Background – Cavotricuspid isthmus-dependent (CTI-dependent) atrial flutter (AFL) is the most common atrial macroreentrant tachycardia. It is usually associated with characteristic electrocardiographic (ECG) findings. Which are comprised of negative flutter waves with a sawtooth pattern in the inferior leads and positive P-waves in V1 (type I ECG). However, in the absence of these characteristics (type II ECG) CTI AFL revealed by electrophysiology study (EPS) has been described.

Purpose and Methods – We investigated characteristics and predictors for CTI-dependent AFL in patients with type II ECG. 

Results – We included 383 patients with AF in ECG recordings undergoing EPS in our study. Upon hospital admission 268 patients (70%) had a type I ECG and 115 patients (30%) showed a type II ECG. 52 patients (45%) showed a CTI-dependent AFL in EPS despite a type II ECG. These patients were younger (70.1±12.6 vs. 75.4±9.0 years; p=0.014), more often male (9 (17%) vs. 26 (41%); p=0.005), suffered more often from arterial hypertension (36 (69%) vs 54 (86%); p=0.033) and had more often heart surgery (16 (31%) vs. 8 (13%); p=0.018) compared to patients with non CTI-dependent AFL. Regarding ECG characteristics, patients with CTI-dependent and Type II ECG showed a longer atrial cycle length (CL) compared to patients with non CTI-dependent AFL (250.6±44.1 vs. 231.1±49.9 ms; p=0.015). A cut-off Cl of 245ms revealed a sensitivity of 0.694 and a specificity of 0.627 to discriminate CTI- and non CTI-dependent AFL. The strongest predictor for a CTI-dependent AFL in patients with type II ECG in multivariate logistic regression analyses was atrial CL >245 ms (OR 2.465; 95% CI 1.066 – 5.701; p=0.035) and male gender (OR 2.631; 95% CI 1.023 – 6.765; p=0.045).

Conclusion – Despite type II ECG there is a considerable amount of patients with CTI-dependent AFL. These patients were younger, predominantly male and showed more often arterial hypertension and prior heart surgery in medical history. An atrial CL >245 ms and male gender were identified as independent predictors for a CTI-dependent AFL in patients with type II ECG.