Assessing diastolic dysfunction in cardiac amyloidosis: a comparative evaluation of left atrial coupling index and left atrial reservoir strain

Background Left atrioventricular coupling index (LACI) and left atrial strain during the reservoir phase (LASr) calculated with transthoracic echocardiography (TTE) and cardiac magnetic resonance (CMR) have emerged as markers of diastolic dysfunction (DD) associated with poor prognosis. However, data on the role of LACI as a marker of DD in cardiac amyloidosis (CA) are limited, and no direct comparison between LACI and LASr has been performed. Purpose Our aim was to evaluate the role of LACI and LASr as markers of diastolic dysfunction in patients with CA using TTE and CMR. Methods All patients underwent both TTE and CMR at the time of CA diagnosis. LACI —defined as the ratio between end-diastolic left atrial volume and end-diastolic left ventricular volume—and LASr were assessed using both TTE (LACI-TTE and LASr-TTE) and CMR (LACI-CMR and LASr-CMR). DD was graded according to the recommendations of the European Association of CardioVascular Imaging. Significant diastolic dysfunction was defined as DD grade >1 in patients with sinus rhythm, or as either a monophasic filling pattern with deceleration time <160 ms or E/e′ ratio >11 in those with atrial fibrillation. Correlation coefficients were calculated to evaluate the relationship between LACI and other imaging parameters. Receiver operating characteristic (ROC) curve analysis was used to determine the areas under the curves (AUCs) for LACI and LASr and to assess their diagnostic accuracy in detecting significant diastolic dysfunction. Optimal cut-off values for both LACI and LASr were determined using the Youden index, while the DeLong test was used to compare the ROC curves. Results A total of 52 consecutive patients were included in the study (median age 71 years [IQR: 64–76]; 77% male). A moderate correlation was observed between LACI-CMR and LACI-TTE (ρ = 0.58, p < 0.001), as well as between LACI-TTE and LASr-TTE (ρ = – 0.62, p < 0.001), and between LACI-CMR and LASr-CMR (ρ = – 0.64, p < 0.001). LACI-TTE showed a moderate correlation with diastolic dysfunction grade (ρ = 0.57, p < 0.001), whereas LACI-CMR was not correlated (ρ = 0.29, p = 0.09). In ROC curve analysis for the detection of significant DD, the diagnostic performance of LACI-TTE (AUC = 0.837, CI 95%: 0.7 - 0.9) was comparable to that of LASr-TTE (AUC = 0.713, CI 95%: 0.5 - 0.9; p = 0.2). The optimal cut-off values for predicting significant diastolic dysfunction were 0.45 for LACI-TTE, with 84% sensitivity and 72% specificity, and 8.6% for LASr-TTE, with 60% sensitivity and 83% specificity. Conclusion In patients with CA, LACI derived from echocardiography—but not from CMR—is associated with diastolic dysfunction grade (DD). LACI-TTE demonstrated comparable accuracy for detecting diastolic dysfunction to LASr-TTE, with the added advantages of being simple, feasible, and noninvasive. These findings support its potential role as a complementary marker for assessing diastolic function in patients with cardiac amyloidosis.