|Year : 2019 | Volume
| Issue : 3 | Page : 135-140
Conventional Two-Dimensional Echocardiography Versus Contrast Echocardiography in the Assessment of Left Ventricular Volumes and Function in Patients with Poor Acoustic Window
Maulik Parekh1, Chandrashekhar Ponde2, Mohsin Ansari3
1 Department of Cardiology, Sir H. N. Reliance Foundation Hospital, Mumbai, Maharashtra, India
2 Department of Cardiology, P. D. Hinduja Hospital, Mumbai, Maharashtra, India
3 Department of Internal Medicine, Kohinoor Hospital, Mumbai, Maharashtra, India
|Date of Submission||24-May-2019|
|Date of Decision||03-Nov-2019|
|Date of Acceptance||24-Nov-2019|
|Date of Web Publication||18-Dec-2019|
A/701, Gods Gift Apartment, Adarsh Layout, Off Marve Road, Malad West, Mumbai - 400 064, Maharashtra
Source of Support: None, Conflict of Interest: None
Aim: To compare the number of left ventricular (LV) segments visualized, detection of regional wall motion, and LV volumes and function with conventional two-dimensional echocardiography versus that with contrast echocardiography in patients with poor acoustic windows. Materials and Methods: This was a prospective study done over a duration of 1 year, on 50 consenting patients with poor echocardiographic image quality. Basic information and baseline echocardiograms were recorded. SonoVue contrast was administered intravenously as per a preset protocol through a peripheral line, and LV endocardial border delineation was recorded in various comparable views. Results: There was a significant change in the quality of the echocardiographic images postcontrast enhancement, with no study images remaining uninterpretable and only 16% remaining technically difficult. The remaining studies became adequate in terms of endocardial border delineation. Myocardial segment visualization changed significantly after contrast, with the number of well-visualized segments per patient improving from 10.66 before contrast to 16.26 after contrast, on average. There was a significant change in the estimation of LV volumes after contrast administration. The biplane ejection fraction was also significantly different after contrast. The study detected new regional wall motion abnormalities in 10 (20%) patients out of the total 50. There was only one case of an adverse event in terms of three isolated ventricular premature complexes in one of the patients after contrast administration. Conclusion: Contrast echo appears to be an easy, safe, and reliable investigation in patients with poor echo windows. Our study shows that endocardial border delineation is best with contrast enhancement, which improves physician's confidence and hence can impact the overall diagnosis, management, and prognosis of patients based on the better and reliable echo findings.
Keywords: Contrast echocardiography, left ventricular opacification, modified Simpson
|How to cite this article:|
Parekh M, Ponde C, Ansari M. Conventional Two-Dimensional Echocardiography Versus Contrast Echocardiography in the Assessment of Left Ventricular Volumes and Function in Patients with Poor Acoustic Window. J Indian Acad Echocardiogr Cardiovasc Imaging 2019;3:135-40
|How to cite this URL:|
Parekh M, Ponde C, Ansari M. Conventional Two-Dimensional Echocardiography Versus Contrast Echocardiography in the Assessment of Left Ventricular Volumes and Function in Patients with Poor Acoustic Window. J Indian Acad Echocardiogr Cardiovasc Imaging [serial online] 2019 [cited 2020 Jul 6];3:135-40. Available from: http://www.jiaecho.org/text.asp?2019/3/3/135/273294
| Introduction|| |
Conventional contrast echocardiography was first described in 1967. This technique has aided in viewing the heart in patients with suboptimal acoustic windows by providing left ventricular (LV) opacification and enhanced endocardial border delineation. The technique of contrast echocardiography has been developed to aid in the visualization of suboptimal images. As cited by Bhatia and Senior, Olszewski found that these suboptimal images are seen in 10%–15% of echocardiography patients. As per the American Society of Echocardiography (ASE), suboptimal images are seen in overall 20% of echocardiography patients in real world.
Conventional contrast echocardiography was invented by an accidental observation in 1967 by Dr. Gramiak while doing a simultaneous catheterization and echo study on a patient with aortic stenosis. Conventional contrast echo is done using microbubble contrast. This type of contrast does not allow opacification of the left side of the heart due to destruction of bubbles in pulmonary capillaries (unless there is right to left shunt at some level) and is used for the evaluation of cardiac and extracardiac shunts and enhancing Doppler signals of tricuspid regurgitation, etc., The new-generation contrast microbubbles are thin with relatively permeable shells which are filled with air ( first generation) or high-molecular-weight gas (second generation) that slow diffusion and dissolution within the blood stream. First-generation contrast agents were created to opacify the left ventricle through intravenous injections by creating stabilized air bubbles by their adherence to microparticles. Second-generation contrast agents were created by replacing the air with gas which stabilizes bubbles even further, thus giving a longer lasting contrast.
Advancements in contrast echocardiography have led to its main applications today. The main applications are LV opacification and enhanced endocardial border delineation. LV opacification is the approved indication for contrast agents. Accurate measurements of LV function provide valuable diagnostic and prognostic information of the cardiac patient. Endocardial border delineation will lead to reduced interobserver variability and increased accuracy in the quantification of LV volume and ejection fraction (EF). Contrast echocardiography is beneficial in increasing the confidence of the interpreting physician in stress echocardiography for the assessment of regional LV function. Contrast echocardiography may also aid in identifying structural abnormalities, detecting intracardiac masses, and enhancing Doppler signals.
The main objective of our study was to compare the number of LV segments visualized, LV volumes and function, and detection of regional wall motion abnormality (RWMA) with conventional two-dimensional echocardiography (2DE) versus that with contrast echocardiography in patients with poor acoustic windows.
| Materials and Methods|| |
It was a prospective, single–center, open-label comparative study conducted at our center. A total of 50 patients were studied and enrolled on a consecutive basis. A sample size of 50 was calculated to detect the difference of 5 units on either side (two-sided test) with level of significance at 5% and power of test at 80% (a total of 50 patients were required). Patients were enrolled from the outpatient department (OPD), indoor wards, and intensive care unit (ICU) of our institute. The institutional review board approval was obtained for the study, and the study was funded by the medical research cell of our institute. Those patients who were advised echocardiography by their primary physician and had poor echocardiographic image quality were enrolled in the study after obtaining written informed consent. Patients under 18 years of age and with unstable angina, significant ventricular arrhythmia, New York Heart Association Class IV symptoms, and intracardiac shunts were excluded from the study.
Before performing the echocardiography study, baseline clinical characteristics were recorded in a prescribed format [Figure 1]. A complete two-dimensional and Doppler echocardiographic study was then performed using standardized protocols from the parasternal and apical windows (Vivid E9 and Vivid I, General Electric Medical Systems, Milwaukee, Wisconsin). Baseline images were obtained using second harmonic imaging and high mechanical index (MI) (1.0–1.5), with other settings individualized to attain the optimum image quality.
All the data of 2DE examination were recorded in a standardized format. The baseline echocardiographic study quality was noted and then patients were prepared for a contrast echocardiogram.
The images were interpreted by experienced echocardiographers. Images were interpreted with special attention to:
- The number of LV segments optimally visualized to interpret segmental wall motion
- The left ventricular end-systolic volume and end-diastolic volume (LVESV and LVEDV)
- Estimation of left ventricular ejection fraction (LVEF).
Image quality of the study was classified into:
- Technically difficult
A technically difficult study is defined as a study in which two or more myocardial segments cannot be visualized at baseline from any imaging window. An uninterpretable study was defined as a study in which more than 50% of the endocardium cannot be visualized from any window and no reliable information regarding LVEF can be reported.,
For unenhanced imaging, second harmonic imaging (MI 1.6, gain 50%, compression 50%, and rejection 50%) was used, whereas for contrast-specific imaging, a low MI of 0.3 was preselected (gain 60% and compression 15%).
Optimization of imaging conditions for endocardial border definition was performed for each patient by modulation of transmit power, gain, focus, and dynamic range, as required.
Apical four- and two-chamber views were acquired without and with contrast-enhancement. The patients were investigated in the left lateral recumbent position, and five consecutive cardiac cycles of each view were acquired during breath-hold at end expiration and digitally stored. Great care was taken to avoid apical foreshortening and to maximize the length from the base to the apex by taking views from different intercostal spaces.
Contrast was administered as per the ASE guidelines. The contrast agent used was SonoVue, a product of Bracco Diagnostics (Milan, Italy). The product is freely marketed in India and is approved by the United States Food and Drug Administration and Drugs Controller General of India for an LV opacification study. It was administered through a peripheral IV line of at least 20G caliber. 0.3–0.5 ml of reconstituted contrast was injected into the peripheral vein followed by 10–20 ml saline flush from the same vein. The saline flush was stopped once the contrast was visualized entering into the right ventricle. The contrast-enhanced images were recorded on the same echocardiographic equipment with the settings optimized and recommended by the ASE. The MI was set at 0.4–0.6. Patients were evaluated for LV function and visualization of LV segments in a standard format. These findings were compared with those derived from unenhanced 2DE at baseline. All participants were observed for any reaction/adverse effects for a period of 30 min postprocedure.
Data analysis was done with the help of SPSS Statistics version 15 (IBM Corp., Armonk, NY, USA) and SigmaPlot version 12 (Systat Software, San Jose, CA, USA). Quantitative data were presented with the help of mean, standard deviation, median, and interquartile range. Comparison between the study groups was done with the help of one-way ANOVA or Kruskal–Wallis test, and “pre-” and “post-” comparison was done with paired t-test or Wilcoxon signed-rank test as per the results of the normality test.
Qualitative data were presented with the help of frequency and percentage table; association among study groups was assessed with the help of Chi-square test, and Fisher's exact test was applied for 2 × 2 tables if the expected count was <5 in more than 25% of the cells. P < 0.05 was considered statistically significant.
| Results|| |
Of the total 50 patients included in this study, there were 37 (74%) male and 13 (26%) female patients. Of the 50 patients, 12 were from the wards, 25 were from the ICU, and 13 patients were from the OPD. The average age of the patients was 64.2 (±11.4) years. 34 (68%) had diabetes mellitus, 31 (62%) had hypertension, 16 (32%) had a history of heart diseases, and 20 (40%) patients had a history of pulmonary ailments. Among the 25 patients from the ICU, 16 patients were on ventilators [Table 1].
The echocardiographic study quality was determined by experienced echocardiographers on the basis of visualization of myocardial segments. At baseline (before contrast), a total of 28 (56%) of studies were categorized as technically difficult and 22 (44%) were categorized as uninterpretable.
The quality of the echocardiographic study changed significantly after contrast enhancement. There were 44% (22) studies which were uninterpretable at baseline. All these studies became either adequate (15) or technically difficult (7). There was no study deemed as uninterpretable after contrast enhanced echo. With contrast enhancement, the percentage of uninterpretable studies decreased from 44% to 0% and technically difficult studies decreased from 56% to 16%, with a resultant increase in adequate quality studies to 86%. If we analyze the image quality, it was poorest in ICU patients compared to ward and OPD patients. Similarly, the maximum improvement in image quality was also noted in an ICU patient after contrast enhancement [Table 2] and [Figure 2].
The total number of segments visualized before contrast was 547 segments, equating to an average of 10.6 segments per patient. After contrast administration, the total number of segments visualized increased to 813 segments, equating to 16.3 segments per patient or 95.6% of the LV myocardium (Wilcoxon, P < 0.0001). The largest degree of improvement was seen in the ICU group of patients [Figure 3].
|Figure 3: Average number of myocardial segments visualized before and after contrast|
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Our study detected new RWMAs in 10 (20%) patients of the total 50. These included RWMAs detected in both previously well-visualized and not well-visualized segments. The majority of the new RWMAs (6 out of 10) were detected in the ICU group of patients.
We also observed that unenhanced echocardiographic images seriously underestimated LVEDVs and overestimated the LVESVs, thereby underestimating the overall EF. The average biplane EF derived by the equipment from the modified Simpson's method was also significantly different in baseline and postcontrast echocardiograms. The overall EF improved in patients across all locations [Figure 4] and [Table 3].
|Figure 4: Biplane left ventricular ejection fraction before and after contrast|
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|Table 3: Comparison of various study parameters irrespective of location|
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After contrast echo, the patient's classification changed as per the new EF. The number of patients with severe LV dysfunction decreased from 14% to 4% and moderate LV dysfunction decreased from 50% to 36%, with a resultant increase in mild LV dysfunction category patients to 60% [Figure 5].
|Figure 5: Impact of contrast echocardiography on ejection fraction assessment|
Click here to view
We came across only one case of an adverse event in terms of three isolated ventricular premature complexes in one of the patients after contrast administration. This required no treatment and subsided on its own.
During the study of our patients, we came across a few interesting findings which were better appreciated on contrast echo. We recorded two patients with LV apical thrombus: one patient with LV noncompaction and one patient with LV apical hypoplasia.
| Discussion and Conclusion|| |
The purpose of this study was to test the significance of contrast echocardiography in improving endocardial border definition and to provide evidence that contrast, when used appropriately in select groups of patients, and to provide incremental benefit over and above the routine echo in assessing LV volumes and function. The present study demonstrates that contrast echocardiography significantly improves the quality and reliability of estimating RWMAs and LV volume quantification.
Our study group patients had diverse demographics. There were 37 males and 13 females. 34 (68%) patients were diabetics [Table 1]. The contrast echocardiogram can be a very useful tool in diabetic patients with poor echo windows. Elhendy et al. evaluated 128 patients with contrast echocardiography; in 101 (79%) patients, invasive angiography detected CAD. The sensitivity and specificity were 89 and 52%, respectively.
In our study, half (50%) of the patients with poor echocardiographic windows were from the ICU. Patients in the ICU are typically quite ill, and a complete understanding of their hemodynamics is essential. Bedside portable echocardiography in the ICU is an important tool in managing such critically ill patients, providing crucial anatomic and hemodynamic data, and often rendering invasive monitoring unnecessary. However, transthoracic echo imaging in the ICU can be of limited utility at times. ICU patients are unable to cooperate with the sonographer and cannot always be optimally positioned. Mechanical ventilation, bandages, lung disease, subcutaneous emphysema, chest tubes, and poor lighting conditions may all impart additional technical obstacles. Because of all the above factors, endocardial resolution is often suboptimal, preventing the accurate assessment of segmental wall motion and global LV function in ICU patients. In our study, we observed that not only were most patients from the ICU but also the majority of ICU patients (60%) had the worst (uninterpretable) acoustic windows at baseline. Reilly et al. also noted that in 70 unselected ICU patients, the wall motion analysis confidence and EF calculations were significantly better after contrast enhancement. Another large series by Kurt et al., which enrolled patients from medical ICU (MICU), surgical ICU (SICU), wards, and OPD, also noted that the patients most uninterpretable and technical difficult window at baseline belonged to SICU and MICU, respectively.
These findings showed that ICU patients are the ones which most frequently have poor echo windows and a good echo study is most crucial for them as LV wall motion and EF impact on their capacity to withstand the hemodynamic demands of illness and are prognostic indicators of survival.
The quality of the echocardiographic study changed significantly after contrast enhancement. As we can see in results, there were 44% (22) studies which were uninterpretable at baseline. All these studies became either adequate quality (15) or technically difficult quality (7). There was no study deemed as uninterpretable on contrast-enhanced echo. After CE, the percentage of uninterpretable studies decreased from 44% to 0% and technically difficult studies decreased from 56% to 16%, with a resultant increase in adequate studies to 86%. We compared our finding with that of a case series by Kurt et al.
As we can see from the results, in our study, we found that unenhanced echocardiographic images underestimated LVEDVs and overestimated the LVESVs, thereby underestimating overall EF. This finding also correlated with many other series reported,,, and with the study from Kurt et al.
Unenhanced 2DE is known to markedly underestimate LV volumes by as much as 30%–40% and LVEF by 3%–6%, when compared with CMR, which is considered as gold standard. The underestimation of LV volumes by unenhanced 2DE is attributed not only to the poor tracking of the endocardial border with this technique, but also to the adoption of off-axis imaging planes and frequent foreshortening of the LV apex. A recent study of 50 patients after acute myocardial infarction demonstrated that the improvement in accuracy of estimation of LV volume and LVEF with contrast-enhanced 2DE is similar to that obtained by unenhanced three-dimensional echocardiography when compared with CMR.
A change in EF by a 5%–10% dramatically changes patient's prognosis and can be helpful as an important tool to modify the management plan. The change in patients' category of LV dysfunction is striking and shows how a change in EF can impact on the overall prognosis.
Contrast echo is easy, safe, and reliable investigation in such circumstances. Other options are transesophageal echocardiogram and cardiac magnetic resonance imaging, which are quite expensive and more invasive. The present study demonstrates that contrast echocardiography significantly improves the quality and accuracy of patient echocardiograms.
Contrast echocardiography is highly underutilized in all parts of world. Based on our research, we would like to put forth that it should be made readily available as standard of care in state-of-art echocardiography laboratories for better interpretation of poor acoustic windows.
Every echocardiographic laboratory should have a written protocol that is detailed for physicians, fellows, and sonographers to follow to administer contrast correctly and to know when it is clinically indicated.
The present study is not without limitations. Small sample size is one major limitation. Another limitation is inter- and intraobserver variability bias. All studies were reported by senior cardiologists, but by a single interprter. Hence, the observer bias still remains.
Technical help from the echocardiography technician of P. D. Hinduja Hospital, Mumbai, Maharashtra, India.
Financial support and sponsorship
Educational grant from the Medical Research Cell of P. D. Hinduja Hospital, Mumbai, Maharashtra, India.
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]
[Table 1], [Table 2], [Table 3]