Rapidly Progressed Distal Arch Aneurysm with Distal Open Stent Graft-Induced New Entry Caused by "Spring-Back" Force

The J Graft Open Stent Graft (JOSG) is used for the frozen elephant trunk procedure in Japan. We report a 70-year-old male who developed a rapidly progressing distal arch aneurysm caused by a distal stent graft-induced new entry (DSINE) 7 months after the procedure. The JOSG was originally implanted at the curved part of the distal arch. It created its initial DSINE on the greater curve and rapidly "sprang" back in 2 months. Urgent thoracic endovascular aortic repair fixed this serious complication. We should remember such rapid progression of DSINE by JOSG and treat its initial sign earlier.

Preemptive angioplasty for contralateral leg stenosis following EXCLUDER Iliac Branch Endoprosthesis implantation

The GORE EXCLUDER Iliac Branch Endoprosthesis (IBE) device is designed to seal off a common iliac artery (CIA) aneurysm, preserving the internal iliac artery during endovascular aortic repair. We report the case of an 84-year-old man with isolated saccular right CIA aneurysm (35 mm) and a relatively small terminal aorta (24 mm). The IBE device was successfully placed, and intraoperative angiography revealed no leakage or delay. However, postoperative computed tomography revealed marked compression of the contralateral leg by a bridging component. Although his ankle-brachial index was preserved, its acute occlusion was judged highly possible; we decided to perform preemptive angioplasty. The angiography revealed the stenosis only in the left anterior oblique view, and angioplasty was uneventfully performed. The leg was successfully patent at 1-year follow-up. When compression by IBE and bridging component in the terminal aorta is expected, caution should be preserved at intraoperative angiography following the device deployment.

Risk Factors for Atrial Fibrillation Recurrence After Cox Maze IV Performed Without Pre-exclusion

BACKGROUND

New guidelines from The Society of Thoracic Surgeons recommend adding surgical ablation as a concomitant procedure for class I indications. We performed the maze procedure for all patients who experienced atrial fibrillation (AF) before cardiac surgery, without surgeon pre-exclusion.

METHODS

We retrospectively analyzed 83 patients, aged 71 ± 11 years (22% >80 years), who underwent Cox maze IV for persistent AF between 2014 and 2017. The mean AF duration (AFD) was 6.9 ± 8.6 years and European System for Cardiac Operative Risk Evaluation II was 7.2 ± 6.8.

RESULTS

The 30-day mortality was 2.4%. During follow-up (mean, 675 days), the 1-, 2-, and 3-year survival rates were 92%, 86%, and 82%, respectively. No strokes were observed despite a mean CHA₂DS₂-VAS_C (Congestive heart failure, Hypertension, Age [≥65 = 1 point, ≥75 = 2 points], Diabetes, and Stroke/transient ischemic attack [2 points], vascular disease, Sex [female = 1 point]) score of 4.1 (expected stroke rate, 4%/y). Twelve patients required a new pacemaker; 56 of 73 survivors (77%) remained AF free. Multivariate logistic regression identified preoperative AFD, f wave size, and mean heart rate per Holter as important risk factors for AF recurrence, with AFD as the most important: 98% of patients with AFD less than 5 years remained AF free. Although the AF-free rate with the AFD of 5 or more years was only 55%, their symptoms improved without heart failure readmission. Concomitant atrial plication was performed more frequently in the group with AFD for 5 or more years, with greater atrial volume reduction and appreciable increases in stroke volume.

CONCLUSIONS

The Cox maze IV procedure performed without pre-exclusion showed reasonable survival rates. Although AF recurred in patients with longer AFD, they fared well with substantial increases in stroke volume. Concomitant atrial volume reduction may have contributed to these additional benefits.

Successful Repair of Regurgitant Pentacuspid Pulmonary Valve Combined With Pulmonary Artery Aneurysm

Pentacuspid pulmonary valve is an extremely rare congenital anomaly. A 71-year-old woman presented with dyspnea on exertion. The preoperative examination showed a large pulmonary artery aneurysm with severe pulmonary regurgitation. The pentacuspid pulmonary valve was an intraoperative finding with four equivalent leaflets and one hypoplastic leaflet. The valve was successfully repaired by use of a bicuspidization technique combined with annuloplasty, and pulmonary artery reduction was performed. Postoperatively, the patient remained asymptomatic with trivial pulmonary regurgitation 1 year later. To our knowledge, this is the first report of a pentacuspid pulmonary valve repair.

Rigorous patient-prosthesis matching of Perimount Magna aortic bioprosthesis

Background

Severe patient-prosthesis mismatch, defined as effective orifice area index ≤0.65 cm2 m−2, has demonstrated poor long-term survival after aortic valve replacement. Reported rates of severe mismatch involving the Perimount Magna aortic bioprosthesis range from 4% to 20% in patients with a small annulus.

Methods

Between June 2008 and August 2011, 251 patients (mean age 70.5 ± 10.2 years; mean body surface area 1.55 ± 0.19 m2) underwent aortic valve replacement with a Perimount Magna bioprosthesis, with or without concomitant procedures. We performed our procedure with rigorous patient-prosthesis matching to implant a valve appropriately sized to each patient, and carried out annular enlargement when a 19-mm valve did not fit. The bioprosthetic performance was evaluated by transthoracic echocardiography predischarge and at 1 and 2 years after surgery.

Results

Overall hospital mortality was 1.6%. Only 5 (2.0%) patients required annular enlargement. The mean follow-up period was 19.1 ± 10.7 months with a 98.4% completion rate. Predischarge data showed a mean effective orifice area index of 1.21 ± 0.20 cm2 m−2. Moderate mismatch, defined as effective orifice area index ≤0.85 cm2 m−2, developed in 4 (1.6%) patients. None developed severe mismatch. Data at 1 and 2 years showed only two cases of moderate mismatch; neither was severe.

Conclusions

Rigorous patient-prosthesis matching maximized the performance of the Perimount Magna, and no severe mismatch resulted in this Japanese population of aortic valve replacement patients.

Successful bicuspid aortic valve repair using external aortic annuloplasty

A 33-year-old man presented with severe aortic insufficiency due to a prolapsed bicuspid aortic valve. The ventriculoaortic junction was dilated to 29 mm without root dilatation, and external ring annuloplasty was performed using a Gelweave (Terumo, Tokyo, Japan) graft to reduce the size to 22 mm. The leaflets were repaired by dividing and suturing a raphe between the right and left cusps. This combination provided adequate coaptation depth (8 mm) and showed excellent results, with trivial aortic insufficiency. This approach is suitable for repair of a bicuspid aortic valve with a dilated ventriculoaortic junction without root dilatation.

Device for simultaneous positron emission tomography, laser speckle imaging and RGB reflectometry: validation and application to cortical spreading depression and brain ischemia in rats

Brain function critically relies on the supply with energy substrates (oxygen and glucose) via blood flow. Alterations in energy demand as during neuronal activation induce dynamic changes in substrate fluxes and blood flow. To study the complex system that regulates cerebral metabolism requires the combination of methods for the simultaneous assessment of multiple parameters. We developed a multimodal imaging device to combine positron emission tomography (PET) with laser speckle imaging (LSI) and RGB reflectometry (RGBR). Depending on the radiotracer, PET provides 3-dimensional quantitative information of specific molecular processes, while LSI and RGBR measure cerebral blood flow (CBF) and hemoglobin oxygenation at high temporal and spatial resolution. We first tested the functional capability of each modality within our system and showed that interference between the modalities is negligible. We then cross-calibrated the system by simultaneously measuring absolute CBF using (15)O-H2O PET (CBF(PET)) and the inverse correlation time (ICT), the LSI surrogate for CBF. ICT and CBF(PET) correlated in multiple measurements in individuals as well as across different animals (R(2)=0.87, n=44 measurements) indicating that ICT can be used for absolute quantitative assessment of CBF. To demonstrate the potential of the combined system, we applied it to cortical spreading depression (CSD), a wave of transient cellular depolarization that served here as a model system for neurovascular and neurometabolic coupling. We analyzed time courses of hemoglobin oxygenation and CBF alterations coupled to CSD, and simultaneously measured regional uptake of (18)F-2-fluoro-2-deoxy-D-glucose ((18)F-FDG) used as a radiotracer for regional glucose metabolism, in response to a single CSD and to a cluster of CSD waves. With this unique combination, we characterized the changes in cerebral metabolic rate of oxygen (CMRO2) in real-time and showed a correlation between (18)F-FDG uptake and the number of CSD waves that passed the local tissue. Finally, we examined CSD spontaneously occurring during focal ischemia also referred to as peri-infarct depolarization (PID). In the vicinity of the ischemic territory, we observed PIDs that were characterized by reduced CMRO2 and increased oxygen extraction fraction (OEF), indicating a limitation of oxygen supply. Simultaneously measured PET showed an increased (18)F-FDG uptake in these regions. Our combined system proved to be a novel tool for the simultaneous study of dynamic spatiotemporal alterations of cortical blood flow, oxygen metabolism and glucose consumption under normal and pathologic conditions.

Off-pump suture repair of left ventricular rupture utilizing TachoComb® sheet: a case report and literature review

A 70-year-old woman was admitted to our institution with acute myocardial infarction. Coronary angiography demonstrated total occlusion of the left anterior descending artery, which was successfully revascularized. Four days later, the patient suddenly went into shock. The subsequent emergency operation revealed a blowout rupture of the left ventricular free wall. Several TachoComb^® (CSL Behring, Tokyo, Japan) sheets were applied to control bleeding and avoid the need for a cardiopulmonary bypass. Horizontal mattress sutures were used in combination with a pair of Teflon felt strips for reinforcement. The combination of TachoComb^® sheets and sutures is a novel hybrid method and an effective life-saving procedure for the treatment of left ventricular blowout ruptures. This approach avoids the need for a cardiopulmonary bypass. Sutureless repairs with TachoComb^® sheet achieve rapid hemostasis without the need for cardiopulmonary bypass. This stabilizes patient hemodynamics immediately and preserves the fragile myocardium. This allows emergency room physicians to open the chest and apply the TachoComb^® sheet to stabilize the patient before the cardiac surgeons arrive at the operating room. This technique will be very useful in emergency situations.

Simultaneous imaging of cortical blood flow and haemoglobin concentration with LASCA and RGB reflectometry

We demonstrate a system for the simultaneous imaging of cortical blood flow and haemoglobin oxygenation by laser speckle contrast analysis (LASCA) and RGB reflectometry. The sensitivity of the system was tested by observing changes of haemoglobin oxygenation and blood flow in rats in response to ischaemic stroke, hypercapnia, hyperoxia, hypoxia, cortical spreading depression and cortical activation following forepaw stimulation.

Successful aortic reimplantation in a three-year-old child with Marfan syndrome

Aortic root dilatation is rare in children, and is often secondary to Marfan syndrome (MFS). We experienced a case of a three-year-old boy (92 cm, 12 kg) with MFS presenting with progressive dilatation of aortic root. We electively performed a valve-sparing aortic root replacement using a 24-mm Gelweave Valsalva graft. Although the patient required a mitral valve repair due to infective endocarditis postoperatively, the recovery from the second surgery was uneventful. This case is one of the youngest children of valve-sparing aortic root replacement in the literature.

Combination of continuous irrigation and vacuum-assisted closure is effective for mediastinitis after cardiac surgery in small children

There is still no consensus on the optimal management to treat pediatric mediastinitis. We assessed the efficacy of continuous irrigation and vacuum-assisted closure (VAC) for mediastinitis in children. This study retrospectively reviewed 20 patients aged <5 years with mediastinitis from December 2002 to December 2009. The median age at the onset was 12 months (0.6-60 months), and the median body weight was 6.9 kg (3.1-15.3 kg). Continuous irrigation was applied for extensive mediastinitis or unstable hemodynamic cases and VAC for localized or ineffective cases after continuous irrigation. A 2-4-week course of intravenous antibiotics was administered after sternal closure. Continuous irrigation was initially applied in 19 patients and VAC in one patient. VAC was employed in six patients because of recurrent or prolonged mediastinitis after continuous irrigation. All patients underwent direct sternal closure without any flap. The median duration of the hospital stay was 49.5 days (15-158 days). Although two patients died of low cardiac output, 18 children survived and had no recurrence after the discharge during a median follow-up of 14 months (1-81 months). The combination of continuous irrigation and VAC is, therefore, considered to be a safe and effective option to minimize the morbidity and mortality in pediatric mediastinitis.

The impact of the length between the top of the interventricular septum and the aortic valve on the indications for a biventricular repair in patients with a transposition of the great arteries or a double outlet right ventricle

The purpose of this study was to establish a useful cut-off level for performing an original Rastelli-type operation in patients with transposition of the great arteries (TGA)/ventricular septal defect (VSD) or double outlet right ventricle (DORV). A total of 43 patients with TGA/VSD or DORV who underwent an original Rastelli-type operation in this institute between March 1993 and January 2009 were reviewed retrospectively. These patients were divided into two groups using the length between the top of the interventricular septum and the aortic valve (IVS-AV length); Group A; IVS-AV length <80% of normal left ventricular end-diastolic diameter (LVDd). Group B; IVS-AV length > or =80% of normal LVDd. Group A had a significantly better survival than Group B (100% vs. 56%, P=0.001). The cardiac event-free survival were 89.1% at 7.2 years in Group A and 26.3% at 8.4 years in Group B (P<0.0001). The Group B had a higher incidence of left ventricular outflow tract obstruction (LVOTO; 3% vs. 33%, P=0.02). The IVS-AV length was found to be a significant risk factor for mortality and LVOTO. The IVS-AV length should, therefore, be taken into consideration when selecting the optimal surgical procedures for these patients.

Impact of mitral valve annuloplasty combined with revascularization in patients with functional ischemic mitral regurgitation

OBJECTIVES

The aim of this work was to determine whether mitral valve (MV) annuloplasty benefits patients with moderate/severe (3+/4+) functional ischemic mitral regurgitation (MR) who undergo coronary artery bypass grafting (CABG).

BACKGROUND

Mitral regurgitation is a strong predictor of poor outcomes in patients with ischemic cardiomyopathy; whether correcting it at the time of CABG improves outcomes is less certain.

METHODS

From 1991 to 2003, 390 patients with 3+/4+ ischemic MR had CABG with (n = 290) or without (n = 100) MV annuloplasty. Groups were propensity-matched using demographics, extent of coronary disease, regional wall motion, and quantitative electrocardiography. Survival, echocardiographic severity of MR, and New York Heart Association (NYHA) functional class were compared.

RESULTS

One-, 5-, and 10-year survival was 88%, 75%, and 47% after CABG alone and 92%, 74%, and 39% after CABG + MV annuloplasty (p = 0.6). Mortality was increased in patients with severe lateral wall motion abnormalities (p = 0.05), ST-segment elevation in lateral leads (p < 0.004), and higher QRS voltage sum (p < 0.0001). Patients undergoing CABG alone were more likely to have 3+/4+ postoperative MR than those undergoing CABG + MV annuloplasty (48% vs. 12% at 1 year, p < 0.0001). The NYHA functional class substantially improved in both groups (p < 0.001) and remained improved; at 5 years, 23% of patients having CABG + mitral annuloplasty and 25% having CABG alone were in NYHA functional class III/IV.

CONCLUSIONS

Although CABG + MV annuloplasty reduces postoperative MR and improves early symptoms compared with CABG alone, it does not improve long-term functional status or survival in patients with severe functional ischemic MR. The MV annuloplasty in this setting, without addressing fundamental ventricular pathology, is insufficient to improve long-term clinical outcomes.

Efficacy of an endothelin-A receptor antagonist in heart transplantation from asphyxiated canine non-heart-beating donors

OBJECTIVE

Hypoxic perfusion before arrest, an indeterminate period of warm ischemia, and subsequent reperfusion are major causes of cardiac allograft dysfunction in non-heart-beating donors (NHBDs). The present study was undertaken to elucidate the cardioprotective effects of ET(A) receptor antagonist FR139317 for hearts obtained from asphyxiated NHBDs in a canine transplantation model.

METHODS

Hypoxic cardiac arrest was induced in 17 donor dogs. FR139317 (10 mg/kg) was given to 7 of the dogs over a period of 10 min before disconnecting the ventilator. The hearts were preserved with FR 139317-supplemented cardioplegic solution (FR group). The remaining 10 did not receive FR 139317 at any time during the experiment (control group). Orthotopic transplantation was performed after a mean myocardial ischemic time of 4h.

RESULTS

During the agonal period, the highest systolic pulmonary artery pressure in the FR group was lower than that in the control group (47 +/- 14 vs. 58 +/- 27 mmHg). All animals in the FR group were weaned from cardiopulmonary bypass, whereas only five of the controls were weaned, two of which were identified to have dominant right ventricular failure. After transplantation, recovery rates of the left ventricular end-systolic pressure-volume ratio (E(max)) and the maximum first derivative of pressure measured over time (max dP/dt) were not significantly different between the groups, but recovery rates of the cardiac index, left ventricular minimum dP/dt and exponential time constant of LV relaxation (tau) in the FR group were higher than those in the control group.

CONCLUSIONS

The ET(A) receptor antagonist FR 139317 reduced pressure overload on the right ventricle by decreasing the peak pulmonary artery pressure before donor arrest. Cardioprotective effects of this agent for heart transplantation from NHBDs are manifested by preserved diastolic properties of the left ventricle.

Giant Flow Reversal in Pulmonary Venous Flow as a Possible Mechanism for Asynchronous Pacing-induced Heart Failure

BACKGROUND

Mechanistic roles of the immediate increase in left atrial (LA) pressure in pacing-induced congestive heart failure have not been clearly understood. We evaluated the impact of asynchronous rapid ventricular pacing on LA hemodynamics in this model.

METHODS

Transthoracic and transesophageal echocardiography and hemodynamic assessment were performed in 23 healthy mongrel dogs. Data were acquired before and 5 minutes after initiation of rapid right ventricular pacing (200/min).

RESULTS

At 5 minutes after initiation of the pacing, giant pulmonary venous (PV) flow reversal (-76 cm/s) was observed in association with 1:1 ventriculoatrial conduction or complete atrioventricular dissociation. This giant PV flow reversal corresponded to an inappropriately timed atrial contraction, especially during systole. Cardiac output (3.21 vs 2.00 L/min, P < .001) was decreased corresponding to the decrease in the forward blood volumes as described by decrease in the Doppler left ventricular (LV) outflow (8.99 vs 4.73 cm, P < .0001), mitral inflow (6.89 vs 3.19 cm, P < .0001), and PV flow (14.15 vs 7.22 cm, P < .0001) velocity integrals. As a result, there was a marked elevation of the mean pulmonary capillary wedge (9.1 vs 17.1 mm Hg, P < .001) and LV end-diastolic (8.2 vs 17.4 mm Hg, P < .01) pressures leading to congestive heart failure.

CONCLUSIONS

The giant PV flow reversal seen during asynchronous rapid right ventricular pacing corresponds to an inappropriate atrial contraction, immediately elevates LA pressure, and may initially promote congestive heart failure. The increase in LV end-diastolic pressure associated with decreased LV ejection fraction caused decrease in the LV filling volume leading to further increase in the LA pressure. This sustained marked elevation in the LA pressure and LV end-diastolic pressure could contribute to the heart failure process.

Myocardial compliance was not altered after acute induction of atrial fibrillation in sheep

BACKGROUND

Although left ventricular (LV) contractility in atrial fibrillation (Af) is known to change in a beat-to-beat fashion, little is known about the changes in LV compliance in Af.

MATERIAL/METHODS

We experimentally induced tachycardic Af (average heart rate - 154 beats per minute) in 18 sheep. LV volume and pressure were simultaneously monitored using a conductance catheter. LV end-diastolic volume (V(ED)) and pressure (P(ED)) were plotted in a beat-to-beat fashion and fitted to the following exponential equation (P(ED)=gamma x e(b x V(ED))) in each animal. A random effects model was constructed to determine if the intercepts and slopes differ.

RESULTS

In all animals, those plots after the induction of Af fit quite well to the exponential function (r=0.834+/-0.184) by gating short preceding interval (RR1) beats. By simply taking the natural logarithm of both sides in the equation, the linear relationship (ln(P(ED)) =alpha+ betaxV(ED), where a = lng) was observed in all animals before (normal sinus rhythm, NSR) and after the induction of Af. Only two of 18 intercepts and four of 18 slopes deviate between NSR and Af. Most interestingly, the random effects model clearly detailed that the average animal had intercepts and slopes that were not discernibly different between NSR and Af.

CONCLUSIONS

Unlike LV contractility, myocardial compliance did not change after the acute induction of Af. These interesting results may give us insights into the understanding of the physiology in acute rapid Af.

Echocardiographic assessment of regional ventricular function after device-based change of left ventricular shape

We assessed the effects of implantation of Myosplint (Myocor, Maple Grove, Minn), a device that changes left ventricular (LV) cross-sectional shape from circular to bilobar, on regional LV function. A total of 10 open-chest dogs with tachycardia-induced cardiomyopathy were studied before and after Myosplint implantation. LV cross-sectional epicardial echocardiography at the papillary muscle level was performed along with acquisition of hemodynamic data. LV normalized thickening, fractional thickening, end-diastolic thickness, and end-diastolic curvatures were calculated for 10 LV segments. Myosplint implantation did not affect LV hemodynamics, but decreased average end-diastolic curvature (P <.0001) and increased its segmental heterogeneity (P <.0001). There was no change in average fractional thickening, whereas normalized thickening increased (P =.05). In contrast, segmental heterogeneity of both normalized and fractional thickening increased (P =.02 and P =.01, respectively). Structural modeling confirmed that Myosplint implantation increases regional stress heterogeneity and curvature heterogeneity. LV cross-sectional shape markedly affects regional LV performance.

Mitral valve replacement through right thoracotomy after previous coronary artery bypass grafting: the usefulness of brachial artery cannulation, perfused ventricular fibrillation with moderate hypothermia, and minimal dissection techniques

It has been reported by several authors that a right thoracotomy for mitral valve surgery can be useful after previous coronary aortery bypass grafting (CABG). A 76-year-old man with mitral valve regurgitation after previous CABG underwent mitral valve replacement with some modified techniques. Cardiopulmonary bypass was established with right brachial artery cannulation and right femoral venous cannulation with the aid of vacuum-assisted venous drainage. Ventricular fibrillation (VF) was induced by rapid pacing of the ventricle, and mitral valve replacement was performed under perfused VF with moderate hypothermia. The patient's postoperative course was uneventful. This method appears to be a safe and easy alternative mitral valve surgery for complicated cases of this type.

Total right ventricular exclusion improves left ventricular function in patients with end-stage congestive right ventricular failure

BACKGROUND

We developed a total right ventricular (RV) exclusion procedure for the treatment of isolated congestive RV failure. The objective of the present study was to elucidate the effects of a complete removal of RV volume overload (RVVO) on the surgically created single left ventricle (LV).

METHODS AND RESULTS

Three adults (2 arrhythmogenic RV dysplasia, 1 Ebstein) and 5 children (all Ebstein) in NYHA class IV underwent the procedure. The RV free wall was resected from the heart, and the tricuspid orifice was closed. Pulmonary blood supply was obtained by a cavopulmonary connection in 6 patients and a systemic-pulmonary shunt in 2. The LV function was evaluated by 2-dimensional echocardiography 1 month after the surgery. All patients are alive. The paradoxical movement of the interventricular septum and geometry of the LV expressed by its eccentricity (2.1 to 1.2, P<0.01) were normalized after the operation in all 8 patients. LV end-diastolic volumes (59% to 109% of normal value, P<0.01), indexed maximal left atrial area (6.5 to 10.5 cm2/m2, P<0.01), LV ejection fraction (27% to 62%, P<0.01), and cardiac index (2.1 to 3.3 L/min/m2, P<0.05) all significantly increased.

CONCLUSIONS

Removal of the RVVO by means of the total RV exclusion procedure provides effective volume loading, restores a cylindrical shape, and improves contractile function of the LV, thus leading to increased systemic output.

An evaluation of the use of new Doppler methods for detecting longitudinal function abnormalities in a pacing-induced heart failure model

BACKGROUND

Doppler tissue echocardiography and color M-mode Doppler flow propagation velocity have proven useful in evaluating cross-sections of patients with left ventricular (LV) dysfunction, but experience with serial changes is limited.

PURPOSE AND METHODS

We tested their use by evaluating the temporal changes of LV function in a pacing-induced congestive heart failure model. Rapid ventricular pacing was initiated and maintained in 20 dogs for 4 weeks. Echocardiography was performed at baseline and weekly during brief pacing cessation.

RESULTS

With rapid pacing, LV volume significantly increased and ejection fraction (57%-28%), stroke volume (37-18 mL), and mitral annulus systolic velocity (16.1-6.6 cm/s) by Doppler tissue echocardiography significantly decreased, with ejection fraction and mitral annulus systolic velocity closely correlated (r = 0.706, P <.0001). In contrast to the mitral inflow velocities, mitral annulus early diastolic velocity decreased steadily (12.3-7.3 cm/s) resulting in a dramatic decrease in mitral annulus early/late (1.22-0.57) diastolic velocity with no tendency toward pseudonormalization. The color M-mode Doppler flow propagation velocity also showed significant steady decrease (57-24 cm/s) throughout the pacing period. Multiple regression analysis chose mitral annulus systolic velocity (r = 0.895, P <.0001) and propagation velocity (r = 0.782, P <.0001) for the most important factor predicting LV systolic and diastolic function, respectively.

CONCLUSIONS

Doppler tissue echocardiography and color M-mode Doppler flow could evaluate the serial deterioration in LV dysfunction throughout the pacing period. These were more useful in quantifying progressive LV dysfunction than conventional ehocardiographic techniques, and were probably relatively independent of preload. These techniques could be suitable for longitudinal evaluation in addition to the cross-sectional study.

Determinants of the development of mitral regurgitation in pacing-induced heart failure

The pacing-induced heart failure model provides an opportunity to assess the structural and functional determinants of mitral regurgitation (MR) in dilated cardiomyopathy. This study aimed to evaluate MR to better understand the multitude of factors contributing to its development. Heart failure was induced by rapid ventricular pacing (230 beats/min) in 40 mongrel dogs. Left ventricular (LV) size and MR were evaluated echocardiographically. LV contractility was analyzed using a conductance catheter. MR increased to mild in 12 animals (regurgitant orifice area, 0.06+/-0.05 cm(2)), moderate in 15 (0.14+/-0.07 cm(2)), and severe in 13 (0.34+/-0.16 cm(2)). The grade of MR had an inverse relationships with E(max) (the slope of the end-systolic pressure-volume relationship, p<0.01) and dE/dt (the slope of the maximum rate of change of pressure-end-diastolic volume [V(ED)] relationship, p<0.01) and positive relationships with V(ED) and end-diastolic cross-sectional areas and lengths (p<0.05) by univariate analysis. The dE/dt had an independently significant (p<0.01) relationship by multivariable logistic regression. Many factors influence the development of MR and because of its similarity to the clinical situation, this model can be used to investigate MR and heart failure, as well as new surgical therapies.

In vitro controllability of the MagScrew total artificial heart system

The purpose of this study was to evaluate the in vitro responses to preload and afterload of our total artificial heart (TAH), the MagScrew TAH. The TAH consists of two blood pumps and a control logic, developed at the Cleveland Clinic, OH, and the MagScrew actuator and its electronic control system, developed by Foster-Miller Technologies, Inc., Albany, NY. Tests were performed on a mock circulatory loop, using water as a test fluid. Preload sensitivity of the Mag-Screw TAH demonstrated a Frank-Starling response to preload in automatic mode. A peak flow of 10 L/min was obtained, with a left atrial pressure of 13 mm Hg. The relationship between right atrial pressure and left atrial pressure was well balanced when tested with a left bronchial shunt flow of 5% and a range of pulmonary artery and aortic pressures. With respect to afterload response, the left pump showed a relatively low sensitivity, which allowed the pump to maintain perfusion over a wide range of aortic pressures. The right pump, on the other hand, was much more sensitive to pulmonary artery pressure, which provided a measure of protection against pulmonary congestion. The very effective physiologic response of the MagScrew TAH is believed to result from employment of a left master, alternating ejection control logic, high inherent sensitivity of the blood pumps to atrial pressure, a lower effective stroke volume for the right pump, and a scaling of right side motor ejection voltage to 80% of that used for the left side ejection.

Predictors of severe right ventricular failure after implantable left ventricular assist device insertion: analysis of 245 patients

BACKGROUND

Insertion of an implantable left ventricular assist device (LVAD) complicated by early right ventricular (RV) failure has a poor prognosis and is largely unpredictable. Prediction of RV failure after LVAD placement would lead to more precise patient selection and optimal device selection.

METHODS AND RESULTS

We reviewed data from 245 patients (mean age, 54+/-11 years; 85% male) with 189 HeartMate (77%) and 56 Novacor (23%) LVADs. Ischemic cardiomyopathy predominated (65%), and 29% had dilated cardiomyopathy. Overall, RV assist device (RVAD) support was required after LVAD insertion for 23 patients (9%). We compared clinical and hemodynamic parameters before LVAD insertion between RVAD (n=23) and No-RVAD patients (n=222) to determine preoperative risk factors for severe RV failure. By univariate analysis, female gender, small body surface area, nonischemic etiology, preoperative mechanical ventilation, circulatory support before LVAD insertion, low mean and diastolic pulmonary artery pressures (PAPs), low RV stroke work (RVSW), and low RVSW index (RVSWI) were significantly associated with RVAD use. Elevated PAP and pulmonary vascular resistance were not risk factors. Risk factors by multivariable logistic regression were preoperative circulatory support (odds ratio [OR], 5.3), female gender (OR, 4.5), and nonischemic etiology (OR, 3.3).

CONCLUSIONS

The need for circulatory support, female gender, and nonischemic etiology were the most significant predictors for RVAD use after LVAD insertion. Regarding hemodynamics, low PAP and low RVSWI, reflecting low RV contractility, were important parameters. This information may lead to better patient selection for isolated LVAD implantation.

Preload-adjusted maximal power: a novel index of left ventricular contractility in atrial fibrillation

BACKGROUND

Left ventricular contractility in atrial fibrillation is known to change in a beat to beat fashion, but there is no gold standard for contractility indices in atrial fibrillation, especially those measured non-invasively.

OBJECTIVE

To determine whether the non-invasive index of contractility "preload-adjusted PWR(max)" (maximal ventricular power divided by the square of end diastolic volume) can accurately measure left ventricular contractility in a beat to beat fashion in atrial fibrillation.

METHODS

Atrial fibrillation was induced experimentally using 60 Hz stimulation of the atrium and maintained in 12 sheep; four received diltiazem, four digoxin, and four no drugs (control). Aortic flow, left ventricular volume, and left ventricular pressure were monitored simultaneously. Preload-adjusted PWR(max), the slope of the end systolic pressure-volume relation (E(max)), and the maximum rate of change of left ventricular pressure (dP/dt(max)) were calculated in a beat to beat fashion.

RESULTS

Preload-adjusted PWR(max) correlated linearly with load independent E(max) (p < 0.0001) and curvilinearly with load dependent dP/dt(max) (p < 0.0001), which suggested the load independence of preload-adjusted PWR(max). After five minutes of diltiazem administration, preload-adjusted PWR(max), dP/dt(max), and E(max) fell significantly (p < 0.0001) to 62%, 64%, and 61% of baseline, respectively. Changes were not significant after five minutes of digoxin (103%, 98%, and 102%) or in controls (97%, 96%, and 95%).

CONCLUSIONS

Preload-adjusted PWR(max) correlates linearly with E(max) and is a useful measure of contractility even in atrial fibrillation. Non-invasive application of this method, in combination with echocardiography and tonometry, may yield important information for optimising the treatment of patients with atrial fibrillation.

Chronic evaluation of the Cleveland Clinic CorAide left ventricular assist system in calves

The Cleveland Clinic CorAide left ventricular assist system is based on a third-generation, implantable, centrifugal pump in which a rotating assembly is suspended fully. To evaluate chronic in vivo system performance and biocompatibility, the CorAide blood pump was implanted in 18 calves for either 1 month or 3 months. Hemodynamics were stable in all calves with a mean pump flow of 5.9 +/- 1.2 L/min and a mean systemic arterial pressure of 98 +/- 5 mm Hg. There were no incidences of bleeding, organ dysfunction, or mechanical failure in any of the 18 calves. Hemolysis occurred in only 1 calf due to outflow graft stenosis. Thrombus inside the pump, seen in 4 of the first 6 cases, was totally eliminated by a final redesign in the remaining cases, including the last 6 implants conducted without anticoagulation therapy. The CorAide blood pump demonstrated good biocompatibility and reliable, effective system performance.

Device based left ventricular shape change: validation of conductance technology in shape changed hearts

We have reported that device based left ventricular (LV) shape change, accomplished by Myosplint, improved LV systolic function by three-dimensional echocardiography (3-D echo). However, evaluation of this device using the pressure-volume relationship is still important. This study was conducted to validate the use of conductance technology for this evaluation in shape-changed hearts. An ex vivo study using excised ovine hearts (n = 11) and an in vivo study using a canine pacing-induced heart failure model (n = 11) were performed. Three Myosplints were implanted. Before and after the shape changes, volumes measured by a conductance catheter were compared with volumes measured by the amount of saline in the ex vivo study or by 3-D echo in the in vivo study. The conductance volumes were linearly correlated with the saline volumes (r2 = 0.961+/-0.046; p < 0.0001) in the ex vivo study and with 3-D echo volumes (r2 = 0.757+/-0.220; p < 0.0001) in the in vivo study. The conductance volumes were linearly correlated with LV volumes even in the shape-changed hearts. This technology can be used to evaluate pressure-volume loops in the shape-changed hearts as long as the conductance volume is calibrated by a reliable method.

In vivo studies of the MagScrew total artificial heart in calves

The purpose of this study was to evaluate the in vivo pump performance of our total artificial heart (TAH), the "MagScrew TAH." The TAH consists of a blood pump and control logic developed at the Cleveland Clinic and the MagScrew actuator and electronic control system developed by Foster-Miller Technologies, Inc. (Albany, NY). MagScrew TAH implantation was performed in two calves. Study durations were 50 and 5 days. The causes of termination were prosthetic valve endocarditis in one case and cable failure in the other. Mean left pump flow ranged from 8.0 to 9.7 L/min, with left atrial pressure of 3.0 to 16.0 mm Hg. Preload sensitivity of the MagScrew TAH demonstrated a Frank-Starling response to preload in automatic mode. The relationship between right and left atrial pressure was well balanced. Mean arterial pressure and mean pulmonary artery pressure were maintained within physiologic ranges over study duration. There were no signs of bleeding, hemolysis, or organ failure. The MagScrew TAH showed physiologic pump performance, and hemodynamics were well maintained without any organ failure. Further development testing will bring the MagScrew TAH to the point of preclinical readiness testing.

Cleveland clinic CorAide blood pump circulatory support without anticoagulation

The Cleveland Clinic CorAide left ventricular assist system consists of a permanently implantable centrifugal pump in which the rotating assembly is completely suspended and noncontacting. A series of chronic animal in vivo studies were conducted to evaluate the biologic effects of CorAide circulatory support without the use of anticoagulation therapy. The CorAide pump was implanted in six calves (five calves for 21 to 32 days and one calf for 95 days). The first five calves received intravenous heparin during the early postoperative periods (2-7 days). Heparin administration was then discontinued and no other anticoagulant drugs were used for the duration of the experiments. The last calf did not receive any anticoagulant except for a bolus dose of heparin (200 U/kg) during surgery. Hemodynamics were stable in all six calves, with a mean pump flow of 5.6+/-1.2 L/min and mean arterial pressure of 100+/-4 mm Hg. The blood pump surfaces were clean of thrombus in all six calves. Significant findings at autopsy were limited to one case of renal infarction. There was no incidence of mechanical failure, bleeding, or device infection. The CorAide pump can be safely run with minimal or no anticoagulant therapy.

Induction and maintenance of an experimental model of severe cardiomyopathy with a novel protocol of rapid ventricular pacing

OBJECTIVE

An animal model of chronic severe heart failure is needed to evaluate new mechanical devices, surgical procedures, and medical therapies. The purpose of this study was to evaluate a unique new model of severe heart failure developed by means of a novel protocol of rapid ventricular pacing.

METHODS

Heart failure was induced in 8 mongrel dogs by means of rapid ventricular pacing (230 beats/min) for 4 weeks. After a sham operation, maintenance pacing at a reduced rate (190 beats/min) was continued for another 4 weeks.

RESULTS

Left ventricular systolic function was significantly reduced at week 4 and remained low at week 8, including the slope of the end-systolic pressure-volume relationship (2.4 +/- 1.0 vs 0.7 +/- 0.2 vs 0.8 +/- 0.3 mm Hg/mL [baseline vs week 4 vs week 8, respectively]), ejection fraction (63% +/- 5% vs 28% +/- 7% vs 33% +/- 5%), and cardiac output (3.1 +/- 0.7 vs 2.0 +/- 0.3 vs 2.2 +/- 0.7 L/min). Significant ventricular remodeling changes took place with increased ventricular volumes and circumferential wall stress, which were stable between weeks 4 and 8. Serum catecholamine and atrial natriuretic polypeptide levels also increased from baseline but stabilized between weeks 4 and 8. The end-diastolic pressure-volume relationship also showed stable diastolic function between weeks 4 and 8.

CONCLUSIONS

Induction pacing at 230 beats/min readily created severe heart failure in all animals, and a new technique of maintenance pacing provided a consistent model of severe heart failure. This model can be used to study a variety of new interventions for heart failure.

Radiobiological characteristics of solid tumours depending on the p53 status of the tumour cells, with emphasis on the response of intratumour quiescent cells

Human head and neck squamous cell carcinoma cells transfected with mutant TP53 (SAS/mTP53) or with a neo vector as a control (SAS/neo) were inoculated subcutaneously (s.c.) into both hind legs of Balb/cA nude mice. Mice bearing tumours received 5-bromo-2'-deoxyuridine (BrdU) continuously to label all proliferating (P) cells in the tumours. The mice then received gamma-ray irradiation. Another group of mice received a series of test doses of gamma-rays while alive or after tumour clamping to obtain hypoxic fractions (HFs) in the tumours. Right after irradiation, the tumour cells were isolated and incubated with a cytokinesis blocker. The micronucleus (MN) frequency in the cells without BrdU labelling (=quiescent (Q) cells) was determined using immunofluorescence staining for BrdU. Meanwhile, 6 h after irradiation, tumour cell suspensions obtained in the same manner were used for determining the frequency of apoptosis in the Q cells. The MN frequency and apoptosis frequency in total (P+Q) tumour cells were determined from the tumours that were not pretreated with BrdU. In total cell populations, SAS/mTP53 cells were more radioresistant than SAS/neo cells in clonogenic survival. Q tumour cells exhibited a significantly lower apoptosis and MN frequency, probably due to their much larger HF, than total cells. In both total and Q cell fractions, SAS/mTP53 cells were less susceptible to apoptosis and more susceptible to micronucleation than SAS/neo cells. Obviously, TP53 status had the potential to influence the radiosensitivity of not only the total cells, but also the Q cells. However, irrespective of the TP53 status, significant differences in radiosensitivity between total and Q tumour cells were consistently observed. From the viewpoint of tumour control as a whole, including intratumour Q tumour cell control, a treatment modality for enhancing the Q cell response has to be considered.

Evaluation of apoptosis and micronucleation induced by reactor neutron beams with two different cadmium ratios in total and quiescent cell populations within solid tumors

PURPOSE

Response of quiescent (Q) and total tumor cells in solid tumors to reactor neutron beam irradiation with two different cadmium (Cd) ratios was examined in terms of micronucleus (MN) frequency and apoptosis frequency, using four different tumor cell lines.

METHODS AND MATERIALS

C57BL mice bearing EL4 tumors, C3H/He mice bearing SCC VII or FM3A tumors, and Balb/c mice bearing EMT6/KU tumors received 5-bromo-2'-deoxyuridine (BrdU) continuously for 5 days via implanted mini-osmotic pumps to label all proliferating (P) cells. Thirty min after i.p. injection of sodium borocaptate-10B (BSH), or 3 h after oral administration of p-boronophenylalanine-10B (BPA), the tumors were irradiated with neutron beams. The tumors without 10B-compound administration were irradiated with neutron beams or gamma-rays. This neutron beam irradiation was performed using neutrons with two different Cd ratios. The tumors were then excised, minced, and trypsinized. The tumor cell suspensions thus obtained were incubated with cytochalasin-B (a cytokinesis blocker), and the MN frequency in cells without BrdU labeling (=Q cells) was determined using immunofluorescence staining for BrdU. Meanwhile, for apoptosis assay, 6 h after irradiation, tumor cell suspensions obtained in the same manner were fixed, and the apoptosis frequency in Q cells was also determined with immunofluorescence staining for BrdU. The MN and apoptosis frequencies in total (P + Q) tumor cells were determined from the tumors that were not pretreated with BrdU.

RESULTS

Without 10B-compounds, the sensitivity difference between total and Q cells was reduced by neutron beam irradiation. Under our particular neutron beam irradiation condition, relative biological effectiveness (RBE) of neutrons was larger in Q cells than in total cells, and the RBE values were larger for low Cd-ratio than high Cd-ratio neutrons. With 10B-compounds, both frequencies were increased for each cell population, especially for total cells. BPA increased both frequencies for total cells more than BSH did. Nevertheless, the sensitivity of Q cells treated with BPA was lower than that of Q cells treated with BSH. Whether based on the MN frequency or the apoptosis frequency, similar results concerning the sensitivity difference between total and Q cells, the values of RBE, and the enhancement effect by the use of 10B-compound were obtained.

CONCLUSION

Apoptosis frequency, as well as the MN frequency, can be applied to our method for measuring the Q cell response to reactor neutron beam irradiation within solid tumor in which the ratio of apoptosis to total cell death is relatively high, as in EL4 tumor. The absolute radiation dose required to achieve the same endpoint for Q cells is much higher than that for total cells when combined with 10B-compound, especially with BPA.

Device-based change in left ventricular shape: a new concept for the treatment of dilated cardiomyopathy

OBJECTIVE

We tested a unique new device, the Myosplint device (Myocor, Inc, Maple Grove, Minn), which is designed to change left ventricular shape, reduce left ventricular wall stress, and improve left ventricular systolic function.

METHODS

Heart failure was induced in 15 dogs over 27 days by rapid pacing (230 beats/min). Seven animals underwent sham surgery, and 8 animals received 3 transventricular Myosplint devices each. Myosplint devices were tightened to create a symmetric bilobular left ventricular shape and were adjusted to produce a calculated 20% reduction in wall stress. Hemodynamic, 2-dimensional, and 3-dimensional echocardiographic studies were recorded at baseline, immediately after Myosplint placement (acute change), and at 1 month after both groups had a reduced rate (190 beats/min) of pacing designed to maintain heart failure.

RESULTS

The Myosplint group had significant sustained improvements in left ventricular ejection fraction from baseline, to the acute change, to 1 month (19% +/- 5%; 36% +/- 8%; 39% +/- 13%) and reductions of left ventricular end-systolic volumes (73 +/- 9 mL; 34 +/- 5 mL; 42 +/- 12 mL) and end-systolic wall stress by 39% (341 +/- 68 10(3) dynes x cm(- 2) to 206 +/- 28 10(3) dynes x cm(-2)) acutely and 31% (372 +/- 83 10(3) dynes x cm(-2) to 250 +/- 40 10(3) dynes x cm(-2)) at 1 month. There were no significant changes in mitral regurgitation.

CONCLUSION

Application of a Myosplint device to a dilated impaired left ventricle resulted in reduced wall stress and improved left ventricular systolic function that was sustained at 1 month. Device-based shape change is a promising new opportunity to treat patients with dilated cardiomyopathy.

In vivo hemodynamic performance of the Cleveland Clinic CorAide blood pump in calves

BACKGROUND

The Cleveland Clinic CorAide left ventricular assist system is based on a small implantable continuous-flow centrifugal blood pump with a completely suspended rotating assembly designed for long-term circulatory support (5 to 10 years).

METHODS

Between June 1999 and August 2000, the CorAide blood pump was implanted in 10 calves for 1 month and in 3 calves for 3 months.

RESULTS

The mean pump flow and arterial pressure were 6.1 +/- 1.1 L/min and 97 +/- 5 mm Hg, respectively. The mean plasma free-hemoglobin level after postoperative day 3 was 2.0 +/- 1.8 mg/dL. Renal and hepatic function remained normal in all cases. There was no incidence of mechanical failure, hemolysis, bleeding, or systemic organ dysfunction in any of the cases. Significant findings at autopsy were limited to two cases of renal infarction, one of which was associated with an outflow graft infection.

CONCLUSIONS

The CorAide blood pump is easily implanted, reliable, nonhemolytic, and nonthrombogenic, positioning it as a leading third-generation, continuous-flow left ventricular assist system with a completely suspended rotor.

Evaluation of the potential of p-boronophenylalaninol as a boron carrier in boron neutron capture therapy, referring to the effect on intratumor quiescent cells

C57BL mice bearing EL4 tumors and C3H / He mice bearing SCC VII tumors received 5-bromo-2'-deoxyuridine (BrdU) continuously for 5 days via implanted mini-osmotic pumps to label all proliferating (P) cells. Three hours after oral administration of l-p-boronophenylalanine-(10)B (BPA), or 30 min after intraperitoneal injection of sodium borocaptate-(10)B (BSH) or l-p-boronophenylalaninol (BPA-ol), a newly developed (10)B-containing alpha-amino alcohol, the tumors were irradiated with thermal neutron beams. For the combination with mild temperature hyperthermia (MTH) and / or tirapazamine (TPZ), the tumors were heated at 40 degrees C for 30 min immediately before neutron exposure, and TPZ was intraperitoneally injected 30 min before irradiation. The tumors were then excised, minced and trypsinized. The tumor cell suspensions thus obtained were incubated with cytochalasin-B (a cytokinesis blocker), and the micronucleus (MN) frequency in cells without BrdU labeling ( = quiescent (Q) cells) was determined using immunofluorescence staining for BrdU. Meanwhile, 6 h after irradiation, tumor cell suspensions obtained in the same manner were used for determining the apoptosis frequency in Q cells. The MN and apoptosis frequency in total (P + Q) tumor cells were determined from tumors that were not pretreated with BrdU. Without TPZ or MTH, BPA-ol increased both frequencies most markedly, especially for total cells. However, as with BPA, the sensitivity difference between total and Q cells was much larger than with BSH. On combined treatment with both MTH and TPZ, this sensitivity difference was markedly reduced, similarly to when BPA was used. MTH increased the (10)B uptake of all (10)B-compounds into both tumor cells. BPA-ol has good potential as a (10)B-carrier in neutron capture therapy, especially when combined with both MTH and TPZ.

Radiosensitization effect by combination with paclitaxel in vivo, including the effect on intratumor quiescent cells

PURPOSE

To evaluate the radiosensitization effect on solid tumors upon combination treatment with paclitaxel (TXL), including the effect on intratumor quiescent (Q) cells.

METHODS AND MATERIALS

Mice bearing SCC VII or EL4 solid tumors received 5-bromo-2'-deoxyuridine (BrdU) continuously for 5 days to label all proliferating (P) cells. The mice then received gamma-irradiation with or without tirapazamine (TPZ) at various time points after TXL administration. Another group of mice received a series of test doses of gamma-rays while alive or after tumor clamping to obtain hypoxic fractions (HFs) in the tumors at various time points after TXL administration. Immediately after irradiation, the tumor cells were isolated and incubated with a cytokinesis blocker. The micronucleus (MN) frequency in cells without BrdU labeling (Q cells) was determined using immunofluorescence staining for BrdU. Meanwhile, 6 h after irradiation, the tumor cells were isolated from the solid tumors in another group of mice, and the apoptosis frequency in Q cells was also determined with immunofluorescence staining for BrdU. The MN and apoptosis frequency in total (P + Q) tumor cells were determined from the tumors that were not pretreated with BrdU. For the measurement of the HFs, the MN or apoptosis frequency of Q cells was then used to calculate the surviving fraction of Q cells from the regression line for the relationship between the MN or apoptosis frequency and the surviving fraction of total tumor cells.

RESULTS

In both SCC VII and EL4 tumors, maximum values of mitotic index (MI) and apoptosis frequency were observed 9 and 24 h after TXL administration, respectively. However, on the whole, the apoptosis frequency for SCC VII was very low. gamma-Irradiation 9 h after TXL administration induced significant radiosensitization effects on the total cells of both tumors. Irradiation at 60 h had a more significant effect on total cells of EL4 tumor, but no significant effect on total cells of SCC VII tumor. Combined treatment with TXL induced no radiosensitization effect on Q cells in either tumor. The effect on Q cells was observed only after TPZ was administered. The HF of total cells in EL4 tumors decreased significantly 60 h after TXL administration.

CONCLUSION

No radiosensitization effect upon combination treatment with TXL is induced in Q tumor cells. However, the effect on P cells is produced by irradiation at the time when the maximum values of MI are induced following TXL administration. In addition, for tumors that are susceptible to apoptosis after TXL administration alone, irradiation at the time of sufficient reoxygenation in tumors after TXL administration produces a greater radioenhancement effect on P cells.

Boronated dipeptide borotrimethylglycylphenylalanine as a potential boron carrier in boron neutron capture therapy for malignant brain tumors

Takagaki, M., Ono, K., Masunaga, S-I., Kinashi, Y., Oda, Y., Miyatake, S-I., Hashimoto, N., Powell, W., Sood, A. and Spielvogel, B. F. Boronated Dipeptide Borotrimethylglycylphenylalanine as a Potential Boron Carrier in Boron Neutron Capture Therapy for Malignant Brain Tumors. Radiat. Res. 156, 118-122 (2001).A boronated dipeptide, borotrimethylglycylphenylalanine (BGPA), was synthesized as a possible boron carrier for boron neutron capture therapy (BNCT) for malignant brain tumors. In vitro, at equal concentrations of (10)B in the extracellular medium, BGPA had the same effect in BNCT as p-boronophenylalanine (BPA). Boron analysis was carried out using prompt gamma-ray spectrometry and track-etch autoradiography. The tumor:blood and tumor:normal brain (10)B concentration ratios were 8.9 +/- 2.1 and 3.0 +/- 1.2, respectively, in rats bearing intracranial C6 gliosarcomas using alpha-particle track autoradiography. The IC(50), i.e. the dose capable of inhibiting the growth of C6 gliosarcoma cells by 50% after 3 days of incubation, was 5.9 x 10(-3) M BGPA, which is similar to that of 6.4 x 10(-3) M for BPA. The amide bond of BGPA is free from enzymatic attack, since it is protected from hydrolysis by the presence of a boron atom at the alpha-carbon position of glycine. These results suggest promise for the use of this agent for BNCT of malignant brain tumors. Further preclinical studies of BGPA are warranted, since BGPA has advantages over both BPA and BSH.

A novel miniature ventricular assist device for hemodynamic support

The HemoDynamics Systems enabler is a new cardiac assist pump that can expel blood from the left ventricle and provide pulsatile flow in the aorta. We evaluated the efficacy of the 18 Fr enabler. The enabler was inserted from the left ventricular apex into the ascending aorta in eight sheep. Heart failure (mild, moderate, and severe) was induced by microsphere injection into the coronary arteries to reduce cardiac output by 10-30%, 31-50%, and more than 50% from baseline, respectively. The enabler was activated, and its flow was increased to approximately 2.0 L/min. Hemodynamic variables were recorded before and after activation. In moderate heart failure, cardiac output and mean aortic pressure increased from 2.3 +/- 0.6 L/min and 59 +/- 12 mm Hg before assist to 2.8 +/- 0.6 L/min and 70 +/- 8 mm Hg at 30 minutes after activation, respectively (p < 0.01). Left atrial pressure decreased from 17 +/- 3 to 13 +/- 4 mm Hg (p < 0.05). Similar findings were observed in mild and severe heart failure. Despite its small diameter, the enabler significantly improved the hemodynamics of failing hearts and may potentially serve as a means of peripheral left ventricular support. Further study is warranted.

Novel Device to Change Left Ventricular Shape for Heart Failure Treatment: Device Design and Implantation Procedure

The Myocor Myosplint is designed to decrease left ventricular (LV) wall stress by changing LV shape, thus improving contractile function in dilated hearts. This shape change is accomplished by surgically placing three Myosplints perpendicular to the LV long axis, drawing the LV walls inward, and creating a symmetric, bilobular LV. Specially designed instruments aid in the precise delivery of these devices. The purpose of this study was to test the safety and feasibility of the procedure in dogs. Dilated cardiomyopathy was induced in 40 healthy dogs (26.3+/-1.7 kg) by ventricular pacing at 230 beats per minute for an average of 25+/-4 days. Using epicardial echocardiography, we placed the Myosplints across the LV chamber, avoiding the major coronary arteries, papillary muscles, and mitral valve. Once placed, the Myosplints were used to draw the LV walls inward to a prescribed distance. In all cases, we successfully implanted three Myosplints without using cardiopulmonary bypass. There were no complications related to the device or procedure. Myosplint implantation to change LV shape is safe and repeatable on a beating cardiomyopathic canine heart. Further study of the procedure will be needed in humans.

Radiobiologic significance of apoptosis and micronucleation in quiescent cells within solid tumors following gamma-ray irradiation

PURPOSE

To determine the frequency of apoptosis in quiescent (Q) cells within solid tumors following gamma-ray irradiation, using four different tumor cell lines. In addition, to assess the significance of detecting apoptosis in these cell lines.

METHODS AND MATERIALS

C3H/He mice bearing SCC VII or FM3A tumors, Balb/c mice bearing EMT6/KU tumors, and C57BL mice bearing EL4 tumors received 5-bromo-2'-deoxyuridine (BrdU) continuously for 5 days via implanted mini-osmotic pumps to label all proliferating (P) cells. The mice then received gamma-ray irradiation at a dose of 4--25 Gy while alive or after tumor clamping. Immediately after irradiation, the tumors were excised, minced, and trypsinized. The tumor cell suspensions thus obtained were incubated with cytochalasin-B (a cytokinesis blocker), and the micronucleus (MN) frequency in cells without BrdU labeling (= Q cells) was determined using immunofluorescence staining for BrdU. Meanwhile, 6 hours after irradiation, tumor cell suspensions obtained in the same manner were fixed. The apoptosis frequency in Q cells was also determined with immunofluorescence staining for BrdU. The MN and apoptosis frequency in total (P + Q) tumor cells were determined from the tumors that were not pretreated with BrdU.

RESULTS

In total cells, SCC VII, FM3A, and EMT6/KU cells showed reasonable relationships between MN frequency and surviving fraction (SF). However, fewer micronuclei were induced in EL4 cells than the other cell lines. In contrast, a comparatively close relationship between apoptosis frequency and SF was found in total cells of EL4 cell line. Less apoptosis was observed in the other cell lines. Quiescent tumor cells exhibited significantly lower values of MN and apoptosis frequency probably due to their large hypoxic fraction, similar to total tumor cells on clamped irradiation.

CONCLUSION

gamma-ray irradiation induced MN formation in SCC VII, FM3A, and EMT6/KU tumor cells, and the apoptosis was marked in EL4 cells compared with the other cell lines. Our method for detecting the Q cell response to gamma-ray irradiation using P cell labeling with BrdU and the MN frequency assay was also applicable to apoptosis detection assay.

Posttransplant function of a nonbeating heart is predictable by an ex vivo perfusion method

BACKGROUND

We attempted to predict the posttransplant cardiac function of nonbeating donor hearts.

METHODS

A total of 13 dogs were studied. Hearts were left in situ for 45 minutes after cardiac arrest caused by exsanguination. Hearts were then excised and reperfused in an ex vivo perfusion apparatus after 60 minutes of warm ischemia to test whether they could eject against an 80 mm Hg afterload from a preload of 10 mm Hg. Thereafter, all hearts were transplanted orthotopically.

RESULTS

Four of 13 hearts were able to eject in the apparatus (group A). However, the other nine hearts could not eject under the defined conditions (group B). All four hearts in group A showed good posttransplant hemodynamics (systolic arterial pressure > 80 mm Hg with mean left atrial pressure < 10 mm Hg) without dopamine. However, none of nine hearts in group B could support the circulation without dopamine.

CONCLUSIONS

Nonbeating donor heart function evaluated in the perfusion apparatus predicts posttransplant heart function. This method may be applicable for selection of transplantable hearts from nonbeating heart donors.