{ "id": "epvy9w9e43", "slug": "contrast-echocardiography", "title": "Contrast echocardiography", "updated": "2026-09-30", "topic_path": [ { "id": "life", "label": "Life and health", "api_url": "https://www.edgepedia.org/api/v1/topics/life" }, { "id": "life.health", "label": "Human health and medicine", "api_url": "https://www.edgepedia.org/api/v1/topics/life.health" }, { "id": "life.health.clinical", "label": "Clinical assessment and procedures", "api_url": "https://www.edgepedia.org/api/v1/topics/life.health.clinical" }, { "id": "life.health.clinical.clinical-imaging", "label": "Medical imaging and radiography", "api_url": "https://www.edgepedia.org/api/v1/topics/life.health.clinical.clinical-imaging" }, { "id": "life.health.clinical.clinical-imaging.ultrasound-and-echocardiography", "label": "Ultrasound and echocardiography", "api_url": "https://www.edgepedia.org/api/v1/topics/life.health.clinical.clinical-imaging.ultrasound-and-echocardiography" } ], "geo": [ { "id": "geo.nongeo.t1946.life.health.clinical.clinical-imaging.ultrasound-and-echocardiography", "label": "Non-geographic · 1946 to 2000: Ultrasound and echocardiography", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo.t1946.life.health.clinical.clinical-imaging.ultrasound-and-echocardiography", "path": [ { "id": "geo.nongeo", "label": "Non-geographic", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo" }, { "id": "geo.nongeo.t1946", "label": "Non-geographic · 1946 to 2000", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo.t1946" }, { "id": "geo.nongeo.t1946.life", "label": "Life and health", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo.t1946.life" }, { "id": "geo.nongeo.t1946.life.health", "label": "Human health and medicine", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo.t1946.life.health" }, { "id": "geo.nongeo.t1946.life.health.clinical", "label": "Clinical assessment and procedures", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo.t1946.life.health.clinical" }, { "id": "geo.nongeo.t1946.life.health.clinical.clinical-imaging", "label": "Medical imaging and radiography", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo.t1946.life.health.clinical.clinical-imaging" }, { "id": "geo.nongeo.t1946.life.health.clinical.clinical-imaging.ultrasound-and-echocardiography", "label": "Ultrasound and echocardiography", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo.t1946.life.health.clinical.clinical-imaging.ultrasound-and-echocardiography" } ] } ], "excerpt": "Contrast echocardiography is cardiac ultrasound performed after intravenous injection of gas microbubbles that opacify the blood pool, used when up to 20% of echocardiograms have poor endocardial border definition.", "snippet": "Contrast echocardiography is cardiac ultrasound performed after intravenous injection of gas microbubbles that opacify the blood pool, used when up to 20% of echocardiograms have poor endocardial border definition.", "node": "life.health.clinical.clinical-imaging.ultrasound-and-echocardiography", "markdown": "# Contrast echocardiography\n\nContrast echocardiography is cardiac ultrasound performed after intravenous injection of echo-contrast agents, gas microbubbles that opacify the blood pool and generate bubble-specific signals. It exists because up to 20% of resting echocardiograms have suboptimal left ventricular endocardial border definition, meaning at least two myocardial segments cannot be visualized.[1](https://www.asecho.org/wp-content/uploads/2025/05/2014_Contrast-Sonography.pdf) Guidelines recommend contrast when two or more contiguous apical-view segments are not clearly seen or when accurate quantification is needed.[2](https://www.mdpi.com/2075-4418/15/14/1743) The only FDA-approved cardiac indication is left ventricular opacification by intravenous injection; stress echo, Doppler enhancement, perfusion assessment, and intracoronary injection during alcohol [septal ablation](https://www.edgepedia.org/septal-ablation) are off-label uses.[3](https://www.uptodate.com/contents/contrast-echocardiography-contrast-agents-safety-and-imaging-technique/print)\n\n| Key fact | Detail |\n|---|---|\n| Trigger for use | Two or more contiguous segments not visualized on non-contrast imaging[2](https://www.mdpi.com/2075-4418/15/14/1743) |\n| US-approved agents | Optison (octafluoropropane, albumin shell), Definity (octafluoropropane, lipid shell), Lumason (sulfur hexafluoride, lipid shell)[4](https://www.asecho.org/wp-content/uploads/2025/05/Contrast-Echo-On-Label-Summary-FINAL-rev.pdf) |\n| Physical basis | Gas is 100,000 times less dense than blood, producing a strong acoustic impedance mismatch[3](https://www.uptodate.com/contents/contrast-echocardiography-contrast-agents-safety-and-imaging-technique/print) |\n| Imaging settings | Low mechanical index (<0.2) with multi-pulse tissue cancellation; bubbles destroy reproducibly at MI > 0.5[4](https://www.asecho.org/wp-content/uploads/2025/05/Contrast-Echo-On-Label-Summary-FINAL-rev.pdf) |\n| EF measurement | Interreader variability with contrast (7.4–8.0%) matches cardiac MRI (7.9%)[5](https://onlinejase.com/article/S0894-7317%2813%2900963-2/abstract) |\n| Serious reactions | About 1 in 10,000 doses (pseudoanaphylactic)[4](https://www.asecho.org/wp-content/uploads/2025/05/Contrast-Echo-On-Label-Summary-FINAL-rev.pdf) |\n| Perfusion timing | Normal myocardium replenishes within 5 s of a flash at rest, within 2 s under stress[6](https://echo.biomedcentral.com/counter/pdf/10.1186/s44156-022-00008-3.pdf) |\n\n## How it works\n\nMicrobubbles reflect ultrasound because gas and blood differ enormously in acoustic impedance; gas is 100,000 times less dense than blood.[3](https://www.uptodate.com/contents/contrast-echocardiography-contrast-agents-safety-and-imaging-technique/print) Commercial agents are microbubbles of inert, high-molecular-weight, low-solubility gas in an elastic shell, small enough (under about 7 µm, red-blood-cell size) to pass unimpeded through pulmonary and systemic capillaries, so they remain entirely intravascular.[7](https://link.springer.com/article/10.1186/s44156-023-00034-9) • [4](https://www.asecho.org/wp-content/uploads/2025/05/Contrast-Echo-On-Label-Summary-FINAL-rev.pdf) The shell and heavy gas limit outward diffusion, extending persistence, with signals detectable for 10 to 30 minutes depending on dose and ultrasound power.[2](https://www.mdpi.com/2075-4418/15/14/1743)\n\nIn the acoustic field the bubbles oscillate asymmetrically, expanding more than they compress, which generates nonlinear fundamental and harmonic signals that linear tissue echoes lack.[8](https://icus-society.org/wp-content/uploads/2021/11/heart-guidelines.pdf) The mechanical index, defined as peak negative pressure (MPa) divided by the square root of transmit frequency (MHz), governs bubble behavior.[9](https://www.sciencedirect.com/science/article/pii/S0894731708005695) Non-contrast 2D echocardiography usually runs at MI above 0.8; contrast studies use low MI below 0.2, where multi-pulse sequences (pulse inversion, power modulation, or both) send pulses differing in phase or amplitude so linear tissue echoes cancel and only bubble signals remain.[2](https://www.mdpi.com/2075-4418/15/14/1743) • [9](https://www.sciencedirect.com/science/article/pii/S0894731708005695) At MI above 0.5, oscillation becomes inertial cavitation and destroys bubbles reproducibly.[4](https://www.asecho.org/wp-content/uploads/2025/05/Contrast-Echo-On-Label-Summary-FINAL-rev.pdf)\n\n## How it is done\n\nPreparation differs by agent: Definity requires 45 s of mechanical VIALMIX agitation and is usable up to 12 h at room temperature; Lumason is reconstituted with saline and shaken vigorously for 20 s, usable up to 3 h; Optison is resuspended by hand.[6](https://echo.biomedcentral.com/counter/pdf/10.1186/s44156-022-00008-3.pdf) • [8](https://icus-society.org/wp-content/uploads/2021/11/heart-guidelines.pdf) Typical boluses are 0.1 mL of Definity or 0.5 mL of Lumason, each followed by a 5 mL saline flush over about 10 s; the flush should be injected slowly to reduce attenuation of deeper left ventricular segments.[6](https://echo.biomedcentral.com/counter/pdf/10.1186/s44156-022-00008-3.pdf) • [2](https://www.mdpi.com/2075-4418/15/14/1743) Continuous infusion is additionally approved for Definity and gives a stable agent concentration at the cost of pumps and preparation time.[4](https://www.asecho.org/wp-content/uploads/2025/05/Contrast-Echo-On-Label-Summary-FINAL-rev.pdf)\n\nThe operator images in non-contrast 2D until contrast appears in the right ventricle (about 5–10 s), switches to contrast-specific mode, and captures left-heart opacification, which follows about 5 s, or 3–5 cardiac cycles, after right ventricular opacification.[2](https://www.mdpi.com/2075-4418/15/14/1743) Brief high-MI flash impulses (MI 0.8–1.2 for 5–15 frames) clear contrast from the myocardium to sharpen endocardial-cavity discrimination.[4](https://www.asecho.org/wp-content/uploads/2025/05/Contrast-Echo-On-Label-Summary-FINAL-rev.pdf)\n\n## Origin\n\nRaymond Gramiak and Pravin M. Shah at the [University of Rochester](https://www.edgepedia.org/university-of-rochester) observed striking enhancement of M-mode echo signals from the aortic root during indocyanine green injections at catheterization around 1967–1968, and the term \"contrast echocardiography\" was coined by analogy with \"contrast angiography\".[10](https://link.springer.com/chapter/10.1007/978-94-015-8126-4_1) • [11](https://doi.org/10.1097/00004424-196809000-00011) • [10](https://link.springer.com/chapter/10.1007/978-94-015-8126-4_1) Gramiak, Shah, and David H. Kramer followed with \"Ultrasound Cardiography: Contrast Studies in Anatomy and Function\" ([Radiology](https://www.edgepedia.org/radiology), 1969).[12](https://doi.org/10.1148/92.5.939) [Harvey Feigenbaum](https://www.edgepedia.org/harvey-feigenbaum) and colleagues extended the approach to the left ventricle with intracardiac indocyanine green injections (Circulation, 1970).[13](https://doi.org/10.1161/01.cir.41.4.615) Agitated saline remained the only option for decades; Optison, with a human-serum-albumin shell, was the first perfluorocarbon-containing intravenous agent approved for left ventricular opacification and endocardial border delineation in humans.[2](https://www.mdpi.com/2075-4418/15/14/1743) • [9](https://www.sciencedirect.com/science/article/pii/S0894731708005695) Kevin Wei and colleagues reported quantification of myocardial blood flow by ultrasound-induced destruction of microbubbles during constant venous infusion in 1998,[14](https://doi.org/10.1161/01.cir.97.5.473) and W. Gregory Hundley and colleagues showed the same year that an intravenous perfluorocarbon agent improved echocardiographic LV volumes and ejection fraction against cine MRI.[15](https://doi.org/10.1016/s0735-1097%2898%2900409-4)\n\n## Variants\n\n**Left ventricular opacification (LVO)** is the approved core use: homogeneous cavity enhancement without swirling or blooming.[6](https://echo.biomedcentral.com/counter/pdf/10.1186/s44156-022-00008-3.pdf) **Saline contrast** uses hand-agitated air bubbles that are too large and short-lived to cross the pulmonary bed, so they opacify the right heart and enter the left heart only when a right-to-left intracardiac or pulmonary arteriovenous shunt exists; this property underlies shunt (for example, patent foramen ovale) detection.[3](https://www.uptodate.com/contents/contrast-echocardiography-contrast-agents-safety-and-imaging-technique/print) • [16](https://pmc.ncbi.nlm.nih.gov/articles/PMC11283996/) **Myocardial contrast echocardiography (MCE)** images perfusion: after a flash clears capillary bubbles, the replenishment rate gives capillary blood velocity, and its product with capillary blood volume (about 90% of myocardial blood resides in capillaries) gives myocardial blood flow.[7](https://link.springer.com/article/10.1186/s44156-023-00034-9) **Contrast stress echo** combines LVO with exercise or dobutamine stress, and **Doppler enhancement** uses contrast to record velocity signals where transmission is poor.[7](https://link.springer.com/article/10.1186/s44156-023-00034-9)\n\n## Applications\n\nIn 110 patients, contrast raised feasibility of biplane volume analysis from 79% to 95%, and ejection fraction differed from MRI by ≥10 EF units in 23 patients before contrast versus none after; interobserver variability for EF fell from 13.9% to 9.6%.[17](https://www.sciencedirect.com/science/article/pii/S0735109704012173) A 120-patient multicenter study found inter-observer reliability for EF of 0.91 with contrast echo, above cardiac MRI (0.86), cineventriculography (0.80), and unenhanced echo (0.79).[18](https://academic.oup.com/eurheartj/article-pdf/26/6/607/23989248/ehi083.pdf) In a Korean multicenter study, poor image quality fell from 31% to 2% and a poorly seen LV apex from 49.4% to 2.4%.[19](https://e-jcvi.org/Synapse/Data/PDFData/0059JCU/jcu-25-28.pdf)\n\nContrast also distinguishes apical hypertrophic cardiomyopathy, apical aneurysms, and thrombus from vascularized tumor, and separates trabecular from compacted myocardium in noncompaction.[20](https://pmc.ncbi.nlm.nih.gov/articles/PMC9707559/) Enhanced Doppler yields aortic stenosis gradients and pulmonary artery pressures in patients with poor windows.[20](https://pmc.ncbi.nlm.nih.gov/articles/PMC9707559/) In stress echo, contrast in suboptimal windows produced sensitivity and specificity for coronary artery disease equivalent to patients with optimal images.[21](https://www.jacc.org/doi/10.1016/j.jacc.2008.08.066) Myocardial perfusion adds value over wall motion: perfusion remains unaffected in left bundle branch block, so an inducible perfusion defect there suggests flow-limiting disease where a wall-motion abnormality may not.[7](https://link.springer.com/article/10.1186/s44156-023-00034-9) Investigational directions include imaging the vasa vasorum to assess plaque vulnerability and theranostic agents for drug delivery and sonothrombolysis.[20](https://pmc.ncbi.nlm.nih.gov/articles/PMC9707559/)\n\n## Limitations and alternatives\n\n**Failure modes** are mostly artifact and timing. Faster injection concentrates microbubbles apically and causes basal attenuation; slower injection causes swirling and incomplete opacification.[6](https://echo.biomedcentral.com/counter/pdf/10.1186/s44156-022-00008-3.pdf) [Attenuation](https://www.edgepedia.org/attenuation) from high bubble concentration is treated by reducing dose or several seconds of high-MI (0.8–1.2) imaging.[4](https://www.asecho.org/wp-content/uploads/2025/05/Contrast-Echo-On-Label-Summary-FINAL-rev.pdf) • [2](https://www.mdpi.com/2075-4418/15/14/1743)\n\n**Safety history.** In October 2007 the FDA placed a boxed warning on Definity and Optison. The 2008 ASE consensus attributes it to deaths in 4 patients with underlying cardiovascular disease among roughly 2 million doses over 6 years (about 1 per 500,000), while the 18,749-patient JACC safety study reports 11 deaths (4 within 30 minutes) temporally related to but not clearly caused by contrast; both accounts are published.[9](https://www.sciencedirect.com/science/article/pii/S0894731708005695) • [21](https://www.jacc.org/doi/10.1016/j.jacc.2008.08.066) Labeling was relaxed in 2008, monitoring requirements for pulmonary hypertension and unstable cardiopulmonary states were removed in 2011, and in 2016 the contraindication for right-to-left shunts was removed for all three agents; the FDA has since lifted the 2007 contraindications, though the boxed warning for serious cardiopulmonary reactions remains in the current labeling for Definity and Optison.[9](https://www.sciencedirect.com/science/article/pii/S0894731708005695) • [1](https://www.asecho.org/wp-content/uploads/2025/05/2014_Contrast-Sonography.pdf) • [4](https://www.asecho.org/wp-content/uploads/2025/05/Contrast-Echo-On-Label-Summary-FINAL-rev.pdf) • [16](https://pmc.ncbi.nlm.nih.gov/articles/PMC11283996/) • [22](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=8ab9c79c-1b5c-4e86-899c-cc74686f070a) Serious pseudoanaphylactic reactions occur in about 1 in 10,000 doses.[4](https://www.asecho.org/wp-content/uploads/2025/05/Contrast-Echo-On-Label-Summary-FINAL-rev.pdf) Studies across inpatient, critical care, pulmonary hypertension, and mechanical support populations reported no deaths and no increase in myocardial infarction or mortality versus controls; DEFINITY is FDA-approved for pediatric patients with suboptimal echocardiograms to opacify the left ventricular chamber and improve delineation of the left ventricular endocardial border, and safety data in pregnancy are unavailable.[4](https://www.asecho.org/wp-content/uploads/2025/05/Contrast-Echo-On-Label-Summary-FINAL-rev.pdf) • [23](https://www.accessdata.fda.gov/drugsatfda_docs/label/2024/021064s033lbl.pdf)\n\n**Alternatives.** Against cardiac MRI, contrast echo reaches comparable EF variability (7.4–8.0% vs 7.9%).[5](https://onlinejase.com/article/S0894-7317%2813%2900963-2/abstract) Against nuclear SPECT, two large multicenter studies found superior sensitivity but lower specificity for myocardial perfusion stress echo, possibly because contrast echo assesses flow kinetics as well as blood volume.[16](https://pmc.ncbi.nlm.nih.gov/articles/PMC11283996/)\n\n## References\n\n1. [Guidelines for the Cardiac Sonographer in the Performance of Contrast Echocardiography: Focused Update (ASE, 2014)](https://www.asecho.org/wp-content/uploads/2025/05/2014_Contrast-Sonography.pdf)\n2. [How to Perform Cardiac Contrast-Enhanced Ultrasound (cCEUS): Part I (Diagnostics, 2025)](https://www.mdpi.com/2075-4418/15/14/1743)\n3. [Contrast echocardiography: Contrast agents, safety, and imaging technique (UpToDate, updated Mar 2026)](https://www.uptodate.com/contents/contrast-echocardiography-contrast-agents-safety-and-imaging-technique/print)\n4. [ASE Guidelines and Recommendations for Contrast Echocardiography: A Summary for FDA-Approved Applications (2018 guideline summary)](https://www.asecho.org/wp-content/uploads/2025/05/Contrast-Echo-On-Label-Summary-FINAL-rev.pdf)\n5. [abstract (onlinejase.com)](https://onlinejase.com/article/S0894-7317%2813%2900963-2/abstract)\n6. [CEUS cardiac exam protocols: International Contrast Ultrasound Society (ICUS) recommendations (Echo Research & Practice, 2022)](https://echo.biomedcentral.com/counter/pdf/10.1186/s44156-022-00008-3.pdf)\n7. [Contrast echocardiography: a practical guideline from the British Society of Echocardiography (Echo Research & Practice, 2023)](https://link.springer.com/article/10.1186/s44156-023-00034-9)\n8. [Clinical Applications of Ultrasonic Enhancing Agents in Echocardiography (ASE 2018 guidelines update, hosted by ICUS)](https://icus-society.org/wp-content/uploads/2021/11/heart-guidelines.pdf)\n9. [ASE Consensus Statement on the Clinical Applications of Ultrasonic Contrast Agents in Echocardiography (2008)](https://www.sciencedirect.com/science/article/pii/S0894731708005695)\n10. [Contrast echocardiography, a historical perspective](https://link.springer.com/chapter/10.1007/978-94-015-8126-4_1)\n11. [Raymond Gramiak, Pravin M. Shah (1968). Echocardiography of the Aortic Root. Investigative Radiology.](https://doi.org/10.1097/00004424-196809000-00011)\n12. [Raymond Gramiak, Pravin M. Shah, David H. Kramer (1969). Ultrasound Cardiography: Contrast Studies in Anatomy and Function. Radiology.](https://doi.org/10.1148/92.5.939)\n13. [HARVEY FEIGENBAUM and colleagues (1970). Identification of Ultrasound Echoes from the Left Ventricle by Use of Intracardiac Injections of Indocyanine Green. Circulation.](https://doi.org/10.1161/01.cir.41.4.615)\n14. [Kevin Wei and colleagues (1998). Quantification of Myocardial Blood Flow With Ultrasound-Induced Destruction of Microbubbles Administered as a Constant Venous Infusion. Circulation.](https://doi.org/10.1161/01.cir.97.5.473)\n15. [Administration of an intravenous perfluorocarbon contrast agent improves echocardiographic determination of left ventricular volumes and ejection fraction: comparison with cine magnetic resonance imaging (Journal of the American College of Cardiology, 1998)](https://doi.org/10.1016/s0735-1097%2898%2900409-4)\n16. [Microbubble Enhanced Echocardiography in Current Cardiology Practice (Reviews in Cardiovascular Medicine)](https://pmc.ncbi.nlm.nih.gov/articles/PMC11283996/)\n17. [Accurate and reproducible measurement of left ventricular volume and ejection fraction by contrast echocardiography: A comparison with magnetic resonance imaging (JACC)](https://www.sciencedirect.com/science/article/pii/S0735109704012173)\n18. [Assessment of systolic left ventricular function: a multi-centre comparison of cineventriculography, cardiac magnetic resonance imaging, unenhanced and contrast-enhanced echocardiography (European Heart Journal, 2005)](https://academic.oup.com/eurheartj/article-pdf/26/6/607/23989248/ehi083.pdf)\n19. [Impact of Contrast Echocardiography on Assessment of Ventricular Function and Clinical Diagnosis in Routine Clinical Echocardiography: Korean Multicenter Study](https://e-jcvi.org/Synapse/Data/PDFData/0059JCU/jcu-25-28.pdf)\n20. [Established and emerging roles for ultrasound enhancing agents (contrast echocardiography), Clinical Cardiology 2022](https://pmc.ncbi.nlm.nih.gov/articles/PMC9707559/)\n21. [Safety and Effectiveness of Contrast Echocardiography in 18,749 Patients Undergoing Stress Echocardiography](https://www.jacc.org/doi/10.1016/j.jacc.2008.08.066)\n22. [DailyMed - DEFINITY- perflutren injection, suspension](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=8ab9c79c-1b5c-4e86-899c-cc74686f070a)\n23. [accessdata.fda.gov](https://www.accessdata.fda.gov/drugsatfda_docs/label/2024/021064s033lbl.pdf)\n\n---\n*Topic: Encyclopedia › Life and health › Human health and medicine › Clinical assessment and procedures › Medical imaging and radiography › Ultrasound and echocardiography*\n\n*Initially written Sep 29, 2026 · Reviewed: Sep 30, 2026 · Edited: Sep 30, 2026 · Last review: Sep 30, 2026*\n\n*Copyright 2026 EdgeChat AI, a subsidiary of Biostate AI.*\n\nLicense: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license\n", "same_as": [], "url": "https://www.edgepedia.org/contrast-echocardiography", "markdown_url": "https://www.edgepedia.org/contrast-echocardiography.md", "license": { "name": "Edgepedia Community License 1.0", "url": "https://www.edgepedia.org/edgepedia/license", "summary": "Free with credit, commercial use included. AI training is open to everyone. For other uses, organizations over USD 100M in revenue or 100M monthly users license separately.", "spdx": "LicenseRef-Edgepedia-Community-1.0" }, "credit": "\"Contrast echocardiography\", Edgepedia (EdgeChat), https://www.edgepedia.org/contrast-echocardiography. Edgepedia Community License 1.0.", "credit_md": "\"[Contrast echocardiography](https://www.edgepedia.org/contrast-echocardiography)\", Edgepedia (EdgeChat), [https://www.edgepedia.org/contrast-echocardiography](https://www.edgepedia.org/contrast-echocardiography). [Edgepedia Community License 1.0](https://www.edgepedia.org/edgepedia/license).", "credit_html": "\"Contrast echocardiography\", Edgepedia (EdgeChat), https://www.edgepedia.org/contrast-echocardiography. Edgepedia Community License 1.0.", "speakable": "Contrast echocardiography is cardiac ultrasound performed after intravenous injection of gas microbubbles that opacify the blood pool, used when up to 20% of echocardiograms have poor endocardial border definition." }