The Sound of Silence

Corresponding Author

“Listen to the silence; it has so much to say.”

—Rumi (1)

The conventional clinical evaluation alone is not always accurate enough to assess patients in the critical care environment. In this context, point-of-care ultrasound (POCUS) has been increasingly incorporated into daily clinical practice. At the bedside, POCUS may help to differentiate a variety of acute cardiorespiratory disorders. Lung ultrasound (LUS) has shown a high added value when used for the bedside diagnosis of alveolar-interstitial syndrome because it is more accurate than chest radiography and clinical examination alone (2,3). There is evidence that POCUS could have a positive impact on patient outcomes and could potentially reduce the length of hospital stay (4).

The case highlighted by Kimura et al. (5) in this issue of JACC: Case Reports is an excellent example of the role of LUS as a diagnostic tool in acute care. They report the case of a patient who had only a mild, atypical presentation with substernal chest discomfort on effort with no other symptoms and whose LUS examination showed a picture of flash pulmonary edema demonstrated by a diffuse B-lines pattern. This asymptomatic flash pulmonary edema was caused by critical coronary artery disease and was a reflection of elevated left ventricular filling pressures induced by myocardial ischemia. This clinical case illustrates the role of LUS in detecting the dynamic elevation of extravascular lung water in the context of unstable ischemic heart disease, as hypothesized by Picano et al. (6) (Figure 1).

Figure 1.

The Lung Water Cascade in Ischemic Heart Disease

PCWP = pulmonary capillary wedge pressure.

From this case reported by Kimura et al. (5), we can see the vital role of LUS as a bedside screening tool in critically ill patients in emergency settings. It also demonstrates the high sensitivity of LUS in detecting alveolar-interstitial edema even in the absence of dyspnea. This sensitivity broadens our view of the role of LUS, and POCUS in general, in acute care settings. Moreover, we can see the value of handheld ultrasound devices in assisting in the diagnosis of life-threatening cardiorespiratory disorders, a practice that could prove very useful in limited-resource settings.

POCUS is increasingly recognized as an essential bedside diagnostic tool, and we may see it as an extension of the daily clinical examination. Although we do not foresee POCUS replacing our current diagnostic tools (e.g., chest radiography, stethoscope), we think that a comprehensive, integrated multimodality diagnostic approach will be the future of bedside clinical diagnosis and examination.

The presence of B-lines is the sonographic sign of interstitial-alveolar syndrome. These lines are vertical artifacts that start from the pleural line and extend to the far field of the ultrasound sector, typically moving with the pleural sliding with every breath. The number of B-lines correlates well with the degree of extravascular lung water (7). B-lines have also been found to have a 95% specificity and 97% sensitivity for the diagnosis of pulmonary edema (8).

Therefore, the number and pattern of B-lines (B-profile) can be used to track dynamic changes in pulmonary congestion and to monitor the response to therapy (9). This evolving body of evidence has led to incorporating B-lines assessment by LUS in international heart failure guidelines.

However, challenges exist regarding the future use of POCUS in acute cardiac care. POCUS data should be interpreted with caution and in the appropriate clinical context. It should be used as part of an integrated approach that includes clinical, laboratory, and other imaging tools. Supervised training and accreditation are essential to ensure quality control while maintaining patient safety. Focused ultrasound examinations performed by clinicians who only had a basic level of training may not be appropriate in the assessment of complex cardiothoracic patients who are critically ill and whose ultrasound studies often require more advanced skills. POCUS in these patients should be performed with a thorough understanding of the pathophysiology and hemodynamics of each case.