Pulmonary Flow Ratio Research Articles

Flow visualization of a unique case of persistent truncus arteriosus with prolonged survival

A 50-year-old woman was admitted to the coronary care unit due to recurrent chest distress for 30 years. She successfully gave birth to a healthy boy at the age of 24. Physical examination showed a pan systolic multifocal murmur, severe acropachia, and cyanosis (Panel A). Her oxygen saturation was 76% at room air. Both transthoracic echocardiography and computed tomographic angiography suggested a truncus arteriosus (Panels B and C). Cardiovascular magnetic resonance illustrated a large, persistent truncus arteriosus (PTA) arising from the base of the heart, overriding a non-restrictive outlet ventricular septal defect. A single left pulmonary artery originated from the basal of the trunk, where the right pulmonary artery was missing (Panel D). Cardiovascular magnetic resonance 4D flow, a non-contrast, blood flow quantifiable technique, was performed. Streamline flow visualization demonstrated a balanced aortic and pulmonary flow ratio (Panel D; see Supplementary data online, Movie S1), which might be the underlying reason for her unique long survival.

No evidence of pulmonary hypertension revealed in an echographic evaluation of right-sided hemodynamics in hyperthyroid cats.

Hyperthyroidism is a common endocrinopathy affecting middle-aged to elderly cats, with multisystemic repercussions. Hyperthyroid humans show decreased lung compliance and increased cardiac output with subsequent left heart failure leading to pulmonary capillary congestion. Prognosis worsens with the development of increased pulmonary vascular pressures (ie, pulmonary hypertension [PH]) in hyperthyroid humans. The effect of excess thyroid hormone concentration on pulmonary arterial hemodynamics is unknown in cats. Assessing pulmonary vascular pressures in veterinary medicine relies heavily on echocardiographic measurements performed at the level of the heart and pulmonary trunk. This study investigated right-sided cardiac and pulmonary arterial hemodynamics in hyperthyroid cats using echocardiography. Echocardiographic examinations of hyperthyroid cats identified through a bi-institutional database search were reviewed for the determination of systolic pulmonary arterial pressure (PAP) and 20 other metrics. Values were compared with those of a healthy cat group using non-parametric statistical analyses. Systolic PAP could not be determined in 23/26 hyperthyroid and 13/14 healthy cats owing to unmeasurable tricuspid regurgitation flow velocity. Hyperthyroid cats were roughly twice as old (P <0.001) and had 2-4-fold higher respiratory rates (P <0.001) than healthy cats. Hyperthyroid cats showed an increase in acceleration time-to-ejection time ratio of pulmonary flow (1.4-fold, P = 0.001), pulmonary artery velocity time integral (1.2-1.6-fold, P = 0.001), maximal pulmonary velocity (1.3-1.7-fold, P = 0.002), stroke volume (1.5-fold, P = 0.001) and cardiac output (1.6-fold, P <0.001) vs healthy cats. None of the other echocardiographic metrics reached statistical significance. Systolic PAP estimation proved unsuitable as a sole measurement for the assessment of PH in hyperthyroid cats owing to the frequent inability to interrogate tricuspid regurgitant flow velocity. Hyperthyroid cats have altered echocardiographic measures of pulmonary hemodynamics dissimilar to those reported in hyperthyroid humans. Differential effects of thyrotoxic cardiomyopathy on ventricular systolic function may underlie species differences.

Abstract 14301: Investigation of an Injection-Jet Self-Powered Fontan Circulation

Introduction: The Fontan circulation is a fragile system in which imperfections at any one of multiple levels may compromise quality of life. Increased inferior vena caval (IVC) pressure itself may play some role in “Fontan failure”. The Fontan circulation is powered with a high speed injection jet shunt (IJS) drawing flow from the aortic arch, balanced by a fenestration to preserve the ratio of pulmonary flow (Qp) to systemic flow (Qs). The high-velocity jet causes flow entrainment, leading to a significant reduction of upstream pressure. We describe a tightly coupled multi-scale lumped parameter/computational fluids dynamics (LPM-CFD) model to validate this hypothesis. Methods: A synthetic 3D CAD model of the fenestrated total cavopulmonary connection (TCPC) was generated, with average dimensions matching those of a 2-4 yo patient. The prescribed cardiac output is of about 2.3L/min. The detailed 3D pulsatile hemodynamics in the fluid domain are modeled as unsteady, turbulent and incompressible. Blood is assumed to be non-Newtonian. Turbulence is approximated using a large eddy simulation (LES) approach. Potential optimal IJS configurations were determined by with a parametric sweep of several geometric design parameters such as TCPC morphology, shunt diameter and location, and fenestration diameter and location. The effects of the IJS implementation on IVC pressure with a fenestration and systemic oxygen saturation were calculated using a tightly coupled LPM-CFD. Results and Discussion: A set of baseline simulations representing a failing Fontan, with elevated IVC pressure (+17.8mmHg). Enlargement of the fenestration to 7 mm results in a 3 mm Hg IVC pressure drop but also significant reduction in systemic oxygen saturation (assuming a 96% pulmonary venous O2 saturation level). Addition of an IJS (2mm nozzle) to this model preserves the IVC pressure drop of 3.2mmHg but improves systemic oxygen saturation with only a small additional volume load to the ventricle (CO/Qs = 1.2). Conclusions: This study demonstrates the potential salutary effect of the IJS on the Fontan circulation. Further exploration of adjustable anatomic and parameters are needed to further reduce IVC pressure and improve systemic saturation.

Early outcome and risk factors analysis of Blalock-Taussig shunt

Objective To investigate the early curative effect of Blalock-Taussig(B-T) shunt and summarize the key point in its post-operative intensive care, analyze the related risk factor of its mortality. Methods We collected 71 patients who received B-T shunt in Shanghai Children′s Medical Center from June 2015 to June 2017.All of 71 cases were divided into neonates group (25 cases) and non-neonate group(46 cases). All patients were operated through median sternotomy, 19 were emergency cases, in which 15 cases were neonates.Eight cases used cardio-pulmonary bypass in our study, in which 4 cases were neonates.Twenty-nine cases received ductus ligation in total 34 patients with patent ductus arterious.Percutaneous heparin was immediately administered after operation as an anticoagulation therapy.Relative large dosage inotropic agents was used after sufficient volume infusion in order to guarantee diastolic pressure higher than 35 mmHg(in neonates >30 mmHg, 1 mmHg=0.133 kPa). Ventilator parameter was adjusted to obtain appropriate flow distribution between pulmonary and systemic circulation.In order to avoid excessive pulmonary flow, the target PO2 was set between 40~45 mmHg. Results Oxygen saturation elevated by 15% after operation in all 71 cases.Average mechanical ventilation time was 92 hours, mean inotropic agents score was 17.There were 6 dead cases, mortality was 8.5%.In neonates, 4 cases dead, mortality was 16.0%.There was no significant difference in ventilation time, ICU retention day and mortality between neonates group and non-neonates group.The logistic regression analysis showed that the body weight and ratio between the shunt conduit diameter and body weight (mm/kg) were the risk factors for early post-operative mortality[body weight: 2 500~3 500 g: OR=6.729, 95%CI=1.373~17.131; ≤2 500 g: OR=7.832, 95%CI=2.563~28.325.the ratio between the shunt conduit diameter and body weight (mm/kg): 1.10~1.15: OR=4.204, 95%CI=1.195~23.926; ≥1.15: OR=3.981, 95%CI=1.195~12.926]. Conclusion B-T shunt is still a high risk operation although it is a palliative method.Low body weight and bigger diameter conduit are the significant factors related to its mortality.Strict control of the systemic and pulmonary flow ratio is the key point in the post-operation intensive care. Key words: Blaclock-Taussig shunts; Neonates; Palliative operation; Congenial heart disease

Cardiac Physiology for Radiologists: Review of Relevant Physiology for Interpretation of Cardiac MR Imaging and CT.

Cardiac computed tomography (CT) and magnetic resonance (MR) imaging provide clinicians with important insights into cardiac physiology and pathology. However, not all radiologists understand the language and concepts of cardiac physiology that are used daily by cardiologists. This review article covers basic cardiac physiology as it relates to cardiac CT and MR imaging. Topics include a review of the cardiac cycle and left ventricular pressure-volume loops as they relate to different pathologic states, evaluation of cardiac function, and calculation of key parameters such as left ventricular volumes and the ejection fraction. The hemodynamics of cardiac shunts are covered, with an emphasis on factors important to cardiologists, including the ratio of pulmonary flow to systemic flow. Additionally, valvular physiologic function is reexamined, with a focus on understanding pressure gradients within the heart and also the changes associated with valvular pathologic conditions, including measurement of regurgitant fractions in patients with valvular insufficiency. Understanding these basic concepts will help radiologists tailor the reporting of cardiac studies to clinically relevant information.

Model-Based Comparison of the Normal and Fontan Circulatory Systems—Part II

In the absence of an accessible chronic animal model of the Fontan circulation, computational modeling can provide insights into this unique circulatory arrangement, especially how differently it behaves from the normal mammalian circulation. Many groups have focused on refining a single element of the entire Fontan circulation-the total cavopulmonary connection (TCPC). Yet, only modest improvements in transplant-free survival have resulted. From an engineering perspective, optimizing the performance of a complex, multiparameter system requires an understanding of how the performance is affected by the full set of system parameters. We evaluated the hemodynamic impact of nine physiological perturbations in the two-year-old (yo) patient with hypoplastic left heart syndrome having a Fontan rearrangement (using our previously described lumped-parameter multicompartment model of both pulmonary and systemic circulations). In cases where comparison is appropriate, we evaluated the hemodynamic impact of analogous pathophysiologies in the normal two-year-olds. We operated the model in open-loop mode in order to expose the magnitude of the impact of uncompensated physiological perturbations. Without the benefit of compensatory mechanisms, a valvar regurgitant fraction of 50% is sufficient to drop the cardiac index (CI) to 2.0 L/min/m(2) or less. Aortopulmonary collateral flow of 0.6 L/min (1.1 L/min/m(2)) or 0.5 L/min (0.9 L/min/m(2)), sufficient to raise the ratio of pulmonary flow to systemic flow (Qp/Qs) to no higher than 1.2 or 1.5 (fenestration present or absent, respectively), is the maximum which could be tolerated (CI = 2.0 L/min/m(2)) without the help of compensatory mechanisms. Ventricular end-diastolic elastance (stiffness) changes have dramatic effects on CI in a Fontan circulatory arrangement. Several components of the Fontan circulation other than the TCPC actually have equal, or greater, impact on CI under certain conditions.

Normal values of right pulmonary to left pulmonary flow ratio in healthy individuals determined by cardiovascular magnetic resonance

In congenital heart disease (CHD) pulmonary flow ratio (PFR) is frequently impaired which is associated with a negative outcome [1]. Classically, lung perfusion scintigraphy has been used for determination of the PFR [2,3]. Phase-velocity cardiac magnetic resonance (PV-MR) for pulmonary flow measurements avoids ionizing radiation; however, studies on PFR in healthy individuals are sparse [2,4–7].

Comparative Outcome of Bidirectional Glenn Shunt in Patients With Pulmonary Vascular Resistance ≥ 3.5 Woods Units Versus < 3.5 Woods Units

Moderate to severe pulmonary hypertension is considered to be an absolute contraindication to the performance of bidirectional Glenn (BDG) shunting. However, BDG shunting has been performed in young children with pulmonary hypertension associated with unrestricted pulmonary blood flow. In this study, the medical records of patients who underwent BDG starting from October 2000 to March 2004 were reviewed. Patients were divided into 2 groups on the basis of indexed pulmonary vascular resistance (PVRI) measured in room air: a high-risk group (n = 12) with PVRI > or = 3.5 Woods units (WU)/m(2) and a low-risk group (n = 28) with PVRI <3.5 WU/m(2) in room air. The 2 groups were comparable with respect to age, weight, ventricular morphology, pulmonary arterial anatomy, and atrioventricular valve function. Mean pulmonary arterial pressure and PVRI were significantly higher in the high-risk group compared with the low-risk group (39.2 +/- 20.7 vs 15.1 +/- 6.25 mm Hg, p <0.002, and 6.0 +/- 2.5 vs 1.6 +/- 0.82 WU/m(2), p <0.0005, respectively). The ratio of pulmonary flow to systemic flow was 1.45 +/- 0.76 in the high-risk group and 1.24 +/- 1.2 in the low-risk group. In the high-risk group, mean PVRI decreased to 2.0 +/- 1.0 WU/m(2) on 100% oxygen (p <0.0005). A contraindication to Glenn shunting was PVRI >3.5 WU/m(2) on 100% oxygen. Hospital mortality was 17% (2 of 12) in the high-risk group and 4% (1 of 28) in the low-risk group. Of 10 survivors in the high-risk group, 1 had undergone a Kawashima procedure, 7 had undergone Fontan procedures (with 1 death), and 2 were awaiting the completion of Fontan procedures as of this writing. In conclusion, these preliminary data suggest that in young children with increased pulmonary flow, BDG shunting can be safely performed, despite the apparent elevation of pulmonary arterial pressure to inoperable levels, provided PVRI decreases to < or = 3.5 WU/m(2) on 100% oxygen.

Doppler sonography determination of flow ratios Qp/Qs and resistance ratios Rp/Rs in isolated ventricular septal defect

We present a model based on an electric analogon that describes the haemodynamic situation of an isolated ventricular septal defect. The model shows a way to estimate the ratio of pulmonary to systemic vascular resistance by Doppler sonographic measurements of pulmonary to systemic flow ratio (Qp/Qs) and the ratio between the size of the defect and the cross-sectional area of the aorta (Av/Aa). The ratio of pulmonary to systemic vascular resistance is theoretically given by: Rp/Rs = Qs/Qp + log (Av/Aa) * (1-Qs/Qp). Systemic to pulmonary flow ratio can be measured by Doppler echocardiography as well as Av/Aa; therefore, Rp/Rs can be estimated noninvasively by the equation given above. The values estimated noninvasively by Doppler echocardiography showed a good correlation with the haemodynamic data obtained at cardiac catheterisation.

Cardiovascular Shunts: MR Imaging Evaluation

Magnetic resonance (MR) imaging has become an important tool for the accurate and noninvasive assessment of congenital heart disease. Because more precise delineation of anatomy and evaluation of function can be obtained with MR imaging than with either echocardiography or angiography, MR imaging is frequently used to evaluate cardiovascular shunt lesions. It is essential that imaging specialists be able to recognize the MR imaging features of various kinds of shunts, including supracristal ventricular septal defect, atrioventricular septal defect, and partial anomalous pulmonary venous connection. MR imaging is particularly useful for evaluating shunt severity, which can be expressed quantitatively as the ratio of pulmonary flow to systemic flow. This ratio can be estimated accurately with the use of either volumetric cine MR imaging or velocity-encoded cine MR imaging.

Computational fluid dynamic simulations of cavopulmonary connections with an extracardiac lateral conduit

Complex congenital heart defects due to the absence of a ventricular chamber can often be treated by the Fontan surgical procedure. The objective of this work was to quantify the haemodynamics in the Fontan operation (cavopulmonary connection) with extracardiac lateral conduit. Four different models based on the finite element method were constructed with different lengths of inferior anastomosis (range 18–25 mm) and inclinations of the conduit (33 and 47.5°). Mass conservation and Navier–Stokes equations were solved by means of the FIDAP code, based on the finite element method. The left-to-right pulmonary flow ratio and percentage inferior caval blood to the left lung were the highest with the smallest anastomosis and highest inclination: 1.35 and 83.26%, respectively. Dissipated power percentage was higher with the largest anastomosis than with the smallest (19.4 vs 15.8%). It was concluded that, when performing a total cavopulmonary connection, an extracardiac lateral conduit: (i) diverts more flow to the left lung, and (ii) shows higher energy losses when compared with a connection with intra-atrial tunnel. This study could be useful to evaluate the incidence of pulmonary arteriovenous malformations.

In vitro flow experiments for determination of optimal geometry of total cavopulmonary connection for surgical repair of children with functional single ventricle

This study sought to evaluate the effect of offsetting cavopulmonary connections at varying pulmonary flow ratios to determine the optimal geometry of the connection. Previous investigators have demonstrated energy conservation within the streamlined contours of the total cavopulmonary connection compared with that of the atriopulmonary connection. However, their surgical design of connecting the two cavae directly opposite each other may result in high energy losses. Others have introduced a unidirectional connection with some advantages but with concerns about the formation of arteriovenous malformation in the lung excluded from hepatic venous return. Thus, an optimal surgical design has not been determined. In the present models, the caval connections were offset through a range of 0.0 to 2.0 diameters by 0.5 superior cava diameter increments. Flow ratios were fixed for superior and inferior cavae and varied for right and left pulmonary arteries as 70:30, 60:40, 50:50, 40:60 and 30:70 to stimulate varying lung resistance. Pressure measurements and flow visualization were done at steady flows of 2, 4 and 6 liters/min to stimulate rest and exercise. Our data show that the energy losses at the 0.0-diameter offset were double the losses of the 1.0 and 1.5 diameters, which had minimal energy losses. This result was attributable to chaotic patterns seen on flow visualization in the 0.0-diameters offset. Energy savings were more evident at the 50:50 right/left pulmonary artery ratio. Energy losses increased with increased total flow rates. The results strongly suggest the incorporation of caval offsets in future total cavopulmonary connections.

Long-term hemodynamic effects of nifedipine on congenital heart disease with Eisenmenger's mechanism in children.

The hemodynamic effect of long-term nifedipine medication was studied in 10 children, 3-12 years of age, five with ventricular septal defect and five with complete atrioventricular septal defect; all had Eisenmenger's reaction, seven also had Down's syndrome. They underwent heart catheterization prior to and during 1-4 years of nifedipine therapy. Fick's principle was used to calculate the ratio of pulmonary arterial pressure to aortic pressure (PAP/PAO), the ratio of pulmonary flow to aortic flow (QP/QS), as well as the ratio of pulmonary vascular resistance to aortic vascular resistance (RP/RS). In the seven children under 8.8 years, nifedipine caused a significant drop in PAP/PAO (p less than 0.004), a slight increase in arterial O2 saturation, a significant increase in QP/QS (p less than 0.02), and a decrease in RP/RS (p less than 0.02). The nifedipine effect was age related. On nifedipine, breathing oxygen resulted in, independent of age, a significant increase in QP/QS (p less than 0.003) and a significant decrease in PAP/PAO (p less than 0.04) and in RP/RS (p less than 0.003). Direct O2 consumption measurements before and during oxygen breathing in six patients demonstrated no significant change in RP, RS, QP, or QS indices. Nifedipine had a relaxing effect on the pulmonary vascular bed, especially in the younger child with Eisenmenger's mechanism. On nifedipine therapy, O2 produced a more complex hemodynamic reaction that was not restricted to the pulmonary circulation alone.

A Measurement of Pulmonary Flow, Systemic Flow and the Ratio of Pulmonary Flow and Systemic Flow by 2D-Doppler Echocardiography in Ventricular Septal Defect -A Comparison Study with the Fick's Method by Cardiac Catheterization-

A Measurement of Pulmonary Flow, Systemic Flow and the Ratio of Pulmonary Flow and Systemic Flow by 2D-Doppler Echocardiography in Ventricular Septal Defect -A Comparison Study with the Fick's Method by Cardiac Catheterization-

Hemodynamic determinants of risk in pulmonary artery banding

<h2>Summary</h2> A classification of left to right shunts is presented based on pulmonary to systemic flow and resistance ratios as well as right ventricular and left ventricular systolic pressure ratios. The results of banding are poor when the ratio of pulmonary flow to systemic flow (Q_P/Q_S) is less than 2.0. Banding may be detrimental when right ventricular systolic pressure is low. Patients at the lowest risk for banding are those with high right ventricular pressures and large shunts.

Left-to-right shunt in atrial septal defect at rest and during exercise.

Abstract. The pulmonary and systemic flow has been calculated at rest and during exercise in 16 patients with atrial septal defects. In 14 of these patients there was a normal pulmonary arterial pressure at rest. Remarkably many of the patients showed only a slight increase in the systemic flow during exercise. The pulmonary flow increased during exercise in most of the patients. The absolute left‐to‐right shunt fell in 5 patients, was unchanged in 1 and moderately increased in 10 patients. No correlation was found between the magnitude of the shunt and the variation in the pulmonary blood flow during exercise. The pulmonary flow ratio decreased in all patients except 3 during exercise.

The effect of exercise on the size of the shunt in patients with atrial septal defects.

Abstract The pulmonary and systemic flow was measured at rest and during exercise in 13 patients with atrial septal defects, of whom 12 had a normal pulmonary arterial pressure. The pulmonary flow ratio decreased in all the patients and the decrease was clearly dependent upon the value at rest. The pulmonary blood flow increased during exercise. This increase was greatest in the patients with a small blood flow in the pulmonary artery and smallest in those with the largest pulmonary blood flow at rest. The shunt decreased correspondingly inasmuch as the systemic blood flow was normal both at rest and during exercise. All the changes tend to produce a normalization of the haemodynamic conditions during exercise in patients with uncomplicated atrial septal defects and explain why the working capacity of these patients is independent of the magnitude of the shunt at rest.

外科的心疾患にともなう肺動脈圧亢進に関する研究

In cardiac surgery, the degree of pulmonary hypertension is an important feature to determine the severity of the diseases, and the functional and pathological abnormalities of the small pulmonary vessels are the important factors to influence the hemodynamics, operative indications and prognosis. While many authors have reported about the correlation between the pathological findings of small pulmonary vessels and hemodynamics, some authors recognized recently that the vasoconstriction of pulmonary vessels causes, maintains and in some instances aggravates the pulmonary hypertension with or without the pathological changes of pulmonary vessels.The author studied on the pulmonary hypertension in special reference to its reversibility in standpoint of pulmonary vasoconstriction from both functional and anatomical aspects of small pulmonary vessels.Seven cases of V.S.D., three cases of A.S.D., three cases of P.D.A. and eleven cases of M.S. were studied. After the routine right heart catheterization was performed at rest, 1 mg/kg of Hexamethonium bromide (C6) was administered through the catheter, the tip of which remained slightly distal to pulmonary bifurcation, and the pulmonary hemodynamic changes were observed after 15 minutes. At operation, the lung biopsies were obtained immediately after thoractomy, and microscopic preparations were all stained with Verhoeff's elastic tissue stains counterstained with Van Gieson's connective tissue stains. Histological studies were confined to small muscular arteries and arterioles, and the lumen : wall ratios (L/W) were measured separately by eyepiece micrometer and their ratios were averaged. The immediate or remote postoperative pulmonary hemodynamic changes were studied about three cases of V.S.D., three cases of A.S.D., one case of P.D.A. and four cases of M.S. The pulmonary hemodynamic data were expressed by % ratios to systemic ones.The results obtained are as follows.1) The higher the initial levels, the more profound the % fall of the ratios of pulmonary to systemic systolic pressure and resistance after the administration of Hexamethonium. In those cases where the pulmonary vessels were well responsive to the administration of Hexamethonium, and so the marked fall of the ratios of pulmonary to systemic systolic pressure and resistance and increase of pulmonary flow ratio or shunt flow ratio were obtained, the medial muscular hypertrophies of small pulmonary vessels, especially of pulmonary arterioles were the most characteristic findings. This fact suggests that the medial muscular hypertrophy is the anatomical expression of pulmonary vasoconstriction which is thought to maintain the pulmonary hypertension.2) In non-responsive cases where the fall of the ratios of pulmonary to systemic systolic pressure and resistance and the increase of pulmonary flow ratio were not obtained, the medial muscular tissues of small pulmonary vessels were very scanty and in addition, the intimal proliferations were present in various degrees. In this group, therefore, pulmonary vasoconstrictive factor is thought not to operate.3) In responsive group, there is an intimate correlation between the ratios of pulmonary to systemic systolic pressure after the administration of Hexamethonium and those after the closure of shunt or mitral commissurotomy.4) Thus, it seems to be possible to anticipate in some degree the reversibility of pulmonary hypertension preoperatively from the pulmonary hemodynamic changes before and after the administration of Hexamethonium.