A practical guide to the lung ultrasound for the assessment of congestive heart failure

Dyspnea is one of the major symptoms encountered in the emergency department, and lung ultrasound (LUS) is recommended for the rapid diagnosis of the underlying disease. B-lines, the "comet-tail"-like vertical lines moving with respiration, are an ultrasound finding relevant to the pulmonary congestion. They may be observed in the normal lung, but bilateral, ≥ 3 B-lines are considered pathological. B-lines with lung sliding (B profile) are a specific sign of heart failure, while B-lines with abolished lung sliding (B' profile) are related with the lung diseases such as acute respiratory distress syndrome. B profile is reported to detect pulmonary edema with about 95% sensitivity and 95% specificity in patients with dyspnea. LUS also can assess the severity of pulmonary congestion semi-quantitatively by counting the number of B-lines or that of positive areas. Whereas the original BLUE protocol requires scanning at 12 zones on the chest, more rapid 8- or 6-zone scan is sufficient for the diagnosis of heart failure, and 2- or 4-zone scan may be used for the critical patients. LUS may be used for the evaluation of heart failure treatment, or can be performed as a part of exercise stress test. LUS can be performed easily and rapidly at the bedside using almost any kind of ultrasound apparatus, and it should be performed more widely in the daily practice as well as in the emergent department.