Systematic Evaluation of Current Possibilities to Determine Left Ventricular Volumes by Echocardiography in Patients after Myocardial Infarction ()
1. Introduction
Accurate left ventricular (LV) volume determination by echocardiography is still a challenge in clinical practice. Nayyar and coworkers described that the interobserver variability for left ventricular volume determination can be significantly reduced by better endocardial border detection due to contrast echocardiography [1]. However, especially in patients with regional wall motion abnormalities quantification of left ventricular volumes and ejection fraction (EF) strongly depends on the views which were used for planimetry. Thus, the present study focusses on the variances of volumes in patients with regional myocardial infarction determined by performing planimetry in different echocardiographic views. This is important because changes of volumes during drug treatment after myocardial infarction can only be detected if determination of volumes are acceptable accurate and reproducible.
After acute myocardial infarction (AMI) the heart undergoes a process of structural and functional changes [2, 3]. This process is described as “remodeling” characterized by left ventricular dilatation, eccentric hypertrophy, wall thinning in the non-infarcted area and LV spherizisation as well as aneurysm formation in the infarcted area [4,5].
Echocardiography is accepted for quantification of LV volumes and LVEF as well as for determination of regional wall motion abnormalities in patients after AMI.The determination of left ventricular end-diastolic volumes (LVEDV), left ventricular end-systolic volumes (LVESV) and LVEF has individual prognostic value and is used to evaluate LV remodeling at follow-up investigations [3,6,7]. For improved diagnostics and especially in case of bad acoustic windows contrast echocardiography is established [8]. With respect to different infarction patterns the determination and analysis of LVEF and LV volumes should be analyzed by different echocardiographic modalities for early detection of remodeling.
The aim of the present study was a systematic evaluation of all current possibilities for determination of LV volumes and LVEF by native and contrast echocardiography. Thus, the mono-, bi-, triand multiplane approach was used for planimetry in patients after AMI despite the fact that regional wall motion abnormalities will have a significant impact on LV volumes. Furthermore, potential changes of the volume parameters due to an early remodeling process after AMI were evaluated. All patients were treated with valsartan or ACE (= angiotensin-converting enzyme) inhibitors.
2. Methods
In the present prospective study 57 patients were enrolled from June 2009 to March 2011. Ultimately 46 of 57 patients were enclosed and 37 underwent the study completely. The analysis focuses, however, only on patients with AMI. Thus, a total of 26 patients (age 63 ± 13) after AMI were included. The study population consists of 8 female and 18 male patients. All patients were treated with valsartan or ACE inhibitor in combination with beta blockers, respectively. Percutaneous coronary angioplasty was performed in a time interval of 1 to 6 hours after onset of symptoms. All patients were treated with aspirin, heparin, nitrates and beta blockers after onset of symptoms and prior to the intervention. Echocardiography was performed directly after interventional therapy at hospital pre-discharge and at follow-up 6 months later.
Inferior AMI was documented in 6 patients and anterior AMI was documented in 20 patients. Standardized transthoracic echocardiography as well as contrast echocardiography was performed in all patients using a GE Vivid 7 system (GE Healthcare) with a M4S phased array and a 3V probe [9]. LVEDV, LVESV and LVEF were determined using the modified Simpson’s rule in mono-, bi-, triand multiplane data sets. LV volumes and LVEF were obtained by endocardial border delineation at end-diastole and end-systole. With the method of disc left ventricular volumes result from a summation of elliptical discs perpendicular to the longitudinal axis of the left ventricle [10]. Monoplane analysis was obtained from the apical long axis view whereas biplane analysis was obtained using the apical 2- and 4-chamber view. The triplane analysis enables a simultaneous acquisition of all three standardized apical views. Real-Time-3D-Echocardiography (RT3DE) permits three-dimensional visualization of cardiac structures by acquisition of 3D data sets detecting the entire heart in a 90˚ × 90˚ sector. The LV systolic function was evaluated by automated endocardial border detection. For the quantification of multiplane data sets automated volume analysis (GE, 4D AutoLVQ software) was used [10,11]. Contrast administration was performed by repetitive bolus injections of 0.3 - 0.4 ml of SonoVue (BRACCO). The data sets were analyzed offline using the EchoPAC software version 110.1.1. In 10 of 26 randomly selected patients LVEDV, LVESV and LVEF was determined by another experienced investigator. The interobserver variability was assessed for each method using native and contrast echocardiography. Both investigators used the same data sets and were blinded to each other’s results.
Statistics
The statistical analysis was obtained by SPSS Statistics software version 17.0. Mean and standard deviations (SD) were calculated for LVEDV, LVESV and LVEF determined by native and contrast echocardiography using the different modalities. Both data of the parameters determined by native and contrast echocardiography and mono-, bi-, triand multiplane approaches were compared to each other using paired t-Test.
3. Results
The assessment of LVEDV, LVESV and LVEF is more accurate using contrast echocardiography. With respect to standardization and adequate image quality LVEDV, LVESV and LVEF show significant increases using contrast echocardiography in comparison to native echocardiography (Figures 1 and 2, Table 1 and Figures 3-8). In addition, due to reduced image quality in native echocardiography (defined by insufficient endocardial border detection in more than 2 segments) 5 patients could not be analyzed without contrast, whereas endocardial contour detection was possible in all patients using contrast. Results of LVEDV, LVESV and LVEF measurements were compared by paired t-Test (p < 0.001). Variances of LVEDV and LVEF are lower in contrast echocardiography compared to native echocardiography, respectively (Table 1). Although in some cases LVEDV was reduced in comparison to the investigation at hospital pre-discharge mean LVEDV was increased at the follow up after 6 months (p < 0.05, Figures 3-8).
In detail, this mean increase of LVEDV with a distinct increase of more than 10 ml within the follow up period was assessed in 10 patients. In this cohort in 6 patients the infarcted area was larger than 40% of the myocardium,
Figure 1. Determination of left ventricular systolic function by the apical mono-, biand triplane approach using native echocardiography in a patient with septal myocardial infarction. Above the apical long axis view (A), (B), the apical 2-chamber view (C), (D) and the apical 4-chamber view (E), (F) are shown at end-diastole (A), (C), (E) and end-systole (B), (D), (F). On the right the simultaneous visualization of all apical views obtained by the triplane approach including a corresponding dynamic LV cast is shown at end-diastole (G) and end-systole (H).
Table 1. Mean ± standard deviation and p-values (paired t-Test) of LVEDV, LVESV and LVEF obtained by the apical mono-, bi-, triand multiplane approach using native and contrast echocardiography. Both the investigation at hospital pre-discharge (1) and the follow-up (2) are shown.
and in 4 patients no reflow was observed after treatment of the culprit artery. In 5 patients LVEDV decreased, in 11 patients LVEDV did not significantly change. Significant differences of LVEDV and LVEF (p < 0.001) were also found using the apical mono-, bi-, triplane approach (Table 1, Figures 1 and 2) as well as the multi-
Figure 2. Determination of left ventricular systolic function by the apical mono-, biand triplane approach using contrast echocardiography in a patient with septal myocardial infarction. Above the apical long axis view (A), (B), the apical 2-chamber view (C), (D) and the apical 4-chamber view (E), (F) are shown at end-diastole (A), (C), (E) and end-systole (B), (D), (F). On the right the simultaneous visualization of all apical views obtained by the triplane approach including a corresponding dynamic LV cast is shown at end-diastole (G) and end-systole (H).
Figure 3. LVEDV (ml) obtained by the monoplane approach using native echocardiography at hospital pre-discharge and 6 months follow-up in patients after AMI. Changes of LVEDV are shown for each patient. In addition mean and standard deviation are given (LVEDV = left ventricular end-diastolic volume).
Figure 4. LVEDV (ml) obtained by the monoplane approach using contrast echocardiography at hospital predischarge and 6 months follow-up in patients after AMI. Changes of LVEDV are shown for each patient. In addition mean and standard deviation are given (LVEDV = left ventricular end-diastolic volume).
Figure 5. LVEDV (ml) obtained by the biplane approach using native echocardiography at hospital pre-discharge and 6 months follow-up in patients after AMI. Changes of LVEDV are shown for each patient. In addition mean and standard deviation are given (LVEDV = left ventricular end-diastolic volume).