Background:
Chronic respiratory diseases are the third-leading cause of death worldwide. Due to shared symptoms with cardiovascular diseases and the possibility of their inaccurate attribution, pulmonary diseases are often undiagnosed.

Objective:
The objective of this study was to investigate the prevalence of chronic respiratory diseases among symptomatic patients in whom suspected coronary artery disease (CAD) had been ruled out.

Methods:
50 patients with chest discomfort or dyspnoea were recruited after invasive coronary angiography (ICA) excluded CAD. Lung function testing, including spirometry and diffusion measurements, was performed on all patients. Standardized assessments of symptoms (CCS chest pain, mMRC score, CAT score) were conducted at baseline and 3-month follow-up.

Results:
Chronic respiratory diseases were identified in 14% of patients, with chronic obstructive ventilation disorders being prevalent in 6%. Patients with normal functional test results showed a significant improvement in symptoms at 3-month follow-up (mean mMRC 0.70 to 0.33, p = 0.06; median CAT 8 to 2, p = 0.01), whereas those with pulmonary findings showed non-significant alterations or unchanged symptoms (mean mMRC 1.14 to 0.71, p = 0.53; median CAT 6 to 6, p = 0.52).

Conclusion:
A considerable number of patients who were initially suspected of having coronary artery disease were identified with chronic respiratory disorders and showed persistent symptoms during follow-up.