P-wave characteristics and histological atrial abnormality.

BACKGROUND: Fibro-fatty transformation is believed to be the leading cause of deteriorated atrial conduction; however, any direct assessment in relation to P-wave characteristics is lacking. We sought to assess P-wave morphology (PWM) and duration (PWD) in relation to histology of the atrial myocardium. OBJECTIVE: Atrial specimens were collected from 11 patients who died from cardiovascular causes (7 men; median age 73 years). METHODS: Tissue samples were taken at the level of superior and inferior PVs, center of posterior left atrial wall, terminal crest (CT) and Bachmann's bundle (BB) for assessment of fibro-fatty tissue extent. Standard 12-lead ECGs in sinus rhythm recorded during hospital stay were used for manual assessment of P-wave. Partial interatrial block (pIAB) was defined as a prolonged (≥ 120 ms) and bimodal P-wave in any lead on 12-lead ECG. RESULTS: The median PWD was 160 (120-200) ms. Fibrosis extent in CT highly correlated to PWD (r=0.914, p<0.001). The combination of fibrosis extent and fatty tissue in BB (16%, range 1%-41%), CT (18%, range 3%-47%) or superior PV (15%, range 6%-24%) correlated to PWD (r=0.627, p=0.039; r=0.795, p=0.003; and r=0.668, p=0.025, respectively). pIAB pattern was observed in 10 subjects; however, it was not associated with either fibrosis or fatty tissue content at any sampling location. CONCLUSIONS: Our findings further support causal association between PWD and the extent of structural abnormalities in the atrial myocardium and the major atrial conduction routes.