Echocardiographic assessment of left atrial volume index in elderly patients with left ventricle anterior myocardial infarction.

INTRODUCTION: Enlarged left atrium predicts outcomes in patients with heart failure, atrial fibrillation and stroke. Left atrial volume especially when corrected for body size, is a more accurate representation of true LA size. AIMS AND
OBJECTIVES: To study left atrial volume index in elderly patients with left ventricle anterior infarction and correlate LAVi with left ventricle ejection fraction and transmitral Doppler flow.
MATERIALS AND METHODS: Control group consisted of 25 healthy elderly subjects Study group consisted of age and sex matched patients with LV anterior infarction with history of characteristic ischaemic chest pain. Patients with valve lesions, large shunts and rythum disturbances were excluded. On transthoracic echocardiography biplane method of disks was used to calculate LA volume. LAVi was calculated by dividing LA volume by body surface area of subjects. OBSERVATION AND
RESULTS: LAVi was significantly raised in elderly patients who suffered from AMI (P<0.005). We also found significant negative correlation of LAVi with LVEF, E wave peak velocity and deacceleration time.
CONCLUSION: Patients with advanced left venticular systolic and diastolic dysfunction had a significantly larger LAVi than healthy subjects. LAVi is useful for risk stratification and for guiding therapy in such patients.

INTRODUCTION

Recent evidence highlight the importance of enlarged left atrium (LA) as a barometer of diastolic burden and a good predictor of cardiovascular outcomes - including heart failure (HF), atrial fibrillation, stroke, and mortality.[1] It is considered a marker of chronically increased left atrial pressure and/or volume. LA volume has been compared to the “glycated hemoglobin of diabetes mellitus”,[2] as it is a reflection of a long-standing hemodynamic condition. Because left atrial size can be measured noninvasively by echocardiography, measurement of LA size is part of the standard echocardiographic examination.

The traditional method of assessing maximal end-systolic anteroposterior dimension of LA from the parasternal long-axis view in M-mode is simple and convenient but its accuracy may be limited by the anatomical confinement afforded by the spine and sternum and the resulting asymetrical or pillow-shaped enlargement of the left atrium.[3] Hence, measurement of a single LA diameter may underestimate actual LA size. For these reasons, multiple linear dimensions or measurement of left atrial volume (LAV) especially when corrected for body size (LAVi) is a more accurate representation of true LA size.[4]

AIMS AND OBJECTIVE

Our aim in the present study was to study left atrial volume index (LAVi) in elderly patients with left ventricle anterior infarction and to correlate LAVi with left ventricle ejection fraction (LVEF) and transmitral Doppler flow.

MATERIALS AND METHODS

The present study was conducted at the Department of Cardiology of Jawahar Lal Nehru Medical College and Associate Group of Hospitals, Ajmer, India.

Grouping of subjects

Control group n = 25: This group consisted of 25 elderly subjects (>70 years) without history of ischemic heart disease, systemic hypertension, and with normal findings in rest and exercise ECG and echocardiography.

Study group n = 50: This group consisted of age- and sex-matched patients with left ventricle (LV) anterior infarction with history of characteristic ischemic chest pain (>30 min), ST segment elevation >2 mm in anterior leads I, aVL, V1 -V6, and positive serum cardiac markers (CPK-MB, Troponin I).

Exclusion criteria

Significant valve lesions (mitral stenosis or greater than moderate mitral regurgitation)

Large shunts

Atrial flutter and fibrillation

Bundle branch block

Poor acoustic window

Design of study

The following detailed analysis were done for all subjects.

ECG

Complete and thorough analysis of all anterior leads in rest and exercise ECG was done.

Transthoracic 2D echocardiography

A transthoracic 2D echocardiographic examination was performed with patients in the left lateral decubitus position. The equipment used was SIEMENS transthoracic echocardiographic machine G-5 and CV-70 with 3.5 MHz transducer. With the use of apical 4-chamber view Simpson's LVEF was calculated as percentage of changes in LV chamber volumes between diastole and systole using formula EDV- ESV / EDV × 100. LA volume was measured from standard apical 4-chamber views at end-systole just before mitral valve opening. LA borders were traced using planimetry in control and study subjects [Figures 1 and 2]. The borders consisted of the walls of the left atrium excluding pulmonary veins and left atrial appendage. The biplane method of disks was used to calculate LA volume. LAVi was calculated by dividing LA volume by body surface area of subjects. Peak transmitral flow E and A wave velocity, E wave deceleration time, were measured from the apical 4-chamber view.

Figure 1

Trans thoracic echocardiogram (Apical 4 chamber view) showing assessment of LAV in normal healthy subjects

Figure 2

Trans thoracic echocardiogram (Apical 4 chamber view) showing assessment of LAV in study group subjects

Statistical evaluation

Data were expressed as mean ± SD. Comparison of all variables in both groups was done by using “unpaired Student's t-test”. Degree of freedom was calculated and P value was obtained. The results of P value were interpreted as follows: P > 0.05 - Not significant,P < 0.025 - Significant, P < 0.01 - Very significant, and P < 0.005 - Highly significant.

Observation

Table 1 shows the basal clinical characteristics of the two groups. There was no significant difference in age, gender, BMI, pulse rate, and blood pressure between the two groups (P > 0.05).

Table 1

Basal clinical characteristics of study and control group subjects

Table 2 shows systolic dysfunction (LVEF- 45 ± 10% vs 76 ± 9%) and stage 1 diastolic dysfunction in patients with left ventricle anterior myocardial infarction (LVAMI) as compared with healthy control group. LAVi was significantly raised in elderly patients who suffered from anterior myocardial infarction (AMI) (26.7 ± 2.1 vs 10.8 ± 2.9) (P < 0.005). Table 3 shows significant negative correlation of LAVi with LVEF, E wave peak velocity, and deceleration time.

Table 2

Values of echocardiographic LV systolic and diastolic function parameters in study and control group subjects

Table 3

Correlation of LAVi with other LV function parameters

DISCUSSION

LAVi <28 ml/m2 at rest predicts normal stress echocardiogram[5] and LAVi > 32 ml/m2 predicts mortality in patients with acute myocardial infarction (MI).[6] LAVi (>50 ml/m2 ) predicts HF hospitalization and mortality with similar statistical power as LVEF (< 45%) in ambulatory adults with coronary artery disease.[7] Increased LA volume is also a predictor of stroke and death. An indexed LA volume of ≥32 ml/m2 is associated with an increased risk of stroke independent of age and other clinical risk factors for cerebrovascular disease.[8] LA volume is intimately related to LV mass/hypertrophy, systolic, and diastolic dysfunction.[2] The only determinant of LA size is body surface area. LA size in a healthy person is independent of age. Indeed, increase in LA size is a reflection of pathophysiologic abnormalities that accompany advancing age rather than a consequence of chronologic aging.[9]

CONCLUSION

Patients with advanced left ventricular systolic and diastolic dysfunction had a significantly larger LAVi than healthy subjects.