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Atrial fibrillation (AF) is associated with atrial remodelling, hemodynamic stress, and complex cardiopulmonary interactions. While natriuretic peptides and echocardiographic abnormalities are established markers of AF-related substrate, the contribution of spirometry changes, as a landmark of pulmonary impairment, remains less clearly defined. This study evaluated whether AF is associated with an integrated cardiopulmonary profile characterized by altered spirometry, increased NT-proBNP, and conventional echocardiographic markers of left atrial structure and function.

We performed a retrospective, single-center observational study based on an existing clinical database of adult patients referred for 24 h 12-lead Holter ECG monitoring because of palpitations and/or chest pain. None of the included patients had a previously documented diagnosis of atrial fibrillation before Holter monitoring. Because a single 24 h Holter recording cannot establish spontaneous termination or long-term temporal pattern with certainty, AF documented for the first time during this recording is referred to throughout as "newly detected AF" rather than "paroxysmal AF". During Holter monitoring, no ECG changes suggestive of myocardial ischemia were detected. From 536 records of patients without previously known AF who underwent 24 h 12-lead Holter ECG monitoring for palpitations and/or chest pain, 164 patients were retained for the main comparison, including 48 with newly detected paroxysmal AF and 116 without AF. Demographic, biochemical, spirometric, and echocardiographic variables were analyzed. The main respiratory parameters were forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), and peak expiratory flow (PEF). NT-proBNP was the primary biomarker, while conventional left atrial structural and functional variables were used for echocardiographic assessment.

NT-proBNP was markedly higher in the AF group (684.5 vs. 62.3 pg/mL, p = 0.001), even when accounting for confounders like age, CKD, or CPD, showing by far the largest between-group difference among the biomarkers assessed (formal discrimination statistics such as ROC/AUC were not computed). The exploratory inflammatory markers assessed (hs-CRP, neutrophil/lymphocyte ratio, homocysteine) showed only modest, non-significant differences. Conventional echocardiographic parameters did not differ significantly between groups. In the strict complete-case comparison, spirometric indices did not reach statistical significance; however, preliminary project-level analysis showed lower FVC, FEV1, and PEF in AF patients, but without supporting the COPD diagnosis, and exploratory correlations suggested a relationship between spirometric performance and left atrial function.

In this cohort, AF was most strongly associated with NT-proBNP, while the respiratory signal was weaker but directionally consistent with a broader cardiopulmonary phenotype. These findings do not support spirometry or NT-proBNP as stand-alone diagnostic tools for AF. However, when interpreted alongside traditional AF risk factors and symptoms, elevated NT-proBNP with concordant spirometric impairment may represent a hypothesis-generating additive signal supporting longer or repeated rhythm monitoring beyond 24 h in selected patients with suspected AF; this additive value was not formally tested against clinical models alone and requires prospective confirmation.