Percutaneous aortic valve replacement. Part 3: Balloon counterpulsation of a novel temporary aortic valve

Testing of a novel percutaneous temporary aortic valve in a rabbit model of acute severe aortic regurgitation: an experimental study

PURPOSE

Device management of hemodynamic instability due to acute aortic regurgitation is not available. A novel, catheter-based, temporary aortic valve (TAV) has been in development. Early prototypes (balloon-based TAV) have undergone proof-of-concept studies in mathematical, bench and animal models. The redesigned membrane-based TAV prototype is evaluated in a rabbit model of acute severe aortic regurgitation.

METHODS

Acute aortic regurgitation was simulated by deploying a self-expanding endovascular stent across the aortic annulus. Eight rabbits of body weights ranging 4.9-5.4 kg were randomly assigned to two groups: those received additional hemodynamic support with the TAV prototype immediately after aortic regurgitation was induced versus no TAV support. The survival times of the two groups were compared.

RESULTS

Comparing the groups with TAV versus without TAV, the mean body weights were similar: 4.99 ± 0.06 vs. 5.10 ± 0.22 kg (p = 0.71). The mean stent sizes used to create acute aortic regurgitation were similar: 6.25 ± 0.50 vs. 6.75 ± 0.50 mm, respectively (p = 0.53). The mean survival times also did not differ significantly: 21.00 ± 15.41 vs. 8.25 ± 2.75 minutes, respectively (p = 0.45). A slight trend appeared to be in favor of longer survival in the TAV supported group.

CONCLUSIONS

In a rabbit model of acute massive aortic regurgitation, the use of the TAV support prototype did not hasten the animals' death, but rather survival may be enhanced by the use of the device. Future studies specifically designed to evaluate the efficacy of the TAV catheter can be valuable in this new technology.

Qualitative coronary flow evaluation of a pre-clinical percutaneous temporary aortic valve

A published balloon-based percutaneous temporary aortic valve (TAV), with a specific fixed gap-to-aorta cross-sectional area ratio, was shown to provide haemodynamic support in acute aortic regurgitation (AR). The fixed gap of the balloon-TAV, however, limits the ability to optimize the gap size balancing coronary flow vs AR protection. Hence, a reduced diastolic gap may improve AR protection, but could reduce coronary flow and increase systolic TAV flow resistance. A new membrane-based TAV, which avoids these design limitations, could guide gap size optimization and advance the development into a pre-clinical tool. The re-designed TAV prototype has a membrane-cone collapsible in systole to reduce flow resistance and expands in diastole with a gap-to-aorta cross-sectional area ratio that can be tailored to optimize AR protection and coronary flow. Without the concern for systolic TAV flow resistance, a lower limit of the gap:aorta cross-sectional area ratio could be determined. The ability of the membrane-TAV design in determining an optimal gap:aorta ratio is tested in an in vitro flow chamber. Three prototypes with reducing gap:aorta cross-sectional area ratios (35%, 15%, 0%) were tested in a flow chamber of simulated acute severe AR. Correspondingly, increasing in forward cardiac output volumes, coronary flow:aortic regurgitant volume ratios and reduction in aortic regurgitant volumes were observed (p < 0.001) in the three models. The membrane-TAV concept contains a design feature for optimization of LV protection from acute AR and coronary perfusion by defining an optimal gap:aorta ratio. Along with the results from the balloon-TAV, a clinically useful percutaneous device for the management of acute severe aortic regurgitation is becoming possible.

Percutaneous temporary aortic valve: a hemodynamic support system for acute aortic insufficiency

A percutaneous temporary aortic valve hemodynamic support catheter is a device that can conceptually maintain stable hemodynamics when significant structural damage occurs to the native aortic valve ensuing acute severe aortic insufficiency. Applications may include a bridge to surgery in active aortic valve endocarditis and an option to allow for diseased valve resection prior to transcatheter aortic valve replacement. An early prototype has undergone successful fundamental mathematical, bench and animal proof-of-concept studies. Design, concept and early data are presented and discussed.