Noncontact Mapping of Ventricular Tachycardia in a Closed‐Chest Animal Model of Chronic Myocardial Infarction

Abstract

Treatment of ventricular tachyarrhythmias in the setting of chronic myocardial infarction requires accurate characterization of the arrhythmia substrate. New mapping technologies have been developed that facilitate identification and ablation of critical areas even in rapid, hemodynamically unstable ventricular tachycardia. A noncontact mapping system was used to analyze induced ventricular tachycardia in a closed-chest sheep model of chronic myocardial infarction. Twelve sheep were studied 96 +/- 10 days after experimental myocardial infarction. During programmed stimulation, 15 different ventricular tachycardias were induced in nine animals. Induced ventricular tachycardia had a mean cycle length of 190 +/- 30 ms. In 12 ventricular tachycardias, earliest endocardial activity was recorded from virtual electrodes, preceding the surface QRS onset by 30 +/- 7 ms. Noncontact mapping identified diastolic activity in ten ventricular tachycardias. Diastolic potentials were recorded over a variable zone, spanning more than 30 mm. Timing of diastolic potentials varied from early to late diastole and could be traced back to the endocardial exit site. Entrainment with overdrive pacing was attempted in nine ventricular tachycardias, with concealed entrainment observed in seven. Abnormal endocardium in the area of chronic myocardial infarction identified by unipolar peak voltage mapping was confirmed by magnetic resonance imaging. These data suggest that induced ventricular tachycardia in the late phase of myocardial infarction in the sheep model is due to macroreentry involving the infarct borderzone. The combination of this animal model with noncontact mapping technology will allow testing of new strategies to cure and prevent ventricular tachycardia in the setting of chronic myocardial infarction.

Comparison of Electroanatomic Contact and Noncontact Mapping of Ventricular Scar in a Postinfarct Ovine Model With Intramural Needle Electrode Recording and Histological Validation

“…Further, the chronic postinfarct ovine model of ventricular scarring is considered a good representation of what occurs clinically in humans. 29 …”

Value of Noncontact Mapping for Identifying Left Ventricular Scar in an Ovine Model

“…These strategies are based on determining the pattern of activation during pacing from various sites near but outside of suspected scar. Scar is thought to be present in the areas bypassed by the activation wavefront (see Figure 1 in Reek et al 11 for a graphic representation of this technique). Therefore, areas of scar would never have the lowest voltage compared with all of the electrograms at that time point.…”

Catheter Ablation of Ventricular Tachycardia by Intramyocardial Injection of Ethanol in an Animal Model of Chronic Myocardial Infarction

“…We are aware of the methodologic limitations of unipolar voltage mapping compared to bipolar voltage mapping with the influence of far‐field sensing leading to inaccuracies when broad‐band unipolar electrograms are used to detect abnormal endocardium. The current study extends our previous experience 30 with voltage mapping based upon the amplitude of virtual unipolar electrograms because ablation lesions were tagged on the map and could be compared with pathology. The unipolar peak voltage map described lesion location accurately compared to pathology.…”

“…Once the left ventricular virtual geometry was established, a unipolar peak‐to‐peak voltage map of the reconstructed left ventricular geometry was generated. Based on our previous observations, 30 a cutoff voltage of >5.3 mV with filter settings of 1.0 to 300 Hz was used to define “normal” myocardium. The low‐voltage area of the infarcted zone was outlined on the virtual left ventricle.…”