Human Histopathology of Electroanatomic Mapping After Cooled‐Tip Radiofrequency Ablation to Treat Ventricular Tachycardia in Remote Myocardial Infarction

Abstract

Electroanatomic substrate mapping for VT ablation sufficiently identified regions of scar and normal myocardium. Regions with bipolar electrogram amplitudes between 0.5 and 1.5 mV were found to correlate to areas of "intermediate" fibrosis (21-79%) with only remnant strands of myocardial cells and were identified as target region for ablation. Cooled-tip endocardial radiofrequency ablation lead to transmural coagulation necrosis up to a depth of 7.0 mm.

Infarct Tissue Heterogeneity by Magnetic Resonance Imaging Identifies Enhanced Cardiac Arrhythmia Susceptibility in Patients With Left Ventricular Dysfunction

“…Infarcts can have marked spatial heterogeneity, with areas of necrosis interspersed with bundles of viable myocytes, particularly in the border zones and periphery of the infarct. [12][13][14] Tissue heterogeneity in these regions may create areas of slow conduction that generate the substrate for the development of lethal reentrant arrhythmias. 14 -16 In the present study, we examine the utility of ceMRI in identifying patients with increased vulnerability to ventricular arrhythmias.…”

“…The latter mechanism is supported by pathological data. 14,31 The architecture of the infarct border zones can be heterogeneous and nonuniform, and in certain situations, it is the juxtaposition and intermingling of normal and infarcted tissue that likely serves as the substrate for reentrant arrhythmias. 14 -16 Because of the admixture of surviving muscle bundles with collagen in the infarct periphery, the volume of distribution for gadolinium may be significantly less than that in the infarct core, 26 which has densely packed collagen fibers.…”

Role of catheter ablation of ventricular tachycardia associated with structural heart disease

“…According to a preliminary evaluation [23] , areas with bipolar voltage ≥ 1.5 mV are normal, those with bipolar voltage ≤ 0.5 mV are areas of dense scar, whereas areas with a voltage between 0.5 and 1.5 mV are the border zone between necrosis/fibrosis and the normal myocardial tissue. In a post-mortem study, these voltage thresholds correlated very well with histology, since massive (> 80%) fibrosis has been found in areas with voltage < 0.5 mV, while intermediate (21%-79%) and minimal (< 20%) fibrosis has been observed in areas with voltage 0.5-1.5 mV and > 1.5 mV, respectively [26] . Once voltage mapping has been completed, pacing maneuvers are used in the area of dense scar and along the border zone to identify a channel of low voltage and slow conduction, possibly related to the VT.…”

Cardiac Magnetic Resonance and Myocardial Viability: Why Is It so Important?

“…40 Wu et al argued that the presence of microvascular obstruction (residual myocardial perfusion abnormality despite revascularization of the tissue) is an important marker for injury severity. 41 Furthermore, Roses et al established that the expansion of the microvascular obstruction zone is a better long-term prognostic factor compared to the ejection fraction and left ventricular volumes. 42 The MRI examination can determine the area at risk and the infarct size.…”

“…46,47 The notion of peri-infarct zone ("gray zone") was introduced by Schmidt et al The quantification of the peri-infarcted zone can be made by tracing the endo-and epicardial margins in the short-axis sequence and the hypersignal region. 41 The infarct nucleus is defined as the region from the myocardium with a signal intensity higher than 50%. The gray zone is described as a zone with greater signal intensity than that of the remote myocardium but lower than 50%.…”