Tain-Yen Hsia

Initial Experience With a Miniaturized Multiplane Transesophageal Probe in Small Infants Undergoing Cardiac Operations

PURPOSEnThere has been reluctance to use intraoperative transesophageal echocardiography (TEE) in small infants. We assessed the utility and safety of a new miniaturized multiplane micro-TEE probe in small infants undergoing cardiac operations.nnnDESCRIPTIONnHemodynamic and ventilation variables were prospectively recorded before and after micro-TEE insertion and removal in infants weighing 5 kg or less undergoing cardiac operations.nnnEVALUATIONnThe study included 42 patients with a mean weight of 3.6 +/- 0.9 kg (range, 1.7 to 5 kg). All probe insertions were successful. There were no complications or clinically significant changes in hemodynamic or ventilation variables. Information provided by TEE resulted in surgical revision in 6 of the 42 patients.nnnCONCLUSIONSnThe micro-TEE provides high quality, useful diagnostic images without hemodynamic or ventilation compromise in small infants undergoing cardiac operations. This advance is important with the growing trend towards complete repair of complex structural heart disease in small infants.

Right Ventricle-to-Pulmonary Artery Shunt: Alternative Palliation in Infants With Inadequate Pulmonary Blood Flow Prior to Two-Ventricle Repair

BACKGROUNDnTraditional palliation of infants with biventricular hearts and inadequate pulmonary blood flow is a modified Blalock-Taussig shunt. The aim of this report is to assess the results of an alternative, right ventricle-to-pulmonary artery (RV-PA) shunt.nnnMETHODSnBetween August 2004 and July 2007, 10 infants with biventricular hearts and inadequate pulmonary blood flow underwent palliation with an RV-PA shunt. Median age was 9 days (range, 4 to 86), weight was 3.0 kg (1.7 to 4.5), and 4 of 10 patients weighed less than 2.5 kg. Shunts were nonvalved Gore-Tex (W.L. Gore Assoc, Flagstaff, AZ), and size was 6 mm (n = 5) or 5 mm (n = 5).nnnRESULTSnThere were no operative deaths. Median oxygen saturation at hospital discharge was 95% (87 to 98). In 2 patients the shunt was partially narrowed with a metal clip; they underwent successful balloon dilation 6 months after shunt placement. Eight patients have undergone two-ventricle repair 6 to 17 months after shunt placement. At the time of complete repair, oxygen saturation was 86 +/- 1% and weight was 7.7 +/- 1.7 kg. Repairs included a valved RV-to-PA conduit, 14 to 16 mm in diameter. There was one interstage death.nnnCONCLUSIONSnThe RV-PA shunt provides successful palliation in infants with biventricular heart disease and inadequate pulmonary blood flow. It can be used in low birth weight infants and allows significant growth with protection of oxygen saturation prior to complete repair. Partial clipping of the shunt with subsequent balloon dilation is an option to prolong palliation. These results compare favorably with those of a modified Blalock-Taussig shunt or single stage complete repair.

Determinants of extracellular matrix remodelling are differentially expressed in paediatric and adult dilated cardiomyopathy

The left ventricular phenotype of idiopathic dilated cardiomyopathy (DCM) can appear similar in paediatric and adult patients. However, the aetiology of paediatric DCM is usually idiopathic, and often leads an aggressive clinical course. A structural underpinning of DCM is extracellular matrix changes, which are determined by a balance between matrix metalloproteinases (MMPs) and tissue inhibitors of MMPs (TIMPs). This study tested the hypothesis that different MMP/TIMP profiles occur in paediatric and adult DCM patients.

Plasma profiling determinants of matrix homeostasis in paediatric dilated cardiomyopathy.

OBJECTIVEnDilated cardiomyopathy is an important cause of cardiac failure in both children and adults, but is more progressive in children. In adult dilated cardiomyopathy, left ventricular remodelling is associated with changes in the plasma levels of matrix metalloproteinases and tissue inhibitor of metalloproteinases. Plasma matrix metalloproteinases and tissue inhibitors of metalloproteinase changes in paediatric dilated cardiomyopathy have not been examined. This study developed a low blood volume, high-sensitivity assay to test the hypothesis that unique and differential plasma matrix metalloproteinases and tissue inhibitors of metalloproteinase profile exist in patients with paediatric dilated cardiomyopathy.nnnMETHODS/RESULTSnA systemic blood sample (1 millilitre) was obtained from seven children aged 8 plus or minus 7 years with dilated cardiomyopathy and 26 age-matched normal volunteers. Using a high-throughput multiplex suspension immunoassay, plasma levels were quantified for collagenases (matrix metalloproteinase-8), gelatinases (matrix metalloproteinase-2 and -9), lysins (matrix metalloproteinase-3 and -7), and tissue inhibitor of metalloproteinases-1, -2, and -4. The matrix metalloproteinase to tissue inhibitors of metalloproteinases ratios were also calculated. The plasma matrix metalloproteinase-2, -7, -8, and -9 levels were increased by greater than twofold in patients with dilated cardiomyopathy than normal patients (with p less than 0.05). Patients with dilated cardiomyopathy also had significantly higher tissue inhibitors of metalloproteinases-1 and -4 (298% and 230%; with p less than 0.05).nnnCONCLUSIONSnThese unique findings show that a specific plasma matrix metalloproteinase/tissue inhibitor of metalloproteinase profile occurs in paediatric dilated cardiomyopathy when compared to the cases of normal children. These distinct differences in the determinants of myocardial matrix structure and function may contribute to the natural history of dilated cardiomyopathy in children and may provide a novel biomarker platform in paediatric dilated cardiomyopathy.

Design of an Experimental Mock Circulatory System for the Fontan Circulation

Each year, a small fraction of children are born with univentricular hearts, causing the lethal blue baby syndrome. Several preliminary operations are required to buy time until the child’s blood vessels grow to sufficient size. Once the child reaches an age of 3–5 years, the blood vessels have grown enough for the Stage 3 Fontan operation, in which the superior and inferior vena cavae are coupled directly to the pulmonary arteries in a cruciform junction [2,3]. After this operation, the heart is only pumping blood to the systemic circulation. Only residual pressure in the systemic veins and intrathoracic pressure change with respiration drive the flow into the lungs [5]. This circulation decreases the load on the heart, allowing the patients to survive with normal blood oxygen levels. This circulation decreases the load on the heart, allowing the patients to survive into their 20s and 30s. An aim of this study is to develop an experimental model of the Fontan circulation that can be readily adapted to simulate patient specific anatomies so as to assist in potential surgical decisions. Of interest is the study of chronic venous hypertension, a result of the Fontan circulation having no heart “vacuum” at the end of the vena cavae; it is known to cause liver failure. We also intend to examine the hypothesis of Hsia et al. [6] that decreasing sub-diaphragmatic venous flow reversal will improve functional outcome of the Fontan.Copyright

PRESSURE VOLUME LOOP ANALYSIS IN PATIENTS WITH SINGLE VENTRICLES: COMPARISON OF PRESSURE-VOLUME LOOP AND NON-INVASIVE MEASURES OF SYSTOLIC FUNCTION

Non-invasive measurements of systolic function in the single ventricle population are performed using measures whose accuracy and reliability have not been fully assessed. We sought to validate non-invasive measures of systolic function with invasive measures of systolic function derived from

Shear Stress Exposure Measurements on the Motionless Fluid Diode Valve in the Pulmonary Position

Pulmonary insufficiency is one of the consequences of congenital heart disease, and currently no permanent solution exists. The concept of a motionless diode valve to regulate the pulmonary circulation has been proposed and previously studied. The diode valve has shown the ability to regulate flow with levels of regurgitation and pressure gradient that are acceptable within the pulmonary circulation [1].Copyright

In Vitro Study of Pulsatile Flow Through a Motionless Diode Valve in the Pulmonary Position

Pulmonary circulation shows a tolerance for mild regurgitation and pressure gradient. [1]. Given these tolerances, we have explored using a fluid diode as a pulmonary valve. Camp et al showed that diode valves are able to regulate flow in the pulmonary position with promising results and could be tolerated using a pig model [2, 3]. Flow and shear stress patterns are two other hemodynamic concerns that must be considered during heart valve design. Elevated bulk flow shear stresses, wall shear stresses, and turbulent stresses within bioprostheses and mechanical valve flow fields are recognized as a cause of cell and platelet damage, initiating platelet activation and triggers for thrombogenesis [4–7]. In this study, we conduct in vitro flow field analysis of the flow downstream of a proposed prototype diode valve in order to observe the flow and shear stress patterns.Copyright

Comparison of In Vitro and In Vivo Testing of Fluid Diodes as a Pulmonary Heart Valve Replacement

The operating pressures in the right heart are significantly lower than those of the left heart and with marked differences in the circulation impedances. The pulmonary circulation shows a tolerance for mild regurgitation and pressure gradient [1]. Pulmonary regurgitation fractions on the order of 20% and transvalvular pressure gradients of less than 25mm Hg are considered mild [2]. Given this tolerance, we examine the concept of using a motionless valve to regulate flow in the pulmonary position. In a previous study, the use of fluid diodes was shown to be a promising concept for use as a pulmonary valve [3]. In this study, we test a fluid diode both in a bench top circulatory system [4] and in a swine model and compare the pressure gradients and regurgitant fractions.Copyright