A rule-based method for predicting the electrical activation of the heart with cardiac resynchronization therapy from non-invasive clinical data

Abstract

Background: Cardiac Resynchronization Therapy (CRT) is one of the few effective treatments for heart failure patients with ventricular dyssynchrony. The pacing location of the left ventricle is indicated as a determinant of CRT outcome.

Objective: Patient specific computational models allow the activation pattern following CRT implant to be predicted and this may be used to optimize CRT lead placement.

Methods: In this study, the effects of heterogeneous cardiac substrate (scar, fast endocardial conduction, slow septal conduction, functional block) on accurately predicting the electrical activation of the LV epicardium were tested to determine the minimal detail required to create a rule based model of cardiac electrophysiology. Non-invasive clinical data (CT or CMR images and 12 lead ECG) from eighteen patients from two centers were used to investigate the models.

Results: Validation with invasive electro-anatomical mapping data identified that computer models with fast endocardial conduction were able to predict the electrical activation with a mean distance errors of 9.2 ± 0.5 mm (CMR data) or (CT data) 7.5 ± 0.7 mm.

Conclusion: This study identified a simple rule-based fast endocardial conduction model, built using non-invasive clinical data that can be used to rapidly and robustly predict the electrical activation of the heart. Pre-procedural prediction of the latest electrically activating region to identify the optimal LV pacing site could potentially be a useful clinical planning tool for CRT procedures.

Keywords: Cardiac resynchronization therapy; Computational models; Electrophysiology; Patient-specific simulations.

Fig. 1

Six electrophysiology models were investigated with the inclusion of scar, functional block in the anterior or posterior regions of the LV, slow septal conduction, and fast endocardial conduction used to determine the importance of these factors in accurately simulating the electrical propagation across the ventricles.

Fig. 2

RV pacing with a six-fold increase in the ventricular endocardium was simulated for the 14CMR cases, with the electrical activation time normalized as a percentage of the QRS duration. The latest activated site is highlighted with a white dot.

Fig. 3

The simulated local activation time normalized as a percentage of the QRS duration (LAT) was compared against the clinical LAT for each of the measured sites in the coronary sinus venous branches for the model with fast endocardial conduction.

Fig. 4

Simulations were run for the 14 CMR cases, with a basic model, inclusion of scar (for cases 9–14), slow septum, fast endocardial conduction, anterior or posterior functional block. Boxplots of the (a) temporal error, (b) distance error, and (c) conduction velocities are shown for each model. The conduction velocities which are between the physiologically plausible range (0.07–0.75 m/s) are highlighted in green.

Fig. 5

(a) CT images were acquired for 4 CRT upgrade patients and were automatically segmented using the Philips model based tool. (b) The EAM from Ensite NavX (white) was mapped to the coronary sinus semi-automatically segmented from the CT images (black). (c) The electrical activation across the ventricles from RV pacing was simulated. (d) The EAM local activation times were mapped onto the model (spheres) and the RMS distance error of the mapped EAM sites onto the models is stated for each case. (e) The LAT as a percentage of the QRS duration was compared between the clinical measurements and the model simulations with a six-fold increased conduction velocity in the ventricular endocardium.

Fig. 6

Simulations were run for the 4 CT cases, with a basic model, slow septum, fast endocardial conduction, anterior or posterior functional block. Boxplots of the (a) temporal error, (b) distance error, and (c) conduction velocities are shown for each model. The conduction velocities which are between the physiologically plausible range (0.07–0.75 m/s) are highlighted in green.