure and mean circulatory filling pressure in those undergoing the Fontan operation can be simply estimated using peripheral venous pressure and arm equilibrium pressure, respectively.

METHODS

This study included 30 patients after the Fontan operation who underwent cardiac catheterization (median 8.6, 3.4-42 years). Peripheral venous pressure was measured at the peripheral vein in the upper extremities. Mean circulatory filling pressure was calculated by the changes of arterial pressure and central venous pressure during the Valsalva maneuver. Arm equilibrium pressure was measured as equilibrated venous pressure by rapidly inflating a blood pressure cuff to 200 mm Hg.

RESULTS

Central venous pressure and peripheral venous pressure were highly correlated (central venous pressure = 1.6 + 0.68 × peripheral venous pressure, R = 0.86, P < .0001). Stepwise multivariable regression analysis showed that only peripheral venous pressure was a significant determinant of central venous pressure. Central venous pressure was accurately estimated using regression after volume loading by contrast injection (R = 0.82, P < .0001). In addition, arm equilibrium pressure measurements were highly reproducible and robustly reflected invasively measured mean circulatory filling pressure (mean circulatory filling pressure = 9.1 + 0.63 × arm equilibrium pressure, R = 0.88, P < .0001).

CONCLUSIONS

Central venous pressure and mean circulatory filling pressure can be noninvasively estimated by peripheral venous pressure and arm equilibrium pressure, respectively. This should help clarify unidentified Fontan pathophysiology and the mechanisms of Fontan failure progression, thereby helping construct effective tailor-made approaches to prevent Fontan failure.

Novel, single-beat approach for determining both end-systolic pressure-dimension relationship and preload recruitable stroke work

Objective

The end-systolic pressure–dimension relationship (ESPDR) and the preload recruitable stroke work (PRSW) relationship are load-insensitive measures of contractility, but their clinical application has been limited by the need to record multiple beats over a wide volume range. In this study, we therefore sought to validate a new method to concomitantly determine the ESPDR and the PRSW relationship from a single beat.

Methods

Pressure–dimension loops were recorded in 14 conscious dogs under various haemodynamic and pathological conditions. Multiple-beat PRSW relationship was determined for its slope (M_w) and for a dimension-axis intercept (D_w). The ESPDR represented by the formula , was estimated from a steady-state, single-beat late-systolic pressure–dimension relationship. The single-beat M_w was determined as an end-systolic pressure when the end-systolic dimension was equal to D_w.

Results

A strong correlation was observed between multiple-beat and single-beat ESPDRs (zero-stress dimension; r=0.98, p<0.0001). The single-beat estimation of M_w calculated using the wall thickness was strongly correlated with the actual M_w (r=0.93, p<0.0001) and was sensitive enough to detect the change in contractility by dobutamine infusion (p<0.001) and by tachycardia-induced heart failure (p<0.001). Similar results were obtained for M_w estimated without information on wall thickness.

Conclusions

M_w can be interpreted as an end-systolic pressure when the end-systolic dimension is equal to D_w. By using the non-linear ESPDR, accurate single-beat estimation of the ESPDR and M_w is possible even without information on wall thickness. These results should enhance the applicability of pressure–volume framework to clinical medicine.

Mechanism of aortic root dilation and cardiovascular function in tetralogy of Fallot

The aortic root dilation in tetralogy of Fallot (TOF) is a long-term clinical problem, because a severely dilated aorta can lead to aortic regurgitation, dissection, or rupture, which can be fatal, necessitating surgical intervention. The details of the mechanism of aortic root dilation, however, are unclear. We have shown that aortic stiffness is increased in patients with repaired TOF, and may mirror the histological abnormality of elastic fiber disruption and matrix expansion. This aortic stiffness is related closely to the aortic dilation, indicating that aortic stiffness may be a predictor of outcome of aortic dilation. Furthermore, the aortic volume overload is a very important determinant of aortic diameter in TOF patients before corrective surgery. In addition, a chromosomal abnormality and the transforming growth factor-β signaling pathway, a major contributor to aortic dilation in Marfan syndrome, also affect this mechanism. In this way, aortic dilation in TOF patients is suggested to be a multifactorial disorder. The aim of this review was therefore to clarify the mechanism of aortic dilation in TOF, focusing on recent research findings. Studies linking histopathology, mechanical properties, molecular/cellular physiology, and clinical manifestations of aortic dilation facilitate appropriate treatment intervention and improvement of long-term prognosis of TOF.

Novel mechanisms for cerebral blood flow regulation in patients with congenital heart disease

BACKGROUND

The mechanisms that regulate cerebral flow in patients after surgery for congenital heart diseases (CHDs) remain poorly understood. We tested our hypothesis that postoperative patients with CHD have disease- or hemodynamic-specific compensatory mechanisms for maintaining cerebral perfusion.

METHODS

A total of 89 children with specific hemodynamics including Glenn (n = 14), Fontan (n = 19), repaired tetralogy of Fallot (n = 24), and control patients (n = 32) were enrolled. The resistance and blood flow distribution between the brain (Rc and CIc) and lower body (Rs and CIs) were calculated by measuring the hemodynamic changes resulting from inferior vena cava occlusion during cardiac catheterization.

RESULTS

Despite considerable differences in cardiac index and superior vena cava pressure (SVCp), cerebral blood flow was preserved in all noncontrol groups, with a ratio between the vascular resistances in the cerebral and lower body circulation (Rc/Rs) that was significantly lower than that in controls. Interestingly, the reduced Rc/Rs of Glenn patients was mediated by the reduced Rc, whereas augmented Rs was conducive to the reduced Rc/Rs in the Fontan and tetralogy of Fallot groups. Multivariate analysis revealed that high SVCp was significantly associated with low Rc. Although low cardiac index was significantly associated with increased Rc and Rs, its impact was much greater on Rs than on Rc.

CONCLUSIONS

Compensatory mechanisms for cerebral flow regulation occur according to hemodynamic abnormality type in postoperative patients with CHD. Because such a regulation mechanism implies cerebral circulation fragility, further investigations are needed to address the impacts of cerebral circulation properties on neurodevelopmental outcomes.

Clinical Evaluation of the Hemodynamic Effects of the High-Flow Nasal Cannula Therapy on the Fontan Circulation

High-flow nasal cannula (HFNC) therapy supports respiratory effort with a minimal elevation in airway pressure. We examined hemodynamic effects of HFNC therapy in a 10-year-old girl with Fontan circulation, in which positive airway pressure has deleterious hemodynamic effects. The HFNC therapy at 30 L/min improved oxygenation without an increase in central venous pressure. It also reduced heart rate, and systemic and pulmonary vascular resistance, and increased cardiac output. In addition, the HFNC therapy improved the cerebral circulation measured by near-infrared spectroscopy. Thus, HFNC therapy may be a potentially useful noninvasive ventilation modality, particularly for patients with Fontan circulation.

Influence of Cardiac Function and Loading Conditions on the Myocardial Performance Index - Theoretical Analysis Based on a Mathematical Model

BACKGROUND

The myocardial performance index (MPI) has emerged as a Doppler-derived index for global ventricular function capable of estimating combined systolic and diastolic performance. While several studies have reported its load-dependency, responses of the MPI to various hemodynamic changes have not been fully characterized.

METHODS AND RESULTS

The response characteristics of the MPI were examined and compared with ejection fractions (EF) by changing hemodynamic parameters within the physiological range in a lumped parameter model of the cardiovascular system. At baseline, the MPI was 0.42 and the EF was 0.68. Heart rate increase resulted in a decrease in EF and an increase in the MPI. Reduction in end-systolic elastance decreased EF and increased the MPI. Volume overload and ventricular stiffening did not affect EF but paradoxically reduced the MPI. Increased afterload due to higher systemic resistance resulted in a decrease in EF and increase in the MPI, but afterload increase caused by reduced arterial compliance led to a decrease in both EF and MPI. These MPI characteristics caused paradoxical improvement of the MPI during disease progression of chronic heart failure in a simulation of mitral regurgitation.

CONCLUSIONS

The MPI is affected by a wider variety of hemodynamic parameters than EF. In addition, it is predicted to decrease paradoxically with volume overload, reduction in arterial compliance, or ventricular diastolic stiffening. These MPI characteristics should be considered when assessing cardiovascular dynamics using this index.

Cardiac biomarkers in children with congenital heart disease

BACKGROUND

Most congenital heart diseases (CHDs) have specific hemodynamics, including volume and pressure overload, as well as cyanosis and pulmonary hypertension, associated with anatomical abnormalities. Such hemodynamic abnormalities can cause activation of neurohormones, inflammatory cytokines, fibroblasts, and vascular endothelial cells, which in turn contribute to the development of pathologic conditions such as cardiac hypertrophy, fibrosis, and cardiac cell damages and death. Measuring biomarker levels facilitates the prediction of these pathological changes, and provides information about the stress placed on the myocardial cells, the severity of the damage, the responses of neurohumoral factors, and the remodeling of the ventricle. Compared to the ample information on cardiac biomarkers in adult heart diseases, data from children with CHD are still limited.

DATA SOURCES

We reviewed cardiac biomarkers-specifically focusing on troponin as a biomarker of myocardial damage, amino-terminal procollagen type III peptide (PIIIP) as a biomarker of myocardial fibrosis and stromal remodeling, and B-type natriuretic peptide (BNP)/N-terminal proBNP as biomarkers of cardiac load and heart failure, by introducing relevant publications, including our own, on pediatric CHD patients as well as adults.

RESULTS

Levels of highly sensitive troponin I are elevated in patients with atrial septal defects (ASDs) and ventricular septal defects (VSDs). PIIIP levels are also elevated in patients with ASD, VSD, pulmonary stenosis, and Tetralogy of Fallot. Measurement of BNP and N-terminal proBNP levels shows good correlation with heart failure score in children.

CONCLUSIONS

In the treatment of children with CHD requiring delicate care, it is vital to know the specific degree of myocardial damage and severity of heart failure. Cardiac biomarkers are useful tools for ascertaining the condition of CHDs with ease and are likely to be useful in determining the appropriate care of pediatric cardiology patients.

Prevalence, implication, and determinants of worsening renal function after surgery for congenital heart disease

Accumulating data in adults indicate the prognostic importance of worsening renal function (WRF) during treatment of acute heart failure. Venous congestion appears to play a dominant role in WRF; however, data regarding WRF in children with congenital heart disease (CHD) are limited. The present study was conducted to elucidate the prevalence and characteristics of WRF after surgery for CHD in children. We also tested our hypothesis that, similar to adult heart failure, venous congestion is an important determinant of WRF independent of cardiac output in this population. Fifty-five consecutive pediatric patients who underwent cardiovascular surgery for CHD were studied (median age 0.7 years; range 3 days to 17 years). The degree of WRF was assessed by the difference between the maximum levels of postoperative serum creatinine (Cr) and preoperative serum Cr. There was a high prevalence of WRF in the present cohort: an increase in Cr level was observed in 47 patients (85 %) and a Cr increase ≥0.3 mg/dL was seen in 23 (42 %). Importantly, WRF was significantly associated with a worse clinical outcome of a longer stay in the intensive care unit and hospital (both p < 0.05), even after controlling for age and operative factors. In addition, multivariate regression analysis revealed that central venous pressure, rather than cardiac output, was an independent determinant of WRF. Postoperative management to relieve venous congestion may help ameliorate or prevent WRF and thereby improve outcomes in patients with CHD.

Influence of Left Ventricular Stiffness on Hemodynamics in Patients With Untreated Atrial Septal Defects

BACKGROUND

Although left ventricular (LV) stiffening with age is believed to increase left-to-right shunting in patients with atrial septal defects (ASD), clinical data have not confirmed this. We sought determinants of the pulmonary-to-systemic flow ratio (Qp/Qs) in patients with untreated ASD.

METHODS AND RESULTS

We retrospectively studied 180 patients with ASD who underwent percutaneous ASD closure between 2007 and 2011. Qp/Qs and LV stiffness were measured before ASD closure.The median age of the subjects was 18 years, and 117 (65.0%) were female. The mean ASD size adjusted for square root of body surface area (BSA) was 14.4±4.2 mm/m, and the Qp/Qs was 2.28±0.74. Adjusted ASD size most strongly related to Qp/Qs (r=0.74, P<0.0001). Multivariate analysis revealed that LV stiffness was a significant predictor of Qp/Qs, independently of adjusted ASD size and vascular resistance (P=0.0015). Based on the multivariate model that accounts for the effects of LV stiffness and vascular resistance, the minimal adjusted diameter that can cause a Qp/Qs of 2.0 was predicted to be 7.3 mm/m.

CONCLUSIONS

Qp/Qs in ASD can change significantly depending on LV stiffness, suggesting that it would increase with age. An ASD >7.3 mm/m in diameter has the potential to cause significant left-to-right shunting, and may require closure regardless of hemodynamic status at the time of assessment.

Cystatin C and body surface area are major determinants of the ratio of N-terminal pro-brain natriuretic peptide to brain natriuretic peptide levels in children

BACKGROUND

Production of N-terminal pro-brain natriuretic peptide (NT) and BNP is equimolar. Although NT clearance occurs only in the kidneys, BNP clearance occurs in the kidneys and other organs. This study tested the hypothesis that NT/BNP ratio in children may be independently related to cystatin C (CysC), a glomerular filtration rate marker, when diastolic function and age/body size are taken into consideration.

METHODS

The study included 430 children (5.3±4.9 years) with heart disease who had undergone cardiac catheterization and simultaneous BNP, NT, and CysC measurements. Pulmonary capillary wedge pressure (PCWP) was used as a ventricular diastolic stretch marker. Variables showing skewed distribution were transformed into a common logarithm.

RESULTS

Univariate regression revealed that logNT/BNP was affected by PCWP (r=-0.12) and logCysC (r=0.57). When age and the log of body surface area (BSA) were added to the stepwise regression, age was not adopted because of multicollinearity to logBSA, but PCWP (β=-0.10), logCysC (β=0.22), and logBSA (β=-0.66) were independent factors of logNT/BNP.

CONCLUSIONS

Renal dysfunction independently increased NT/BNP, whereas high BSA decreased it and is the greatest determinant of NT/BNP. The observation that high PCWP decreased NT/BNP may suggest that worsening heart failure slows BNP clearance from other organs, a compensatory pathway of heart failure. These factors need to be considered when assessing BNP and NT.

Hemodynamic performance of the Fontan circulation compared with a normal biventricular circulation: a computational model study

The physiological limitations of the Fontan circulation have been extensively addressed in the literature. Many studies emphasized the importance of pulmonary vascular resistance in determining cardiac output (CO) but gave little attention to other cardiovascular properties that may play considerable roles as well. The present study was aimed to systemically investigate the effects of various cardiovascular properties on clinically relevant hemodynamic variables (e.g., CO and central venous pressure). To this aim, a computational modeling method was employed. The constructed models provided a useful tool for quantifying the hemodynamic effects of any cardiovascular property of interest by varying the corresponding model parameters in model-based simulations. Herein, the Fontan circulation was studied compared with a normal biventricular circulation so as to highlight the unique characteristics of the Fontan circulation. Based on a series of numerical experiments, it was found that 1) pulmonary vascular resistance, ventricular diastolic function, and systemic vascular compliance play a major role, while heart rate, ventricular contractility, and systemic vascular resistance play a secondary role in the regulation of CO in the Fontan circulation; 2) CO is nonlinearly related to any single cardiovascular property, with their relationship being simultaneously influenced by other cardiovascular properties; and 3) the stability of central venous pressure is significantly reduced in the Fontan circulation. The findings suggest that the hemodynamic performance of the Fontan circulation is codetermined by various cardiovascular properties and hence a full understanding of patient-specific cardiovascular conditions is necessary to optimize the treatment of Fontan patients.

Pulmonary arterial wall stiffness and its impact on right ventricular afterload in patients with repaired tetralogy of Fallot

BACKGROUND

Recent histologic studies involving patients with tetralogy of Fallot (TOF) have revealed a reduction in normal elastic fibers in the pulmonary trunk. Such histologic changes may significantly alter the mechanical properties of the arterial wall and may thereby augment the pulsatile afterload on the right ventricle (RV) and propagate RV dilation and dysfunction.

METHODS

We studied 29 patients with repaired TOF (median age, 5.9 years) and 29 age-matched controls. Pulmonary arterial hemodynamics were investigated by measuring the pulmonary input impedance during cardiac catheterization.

RESULTS

Patients with TOF had higher characteristic impedance (p = 0.0002), lower total pulmonary vascular compliance (p < 0.0001), and enhanced wave reflection (p < 0.0001). Consistent with these changes, patients with TOF were subject to higher pulsatile load, measured by fundamental frequency impedance (p < 0.0001), which was significantly related to both reduced RV output and increased RV end-diastolic volume (p = 0.006 and 0.003, respectively). Moreover, pulmonary arterial compliance was strongly related to RV end-diastolic volume (r = -0.69, p = 0.0001). In multivariate analysis, pulmonary arterial compliance was a significant predictor of RV dilation independent of pulmonary regurgitation and pulmonary stenosis (p = 0.03).

CONCLUSIONS

In line with known histologic changes, pulmonary arterial stiffness is increased and is significantly related to reduced RV ejection and RV enlargement in patients with repaired TOF. These results suggest that not only pulmonary valvular function (pulmonary regurgitation/pulmonary stenosis) but also pulmonary vascular pulsatile properties can be an important therapeutic target to improve prognosis in this population.

Constrictive pericarditis developed after childhood repair of ventricular septal defect

The patient was an 18-year-old man who had undergone surgical closure of ventricular septal defect at the age of 2 years. The patient was urgently hospitalized due to syncope after longstanding uneventful postoperative course, and diagnosed with atrial flutter. Echocardiography showed poor ventricular motion and markedly dilated both atriums. After termination of atrial flutter, ventricular motion improved remarkably; however, there was little improvement in heart failure. Although we suspected constrictive pericarditis, calcification observed on computed tomography was too localized to fully explain the cause of severe diastolic dysfunction. Based on the waveform of mitral annular tissue Doppler imaging, we were strongly convinced of the underlying physiology of constrictive pericarditis. Pericardial decortications markedly improved heart failure symptoms. This case emphasizes that constrictive pericarditis could be a life-threatening complication in the remote phase after congenital heart surgery. It also emphasizes the importance of functional assessment by echocardiography to identify the cause-effect relation between imaging and clinical symptoms.

Landiolol hydrochloride infusion for treatment of junctional ectopic tachycardia in post-operative paediatric patients with congenital heart defect

AIMS

Junctional ectopic tachycardia (JET) after cardiopulmonary bypass surgery for congenital heart defects is often therapy-resistant and associated with high morbidity and mortality. Improvement of pharmacological therapy is needed.

METHODS AND RESULTS

We retrospectively analysed the clinical data of four patients with congenital heart defects, who developed post-operative JET and were treated with landiolol hydrochloride, representing all such patients treated at our university. In two patients, landiolol was used after failure of response to anti-arrhythmic therapies, including thermal control, sedation, discontinuation of catecholamines, and pharmacological therapy with nifekalant and amiodarone. Landiolol was used as a first-line therapy in the other two patients. In all patients, landiolol, at a dose ranging from 1.0 to 10.0 µg/kg/min, achieved successful sinus conversion within 15 min. No adverse events, such as bradycardia, hypotension, or hypoglycaemia, were encountered in all four patients.

CONCLUSION

Although limited to a small and heterogeneous group of patients, the results suggest that landiolol is a potentially useful therapeutic option for the well-known difficult condition of post-operative JET, and warrant further investigation in large-scale controlled studies.

Usefulness of cystatin C in the postoperative management of pediatric patients with congenital heart disease

BACKGROUND

The characteristics of the renal marker cystatin C (Cys-C) in association with the postoperative management of children with congenital heart disease (CHD) remain unclear.

METHODS AND RESULTS

Serum Cys-C and creatinine (Cr) levels were measured preoperatively and on the third postoperative day in 53 consecutive CHD patients (age, 1 day-11 years). On the third postoperative day, the patients were divided into 2 groups: the clinically severe group, requiring continuous infusion of diuretic drugs or peritoneal dialysis; and the non-severe group, composed of those without such needs. Preoperative Cys-C level decreased with age (by month) during the first year of life and remained almost constant thereafter, while Cr level increased with age. The Cys-C ratio (Cys-C level on the third postoperative day/preoperative level) was positively correlated with Cr ratio (R=0.57, P<0.001). Both Cys-C and Cr levels increased in correlation with the clinical severity of renal impairment. Receiver operating characteristic curve analysis failed to demonstrate an advantage of Cys-C over Cr in detecting severity.

CONCLUSIONS

Cys-C may be a useful marker of renal function in terms of hemodynamic status in the postoperative management of CHD, although its superiority over Cr could not be confirmed. Future studies should clarify the role of Cys-C in clinical decision-making and evaluate the relationship of Cys-C with factors that may affect its levels.

Stenosis of a reconstructed aorta caused a paradoxical diastolic pressure gradient after norwood operation

An infant with hypoplastic left heart syndrome showed paroxysmal episodes of bradycardia, hypotension, and hypoxemia upon crying after modified Norwood operation. Echocardiography showed decreased right ventricular ejection with grade III tricuspid regurgitation, a markedly enlarged aortic arch, and accelerated blood flow distal to the enlarged aorta. Aortography demonstrated an aneurysmal neo-aorta with an apple-shaped appearance. The pressure measurements revealed intriguing aortic hemodynamics: the diastolic pressure of the ascending aorta was lower than that of the descending aorta (42 mmHg vs. 52 mmHg) despite no systolic pressure gradient. Markedly reduced compliance in the ascending aorta relative to that in the descending aorta, which was suggested by the difference in time constant of aortic pressure decay, may explain this hemodynamics. Impaired coronary circulation caused by lowered diastolic pressure in ascending aorta was indicated by reduced subendocardial viability ratio, and may account for her symptom and lowered ventricular ejection. The patient’s condition was indeed significantly improved by surgical correction of the aortic shape. This case highlights the importance of aortic shape and properties after Norwood operation.