F-amplitude, left atrial appendage velocity, and thromboembolic risk in nonrheumatic atrial fibrillation

Background: Reduced left atrial appendage velocity (LAAV) has been identified as a marker for thromboembolism in patients with atrial fibrillation. Hypothesis: It was postulated that electrocardiographic (ECG) F-wave amplitude would correlate with LAAV, and inversely with the risk of thromboembolism in patients with atrial fibrillation. Methods: In all, 53 patients with nonrheumatic (NRAF) and 7 patients with rheumatic (RAF) atrial fibrillation underwent assessment of maximum LAAV, which was correlated to the maximum ECG F-wave voltage from lead V-1 (Fmax). In 450 NRAF patients on neither aspirin nor warfarin, the relationship between Fmax and thromboembolic risk was assessed over an average follow-up of 1.3 years. Results: Fmax did not correlate with LAAV (r = 0.2, p = 0.07). Patients with intermittent atrial fibrillation (n = 123) had smaller Fmax amplitude than patients with constant atrial fibrillation (n = 327) (mean 0.73 vs. 0.88 mV(-1), p = 0.001). Fmax amplitude was not related to a history of hypertension, systolic blood pressure, duration of NRAF, abnormal transthoracic echocardiographic left ventricular (LV) systolic function or left atrial (LA) diameter There was a strong trend for increased LV mass being related to smaller Fmax amplitude after adjusting for body surface area (p = 0.06). Fmax amplitude was not correlated with risk of embolic events, including only those events presumed by a panel of case-blinded neurologists to be cardioembolic. Conclusion: Fmax amplitude in NRAF is smaller in patients with intermittent versus constant AF. It does not correlate with LAAV, LA size, increased LV mass, or systolic dysfunction, hypertension, or risk of embolism. Therefore, Fmax amplitude may not be used as a surrogate for LAAV, or as a measure of thromboembolic risk in NRAF.