Mind the gap: Quantification of incomplete ablation patterns after pulmonary vein isolation using minimum path search

Abstract

Pulmonary vein isolation (PVI) is a common procedure for the treatment of atrial fibrillation (AF) since the initial trigger for AF frequently originates in the pulmonary veins. A successful isolation produces a continuous lesion (scar) completely encircling the veins that stops activation waves from propagating to the atrial body. Unfortunately, the encircling lesion is often incomplete, becoming a combination of scar and gaps of healthy tissue. These gaps are potential causes of AF recurrence, which requires a redo of the isolation procedure. Late-gadolinium enhanced cardiac magnetic resonance (LGE-CMR) is a non-invasive method that may also be used to detect gaps, but it is currently a time-consuming process, prone to high inter-observer variability. In this paper, we present a method to semi-automatically identify and quantify ablation gaps. Gap quantification is performed through minimum path search in a graph where every node is a scar patch and the edges are the geodesic distances between patches. We propose the Relative Gap Measure (RGM) to estimate the percentage of gap around a vein, which is defined as the ratio of the overall gap length and the total length of the path that encircles the vein. Additionally, an advanced version of the RGM has been developed to integrate gap quantification estimates from different scar segmentation techniques into a single figure-of-merit. Population-based statistical and regional analysis of gap distribution was performed using a standardised parcellation of the left atrium. We have evaluated our method on synthetic and clinical data from 50 AF patients who underwent PVI with radiofrequency ablation. The population-based analysis concluded that the left superior PV is more prone to lesion gaps while the left inferior PV tends to have less gaps (p < 0.05 in both cases), in the processed data. This type of information can be very useful for the optimization and objective assessment of PVI interventions.

Software Framework to Quantify Pulmonary Vein Isolation Atrium Scar Tissue

“…Comparing scans, even of the same patient, is a difficult problem, it implies the comparison of two morphologically different shapes and a potentially complicated registration problem, such a limitation was reported on [1]. As seen in Figure 2, the shapes differ in the same patient, however not the physiological characteristics, a patient will have the same number of veins showing.…”

“…Pulmonary vein isolation (PVI) is a common ablation procedure to isolate abnormal electrical signals occurring in the pulmonary veins. A successful ablation produces a lesion encircling the veins and stopping activation propagating from the pulmonary veins to the body of the atrium [1]. Late-gadolineum-enhanced (LGE) cardiac magnetic resonance (CMR) scans are the standard tool for imaging of chronic scar [2].…”

“…There are few available methods to robustly assess CMR ablation lesions, in many cases, visual inspection is required [3]- [5]. In [1], a fully automated approach to quantify the ablation is presented. However, the high variability in pulmonary veins' (PV) morphology limits this approach to common patients with 4 PV configurations, as the method requires a very specific parcellation of the atrium.…”

Applications of multimodality imaging for left atrial catheter ablation

“…Indeed, in many cases, visual inspection rather than quantitative analysis has been used. 83–85 In Nuñez Garcia et al , 86 a fully automated approach to quantify the ablation was presented. However, the variability in pulmonary vein morphology limits this approach to a configuration of four pulmonary veins, as the method requires a very specific parcellation of the atrium.…”

“…( C ) Methods that require full manual intervention. ( D ) The fully automated method by Nunez-Garcia et al , 86 which depends on a very specific parcellation of the atrium. ( E ) Semi-automated approaches.…”