Interatrial block and P-terminal force: a reflection of mitral stenosis severity on electrocardiography

Interatrial block (IAB), a frequently overlooked conduction delay between the atria, is defined as prolonged P-wave on the electrocardiogram (ECG). Previously, IAB has been shown to be an indicator of dilated and impaired left atrial function, and a predictor of both atrial fibrillation and embolic stroke. The study aim was to test the hypothesis that, on ECG, IAB with P-terminal force can reflect the echocardiographic severity of mitral stenosis (MS).

Patients with rheumatic MS who were referred to a single cardiac center for echocardiography between July and October 2009, and who met the study entry criteria (echocardiographically documented rheumatic MS), were invited to participate. Consequently, 116 such patients were studied prospectively, while a group of age- and gender-matched subjects without echocardiographic signs of rheumatic valve involvement served as controls. Transthoracic echocardiography was performed in all subjects.

A positive correlation was observed between IAB (> or = 120 ms) and the mean mitral valve gradient (R = 0.3, p <0.001). A strong negative correlation was also present between the mitral valve area (MVA) and the presence of IAB (R = -0.3, p <0.001). The presence of pulmonary hypertension and a poor NYHA functional class were associated with a high incidence of significant IAB (R = 0.4, p <0.001; R = 0.3, p <0.001, respectively), and there was a strong correlation between IAB and the P-terminal force (p <0.001). Both, the presence of significant IAB and P-terminal force were correlated with a calcific mitral valve (p <0.001). Only the MVA (beta = 0.3; p = 0.008) was a predictor of IAB in multivariate analysis.

A severe mitral gradient, a decreased MVA, an increased pulmonary artery pressure, and a poor NYHA class were shown to correlate with IAB duration and P-terminal force. Significant IAB (> or = 120 ms) and P-terminal force might be considered as a novel indicator of echocardiographic severity and associated complications during the follow up of MS. However, these interrelations must be clarified in further studies.