Algorithm for cavo-tricuspid isthmus flutter on surface ECGs: the ACTIONS study

Abstract

ObjectiveCavo-tricuspid isthmus atrial flutter (CTI-AFL) is an important arrhythmia to recognise because there is a highly effective and relatively low-risk ablation strategy. However, clinical experience has demonstrated that providers often have difficulty distinguishing AFL from atrial fibrillation.MethodsWe developed a novel ECG-based three-step algorithm to identify CTI-AFL based on established CTI flutter characteristics and verified on consecutive ablation cases of typical flutter, atypical flutter and atrial fibrillation. The algorithm assesses V1/inferior lead F-wave concordance, consistency of P-wave morphology and the presence of isoelectric intervals in the inferior leads. In this observation study, the algorithm was validated on a cohort of 50 second-year medical students. Students were paired in a control and experimental group, and each pair received 10 randomly selected ECGs (from a pool of 50 intracardiac electrogram-proven CTI-AFL and 50 AF or atypical AFL cases). The experimental group received a cover sheet with the CTI algorithm, and the control group received no additional guidance.ResultsThere was a statistically significant difference in the mean number of correctly identified ECGs among the students in the experimental and control groups (8.12 vs 5.68, p<0.001). Students who used the algorithm correctly identified 2.44 more ECGs as being CTI-AFL or not CTI-AFL. Using the electrophysiology study as the gold standard, the algorithm had an accuracy of 81%, sensitivity of 81%, specificity of 82%, positive predictive value of 78% and negative predictive value of 84% in identifying CTI-AFL.ConclusionWe developed a three-step ECG algorithm that provides a simple, sensitive, specific and accurate tool to identify CTI-AFL.

Atrial fibrillation and atrial flutter – the state of the art. Part 1

“…The 2 mechanisms may coexist or transform from one into another. AFL can be classified as cavotricuspid isthmus (CTI)-dependent, which accounts for more than 90% of AFL, or atypical when the mechanism does not include the CTI [3]. In the CTI-dependent AFL, a reentrant circuit is in the right atrium, and the CTI between the inferior vena cava ostium and the tricuspid valve is the region of delayed conduction, which is critical for sustaining arrhythmia.…”