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Personalized computational cardiac models are emerging as an important tool for studying cardiac arrhythmia mechanisms, and have the potential to become powerful instruments for guiding clinical anti-arrhythmia therapy. In this article, we present the methodology for constructing a patient-specific model of atrial fibrosis as a substrate for atrial fibrillation. The model is constructed from high-resolution late gadolinium-enhanced magnetic resonance imaging (LGE-MRI) images acquired in vivo from a patient suffering from persistent atrial fibrillation, accurately capturing both the patient's atrial geometry and the distribution of the fibrotic regions in the atria. Atrial fiber orientation is estimated using a novel image-based method, and fibrosis is represented in the patient-specific fibrotic regions as incorporating collagenous septa, gap junction remodeling, and myofibroblast proliferation. A proof-of-concept simulation result of reentrant circuits underlying atrial fibrillation in the model of the patient's fibrotic atrium is presented to demonstrate the completion of methodology development.

Background Late gadolinium enhanced (LGE) MRI is the gold standard test for non-invasive detection of myocardial scar. Many VT ablation candidates who would derive benefit from LGE MRI do not undergo cardiac MRI largely due to image artifacts generated by cardiac devices. A recent study reported improved LGE MRI for patients with implantable cardiac devices using a custom-made wideband adiabatic inversion-recovery (IR) pulse [1]. The purpose of this study was to implement off-resonanceinsensitive LGE MRI based on commercially available IR pulse for imaging ventricular scar without image artifacts induced by cardiac devices. Methods We implemented cardiac-device-insensitive LGE MRI by modifying a commercially available adiabatic IR pulse (Siemens_external_RF_file:IR10240H180.IR180_36B1_2) with the following parameters:b = 750radians/s, μ =1 0 (dimensionless), pulse duration = 6.1 ms. We designed the IR pulse to achieve B1 +o f 1050 Hz and 779 Hz at 1.5T and 3T, respectively, in order to achieve adiabaticity within the RF amplifier and SAR limits. Standard and wideband LGE MRI pulse sequences were evaluated in phantoms and seven canines (with ICD placed 10 cm away from the heart) with myocardial lesions created by radio-frequency ablation at 3T, as well as in one patient with ICD at 1.5T. Both LGE MRI pulse sequences used the same standard imaging parameters, except for the IR pulse. Two readers independently evaluated the image quality(1-5;worst-best) and artifact level(1-5;least-most) using a 5-point Likert scale. After administration of TTC, animals were euthanized for heart removal and gross pathology.

Catheter ablation is effective in symptomatic, drug refractory atrial fibrillation and can result in cure but success rates vary significantly with recurrences ranging from 40-86%. In the months following ablation, LA wall scarring on late gadolinium enhancement (LGE) is useful for determining the location and extent of injury and has been used to guide follow up ablation to 'close the gaps' after unsuccessful PVAI. More recently, imaging acute ablation injury using double inversion recovery (DIR) sequences has been shown feasible and has generated interest for its potential clinical value in guiding ablations.