Classic and Novel Echocardiographic Signs: A Review

1. Introduction

Echocardiography is a first-line imaging tool for assessing cardiovascular diseases [1,2,3,4,5,6,7,8,9]. Echocardiographic signs are specific patterns or findings on echocardiography that have been described to aid in diagnosis, help clinicians remember key features, and serve as teaching tools. These signs are often named after several conventions, including metaphors, eponyms, descriptive features, acronyms, etc. This paper aims to provide an overview of classic signs in echocardiography, including the McConnell’s Sign, the D-Sign, the 60:60 Sign, the SAM Sign, and the Swinging Heart Sign, focusing on their naming logics, definitions, and clinical implications to facilitate a better understanding of classic echocardiographic signs, and to first propose three novel signs, the Three Pipes Sign, the LTS Sign, and the LTI sign, which may aid in diagnosis and serve as teaching aids in echocardiography.

2. Classic Echocardiographic Signs

We provide an overview of classic echocardiographic signs, including McConnell’s Sign, the D-Sign, the 60:60 Sign, the SAM Sign, and the Swinging Heart Sign. These signs are associated with a spectrum of cardiovascular conditions, including acute pulmonary embolism, hypertrophic cardiomyopathy, and pericardial effusion. For each sign, we review its naming logic, definition, and clinical implications.

2.1. McConnell’s Sign

Naming logic: McConnell’s Sign is named after its original describer, first described by McConnell et al. in 1996 [10].

Definition: McConnell’s Sign refers to an echocardiographic finding of segmental right ventricular wall motion abnormality with apical sparing [11,12]. First described by McConnell et al. in 1996 [10], it is an echocardiographic sign highly specific for acute pulmonary embolism and may guide rapid intervention when other testing is not feasible.

Clinical implications: McConnell’s Sign is specific for acute pulmonary embolism. It can be demonstrated at the bedside with a transthoracic echocardiogram and may guide therapeutic intervention [11,12,13,14,15].

2.2. The D-Sign

Naming logic: the D-Sign is named for its resemblance to the letter “D” [16].

Definition: The D-Sign is when the left ventricle assumes the shape of the letter “D” instead of its normal circular appearance [16]. It occurs when early diastolic right ventricular pressure exceeds that of the left ventricle and indicates right ventricular pressure overload.

Clinical implications: The D-Sign is an echocardiographic marker of right ventricular pressure overload and can be seen in acute right ventricular failure, RV dilatation, pulmonary embolism, or chronic pulmonary hypertension [17,18].

2.3. The 60/60 Sign

Naming logic: The 60:60 Sign is named for the two numerical cutoff values it comprises.

Definition: The 60/60 Sign is a 2D transthoracic echocardiographic finding defined by the combination of a pulmonary acceleration time of less than 60 ms and a tricuspid regurgitation jet gradient of less than 60 mmHg. It is highly specific but poorly sensitive for the diagnosis of pulmonary embolism [19,20].

Clinical implications: The 60/60-Sign is highly specific for pulmonary embolism. When present, it can confirm the diagnosis of pulmonary embolism and support immediate clinical decision-making, but its low sensitivity means it cannot be used to exclude the diagnosis. Additionally, it serves as an independent predictor of 30-day mortality, warranting heightened clinical vigilance and more aggressive management in positive cases [21,22].

2.4. The SAM Sign

Naming logic: The SAM Sign is named as an abbreviation for “systolic anterior motion”.

Definition: The SAM Sign is the abbreviation for “systolic anterior motion of the mitral valve.” It refers to the abnormal movement of the anterior mitral valve leaflet toward the interventricular septum during systole, which obstructs the left ventricular outflow tract. This is a classic echocardiographic finding in hypertrophic cardiomyopathy [23,24,25].

Clinical implications:

This sign can serve as important diagnostic evidence for obstructive hypertrophic cardiomyopathy. It can also be observed after aortic valve replacement, mitral valve repair, and acute myocardial infarction [23,24,25,26,27,28,29,30].

2.5. The Swinging Heart Sign

Naming logic: The Swinging Heart Sign is named for the descriptive appearance of the heart swinging within a large pericardial effusion.

Definition: The Swinging Heart Sign is diagnosed when a standard view of the left ventricle reveals that the right ventricular anterior wall, the interventricular septum, and the left ventricular posterior wall all move in the same direction throughout the cardiac cycle. Often, identification of specific valvular or other intracardiac structures is not possible [31].

Clinical implications: The swinging heart pattern appears to be a reliable marker of cardiac tamponade in the setting of a large pericardial effusion, except in those patients with intrapericardial lesions which mechanically limit cardiac motion [32,33,34,35,36,37,38].

In summary, these five classic echocardiographic signs each carry important diagnostic value in specific cardiovascular conditions. McConnell’s Sign, the D-Sign, and the 60:60 Sign serve as important clues for pulmonary embolism, with the 60/60 Sign additionally providing prognostic information regarding 30-day mortality. The SAM Sign is a key diagnostic feature of obstructive hypertrophic cardiomyopathy, while the Swinging Heart Sign is a reliable marker of cardiac tamponade in the setting of large pericardial effusion. Together, these signs not only facilitate rapid recognition and differential diagnosis of conditions such as pulmonary embolism, hypertrophic cardiomyopathy, and pericardial effusion, but also serve as effective teaching tools for consolidating the key echocardiographic manifestations of these diseases. The summary of classic echocardiographic signs is shown in Table 1.

3. Novel Echocardiographic Signs

We first propose two novel echocardiographic signs, the Three Pipes Sign and the LTS Sign, which are associated with coarctation of the descending aorta and dilated cardiomyopathy, respectively. For each sign, we describe its naming logic, definition, and clinical implications.

3.1. The Three Pipes Sign

We propose the “Three Pipes Sign” as a novel sonographic sign to aid in the recognition of the suprasternal long-axis view of the aortic arch when the three major branches are adequately displayed, and to assist in the echocardiographic localization and measurement of coarctation of the descending aorta based on the relationship of the narrowing to these three branches.

Naming logic: The sign is named for its descriptive appearance, as the three major branches of the aortic arch resemble three pipes.

Definition: The “Three Pipes Sign” refers to the sonographic appearance of the suprasternal long-axis view of the aortic arch in which the three major branches, namely the brachiocephalic trunk, left common carotid artery, and left subclavian artery, may be visualized arising from the aortic arch, appearing as three parallel or slightly diverging tubular structures, together resembling three pipes.

Clinical implications: The “Three Pipes Sign” serves three purposes: (1) Recognition of the scanning plane: The sign provides a simple, intuitive pattern of three tubular structures arising from the aortic arch, which may help sonographers, particularly trainees, recognize the suprasternal long-axis view of the aortic arch when the three branches are adequately displayed. (2) Assessment of aortic anomalies: Adequate display of the three branches provides the anatomical framework for the echocardiographic localization and measurement of coarctation of the descending aorta. The location of coarctation is defined by its relationship to the innominate artery, left common carotid artery, and left subclavian artery. Thus, the “Three Pipes Sign” provides the necessary anatomical guide for localizing coarctation of the descending aorta. (3) Scanning quality control: The sign may help confirm adequate visualization of the aortic arch and its three major branches.

3.2. The LTS Sign

We propose the “LTS” as a novel sonographic sign for dilated cardiomyopathy.

Naming logic: LTS is an abbreviation for the “Large-Thin-Small” triad.

Definition: The “LTS” refers to the echocardiographic appearance of dilated cardiomyopathy characterized by three features: (1) large ventricular cavity, (2) thin interventricular septum, and (3) small mitral valve orifice, the initials of which yield the “Large-Thin-Small” triad: LTS.

Clinical implications: The “LTS” serves two purposes: (1) Recognition of dilated cardiomyopathy: The sign provides a simple mnemonic: Large, Thin, Small. This may help echocardiographers, particularly trainees, recognize the typical echocardiographic features of dilated cardiomyopathy. (2) Teaching tool: The sign offers trainees a simple mnemonic to help them remember the three core features.

3.3. The LTI Sign

We propose the “LTI” as a novel sonographic sign for endocardial fibroelastosis.

Naming logic: LTI is an abbreviation for the “Large-Thick-Impaired” triad.

Definition: The “LTI” refers to the echocardiographic appearance of endocardial fibroelastosis characterized by three features: (1) large ventricular cavity, (2) thick endocardium, and (3) impaired ventricular function, the initials of which yield the “Large-Thick-Impaired” triad: LTI.

Clinical implications: The “LTI” serves two purposes: (1) Recognition of endocardial fibroelastosis: The sign provides a simple mnemonic: Large, Thick, Impaired. This may assist echocardiographers, especially trainees, in recognizing the characteristic echocardiographic features of endocardial fibroelastosis. (2) Teaching tool: The sign provides trainees with an easy mnemonic to help them remember the three core features.

In summary, the Three Pipes Sign, the LTS Sign, and the LTI Sign are three novel echocardiographic signs that may aid in diagnosis and serve as teaching aids. The Three Pipes Sign provides a simple, intuitive pattern for recognizing the suprasternal long-axis view of the aortic arch when the three major branches are adequately displayed. It may serve as a useful teaching tool for trainees, as a sonographic guide for the localization and measurement of coarctation of the descending aorta based on the relationship of the coarctation to the three branches, and as an aid in scanning quality control. The LTS Sign summarizes the three core echocardiographic features of dilated cardiomyopathy, namely large ventricular cavity, thin interventricular septum, and small mitral valve orifice, into a memorable mnemonic. It may serve as a useful teaching tool for trainees and as an aid in echocardiographic evaluation. The LTI Sign summarizes the three characteristic echocardiographic features of endocardial fibroelastosis, including large ventricular cavity, thick endocardium, and impaired ventricular function, into a memorable mnemonic. It may serve as a helpful teaching tool for trainees and an aid in echocardiographic assessment. The signs are simple, straightforward, and may be valuable for trainees in learning and remembering key sonographic findings. The summary of novel echocardiographic signs is shown in Table 2.

4. Limitations

This review has several limitations. First, the three novel signs are proposed based on established sonographic anatomy and echocardiographic knowledge, and their clinical utility will require further assessment in routine practice. Second, this review is not a systematic review, and the selection of signs is based on the authors’ judgment rather than a comprehensive literature search.

5. Future Directions

Looking forward, echocardiography continues to evolve with advances in technology and imaging techniques. We hope that more novel, simple, and memorable echocardiographic signs will be proposed to aid in the recognition of important scanning planes, the identification of specific cardiovascular conditions, and the teaching of echocardiography to trainees. With the increasing integration of artificial intelligence in echocardiography, there may be opportunities to automatically detect these signs, further enhancing their clinical utility and educational value.

Inspired by the educational value of echocardiographic signs, we also note that terminological precision in echocardiographic parameters may have implications for teaching. Tricuspid annular plane systolic excursion (TAPSE) is one such parameter that warrants consideration. While it is a well-established parameter for the measurement of right ventricular longitudinal systolic function, its name does not explicitly indicate that the measured excursion is longitudinal. A more precise term, TAPSLE, which is an abbreviation for tricuspid annular plane systolic longitudinal excursion, may therefore be considered to better reflect the longitudinal nature of this parameter and to enhance teaching and clinical communication. We encourage further discussion among the echocardiography community on the potential adoption of TAPSLE in practice.

6. Conclusion

Echocardiographic signs help clinicians recognize characteristic imaging patterns and facilitate accurate diagnosis. In this review, we have summarized five classic echocardiographic signs, namely McConnell’s Sign, the D-Sign, the 60:60 Sign, the SAM Sign, and the Swinging Heart Sign, each of which carries important diagnostic value in specific cardiovascular conditions. We have also first proposed three novel signs, the Three Pipes Sign, the LTS Sign, and the LTI Sign, which may aid in the recognition of the suprasternal long-axis view of the aortic arch, the echocardiographic features of dilated cardiomyopathy, and those of endocardial fibroelastosis, respectively. For each sign, we have described its naming logic, definition, and clinical implications, highlighting how these signs may serve not only as diagnostic clues but also as effective teaching aids. We hope that this review facilitates a better understanding of classic echocardiographic signs and encourages the continued development of simple, memorable signs to enhance both clinical practice and echocardiography education.