The timing of the P-wave in V1-V6 precordial transition allows to identify the mechanism of right atrial tachycardia
M Marchetti, A Luca, M Le Bloa, C Teres, C Ascione, M Pagnoni, J Solana Munoz, G Domenichini, E Pruvot, P PascaleAbstract
Background
Right atrial tachycardia (AT) is a commonly addressed condition in electrophysiology (EP). Yet, correct 12-lead ECG-based discrimination of cavotricuspid isthmus-dependent AT (CTI-AT) from atypical right atrial AT (non-CTI right AT) can be challenging in some cases and impact procedural planning. Precordial transition has been described in CTI-AT but whether the timing of the P-wave provides additional insights into the mechanism of right AT has not been studied.
Purpose
To assess whether precordial P-wave pattern and timing of polarity variation help discriminate non-CTI right AT from clockwise or counterclockwise CTI-AT.
Methods
12-lead electrocardiograms (ECGs) and EP studies of patients who underwent right AT ablation were retrospectively reviewed. Consecutive patients who displayed unmasked P-waves in precordial leads and in whom the mechanism of AT was proved during EP study were included. Patients were classified in three groups of same size: 1) non-CTI dependent right AT, 2) counterclockwise CTI-AT (ccwCTI-AT) and 3) clockwise CT-AT (cwCTI-AT). Precordial P-wave transition was defined as a gradual or abrupt polarity change of the P-wave with progression across the precordium from V1 to V6. Precordial polarity transition was considered synchronous when peak or nadir of P-wave occurred simultaneously in V1-V6 or, asynchronous when it occurred with a time gap of > 20 ms. Precordial ECG patterns and timings of polarity change were compared among groups.
Results
Among 62 patients (24% women, mean age 62.5 years), 23 had non-CTI right AT, 21 ccwCTI-AT and 18 cwCTI-AT. P-wave was negative in V1 in 96% (22/23) and 78% (14/18) of cases with non-CTI right AT and cwCTI-AT respectively. P-wave was positive in V1 in 100% (21/21) of ccwCTI-AT. Precordial V1-V6 P-wave transition was observed in 96% (22/23), 100% (21/21) and 89% (16/18) of patients with non-CTI right AT, ccwCTI-AT and cwCTI-AT, respectively. A transition pattern ‘negative P-wave in V1 to positive P-wave in V6’ was observed in 91% (21/23) of non-CTI right AT and 66% (12/18) of cwCTI-AT, while 100% (21/21) of patients with ccwCTI-AT had an opposite precordial transition pattern with positive P-wave in V1 to negative P-wave in V6. The timing of the P-wave precordial transition was asynchronous in 95% (35/37) of CTI-AT cases (100% in ccwCTI-AT and 88% in cwCTI-AT), while it was synchronous in 95% (21/22) of non-CTI right AT; p<0.00001.
Conclusion
Among patients with right AT displaying a precordial transition on 12-lead ECG, an asynchronous transition is highly specific of CTI-dependent AT while the identification of a synchronous V1-V6 precordial transition clearly points towards non-CTI-dependent right AT. This might improve 12-lead ECG based diagnosis of right AT mechanism and allow adequate ablation procedural planning.Figure 1.