Year: 2019
Type: editorial
Abstract: This article refers to 'Lung ultrasound-guided treatment in ambulatory patients with heart failure: a randomized controlled clinical trial (LUS-HF study)' by M. Rivas-Lasarte et al., published in this issue on pages 1605–1613. In the last few years, lung ultrasound (LUS) has moved from a niche research tool to the clinical arena, and from intensive care units and emergency departments to cardiology and internal medicine.1 LUS is part of point-of-care ultrasound, which is the quintessence of clinical ultrasound. Its primary purpose is less about the examination of an organ (the lungs), but as a tool to answer a specific clinical question. While LUS is indeed an imaging study, it is fundamentally clinical in nature; some describe its clinical application as a kind of 'extended' physical examination. Indeed, insonation has recently been described as the 'fifth pillar' of bedside physical examination.2 Applying insonation to the lungs allows a rough semi-quantification of the degree of pulmonary deaeration. Thus, the utility of LUS spans multiple clinical settings, as documented by hundreds of studies worldwide.3 Ironically, visualization of B-lines is the most counterintuitive LUS sign: they are artefacts, appearing as comet tails across the screen. They do not directly depict the lung parenchyma; rather, B-lines indirectly inform us of the level of deaeration, which in a patient with heart failure (HF) represents, with very high probability, interstitial pulmonary oedema. A substantial body of work confirms the value of LUS in the HF setting (Table 1). The presence of B-lines narrows the differential diagnosis of acute dyspnoea.4 A recent randomized trial demonstrated B-lines together with clinical assessment improved diagnostic accuracy when compared to the current diagnostic approach of clinical assessment plus chest X-ray and N-terminal pro-B-type natriuretic peptide (NT-proBNP), and significantly reduced the time needed for a correct diagnosis.5 B-lines also predict outcomes; subclinical persistent congestion – defined by persistent B-lines at discharge – predicts rehospitalization.6, 7 Similarly, the presence of a higher number of B-lines in HF patients in the outpatient setting, predicts rehospitalization with acute pulmonary oedema and death.8-10 Despite the diagnostic and prognostic value of B-lines, what is unknown is whether B-lines are a target for therapy. Does LUS-guided therapy, even in the absence of clear signs and symptoms, improve HF patients' outcomes? Diagnosis Inpatients Outpatients ++++ +++ ++++ ++ Multiple, diffuse, bilateral B-lines rule in AHF. Absence of multiple, diffuse, bilateral B-lines rules out AHF ≥14 total B-lines Monitoring Inpatients ++ Variation of B-lines, with first significant reduction already less than 1 h after diuretic therapy A significant reduction of B-lines during hospitalization predicts rehospitalization for HF and death at 6 months Prognosis Inpatients Outpatients +++ +++ Persistent significant B-lines at discharge (>20/30 total B-lines) predicts rehospitalization for HF and death at 3 months A higher number of B-lines during out-office visit predicts hospitalisation for HF and death at 6 months The paper by Rivas-Lasarte et al.11 begins to fill this knowledge gap. In this single-blind trial, 123 patients hospitalized for HF were randomized to either standard follow-up or LUS-guided (plus usual care) follow-up. Both study arms required scheduled visits at 2 weeks, 1, 3, and 6 months after discharge. In the LUS-guided arm, treating physicians were encouraged to modify diuretic therapy according to the number of B-lines present on LUS. Ultimately, LUS-guided patients had better outcomes (hazard ratio 0.518, 95% confidence interval 0.268–0.998; P = 0.049) as defined by the primary composite endpoint (number of urgent visits, hospitalizations for worsening HF, and death from any cause). Compared to standard follow-up, the absolute risk reduction was 17%, resulting in a number needed to treat of 5. At first glance, this is a stunning accomplishment. Yet such a strong effect, coupled with wide confidence intervals and a marginally significant P-value warrants caution. Outcome differences were driven solely by a lower number of urgent visits for HF. No differences in rehospitalization or mortality were observed. Nor were there any differences in quality of life or NT-proBNP values. On the other hand, the LUS-guided arm had significantly greater improvements in the 6-min walk test, nearly doubling the distance (37 m vs. 60 m) compared with those in the standard follow-up group. They also received higher doses of loop diuretics, suggesting insonation may add to the traditional physical exam in detecting congestion.10 Nevertheless, these discordant secondary signals combined with no reduction in rehospitalization or mortality highlight the need for continued investigation. Other limitations of this study are worth noting as they highlight current limitations in the field. There are no clear cut-off values for B-lines to establish when a patient can be considered decompensated. In truth, different cut-offs likely apply to different patient populations, since the same number of B-lines in a patient with acute symptoms of HF have a different meaning than a patient with chronic HF or in patients without a history of HF. LUS studies in patients with HF continue to vary in protocol technique, both in terms of number of thoracic sites scanned12 and in the quantification/semi-quantification of B-lines.13 At present, the number of B-lines (quantity) is the dominant concern. Yet quality of B-lines, such as location in the chest (apical B-lines may highlight greater severity) and distribution may also matter. Importantly, B-lines, similar to any other biomarker, should not be viewed in isolation. Context matters: sonographic information must be integrated with our knowledge, experience and clinical judgment. Finally, as a single-centre study, it should be viewed more as a pilot experience; one that is promising and will hopefully lead to a multicentre study. Other studies are ongoing: the BLUSHED-HF study, which is a multicentre randomized pilot trial designed to test whether a LUS-guided treatment protocol outperforms usual care for reducing pulmonary congestion during emergency department stay14; and the LUST study, which shifts the idea of LUS-guided treatment to dialysis patients and has already provided some preliminary results.15 If confirmed by larger multicentre studies, the implications would be remarkable. LUS is easy to learn and patient friendly. Integrating LUS in the management of HF patients might tailor the approach to titrating therapies. The detection of B-lines, even in asymptomatic patients, would lead to further optimization of treatment, which in turn might reduce hospitalization. Ultimately, Rivas-Lasarte and colleagues are to be congratulated for their significant contribution towards HF management. Patients want to feel well and stay well; the LUS-HF study suggests adding ultrasound assessment will reduce urgent HF visits. Given the safety of LUS and its well established diagnostic and prognostic benefits, we strongly encourage its use. The next few years will yield greater insights into the value of LUS in HF; perhaps ultrasound lung comets will indeed guide us. Conflict of interest: none declared.
DOI: 10.1002/ejhf.1641
Authors: Luna Gargani, Robinson M. Ferre, Peter S. Pang
Language: English
Field: Medicine
Domain: Health Sciences
Open Access status: bronze
OpenAlex ID: W2996773926