SPC365

Electrophysiological characterization of tachycardia circuit and underlying substrate in atypical atrial flutters

Session: SESSÃO DE COMUNICAÇÕES ORAIS 12 - AVANÇOS EM ABLAÇÃO: TÉCNICAS, FERRAMENTAS E RESULTADOS
Speaker: Guilherme Portugal

Congress: CPC 2025
Topic: C. Arrhythmias and Device Therapy
Theme: 06. Supraventricular Tachycardia (non-AF)
Subtheme: 06.1 Supraventricular Tachycardia (non-AF) - Pathophysiology and Mechanisms
Session Type: Comunicações Orais
FP Number: ---
Authors: Guilherme Portugal; Mariana Pereira; Pedro Silva Cunha; Bruno Valente; Helder Santos; Sofia Jacinto; Ines Neves; Rui Cruz Ferreira; Mario Martins Oliveira

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<p style="text-align:start"><span style="font-size:medium"><span style="font-family:Calibri,sans-serif"><span style="color:#000000">Introduction</span></span></span></p>

<p style="text-align:start"><span style="font-size:medium"><span style="font-family:Calibri,sans-serif"><span style="color:#000000">Atypical atrial flutter (AFL) is an uncommon arrythmia due to an underlying atrial electrophysiological substrate which may be idiopathic or related to previous interventions. Data is lacking on the electrophysiological characterization of AFL circuits, which may help in the understanding of this complex arrhythmia.</span></span></span></p>

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<p style="text-align:start"><span style="font-size:medium"><span style="font-family:Calibri,sans-serif"><span style="color:#000000">Methods</span></span></span></p>

<p style="text-align:start"><span style="font-size:medium"><span style="font-family:Calibri,sans-serif"><span style="color:#000000">Consecutive patients submitted to atypical atrial flutter ablation in a tertiary center were included. Only patients where the entire circuit was mapped were included in the final analysis. </span></span></span></p>

<p style="text-align:start"><span style="font-size:medium"><span style="font-family:Calibri,sans-serif"><span style="color:#000000">The activation map was divided in 10 isochronal segments; after analysis of the tachycardia circuit, each segment was categorized as common isthmus or as outer loop. The propagation velocity was manually calculated for each segment. In addition, the presence of atrial substrate, defined as bipolar voltage &lt;0.3 mV, was assessed for each tachycardia component and calculated as a percentage of the total area of the circuit segment.</span></span></span></p>

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<p style="text-align:start"><span style="font-size:medium"><span style="font-family:Calibri,sans-serif"><span style="color:#000000">Results</span></span></span></p>

<p style="text-align:start"><span style="font-size:medium"><span style="font-family:Calibri,sans-serif"><span style="color:#000000">25 AFL circuits in 21 patients were analyzed, with a mean cycle length 280 +/- 46 ms. All 21 patients had circuits related with low atrial voltage areas, which were due to previous intervention in 54% and spontaneous in 46%. The mechanism was microreentry in 12% and macroreentry in 88%, with 3577+/-1911 points per activation map. The tachycardia was mapped to the left atrium in 72%, right atrium in 24% and was biatrial in 1 case; 11 circuits were single-loop, 14 were double loop and 1 was triple-loop. A total of 355 AFL segments were assessed of which 56 corresponded to the common isthmus and 299 to an outer loop; each circuit had a mean of 4 isthmus and 6 outer loop segments. Wavespeed velocity was 0.56+/- 0.37 m/s and did not differ between isthmus and outer loop (0.54 vs 0.56, p=0.73); a representative chart plotting the wavespeed for the different circuit isochrones is presented on Figure 1. The mean length of the tachycardia isthmus was 56 +/-27 mms vs 116 +/-42 mms for the outer loop (p&lt;0.001). At multivariate regression analysis, critical isthmus segments were predicted by a smaller isochronal area (OR 1.15 CI 1.10-1.20, p&lt;0.001) and higher percentage of fibrosis (OR 7.3, CI 1.2-45, p=0.03).</span></span></span></p>

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<p style="text-align:start"><span style="font-size:medium"><span style="font-family:Calibri,sans-serif"><span style="color:#000000">Conclusions</span></span></span></p>

<p style="text-align:start"><span style="font-size:medium"><span style="font-family:Calibri,sans-serif"><span style="color:#000000">AFL circuits are invariably related to atrial substrate. Most circuits are complex, consisting of 2 or more loops. The critical isthmus has similar wavespeed velocity to the remaining tachycardia circuit, but is more commonly found in narrow areas with high percentage of atrial fibrosis.</span></span></span></p>