Prognostication and risk stratification by assessment of left atrioventricular plane displacement in patients with myocardial infarction

Abstract

Background: Mean left atrioventricular plane displacement is strongly related to prognosis in patients with heart failure. We aimed to examine its value for prognostication and risk stratification in patients hospitalised for acute myocardial infarction. Methods and results: Left atrioventricular plane displacement was assessed by echocardiography in 271 consecutive patients with acute myocardial infarction. Mean prospective follow-up was 628 days. Atrioventricular plane displacement was readily assessed in all patients and was significantly lower in patients who died (n=41, 15.1%) compared to the survivors: 8.2(5.6) v. 10.0(5.5) mm, P<0.0001. Overall mortality was 31.3% in the lowest quartile with regard to atrioventricular plane displacement (<8.00 mm) and 10.1% in the combined upper three quartiles. Thus, the hazard ratio for an atrioventricular plane displacement <8.0 mm compared to 8 mm or more was 3.1, P=0.0001. The combined mortality/heart failure hospitalisation incidence was 43.8% in the lowest and 14.6% in the combined upper three quartiles: Risk ratio 3.0, P<0.0001. In multivariate analysis, including age and history of atrial fibrillation, left atrioventricular plane displacement was an independent prognostic marker. Conclusion: In post-myocardial infarction patients, echocardiographic assessment of atrioventricular plane displacement showed a strong, independent prognostic value. Determination of left atrioventricular plane displacement can be readily performed in virtually all patients, and may in clinical practice facilitate identification of high-risk patients.

Introduction

The prognosis after acute myocardial infarction is related to the degree of left ventricular systolic dysfunction [1], [2], [3], [4], [5]. Left ventricular systolic function is often expressed as ejection fraction and most commonly measured by radionuclide ventriculography, contrast cineangiography and echocardiography. Echocardiography is the least complicated, expensive and time consuming, as well as the most accessible method.

Several echocardiographic techniques can be applied to evaluate global left ventricular systolic function. Traditional techniques, however, all have drawbacks. The fractional shortening and Teichholtz techniques are not reliable when left ventricular contraction is asymmetrical [6], [7], [8]. Two-dimensional echocardiography tolerates asymmetry but requires good image quality for adequate tracing of the endocardial borders [9], [10], [11], which is not always obtainable [12]. Some investigators have reported a poor agreement between left ventricular ejection fraction determined by two-dimensional echocardiography and ejection fraction evaluated by radionuclide ventriculography or contrast cineangiography [13], [14]. Others have shown that two-dimensional echocardiography correlates closely with radionuclide ventriculography [15], [16]. It has been reported that two-dimensional echocardiographic assessment of regional wall motion correlates closely with haemodynamic status, and that it is reliable, reproducible and valuable for selecting high risk patients [17], [18]. It does, however, require experienced investigators and it is somewhat time-consuming [17], [18].

The left ventricular pump function has traditionally been thought to be mainly related to the action of the circumferentially oriented myocardial fibres [19]. However, the complexity of myocardial fibre orientation and the importance of longitudinal fibres was thoroughly described in man in the early 1980’s [20], and has since been further clarified [21], [22], [23], [24], [25], [26], [27], [28], [29]. The epicardial surface of the heart remains practically immobile during the cardiac cycle [22], and normal left ventricular ejection requires displacement of the atrioventricular plane. During cardiac systole the atrioventricular plane moves towards the apex as a result of contraction of longitudinal fibres [22]. Since the distance between the apex and the chest surface is constant during the cardiac cycle [22], [23], [30], the left atrioventricular plane displacement (AVPD) as measured from the surface of the thorax, using transthoracic two-dimensionally guided M-mode echocardiography, equals the intraventricular displacement [25]. Mean left AVPD reflects global left ventricular function despite left ventricular asymmetry, since it is determined in four different regions of the left ventricle—the septal, lateral, inferior and anterior regions—and since it evaluates the total shortening along the left ventricular long axis in the respective region. Demands on image quality are quite low, as the atrioventricular plane is highly echogenic, and the examination only takes a few minutes [12].

We have previously shown that the prognosis in patients with heart failure correlates closely with the degree of left AVPD impairment [12]. The aim of the present study was to investigate the prognostic value of an echocardiographic determination of the left AVPD in patients with an acute myocardial infarction. We also wanted to assess whether cardiac morbidity was related to the degree of left AVPD impairment.