Feasibility of an animal model for long-term mechanical circulatory support with Impella 5.5 implanted through carotid artery access in sheep

Impella is a mechanical circulatory support device of a catheter-based intravascular microaxial pump for left ventricular support and unloading. However, nonclinical studies assessing the effects of the extended duration of left ventricular unloading on cardiac recovery are lacking. An animal model using Impella implanted with a less invasive procedure to enable long-term support is required. This study aimed to evaluate the feasibility of an animal model for long-term support with Impella 5.5 implanted through carotid artery access in sheep.Impella 5.5 was implanted in four sheep through the proximal region of the left carotid artery without a thoracotomy, and myocardial injuries were induced by coronary microembolization. Support by Impella 5.5 was maintained for 4 weeks, and the animals were observed. The position of Impella 5.5 and cardiac function was evaluated using cardiac computer tomography at 2 and 4 weeks after implantation.All four animals completed the 4-week study without major complications. The discrepancy in the Impella 5.5 flow rate between the conscious and anesthetized states was observed depending on the device's position. Animals in whom the inflow was above the left ventricular papillary muscle had a relatively high flow rate under the maximum performance level without a suction alarm during the conscious state. Pathological changes in the aortic valve were observed. Cardiac function under the minimum performance level was observed with no remarkable deterioration.The animal model with myocardial injuries supported for 4 weeks by Impella 5.5 implanted through carotid artery access in sheep was feasible.

Hemodynamic Evaluation of Asynchronous Speed Modulation of a Continuous-Flow Left Ventricular Assist Device in an Acute-Myocardial Injury Sheep Model

Asynchronous rotational-speed modulation of a continuous-flow left ventricular assist device (LVAD) can increase pulsatility; however, the feasibility of hemodynamic modification by asynchronous modulation of an LVAD has not been sufficiently verified. We evaluated the acute effect of an asynchronous-modulation mode under LVAD support and the accumulated effect of 6 consecutive hours of driving by the asynchronous-modulation mode on hemodynamics, including both ventricles, in a coronary microembolization-induced acute-myocardial injury sheep model. We evaluated 5-min LVAD-support hemodynamics, including biventricular parameters, by switching modes from constant-speed to asynchronous-modulation in the same animals ("acute-effect evaluation under LVAD support"). To determine the accumulated effect of a certain driving period, we evaluated hemodynamics including biventricular parameters after weaning from 6-hour (6 h) LVAD support by constant-speed or asynchronous-modulation mode ("6h-effect evaluation"). The acute-effect evaluation under LVAD support revealed that, compared to the constant-speed mode, the asynchronous-modulation mode increased vascular pulsatility but did not have significantly different effects on hemodynamics, including both ventricles. The 6 h-effect evaluation revealed that the hemodynamics did not differ significantly between the two groups except for some biventricular parameters which did not indicate negative effects of the asynchronous-modulation mode on both ventricles. The asynchronous-modulation mode could be feasible to increase vascular pulsatility without causing negative effects on hemodynamics including both ventricles. Compared to the constant-speed mode, the asynchronous-modulation mode increased pulsatility during LVAD support without negative effects on hemodynamics including both ventricles in the acute phase. Six hours of LVAD support with the asynchronous-modulation mode exerted no negative effects on hemodynamics, including both ventricles, after weaning from the LVAD.

Feasibility study of an artificial placenta system consisting of a loop circuit configuration extracorporeal membrane oxygenation with a bridge circuit in the form of the umbilical arterial-venous connection

We developed a new artificial placenta (AP) system consisting of a loop circuit configuration extracorporeal membrane oxygenation (ECMO) with a bridge circuit designed to be applied to the fetus in the form of an umbilical arterial-venous connection. We aimed to evaluate the feasibility of the AP system by performing a hydrodynamic simulation using a mechanical mock circulation system and fetal animal experiment. The effect of the working condition of the AP system on the fetal hemodynamics was evaluated by hydrodynamic simulation using a mechanical mock circulation system, assuming the weight of the fetus to be 2 kg. The AP system was introduced to two fetal goats at a gestational age of 135 days. The general conditions of the experimental animals were evaluated. The mock simulation showed that in an AP system with ECMO in the form of an umbilical arterial-venous connection in series, it could be difficult to maintain fetal hemodynamics when high ECMO flow was applied. The developed AP system could have high ECMO flow with less umbilical blood flow; however, the possibility of excessive load on the fetal right-sided heart should be noted. In the animal experiment, kid 1 (1.9 kg) was maintained on the AP system for 12 days and allowed to grow to term. In kid 2 (1.6 kg), the AP system could not be established because of the occlusion of the system by a thrombus. The developed AP system was feasible under both in vitro and in vivo conditions. Improvements in the AP system and management of the general fetal conditions are essential.

Coronary microembolization sheep model by adjusting the number of microspheres based on coronary blood flow

BACKGROUND

A heart failure (HF) model using coronary microembolization in large animals is indispensable for medical research. However, the heterogeneity of myocardial response to microembolization is a limitation. We hypothesized that adjusting the number of injected microspheres according to coronary blood flow could stabilize the severity of HF. This study aimed to evaluate the effect of microsphere injection based on the left coronary artery blood flow in an animal model.

METHODS

Microembolization was induced by injecting different numbers of microspheres (polystyrene, diameter: 90 μm) into the left descending coronary artery of the two groups of sheep (400 and 600 times coronary blood flow [ml/min]). Hemodynamic parameters, the pressure-volume loop of the left ventricle, and echocardiography findings were examined at 0.5, 1.5, 3.5, and 6.5 h after microembolization.

RESULTS

End-diastolic pressure and normalized heart rate increased over time, and were significantly higher in 600 × coronary blood flow group than those in 400 × coronary blood flow group (p = 0.04 and p < 0.01, respectively). The maximum rate of left-ventricular pressure rise and normalized stroke volume decreased over time, and were significantly lower in 600 × coronary blood flow group than those in 400 × coronary blood flow group (p < 0.01 and p < 0.01, respectively). The number of microspheres per coronary blood flow was significantly correlated with the decrease in stroke volume and the maximum rate of left ventricular pressure rise in 6.5 h (r = 0.74, p = 0.01 and r = 0.71, p = 0.02, respectively).

CONCLUSIONS

Adjusting the number of injected microspheres based on the coronary blood flow enabled the creation of HF models with different degrees of severity.

Analysis of systemic vascular resistance after cardiac surgery: a retrospective cohort study

Background

Hypotension is a dangerous vital sign frequently encountered during the postoperative management of cardiac surgery. However, factors influencing the systemic vascular resistance index (SVRI), which is strongly related to hypotension, are not well understood. This study evaluated the characteristics of the SVRI according to the type of cardiac surgery.

Methods

During this retrospective cohort study, we used the clinical data of patients who underwent cardiac surgery at Asahi General Hospital from April 2014 to August 2020. We analyzed their vital signs during the first 12 hours after surgery and evaluated the differences in vital signs among four types of surgery: mitral valve (MV) surgery; aortic valve (AV) surgery; coronary artery bypass grafting (CABG); and thoracic aorta (TA) surgery. Data were compared among these four groups using one-way analysis of variance every 2 hours postoperatively. Those with significant differences were further compared using the post hoc Tukey-Kramer test.

Results

A total of 493 patients participated in this study. Overall, the SVRI decreased within 2 hours after the cardiopulmonary bypass surgery. The SVRI after MV surgery was significantly lower than that after other surgery types. The doses of inotropes used for MV surgery and TA surgery were significantly greater than those used for the other surgery types.

Conclusions

The SVRI changes significantly after cardiac surgery and may decrease, especially after MV surgery. For better results, it is necessary to consider the differences in the SVRI that are associated with different types of cardiac surgery.

[Ruptured Coronary Artery Aneurysm Associated with Coronary Artery Fistula;Report of a Case]

We report a case of a ruptured coronary artery aneurysm associated with coronary artery fistula. A 63-year-old man was suffering from cardiac tamponade due to a ruptured coronary artery aneurysm. An emergency operation was performed to repair the aneurysm. Under cardiopulmonary bypass, all inlet and outlet vessels were sutured and closed. The patient recovered uneventfully. A postoperative coronary computed tomography(CT) angiogram showed extinction of the aneurysm.

Acquired von Willebrand Syndrome due to Aortic Valve Stenosis in a Case with Antiphospholipid Antibody

Acquired von Willebrand syndrome (AVWS) is a bleeding disorder caused by an acquired deficiency of von Willebrand factor (vWF). Some patients with AVWS show a low bleeding tendency and are diagnosed by the presence of a mild prolongation of activated partial thromboplastin time (APTT) preoperatively. Another cause of APTT prolongation is the presence of antiphospholipid antibody (aPL). We experienced a case of AVWS due to aortic valve stenosis in a patient with aPL in whom aortic valve replacement surgery was successful with vWF replacement. In patients with AVWS-associated disorders who are identified based on APTT prolongation at the preoperative examination, both vWF and aPL screening tests must be performed.

What Is the Optimal Setting for a Continuous-Flow Left Ventricular Assist Device in Severe Mitral Regurgitation?

Excessive left ventricular (LV) volume unloading can affect right ventricular (RV) function by causing a leftward shift of the interventricular septum in patients with mitral regurgitation (MR) receiving left ventricular assist device (LVAD) support. Optimal settings for the LVAD should be chosen to appropriately control the MR without causing RV dysfunction. In this study, we assessed the utility of our electrocardiogram-synchronized rotational speed (RS) modulation system along with a continuous-flow LVAD in a goat model of MR. We implanted EVAHEART devices after left thoracotomy in six adult goats weighing 66.4 ± 10.7 kg. Severe MR was induced through inflation of a temporary inferior vena cava filter placed within the mitral valve. We evaluated total flow (TF; the sum of aortic flow and pump flow [PF]), RV fractional area change (RVFAC) calculated by echocardiography, left atrial pressure (LAP), LV end-diastolic pressure (LVEDP), LV end-diastolic volume (LVEDV), and LV stroke work (LVSW) with a bypass rate (PF divided by TF) of 100% under four conditions: circuit-clamp, continuous mode, co-pulse mode (increased RS during systole), and counter-pulse mode (increased RS during diastole). TF tended to be higher in the counter-pulse mode. Moreover, RVFAC was significantly higher in the counter-pulse mode than in the co-pulse mode, whereas LAP was significantly lower in all driving modes than in the circuit-clamp condition. Furthermore, LVEDP, LVEDV, and LVSW were significantly lower in the counter-pulse mode than in the circuit-clamp condition. The counter-pulse mode of our RS modulation system used with a continuous-flow LVAD may offer favorable control of MR while minimizing RV dysfunction.

Long-term outcome after the original and simple modified technique of valve-sparing aortic root reimplantation in Marfan-based population, David V University of Tokyo modification

BACKGROUND

In valve-sparing aortic root replacement (VSARR), how to reproduce Valsalva sinus has been an issue. In the original David V procedure, they put plication stitches at sinotubular junction level, although the reefing effect is limited and distal graft remains larger than native. Other modified techniques are two-grafts technique and ready-made Valsalva graft. However, the former needs graft-graft anastomosis and may not be cost-effective, while in the latter, the shape of sinus is fixed and minor adjustment is difficult. David V University of Tokyo modification (David V-UT) is our original solution to that, creating pseudosinus with one straight graft by longitudinal size-reduction running sutures above each pseudosinus. The purpose of the present study is to investigate long-term outcome of David V-UT.

METHODS

We analyzed 59 David V-UT patients from February 2004 to February 2013 and long-term outcomes were investigated by Kaplan-Meier methods. Risk factors for adverse events "death or recurrent aortic insufficiency (AI) with or without aortic valve reoperation" were analyzed by using Cox proportional hazard models.

RESULTS

Mean age was 33.1±14.5 years, and 38 patients (64%) were male. Marfan syndrome (MFS) accounts for 47 patients (80%). Only one patient was with bicuspid aortic valve. No in-hospital mortality was observed. Mean follow-up was 4.9±2.4 years. Estimated survival was 94.0±3.4% at 5 years. Freedoms from aortic valve reoperation and recurrent AI greater than mild were 95.7±3.0% and 88.9±4.7% at 5 years, respectively. In Cox proportional hazard analysis, preoperative AI greater than mild and Z score of annular diameter were significant risks for adverse events (p=0.027 and 0.045, hazard ratio 6.084 and 1.432, 95% C.I. 1.225-30.21 and 1.008-2.035, respectively).

CONCLUSIONS

Even in Marfan-characterized population, David V-UT provided satisfactory long-term outcome, comparable to other VSARR modifications. It is simple but can freely reproduce trilobed sinus with one straight graft.

Alteration of LV end-diastolic volume by controlling the power of the continuous-flow LVAD, so it is synchronized with cardiac beat: development of a native heart load control system (NHLCS)

There are many reports comparing pulsatile and continuous-flow left ventricular assist devices (LVAD). But continuous-flow LVAD with the pulsatile driving technique had not been tried or discussed before our group's report. We have previously developed and introduced a power-control unit for a centrifugal LVAD (EVAHEART®; Sun Medical), which can change the speed of rotation so it is synchronized with the heart beat. By use of this unit we analyzed the end-diastolic volume (EDV) to determine whether it is possible to change the native heart load. We studied 5 goats with normal hearts and 5 goats with acute LV dysfunction because of micro-embolization of the coronary artery. We used 4 modes, "circuit-clamp", "continuous", "counter-pulse", and "co-pulse", with the bypass rate (BR) 100%. We raised the speed of rotation of the LVAD in the diastolic phase with the counter-pulse mode, and raised it in the systolic phase with the co-pulse mode. As a result, the EDV decreased in the counter-pulse mode and increased in the co-pulse mode, compared with the continuous mode (p < 0.05), in both the normal and acute-heart-failure models. This result means it may be possible to achieve favorable EDV and native heart load by controlling the rotation of continuous-flow LVAD, so it is synchronized with the cardiac beat. This novel driving system may be of great benefit to patients with end-stage heart failure, especially those with ischemic etiology.