Gengo Sunagawa

Coronary artery bypass surgery is superior to percutaneous coronary intervention with drug-eluting stents for patients with chronic renal failure on hemodialysis.

BACKGROUND Improvements in the results of percutaneous coronary intervention (PCI) with drug-eluting stents (DES) have been extending their use in patients with all forms of coronary artery disease. The purpose of this study was to compare the midterm clinical results of coronary artery bypass surgery (CABG) and PCI with DES in patients with chronic renal failure on hemodialysis. METHODS From January 2002 to December 2006, 29 patients underwent CABG, and 75 patients underwent PCI with DES. For CABG, 24 patients had off-pump surgery. The mean follow-up was 32.0 +/- 22.0 months for CABG and 23.5 +/- 14.8 months for PCI. Survival, cardiac death, major adverse cardiac events (cardiac death, myocardial infarction, revascularization), and target lesion revascularization were analyzed using the Kaplan-Meier method. RESULTS Preoperative characteristics and risk factors were compatible between the groups except for the European System for Cardiac Operative Risk Evaluation (7.3 +/- 2.7 for CABG and 5.0 +/- 2.4 for PCI, p < 0.0001) and the presence of a left main trunk lesion (53.3% for CABG and 18.7% for PCI). Thirty-day mortality was 3.3% for CABG and 4.0% for PCI. The 2-year survival rate was 84.0% for CABG and 67.6% for PCI (p = 0.0271). The cardiac death-free curve at 2 years was 100% for CABG and 84.1% for PCI (p = 0.0122). The major adverse cardiac events-free rate at 2 years was 75.8% for CABG and 31.5% for PCI (p < 0.0001). During the follow-up period, there were 6 late deaths in the CABG group and 27 late deaths (including 6 sudden deaths) in the PCI group. CONCLUSIONS Coronary artery bypass grafting was superior to PCI with DES in patients with chronic renal failure on hemodialysis in terms of long-term outcomes for cardiac death, major adverse cardiac events, and target lesion revascularization. The DES carried a higher risk for sudden death, which might be associated with stent thrombosis.

Limitations to Chronic Right Ventricular Assist Device Support

Failure of the right ventricle represents a significant clinical problem and may have different causes, with rates varying between 5% and 50% in patients supported by a left ventricular assist device (LVAD). However, treatment options and device development for right ventricular failure (RVF) have significantly lagged behind those for LVADs. Newer technologies designed or adapted for RV support are needed to provide adequate long-term circulatory support. In this review, we discuss (1) the significance of RVF and its physiologic implications, (2) device constraints affecting treatment options for RVF, and (3) implantable VADs potentially available for RV support.

Median Sternotomy or Right Thoracotomy Techniques for Total Artificial Heart Implantation in Calves

The choice of optimal operative access technique for mechanical circulatory support device implantation ensures successful postoperative outcomes. In this study, we retrospectively evaluated the median sternotomy and lateral thoracotomy incisions for placement of the Cleveland Clinic continuous-flow total artificial heart (CFTAH) in a bovine model. The CFTAH was implanted in 17 calves (Jersey calves; weight range, 77.0-93.9 kg) through a median sternotomy (n = 9) or right thoracotomy (n = 8) for elective chronic implantation periods of 14, 30, or 90 days. Similar preoperative preparation, surgical techniques, and postoperative care were employed. Implantation of the CFTAH was successfully performed in all cases. Both methods provided excellent surgical field visualization. After device connection, however, the median sternotomy approach provided better visualization of the anastomoses and surgical lines for hemostasis confirmation and repair due to easier device displacement, which is severely limited following right thoracotomy. All four animals sacrificed after completion of the planned durations (up to 90 days) were operated through full median sternotomy. Our data demonstrate that both approaches provide excellent initial field visualization. Full median sternotomy provides larger viewing angles at the anastomotic suture line after device connection to inflow and outflow ports.

Human Fitting Studies of Cleveland Clinic Continuous-Flow Total Artificial Heart.

Implantation of mechanical circulatory support devices is challenging, especially in patients with a small chest cavity. We evaluated how well the Cleveland Clinic continuous-flow total artificial heart (CFTAH) fit the anatomy of patients about to receive a heart transplant. A mock pump model of the CFTAH was rapid-prototyped using biocompatible materials. The model was brought to the operative table, and the direction, length, and angulation of the inflow/outflow ports and outflow conduits were evaluated after the recipient’s ventricles had been resected. Thoracic cavity measurements were based on preoperative computed tomographic data. The CFTAH fit well in all five patients (height, 170 ± 9 cm; weight, 75 ± 24 kg). Body surface area was 1.9 ± 0.3 m2 (range, 1.6–2.1 m2). The required inflow and outflow port orientation of both the left and right housings appeared consistent with the current version of the CFTAH implanted in calves. The left outflow conduit remained straight, but the right outflow direction necessitated a 73 ± 22 degree angulation to prevent potential kinking when crossing over the connected left outflow. These data support the fact that our design achieves the proper anatomical relationship of the CFTAH to a patient’s native vessels.

Mechanism of Self-Regulation and In Vivo Performance of the Cleveland Clinic Continuous-Flow Total Artificial Heart

Cleveland Clinics continuous-flow total artificial heart (CFTAH) provides systemic and pulmonary circulations using one assembly (one motor, two impellers). The right pump hydraulic output to the pulmonary circulation is self-regulated by the rotating assemblys passive axial movement in response to atrial differential pressure to balance itself to the left pump output. This combination of features integrates a biocompatible, pressure-balancing regulator with a double-ended pump. The CFTAH requires no flow or pressure sensors. The only control parameter is pump speed, modulated at programmable rates (60-120 beats/min) and amplitudes (0 to ±25%) to provide flow pulses. In bench studies, passive self-regulation (range: -5 mm Hg ≤ [left atrial pressure - right atrial pressure] ≤ 10 mm Hg) was demonstrated over a systemic/vascular resistance ratio range of 2.0-20 and a flow range of 3-9 L/min. Performance of the most recent pump configuration was demonstrated in chronic studies, including three consecutive long-term experiments (30, 90, and 90 days). These experiments were performed at a constant postoperative mean speed with a ±15% speed modulation, demonstrating a totally self-regulating mode of operation, from 3 days after implant to explant, despite a weight gain of up to 40%. The mechanism of self-regulation functioned properly, continuously throughout the chronic in vivo experiments, demonstrating the performance goals.

The clinical challenge to reduce the postoperative residual shunt in surgical repair of postinfarction ventricular septal perforation

Postinfarction ventricular septal perforation (VSP) remains a surgical challenge. The present study describes the use of an interrupted suture technique with the goal of reducing the incidence of postoperative residual shunt. Thirty-four consecutive cases of patients who underwent Davids procedure for VSP between 1996 and 2008 were reviewed. A running suture technique was used to close the ruptured septum (C-group: 14 patients) prior to 2002, while the interrupted suture technique (I-group: 20 patients) was used after that point. The overall 30-day mortality was 26.5%, and the mortality rate was not different when comparing the two groups. Postoperative residual shunt was present in five patients (36%) in the C-group and in two patients (10%) in the I-group. In conclusion, use of the interrupted suture technique resulted in a lower incidence of postoperative residual shunt rate. However, the mortality associated with surgical repair of VSP remains high.

Anatomy of the bovine ascending aorta and brachiocephalic artery found unfavorable for total artificial heart implant

The biocompatibility assessment of the Cleveland Clinic continuous-flow total artificial heart is an important part of the device developmental program. Surgical and postoperative management are key factors in achieving optimal outcomes. However, the presence of vascular anatomical abnormalities in experimental animal models is often unpredictable and may worsen the expected outcomes. We report a technical impediment encountered during total artificial heart implantation complicated by unfavorable bovine anatomy of the ascending aorta and brachiocephalic arterial trunk.

Post-explant visualization of thrombi in outflow grafts and their junction to a continuous-flow total artificial heart using a high-definition miniaturized camera

Post-explant evaluation of the continuous-flow total artificial heart in preclinical studies can be extremely challenging because of the device’s unique architecture. Determining the exact location of tissue regeneration, neointima formation, and thrombus is particularly important. In this report, we describe our first successful experience with visualizing the Cleveland Clinic continuous-flow total artificial heart using a custom-made high-definition miniature camera.

Initial in vitro testing of a paediatric continuous-flow total artificial heart

OBJECTIVES Mechanical circulatory support has become standard therapy for adult patients with end-stage heart failure; however, in paediatric patients with congenital heart disease, the options for chronic mechanical circulatory support are limited to paracorporeal devices or off-label use of devices intended for implantation in adults. Congenital heart disease and cardiomyopathy often involve both the left and right ventricles; in such cases, heart transplantation, a biventricular assist device or a total artificial heart is needed to adequately sustain both pulmonary and systemic circulations. We aimed to evaluate the in vitro performance of the initial prototype of our paediatric continuous-flow total artificial heart. METHODS The paediatric continuous-flow total artificial heart pump was downsized from the adult continuous-flow total artificial heart configuration by a scale factor of 0.70 (1/3 of total volume) to enable implantation in infants. System performance of this prototype was evaluated using the continuous-flow total artificial heart mock loop set to mimic paediatric circulation. We generated maps of pump performance and atrial pressure differences over a wide range of systemic vascular resistance/pulmonary vascular resistance and pump speeds. RESULTS Performance data indicated left pump flow range of 0.4-4.7 l/min at 100 mmHg delta pressure. The left/right atrial pressure difference was maintained within ±5 mmHg with systemic vascular resistance/pulmonary vascular resistance ratios between 1.4 and 35, with/without pump speed modulation, verifying expected passive self-regulation of atrial pressure balance. CONCLUSIONS The paediatric continuous-flow total artificial heart prototype met design requirements for self-regulation and performance; in vivo pump performance studies are ongoing.

Early in vivo experience with the pediatric continuous-flow total artificial heart

BACKGROUND Heart transplantation in infants and children is an accepted therapy for end-stage heart failure, but donor organ availability is low and always uncertain. Mechanical circulatory support is another standard option, but there is a lack of intracorporeal devices due to size and functional range. The purpose of this study was to evaluate the in vivo performance of our initial prototype of a pediatric continuous-flow total artificial heart (P-CFTAH), comprising a dual pump with one motor and one rotating assembly, supported by a hydrodynamic bearing. METHODS In acute studies, the P-CFTAH was implanted in 4 lambs (average weight: 28.7 ± 2.3 kg) via a median sternotomy under cardiopulmonary bypass. Pulmonary and systemic pump performance parameters were recorded. RESULTS The experiments showed good anatomical fit and easy implantation, with an average aortic cross-clamp time of 98 ± 18 minutes. Baseline hemodynamics were stable in all 4 animals (pump speed: 3.4 ± 0.2 krpm; pump flow: 2.1 ± 0.9 liters/min; power: 3.0 ± 0.8 W; arterial pressure: 68 ± 10 mm Hg; left and right atrial pressures: 6 ± 1 mm Hg, for both). Any differences between left and right atrial pressures were maintained within the intended limit of ±5 mm Hg over a wide range of ratios of systemic-to-pulmonary vascular resistance (0.7 to 12), with and without pump-speed modulation. Pump-speed modulation was successfully performed to create arterial pulsation. CONCLUSION This initial P-CFTAH prototype met the proposed requirements for self-regulation, performance, and pulse modulation.