Diagnostic usefulness of spiroergometry and risk factors of long -COVID in patients with normal left ventricular ejection fraction
Authors: Bielecka-Dabrowa A M , Sakowicz A , Banach M , Maciejewski M , Gryglewska K 
Published: October 2022

Abstract

Background
Recent evidence has shown that patients with acute SARS-CoV-2 infection might present symptoms of infection a long time after a recovery.

Purpose
To investigate the risk factors and assess the utility of spiroergometry parameters in differential diagnosing patients presenting the symptoms (dyspnea, fatique, pain in chest, muscle pain, cognitive impairment, taste and smell disturbances) persisting for a few months after recovery from COVID 19 (symptoms of long COVID).

Methods and results
The 146 patients (pts) with normal left ventricular ejection fraction and without respiratory diseases, hospitalised in Cardiology Department recovering from COVID-19 at three to six months after confirmed diagnosis were included. The clinical examination, laboratory results, echocardiography using Vivid E95–GE Healthcare, non-invasive body mass analysis using Body Composition Analyzer (Tanita Pro), spiroergometry using The MetaSoft® Studio application were analyzed. The subjects were divided into the two following groups: group demonstrating long COVID symptoms (i.e. suffering from one of the following dyspnea, fatique, pain in chest, muscle pain, cognitive impairment, taste or smell disturbances) [N=44 pts] and the group without long COVID symptoms [N=102 pts]. Pts with long COVID symptoms presented significantly higher age (58 versus [vs] 44 years; p&lt;0.0001), higher metabolic age (53 vs 45 years; p=0.01), higher left atrial diameter (37 vs 35 mm; p=0.04), higher left ventricular mass index (LVMI) (83 vs 74 g/m2, p=0.03), higher E/E' (7.3 vs 6; p&lt;0.001) compared to control group. In CPET long COVID pts presented lower forced vital capacity (FVC) (3.6 vs 4.3 L; p=0.009), lower maximal oxygen consumption measured during incremental exercise indexed per kilogram (VO2max) (21 vs 23 ml/min/kg; p=0.04), lower respiratory exchange ratio (RER) (1.0 vs 1.1; p=0.04); lower forced expiratory volume in one second (FEV1) (2.9 vs 3.25 L; p=0,03); higher ratio of forced expiratory volume in one second to forced vital capacity (FEV1/FVC) (106 vs 100%; p=0.0002) – Figure 1, there were no significant changes in electrocardiogram between groups. The laboratory results pointed that pts with long COVID symptoms had also lower rate of red blood cells (RBC) (4,4 vs 4,6 mln; p=0.01); higher level of glucose (92 vs 90 mg%; p=0.02); lower glomerular filtration rate (GFR) estimate by Modification of Diet in Renal Disease (MDRD) (88 vs 95; p=0.02); higher level of hypersensitive cardiac Troponin T (hsTnT) (6.1 vs 3.9 ng/L; p=0.03). The parameters significant in univariate analyses were included to the multivariate model. The results of multiple logistic regression were as follows: age (OR 4.6, 95% CI: 1.7–11.5; p=0.001) and LVMI (OR 2.5, 95% CI: 1.0–6.6; p=0.04).

Conclusions
Persistent symptoms in long COVID can mimic those of cardiovascular disease. Spiroergometric parameters are useful in making a proper diagnosis.

Funding Acknowledgement
Type of funding sources: Public hospital(s). Main funding source(s): Polish Mother's Memorial Hospital Research Institute