PRessure-based Evaluation of Disease Improvement in the Course of TAVI (PREDIC-TAVI)

Background and Rationale:

Severe Aortic Stenosis (AS) is characterized by the progressive calcification and narrowing of the aortic valve leaflets, leading to a significant mechanical obstruction in the Left Ventricular Outflow Tract (LVOT). While Transcatheter Aortic Valve Replacement (TAVR) has become the gold standard for high-risk and increasingly intermediate-to-low-risk patients, the clinical response remains heterogeneous. Current procedural success is primarily evaluated using steady-flow metrics such as Mean Pressure Gradient (MG) and Aortic Valve Area (AVA). However, the total workload on the Left Ventricle (LV) is not merely a function of valvular resistance but also involves pulsatile components including arterial compliance, wave reflections, and valvulo-arterial impedance. In many TAVR candidates, concomitant systemic arterial stiffness and reduced vascular compliance complicate the hemodynamic profile, making traditional gradients insufficient to fully characterize the true obstructive load and ventricular performance, e.g. in certain disease endotypes subgroups "paradoxical" low-flow, low-gradient (LFLG) phenotypes.

The PREDIC-TAVI study utilizes state-of-the-art wave mechanics to provide a granular assessment of the cardiovascular system's response to TAVR:

1. Wave Intensity Analysis (WIA): By analyzing simultaneous changes in pressure and flow (or flow-surrogates), WIA identifies the energy flux of forward-traveling waves (Forward Compression Waves [FCW] generated by LV ejection and Forward Expansion Waves [FEW] during relaxation) and backward-traveling waves (Backward Compression Waves [BCW] reflected from the systemic tree and the stenotic valve).
2. Reservoir-Excess Pressure Analysis (REPA): This method decomposes the measured aortic pressure waveform into a reservoir pressure (Pr), reflecting the global arterial storage and compliance dynamics, and an excess pressure (Pxs), representing the dynamic, wave-related component of the pulse. Parameters such as P-infinity (Pinf) serve as proxies for microcirculatory closing pressures.

Study Design and Procedural Methodology: This is a prospective, single-center, observational cohort study. Consecutive patients (aged 60-90 years) with a multidisciplinary "Heart Team" diagnosis of severe AS and a clinical indication for TAVR will be enrolled. The study employs a high-fidelity "pressure-only" approach for hemodynamic analysis. During the routine TAVR procedure, proximal aortic pressure waveforms will be recorded via fluid-filled catheters at a minimum sampling rate of 100 Hz. Recordings will be captured at two specific time points:

• Baseline (Pre-Implantation): Immediately prior to valve deployment under stable hemodynamic conditions.
• Post-Implantation: Following valve deployment and stabilization. Data acquisition occurs within the standard clinical workflow, requiring no additional invasive maneuvers. Waveforms are analyzed offline using standardized signal-processing algorithms (Savitzky-Golay filtering, beat segmentation, and diastolic exponential fitting) to derive delta-WIA and delta-REPA metrics.

Longitudinal Follow-up and Clinical Endpoints: The study aims to correlate acute intra-procedural hemodynamic changes with multidimensional clinical outcomes at three distinct follow-up intervals:

1. 1-Month Follow-up (30 ± 5 days):
2. 6-Month Follow-up (180 ± 14 days):
3. 12-Month Follow-up (1 Year ± 3 weeks):

Primary Outcome Measures:

• Clinical Improvement: Assessed via the change in health-related quality of life using the EuroQol 5-Dimension 5-Level (EQ-5D-5L) index scores and Visual Analog Scale (VAS).
• Major Adverse Cardiovascular Events (MACE): A composite of all-cause mortality, stroke (major/minor), myocardial infarction, and unplanned hospitalizations due to heart failure or valve dysfunction, classified according to Valve Academic Research Consortium 3 (VARC-3) criteria. All cause mortality and any ED admissions are separately assessed.

Statistical Analysis Plan: The relationship between hemodynamic deltas and clinical outcomes will be analyzed using Pearson/Spearman correlations and linear regression. To account for the longitudinal follow-up and baseline clinical covariates (e.g., age, gender, comorbidities, and baseline LVEF), Generalized Linear Mixed Models (GLMM) will be utilized. Receiver Operating Characteristic (ROC) curves and Area Under the Curve (AUC) values will be calculated to determine the predictive power of wave-based metrics for 1-year MACE. OR/HR will be calculated for endpoints.

Sample Size Rationale: Based on current literature, TAVR is expected to significantly increase FCW energy and Pxs. To detect a moderate correlation (r=0.35) between these changes and the EQ-5D-5L index with 80% power and 5% alpha, a minimum of 62 patients is required. To ensure robust 1-year MACE prediction (assuming a 28% event rate in the TAVR population per SWEDEHEART registry data) and to account for technical or follow-up attrition, a target enrollment of at least 100 consecutive patients is established.

Scientific Contribution: The PREDIC-TAVI-IMAEH study seeks to define a new "physiological success" signature for TAVR. By moving beyond static gradients, this research aims to improve the diagnostic and prognostic algorithms for severe AS, providing clinicians with sensitive markers to optimize valve deployment and better anticipate the recovery trajectory of complex cardiovascular patients.