Systemic venous and pulmonary arterial flow patterns after Fontan's procedure for tricuspid atresia or single ventricle

The Fontan Procedure for Single-Ventricle Physiology

The Fontan procedure is the final procedure in staged palliation for patients with functional single-ventricle physiology. The goal of the procedure is to separate systemic and pulmonary blood flow by directing systemic venous return through the Fontan connection to the pulmonary arteries and the lungs without ventricular contribution. Following the procedure, pulmonary blood flow is completely passive and dependent on pressure gradients, resulting in complex postoperative cardiopulmonary interactions. Understanding the physiology is essential to effectively manage these patients. Critical care nurses caring for patients after a Fontan procedure must understand preoperative data, risk factors, and unique postoperative physiology so they can anticipate specific postoperative problems, recognize trends in clinical status, and develop an appropriate plan of care. This paper reviews the first 2 stages of single-ventricle palliation, relevant modifications to the Fontan procedure, important preoperative cardiac catheterization data, common postoperative problems, and outcomes after the Fontan procedure.

Contributions of Respiration and Heartbeat to the Pulmonary Blood Flow in the Fontan Circulation

BACKGROUND

In the Fontan circulation, driving forces with respiration, heartbeat, and lower limb muscle pump are relevant. However, the mechanics of these forces has not been proven, and their effects on the Fontan circulation remain unclear.

METHODS

We performed catheter examinations and measured pressure and flow velocity simultaneously in the bilateral pulmonary arteries of 12 Fontan patients 1 year after the operation. The pulmonary pressure and flow velocity data were decomposed into respiratory and heartbeat components by discrete Fourier analysis. We then calculated respiratory and cardiac wave intensity (WI) based on the respiratory and heartbeat components of pressure and flow velocity data.

RESULTS

Respiratory WI formed 2 negative peaks, a backward expansion wave during the inspiratory phase, and then a backward compression wave during the expiratory phase. In 2 phrenic nerve palsy cases and 1 case of a patient on a respirator, respiratory WI showed disturbed patterns and a negative pattern, respectively. Cardiac WI showed 2 or 4 negative peaks, the time phase of which matched that of the atrial contractions.

CONCLUSIONS

WI analysis elucidated that inspiration acts as a sucking driving force and increases the pulmonary blood flow in the Fontan circulation. Respiratory complications compromise efficiency in the Fontan circulation. It was also revealed that the pulmonary blood flow was mutually dammed up and sucked in by increases and decreases in atrial pressure.

Pulmonary and caval blood flow patterns in patients with intracardiac and extracardiac Fontan: a magnetic resonance study

AIMS

We compared in vivo blood flow and pulsatility after different types of Fontan operation using magnetic resonance imaging.

MATERIAL AND METHODS

A total of 37 consecutive patients (mean age 19+/-7.9 years, 7.3+/-3.2 years after Fontan operation), 7 with atriopulmonary anastomosis (APC), 18 with intra-atrial lateral tunnel (LTFO) and 12 with extracardiac Fontan (ECFO) were studied using magnetic resonance phase-contrast velocity mapping. Blood flow (volume flow) in the superior vena cava (SVC), inferior vena cava (IVC) and both pulmonary arteries were measured and a pulsatility index was calculated for each vessel.

RESULTS

For all modifications, the blood flow distribution between the SVC and IVC was normal (1:2). Patients with APC had a normal pulsatility, a dilated right atrium, partial backward flow in the IVC and physiological blood flow distribution between the pulmonary arteries. LTFO and ECFO patients had no retrograde flow in the IVC, equal blood flow distribution between the pulmonary arteries and very low or absent pulsatility.

CONCLUSIONS

MRI allows hemodynamic quantification and characterization of various types of Fontan modifications and may be a valuable tool to predict Fontan failure. Despite showing normal pulsatility, patients with APC have right atrial dilatation and partial backward flow in the IVC, demonstrating suboptimal Fontan circulation. LTFO and ECFO both produce unidirectional antegrade flow in the IVC but pulsatility is very low or absent, which may promote poor pulmonary artery growth and increase of pulmonary vascular resistance contributing to late Fontan failure.

Emergency cesarean section in a patient with Fontan circulation using an indwelling epidural catheter

Management of parturients with a history of Fontan procedure requires careful monitoring of cardiovascular parameters and anticipation of potential complications. We describe potential pitfalls in a parturient with atriopulmonary Fontan circulation, who received epidural analgesia for labor and who later required emergency cesarean section. Low-dose local anesthetic in combination with meperidine provided excellent perioperative epidural analgesia and cardiovascular stability. Epidural analgesia during labor offered optimal pain relief and facilitated conversion to surgical anesthesia for an emergency cesarean section.

Effect of unilateral diaphragm paralysis on branch pulmonary artery flow

BACKGROUND

Respiration is known to be a significant contributor to pulmonary flow in patients who have had Glenn or Fontan procedures.

OBJECTIVE

The purpose of this study was to evaluate the effect of respiration on branch pulmonary artery flow in normal participants, in those with uncomplicated Glenn or Fontan procedures, and in those with uncomplicated biventricular (2V) repairs, and to compare them with similar groups of postoperative patients who had unilateral diaphragm paralysis.

METHODS

Twenty-one normal infants and children were studied, along with 10 who had undergone uncomplicated bidirectional Glenn or Fontan palliation. Also studied were 10 patients with uncomplicated 2V repairs and 17 patients having ultrasound demonstration of diaphragm paralysis. Nine had undergone Glenn or Fontan procedures and 8 had undergone 2V repair. With the use of conventional pulsed Doppler, branch right and left pulmonary artery waveforms were recorded during spontaneous respiration. The velocity time integral (VTI); heart rate (HR); and systolic, diastolic, and mean velocities were measured at end-expiration and during inspiration. The pulsatility index (PI) (PI = systolic velocity - diastolic velocity/mean velocity) was calculated for each condition.

RESULTS

In normal participants PI was 1.69 with a 4.7% increase with inspiration; VTI x HR was 1859. In patients who had undergone uncomplicated Glenn/Fontan procedures PI was 1.06 with a 27.5% increase with inspiration; VTI x HR was 1303, all P =.001 versus normal participants. In patients with 2V repairs PI was 1.7 with a 5.6% increase with inspiration; VTI x HR was 1850, all P = ns versus normal participants. Patients with Glenn/Fontan connections and diaphragm paralysis had lower PI (0.81), inspiratory increase (7.9%), and VTI x HR (610) on the affected side, all P =.001 versus the normal side, and versus patients who had undergone uncomplicated Glenn/Fontan procedures. Patients with 2V repair with a pulsatile source of pulmonary flow had a smaller significant difference in the measured indices. Three patients underwent diaphragm plication with improvement in PI, inspiratory increase in PI, and VTI x HR postplication.

CONCLUSION

In normal participants and patients with uncomplicated 2V repair, inspiration has little effect on PI in branch pulmonary arteries. In patients who have undergone uncomplicated Glenn/Fontan procedures, PI is less than that of normal participants and the effect of inspiration is approximately 5-fold greater. This significant effect of inspiration on pulmonary flow is lost on the affected side in patients with Glenn/Fontan connections and diaphragm paralysis, and is blunted on the affected side in patients with 2V repair and diaphragm paralysis. Loss of diaphragm function is associated with redistribution of pulmonary flow away from the affected side.

Intraoperative evaluation of pulmonary artery flow during the Fontan procedure by transesophageal Doppler echocardiography

After the Fontan procedure, pulmonary artery (PA) flow is maintained without right ventricular pump function. We evaluated intraoperative PA flow velocity patterns using transesophageal Doppler echocardiography (TEE) immediately after cardiopulmonary bypass (CPB) in patients during Fontan or hemi-Fontan procedures. We studied 10 patients with single-ventricle physiology (age range, 5 mo to 3 yr 1 mo). Anesthesia was induced and maintained with fentanyl. After induction of anesthesia, a pediatric TEE probe was inserted into the esophagus. All patients had surgical repair involving direct anastomosis of the right atrium to the PA. Immediately after completion of CPB, adequacy of the atriopulmonary anastomosis was assessed and PA flow velocity was recorded. In all patients, the atriopulmonary anastomosis was clearly defined using a single-plane TEE probe, and PA flow recording was completed successfully. Intraoperative PA flow velocities showed two distinct patterns. Biphasic forward flows with peak velocities during systole and diastole were observed in six patients. The remaining four patients showed forward flows with flow reversals. The four patients demonstrating flow reversals showed significantly reduced fractional shortening (26.5+/-2.1% vs. 35.5+/-6.3%) and larger pressure gradient between the right atrium and left atrium (10.8+/-1.3 mm Hg vs 8.0+/-0.9 mm Hg) when compared to those without reverse flow. Two patients with reverse flow required reoperation because of hypotension. Because PA flow is influenced by pulmonary vascular resistance and left ventricular function, TEE assessed intraoperative PA flow should be further evaluated as a useful predictor of surgical outcome after a Fontan procedure.

Instantaneous pressure-flow velocity relations of systemic venous return in patients with univentricular circulation

OBJECTIVE

To assess the pressure and flow velocity relations and respiratory variability of the systemic venous and hepatic venous return in patients with univentricular circulation.

PATIENTS

15 selected patients who had undergone cavopulmonary anastomosis (10) or atriopulmonary anastomosis (5). Mean age at operation was 55.1 months (range 9 to 145). Studies were done at 75.5 (32.6) months (mean (SD)) after the operation.

SETTING

Tertiary referral centre.

METHODS

Patients were studied using simultaneous recordings of ECG, pressure trace, respirometer trace, and pulsed Doppler echocardiography. Mean systemic venous pressure and pulmonary vascular resistance did not differ significantly between the two patient groups.

RESULTS

After total cavopulmonary anastomosis, systemic venous pressure tracings showed a flattened pressure curve without any dependence on cardiac or respiratory cycle. After atriopulmonary anastomosis, right atrial pressure tracings showed a significantly higher "a" wave corresponding to atrial contraction, without any respiratory variability. Pulsed Doppler examination of the superior and inferior caval vein and hepatic vein after total cavopulmonary anastomosis did not show a reverse flow after atrial contraction. The inspiratory to expiratory velocity ratio of antegrade flow revealed a significant dependence of flow on changes in intrathoracic pressure in the intra-atrial tunnel, caval veins, and hepatic vein. During expiration, decrease or cessation of antegrade hepatic venous flow was documented. After an atriopulmonary anastomosis, there was a biphasic antegrade venous flow pattern without significant respiratory variation.

CONCLUSIONS

After total cavopulmonary anastomosis, there was marked respiratory dependence of systemic and hepatic venous return, whereas after an atriopulmonary anastomosis venous flow pattern varied according to cardiac cycle and pressure trace. The effects of total cavopulmonary anastomosis on venous return might counteract its other haemodynamic advantages.

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 degrees). 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.

Cardiac MR imaging in congenital heart disease

Magnetic resonance imaging is a unique and insightful tool for the assessment of structure and function in congenital heart disease. For anatomic assessment, the large field of view, lack of limitation by patient size, and ability to create three-dimensional surface displays from routine imaging acquisitions offer several advantages over other modalities. The ability of magnetic resonance imaging to assess the volume and mass of bizarre ventricular shapes accurately and myocardial tissue and blood tagging as well as phase encoded velocity mapping has enhanced research in pediatric cardiology. Newer techniques, such as oxygen-sensitive magnetic resonance imaging and echo-planar magnetic resonance imaging, promise even further advances in research and in clinical applications.

Pulsed Doppler echocardiographic assessment of patterns of venous flow after the modified Fontan operation: potential clinical implications

To assess the effect of a modified Fontan operation on systemic venous blood flow and the hepatic circulation, we compared 11 patients having an atriopulmonary connection and 35 with total cavopulmonary anastomosis. The Doppler echocardiographic study of the caval venous, hepatic venous and portal venous flow was performed so as to calculate the pulsatility ratio and the variation of flow with respiration. All patients had undergone cardiac catheterization. In addition, we included specific laboratory investigations to assess function of various organs. Significantly lower maximum velocities of flow at inspiration (0.31+/-0.12 m/sec vs 0.45+/-0.14 m/sec) and expiration (0.23+/-0.09 m/sec vs 0.32+/-0.11 m/sec), less pulsatility (0.43 vs 0.16) and a lower ratio of systolic to diastolic velocity (1.22 vs 1.85) were found in the patients having a cavopulmonary as compared to an atriopulmonary anastomosis. Peak velocities of hepatic venous flow during inspiration and expiration were significantly lower in those with a cavopulmonary anastomosis (p = 0.001 and p < 0.001, respectively). In these patients, forward flow was extremely dependent on respiration, with decrease or cessation of antegrade flow during expiration in 22 patients. The velocity of portal venous flow was also significantly lower in these patients, although the pulsatility ratio did not differ significantly between the groups (0.5+/-0.21 and 0.57+/-0.23, respectively). The ratio of inspiratory and expiratory velocities showed no significant difference between the groups, nor was there any correlation between the pulsatility ratio of the venous vessels or the ratio of peak flow velocities during expiration and the mean systemic venous/right atrial pressure on postoperative cardiac catheterization. Hypoproteinemia was found in 8 patients after total cavopulmonary anastomosis; 9 of 10 patients with protein C deficiency belonged to this group. The dependence of hepatic venous flow on respiration in the presence of a chronically elevated systemic venous pressure in patients after the total cavopulmonary anastomosis may influence hepatic function in the postoperative period.

The nature of flow in the systemic venous pathway measured by magnetic resonance blood tagging in patients having the Fontan operation

OBJECTIVES

Our objectives were twofold: (1) to determine cardiac and respiratory dependency of systemic venous pathway flow of patients having the Fontan operation with a total cavopulmonary connection and (2) to describe the velocity profile. Systemic venous pathway flow is hypothesized to be mostly respiratory dependent, to be laminar, and to have a smooth velocity profile.

METHODS

Twenty-two patients having the Fontan operation (aged 8.6 +/- 4.7 years) underwent magnetic resonance blood tagging (bolus tagging). Systemic venous pathway spin-echo images parallel to the blood flow were used as a localizer. A saturation pulse labeled the blood, and a cine image was acquired at the inferior and superior venae cavae and midportion of the baffle in the systemic venous pathway, triggered to the electrocardiogram and gated to both end-expiration and end-inspiration. Repetition time was 50 msec.

RESULTS

Flow in the systemic venous pathway was laminar throughout its course and was found to be phasic to both cardiac and respiratory cycles. Approximately 70% of flow was cardiac dependent, and the rest was respiratory. Highest flow occurred near end-systole and early diastole and in inspiration. Lowest flow occurred in diastasis. Velocity was highest and flow least "pluglike" in the mid-baffle area during cardiac or respiratory imaging (45 +/- 17 and 32 +/- 11 cm/sec, respectively).

CONCLUSION

A substantial amount of pulmonary blood flow in patients who have undergone a total cavopulmonary connection type of Fontan operation has a cardiac component. Furthermore, we confirm that this flow is laminar but nonuniform across the systemic venous pathway. Highest flows occurred near end-systole and early diastole, as well as in inspiration, and the lowest flow occurred in diastasis. This information may help in designing the systemic venous pathway and optimizing medical management.

Comparison of patterns of pulmonary venous blood flow in the functional single ventricle heart after operative aortopulmonary shunt versus superior cavopulmonary shunt

In this study we investigated the patterns of pulmonary venous flow in children with functional single ventricles to obtain a better understanding of the determinants of transpulmonary blood flow. Sixty-eight patients with functional single ventricles and aortopulmonary shunt (n = 34, group I), or superior cavopulmonary connection (n = 34, group II) underwent transesophageal Doppler echocardiographic assessment of flow in the left upper pulmonary vein before undergoing the next stage of surgery. Twelve patients from group II also underwent simultaneous evaluation of superior vena caval flow. Biphasic forward pulmonary venous flow was noted in 62 patients in sinus rhythm (S wave in systole, D wave in diastole); in 6 patients with junctional rhythm, significant early systolic reversal of flow was present. Both the S- and D-wave velocity-time integrals (VTI) were greater in group I than in group II (S(VTI) 9.9 +/- 4.2 vs 8.0 +/- 2.6, p = 0.02; D(VTI) 8.0 +/- 3.5 vs 4.2 +/- 2.6, p <0.001). In both groups, pulmonary venous flow was predominantly systolic; however, the proportion of flow during ventricular systole was significantly greater in group II than in group I (S(VTI)/D(VTI) group II: 2.4 +/- 1.5; group I 1.4 +/- 0.5, p = 0.001; percent systolic fraction of pulmonary venous flow group II = 67%, group I = 56%, p <0.001). Analysis of superior vena caval flow in group II revealed a single predominant wave with onset at early systole and peak in late systole at a mean of 150 ms after the pulmonary venous S-wave peak. Our data suggest that ventricular systole (i.e., atrial relaxation, atrioventricular valve descent) asserts great influence on transpulmonary blood flow in the functional single ventricle.

Effect of surgical reconstruction on flow profiles in the aorta using magnetic resonance blood tagging

BACKGROUND

The aorta that has undergone an aorta-pulmonary artery anastomosis may not exhibit the same velocity profile as the nonreconstructed aorta, whose velocity profile is thought to be uniform across the vessel diameter (plug flow). This may have an impact on fluid dynamics and will alter Doppler flow calculations. Our objective was to determine the impact of surgical reconstruction on the velocity and flow profiles of the reconstructed ascending and descending aorta.

METHODS

Using a magnetic resonance imaging tagging technique that labels flowing blood (bolus tagging), we studied 22 patients (mean age, 8.6 +/- 4.7 years) who had had a Fontan procedure. A cine sequence labeled the blood and acquired the image after 20 ms in the middle of the ascending aorta and behind the left atrium in the descending aorta. The repetition time was 50 ms.

RESULTS

The reconstructed ascending aorta displayed a velocity profile skewed anteriorly, whereas in the nonreconstructed aorta, the velocity profile was flat. Reconstructed aortas also displayed flows that were higher anteriorly, took a longer time to reach maximum velocity, and were less like "plug" flow than the nonreconstructed aorta. The descending aorta, regardless of whether aortic reconstruction was present, displayed velocity profiles (at various phases of systole) skewed posteriorly.

CONCLUSIONS

The reconstructed aorta displays disturbed flow, and the velocities across the ascending aortic diameter are more varied than those in aortas without reconstruction and are skewed anteriorly. The descending aortic velocity profile in children is skewed posteriorly, regardless of whether aortic reconstruction is present. This information may help design and build a "better" aortic reconstruction.

What factors affect ventricular performance after a Fontan-type operation?

Postoperative conditions after a Fontan-type operation, particularly as they affect results in the early term, are thought to depend on factors such as the state of pulmonary circulation and ventricular function. In this study, we attempted to determine the factors that influence ventricular characteristics in the middle term after Fontan-type procedures. Catheterization was performed at a mean of 15 months after operation in 57 patients with univentricular atrioventricular connection who underwent the operation between 1.0 and 22.6 years of age. End-diastolic volume, end-systolic volume, ejection fraction, and end-diastolic pressure of the systemic ventricle were analyzed together with an estimation of the systemic flow index. These parameters were influenced significantly by the presence of atrioventricular valve insufficiency. The morphologically left ventricle showed a better ejection fraction than did the morphologically right ventricle, whereas the systemic flow index was greater in patients undergoing total cavopulmonary connection than in those receiving an atriopulmonary connection. Young age was significantly associated with a better postoperative contractility, whereas the potential for impaired ventricular compliance was suggested in several patients undergoing operation after 4 years of age. On the basis of our results, we conclude that total cavopulmonary connection performed at a young age should be the surgical procedure of choice and that atrioventricular insufficiency must be treated properly at, and even after, the initial definitive repair.

The modified Fontan operation. An analysis of risk factors for early postoperative death or takedown in 702 consecutive patients from one institution

To better understand risk factors associated with early postoperative death or failure, we reviewed our entire experience with 702 consecutive patients who had the modified Fontan operation at the Mayo Clinic between October 1973 and December 1989. The event rate for takedown of repair or death during the initial hospitalization or within 30 days of the operation was 14.8% (successful takedown of the repair, n = 6; death, n = 98). To identify variables associated with early death or Fontan takedown, we analyzed 33 clinical and hemodynamic variables in a univariate and multivariate manner. On the basis of a stepwise logistic discriminant analysis, patients who were younger and operated on before 1980 with a higher preoperative pulmonary artery mean pressure, asplenia, higher intraoperative (after Fontan operation) right atrial pressure, longer aortic crossclamp time, and pulmonary artery ligation were more likely to have the outcome event of interest (p values < 0.05). A new variable, corrected pulmonary artery pressure (that is, mean preoperative pulmonary artery pressure divided by the ratio of pulmonary to systemic flow if the ratio of pulmonary to systemic flow is greater than 1.0), was significantly associated with the outcome event univariately (p = 0.002), but was no more predictive than the preoperative pulmonary artery mean pressure. Variables less predictive of the outcome event in this analysis included multiple prior operations, polysplenia syndrome, complex anatomy other than asplenia syndrome, and systemic atrioventricular valve regurgitation. These results represent the largest single-institution review of the Fontan operation and suggest that some anatomic and hemodynamic variables previously predictive of poor early outcome have been nullified by current operative methods.

Resuscitation after modified Fontan procedure

As the survival rate after modified Fontan procedure is increasing, cardiopulmonary resuscitation may be needed in such patients for other causes not related to their cardiac status. The state-of-the-art cardiopulmonary resuscitation with external chest compression may not be sufficient to revive such patients, and the addition of external abdominal compressions may help in the final outcome, as is reported here.

Postoperative pulmonary flow dynamics after Fontan surgery: assessment with nuclear magnetic resonance velocity mapping

OBJECTIVES

This study was performed to assess the value of nuclear magnetic resonance (NMR) velocity mapping for the measurement of pulmonary blood flow after Fontan surgery.

BACKGROUND

Echocardiographic studies of pulmonary flow after Fontan surgery are not always satisfactory. The newly developed technique of NMR velocity mapping may contribute to the elucidation of the Fontan circulation.

METHODS

At frequent intervals during the cardiac cycle, forward and backward flow volumes in the pulmonary arteries of nine volunteers were measured, summed and compared with right ventricular stroke volume to validate the velocity mapping technique. In 14 patients after Fontan surgery, assessment of pulmonary flow volumes enabled the evaluation of atriopulmonary and atrioventricular (AV) Fontan connections. The findings were correlated with precordial echocardiography.

RESULTS

Validation of the NMR technique, obtained from volunteer experiments, showed a high correlation (r = 0.97) between right ventricular stroke volume and volumetric pulmonary stroke flow. In all patients with an atriopulmonary Fontan connection (n = 8), forward flow in the pulmonary artery was biphasic, similar to normal venous flow. Monophasic systolic pulmonary flow curves indicating right ventricle-dependent pulmonary blood flow were found in three of six patients with an AV Fontan connection. In the remaining three patients, the pulmonary flow pattern did not reflect right ventricular contraction. Measurement of flow velocity alone may give a false impression of forward flow and thus of right ventricular contribution. Pulmonary regurgitation was demonstrated in six of eight patients with an atriopulmonary connection.

CONCLUSIONS

Nuclear magnetic resonance velocity mapping provides accurate and valuable information on pulmonary flow volume and velocity after Fontan surgery. The success of AV Fontan surgery can be deduced from the presence of a monophasic systolic pulmonary flow pattern as demonstrated by NMR velocity mapping. With NMR flow volume analysis, substantial pulmonary regurgitation occurring after atriopulmonary Fontan surgery can be measured.

Pulsed Doppler echocardiographic assessment of portal venous flow patterns in patients after the Fontan operation

OBJECTIVE

To assess the effect of the condition of the right heart after the Fontan operation on portal venous flow, and to determine whether the characteristics of portal venous flow were different when there was an atriopulmonary connection with atrial septal closure rather than an atriopulmonary or total cavopulmonary connection with intra-atrial routing.

PATIENTS AND METHODS

After the Fontan operation six patients with an atriopulmonary connection (group 1), three patients with an atriosubpulmonary connection (group 2), four patients with intra-atrial routing and an atriopulmonary connection (group 3), and five patients with a total cavopulmonary connection (group 4) were studied by pulsed Doppler echocardiography. The flow signals were recorded for the pulmonary artery, hepatic vein, and intrahepatic portal vein in each patient. Postoperative cardiac catheterisation was performed in 16 of the 18 patients. The Doppler findings were compared with those of 14 controls.

RESULTS

The portal flow was pulsatile in 13 patients and constant in five patients. Reversed flow was shown at or just after the QRS wave after hepatic venous regurgitation in two group 1 patients. The flow signal was interrupted in two group 1 patients and two group 2 patients. Decrease in velocity of flow was recorded in two group 1 patients, one group 2 patients, three group 3 patients, and one group 4 patient. Portal flow was constant in one group 3 patient and four group 4 patients. The pulsatility ratio ranged from -0.46 to 0.49 (mean (SD), 0.03 (0.32)) in the patients from group 1 and 2, from 0.41 to 0.76 (0.54 (0.15)) in group 3, and from 0.70 to 0.80 (0.75 (0.04)) in group 4. The ratio in the controls ranged from 0.29 to 0.83 (0.61 (0.13)). The ratio was significantly lower in groups 1 and 2 than in group 3 (p < 0.01), group 4 (p < 0.01), or the controls (p < 0.005). There was no significant difference in the ratio between group 3 and group 4 and no correlation between the pulsatility ratio and the cardiac index (r = 0.26), mean right atrial pressure (r = 0.25), or pulmonary vascular resistance (r = 0.17).

CONCLUSION

The larger hepatic venous regurgitation caused by atrial contraction in patients with an atriopulmonary connection correlated with the higher portal pulsatility and a total cavopulmonary connection reduced portal pulsatility.

The modified Fontan procedure: physiology and anesthetic implications

The modified Fontan operation has gained wide acceptance as a functional corrective procedure for patients with CHD with single ventricle physiology. Long-term survival and palliation of symptoms are excellent with most patients able to lead normal lives. The absence of a pulmonary contractile ventricle means that the single ventricle is responsible for perfusion of both the pulmonary and systemic circulations. Elevated systemic venous pressure is required to overcome PVR and this state of systemic venous hypertension has a significant impact on the anesthetic and postoperative care of these patients.

The utility of transesophageal echocardiography during and after Fontan operations in small children

Transesophageal echocardiography with Doppler examination was performed intraoperatively in 19 children undergoing modified Fontan operations and in 10 patients postoperatively. Comparisons were made with results of intraoperative epicardial imaging (9 patients) and with postoperative transthoracic imaging (10 patients). Transesophageal echocardiography optimally visualized atriopulmonary and cavopulmonary anastomoses. Epicardial echocardiography was successful in only three of nine patients. Intraoperative transesophageal echocardiography showed residua in 8 of 19 studies and led directly to surgical revision or medical therapy. These residua included stenosis of the cavopulmonary anastomosis (1 patient), unsatisfactory atrial fenestration (2 patients), patent ductus arteriosus (1 patient), residual cavoatrial shunting (1 patient), atrial thrombi (1 patient), and poor ventricular function (2 patients). Results of examination in the postoperative intensive care unit showed significant abnormalities in 4 of 10 patients. This study demonstrates that transesophageal echocardiography provides unique anatomic and physiologic information during and after modified Fontan operations in small children and therefore may have significant impact on patient management.

Doppler assessment of pulmonary artery flow patterns and ventricular function after the Fontan operation

To assess the relation between ventricular systolic and diastolic function and pulmonary artery (PA) flow patterns after the Fontan operation, 15 postoperative patients were prospectively evaluated with echocardiography. Blood flow velocities in the PA were recorded with pulsed Doppler echocardiography. Ejection fraction was measured by 2-dimensional echocardiography using Simpson's rule. Indexes of diastolic function were measured from the systemic atrioventricular valve inflow Doppler and included peak E and A velocities, peak filling rate normalized for stroke volume, the fractions of filling in early and late diastole (E and A area fractions), and the E/A velocity and area ratios. Compared with 15 age-matched control subjects, the 15 patients who had undergone the Fontan procedure had decreased peak E velocity (0.65 +/- 0.20 vs 0.87 +/- 0.10 m/s), decreased E/A velocity ratio (1.29 +/- 0.23 vs 1.98 +/- 0.46), decreased normalized peak filling rate (6.09 +/- 0.90 vs 6.81 +/- 0.83 s-1), decreased E area fraction (0.63 +/- 0.09 vs 0.72 +/- 0.07), increased A area fraction (0.37 +/- 0.07 vs 0.24 +/- 0.06), and decreased E/A area ratio (1.77 +/- 0.45 vs 3.33 +/- 1.15) (p less than 0.05). These diastolic filling abnormalities are consistent with impaired ventricular relaxation and decreased early diastolic transvalvular pressure gradient. PA Doppler recordings showed 2 distinct patterns of flow. Pattern I, observed in 9 patients, showed biphasic forward flow with peak velocities in mid to late systole and mid-diastole. Pattern II, observed in the remaining 6 patients, showed decreased systolic forward flow, a late systolic to early diastolic flow reversal, and delayed onset of diastolic forward flow.(ABSTRACT TRUNCATED AT 250 WORDS)

Doppler echocardiographic evaluation of pulmonary blood flow after the Fontan operation: the role of the lungs

OBJECTIVE

To document whether the act of respiration influences pulmonary blood flow in patients after the Fontan operation.

DESIGN

Prospective study in which patients acted as their own controls.

SETTING

Supraregional paediatric cardiology centre.

PATIENTS

Sixteen patients who had undergone atriopulmonary anastomosis (Fontan operation) for the treatment of congenital heart disease.

INTERVENTION

Doppler assessment of pulmonary artery flow patterns with a simultaneous respirometer, electrocardiogram and phonocardiogram.

RESULTS

Total (mean (1SD) ) forward pulmonary flow was 63.6 (35)% higher during inspiratory cardiac cycles than during expiratory ones.

CONCLUSIONS

The act of breathing provides an additional energy supply to pulmonary blood flow in patients after the Fontan operation.

The Fontan procedure: a historical review

Complete bypass of the right ventricle was first performed successfully and subsequently reported by Fontan and Baudet for patients with tricuspid atresia. By eliminating congenital and surgical shunts, ventricular volume overload and pulmonary hypertension were avoided. A logical extension of its predecessor, the partial right heart bypass procedure introduced by Glenn, the Fontan operation has great application for patients with various forms of univentricular heart. It is one of the historic advances in the surgical treatment of congenital heart disease.

Role of intraoperative ultrasound examination in patients undergoing a Fontan-type procedure

To determine its potential impact on perioperative surgical management intraoperative ultrasound examination (cross sectional imaging, colour flow mapping, pulsed and continuous wave Doppler) was used in 16 consecutive patients undergoing a Fontan-type procedure. Epicardial cross sectional imaging before bypass defined the precise intracardiac morphology in 15 of 16 patients. The preoperative morphological diagnosis was refined in four patients (25%), and this influenced surgical management in two (12%). Epicardial studies after bypass identified seven residual haemodynamic lesions in five patients (three residual intercardiac shunts, one ventricular outflow obstruction, one pulmonary artery obstruction, two mitral valve regurgitation), and led to immediate revision during a second period of bypass in three (18%). In one patient who required early reoperation residual shunting was not detected after bypass by either colour flow mapping or a contrast study. Final intraoperative studies showed a good surgical result in 14 patients (87%). Flow characteristics and flow velocities within the Fontan circulation could be assessed immediately after the patient came off cardiopulmonary bypass by means of combined pulsed wave Doppler and colour flow mapping in 14 of the 16 patients. Cross sectional studies of the left heart after bypass showed no change in ventricular function and allowed monitoring of volume replacement and ventricular filling. Intraoperative ultrasound was a valuable monitoring technique in patients undergoing a Fontan-type procedure. It refined preoperative diagnosis, monitored ventricular function, and identified or excluded residual haemodynamic lesions in most patients.

Pulmonary blood flow after total cavopulmonary shunt

The pattern of pulmonary blood flow was studied in three patients after a total cavopulmonary shunt procedure. Doppler studies showed a phasic pattern of flow which varied with the respiratory cycle. Pulmonary blood flow was increased with normal inspiration, and was much augmented by the Mueller manoeuvre. This suggests that flow was occurring when a negative intrathoracic pressure was generated. During a brief Valsalva manoeuvre blood flowed away from the lungs. With a sustained Valsalva manoeuvre there was no spontaneous forward flow; instead there was low velocity pulsatile pulmonary blood flow that coincided with ventricular systole. Left ventricular cavity dimensions decreased, reflecting a considerably reduced pulmonary blood flow. Pulmonary blood flow after the total cavopulmonary shunt operation is critically dependent on changes in intrathoracic pressure. This has important implications in terms of the immediate postoperative management of these patients.

Transesophageal echocardiography in evaluation and management after a Fontan procedure

Transesophageal echocardiography was used in 18 patients (aged 1.6 to 34 years, mean age 12.6) to assess the immediate (5 patients) or intermediate (13 patients) results after a Fontan-type procedure. The findings were correlated with precordial echocardiographic (all patients) and cardiac catheterization (11 patients) data. Atrial shunting was documented by transesophageal studies in three patients (precordial in one patient). In two patients it was confirmed by cardiac catheterization; the third underwent reoperation based on the transesophageal study alone. Pulmonary artery obstruction was documented in three patients (precordial in one patient) and was confirmed by subsequent cardiac catheterization in all. Evaluation of anterior Fontan connections was successful in 5 of 8 patients (precordial in 6 of 8), and posterior connections in 10 of 10 patients (precordial in 5 of 10). A Glenn shunt could be evaluated in eight of nine patients (precordial in three of nine). Thrombus formation was detected by transesophageal studies in three patients (precordial in one patient); repeat studies were used to evaluate thrombolytic therapy in two. Atrioventricular valvular regurgitation (11 of 18 patients) was better defined by transesophageal than by precordial studies (5 of 18). A coronary artery fistula was identified in two cases (precordial in none). Transesophageal pulsed Doppler interrogation of pulmonary artery and pulmonary vein flow patterns consistently allowed a detailed evaluation of the Fontan circulation. Transesophageal echocardiography is an important diagnostic and monitoring technique after the Fontan procedure. In this series, it was far superior to precordial ultrasound evaluation and of substantial additional value to cardiac catheterization.

Doppler echocardiographic evaluation of pulmonary artery flow after modified Fontan operation: importance of atrial contraction

Doppler echocardiography was used to evaluate blood flow in the pulmonary artery in 14 patients 2 to 42 months (mean (SD) 17 (12) months) after a modified Fontan operation incorporating a direct atriopulmonary anastomosis. Preoperatively six patients had tricuspid atresia, six had a double inlet left ventricle, and two had pulmonary atresia with an intact ventricular septum. The postoperative rhythm was sinus in 11 patients, junctional in one, ventricular pacing in one, and atrioventricular sequential pacing in one. In one patient the Doppler trace was unsatisfactory for analysis. In all patients forward flow in the pulmonary artery had biphasic peaks related to both atrial and ventricular contraction. The mean (SD) peak flow velocity that was synchronous with atrial contraction was 80 (30) cm/s and that synchronous with ventricular contraction was 74 (23) cm/s. The atrial contribution to total pulmonary artery flow, assessed by velocity-time integrals, varied between 22% and 73% (mean (SD) 45 (14)%). In patients with tricuspid atresia the mean (SD) peak flow velocity with atrial contraction was 90 (27) cm/s and that with ventricular contraction was mean (SD) 68 (24) cm/s. In patients with double inlet left ventricle the mean (SD) peak flow velocity was 67 (36) cm/s with atrial contraction and 80 (25) cm/s with ventricular contraction. The atrial contribution to total pulmonary blood flow in patients with tricuspid atresia was significantly higher (53 (11)%) than in those with double inlet left ventricle (37 (14)%). Pulmonary artery flow after modified Fontan operation was biphasic and was related to both atrial and ventricular contraction. The atrial contribution to pulmonary blood flow is greater in patients with tricuspid atresia than in those with a double inlet left ventricle. The mechanism of the second peak related to ventricular contraction is unknown.

Early diastolic clicks after the Fontan procedure for double inlet left ventricle: anatomical and physiological correlates

M mode echocardiograms and simultaneous phonocardiograms were recorded in four patients with early diastolic clicks on auscultation. All had double inlet left ventricle and had undergone the Fontan procedure with closure of the right atrioventricular valve orifice by an artificial patch. The phonocardiogram confirmed a high frequency sound occurring 60-90 ms after aortic valve closure and coinciding with the time of maximal excursion of the atrioventricular valve patch towards the ventricular mass. One patient had coexisting congenital complete heart block. The M mode echocardiogram showed "reversed" motion of the patch towards the right atrium during atrial contraction. Doppler flow studies showed that coincident with this motion there was forward flow in the pulmonary artery with augmentation when atrial contraction coincided with ventricular systole. The early diastolic click in these patients was explained by abrupt cessation of the motion of the atrioventricular valve patch towards the ventricular mass in early diastole. In one patient atrial contraction led to a reversal of this motion and was associated with forward flow in the pulmonary artery.

Assessment of the intrapulmonary ventilation-perfusion distribution after the Fontan procedure for complex cardiac anomalies: relation to pulmonary hemodynamics

In 12 patients who underwent the Fontan procedure for complex cardiac anomalies, lung scanning with xenon-133 was performed to assess the intrapulmonary ventilation-perfusion distribution, and comparison was made with a control group. All data were then analyzed in relation to either pre- or postoperative pulmonary hemodynamic data. In ventilation scans, the intrapulmonary distribution in the right lung was almost normal. In perfusion scans, an abnormal increased upper to lower lobe perfusion ratio greater than the normal value found in the control group was noted in seven patients (58.3%). There was a significant correlation (p less than 0.02) between the upper to lower lobe perfusion ratio and postoperative pulmonary vascular resistance. Furthermore, this perfusion ratio correlated inversely with the preoperative (p less than 0.005) and postoperative (p less than 0.02) right pulmonary artery area index, defined as the ratio of cross-sectional area to the normal value. Of five patients with less than 90% arterial oxygen saturation, four showed an abnormal distribution of pulmonary blood flow greater than the normal perfusion ratio. No patient had evidence of a pulmonary arteriovenous fistula by the echocardiographic contrast study. These results suggest that abnormal distribution of pulmonary blood flow to the upper lung segment may develop in patients after the Fontan procedure, and that insufficient size of the pulmonary artery before operation and the consequent postoperative elevation of pulmonary vascular resistance may be responsible for this perfusion abnormality.

Radionuclide evaluation of lung perfusion after the Fontan procedure

Lung perfusion was evaluated in 19 patients in whom a Fontan operation had been performed at a mean age of 3.7 years. First pass and equilibrium data were acquired during the lung particle perfusion scan 0.5 to 7.9 years (mean 3.7 years) following the Fontan procedure. Abnormalities of lung perfusion were documented in 8 patients. Minimal underperfusion of small areas of either right or left lung were noted in 4 patients, while the remaining 4 had evidence of major perfusion defects, involving both lungs. The perfusion defects were localized, in the majority of cases, on the side where a palliative procedure had been performed before the Fontan operation: it is of note that all our patients without palliative procedures did not show abnormalities in lung perfusion. Major abnormalities of lung perfusion seemed related to possible intimal thrombosis or emboli due to prolonged polycythemia or to pulmonary vessel distortion due to long-standing shunts.

Hemodynamic responses to isolated increments in heart rate by atrial pacing after a Fontan procedure

The physiologic role of the right ventricle has long been a subject of interest to physiologists. The Fontan operation provides a human model for studying the circulation in series devoid of a subpulmonic right ventricle. The hemodynamic response to isotonic exercise in this setting has been established, and differs appreciably from normal. However, the physiologic response to an increase in heart rate (atrial pacing) as an isolated variable has not been examined and compared to atrial pacing in hearts with two concordant subarterial ventricles. Accordingly, we compared the supine bicycle exercise response to rate-equivalent right atrial pacing in nine patients after atriopulmonary anastomoses (the Fontan operation) for single ventricle or tricuspid atresia. Cardiac index increased 77% with exercise (rest 2.6 L/min/m2; exercise 4.6 L/min/m2) but decreased 12% with atrial pacing (rest 2.5 L/min/m2; pacing 2.2 L/min/m2). Pulmonary arterial oxygen saturation declined significantly during exercise (rest 68%; exercise 31%) and during atrial pacing (control 72%; pacing 64%). The mean increment in pulmonary arterial pressure was 1.3 times greater with exercise (rest 14 mm Hg; exercise 20 mm Hg) than with pacing (control 12 mm Hg; pacing 16 mm Hg). Peak systemic arterial systolic pressure increased 14% with exercise but was unchanged by pacing. Systemic and pulmonary vascular resistances fell with exercise but changed insignificantly during atrial pacing. Stroke volume rose slightly with exercise but fell significantly with pacing.(ABSTRACT TRUNCATED AT 250 WORDS)

The modified Fontan operation for double inlet left ventricle. Surgical results, early haemodynamic and functional assessment

Twenty-one patients with a double inlet left ventricle underwent a modified Fontan between May 1979 and August 1987. All but the first patient in this series were operated upon after August 1984. Their age at operation ranged from 4 to 23 years with a median age of 8 years. Initial palliation was required in 12 patients and the mean interval to repair was 77.1 months, ranging from 38 to 112. Only one of the criteria of Choussat was exceeded in 12 patients. The pulmonary vascular resistance was always less than 4 Um2. A direct atriopulmonary anastomosis was performed in 19 patients and an aortic homograft interposition was used in 2. There was one hospital death due to acute cardiac failure and no late deaths. The average of the mean right and left atrial pressures measured early postoperatively was 12.9 and 8 mmHg respectively. A prolonged hospitalization with a mean of 23 days, ranging from 9 to 69, was required because of recurrent pleural and pericardial effusions which usually resolved after the first 6 postoperative months. The need for early anticoagulation is recommended to prevent the risk of pulmonary thromboembolism observed in 2 of our patients. Cardiac catheterization performed in 19 patients within 1 year after surgery showed that the average of the mean right atrial pressure had decreased to 11.3 mmHg without a gradient across the anastomosis in any case. Two patients required reoperation: one for enlargement of a restrictive ventricular septal defect and the other for closure of a recurrent dehiscence of the patch used for closure of the right a-v valve. Three patients developed a significant subaortic obstruction and have been scheduled for reoperation. Ventricular function was assessed at a mean interval of 11.9 months (17 patients) and 25.5 months (13 patients) from surgery. Gated equilibrium radionuclide ventriculography showed that the ejection fraction was normal (greater than or equal to 50%) and it had increased with time in 10. Yet, the response to exercise was normal in only 5 of the 13 patients re-evaluated. Treadmill exercise testing showed an increase in exercise tolerance from a mean of 7.4 min to a mean of 8.7 min.(ABSTRACT TRUNCATED AT 400 WORDS)