The endless fascination of right typical atrial flutter: can we predict its occurrence?
Author: Claudio Tondo
Centro Cardiologico Monzino Istituto di Ricovero e Cura a Carattere Scientifico - Dept. of Biomedical, Surgical and Dentistry Sciences, University of Milan, Centro Cardiologico Monzino Italy
In this issue of the Journal, Rickman et (1) al. take us into a new journey across the landscape of the cavo-tricuspid dependent atrial flutter (AFL) by enriching the old concepts with a novel parameter, i.e. right atrial collision time (RACT), whose role is to predict the occurrence of right common atrial flutter. Cavo-tricuspid dependent AFL has been extensively investigated in the last few decades and it is well also known its association with atrial fibrillation (AF). (2-5). The chance for the development of right AFL is strictly related to changes in functional conduction properties of the atrial myocardium which are greatly influenced by fibrotic/scar tissue and increased atrial volume. If these circumstances take place, reduction in conduction velocity can favor a macro-reentry circuit with the wavefront that does not meet its refractory tail and perpetuate the arrhythmia. Therefore, the time required to traverse the entire circuit is related to the circuit’s functional properties. Constant pacing from the coronary sinus os is a well-recognized surrogate for the calculation of the collision time of the two wavefronts traveling the circuit in counterclockwise and clockwise direction.
Rickman et al. (1) have used this modality of pacing for investigating whether the collision time of the two wavefronts on the lateral wall of the right atrium could predict the occurrence of typical atrial flutter. For this purpose, the authors have designed a prospective study including a sample size of 98 patients, 41 having AFL and 57 as controls. The main findings were that patients with AFL were older (64.7±9.7 vs 52.4±16.8 years) and more often male and with significantly longer mean RACT (132.6±17.3 ms vs 99.1±11.6 ms) (p<0.001).
Moreover. a RACT cut-off of 115.5 ms had a sensitivity and specificity of 92.7% and 93.0% respectively for diagnosis of AFL and an ROC curve indicated an AUC of 0.96 (95% CI: 0.93-1.0, p<0.01). Based on these premises, RACT could be utilized as new marker for the propensity of developing typical AFL Needless to remind that patients with AFL also showed longer P wave duration, larger right and left atrium volumes and higher rate of comorbidities. Really and truly, these findings are not unexpected. On the other hand, on multivariate analysis only RACT was independently associated with atrial flutter patients (OR 1.6 (1.1 – 2.4) p = 0.03).