Lung ultrasound beats chest x-ray for heart failure detection

Point-of-care lung ultrasound has a higher sensitivity than chest x-ray for detecting symptoms of pulmonary edema in patients with acute decompensated heart failure (ADHF), according to a new meta-analysis. The findings could indicate that ultrasound is a better choice for these patients, according to a study published March 15 in JAMA Network Open.

Acute decompensated heart failure is defined as the immediate worsening of symptoms from heart failure, occurring when the heart is unable to adequately circulate fluid. Among the symptoms are leg swelling, fatigue, and dyspnea; indeed, ADHF is the primary cause of dyspnea in 40% of adults presenting to the emergency room, according to a research group led by Dr. Anna Maw of the University of Colorado.

Pulmonary edema is a classic sign of ADHF, with guidelines calling for the use of tools such as physical exam, brain-type natriuretic peptide (BNP) blood test, and chest x-ray. But diagnostic workup for the condition can be challenging, with chest x-ray providing false-negative results in 20% of cases.

Lung ultrasound at the bedside has been offered up as an alternative. The modality is fast and relatively easy to perform, and it does not involve the use of radiation. In fact, some studies have shown that ultrasound has equal or better accuracy than chest x-ray for most causes of dyspnea, the authors noted. Extravascular water content in the lungs can be visualized in a semiquantitative fashion by the number of B-lines on ultrasound scans.

The authors, therefore, decided to perform a meta-analysis of research studies that have been performed comparing lung ultrasound to chest x-ray for patients with ADHF. After applying exclusion criteria, they ended up with six clinical studies performed between 2011 and 2017 at various sites around the world. In all, the studies included results from 1,827 patients.

The researchers reported sensitivity and specificity for both the individual studies and the six studies combined. When pooled, the performance of lung ultrasound was better than chest x-ray in terms of sensitivity in detecting pulmonary edema in ADHF patients. For specificity, on the other hand, they found no statistically significant difference between the modalities.

Chest x-ray vs. lung ultrasound for ADHF patients
	Chest x-ray	Lung ultrasound	p-value
Pooled sensitivity	0.73	0.88	p < 0.001
Pooled specificity	0.90	0.90	p = 0.96

How do the numbers translate into patient care?

"For every 100 patients presenting with dyspnea owing to cardiogenic pulmonary edema, [lung ultrasound] can diagnose 15 more cases than [chest x-ray] without an increase in the number of false positives," the authors noted.

Lung ultrasound could eventually become an accepted initial staging modality for the evaluation of patients with dyspnea. The authors recommended prospective studies to see if the modality improves diagnosis, treatment, and outcomes for these patients.