{'fraction_non_alphanumeric': 0.025866813428728673, 'fraction_numerical': 0.006053935057787562, 'mean_word_length': 5.492857142857143, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 1, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Is pulmonary artery wedge pressure a Fib in A‐Fib?

Heisenberg’s uncertainty principle states that there is a fundamental limit to the precision which we can obtain knowledge about the physical properties of a quantum particle, specifically stating one cannot precisely know the position and momentum of a quantum particle.1 In the study by Dickinson et al.2 in this issue of the Journal, the authors provide their own version of a haemodynamic uncertainty principle by studying the effects that atrial fibrillation (AF) has on the relationship between measured pulmonary artery wedge pressure (PAWP) and left ventricular end-diastolic pressure (LVEDP). The question of the accuracy of PAWP as a surrogate for left ventricular (LV) filling pressure is not one without important clinical implications. A common reason to perform a haemodynamic study is to establish the diagnosis and aetiology of pulmonary hypertension (PH). Per the European Society of Cardiology/European Respiratory Society and American College of Cardiology/American Heart Association guidelines, the presence of elevated LV filling pressures (>15 mmHg) establishes the diagnosis of post-capillary PH (or PH due to left heart disease).3,4 Conversely, the absence of elevated LV filling pressures establishes the presence of pre-capillary PH. The distinction between these two different (though sometimes overlapping) physiologies drives therapeutic decision-making. However, the accuracy of PAWP as a LVEDP surrogate in the setting of AF has not been robustly assessed, and Dickinson and colleagues commendably set out to answer that important question. After exclusions, 123 patients without severe mitral valvular disease who underwent simultaneous left and right heart catheterization at their centre were included. Thirty-four patients (28% of