Is electrocardiography a reliable tool for identifying patients with isthmus-dependent atrial flutter?

To verify the reliability of the surface ECG to discriminate between cavotricuspid isthmus-dependent atrial flutter (CTI-AFL) and non-CTI-AFL.

We reviewed the ECGs of 186 consecutive patients who underwent catheter ablation of AFL between January 2004 and January 2008. The ECG pattern was defined typical for CTI-AFL, if F-waves were: (i) dominantly negative in the inferior leads and positive in V1 (CCW) or (ii) dominantly positive in the inferior leads and negative in V1 (CW). At the electrophysiological study (EPS), 138 patients (74.2%) had a CTI-AFL and 48 patients (25.8%) had a non-CTI-AFL. A CTI-AFL was found not only in 90.5% of patients having a typical ECG, but also in 40% of patients having an atypical ECG. Thus, a typical AFL ECG showed a sensitivity of 0.83 and a specificity of 0.75 to predict a CTI-AFL, with a positive predictive value of 90.5% and a negative predictive value of 60%.

Typical AFL ECG is a good predictor of CTI-AFL, and in this case, an ablation procedure can be recommended. On the contrary, an atypical AFL ECG does not rule out a CTI-AFL; so, even in this group of patients, an EPS should not be denied when indicated by the clinical circumstances.