Differences in Thoracic Fluid Content and Cardiac contractility in Individuals with Myasthenia Gravis are Associated with the Severity of Autonomic Dysfunction

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Physiology in Focus 2024 (Northumbria University, UK) (2024) Proc Physiol Soc 59, PCB067

Poster Communications: Differences in Thoracic Fluid Content and Cardiac contractility in Individuals with Myasthenia Gravis are Associated with the Severity of Autonomic Dysfunction

Monika Zawadka-Kunikowska1, Mirosława Cieślicka1, Wieńczysława Adamczyk1, Monika Bejtka1, Joanna Fanslau1, Wojciech Kaźmierczak1, Łukasz Rzepiński1,

1Department of Human Physiology, Nicolaus Copernicus University Ludwik Rydygier Collegium Medicum in Bydgoszcz Bydgoszcz Poland, 2Department of Human Physiology, Nicolaus Copernicus University Ludwik Rydygier Collegium Medicum in Bydgoszcz Bydgoszcz Poland, 3The Institute of Physiology and Pathology of Hearing Warszawa Poland, 4Sanitas - Neurology Outpatient Clinic Bydgoszcz Poland, 5Department of Neurology, 10th Military Research Hospital and Polyclinic Bydgoszcz Poland,

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Introduction: Myasthenia gravis (MG), a rare autoimmune disorder, poses diagnostic and management challenges, with significant impacts on patients' quality of life. Cardiac autonomic dysfunction has been identified in patients with MG, often with limited comprehensive assessments integrating impedance cardiography (ICG).

Aims: We assessed cardiac function, including  thoracic fluid content and myocardial contractility, in both MG patients and healthy controls (HCs), and its correlation with the severity of autonomic impairment using cardiovascular autonomic function tests (AFTs).

Methods: Fifty-three patients with MG (median age 41, interquartile range 36-45) and 30 HCs  (median age 38, interquartile range 25-42) underwent standardized AFTs. Patients were categorized into Non-CAN (n=33) and CAN (n=20) groups based on their Cardiovascular Autonomic Neuropathy (CAN) status, as evaluated using the Composite Autonomic Scoring Scale (CASS). We continuously measured cardiovascular parameters using ICG, including thoracic fluid content (TFC), stroke volume (SV), cardiac output (CO), and myocardial contractility indices such as left ventricle ejection time (LVET), left ventricular work index (LVWI), index of contractility (IC), Heather Index (HI), and mean systolic ejection rate (MSER). Preload was assessed as end-diastolic index (EDI), and afterload as total peripheral vascular resistance (TPR). Heart rate and blood pressure (BP) were calculated from electrocardiography and plethysmography.

Results: At baseline before VM, the CAN-MG group exhibited significantly higher HR, diastolic BP, TPR, and lower values of EDI (p < 0.001), IC (p < 0.001), ACI (p = 0.005), LVET (p = 0.003), MSER (p < 0.001) than the HCs. Both MG groups (CAN, Non-CAN) had significantly lower values of SV, TFC than HCs (p < 0.001). In contrast, the CAN MG group showed significantly lower cardiac inotropy (HI) compared to the Non-CAN MG and HCs groups. Total CASS score correlated with lower resting thoracic fluid content (R = -0.36, p=0.009) and myocardial contractility parameters: IC (R=-0.36, p=0.007), HI (R = -0.40, p=0.003), EDI (R = -0.36, p=0.009), MSER (R = -0.33, p=0.016), LVWI (R=-0.32, p=0.019), ACI (R = -0.31, p=0.024), At baseline, decreased preload (EDV), TFC, myocardial contractility (MSER, LVWI, ACI), and cardiac inotropy (HI) parameters were associated with higher TPR at rest.

Conclusions: These findings underscore the significance of subclinical cardiac impairment associated with decreased thoracic fluid content and myocardial contractility in MG patients, as well as their relationship with the severity of autonomic abnormalities.

 

 

Where applicable, experiments conform with Society ethical requirements.

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