Cesare Corrado

A two-variable model robust to pacemaker behaviour for the dynamics of the cardiac action potential.

Highlights • Simplified cardiomyocyte electrophysiology model optimised for patient specific modelling.• Modified Mitchell and Schaeffer model.• No spurious pacemaker behaviour.• Suitable for parameter fitting.• Consistent leading order APD approximation.

Lesion Index–Guided Ablation Facilitates Continuous, Transmural, and Durable Lesions in a Porcine Recovery Model

Background: The Lesion Index (LSI) is a proprietary algorithm from Abbott Medical combining contact force, radiofrequency application duration, and radiofrequency current. It can be displayed during ablation with the TactiCath contact force catheter. The LSI Index was designed to provide real-time lesion formation feedback and is hypothesized to estimate the lesion diameter. Methods and Results: Before ablation, animals underwent cardiac computed tomography to assess atrial tissue thickness. Ablation lines (n=2–3 per animal) were created in the right atrium of 7 Göttingen mini pigs with point lesions (25 W). Within each line of ablation, the catheter tip was moved a prescribed distance (D/mm) according to 1 of 3 strategies: D=LSI+0 mm; D=LSI+2 mm; or D=LSI+4 mm. Two weeks after ablation, serial sections of targeted atrial tissue were examined histologically to identify gaps in transmural ablation. LSI-guided lines had a lower incidence of histological gaps (4 gaps in 69 catheter moves, 5.8%) than LSI+2 mm lines (7 gaps in 33 catheter moves, 21.2%) and LSI+4 mm lines (15 gaps in 23 catheter moves, 65.2%, P<0.05 versus D=LSI). &Dgr;LSI was calculated retrospectively as the distance between 2 adjacent lesions above the mean LSI of the 2 lesions. &Dgr;LSI values of ⩽1.5 were associated with no gaps in transmural ablation. Conclusions: In this model of chronic atrial ablation, delivery of uninterrupted transmural linear lesions may be facilitated by using LSI to guide catheter movement. When &Dgr;LSI between adjacent lesions is ⩽1.5 mm, no gaps in atrial linear lesions should be expected.

A conduction velocity adapted eikonal model for electrophysiology problems with re-excitability evaluation

HighlightsMulti‐front eikonal model.Propagation Velocity adaptation to the electrical substrate.Mitchell–Schaeffer action potential.Suitable for parameter heterogeneity.Suitable for clinical applications. Graphical abstract Figure. No Caption available. Abstract Computational models of heart electrophysiology achieved a considerable interest in the medical community as they represent a novel framework for the study of the mechanisms underpinning heart pathologies. The high demand of computational resources and the long computational time required to evaluate the model solution hamper the use of detailed computational models in clinical applications. In this paper, we present a multi‐front eikonal algorithm that adapts the conduction velocity (CV) to the activation frequency of the tissue substrate. We then couple the eikonal new algorithm with the Mitchell–Schaeffer (MS) ionic model to determine the tissue electrical state. Compared to the standard eikonal model, this model introduces three novelties: first, it evaluates the local value of the transmembrane potential and of the ionic variable solving an ionic model; second, it computes the action potential duration (APD) and the diastolic interval (DI) from the solution of the MS model and uses them to determine if the tissue is locally re‐excitable; third, it adapts the CV to the underpinning electrophysiological state through an analytical expression of the CV restitution and the computed local DI. We conduct series of simulations on a 3D tissue slab and on a realistic heart geometry and compare the solutions with those obtained solving the monodomain equation. Our results show that the new model is significantly more accurate than the standard eikonal model. The proposed model enables the numerical simulation of the heart electrophysiology on a clinical time scale and thus constitutes a viable model candidate for computer‐guided radio‐frequency ablation.

A work flow to build and validate patient specific left atrium electrophysiology models from catheter measurements

HighlightsLocally personalised atrial electrophysiology.Predictive simulations.Catheter measurements.Clinical time scale.Atrial fibrillation. Graphical abstract Figure. No caption available. ABSTRACT Biophysical models of the atrium provide a physically constrained framework for describing the current state of an atrium and allow predictions of how that atrium will respond to therapy. We propose a work flow to simulate patient specific electrophysiological heterogeneity from clinical data and validate the resulting biophysical models. In 7 patients, we recorded the atrial anatomy with an electroanatomical mapping system (St Jude Velocity); we then applied an S1–S2 electrical stimulation protocol from the coronary sinus (CS) and the high right atrium (HRA) whilst recording the activation patterns using a PentaRay catheter with 10 bipolar electrodes at 12 ± 2 sites across the atrium. Using only the activation times measured with a PentaRay catheter and caused by a stimulus applied in the CS with a remote catheter we fitted the four parameters for a modified Mitchell–Schaeffer model and the tissue conductivity to the recorded local conduction velocity restitution curve and estimated local effective refractory period. Model parameters were then interpolated across each atrium. The fitted model recapitulated the S1–S2 activation times for CS pacing giving a correlation ranging between 0.81 and 0.98. The model was validated by comparing simulated activations times with the independently recorded HRA pacing S1–S2 activation times, giving a correlation ranging between 0.65 and 0.96. The resulting work flow provides the first validated cohort of models that capture clinically measured patient specific electrophysiological heterogeneity.

Cardiac CT assessment of tissue thickness at the ostium of the left atrial appendage predicts acute success of radiofrequency ablation

Tissue thickness at the site of ablation is a determinant of lesion transmurality. We reported the feasibility, safety, and efficacy of longstanding persistent atrial fibrillation ablation, incorporating deliberate left atrial appendage (LAA) isolation and occlusion, and identified systematic differences in ostial LAA tissue thickness in a matched cohort of cadaveric specimens.

Personalization of Atrial Electrophysiology Models from Decapolar Catheter Measurements

A novel method to characterize biophysical atria regional ionic models from multi-electrode catheter measurements and tailored pacing protocols is presented. Local atria electrophysiology was described by the Mitchell and Schaeffer 2003 action potential model. The pacing protocol was evaluated using simulated bipolar signals from a decapolar catheter in a model of atrial tissue. The protocol was developed to adhere to the constraints of the clinical stimulator and extract the maximum information about local electro-physiological properties solely from the time the activation wave reaches each electrode. Parameters were fitted by finding the closest parameter set to a data base of 3125 pre computed solutions each with different parameter values. This fitting method was evaluated using 243 randomly generated in silico data sets and yielded a mean error of \(\pm 10.46\,\%\) error in estimating model parameters.