Impact of Valvulo-Arterial Impedance on Long-Term Quality of Life and Exercise Performance After Transcatheter Aortic Valve Replacement

Soft robotic platform for progressive and reversible aortic constriction in a small-animal model

Our understanding of cardiac remodeling processes due to left ventricular pressure overload derives largely from animal models of aortic banding. However, these studies fail to enable control over both disease progression and reversal, hindering their clinical relevance. Here, we describe a method for progressive and reversible aortic banding based on an implantable expandable actuator that can be finely tuned to modulate aortic banding and debanding in a rat model. Through catheterization, imaging, and histologic studies, we demonstrate that our platform can recapitulate the hemodynamic and structural changes associated with pressure overload in a controllable manner. We leveraged soft robotics to enable noninvasive aortic debanding, demonstrating that these changes can be partly reversed because of cessation of the biomechanical stimulus. By recapitulating longitudinal disease progression and reversibility, this animal model could elucidate fundamental mechanisms of cardiac remodeling and optimize timing of intervention for pressure overload.

The Effect of Surgical Aortic Valve Replacement on Arterial Stiffness: Does the Valve Type Matter?

Background: Despite the increasing use of transcatheter aortic valve procedures, many patients still require surgical aortic valve replacement (SAVR). Assessing arterial properties in patients undergoing SAVR for aortic valve stenosis can be challenging, and the existing evidence is inconclusive. Our study aimed to investigate the impact of SAVR on vascular stiffness and the quality of life, as well as the different effects of valve type on arterial properties. Methods: We included 60 patients (mean age 70.25 ± 8.76 years, 65% men) with severe symptomatic aortic stenosis who underwent SAVR. Arterial stiffness (cfPWV, baPWV) and vascular parameters (AIx@75, central pressures, SEVR) were measured at baseline, pre-discharge, and 1-year post-operation. The QOL was assessed using the generic questionnaire-short-form health survey 36 (SF-36) pre-operatively and at 1 year. Results: Post-SAVR, cfPWV increased immediately (7.67 ± 1.70 m/s vs. 8.27 ± 1.92 m/s, p = 0.009) and persisted at 1 year (8.27 ± 1.92 m/s vs. 9.29 ± 2.59 m/s, p ≤ 0.001). Similarly, baPWV (n = 55) increased acutely (1633 ± 429 cm/s vs. 2014 ± 606 cm/s, p < 0.001) and remained elevated at 1 year (1633 ± 429 cm/s vs. 1867 ± 408 cm/s, p < 0.001). Acute decrease in Alx@75 (31.16 ± 10% vs. 22.48 ± 13%, p < 0.001) reversed at 1 year (31.16 ± 10% vs. 30.98 ± 9%, p = 0.71). SEVR improved (136.1 ± 30.4% vs. 149.2 ± 32.7%, p = 0.01) and persisted at 1 year (136.1 ± 30.4% vs. 147.5 ± 30.4%, p = 0.01). SV had a greater cfPWV increase at 1 year (p = 0.049). The QOL improved irrespective of arterial stiffness changes. Conclusions: After SAVR, arterial stiffness demonstrates a persistent increase at 1-year, with valve type having a slight influence on the outcomes. These findings remain consistent despite the perceived QOL.

Exploring the mechanisms responsible for reduced systolic function in high-gradient aortic stenosis

OBJECTIVE

To characterise the mechanics responsible for the reduced ejection fraction (rEF) in high-gradient severe aortic stenosis (AS).

METHODS

21 patients with high-gradient severe AS (aortic valve area (AVA) <1.0 cm2 and mean gradient (MG) >40 mm Hg) were included. They included 9 patients with rEF (EF <50%) and 12 with preserved ejection fraction (pEF) (EF >50%). Valve area and MG were assessed echocardiographically, and myocardial fibrosis was quantified using MRI. Load-independent measures of intrinsic contractility was assessed with pressure-volume haemodynamics.

RESULTS

80% of the cohort was female, with a mean age of 64 years. Patients were matched for age, sex and body surface area. Load-independent contractile function was similar between the rEF and pEF groups: preload recruitable stroke work slope (101 vs 112 mm Hg; p=0.65), end-systolic pressure-volume relationship slope (1.91 vs 1.28 mmHg/mL; p=0.07) and Starling Contractile Index slope (3.47 vs 7.96 mm Hg/mL/s; p=0.31). End-systolic wall stress and valvuloarterial impedance were higher in cases with rEF (150 vs 83.5 N/cm2; p<0.01 and 4.8 vs 3.4 mm Hg/mL; p=0.05), driven by higher degrees of valvular stenosis (valve area 0.46 vs 0.78 cm2; p<0.01). The rEF group was more symptomatic (New York Heart Association 3.3 vs 2.3; p=0.02), with higher pulmonary pressures (50 vs 30 mm Hg; p=0.04) and more fibrosis (24% vs 13% of left ventricular mass; p=0.03).

CONCLUSION

The pathophysiological problem in patients with high-gradient AS with rEF relates to an excessively increased afterload due to more severe valvular stenosis, with preserved intrinsic contractile function. Myocardial fibrosis in the rEF group did not translate into worse muscle function.

Left ventricular reverse remodeling after transcatheter aortic valve implantation in patients with low-flow low-gradient aortic stenosis

OBJECTIVES

Left ventricular reverse remodeling (LVRR) is associated with improved outcome in patients with heart failure. Factors associated with and predictive of LVRR in patients with low-flow low-gradient aortic stenosis (LFLG AS) after transcatheter aortic valve implantation (TAVI) and its impact on outcome were assessed.

METHODS

Pre- and postprocedural left ventricular (LV) function and volume were investigated in 219 patients with LFLG. LVRR was defined as an absolute increase of ≥10% in LV ejection fraction (LVEF) and reduction of ≥15% in LV end-systolic volume (LVESV). The primary endpoint was the combination of all-cause mortality and rehospitalization for heart failure.

RESULTS

The mean LVEF was 35.0 ± 10.0%, with a stroke volume index (SVI) of 25.9 ± 6.0 mL/m2 and LVESV of 94.04 ± 46.0 mL. At a median of 5.2 months (interquartile range, 2.7-8.1 months), 77.2% (n = 169) of the patients showed echocardiographic evidence of LVRR. A multivariate model revealed three independent factors for LVRR after TAVI: SVI of <25 mL/m2 (hazard ratio [HR], 2.31; 95% confidence interval [CI], 1.08-3.58; p < 0.01), LVEF of <30% (HR, 2.76; 95% CI, 1.53-2.91; p < 0.01), and valvulo-arterial impedance (Zva) of <5 mmHg/mL/m2 (HR, 5.36; 95% CI, 1.80-15.98; p < 0.01). Patients without evidence of LVRR showed a significantly higher incidence of the 1-year combined endpoint (32 [64.0%] vs. 75 [44.4%], p < 0.01).

CONCLUSIONS

The majority of patients with LFLG AS show LVRR after TAVI, which is associated with favorable outcomes. An SVI of <25 mL/m2, LVEF of <30%, and Zva < 5mmHg/mL/m2 represent predictors of LVRR.

Using Augmented Mean Arterial Pressure to Identify High Mortality Risk Patients With Moderate Aortic Stenosis

OBJECTIVE

To study the usefulness of a novel echocardiographic marker, augmented mean arterial pressure (AugMAP = [(mean aortic valve gradient + systolic blood pressure) + (2 × diastolic blood pressure)] / 3), in identifying high-risk patients with moderate aortic stenosis (AS).

PATIENTS AND METHODS

Adults with moderate AS (aortic valve area, 1.0-1.5 cm2) at Mayo Clinic sites from January 1, 2010, through December 31, 2020, were identified. Baseline demographic, echocardiographic, and all-cause mortality data were retrieved. Patients were grouped into higher and lower AugMAP groups using a cutoff value of 80 mm Hg for analysis. Kaplan-Meier and Cox regression models were used to assess the performance of AugMAP.

RESULTS

A total of 4563 patients with moderate AS were included (mean ± SD age, 73.7±12.5 years; 60.5% men). Median follow-up was 2.5 years; 36.0% of patients died. The mean ± SD left ventricular ejection fraction (LVEF) was 60.1%±11.4%, and the mean ± SD AugMAP was 99.1±13.1 mm Hg. Patients in the lower AugMAP group, with either preserved or reduced LVEF, had significantly worse survival performance (all P<.001). Multivariate Cox regression showed that AugMAP (hazard ratio, 0.962; 95% CI, 0.942 to 0.981 per 5-mm Hg increase; P<.001) and AugMAP less than 80 mm Hg (hazard ratio, 1.477; 95% CI, 1.241 to 1.756; P<.001) were independently associated with all-cause mortality.

CONCLUSION

AugMAP is a simple and effective echocardiographic marker to identify high-risk patients with moderate AS independent of LVEF. It can potentially be used in the candidate selection process if moderate AS becomes indicated for aortic valve intervention in the future.

Soft robotics-enabled large animal model of HFpEF hemodynamics for device testing

Heart failure with preserved ejection fraction (HFpEF) is a major challenge in cardiovascular medicine, accounting for approximately 50% of all cases of heart failure. Due to the lack of effective therapies for this condition, the mortality associated with HFpEF remains higher than that of most cancers. Despite the ongoing efforts, no medical device has yet received FDA approval. This is largely due to the lack of an in vivo model of the HFpEF hemodynamics, resulting in the inability to evaluate device effectiveness in vivo prior to clinical trials. Here, we describe the development of a highly tunable porcine model of HFpEF hemodynamics using implantable soft robotic sleeves, where controlled actuation of a left ventricular and an aortic sleeve can recapitulate changes in ventricular compliance and afterload associated with a broad spectrum of HFpEF hemodynamic phenotypes. We demonstrate the feasibility of the proposed model in preclinical testing by evaluating the hemodynamic response of the model post-implantation of an interatrial shunt device, which was found to be consistent with findings from in silico studies and clinical trials. This work addresses several of the limitations associated with previous models of HFpEF, such as their limited hemodynamic fidelity, elevated costs, lengthy development time, and low throughput. By showcasing exceptional versatility and tunability, the proposed platform has the potential to revolutionize the current approach for HFpEF device development and selection, with the goal of improving the quality of life for the 32 million people affected by HFpEF worldwide.

Quality of Life Measures in Aortic Stenosis Research: A Narrative Review

BACKGROUND

Elderly patients with aortic stenosis (AS) not only have a reduced life expectancy but also a reduced quality of life (QoL). The benefits of an AS intervention may be considered a balance between a good QoL and a reasonably extended life. However, the different questionnaires being used to determine the QoL were generally not developed for the specific situation of patients with AS and come with strengths and considerable weaknesses. The objective of this article was to provide an overview of the available QoL instruments in AS research, describe their strengths and weaknesses, and provide our assessment of the utility of the available scoring instruments for QoL measurements in AS.

SUMMARY

We identified and reviewed the following instruments that are used in AS research: Short Form Health Survey (SF-36/SF-12), EuroQol-5D (EQ-5D), the Illness Intrusiveness Rating Scale (IIRS), the HeartQoL, the Kansas City Cardiomyopathy Questionnaire (KCCQ), the Minnesota Living with Heart Failure Questionnaire (MLHF), the MacNew Questionnaire, and the Toronto Aortic Stenosis Quality of Life Questionnaire (TASQ).

KEY MESSAGES

There is no standardized assessment of QoL in patients with AS. Many different questionnaires are being used, but they are rarely specific for AS. There is a need for AS-specific research into the QoL of patients as life prolongation may compete for an improved QoL in this elderly patient group.

Transcatheter Aortic Valve Replacement Prognostication with Augmented Mean Arterial Pressure

BACKGROUND

Post-transcatheter aortic valve replacement (TAVR) patient outcome is an important research topic. To accurately assess post-TAVR mortality, we examined a family of new echo parameters (augmented systolic blood pressure (AugSBP) and arterial mean pressure (AugMAP)) derived from blood pressure and aortic valve gradients.

METHODS

Patients in the Mayo Clinic National Cardiovascular Diseases Registry-TAVR database who underwent TAVR between 1 January 2012 and 30 June 2017 were identified to retrieve baseline clinical, echocardiographic and mortality data. AugSBP, AugMAP and valvulo-arterial impedance (Zva) (Zva) were evaluated using Cox regression. Receiver operating characteristic curve analysis and the c-index were used to assess the model performance against the Society of Thoracic Surgeons (STS) risk score.

RESULTS

The final cohort contained 974 patients with a mean age of 81.4 ± 8.3 years old, and 56.6% were male. The mean STS risk score was 8.2 ± 5.2. The median follow-up duration was 354 days, and the one-year all-cause mortality rate was 14.2%. Both univariate and multivariate Cox regression showed that AugSBP and AugMAP parameters were independent predictors for intermediate-term post-TAVR mortality (all p < 0.0001). AugMAP1 < 102.5 mmHg was associated with a 3-fold-increased risk of all-cause mortality 1-year post-TAVR (hazard ratio 3.0, 95%confidence interval 2.0-4.5, p < 0.0001). A univariate model of AugMAP1 surpassed the STS score model in predicting intermediate-term post-TAVR mortality (area under the curve: 0.700 vs. 0.587, p = 0.005; c-index: 0.681 vs. 0.585, p = 0.001).

CONCLUSIONS

Augmented mean arterial pressure provides clinicians with a simple but effective approach to quickly identify patients at risk and potentially improve post-TAVR prognosis.

Left ventricular hypertrophy, diastolic dysfunction and right ventricular load predict outcome in moderate aortic stenosis

Aims

Predictors of progression of moderate aortic valve stenosis (AS) are incompletely understood. The objective of this study was to evaluate the prognostic value of left ventricular hypertrophy (LVH), diastolic dysfunction, and right ventricular (RV) load in moderate AS.

Methods and results

Moderate AS was defined by aortic valve area (AVA), peak transvalvular velocity (V_max) or mean pressure gradient (PG_mean). A total of 131 Patients were divided into two groups according to the number of pathophysiological changes (LVH, diastolic dysfunction with increased LV filling pressures and/or RV load): <2 (group 1); ≥2 (group 2). The primary outcome was survival without aortic valve replacement (AVR). After follow-up of 30 months, the reduction of AVA (-0.06 ± 0.16 vs. -0.24 ± 0.19 cm², P < 0.001), the increase of PG_mean (2.89 ± 6.35 vs 6.29 ± 7.13 mmHg, P < 0.001) and the decrease of the global longitudinal strain (0.8 ± 2.56 vs. 1.57 ± 3.42%, P < 0.001) from baseline to follow-up were significantly more pronounced in group 2. Survival without AVR was 82% (group 1) and 56% (group 2) [HR 3.94 (1.74-8.94), P < 0.001]. Survival without AVR or progression of AS was 77% (group 1) and 46% (group 2) [HR 3.80 (1.84-7.86), P < 0.001]. The presence of ≥2 pathophysiological changes predicted outcome whereas age, comorbidities, LDL-cholesterol did not.

Conclusion

The presence of ≥2 pathophysiological changes is a strong predictor of outcome in moderate AS and may be useful for risk stratification, particularly for scheduling follow-up time intervals and deciding the timing of AVR.

The cardiac computed tomography-derived extracellular volume fraction predicts patient outcomes and left ventricular mass reductions after transcatheter aortic valve implantation for aortic stenosis

BACKGROUND

Transcatheter aortic valve implantation (TAVI) improved outcome of patients with severe aortic valve stenosis (AS). Myocardial fibrosis is associated with AS-related pathological left ventricular (LV) remodeling and predicts cardiovascular mortality after TAVI. The present study aimed to investigate the impact of preoperative extracellular volume (ECV) assessed by computed tomography (CT) on left ventricular mass (LVM) regression and clinical outcomes in severe AS patients after TAVI.

METHODS

We examined 71 consecutive severe AS patients who underwent CT with ECV determination before TAVI. ECV was calculated as the ratio of the change in Hounsfield units in the myocardium and LV blood before and after contrast administration, multiplied by (1-hematocrit). Delayed scan was performed at 5 min after contrast injection. Echocardiography was performed before and 6 months after TAVI. The primary endpoint was heart failure (HF) hospitalization after TAVI. Patients were divided into two subgroups according to the median value of global ECV with 32 % (Low-ECV group: n = 35, and High-ECV group: n = 36).

RESULTS

No significant differences were observed in background characteristics between the 2 groups. However, the preoperative LV ejection fraction and LVM index were similar between the 2 groups, the Low-ECV group had greater LVM index reduction than the High-CV group after 6 months (p < 0.001). Kaplan-Meier curves demonstrated that the High-ECV group had significantly higher rate of HF hospitalization than the Low-ECV group (p = 0.016). In addition, multivariate analyses identified high global ECV as an independent predictor of HF hospitalization (HR 10.8, 95 % confidence interval 1.36 to 84.8, p = 0.024).

CONCLUSION

The low preoperative ECV assessed by CT is associated with the greater LVM regression, and predict better outcome in AS patients after TAVI.

A soft robotic sleeve mimicking the haemodynamics and biomechanics of left ventricular pressure overload and aortic stenosis

Preclinical models of aortic stenosis can induce left ventricular pressure overload and coarsely control the severity of aortic constriction. However, they do not recapitulate the haemodynamics and flow patterns associated with the disease. Here we report the development of a customizable soft robotic aortic sleeve that can mimic the haemodynamics and biomechanics of aortic stenosis. By allowing for the adjustment of actuation patterns and blood-flow dynamics, the robotic sleeve recapitulates clinically relevant haemodynamics in a porcine model of aortic stenosis, as we show via in vivo echocardiography and catheterization studies, and a combination of in vitro and computational analyses. Using in vivo and in vitro magnetic resonance imaging, we also quantified the four-dimensional blood-flow velocity profiles associated with the disease and with bicommissural and unicommissural defects re-created by the robotic sleeve. The design of the sleeve, which can be adjusted on the basis of computed tomography data, allows for the design of patient-specific devices that may guide clinical decisions and improve the management and treatment of patients with aortic stenosis.

New Evidence About Aortic Valve Stenosis and Cardiovascular Hemodynamics

Aortic stenosis (AS) is the most common degenerative valvular disease in western word. In patients with severe AS, small changes in aortic valve area can lead to large changes in hemodynamics. The correct understanding of cardiac hemodynamics and its interaction with vascular function is of paramount importance for correct identification of severe AS and to plan effective strategies for its treatment. In the current review with highlight the importance of pressure recovery phenomenon and valvular arterial impedance as novel tools in the evaluation of patients with aortic stenosis.

Cardiac Remodeling and Disease Progression in Patients With Repaired Coarctation of Aorta and Aortic Stenosis

BACKGROUND

Valvulo-arterial impedance (Zva) is used for assessment of left ventricular (LV) global pressure load in patients with aortic stenosis (AS) and impaired arterial compliance. Because patients with repaired coarctation of aorta (COA) have impaired arterial compliance, we hypothesized that COA patients with greater than or equal to moderate AS (AS-COA group) will have higher Zva, symptomatic progression, and cardiovascular events, as compared to non-COA patients with similar AS severity (AS group).

METHODS

Propensity matching (1:1) of 71 AS-COA and 71 AS patients based on age, sex, body mass index, and aortic valve mean gradient (cohort 1). Of 172 patients, 117 patients (AS-COA [n=62]; AS [n=55]) underwent aortic valve replacement, cohort 2. Cohort 1 was used to assess the relationship between preoperative Zva, cardiac remodeling, and symptomatic progression, while cohort 2 was used to assess the relationship between postoperative Zva, LV mass index regression (reduction in LV mass index after aortic valve replacement), and cardiovascular events.

RESULTS

The AS-COA group had higher Zva (4.2±0.6 versus 3.5±0.4 mm Hg/mL·m², P<0.001), more advanced cardiac remodeling, and higher 5-year incidence of symptomatic progression (85% versus 51%, P<0.001). Preoperative Zva was independently associated with cardiac remodeling (r=0.66, P<0.001) and symptomatic progression (hazard ratio, 1.06 [1.02-1.10], per mm Hg/mL·m² increase in Zva). The AS-COA group had higher postoperative Zva (3.3±0.5 versus 2.4±0.4 mm Hg/mL·m², P<0.001), less robust LV mass index regression at 1-year post-aortic valve replacement, and higher 5-year incidence of cardiovascular events. Postoperative Zva was independently associated with LV mass index regression (r=-0.46, P<0.001) and cardiovascular events (hazard ratio, 1.06 [1.02-1.10], per mm Hg/mL·m² increase in Zva).

CONCLUSIONS

Adults with AS-COA had higher LV global pressure load, cardiac remodeling, symptomatic progression, and cardiovascular events as compared to non-COA patients with similar severity of AS. Zva can identify patients at risk for adverse outcomes, and perhaps should be used for risk stratification with regards to timing of aortic valve replacement.

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

OBJECTIVE

Our objective was to evaluate the impact of various blood pressures (BPs) on coronary perfusion and valvular hemodynamics following aortic valve replacement (AVR).

BACKGROUND

Lower systolic and diastolic (SBP/DBP) pressures from the recommended optimal target range of SBP < 120-130 mmHg and DBP < 80 mmHg after AVR have been independently associated with increased cardiovascular and all-cause mortality.

METHODS

The hemodynamic assessment of a 26 mm SAPIEN 3 transcatheter aortic valve (TAV), 29 mm Evolut R TAV, and 25 mm Magna Ease surgical aortic valve (SAV) was performed in a pulsed left heart simulator with varying SBP, DBP, and heart rate (HR) conditions (60 and 120 bpm) at 5 L/min cardiac output (CO). Average coronary flow (CF), effective orifice areas (EOAs), and valvulo-arterial impedance (Zva) were calculated.

RESULTS

At HR of 60 bpm, at SBP < 120 mmHg and DBP < 60 mmHg, CF decreased below the physiological lower limit with several different valves. Zva and EOA were found to increase and decrease respectively with increasing SBP and DBP. The same results were found with an HR of 120 bpm. The trends of CF variation with BP were similar in all valves however the drop below the lower physiological CF limit was valve dependent.

CONCLUSION

In a controlled in vitro system, with different aortic valve prostheses in place, CF decreased below the physiologic minimum when SBP and DBP were in the range targeted by blood pressure guidelines. Combined with recent observations from patients treated with AVR, these findings underscore the need for additional studies to identify the optimal BP in patients treated with AVR for AS.

Challenges and opportunities in improving left ventricular remodelling and clinical outcome following surgical and trans-catheter aortic valve replacement

Over the last half century, surgical aortic valve replacement (SAVR) has evolved to offer a durable and efficient valve haemodynamically, with low procedural complications that allows favourable remodelling of left ventricular (LV) structure and function. The latter has become more challenging among elderly patients, particularly following trans-catheter aortic valve implantation (TAVI). Precise understanding of myocardial adaptation to pressure and volume overloading and its responses to valve surgery requires comprehensive assessments from aortic valve energy loss, valvular-vascular impedance to myocardial activation, force-velocity relationship, and myocardial strain. LV hypertrophy and myocardial fibrosis remains as the structural and morphological focus in this endeavour. Early intervention in asymptomatic aortic stenosis or regurgitation along with individualised management of hypertension and atrial fibrillation is likely to improve patient outcome. Physiological pacing via the His-Purkinje system for conduction abnormalities, further reduction in para-valvular aortic regurgitation along with therapy of angiotensin receptor blockade will improve patient outcome by facilitating hypertrophy regression, LV coordinate contraction, and global vascular function. TAVI leaflet thromboses require anticoagulation while impaired access to coronary ostia risks future TAVI-in-TAVI or coronary interventions. Until comparable long-term durability and the resolution of TAVI related complications become available, SAVR remains the first choice for lower risk younger patients.