Quantification of vertical “B-lines” on lung ultrasound (LUS) is being used increasingly often to quantify pulmonary congestion for diagnosis, monitoring, and prognosis of patients with acute or chronic heart failure (HF). A recent systematic review published in Echocardiography suggests B-lines can also provide prognostic information beyond Killip class in patients with acute myocardial infarction (AMI).
Researchers at Brigham and Women’s Hospital have become the first to study the long-term trajectory of LUS findings after AMI. They conclude in the European Heart Journal Acute Cardiovascular Care that quantification of B-lines could facilitate early detection, quantification, and monitoring of pulmonary congestion in AMI patients.
The authors are Elke Platz, MD, MS, director of the Ultrasound Research Core Laboratory and director of Translational Ultrasound in the Division of Cardiovascular Medicine, Brian Claggett, PhD, assistant professor in the Division, Amil Shah, MD, co-director of the Cardiac Imaging Core Laboratory, and colleagues.
Assessment of pulmonary congestion with LUS was a prespecified exploratory analysis performed as part of the echocardiographic substudy of PARADISE-MI. That trial randomized 5,661 patients with AMI to sacubitril/valsartan or ramipril in 41 countries between 2016 and 2020.
Twenty-five sites from 11 countries participated in the LUS substudy between March 2018 and January 2021. 152 patients (mean age 65, 32% women) had adequate LUS images at baseline, and 141 had adequate images eight months later or at the end of the study. Paired examinations were available for 115 patients.
B-lines and Clinical Characteristics
132 patients (87%) had detectable B-lines at baseline. As expected, those with a greater number of B-lines were more likely to have presented with a higher Killip class and to have had pulmonary congestion documented at baseline by clinical signs, chest X-ray or chest CT.
However, 55% of patients with Killip class I at screening had ≥3 B-lines at baseline, the definition of subclinical pulmonary congestion in this study. ≥3 B-lines were also evident in 56% of patients who qualified for PARADISE-MI based on left ventricular ejection fraction <30% at screening (without evidence of pulmonary congestion on physical examination, X-ray or CT).
Changes in B-lines
The median follow-up period was 16 months. Among the 115 patients with paired examinations, there was an overall decline in B-lines from baseline (mean, −1.6; P=0.018). In that subgroup, the proportion of patients with <3 B-lines at follow-up was:
- 53% among the 40 patients who had 0–2 B-lines at baseline
- 39% among the 44 patients who had 3–7 B-lines at baseline
- 36% among the 31 patients who had ≥8 B-lines at baseline (P=0.003)
The composite long-term outcome was death from cardiovascular causes or incident HF (n=18; 12%), whichever occurred first. Incident HF included hospitalization for HF or outpatient episodes of symptomatic HF treated with intravenous or sustained oral diuretic therapy.
Although the eight-month event rates for the composite outcome were numerically higher among patients with a higher B-line count at baseline,
these differences were not statistically significant. Furthermore, adjusted for baseline, there were, on average, six more B-lines at follow-up in a patient who experienced an HF event than a patient who did not (P=0.001).
B-lines and Cardiac Structure and Function
Worse pulmonary congestion at baseline was associated with prognostically important echocardiographic markers: larger left atrial size, higher E/e′, higher E/A ratio, greater degree of mitral regurgitation, worse right ventricular systolic function, and higher tricuspid regurgitation velocity (P-trend <0.05 for all).
Currently, the assessment of pulmonary congestion is subjective and variable. LUS shows promise for not just detecting but also quantifying subclinical pulmonary congestion following AMI. The use of LUS findings could facilitate the identification of patients with AMI who are at high risk of developing HF and enable earlier initiation of HF therapy.