Impact of blood pressure on coronary perfusion and valvular hemodynamics after aortic valve replacement

Analysis of Energy and Pressure in the Sinus with Different Blood Pressures after Bioprosthetic Aortic Valve Replacement

PURPOSE

To investigate the effect of changing systolic and diastolic blood pressures (SBP and DBP, respectively) on sinus flow and valvular and epicardial coronary flow dynamics after TAVR and SAVR.

METHODS

SAPIEN 3 and Magna valves were deployed in an idealized aortic root model as part of a pulse duplicating left heart flow loop simulator. Different combinations of SBP and DBP were applied to the test setup and the resulting change in total coronary flow from baseline (120/60 mmHg), effective orifice area (EOA), and left ventricular (LV) workload, with each combination, was assessed. In addition, particle image velocimetry was used to assess the Laplacian of pressure (∇ 2 P ) in the sinus, coronary and main flow velocities, the energy dissipation rate (EDR) in the sinus and the LV workload.

RESULTS

This study shows that under an elevated SBP, there is an increase in the total coronary flow, EOA, LV workload, peak velocities downstream of the valve,∇ 2 P , and EDR. With an elevated DBP, there was an increase in the total coronary flow and∇ 2 P . However, EOA and LV workload decreased with an increase in DBP, and EDR increased with a decrease in DBP.

CONCLUSIONS

Blood pressure alters the hemodynamics in the sinus and downstream flow following aortic valve replacement, potentially influencing outcomes in some patients.

Effect of Blood Pressure Levels on Sinus Hemodynamics in Relation to Calcification After Bioprosthetic Aortic Valve Replacement

Coexisting hypertension and aortic stenosis are common. Some studies showed that elevated blood pressures may be associated with progression of calcific aortic valve disease (CAVD) while others showed no correlation. Flow dynamics in the sinuses of Valsalva are considered key factors in the progression of CAVD. While the relationship between hemodynamics and CAVD is not yet fully understood, it has been demonstrated that they are tightly correlated. This study aims to investigate the effect of changing systolic and diastolic blood pressures (SBP and DBP, respectively) on sinus hemodynamics in relation to potential initiation or progression of CAVD after aortic valve replacement (AVR). Evolut R, SAPIEN 3 and Magna valves were deployed in an aortic root under pulsatile conditions. Using particle image velocimetry, the hemodynamics in the sinus were assessed. The velocity, vorticity, circulation ( Γ ) and shear stress were calculated. This study shows that under elevated SBP and DBP, velocity, vorticity, and shear stress nearby the leaflets increased. Additionally, larger fluctuations of Γ and area under the curve throughout the cardiac cycle were observed. Elevated blood pressures are associated with higher velocity, vorticity, and shear stress near the leaflets which may initiate or accelerate pro-calcific changes in the prosthetic leaflets leading to bioprosthetic valve degeneration.

Differential Impact of Blood Pressure Control Targets on Epicardial Coronary Flow After Transcatheter Aortic Valve Replacement

Background

The cause for the association between increased cardiovascular mortality rates and lower blood pressure (BP) after aortic valve replacement (AVR) is unclear. This study aims to assess how the epicardial coronary flow (ECF) after AVR varies as BP levels are changed in the presence of a right coronary lesion.

Methods

The hemodynamics of a 3D printed aortic root model with a SAPIEN 3 26 deployed were evaluated in an in vitro left heart simulator under a range of varying systolic blood pressure (SBP) and diastolic blood pressure (DBP). ECF and the flow ratio index were calculated. Flow index value <0.8 was considered a threshold for ischemia.

Results

As SBP decreased, the average ECF decreased below the physiological coronary minimum at 120 mmHg. As DBP decreased, the average ECF was still maintained above the physiological minimum. The flow ratio index was >0.9 for SBP ≥130 mmHg. However, at an SBP of 120 mmHg, the flow ratio was 0.63 (p ≤ 0.0055). With decreasing DBP, no BP condition yielded a flow ratio index that was less than 0.91.

Conclusions

Reducing BP to the current recommended levels assigned for the general population after AVR in the presence of coronary artery disease may require reconsideration of levels and treatment priority. Additional studies are needed to fully understand the changes in ECF dynamics after AVR in the presence and absence of coronary artery disease.

Effect of aortic curvature on bioprosthetic aortic valve performance

Transvalvular pressure gradient (ΔP) after aortic valve replacement is an important surrogate of aortic bioprostheses performance. Invasive ΔP is often measured after transcatheter aortic valve replacement to exclude patient-prosthetic mismatch. However, invasive aortic pressures are usually recorded in the pressure recovery (PR) zone downstream of the valve, potentially resulting in ΔP underestimation compared to noninvasive measurements. PR was extensively studied in straight ascending aortas. However, the impact of various aortic arch configurations on ΔP has not been explored. PR was assessed in a pulse duplicating simulator at various cardiac conditions of cardiac output, heart rates and pressures. Three different aortic geometries with identical root dimensions but with different aortic arches were used: (1) curvature 1, (2) curvature 2, and (3) straight aortic models. Instantaneous pressure and peak ΔP measurements were recorded incrementally along the models for each cardiac condition. The models with aortic arches produced two distinct PR zones (after the valve and after the aortic arch), whereas the model without an aortic arch produced only one PR zone (after the valve). The trend of the pressure and ΔP curves for each model was independent of the cardiac condition used, but the individually measured pressure magnitudes did change with different conditions. In this study, we illustrated the differences in PR between distinct aortic curvatures and straight aorta. PR affects pressure and ΔP measurements. These effects are clear when recording aortic pressures by catheterization and echocardiography.

A Preliminary Study on the Usage of a Data-Driven Probabilistic Approach to Predict Valve Performance Under Different Physiological Conditions

Predicting potential complications after aortic valve replacement (AVR) is a crucial task that would help pre-planning procedures. The goal of this work is to generate data-driven models based on logistic regression, where the probability of developing transvalvular pressure gradient (DP) that exceeds 20 mmHg under different physiological conditions can be estimated without running extensive experimental or computational methods. The hemodynamic assessment of a 26 mm SAPIEN 3 transcatheter aortic valve and a 25 mm Magna Ease surgical aortic valve was performed under pulsatile conditions of a large range of systolic blood pressures (SBP; 100-180 mmHg), diastolic blood pressures (DBP; 40-100 mmHg), and heart rates of 60, 90 and 120 bpm. Logistic regression modeling was used to generate a predictive model for the probability of having a DP > 20 mmHg for both valves under different conditions. Experiments on different pressure conditions were conducted to compare the probabilities of the generated model and those obtained experimentally. To test the accuracy of the predictive model, the receiver operation characteristics curves were generated, and the areas under the curve (AUC) were calculated. The probabilistic predictive model of DP > 20 mmHg was generated with parameters specific to each valve. The AUC obtained for the SAPIEN 3 DP model was 0.9465 and that for Magna Ease was 0.9054 indicating a high model accuracy. Agreement between the DP probabilities obtained between experiments and predictive model was found. This model is a first step towards developing a larger statistical and data-driven model that can inform on certain valves reliability during AVR pre-procedural planning.