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).