Left atrial volumetric-mechanical coupling index as a marker of subclinical primary heart involvement in systemic sclerosis

Abstract Background Primary heart involvement in systemic sclerosis (SSc) is a common yet often clinically silent marker of poor prognosis. Up to 80% of patients have histopathological evidence of heart involvement, highlighting the need for better screening and diagnostic methods. N-terminal pro-brain natriuretic peptide (NTproBNP), a well-established cardiac biomarker, is often increased in patients with SSc, but with a not fully understood mechanism. Meanwhile, left atrial volumetric-mechanical coupling index (LACI), a new echocardiographic parameter, has been shown to predict cardiovascular outcomes in heart failure patients and the general population, but it has not been studied in SSc. Purpose To identify new echocardiographic parameters, particularly related to left atrial volume and function, as markers of increased NTproBNP in SSc patients without overt heart involvement. Methods Consecutive SSc patients without overt heart disease referred for routine cardiac screening underwent 2D and 3D transthoracic echocardiography, including atrial and ventricular strain analysis. LACI was calculated by both 2D and 3D echocardiography as the ratio between the left atrial volume index and the tissue-Doppler-imaging septal a’ velocity. Patients with significant structural and functional changes suggestive of systolic or diastolic dysfunction or pulmonary hypertension, and those with impaired global left ventricular strain were excluded. Logistic regression, Pearson correlation coefficients, and area under the receiver-operating characteristic curve (AUC) are used to analyze the association and predictive power of LACI for elevated NTproBNP. Results A total of 36 SSc patients (55±10 years old; 34 (94%) women; mean disease duration 14±11 years) were included. Sixteen (44.4%) had diffuse cutaneous involvement (dcSSc). Seventeen (47%) patients had increased NTproBNP levels (i.e. >125 pg/mL). Among all tested variables, 3D LACI had the best correlation with NTproBNP values (r = 0.63, p<0.001). A 3D LACI of >2 associated with NTproBNP of >125 pg/mL (odds ratio 7.33 [95%CI 1.38-38.8]; p=0.01) and predicted these increased values with a sensitivity of 76.9% and a specificity of 81.2% (AUC 0.78). NTproBNP was also correlated with 2D LACI (r=0.55, p<0.001), peak left atrial longitudinal strain (r=-0.42, p=0.01), and left atrial contraction strain (r=0.48, p=0.005). Compared to patients with limited cutaneous involvement, those with dcSSc had higher NTproBNP values (250±139.6 vs 107.2±110.9 pg/mL, p=0.001), higher 3D LACI values (2.6±0.9 vs 1.9±0.5, p=0.02), with similar left atrial and ventricular strain parameters. Conclusion Left atrial volumetric-mechanical coupling index assessed by 3D echocardiography is significantly associated with and predictive of elevated NTproBNP levels in SSc patients without overt heart disease and may be a potentially useful non-invasive marker for screening for early subclinical heart involvement in SSc patients.