A Pediatric Ventricular Assist Device: Its Development and Experimental Evaluation of Hemodynamic Effects on Postoperative Heart Failure of Congenital Heart Diseases

To evaluate the effectiveness of a pediatric ventricular assist device (VAD), hemodynamic effects of the VAD were investigated experimentally in two types of postoperative profound heart failure models of congenital heart disease. In the model I Fontan or modified Fontan operation model, right ventricular pump function was excluded surgically and a shunt between the right atrium and the pulmonary artery was constructed in four dogs. With a VAD between the left atrium and the aorta, pressure gradient across the lung and the cardiac output increased. Right ventricular failure was induced surgically and high pulmonary vascular resistance was made by injection of glass beads in five dogs in model II. Cardiac output increased and the right atrial pressure decreased when a VAD between the right atrium and the pulmonary arterial trunk was activated. In conclusion, the VAD will become a promising modality to manage pediatric profound heart failure cases.     

Hemodynamic evaluation of heterotopic heart transplantation.

To assess the relative contribution of native and donor hearts to total circulatory performance after heterotopic transplantation, we used cardiac catheterization to examine 10 patients. Left and right ventricular filling pressures significantly decreased by 41% and 36%, respectively, cardiac index increased by 25%, and pulmonary arteriolar resistance was reduced by 61%. Patients were subdivided into two groups according to the presence of one (group I) or two (group II) peaks on the aortic pressure curve. In group I, the donor left ventricle assumed total left ventricular work and 80% of right ventricular work. Because the native left ventricle could not generate enough pressure to open the aortic valve, its entire stroke volume was ejected into the common left atrium. In addition, in all four patients a native aortic regurgitation occurred in diastole and systole. In contrast, in group II, native left ventricular systolic pressure always exceeded aortic diastolic pressure. The donor left ventricle contributed 68% to systemic blood flow and the donor right ventricle 51% to pulmonary blood flow. Mild native aortic regurgitation was demonstrated in two patients only. Native left ventricular function deteriorated postoperatively in all patients (ejection fraction decreased from 0.22 +/- 0.09 to 0.14 +/- 0.08), but this deterioration was more marked in group I. Postoperative depression of native left ventricular function could not be ascribed to progression of coronary artery disease but was mainly due to reduced preload (competitive filling) and increased afterload. Thus in group I patients with more severe preoperative left ventricular dysfunction, the donor heart behaved like a total biventricular assist device. In contrast, in group II patients the donor heart acted like a partial biventricular assist device.     

Stage I palliation of hypoplastic left heart syndrome: the importance of neoaorta construction

After Norwood's initial report of successful first-stage palliation of hypoplastic left heart syndrome in neonates, the occurrence of distal aortic obstructions, shunt problems, and late deaths have led to modifications in the surgical technique. Between January 1986 and December 1987, 12 neonates from three to 16 days old underwent stage I palliation with the same objectives. An open atrial septectomy was always performed. The pulmonary artery bifurcation was transected from the main pulmonary artery and closed with an aortic homograft patch. The aortotomy was begun 2 cm below the patent ductus arteriosus insertion and extended across the transverse arch and down the ascending aorta. The neoaorta was constructed using the hypoplastic ascending aorta-transverse aortic arch, the main pulmonary artery, and an aortic homograft augmentation patch. The homograft is hemostatic and pliable, and molds well in forming the neoaorta. A 4-mm shunt was inserted between the right innominate artery and the right pulmonary artery in 5 patients and the neoaorta and the pulmonary artery bifurcation patch in 7 patients. The early systemic oxygen saturation was optimized at 75% to 80% with hyperventilation, high concentration of inspired oxygen, sodium bicarbonate, and the frequent use of vasopressors to maintain an arterial blood pressure of 65 to 75 mm Hg. Two patients (17%) died early after operation; 1 had severe right ventricular dysfunction and both had severe tricuspid regurgitation. There were 2 late deaths at 7 and 13 months, of sepsis and hypoxia. The 8 survivors (67%) continue to do well over follow-up. The preoperative tricuspid regurgitation has remained stable in 3 survivors and disappeared in 2 survivors.(ABSTRACT TRUNCATED AT 250 WORDS)     

Patent foramen ovale: a cause of significant post-coronary artery bypass grafting morbidity

We describe two patients who underwent coronary artery bypass grafting complicated by postoperative hypoxemia due to a patent foramen ovale with right-to-left shunting. We discuss different hypotheses to explain the shunt: decreased right ventricular compliance, right atrial geometric changes due to septal distension or ischemia, exceeding filling pressure and localised haemorragic pericardial tamponade and low atrial pressure when correcting aortic stenosis. We emphasize the close interplay of pericardectomy and the four cardiac chambers including the distortion of the heart axis. The contrast echo produced by microbubbles of air is the safest and the most accurate procedure to detect the shunt. The two patients progressed positively with an extracorporeal circulation of short duration and without complications linked to the intervention. We conclude that postoperative unexplained hypoxemia must always exclude diagnosis of right-to-left shunting due to a patent foramen ovale (PFO).     

A case report of definitive repair for pulmonary atresia and intact ventricular septum associated with aortic valve regurgitation

A successful definitive repair for a 10-year-old girl with pulmonary atresia and intact ventricular septum (PA.IVS) associated with aortic valve regurgitation is described. The Fontan type repair was not indicated in this case because of the left ventricular dysfunction due to aortic valve regurgitation and inadequate size of the pulmonary artery. Therefore, right ventricular outflow tract reconstruction, Glen shunt and aortic valve replacement were performed despite severe hypoplastic right ventricle (RVEDVI; 33% of normal) and restrictive tricuspid valve (TVD; 48% of normal). Postoperatively, good result was obtained. There is general agreement that biventricular repair could be safely performed using Glenn shunt, when RVEDVI is above 40% of normal and TVD is above 50% of normal in a patient with PA.IVS. Moreover recently including our case, several successful repairs for PA.IVS with more hypoplastic right ventricle and tricuspid valve have been reported. So it is suggested that the right ventricular outflow tract reconstruction and Glenn shunt can be reliably applied for PA.IVS with more hypoplastic right ventricle and more restrictive tricuspid valve. To our knowledge, this is the first successful report of definitive repair (right ventricular outflow tract reconstruction, Glenn shunt and AVR) for PA.IVS associated with AR.     

Use of a Paracorporeal Pneumatic Ventricular Assist Device for Postoperative Cardiogenic Shock in Two Children with Complex Cardiac Lesions

Pneumatic ventricular assist device (VAD) was utilized for cardiogenic shock after intracardiac operation in two children with complex cardiac anomalies based with single ventricle. In the first case (a 10-year-old), after a modified Fontan operation, VAD was placed between the functional left atrium and ascending aorta, serving as a "artificial single ventricle" with neither pumping chamber nor artificial support in the right side of the heart. The systemic circulation was maintained by keeping relatively high central venous pressure. In another child (a 3-year-old) who underwent repair of incompetent atrioventricular valve leaving intracardiac lesions, VAD was placed between the common atrium and ascending aorta, serving as a pump for both pulmonary and systemic circulation with regulation of pulmonary blood flow through an aortopulmonary Gore-Tex shunt. The circulatory assist with VAD was utilized for 5 and 6 days, respectively. Although weaning from the device was not feasible in both patients because of the pulmonary dysfunction, these experience showed the possible use of VAD for cardiogenic shock after surgery in patients with complex cardiac anomalies.     

Pulmonary stenosis and impaired myocardial function.

Two young Black female patients with pulmonary valve stenosis and intact ventricular septa are presented in protracted congestive cardiac failure with severe tricuspid insufficiency and, in one, atrial fibrillation. Right ventricular systolic dysfunction was manifested by peak systolic pressures below systemic level, raised end-diastolic pressures and low cardiac output, but without right-to-left shunt. These findings are in strong contrast to those found in most patients with pulmonary stenosis of long standing, where persistent impairment of right ventricular function is diastolic with a high end-diastolic pressure and reversal of an interatrial shunt which result from poor right ventricular compliance.Evidence of left ventricular dysfunction was also present in both cases. Protracted heart failure in these patients is believed to have been the result of coincidental cardiomyopathy in a racial group highly predisposed to this disorder. A diagnostic appreciation of this phenomenon is important in the evaluation of heart disease in the Black, since cardiomyopathy may modify or even mask the features of the underlying disorder.     

Post aortic left innominate vein in a patient with a surgically corrected double outlet right ventricle]

We report the presence of a post aortic left innominate vein (PALIV) in a patient with a surgically corrected double outlet right ventricle. A 30-year-old male was admitted to our hospital with exertional dyspnea. The patient had undergone right ventricular outflow tract reconstruction and closure of ventricular septal defect at the age of 14. Echocardiography and cardiac catheterization showed severe pulmonary regurgitation and a residual ventricular septal shunt. After resternotomy, right ventricular outflow tract reconstruction and residual shunt closure were performed. During the operation, the left innominate vein was not found in front of the aorta. Postoperative cardiac catheterization and computed tomography showed that the left innominate vein was positioned behind the ascending aorta draining to the superior caval vein.     

Preliminary result of an algorithm to select proper ventricular assist devices for high-risk patients with extracorporeal membrane oxygenation support.

BACKGROUND: Extracorporeal membrane oxygenation (ECMO) is not suitable for long-term support because of its high incidence of complications. Conversion from ECMO to ventricular assist device (VAD) is reasonable, and we have developed a simple algorithm for selecting proper VADs for these ECMO-supported patients. METHODS: We converted 12 patients who were receiving ECMO support to VAD for bridge to transplantation. Group I (n = 6) was converted directly from ECMO to VAD. Group II (n = 6) underwent stage conversion. We added left atrial drainage to ECMO because of lung edema or marked left heart distension. We discontinued drainage after recovery of right heart function. Group II had more unfavorable risk factors for VAD before ECMO. RESULTS: Three patients (50%) in Group I received biventricular VADs. The other 3 patients were converted to left ventricular assist device (LVAD), but only 1 (16.7%) experienced successful conversion. We successfully converted 5 patients (83.3%) in Group II to LVAD without right VAD, and 4 of them could be weaned from the ventilator. The multiple-organ dysfunction score gradually improved in Group II despite additional surgery. Two patients in each group received heart transplantation and survived long term. CONCLUSION: Using a conversion protocol provides a good guideline for making decisions. According to the protocol, right heart and pulmonary function can be clearly assured before shifting to LVAD in these critical ECMO-supported patients.     

Right ventricular aneurysm following modified Norwood-Sano operation for hypoplastic left heart syndrome

Hypoplastic left heart syndrome is a rare congenital heart defect characterized by underdevelopment of left-sided heart structures, including the aortic arch. The contemporary surgical management of this anomaly includes the Norwood procedure and provision of pulmonary blood flow by either a modified Blalock-Taussig shunt (MBTS) or a right ventricle-to-pulmonary artery (RV-PA) conduit, commonly referred to as the Sano shunt. We report on an unusual complication of the Sano shunt, that of a giant right ventricular pseudoaneurysm occurring at the shunt insertion site.     

Epikardiale Echokardiographie

Epicardial echocardiography has been available since the early 1970s as an intraoperative diagnostic modality to assess ventricular and valvular function. With this technique, an ultrasonic transducer is placed directly on the epicardial surface of the heart, following sternotomy and pericardiotomy. Under the guidance of the cardiac anesthesiologist, the surgeon places the transducer so that the desired views of cardiac structures and great vessels can be obtained. The anesthesiologist performs the acquisition, analysis and interpretation of the echocardiographic images. Despite the feasibility of epicardial echocardiography, transesophageal echocardiography (TEE) has emerged over the last two decades as the main form of intraoperative echocardiography. Although TEE allows continuous monitoring of cardiac and valvular function without interruption of the surgical procedure, placement of a TEE probe may be difficult or contraindicated in some patients. In such cases, epicardial echocardiography may be the optimal ultrasonographic imaging modality to assess ventricular and valvular function during cardiac surgery. We describe the use of epicardial echocardiography for intraoperative assessment of valvular function in two patients where TEE was either contraindicated or probe placement could not be performed safely. The first patient underwent surgical repair of the mitral valve for severe mitral regurgitation. After weaning the patient from cardiopulmonary bypass (CPB), epicardial echocardiography was used to confirm successful reconstruction of the valve and to exclude residual mitral regurgitation. The second patient was scheduled for coronary artery bypass grafting (CABG). Prior to the initiation of CPB, the presence of moderate aortic stenosis was confirmed using Doppler echocardiography via an epicardial approach.     

Numerical simulation of cardiovascular dynamics with left heart failure and in-series pulsatile ventricular assist device

This article presents a numerical model for investigations of the human cardiovascular circulation system response, where the function of the impaired left ventricle is augmented by the pumping action of a pulsatile ventricular assist device (VAD) connected in series to the native heart. The numerical model includes a module for detailed heart valve dynamics, which helps to improve the accuracy of simulation in studying the pulsatile type VAD designs. Simulation results show that, for the case with left ventricular (LV) failure, the VAD support successfully compensates the impaired cardiovascular response, and greatly reduces the after-load of the diseased ventricle, thus assisting possible recovery of the ventricle from the diseased condition. The effects of these conditions on pulmonary circulation are also shown. To investigate the effect of different pumping-activation functions (VAD motion profiles) on the cardiovascular response, three different VAD motion profiles are investigated. The numerical results suggest that Hermitian type motion profiles (smooth curves skewed toward early systole) have the advantage of requiring minimum power to the VAD, and producing the minimum after-load to the left ventricle, minimum ventricular wall stress, and minimum ventricular work to the diseased ventricle; while sawtooth type motions need slightly more power input, and induce slightly increased aortic pressure in diastole, thus improving coronary perfusion.     

Pulmonary artery configuration after palliative operations for hypoplastic left heart syndrome

Pulmonary artery architecture and symmetry after palliative operations for hypoplastic left heart syndrome may affect subsequent suitability for a modified Fontan operation. Two-dimensional echocardiography was used to measure pulmonary artery diameter and assess symmetry after two types of systemic-pulmonary artery shunts: modified right Blalock-Taussig shunt (14 patients) and central shunt (from underside of aortic arch gusset to pulmonary artery confluence) (14 patients). Age, weight, preoperative diameter of right and left pulmonary arteries (proximal, middle, and distal segments), and mean interval between preoperative and postoperative echocardiographic studies (20.2 +/- 4.4 days in the Blalock shunt group; 19.1 +/- 6.8 days in the central shunt group) were similar. Early postoperatively, patients with a Blalock shunt showed a significant decrease in the diameter of all pulmonary artery segments except the distal right pulmonary artery. The diameters tapered from distal right to distal left pulmonary artery in this group. Patients with the central shunt had a significant decrease in the diameter of all pulmonary artery segments. There were no significant differences when cross comparisons were made of the various pulmonary arterial segments in patients after a central shunt. Similar findings persisted in 19 patients from both groups who had a late postoperative echocardiogram (mean interval between studies = 271 days in the group of 10 patients with Blalock shunt and 167 days in the group of nine patients with a central shunt). In conclusion, the central shunt preserves pulmonary artery symmetry, which may be important in candidates for the Fontan operation in infancy.     

Accessory mitral valve associated with aortic regurgitation in an elderly patient: report of a case

We encountered a 75-year-old man who complained of exertional dyspnea. An echocardiographic examination showed aortic regurgitation and a tumor in the left ventricular outflow tract. Under complete extracorporeal circulation, we surgically made an incision of the ascending aorta with a slight thickening of the aortic valve and an enlarged annulus. After excising the aortic valve, an examination of the subvalvular region revealed mitral valve-like tissue extending from the annular region of the right coronary cusp to the ventricular septum, while the chordae tendinae was attached to the septum. This issue was excised, and the aortic valve was replaced with a 27-mm SJM valve. The postoperative course was uneventful, and the patient was discharged in good condition on postoperative day 30. An accessory mitral valve is extremely rare. Since this indication for surgical treatment is associated with congenital heart disease or a left ventricular outflow tract obstruction, most patients are young. Our patient had no associated cardiac anomalies and no pressure gradient attributable to a left ventricular outflow tract obstruction. This accessory mitral valve was discovered during aortic valve replacement surgery. To our knowledge, our patient is the oldest reported with an accessory mitral valve to have undergone a surgical resection.     

Comparison of intraoperative nitroprusside unloading in mitral and aortic regurgitation.

To compare the hemodynamic effect of vasodilator therapy on different regurgitant lesions, we infused sodium nitroprusside intraooperatively in 12 patients with mitral regurgitation and 15 with aortic regurgitation. During the critical period preceding establishment of cardiopulmonary bypass, both groups had developed intense vasoconstriction and cardiac decompensation. All demonstrated improved cardiac function with vasodilator therapy; however, the degree of improvement with nitroprusside differed in the two groups. Stroke volume increased 10 ml. per beat per meter squared in those patients with aortic regurgitation and only 6 ml. per beat per meter squared in those with mitral regurgitation (p less than 0.05). The percent increase in stoke volume induced by nitroprusside was inversely correlated to the preoperative left ventricular ejection fraction (r = 0.44, p less than 0.02). Patients with aortic regurgitation had lower preoperative left ventricular ejection fractions than those with mitral regurgitation (0.53 versus 0.63, p less than 0.02). Therefore, we conclude that patients with aortic regurgitation derived greater intraoperative hemodynamic benefit from unloading with nitroprusside, because they came to surgery with greater impairment of left ventricular contractility. Although nitroprusside improved cardiac function in both groups, only the patients with aortic regurgitation achieved normal pulmonary artery pressure (17 torr) and pulmonary vascular resistance (2.1 units) as a result of unloading. Those with mitral regurgitation continued to have pulmonary hypertension (28 torr) and increased pulmonary vascular resistance (3.9 units) despite vasodilator therapy. Thus the data suggest that patients with mitral regurgitation derived less hemodynamic benefit from intraoperative nitroprusside therapy because they were also limited by right ventricular dysfunction and a less responsive pulmonary vasculature.     

Ventricular assist device in patients with prosthetic heart valves

Ventricular assist device (VAD) support inpatients with a prosthetic heart valve had previously been considered a relative contraindication due to an increased risk of thromboembolic complications. We report our clinical experience of VAD implantation in patients with prosthetic heart valves, including both mechanical and bioprosthetic valves. The clinical records of 133 consecutive patients who underwent VAD implantation at a single institution from January 2002 through June 2009 were retrospectively reviewed. Six of these patients had a prosthetic valve in place at the time of device implantation. Patient demographics,operative characteristics, and postoperative complications were reviewed.Of the six patients,four were male.The mean age was 57.8 years (range 35–66 years). The various prosthetic cardiac valves included a mechanical aortic valve (n = 2), a bioprosthetic aortic valve (n = 3), and a mechanical mitral valve (n = 1).The indications for VAD support included bridge to transplantation (n = 2), bridge to recovery (n = 1), and postcardiotomy ventricular failure(n = 3). Three patients underwent left ventricular assist device placement and three received a right ventricular assist device. Postoperatively, standard anticoagulation management began with a heparin infusion (if possible)followed by oral anticoagulation.The 30-day mortality was50% (3/6). The mean duration of support among survivors was 194.3 days (range 7–369 days) compared with 16.0 days(range 4–29 days) for nonsurvivors. Of the three survivors,two were successfully bridged to heart transplantation and one recovered native ventricular function.Among the three nonsurvivors,acute renal failure developed in each case, and two developed heparin-induced thrombocytopenia. This study suggests that VAD placement in patients with a prosthethic heart valve, either mechanical or bioprosthetic,appears to be a reasonable option.     

A case report: Rastelli operation for double outlet right ventricle associated with a chordae insertion to the infundibular septum]

A successful Rastelli operation for double outlet right ventricle (DORV) with a chordae insertion of the tricuspid valve to the infundibular septum was reported. A patient was a 6-year-old boy and the diagnosis was DORV, d-malposition of the aorta and pulmonary stenosis. The infundibular septum was not resected but mobilized with two incision, one anterior and vertical, and other one subaortic. This procedure allowed the construction of the tunnel similar to the closure of a large, subarterial VSD and of the straight unobstractive left outflow tract. The postoperative echocardiographic and angiographic examination revealed neither the pressure gradient in the left ventricular outflow tract nor the tricuspid regurgitation.     

Intermittent atrial level right-to-left shunt with temporary hypoxemia in a patient during support with a left ventricular assist device

We report a 56-year-old male patient developing hypoxemia after surgical replacement of infected valves of a left ventricular assist device (LVAD, Novacor) which had supported him during the previous 15 months. Contrast transesophageal echocardiography (TEE) revealed an atrial septal defect with intermittent right-to-left shunt across a patent foramen ovale. We postulate that the shunt detected in this patient occurred as a consequence of reduced pulmonary vascular compliance due to positive end-expiratory pressure (PEEP) and an increase of mean intrathoracic pressure. Furthermore, we hypothesize that synchronized LVAD operation exacerbates any potential right-to-left shunt due to the profound left ventricular unloading which occurs during LVAD support. In this first report of a right-to-left shunt from a previously unrecognized patent foramen ovale in a Novacor patient, the subsequent transient hypoxemia could be managed by avoiding PEEP of more than 3 mmHg, and mean airway pressure of more than 11 mmHg and by careful volume replacement in order to prevent the pump from completely emptying the left ventricle (LV) and the left atrium (LA). Thus, prior to every LVAD implantation a transesophageal contrast echocardiography with Valsalva maneuver should be performed to identify intracardiac right-to-left shunt.     

Repair of cor triatriatum associated with partially unroofed coronary sinus.

A young patient with cor triatriatum, secundum atrial septal defect, persistent left superior vena cava, partially unroofed coronary sinus, and moderate tricuspid regurgitation was documented to have both a left-to-right shunt from the common pulmonary venous chamber to the right atrium and a right-to-left shunt from the partially unroofed coronary sinus to the left atrium. Resection of the membrane dividing the left atrium, closure of the atrial septal defect and the partially unroofed coronary sinus with pericardial patches, and a tricuspid annuloplasty resulted in an excellent hemodynamic result.     

Biventricular pacing in a patient with severe congestive heart failure

We report a case of dilated cardiomyopathy with severe congestive heart failure (ejection fraction: 19%) and complete left bundle branch block (QRS duration: 240 ms) 13 years after aortic valve replacement. Permanent biventricular pacing was implanted by inserting a left ventricular lead thorough a small left thoracotomy following intravenous insertion of right atrial and ventricular endocardial leads. Biventricular pacing increased hemodynamic parameters such as blood pressure, cardiac output and decreased mitral regurgitation. Symptoms and exercise tolerance improved dramatically. Left ventricular epicardial lead insertion via a small thoracotomy is thus useful in selected patients.