Evaluation of an implantable motor-driven left ventricular assist device

A console based implantable motor-driven left ventricular assist device (LVAD) was developed and tested. Ten sheep weighing 42-73 kg (mean, 54.4 kg) were used as the experimental animals. Four animals survived 5-12 h (mean, 9.5 h). The mean pump flow was 1.63 L/min, ranging from 0.8 to 2.5 L/min. The cause of termination was respiratory failure in 3 animals, bleeding in 2, ventricular fibrillation in 2, vent tube obstruction in 1, thrombus formation in 1, and mechanical failure of the driving console in 1. Following the in vivo studies, the computer regulated controller was tested in a mock circulatory system. The LVAD provided 5.34 L/min of maximum output against a mean afterload of 80 mm Hg with a filling pressure of 15 mm Hg when the pump rate was 80 bpm in the fixed rate mode. With an increase in the pump afterload from 80 to 140 mm Hg, the total system efficiency varied from 7.81 to 8.34% when the pump preload was 15 mm Hg. An ultracompact, completely implantable electromechanical VAD has been under development. This device should fit in a 60 kg adult. As the next step, we are preparing to implant this ultracompact implantable VAD with an electronic controller in an animal model with better results being expected.     

Development of rear‐impeller axial flow blood pump for realization of axial flow blood pump installed at aortic valve position

In this study, rear‐impeller axial flow blood pumps (RIAFBP) were developed to realize a trans‐valve axial ventricular assist device (VAD) which consists of the latter blood pump and a polymer monomembrane aortic valve, such as the jellyfish valve. The motor of the RIAFBP is installed in the left ventricle, and its impeller is placed at the aortic valve position. In the prototype RIAFBP, the rotation of the motor is sustained by polyethylene bushings. The RIAFBP has a length of 50 mm and diameter of 19.6 mm. The miniature RIAFBP has the same construction as that of the prototype; however, it employs a ceramic bearing and fin bearing to improve endurance and to reduce blood stagnation. The miniature RIAFBP has a length of 63 mm and diameter of 12 mm. Both RIAFBPs were examined by an in vitro experiment using a 33% glycerin solution. The prototype RIAFBP achieved a maximum pump outflow of 8.5 L/min against a pump head of 100 mm Hg at a rotational speed of 12 000 rpm. The miniature RIAFBP achieved 7 L/min against a pump head of 70 mm Hg at a rotational speed of 21 600 rpm. In conclusion, the miniature RIAFBP has enough pump performance to realize the trans‐valve axial VAD.     

Ultrasound-based estimation of remaining cardiac function in LVAD-supported ex vivo hearts

Left ventricular assist devices (LVAD) provide cardiac support to patients with advanced heart failure. Methods that can directly measure remaining LV function following device implantation do not currently exist. Previous studies have shown that a combination of loading (LV pressure) and deformation (strain) measurements enables quantitation of myocardial work. We investigated the use of ultrasound (US) strain imaging and pressure–strain loop analysis in LVAD-supported hearts under different hemodynamic and pump unloading conditions, with the aim of determining LV function with and without LVAD support. Ex vivo porcine hearts (n = 4) were implanted with LVADs and attached to a mock circulatory loop. Measurements were performed at hemodynamically defined “heart conditions” as the hearts deteriorated from baseline. Hemodynamic (including LV pressure) and radio-frequency US data were acquired during a pump-ramp protocol at speeds from 0 (with no pump outflow) to 10 000 revolutions per minute (rpm). Regional circumferential (ε_circ) and radial (ε_rad) strains were estimated over each heart cycle. Regional ventricular dyssynchrony was quantitated through time-to-peak strain. Mean change in LV pulse pressure and ε_circ between 0 and 10 krpm were −21.8 mm Hg and −7.24% in the first condition; in the final condition −46.8 mm Hg and −19.2%, respectively. ε_rad was not indicative of changes in pump speed or heart condition. Pressure–strain loops showed a degradation in the LV function and an increased influence of LV unloading: loop area reduced by 90% between 0 krpm in the first heart condition and 10 krpm in the last condition. High pump speeds and degraded condition led to increased dyssynchrony between the septal and lateral LV walls. Functional measurement of the LV while undergoing LVAD support is possible by using US strain imaging and pressure–strain loops. This can provide important information about remaining pump function. Use of novel LV pressure estimation or measurement techniques would be required for any future use in LVAD patients.     

Interaction of a Transapical Miniaturized Ventricular Assist Device With the Left Ventricle: Hemodynamic Evaluation and Visualization in an Isolated Heart Setup

New left ventricular assist devices (LVADs) offer both important advantages and potential hazards. VAD development requires better and expeditious ways to identify these advantages and hazards. We validated in an isolated working heart the hemodynamic performance of an intraventricular LVAD and investigated how its outflow cannula interacted with the aortic valve. Hearts from six pigs were explanted and connected to an isolated working heart setup. A miniaturized LVAD was implanted within the left ventricle (tMVAD, HeartWare Inc., Miami Lakes, FL, USA). In four experiments blood was used to investigate hemodynamics under various loading conditions. In two experiments crystalloid perfusate was used, allowing visualization of the outflow cannula within the aortic valve. In all hearts the transapical miniaturized ventricular assist device (tMVAD) implantation was successful. In the blood experiments hemodynamics similar to those observed clinically were achieved. Pump speeds ranged from 9 to 22 krpm with a maximum of 7.6 L/min against a pressure difference between ventricle and aorta of ～50 mm Hg. With crystalloid perfusate, central positioning of the outflow cannula in the aortic root was observed during full and partial support. With decreasing aortic pressures the cannula tended to drift toward the aortic root wall. The tMVAD could unload the ventricle similarly to LVADs under conventional cannulation. Aortic pressure influenced central positioning of the outflow cannula in the aortic root. The isolated heart is a simple, accessible evaluation platform unaffected by complex reactions within a whole, living animal. This platform allowed detection and visualization of potential hazards.     

Feasibility of a Tiny Gyro Centrifugal Pump as an Implantable Ventricular Assist Device

The Gyro pumps were developed for long-term circulatory support. The first generation Gyro pump (C1E3) achieved 1 month paracorporeal circulatory support in chronic animal experiments; the second generation (PI702) implantable ventricular assist device (VAD) was successful for over 6 months. The objective of the next generation Gyro pump is for use as a long-term totally implantable VAD and for pediatric circulatory support. This tiny Gyro pump (KP101) was fabricated with the same design concept as the other Gyro pumps. The possibility of an implantable VAD was determined after performance and hemolysis test results were compared to those of the other Gyro pumps. The pump housing and impeller were fabricated from polycarbonate with an impeller diameter of 35 mm. The diameter and height of the pump housings are 52.3 mm and 29.9 mm, respectively. At this time, a DC brushless motor drives the KP101, which is the same as that for the C1E3. The pump performance was measured in 37% glycerin water at 37 degrees C. Hemolysis tests were performed utilizing a compact mock loop filled with fresh bovine blood in a left ventricular assist device (LVAD) condition at 37 degrees C. The KP101 achieved the LVAD conditions of 5 L/min and 100 mm Hg at 2,900 rpm; generated 10 L/min against 100 mm Hg at 3,200 rpm; 3 L/min against 90 mm Hg at 2,600 rpm; and 2 L/min against 80 mm Hg at 2,400 rpm. In addition, the pump efficiency during this experiment was 12.5%. The other Gyro pumps. that is, the C1E3, PI601, and PI701, in an LVAD condition require 1,600, 2,000, and 2,000 rpm, respectively. The KP101 produced a normalized index of hemolysis (NIH) value of 0.005 g/100 L. With regard to the NIH, the other Gyro pumps, namely the C1E3, PI601, and PI701 demonstrated 0.0007, 0.0028, and 0.004 g/100 L, respectively. The KP101 produced an acceptable pressure flow curve for a VAD. The NIH value was higher than that of other Gyro pumps, but is in an acceptable range.     

Ascending aorta outflow graft location and pulsatile ventricular assist provide optimal hemodynamic support in an adult mock circulation

Although continuous flow (CF) and pulsatile flow (PF) ventricular assist devices (VADs) are being clinically used, their effects on aortic blood flow, as a measure of overall blood distribution, remain unclear. In acute VAD support animal experiments, our group has described a zone of turbulent mixing in the aortic arch. The objective of this study was to confirm this finding in the controlled setting of an adult mock circulation, simulating ventricular pathophysiologic states (normal and failing ventricle). CF and PF flow VADs were connected to ventricular apical inflow and ascending aorta (AA) or descending aorta (DA) outflow cannulae. Cardiovascular pressure and flow waveforms were recorded at varying levels of VAD bypass resulting in four test conditions: (i) CF-AA; (ii) CF-DA; (iii) PF-AA; and (iv) PF-DA. Confirming the animal data, no differences in mean aortic flow between CF and PF VADs were found, and significantly lower mean aortic arch flow with DA cannulation was noted. Mean aortic root flow decreased with increasing VAD bypass flow. As in the animal studies, despite similar mean flow rates, significant differences in waveform morphology were observed for AA and DA outflow graft locations and varying levels of VAD bypass. At 100% VAD support in the failing heart, PF restored waveform pulsatility to normal baseline while CF resulted in little pulsatility. These results confirm our earlier findings in the animal model, suggesting that outflow graft location may have a significant effect on aortic blood flow distribution. The long-term implications of these findings are being examined in ongoing studies.     

Is anterior mitral valve leaflet length important in outcome of septal myectomy for obstructive hypertrophic cardiomyopathy?

ObjectivesElongation of mitral valve leaflets is a phenotypic feature of hypertrophic cardiomyopathy, and some surgeons advocate plication of the anterior leaflet at the time of septal myectomy. The present study investigates mitral valve leaflet length and outcomes of patients undergoing septal myectomy for obstructive hypertrophic cardiomyopathy.MethodsWe reviewed the records and echocardiograms of 564 patients who underwent transaortic septal myectomy for obstructive hypertrophic cardiomyopathy between February 2015 and April 2018. Extended septal myectomy without plication of the anterior leaflet was the standard procedure. From intraoperative prebypass transesophageal echocardiograms, we measured anterior and posterior mitral valve leaflets and their coaptation length. For comparison, we performed these mitral valve leaflet measurements in 90 patients who underwent isolated coronary artery bypass grafting and 92 patients undergoing aortic valve replacement in the same period. Among patients with hypertrophic cardiomyopathy undergoing septal myectomy, we assessed left ventricular outflow tract gradient relief and 1-year survival in relation to leaflet length.ResultsMedian patient age (interquartile range) was 60.3 (50.2-67.7) years, and 54.1% were male. Concomitant mitral valve repair was performed in 36 patients (6.4%), and mitral valve replacement was performed in 8 patients (1.4%), primarily for intrinsic mitral valve disease. Patients in the hypertrophic cardiomyopathy cohort had significantly longer mitral valve leaflet measurements compared with patients undergoing coronary artery bypass grafting or aortic valve replacement (P < .001 for all 3 measurements). Preoperative resting left ventricular outflow tract gradients were not related to leaflet length (<30 mm, median 49 [21, 81.5] mm Hg vs ≥30 mm, 50.5 [21, 77] mm Hg; P = .76). Further, gradient reduction after myectomy was not related to leaflet length; patients with less than 30 mm anterior leaflet length had a median gradient reduction of 33 (69, 6) mm Hg compared with 36.5 (62, 6) mm Hg for patients with leaflet length 30 mm or more (P = .36). Anterior mitral valve leaflet length was not associated with increased 1-year mortality (P = .758).ConclusionsOur study confirms previous findings that patients with hypertrophic cardiomyopathy have slight (5 mm) elongation of mitral valve leaflets. In contrast to other reports, increased anterior mitral valve leaflet length was not associated with higher left ventricular outflow tract gradients. Importantly, we found no significant relationship between anterior mitral valve leaflet length and postoperative left ventricular outflow tract resting gradients or gradient relief. Thus, in the absence of intrinsic mitral valve disease, transaortic septal myectomy with focus on extending the excision beyond the point of septal contact is sufficient for almost all patients.     

Intramyocardial delivery of bone marrow mononuclear cells and mechanical assist device implantation in patients with end-stage cardiomyopathy

In end-stage heart failure, mechanical ventricular assist devices (VAD) are being used as bridge-to-transplantation, as a bridge-to-recovery, or as the definitive therapy. We tested the hypothesis that myocardial implantation of autologous bone marrow mononuclear cells (BMNC) increases the likelihood of successful weaning from left VAD (LVAD) support. Ten patients (aged 14-60 years) with deteriorating heart function underwent LVAD implantation and concomitant implantation of autologous BMNC. Bone marrow was harvested prior to VAD implantation and BMNC were prepared by density centrifugation. Two patients received a pulsatile, extracorporeal LVAD and eight a nonpulsatile implantable device. Between 52 and 164 x 10(7) BMNC containing between 1 and 12 x 10(6) CD34+ cells were injected into the LV myocardium. There was one early and one late death. The median time on LVAD support was 243 days (range 24-498 days). Repeated echocardiographic examinations under increased hemodynamic load revealed a significant improvement of LV function in one patient. Three patients underwent heart transplantation, and four patients remain on LVAD support >1 year without evidence of recovery. Only one patient was successfully weaned from LVAD support after 4 months, and LV function has remained stable ever since. In patients with endstage cardiomyopathy, intramyocardial injection of BMNC at the time of LVAD implantation does not seem to increase the likelihood of successful weaning from VAD support. Other cell-based strategies should be pursued to harness the potential of cell therapy in LVAD patients.     

Detection of left ventricle function from a magnetically levitated impeller behavior

The magnetically levitated (Mag-Lev) centrifugal rotary blood pump (CRBP) with two-degrees-of-freedom active control is promising for safe and long-term support of circulation. In this study, Mag-Lev CRBP controllability and impeller behavior were studied in the simulated heart failure circulatory model. A pneumatically driven pulsatile blood pump (Medos VAD [ventricular assist device]-54 mL) was used to simulate the left ventricle (LV). The Mag-Lev CRBP was placed between the LV apex and aortic compliance tank simulating LV assistance. The impeller behavior in five axes (x, y, z, theta, and phi) was continuously monitored using five eddy current sensors. The signals of the x- and y-axes were used for feedback active control, while the behaviors of the other three axes were passively controlled by the permanent magnets. In the static mock circuit, the impeller movement was controlled to within +/-10-+/-20 microm in the x- and y-axes, while in the pulsatile circuit, LV pulsation was modulated in the impeller movement with the amplitude being 2-22 microm. The amplitude of impeller movement measured at 1800 rpm with the simulated failing heart (peak LV pressure [LVP] = 70 mm Hg, mean aortic pressure [AoP(mean)] = 55 +/- 20 mm Hg, aortic flow = 2.7 L/min) was 12.6 microm, while it increased to 19.2 microm with the recovered heart (peak LVP = 122 mm Hg, AoP(mean) = 100 +/- 20 mm Hg, aortic flow = 3.9 L/min). The impeller repeated the reciprocating movement from the center of the pump toward the outlet port with LV pulsation. Angular rotation (theta, phi) was around +/-0.002 rad without z-axis displacement. Power requirements ranged from 0.6 to 0.9 W. Five-axis impeller behavior and Mag-Lev controller stability were demonstrated in the pulsatile mock circuit. Noncontact drive and low power requirements were shown despite the effects of LV pulsation. The impeller position signals in the x- and y-axes reflected LV function. The Mag-Lev CRBP is effective not only for noncontact low power control of the impeller, but also for diagnosis of cardiac function noninvasively.     

Performance of a new implantable cardiac assist centrifugal pump

The AB-180 is a new implantable centrifugal pump with a low volume dome (10 ml) and a local heparin delivery system which avoids systemic heparinization. This study focuses on its hemodynamic performance. We analyzed 3 anesthetized calves (71.0 +/- 2.5 kg), equipped with arterial pressure (AP), and Swan-Ganz and left atrial pressure (LAP) catheters. The AB-180 pump was installed through a left thoracotomy, with a transmitral left ventricular (LV) inflow cannula inserted via the left appendage and an outflow tract sutured to the descending aorta. LAP, AP, and blood flow across the pump were recorded for various pump speed and in different preload conditions (right atrial pressure = 4, 7, and 10 mm Hg, respectively). The pump significantly unloaded the left heart cavities and was able to increase the mean AP. For an RAP of 10 mm Hg, running the pump at 4,500 rpm decreased the LAP from 11.0 +/- 0.8 mm Hg to 3.0 +/- 0.8 mm Hg (p < 0.001) and augmented the mean AP from 48.2 +/- 6.4 mm Hg to 80.8 +/- 12.1 mm Hg (p < 0.001). A maximal pump flow of 5.6 +/- 0.2 L/min was obtained under these conditions. In addition to the advantage of its particular design, the AB-180 can be considered as an efficient left ventricular assist device (LVAD). It significantly unloads the left heart cavities and ensures efficient systemic AP and blood flow.     

Reducing regional flow stasis and improving intraventricular hemodynamics with a tipless inflow cannula design: An in vitro flow visualization study using the EVAHEART LVAD

Due to the high stroke rate of left ventricular assist device (LVAD) patients, reduction of thrombus has emerged as an important target for LVAD support. Left ventricular blood flow patterns with areas of flow stasis and recirculation are associated with platelet aggregation, which is worsened by exposure to high shear stress. Previous reports of intraventricular thrombus in LVAD patients have identified the outside of the LVAD inflow cannula as a nidus for LV thrombus formation. Previous studies of LVAD inflow cannula design have shown a region of low blood velocity and pulsatility at the apex, adjacent to the cannula. One unresolved question is whether the standard practice of inserting the LVAD inflow cannula several mm into the LV could be revised to reduce thrombus formation. To address this, a “tipless” inflow cannula was designed for the EVAHEART LVAS, and assessed in a mock circulatory loop of the LVAD‐supported heart. Customized transparent silicone models of a dilated LV were connected to the EVAHEART LVAS at the apex with a clear polycarbonate inflow cannula for flow visualization using particle image velocimetry (PIV). The “tipless” cannula was inserted flush with the endocardial border and did not protrude into the LV. This condition was compared to the standard cannula position with a 1‐cm insertion into the LV. The Pre‐LVAD condition corresponded to a severe heart failure patient (ejection fraction of 24%) with a dilated LV (180 mL). LVAD support was provided at speeds of 1.8 and 2.3 krpm. At the lower LVAD speed, 63% of the flow passed through the LVAD, with the remainder ejecting through the aortic valve. When LVAD speed was increased, nearly all flow (98%) left the LV through the LVAD. Both LVAD speed conditions produced a vortex ring similar to the Pre‐LVAD condition in diastole. However, the protruding inflow cannula interrupted the growth and restricted the movement of the vortex, and produced areas of low velocity and pulsatility adjacent to the cannula. The tipless cannula exhibited an uninterrupted pattern of the mitral jet toward the LV apex, which allowed the diastolic vortex to grow and aid in the washout of this region. In addition, the tipless cannula increased aortic valve flow, which reduces stasis in the left ventricular outflow tract. The EVAHEART LVAS tipless inflow cannula design improved regional velocity, pulsatility, and vortex formation compared to the standard protruding design, which all reduce the risk of thrombus formation. The clinical significance of the differences observed in the flow field will be dependent on other factors such as the cannula material and surface characteristics, as well as the patients' coagulation status.     

Pulsatile Total Artificial Heart Using a Reversible Rotary Pump

Abstract: A pump circuit was assembled and examined for use as an implantable artificial heart. The circuit consisted of a gear pump and 4 artificial heart valves. Mitral and pulmonary arterial valves were placed at the inflow port of the pump, and aortic and tricuspid valves were placed at the outflow port. The mitral and the tricuspid valves were connected to each reservoir at 10 mm Hg, and the aortic and the pulmonary arterial valves were connected to the head tanks at 80 and 20 mm Hg, respectively. The pump discharged pulsatile flows into both systemic and pulmonary arteries alternately by switching the direction of rotation periodically. Because the rated discharge was 1.7 L/min for the gear pump used, the measured flow rate was 0.8-0.75 L/min at a heart rate of 60–110 bpm.     

Use of the Alfieri edge-to-edge technique to eliminate left ventricular outflow tract obstruction caused by mitral systolic anterior motion

A 68-year-old woman with concentric left ventricular hypertrophy, prosthetic valve endocarditis with aortic root abscess, and sepsis had aortic root replacement with an aortic allograft. On weaning from cardiopulmonary bypass, she had hemodynamic instability caused by systolic anterior motion of the mitral valve, which resulted in a left ventricular outflow tract obstruction; the peak pressure gradient across the left ventricular outflow tract was 130 mm Hg, and there was moderately severe (3+) mitral regurgitation. After reinstitution of cardiopulmonary bypass, a central Alfieri edge-to-edge stitch was placed between the anterior and posterior leaflets of the mitral valve. This reduced the gradient across the left ventricular outflow tract to 10 mm Hg and eliminated the mitral regurgitation, which enabled successful separation from cardiopulmonary bypass.     

Transcatheter aortic valve replacement in left ventricular assist device patient‐overcoming the complications with transapical approach and circulatory arrest

We present the patient with severe aortic insufficiency (AI) 5 years post left ventricular assist device (LVAD) implantation. His management was complicated with unsuccessful percutaneous aortic valve closure attempt, transcatheter aortic valve replacement (TAVR) implantation with a severe paravalvular leak, eventual valve dislodgment into the left ventricle (LV), and LVAD inflow cannula occlusion. We utilized a mini‐thoracotomy approach to successfully retrieve the dislodged valve through the LV apex while deploying a valve‐in‐valve TAVR under direct visualization and deep hypothermic cardiac arrest. This case can serve as an example of the serious pitfalls and potential resolution strategies when treating LVAD‐associated AI.     

Impact of turbulent blood flow in the aortic root on de novo aortic insufficiency during continuous-flow left ventricular-assist device support

Severe aortic insufficiency (AI) after implantation of continuous-flow left ventricular-assist device (LVAD) affects device performance and outcomes. However, the mechanism for the occurrence and progression of AI has not been elucidated. We investigated the impact of nonphysiological retrograde blood flow in the aortic root on AI after LVAD implantation. Blood flow pattern was analyzed in patients with and without AI (n = 3 each) who underwent LVAD implantation, by computational fluid dynamics with patient-specific geometries, which were reproduced using electrocardiogram-gated 320-slice computed tomographic images. The total volume of retrograde blood flow during one cardiac cycle (716 ± 88 mL) was higher and the volume of slow blood flow (<0.1 cm/s) (0.16 ± 0.04 cm³) was lower in patients with AI than in those without AI (360 ± 111 mL, P = .0495, and 0.49 ± 0.08 cm³, P = .0495, respectively). No significant difference in wall shear stress on the aortic valve was observed between the groups. Patients with AI had a perpendicular anastomosis at the distal ascending aorta and the simulation in the modified anastomosis model of patients with AI showed that the retrograde blood flow pattern depended on the angle and position of anastomosis. Computational fluid dynamics revealed strong retrograde blood flow in the ascending aorta and aortic root in patients with AI after LVAD implantation. The angle and position of LVAD outflow anastomosis might impact retrograde blood flow and de novo AI after LVAD implantation.     

Left ventricular pressure and volume unloading during pulsatile versus nonpulsatile left ventricular assist device support

BACKGROUND: Nonpulsatile axial or centrifugal pumps are the latest generation of left ventricular assist devices (LVAD). Whether left ventricular (LV) unloading and outcome in these devices is similar to pulsatile LVADs during long-term support has not been investigated. We compared LV unloading and mortality between different types of LVAD support (pulsatile versus nonpulsatile). METHODS: In 31 patients undergoing long-term LVAD implantation (nonpulsatile = 10, pulsatile = 21) preoperative and postoperative echocardiographic and hemodynamic assessment with right heart catheterization had been obtained. RESULTS: All patients had similar echocardiographic, hemodynamic, and clinical heart failure characteristics at baseline. The degree of LV pressure unloading was the same in both device types, caused by similar reduction of mean pulmonary pressure (18.6 +/- 5.1 versus 18.3 +/- 7.5 mm Hg) and pulmonary capillary wedge pressure (8.9 +/- 4.4 versus 8.0 +/- 7.0 mm Hg). Left ventricular volume unloading was pronounced with a pulsatile device owing to a statistically significant higher pump output (5.1 +/- 1.0 L/min) in comparison with nonpulsatile LVADs (3.6 +/- 0.9 L/min, p < 0.001). Echocardiographic-determined end-systolic indicators confirm this augmentation in pulsatile LVADs. Etiology or the time interval of hemodynamic reassessment had no impact in left ventricular pressure unloading, but LV volume unloading decreased between day 60 and 120 in patients with nonpulsatile LVADs. The preoperative and postoperative transplant mortality was comparable in both groups. CONCLUSIONS: Left ventricular pressure unloading is similar in patients with nonpulsatile as compared with pulsatile implantable long-term assist devices. Left ventricular volume unloading is pronounced in pulsatile LVADs.     

Surgical options in subaortic stenosis associated with endocardial cushion defects

Over a 15-year period, 12 patients with endocardial cushion defects undergoing correction had subaortic stenosis requiring operative intervention. Ages ranged from 4 months to 17 years (mean, 7 +/- 6 years) and subaortic gradients from 15 to 100 mm Hg (mean, 60 +/- 25 mm Hg). Subaortic stenosis was due to discrete fibromuscular tissues in 7 patients, mitral valve malattachment in 3, and tunnel outflow in 2. In 2, the subaortic stenosis was clinically significant at the time of endocardial cushion defects repair, whereas in 10 it was noted 2 to 14 years postoperatively (mean, 6.3 +/- 5 years). Surgical relief of subaortic stenosis was accomplished by resection of muscle tissues in 7, apicoaortic conduit insertion in 2, modified Konno procedure (aortic valve preserved) in 2, and lifting of malattached mitral valve from the outflow in 1. There was no early death and one late death (infected conduit). Severe mitral insufficiency developed in the patient who had the mitral valve lifted and necessitated valve replacement. Postoperative echocardiographic gradient in 9 patients ranged from 0 to 36 mm Hg (mean, 10.5 +/- 14 mm Hg). Clinically significant subaortic stenosis has not developed in any patient in 15 years of follow-up (mean, 5 +/- 4 years). We conclude that in subaortic stenosis associated with endocardial cushion defects, resection is effective for discrete obstruction, whereas a modified Konno procedure is preferable for obstruction due to tunnel outflow or mitral valve malattachment.     

Radial Artery Tonometry to Monitor Blood Pressure and Hemodynamics in Ambulatory Left Ventricular Assist Device Patients in Comparison With Doppler Ultrasound and Transthoracic Echocardiography: A Pilot Study

Noninvasive measurements of blood pressure (BP) and cardiac output (CO) are crucial in the follow‐up of continuous‐flow left ventricular assist device (CF‐LVAD) patients. For our pilot study, we sought to compare BP measurements between a tonometry blood pressure pulse analyzer (BPPA) (DMP‐Life, DAEYOMEDI Co., Ltd., Gyeonggi‐do, South Korea) and Doppler ultrasound in CF‐LVAD patients, as well as to compare the BPPA estimated CO to LVAD calculated blood flow and to the patient’s intrinsic CO estimated with transthoracic echocardiography (TTE). Ambulatory CF‐LVAD patients (6 HeartMate, 26 HeartMate II), were included. According to TTE findings, patients were then subdivided in two groups: patients with an opening aortic valve (OAV) [n = 21] and those with an intermittent opening aortic valve (IOAV) [n = 11]. We found a very good correlation of systolic BP (SBP) measurements between the two methods, BPPA and Doppler ultrasound (r = 0.87, P < 0.0001). Bland‐Altman plots for SBP revealed a low bias of ?4.6 mm Hg and SD of ±4.7 mm Hg. In CF‐LVAD patients with IOAV, the BPPA‐CO had a good correlation with the LVAD‐flow (r = 0.78, P < 0.0001), but in OAV patients, there was no correlation. After adding the patient’s intrinsic CO, estimated from TTE in patients with OAV to the LVAD‐flow, we found a very good correlation between the BPPA‐CO and LVAD‐flow + TTE‐CO (r = 0.81, P = 0.002). Our study demonstrated that compared with the standard clinical method, Doppler ultrasound, the BPPA measured BP noninvasively with good accuracy and precision of agreement. In addition, tonometry BPPA provided further valuable information regarding the CF‐LVAD patient’s intrinsic CO.     

Influence of the Compliance of the Pump Housing and Cannulas of a Paracorporeal Pneumatic Ventricular Assist Device on Transient Pressure Characteristics

Abstract: The dependence of transient pressure characteristics of a ventricular assist device (VAD) on the compliance of its housing and cannulas was investigated in a mock circulation. The peak rate of change of pressure ( dP/dt _max) values was greater in the cannulas than other compartments and was associated with valve closure-induced pressure oscillations. When cannula compliance was increased from 0.0057 to 0.0129 cm³/mm Hg, these values decreased by ˜20%, and outflow cannula pressure oscillation frequency decreased from 17.5 Hz by 35%. This trend was also apparent in the inflow. A VAD housing compliance increase from 0.0162 to 0.0483 cm³/mm Hg caused a dP/dt _max decrease of 30% in both the blood chamber and the outflow cannula. The effect of this change on the inflow was weaker implying that housing absorbs the energy associated with outflow deceleration more effectively than the inflow. These findings suggest that increasing VAD housing and cannulas compliance can improve hydrodynamic performance.     

Congenital aortic and truncal valve reconstruction using the Ozaki technique: Short-term clinical results

ObjectivesAortic valve reconstruction (AVRec) with neocuspidization or the Ozaki procedure with complete cusp replacement for aortic valve disease has excellent mid-term results in adults. Limited results of AVRec in pediatric patients have been reported. We report our early outcomes of the Ozaki procedure for congenital aortic and truncal valve disease.MethodsA retrospective analysis was performed on all 57 patients with congenital aortic and truncal valve disease who had a 3-leaflet Ozaki procedure at a single institution from August 2015 to February 2019. Outcome measures included mortality, surgical or catheter-based reinterventions, and echocardiographic measurements.ResultsTwenty-four patients had aortic regurgitation (AR), 6 had aortic stenosis (AS), and 27 patients had AS/AR. Two patients had quadricuspid valves, 26 had tricuspid, 20 had bicuspid, and 9 had unicusp aortic valves. Four patients had truncus arteriosus. Thirty-four patients had previous aortic valve repairs and 5 had replacements. Preoperative echocardiography mean annular diameter was 20.90 ± 4.98 cm and peak gradient for patients with AS/AR was 53.62 ± 22.20 mm Hg. Autologous, Photofix, and CardioCel bovine pericardia were used in 20, 35, and 2 patients. Eight patients required aortic root enlargement and 20 had sinus enlargement. Fifty-one patients had concomitant procedures. Median intensive care unit and hospital length of stay were 1.87 and 6.38 days. There were no hospital mortalities or early conversions to valve replacement. At discharge, 98% of patients had mild or less regurgitation and peak aortic gradient was 16.9 ± 9.5 mm Hg. Two patients underwent aortic valve replacement. At median follow-up of 8.1 months, 96% and 91% of patients had less than moderate regurgitation and stenosis, respectively.ConclusionsThe AVRec procedure has acceptable short-term results and should be considered for valve reconstruction in pediatric patients with congenital aortic and truncal valve disease. Longer-term follow-up is necessary to determine the optimal patch material and late valve function and continued annular growth.