Background and aim of the study. Previous studies evaluated the effects of heart rate (HR) increase on the left ventricular (LV) function, by two-dimensional longitudinal strain, but many authors also assessed the left atrium (LA) function based on speckle tracking imaging (STI). The LA and LV are connected through the mitral annulus and the LA modulates LV filling and performance. The interaction between LA and LV functions during the cardiac cycle (LA–LV coupling) is crucial. We aimed to evaluate the changes in LA strain in response to increases in HR.
Methods. We enrolled 45 patients. 38 were evaluated with LA strain. 31 patients were affected by chronic heart failure (CHF), among whom 18 with implanted cardioverter defibrillator (ICD), 13 with ICD and cardiac resynchronization therapy (ICD-CRT) and 7 without CHF who had a PM implanted. All were in clinically stable conditions for at least 30 days and in conventional medical therapy. Starting from basal values, HR was increased by 10 beats/min programming the implantable devices at higher atrial stimulation frequencies to max 90 beats/min. At each HR, echocardiography was performed and main functional parameters were calculated, including those for LV filling evaluation (i.e. E/e’ ratio). Changes in LA strain measures, i.e. the strain of reservoir (LAr), conduit (LAcd) and contraction (LAct), and in LV global longitudinal strain (LVGLS) were calculated. The ratio between LAr and septal E/e’ was evaluated to estimate LV filling pressures.
Results. No significant variation was found in the measurements of E/e's and the LAr/E/e's ratio when all patients were analysed. However, there was a significant reduction in LA/E/e's in patients who did not show HR-dependent worsening in LV-GLS and a significant increase in the other group (figure 1). These results underline the relationship between LA and LV functions and consequently show the AV uncoupling at higher HR. Interestingly, the worsening of both LA and LV function assessed by strain was more evident at the rate of 90 bpm (figure 2).
Conclusions. The increase of HR was associated with both worsening of LA and LV function assessed by STI. This response is associated with an increase in LV filling pressures. These results offer new data about HR related LA-LV coupling and could be useful for guiding the optimal HR responsiveness of the implanted devices.