Darryl F. Shore

Characterization of Right Ventricular Diastolic Performance After Complete Repair of Tetralogy of Fallot Restrictive Physiology Predicts Slow Postoperative Recovery

BACKGROUND Prolonged postoperative recovery caused by a low cardiac output state occurs in some patients after complete repair of tetralogy of Fallot. Biventricular systolic function is usually well preserved in these patients. The contribution of impaired diastolic function, particularly of the right ventricle, has not been studied in detail; therefore, we performed a prospective study of right ventricular diastolic function in this patient group. METHODS AND RESULTS We studied biventricular systolic and diastolic function using Doppler echocardiographic examination. Tricuspid valve, superior vena caval, pulmonary arterial, and mitral valve Doppler spectrals were obtained during the first postoperative day in 35 patients aged 6 months to 45 years who underwent complete repair of tetralogy of Fallot. Biventricular systolic function was grossly normal in all patients. Isolated restrictive right ventricular physiology characterized by pulmonary arterial antegrade flow coincident with atrial systole and associated with prominent retrograde superior vena caval flow was seen in 17 of the 35 patients (group 1). This flow was augmented during the expiratory phase of positive pressure ventilation and abolished or greatly diminished during the inspiratory phase (P < .001). An increase in the duration of pulmonary regurgitation occurred during the inspiratory phase of positive pressure ventilation in these patients (P < .01). All patients with right ventricular restriction had a clinical picture compatible with a low cardiac output state, requiring prolonged stays in intensive care and the hospital. Clinical improvement was mirrored by resolution of the Doppler markers of right ventricular restriction in most of the patients. CONCLUSIONS Isolated right ventricular restriction is characterized by antegrade diastolic pulmonary arterial flow on Doppler echocardiography and is responsible for the slower postoperative course and clinical evidence of low cardiac output state in some patients after complete repair of tetralogy of Fallot.

Cardiopulmonary Interactions After Fontan Operations Augmentation of Cardiac Output Using Negative Pressure Ventilation

BACKGROUND The low-output state is the chief cause of morbidity and mortality after Fontan operations. An alternative hemodynamic tool would be a welcome addition for these patients, who are typically resistant to conventional therapeutic measures. METHODS AND RESULTS The hemodynamic effects of conversion from conventional intermittent positive pressure ventilation (IPPV) to cuirass negative pressure ventilation (NPV) was investigated in nine acute postoperative Fontan patients on the pediatric intensive care unit and nine anesthetized patients undergoing cardiac catheterization in the convalescent phase after Fontan operations. Pulmonary blood flow was measured using the direct Fick method during IPPV and after a brief period of NPV. In one subgroup of patients, pulmonary blood flow was measured again after reinstitution of IPPV, and in a second subgroup, pulmonary blood flow was measured after an extended period of NPV. A brief period of NPV increased pulmonary blood flow from 2.4 to 3.5 L x min(-1) x /m(-2), with a mean increase of 42%. Pulmonary blood flow continued to improve, with a total increase of 54% after an extended period of NPV. Values fell toward baseline after reinstitution of IPPV. Heart rate was unchanged during NPV, and the improvement in pulmonary blood flow was achieved by an increase in stroke volume from 25 mL/m2 to 37 mL/m2. CONCLUSIONS Through improvement of the stroke volume alone, NPV brought about a marked increase in the pulmonary blood flow and, hence, cardiac output of Fontan patients. An improvement in cardiac output of this order, and by this mechanism, is currently unmatched by any therapeutic alternatives.

Relationship Between Type of Outflow Tract Repair and Postoperative Right Ventricular Diastolic Physiology in Tetralogy of Fallot Implications for Long-term Outcome

BACKGROUND Restrictive right ventricular (RV) physiology can be present early and late after tetralogy of Fallot repair. It is associated with a complicated early postoperative course but is favorable late after repair because it is associated with less pulmonary regurgitation, better exercise tolerance, and less QRS prolongation and symptomatic ventricular arrhythmias. It is not known, however, whether in the current surgical era, this physiology is present in tetralogy of Fallot patients at mid-term follow-up and whether it is related to the type of RV outflow tract repair. Finally, the impact of this physiology on the early evolution of QRS prolongation has not been examined previously. In this study we attempted to address these issues in a cohort of recently operated patients. METHODS AND RESULTS Ninety-five patients were studied 4.3 years after repair by Doppler echocardiography, serial electrocardiograms, and chest radiographs. Restrictive RV physiology defined by the presence of antegrade pulmonary artery flow in late diastole was present in 38% of the patients. It was more common in patients with transannular patch (TAP) repair compared with non-TAP repair (50% versus 21%, P < .05). QRS duration at follow-up was 121.2 +/- 17.6 and 132.6 +/- 11.8 ms in restrictive and nonrestrictive patients with TAP repair, respectively (P < .02). CONCLUSIONS Restrictive RV physiology has been identified at mid-term follow-up in a contemporary surgical series. It is associated with less QRS prolongation, regardless of the technique used for outflow tract repair, and may be associated with fewer long-term complications. Nonrestrictive physiology is associated with the most marked QRS prolongation. This subgroup is most at risk from the late deleterious consequences of chronic pulmonary regurgitation.

Should atrial septal defects in adults be closed

BACKGROUND By assessing current surgical outcome and symptomatic relief, this study attempts to answer whether atrial septal defects in adults should be closed. METHODS Thirty-nine adult patients aged 35.2 +/- 13.6 years underwent operation for an atrial septal defect between June 1988 and June 1994. Indications for closure were symptoms (33 patients) or a significant left-to-right atrial shunt (6 patients). Data were obtained from hospital records, and the latest status of the patients was determined by a written questionnaire. RESULTS There were no deaths. Pulmonary embolism in 1 patient was the only complication observed. The QRS duration on the surface electrocardiogram decreased immediately (p < 0.001), and the cardiothoracic ratio on chest radiographs was significantly lower 3 to 6 months after operation (p < 0.001), both findings reflecting improved hemodynamics. No residual shunts were seen on follow-up (mean follow-up, 3.3 +/- 2.2 years). Twenty-seven (81.8%) of the 33 symptomatic patients improved clinically in terms of exercise performance, atrial arrhythmias, or both. Three (50%) of the 6 previously asymptomatic patients reported improved functional capacity post-operatively. CONCLUSIONS Today, operation for atrial septal defects in adults can be performed with no mortality and low morbidity and results in symptomatic improvement in the majority of patients. Clinical improvement was seen even in patients who considered themselves asymptomatic preoperatively. We advocate closure of atrial septal defects in adult patients with symptoms or significant atrial shunts.

Passive Stiffness of Myocardium From Congenital Heart Disease and Implications for Diastole

Background— In ventricular dilatation or hypertrophy, an elevated end-diastolic pressure is often assumed to be secondary to increased myocardial stiffness, but stiffness is rarely measured in vivo because of difficulty. We measured in vitro passive stiffness of volume- or pressure-overloaded myocardium mainly from congenital heart disease. Methods and Results— Endocardial ventricular biopsies were obtained at open heart surgery (n=61; pressure overload, 36; volume-overload, 19; dilated cardiomyopathy, 4; normal donors, 2). In vitro passive force-extension curves and the stiffness modulus were measured in skinned tissue: muscle strips, strips with myofilaments extracted (mainly extracellular matrix), and myocytes. Collagen content (n=38) and titin isoforms (n=16) were determined. End-diastolic pressure was measured at cardiac catheterization (n=14). Pressure-overloaded tissue (strips, extracellular matrix, myocytes) had a 2.6- to 7.0-fold greater force and stiffness modulus than volume-overloaded tissue. Myocyte force and stiffness modulus at short stretches (0.05 resting length, L0) was pressure-overloaded >normal≈volume-overloaded>dilated cardiomyopathy. Titin N2B:N2BA isoform ratio varied little between conditions. The extracellular matrix contributed more to force at 0.05 L0 in pressure-overloaded (35.1%) and volume-overloaded (17.4%) strips than normal myocardium. Stiffness modulus increased with collagen content in pressure-overloaded but not volume-overloaded strips. In vitro stiffness modulus at 0.05 L0 was a good predictor of in vivo end-diastolic pressure for pressure-overloaded but not volume-overloaded ventricles and estimated normal end-diastolic pressure as 5 to 7 mm Hg. Conclusions— An elevated end-diastolic pressure in pressure-overloaded, but not volume-overloaded, ventricles was related to increased myocardial stiffness. The greater stiffness of pressure-overloaded compared with volume-overloaded myocardium was due to the higher stiffness of both the extracellular matrix and myocytes. The transition from normal to very-low stiffness myocytes may mark irreversible dilatation.

Coagulation factor abnormalities after the Fontan procedure and its modifications

OBJECTIVE Recently we reported the prevalence of thromboembolism in patients who underwent the Fontan procedure and its modifications. Although hemodynamic factors may well contribute to thromboembolism, recent evidence suggests that coagulation factor abnormalities may also play a role. We therefore set out to investigate the coagulation status in a group of patients who had undergone the Fontan procedure. METHODS The study population consists of 20 children who had undergone the Fontan procedure and its modifications. They were examined for coagulation factor abnormalities. Concentrations of serum albumin, total protein, and liver enzymes were also measured. The median age at the time of the operation was 6.2 years (17 months to 8 years) with a male/female ratio of 2.3:1. The median time from the Fontan repair was 4.9 years (18 to 76 months). RESULTS Protein C (p < 0.001), protein S (p < 0.02), and factor VII (p < 0.001) were significantly lower than the normal range. The changes in serum albumin and total protein and factors II, IX, and X were not significant. CONCLUSIONS It is possible that deficiency in protein C, protein S, and factor VII partly account for the prevalence of thromboembolism after Fontan-type repairs. The risk of long-term anticoagulation should be weighed against the best palliative procedure for these patients. We suggest that reduced protein C, protein S, and factor VII levels in this group of patients should be regarded as risk factors and that such patients should be treated with anticoagulants.

Clinical Outcomes of Surgical Pulmonary Valve Replacement after Repair of Tetralogy of Fallot and Potential Prognostic Value of Preoperative Cardiopulmonary Exercise Testing

Background— Indications for surgical pulmonary valve replacement (PVR) after repair of tetralogy of Fallot have recently been broadened to include asymptomatic patients. Methods and Results— The outcomes of PVR in adults after repair of tetralogy of Fallot at a single tertiary center were retrospectively studied. Preoperative cardiopulmonary exercise testing was included. Mortality was the primary outcome measure. In total, 221 PVRs were performed in 220 patients (130 male patients; median age, 32 years; range, 16–64 years). Homografts were used in 117 patients, xenografts in 103 patients, and a mechanical valve in 1 patient. Early (30-day) mortality was 2%. Overall survival was 97% at 1 year, 96% at 3 years, and 92% at 10 years. Survival after PVR in the later era (2005–2010; n=156) was significantly better compared with survival in the earlier era (1993–2004; n=65; 99% versus 94% at 1 year and 98% versus 92% at 3 years, respectively; P=0.019). Earlier era patients were more symptomatic preoperatively (P=0.036) with a lower preoperative peak oxygen consumption (peak O2; P<0.001). Freedom from redo surgical or transcatheter PVR was 98% at 5 years and 96% at 10 years for the whole cohort. Peak O2, E/CO2 slope (ratio of minute ventilation to carbon dioxide production), and heart rate reserve during cardiopulmonary exercise testing predicted risk of early mortality when analyzed with logistic regression analysis; peak O2 emerged as the strongest predictor on multivariable analysis (odds ratio, 0.65 per 1 mL·kg−1·min−1; P=0.041). Conclusions— PVR after repair of tetralogy of Fallot has a low and improving mortality, with a low need for reintervention. Preoperative cardiopulmonary exercise testing predicts surgical outcome and should therefore be included in the routine assessment of these patients.

PRIMARY BALLOON DILATATION OF COARCTATION OF THE AORTA IN NEONATES

Primary balloon dilatation of coarctation of the aorta was attempted in 10 consecutive neonates (age range 2-23 days). The coarctation site was crossed and the balloon inflated in all but one patient. In two patients with associated severe isthmal hypoplasia there was no change in the gradient after dilatation. In the remainder, the residual gradients were trivial and angiography showed complete relief of coarctation. Severe recoarctation developed 5-12 weeks after dilatation in five patients, each considered to have had an excellent initial result. The coarctation was rapidly progressive in three patients in whom Doppler studies within two weeks of the development of recoarctation had shown no significant gradient. In the other two patients progressive restenosis was charted by Doppler examinations over the course of 6-8 weeks. Three patients had a second, initially successful, dilatation procedure. One patient remained well with no residual gradient 18 weeks later. Stenosis recurred within eight weeks in the other two, and both have undergone successful surgical repair. Balloon dilatation of a native coarctation of the aorta gave excellent immediate results in most neonates. Severe isthmal hypoplasia is, however, a contraindication to balloon dilatation and early restenosis is an important problem. These results do not support the continued use of primary balloon dilatation of coarctation of the aorta in neonates.

Complete Atrioventricular Septal Defect, Down Syndrome, and Surgical Outcome: Risk Factors

BACKGROUND This study was conducted to evaluate surgical outcome and to identify risk factors for hospital mortality and reoperation after repair of complete atrioventricular septal defect. METHODS A total of 147 consecutive children underwent repair between January 1986 and December 1998. Of those, 106 had Down syndrome, 37% had normal chromosomes, and 4 had other syndromes; 108 underwent primary repair, 19 had prior pulmonary artery banding, and 20 had additional tetralogy of Fallot. The median weight at primary repair was 4.5 kg. A two-patch technique was used in 88%. RESULTS The 30-day mortality was 15% (70% confidence interval [CI] 12% to 19%). A double orifice atrioventricular valve was found to be a significant risk factor (p = 0.002), with 6 of 11 patients dying. If double orifice atrioventricular valve patients are excluded, the mortality rate falls to 12% (70% CI 9% to 15%). No difference in mortality was found between Down syndrome and chromosomally normal children but the latter more commonly required reoperation. Chromosomally normal children frequently have a dysplastic common atrioventricular valve (24% versus 3% in Down children, p < 0.001). In a multivariate Cox model including both variables, the presence of a dysplastic atrioventricular valve was a significant risk factor for reoperation. After controlling for the presence of a dysplastic atrioventricular valve, Down syndrome retained a significant protective effect but the upper limit of the confidence interval was close to 1. CONCLUSIONS The presence of a double orifice atrioventricular valve emerged as an unforeseen risk factor for death.

Oxygen consumption after cardiopulmonary bypass surgery in children: determinants and implications.

OBJECTIVE We sought to assess oxygen consumption and its determinants in children shortly after undergoing cardiopulmonary bypass operations. METHODS Twenty children, aged 2 months to 15 years (median, 3.75 years), undergoing hypothermic cardiopulmonary bypass operations were studied during the first 4 hours after arrival in the intensive care unit. Central and peripheral temperatures were monitored. Oxygen consumption was continuously measured by using respiratory mass spectrometry. Oxygen delivery was calculated from oxygen consumption and arterial and mixed venous oxygen contents, which were sampled every 30 minutes. Oxygen extraction was derived by the ratio of oxygen consumption and oxygen delivery. Arterial blood lactate levels were measured every 30 minutes. RESULTS There was a correlation between oxygen consumption and age in patients older than 3 months (r = -0.76). Mean oxygen consumption increased by 14.7% during the study. The increase in oxygen consumption was correlated with the increase in central temperature (r = 0.73). Nine patients had an arterial lactate level above 2 mmol/L on arrival. There were no significant differences in oxygen consumption, oxygen delivery, and oxygen extraction between the group with lactate levels between 2 and 3 mmol/L and the groups with normal lactate levels both on arrival and at 2 hours. One patient with a peak lactate level of 6.8 mmol/L had initially low oxygen delivery (241.3 mL. min(-1). m(-2)). CONCLUSIONS During the early hours after a pediatric cardiac operation, the increase in oxygen consumption is mainly attributed to the increase in central temperature. Oxygen consumption is negatively related to age. Mild lactatemia is common and does not appear to reflect oxygen delivery or oxygen consumption or a more complicated recovery.