Associations of electrocardiographic P-wave characteristics with left atrial function, and diffuse left ventricular fibrosis defined by cardiac magnetic resonance: The PRIMERI study

BACKGROUND: Abnormal P-terminal force in lead V₁ (PTFV₁) is associated with an increased risk of heart failure, stroke, atrial fibrillation, and death. OBJECTIVE: Our goal was to explore associations of left ventricular (LV) diffuse fibrosis with left atrial (LA) function and electrocardiographic (ECG) measures of LA electrical activity. METHODS: Patients without atrial fibrillation (n = 91; mean age 59.5 years; 61.5% men; 65.9% white) with structural heart disease (spatial QRS-T angle ≥105° and/or Selvester QRS score ≥5 on ECG) but LV ejection fraction >35% underwent clinical evaluation, cardiac magnetic resonance, and resting ECG. LA function indices were obtained by multimodality tissue tracking using 2- and 4-chamber long-axis images. T₁ mapping and late gadolinium enhancement were used to assess diffuse LV fibrosis and presence of scar. P-prime in V₁ amplitude (PPaV₁) and duration (PPdV₁), averaged P-wave-duration, PR interval, and P-wave axis were automatically measured using 12 SLTM algorithm. PTFV₁ was calculated as a product of PPaV₁ and PPdV₁. RESULTS: In linear regression after adjustment for demographic characteristics, body mass index, maximum LA volume index, presence of scar, and LV mass index, each decile increase in LV interstitial fibrosis was associated with 0.76 mV∗ms increase in negative abnormal PTF_V1 (95% confidence interval [CI] -1.42 to -0.09; P = .025), 15.3 ms prolongation of PPdV₁ (95% CI 6.9 to 23.8; P = .001) and 5.4 ms prolongation of averaged P-duration (95% CI 0.9-10.0; P = .020). LV fibrosis did not affect LA function. PPaV₁ and PTFV₁ were associated with an increase in LA volumes and decrease in LA emptying fraction and LA reservoir function. CONCLUSION: LV interstitial fibrosis is associated with abnormal PTF_V1, prolonged PPdV₁, and P-duration, but does not affect LA function.