Studies on Assessment of Left Atrial Distensibility to Predict Late Prognosis in Consecutive Patients Received Echocardiographic Examination

Introduction High left ventricular filling pressure (LVFP) have been associated with volume overload in patients with heart failure and have also been correlated to some extent with more severe symptoms and lower survival rates. In a study of more than 1000 patients hospitalized with acute decompensated heart failure, those with persistently elevated LVFP more than 18 mmHg had increased 1-year mortality compared with those with LVFP less than 16 mmHg. Investigators have also demonstrated that acute reduction of LVFP with vasodilator therapy can improve cardiac function and reduce mortality risk, suggesting that LVFP is an appropriate marker of cardiac risk and functional improvement. However, LVFP measurement involves invasive catheterization, limiting its clinical use especially in the outpatient setting. In advance of new techniques and modality, echocardiography provides some useful parameters to assess LVFP, such myocardial tissue Doppler imaging. Many articles had documented that peak velocity of early-diastolic trans-mitral inflow velocity divided by early-diastolic velocity over mitral annulus was closed correlated with LVFP. However, myocardial tissue Doppler only provides the information of regional myocardium, so patients with regional wall motion abnormality, such as coronary artery disease, can't be assessed by this method without handicap. In addition, conduction disturbance, like bundle branch block, also influences the result of myocardial tissue Doppler. For resolving those problems, we will design a new global parameter to assess LVFP. In prior study, we disclosed the logarithmic relationship between LVFP and left atrial distensibility in acute myocardial infarction patient received primary coronary intervention. This time, to extend our conclusion to general population received echocardiographic examination is attempted. Additionally, we infer that left atrial distensibility which indicates LVFP would influence long-term prognosis, including the event rate of cardiovascular event, stroke and death.

Purpose Left atrial size, particularly left atrial volume, has been recognized as a marker of left ventricular diastolic dysfunction. Contrary to flow and tissue Doppler parameters, left atrial volume is independent of acute volume load and therefore may provide a more accurate assessment of acute and chronic left ventricular dysfunction. In addition, the measurement of left atrial volume is lack of some handicaps of tissue Doppler, including regional myocardial dysfunction in coronary artery disease and bundle branch block. In recent studies, end-systolic left atrial volume (maximal left atrial volume) was useful to predict the risk of atrial fibrillation after cardiac surgery. The short-term and long-term prognosis of acute myocardial infarction was also associated with left atrial volume. In patients with mitral regurgitation, it could be used to reliably estimate the regurgitant volume. Despite end-systolic left atrial volume provides prognostic significance in many disease entities, left atrium is filling and empty in dynamic cyclic motion, so we speculate that left atrial distensibility, defined as the percentage change of left atrial volume between end-systolic and end-diastolic phase, has more prognostic power to represent LVFP and to predict the prognosis. Based on the phenomenon of that higher LVFP, which will conduct to and stretch left atrium in diastolic phase, induces left atrial distension and makes the reduction of distensibility between end-systolic and end-diastolic phases, we had proved the logarithmic relationship between left atrial distensibility and LVFP.

Materials and Methods

Subjects:

2000 consecutive patients received echocardiographic examinations will be enrolled. The exclusion criteria are including (1) patients with prosthetic mitral valves or mitral stenosis, (2) rhythm other than sinus rhythm, (3) age more than 18 years-old, (4) inadequate image quality, (5) lack of informed consent.