Ultrasound lung comets (ULCs) are a nonionizing bedside approach to assess extravascular lung water. We evaluated a protocol for grading ULC score to estimate pulmonary congestion in heart failure patients and investigated clinical and echocardiographic correlates of the ULC score. Ninety-three patients with congestive heart failure, admitted to the emergency department, underwent pulmonary ultrasound and echocardiography. A ULC score was obtained by summing the ULC scores of 7 zones of anterolateral chest scans. The results of ULC score were compared with echocardiographic results, the New York Heart Association (NYHA) functional classification, radiologic score, and N-terminal pro-b-type natriuretic peptide (NT-proBNP). Positive linear correlations were found between the 7-zone ULC score and the following:
In patients with congestive heart failure or intravascular volume overload, redistribution of fluids within the lungs leads to pulmonary edema. Excessive extravascular lung water (EVLW) accumulates in the interstitial and alveolar spaces, due to elevated left ventricular (LV) filling pressures [
Lung ultrasound is a noninvasive and nonionizing imaging technique that has been previously proposed as a bedside tool for evaluating pulmonary congestion in patients with heart failure [
Echocardiography is a noninvasive tool which provides a good understanding of the functional and hemodynamic information in heart failure patients. The ability to evaluate ULCs on lung ultrasound may provide further insight into the clinical and pathophysiological involvement of the lungs. The present study assessed the performance of a simplified ULC scoring system for evaluating pulmonary congestion and investigated clinical and echocardiographic correlates of the ULC score.
This was a prospective study. The Ethics Committee of Beijing Chaoyang Hospital approved the protocol, and all patients provided informed consent.
During a 6-month period, from August 2015 to January 2016, we studied patients with congestive heart failure who satisfied the modified Framingham criteria [
Patients with the following were excluded: age < 18 years, atrial fibrillation, mitral stenosis, and pulmonary disease. A diagnosis of pulmonary disease was based mainly on clinical symptoms, chest radiograph, and blood tests. Also excluded were patients with an abnormal pleural line observed by linear probe because B-lines can arise due to interstitial lung disease [
A linear probe was used to exclude noncardiac ULCs. (a) Normal pleura line and cardiac ULCs. (b, c) The abnormal pleural line could also generate ULCs (which are best visible under real-time examination), and they were confirmed by high-resolution computed tomography as interstitial lung disease and pneumonic infiltrate, respectively.
Cardiac and lung echographic examinations were performed before intravenous diuretic therapy. All patients were analyzed in the supine, near-to-supine, or lateral position. An experienced operator (HL) with 8 years of echographic examination experience and 2 years of lung ultrasound experience performed the examinations, using Philips CX50 (Philips Ultrasound, Bothell, Washington, USA) with S5-1 phased-array probe (1–5 MHz) and L12-3 linear probe (3–12 MHz).
Before the echographic examinations, a bedside anteroposterior chest X-ray was performed with the patient in the supine position. Scoring of pulmonary congestion was determined through a previously validated radiologic score incorporating assessment of variables (Table
Radiologic score variables.
Variables | Score | ||
---|---|---|---|
Mild | Moderate | Severe | |
Hilar vessels | |||
Enlarged | 1 | 2 | 3 |
Increased in density | 2 | 4 | 6 |
Blurred | 3 | 6 | 9 |
Kerley lines | |||
A | 4 | 8 | |
B | 4 | 8 | |
C | 4 | 8 | |
Micronodules | 4 | 8 | |
Widening of interlobar fissures | 4 | 8 | 12 |
Peribronchial and perivascular cuffs | 4 | 8 | 12 |
Extensive perihilar haze | 4 | 8 | 12 |
Subpleural effusion | 5 | 10 | |
Diffuse increase in density | 5 | 10 | 15 |
All patients underwent transthoracic echocardiography examination at bedside. In accordance with the recommendations of the American Society of Echocardiography, the LV end-diastolic and end-systolic diameters (LVEDD and LVESD, resp.) were measured from the M-mode trace, obtained via a parasternal long-axis view. Left ventricular end-diastolic and end-systolic volumes (LVEDV and LVESV), ejection fraction (LVEF), and left atrial volume were obtained from 2-chamber and 4-chamber views using the biplane Simpson’s method and indexed to body surface area. The peak Doppler velocities of early (
After the transthoracic echocardiography examination, all patients underwent transthoracic lung ultrasonography with the same phased-array transducer. Seven zones were considered in our simplified ULC scoring method. The anterior chest wall was delineated from the sternum to the anterior axillary line and was subdivided into upper and lower halves, from the clavicle to the diaphragm. The lateral zone was delineated from the anterior to the posterior axillary line and was subdivided into upper and lower halves (the area above the fourth intercostal space was defined as the upper area). We initially adopted an 8-zone protocol, but inclusion of the anterior lower area on the left side was subsequently removed, because most of the study population had an enlarged heart which intervened with the area. Therefore, the 7-zone protocol was adopted.
The elementary findings that were evaluated were the ULCs (also known as B-lines), defined as hyperechogenic, vertical comet tail artifacts with a narrow base, spreading from the pleural line to the further border of the screen [
According to the increasing order of severity of interstitial or alveoli involvement, images were classified as zero, septal syndrome, interstitial-alveolar syndrome, or white lung [
Increasing severity of interstitial or alveoli involvement. (a) Normal lung; B-lines are absent. (b) Septal syndrome; B-lines are about 7 mm apart, corresponding to subpleural septa. (c) Interstitial-alveolar syndrome; B-lines are confluent. (d) White lung. B-lines have coalesced, resulting in an echographic lung field that is almost completely white.
The stored images of each patient were scored one month after the baseline assessment, by the same investigator (HL) who performed the corresponding transthoracic ultrasonography examination. Interobserver reliability was assessed by another observer (WZ) by dynamic clips in a set of 20 cases. Each investigator was blinded to the previous results.
We also scanned the pleural line with a high-resolution linear probe, to exclude pneumogenic ULCs (Videos
Standard descriptive results are expressed as mean and standard deviation, and categorical data are expressed as percentage. Correlations between variables were assessed by Spearman’s 2-tailed method. Independent correlates of ULC score were identified by multiple linear regression analyses after logarithmic transformation of NT-proBNP. The coefficient of differences among 3 groups was compared using one-way analysis of variance. To assess intraobserver and interobserver reliability, the ULC scores were calculated by a weighted kappa statistic. The diagnostic utility of transthoracic echocardiography in detecting moderate or severe pulmonary congestion symptoms was determined using receiver-operating characteristic (ROC) curves. The best threshold was obtained by selecting the point on the ROC curve that maximized both sensitivity and specificity. Comparisons of the values of two groups were performed using the independent-samples Student’s
During the study period, 93 heart failure patients with dyspnea were enrolled (Table
Patients’ clinical characteristics.
Variables | Mean ± SD or number (%) |
---|---|
Subjects, |
93 |
Age, y | |
Gender, female/male | 32/61 |
Body surface area, m2 | |
Hypercholesterolemia | 40 (43) |
Diabetes | 20 (22) |
Previous MI |
16 (17) |
PCI |
10 (11) |
CABG |
4 (4) |
NT-proBNP, pg/ml | |
Radiologic score | |
NYHA functional class | |
II | 28 (30) |
III | 56 (60) |
IV | 9 (10) |
Cause of heart failure | |
Coronary artery disease | 64 (69) |
Hypertension | 14 (15) |
Dilated cardiomyopathy | 7 (8) |
Myocarditis | 4 (4) |
Perinatal cardiomyopathy | 1 (1) |
Autoimmunity cardiomyopathy | 1 (1) |
Alcoholic cardiomyopathy | 2 (2) |
Assessments of ULCs were performed in all patients (feasibility = 100%). Bilateral diffuse B-lines were identified in all patients by lung ultrasound [
The kappa values for the intra- and interobserver reliabilities of the simplified ULC score assessment were 0.92 and 0.90, respectively.
Significant linear correlations were found between the simplified ULC score and radiologic score (
The mean LVEF was 36% (range: 20%–55%; Table
Patients’ echocardiographic characteristics.
Variables | Mean ± SD |
---|---|
LV ejection fraction, % |
|
LV end-diastolic diameter, mm |
|
LV end-systolic diameter, mm |
|
LVEDV, mL/ |
|
LVESV, mL/ |
|
LAV, mL/ |
|
SPAP, mmHg |
|
TAPSE, mm |
|
GLS, % |
|
LV: Left ventricular; LVEDV: left ventricle end-diastolic volume; LVESV: left ventricle end-systolic diameter; LAV: left atrial volume; index: divided by BSA (body surface area); SPAP: systolic pulmonary artery pressure; TAPSE: tricuspid annular plane systolic excursion; GLS: global longitudinal strain.
There was a significant correlation between the simplified ULC score and each of the following: average
Correlation between ULC score and
Figure
Lung ultrasound and echocardiographic parameters of a patient with congestive heart failure. (a) Interstitial-alveolar syndrome was detected by lung ultrasound. (b) Mitral inflow showed
The multivariate analysis showed that the only variables independently associated with ULC score were
The patients were stratified into 3 groups by LVEF ≥ 40% (
ULC scores by diastolic function grade and left ventricle ejection fraction (LVEF).
ULC score |
| ||
---|---|---|---|
LV diastolic function grade | Grade I |
|
<0.001 |
Grade II |
|
||
Grade III |
|
||
|
|||
LV ejection fraction (LVEF) | LVEF ≥ 40% |
|
0.52 |
LVEF 25–39% |
|
||
LFEF < 25% |
|
The optimal cutoff value of ULC score according to the ROC curve was 8 for predicting NYHA ≥ 3 (i.e., moderate or severe congestion symptoms according to NYHA [
Patients with ULC scores < 8 and ≥8
Variables | ULC score | | |
---|---|---|---|
<8 ( |
≥8 ( | ||
|
|
|
<0.0001 |
SPAP, mmHg |
|
|
<0.0001 |
GLS, % |
|
|
0.14 |
LV ejection fraction, % |
|
|
0.55 |
LVEDD, mm |
|
|
0.46 |
|
|
|
0.57 |
|
|
|
0.66 |
TAPSE, mm |
|
|
0.06 |
LV diastolic function grade | <0.05 | ||
Grade I | 7 (19) | 1 (2) | |
Grade II | 18 (49) | 26 (46) | |
Grade III | 12 (32) | 29 (52) | |
Mitral regurgitation | <0.001 | ||
Mild | 27 (73) | 19 (34) | |
Moderate | 8 (22) | 25 (45) | |
Severe | 2 (5) | 12 (21) | |
NYHA functional class | <0.001 | ||
II | 20 (54) | 11 (20) | |
III | 15 (41) | 33 (59) | |
IV | 2 (5) | 12 (21) | |
Age, y |
|
|
<0.05 |
NT-proBNP, pg/ml |
|
|
<0.0001 |
Radiologic score |
|
|
<0.0001 |
An ROC curve was plotted to predict further for moderate-to-severe pulmonary congestion symptoms. (i.e., ULC score ≥ 8; Figure
ROC curves showing the diagnostic performance of
The primary objective of the present study was to evaluate a simplified protocol for scoring ULCs to estimate pulmonary congestion in heart failure patients. This 7-zone protocol was compared with the echocardiographic results, NYHA functional classification, radiologic score, and NT-proBNP. We found that the 7-zone ULC score correlated with LV diastolic functional parameters, SPAP, GLS, the severity of mitral regurgitation, NYHA functional classification, radiologic score, and NT-proBNP. Multivariate analysis identified the
ULCs are multiple comet tails and a simple echographic sign of EVLW [
Serum NT-proBNP is a biomarker that is widely used for diagnosing heart failure, although the sensitivity and specificity are not perfect. The use of NT-proBNP coupled with lung ultrasound could significantly improve the diagnostic accuracy in determining heart failure [
A recent study used a simplified 4-sector method and reported good correlation with EVLW values derived from transpulmonary thermodilution [
For patients with suspected heart failure, echocardiography is an essential imaging tool that can be used to measure LV systolic and diastolic function, estimate pulmonary capillary wedge pressure (PCWP) and SPAP, and evaluate LV filling pressure [
However, unlike the above studies, we found that the LVEF was somewhat less informative for predicting the degree of lung congestion. The discrepancy in results could be due to different study populations. Ours was limited exclusively to a cohort of identified left heart failure patients with pulmonary congestion. In some contexts, it has been shown that the signs and symptoms of congestive heart failure correlate poorly with LVEF [
An enlarged left heart is suggestive of chronically elevated LV filling pressure. A normal left heart volume is often noted in patients with acute increase in LV filling pressures or in the earliest stage of diastolic dysfunction. However, our study population included patients with a history of chronic heart failure; and this may be the reason for the inconsistency between left heart volume and pulmonary congestion degree.
In the present study, we offer a simplified ULC scoring method to estimate the degree of congestion that considered only 7 thoracic zones. This tool is less refined than counting all the B-lines in 28 sectors but provides easy-to-acquire data in an emergency setting, and it is much easier to differentiate 4 types of ULC patterns than it is to count B-lines.
The study may be considered limited by the lack of patients with atrial fibrillation and mitral stenosis. A goodly proportion of patients with heart failure experience these conditions, especially those with preserved LVEF [
Our conclusions are based only on imaging evaluations and echocardiographic indices. While B-lines are thought to reflect EVLW, there is no reference standard available to verify the EVLW volume and left atrial pressure (LAP) by invasive catheter.
This novel simplified ULC scoring method is a rapid, noninvasive, and reliable tool to assess pulmonary congestion in patients with heart failure. Diastolic rather than systolic performance may be the most important determinant of the degree of lung congestion in these patients.
The authors declare that they have no conflicts of interest.
This work was supported by the NSFC (National Natural Science Foundation of China; no. 81571683), the Fund of Clinical Application of Capital Project (Z141107002514074), and the Fund of Health Development and Scientific Research of Capital Projects (no. 2014-2-1061).
Videos 1–4. Normal lung and three types of ULCs in ultrasound images which indicate increasing severity of interstitial or alveoli involvement.
Video 1: Normal lung; B-lines are absent.
Video 2: Septal syndrome; B-lines are scattered (about 7 mm apart) corresponding to the distance of subpleural septa.
Video 3: Interstitial-alveolar syndrome; B-lines are confluent.
Video 4: White lung; B-lines have coalesced, resulting in an echographic lung field that is almost completely white.
Note. Classification of images is according to the distribution of B-lines with the “highest” score in the respiratory cycle (Videos 2–4).
Videos 5–7. Linear probe was used to exclude noncardiac ULCs (abnormal pleural line could also generate ULCs).
Video 5: Normal pleura line and cardiac ULCs.
Video 6: Fringed pleural line indicates interstitial lung disease.
Video 7: Irregular pleural line with microconsolidations.