Fibromyalgia (FM) is a chronic pain syndrome that affects multiple body systems and is often associated with fatigue, sleep disturbances, anxiety, and other comorbidities. Increasing evidence suggests that FM is also linked to cardiovascular dysfunction due to autonomic imbalance, sympathetic overactivity, and endothelial dysfunction. Patients with FM may therefore be at higher risk of developing subclinical ventricular dysfunction even before overt cardiovascular disease becomes apparent.

Traditional echocardiographic evaluation of left ventricular function is based on ejection fraction (LVEF). However, LVEF has important limitations. It may remain normal despite underlying myocardial impairment, is strongly influenced by loading conditions, and often fails to detect early myocardial dysfunction. Recent advances in echocardiography allow for the assessment of Global Longitudinal Strain (GLS), a sensitive and reproducible measure of myocardial deformation. GLS abnormalities can be detected earlier than changes in LVEF and are predictive of future declines in ejection fraction.

This study aims to evaluate myocardial function in fibromyalgia patients using GLS obtained by two-dimensional speckle-tracking echocardiography (2D-STE). By comparing FM patients with age- and sex-matched healthy controls, the study seeks to determine whether FM patients show a higher prevalence of subclinical ventricular dysfunction.

The study is designed as a prospective, observational, case-control study. A total of 118 participants will be enrolled: 59 patients diagnosed with fibromyalgia according to the 2010 American College of Rheumatology (ACR) criteria, and 59 control subjects without fibromyalgia. The control group will consist of volunteers presenting with mechanical low back pain but without systemic rheumatic disease.

All participants will undergo echocardiographic examination using a standardized protocol with Vivid E95 Dimension ultrasound equipment (GE Healthcare). Global Longitudinal Strain will be measured offline using EchoPAC software, and results will be analyzed according to recommendations of the American Society of Echocardiography. In addition, fibromyalgia patients will complete the Fibromyalgia Impact Questionnaire (FIQ) to evaluate disease severity, and results will be compared with echocardiographic findings.

Primary Outcome: Prevalence of subclinical left ventricular dysfunction, defined as impaired GLS, in fibromyalgia patients compared to controls.

Secondary Outcome: Correlation between GLS values and fibromyalgia disease severity scores.

This study is expected to provide new insights into the cardiovascular involvement of fibromyalgia. Detecting early myocardial impairment with GLS may help identify patients at risk of future cardiovascular complications and may support closer monitoring and preventive strategies in this population.

Fibromyalgia (FM) is a chronic, multisystem disorder affecting approximately 2-4% of the general population, predominantly women. It is characterized by widespread musculoskeletal pain, fatigue, sleep disturbances, anxiety, cognitive impairment, and autonomic symptoms such as gastrointestinal irregularities, Raynaud-like phenomena, and sicca complaints. The pathophysiology remains incompletely understood but is thought to involve central pain sensitization and dysautonomia.

Emerging evidence indicates that FM is associated with increased cardiovascular risk. Observational studies have demonstrated a higher prevalence of endothelial dysfunction, arterial stiffness, arrhythmias, and coronary artery disease in FM patients. Mechanistically, chronic sympathetic overactivity and persistent catecholamine release may increase myocardial oxygen demand, impair microvascular perfusion, and lead to subtle myocardial dysfunction. Autonomic imbalance has also been documented by heart rate variability studies, supporting impaired sympathetic-parasympathetic regulation. Importantly, the overlap between FM symptoms (fatigue, poor sleep, reduced functional capacity) and those of heart failure suggests a potential underrecognized cardiac component in FM.

Conventional echocardiography relies on left ventricular ejection fraction (LVEF) to evaluate systolic function. However, LVEF may remain normal despite underlying myocardial impairment and is strongly affected by loading conditions and observer variability. Many patients with heart failure present with preserved ejection fraction (HFpEF), underscoring the limitations of LVEF as an early marker of myocardial dysfunction.

Global Longitudinal Strain (GLS), assessed using two-dimensional speckle-tracking echocardiography (2D-STE), has emerged as a more sensitive and reproducible tool for detecting early myocardial dysfunction. GLS abnormalities can precede measurable reductions in LVEF and have prognostic value across diverse conditions including ischemic heart disease, hypertension, valvular disease, chemotherapy-related cardiotoxicity, and heart failure.

Preliminary studies in FM populations suggest possible subclinical myocardial involvement. Some reports describe increased risk of diastolic dysfunction and impaired GLS in FM patients, possibly reflecting the impact of chronic stress and autonomic dysregulation on cardiac mechanics. Nevertheless, systematic and adequately powered investigations remain scarce.

This prospective, observational, case-control study is designed to fill this knowledge gap. The study will enroll 59 FM patients diagnosed according to the 2010 American College of Rheumatology (ACR) criteria and 59 age- and sex-matched controls without systemic rheumatic disease. Echocardiographic examinations will be performed using a standardized protocol (Vivid E95, GE Healthcare), and GLS will be measured offline with EchoPAC software, following the American Society of Echocardiography guidelines. Disease severity in FM will be assessed using the Fibromyalgia Impact Questionnaire (FIQ).

The primary hypothesis is that FM patients will demonstrate a higher prevalence of impaired GLS, consistent with subclinical ventricular dysfunction, compared with controls. The secondary hypothesis is that higher FIQ scores will correlate with greater impairment in GLS, suggesting a relationship between disease burden and cardiac involvement.

The anticipated significance of this research lies in clarifying the cardiovascular component of fibromyalgia. Early identification of myocardial dysfunction using GLS may allow for improved risk stratification, closer clinical monitoring, and preventive strategies aimed at reducing long-term cardiovascular morbidity. Beyond its clinical relevance, this study also extends the application of GLS into a non-traditional, rheumatology-related context, reinforcing the systemic nature of FM and the need for interdisciplinary management approaches.

Inclusion Criteria:

• Age between 18 and 50 years.
• No diagnosis of fibromyalgia.
• Volunteers presenting with mechanical low back pain but otherwise healthy.

Exclusion Criteria:

• Hypertension.
• Coronary artery disease.
• Diabetes mellitus.
• Significant valvular heart disease.
• Documented arrhythmias.
• Congestive heart failure.
• Systemic rheumatic diseases (e.g., SLE, RA).
• Hyperthyroidism or hypothyroidism.

Patients aged 18-50 years diagnosed with fibromyalgia according to the 2010 ACR criteria recruited from the Physical Medicine and Rehabilitation outpatient clinic of Ankara Training and Research Hospital, and age- and sex-matched healthy controls presenting with mechanical low back pain but without systemic disease.

Individual participant data will not be shared due to institutional policies regarding patient privacy and data protection regulations