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Substrate Mapping to Detect Abnormal Atrial Endocardium With Slow Conduction in Patients With Atypical Right Atrial Flutter

Jin Long Huang, MD, PhD^_*,, Ching-Tai Tai, MD^_*,, Yenn-Jiang Lin, MD^_*,, Bien-Hsien Huang, MD^_*,, Kun-Tai Lee, MD^_*,, Satoshi Higa, MD^_*,, Yoga Yuniadi, MD^_*,, Yi-Jen Chen, MD, PhD^_*,, Shih-Lin Chang, MD^_*,, Li-Wei Lo, MD^_*,, Wanwarang Wongcharoen, MD^_*,, Chih-Tai Ting, MD, PhD^_*, and Shih-Ann Chen, MD^_*,,_*

^_* Institute of Clinical Medicine and Cardiovascular Research Institute, National Yang-Ming University, Taipei, Taiwan
Cardiovascular Center, Taichung Veterans General Hospital, Taichung, Taiwan
Division of Cardiology, Department of Medicine, Veterans General Hospital-Taipei, Taipei, Taiwan

View larger version (15K): [in a new window]   Figure 1 Definition of a normalized low-voltage zone: ratio of the local peak negative voltage (PNV) of the unipolar electrogram to the maximal PNV of a selected atrial cycle of the entire right atrium.

View larger version (43K): [in a new window]   Figure 2 A schematic example of the protected isthmus bordered by the low-voltage zones (LVZs). Convergence of a voltage gradient was found on both sides of the isthmus.

View larger version (67K): [in a new window]   Figure 3 Voltage maps (A), isopotential maps (B), and unipolar electrograms along the re-entry circuit (C) in a patient with atypical flutter. (A) Normalized peak negative voltage (PNV) distribution of the right atrium (RA) in a posterolateral view. Note that the protected isthmus was found between 2 low voltage zone (LVZ) areas, where the normalized PNV was from 0% to 30%. (B) Activation wavefront of atypical flutter (clockwise upper loop re-entry flutter) passing through the protected isthmus identified by the voltage maps. CT = crista terminalis; IVC = inferior vena cava; SVC = superior vena cava. (C) Unipolar electrograms (Eg) within the isthmus exhibit fragmented electrograms (virtual 3 and 4), indicating there is slow conduction; whereas the unipolar electrograms outside the isthmus exhibit an rS pattern (virtual 1, 2, and 5).

View larger version (84K): [in a new window]   Figure 4 The normalized unipolar voltage maps, conduction block, and activation circuit of atypical atrial flutter (white lines) in 6 patients. Note that the most protected isthmuses were at the posterolateral right atrium near the location of the crista terminalis. LVZ = low voltage zone; PNV = peak negative voltage.

View larger version (8K): [in a new window]   Figure 5 Characteristics of the protected isthmus. (A) Mean peak negative voltage (PNV) inside and outside the isthmus. The PNV is lower inside the isthmus than outside. (B) Conduction velocity was slower inside the isthmus than outside.

View larger version (12K): [in a new window]   Figure 6 Receiver-operating characteristic (ROC) curve analysis predicting the slow conduction of the isthmus using the normalized voltage threshold.