High-Resolution Mapping of Post-Infarction Reentrant Ventricular Tachycardia: Electrophysiological Characterization of the Circuit
Background—In-vivo description of ventricular tachycardia (VT) circuits is limited by insufficient spatiotemporal resolution. We utilized a novel high-resolution mapping technology to characterize the electrophysiological properties of the post-infarction reentrant VT circuit.
Methods—In 15 swine, myocardial infarction (MI) was induced by left anterior descending artery balloon occlusion. Animals were studies 6-8 weeks after MI. Activation mapping of VTs was performed using the RhythmiaTM mapping system. Activation time was based on a combination of bipolar and unipolar electrograms. The response to overdrive pacing from different zones of the circuit was examined.
Results—A total of 56 monomorphic VTs were induced (3.8±2.1 per animal). Among these, 21 (37.5%) were hemodynamically stable and allowed mapping of the circuit. Isthmuses were 16.4±7.2mm long and 7.4±2.8mm wide. Conduction velocities were slowest at the inward curvature into the isthmus "entrance" (0.28±0.2m/sec), slightly faster at the outward curvature "exit" (0.40±0.3m/sec) and nearly normal at the central isthmus (0.62±0.2m/sec). In 3 animals 2 VT morphologies with opposite axis sharing the same isthmus were mapped. Conduction velocities within the shared isthmus were dependent on the activation vector, consistently slower at the proximal curvature. Overdrive pacing from isthmus sites determined by activation mapping was consistent with entrainment criteria for isthmus. However, dimensions of the isthmus defined by entrainment exceeded dimensions of the isthmus measured by activation mapping by 32%±18%.
Conclusions—In post-infarction reentrant VT, conduction velocities are slowest at the proximal and distal curvatures. Entrainment mapping overestimates the true size of the isthmus. High-resolution activation mapping of VT may better guide ablation therapy.
- Received February 8, 2016.
- Revision received April 11, 2016.
- Accepted May 5, 2016.