B-Lines on Lung Ultrasound During Stress Echocardiography
- B-lines on stress echocardiography appear to be associated with worse clinical outcomes in terms of death and nonfatal MI.
What are the functional and prognostic correlates of B-lines during stress echocardiography (SE)?
In this prospective, multicenter study, transthoracic echocardiography (TTE) and lung ultrasound (LUS) were performed among 2,145 patients referred for exercise (n = 1,012), vasodilator (n = 1,054), or dobutamine (n = 79) SE at one of 11 sites in six countries (Brazil, Bulgaria, Italy, Poland, Russian Federation, and Serbia). Using the same transducer for TTE and LUS but adjusting transducer depth, LUS was evaluated in four sites. B-lines were defined as discrete laser-like vertical hyperechoic reverberation artifact arising from the pleural surface and extending to the screen bottom without fading or moving synchronously with lung sliding, and scored at each of the four scanned sites on a 0- to 10-point scale. SE analysis included: a) new regional left ventricular (LV) wall motion abnormalities in two contiguous segments; b) reduced LV contractile reserve (defined as the ratio of peak-to-rest LV force [calculated as systolic blood pressure over LV systolic volume]; threshold ≤2.0 for exercise and dobutamine, ≤1.1 for vasodilators); c) abnormal coronary flow velocity reserve (defined as peak hyperemic to rest diastolic mid-left anterior descending peak flow velocity; threshold ≤2.0); and d) abnormal heart rate reserve (defined as peak to resting heart rate; threshold ≤1.80 for exercise and dobutamine, ≤1.22 for vasodilators). All patients completed follow-up.
Patients were divided into four groups based on B-line score at peak stress: group I, absence of stress B-lines (score 0-1, n = 1,389 [64.7%]); group II, mild B-lines (score 2-4, n = 428 [20%]); group III, moderate B-lines (score 5-9, n = 209 [9.7%]); and group IV, severe B-lines (score ≥10, n = 119 [5.4%]). During a median follow-up of 15.2 months (interquartile range, 12-20 months), there were 38 deaths and 28 nonfatal myocardial infarctions (MIs) in 64 patients. On multivariable analysis, severe stress B-lines (hazard ratio [HR], 3.544; 95% confidence interval [CI], 1.466-8.687; p = 0.006), abnormal heart rate reserve (HR, 2.276; 95% CI, 1.215-4.262; p = 0.01), abnormal coronary flow velocity reserve (HR, 2.178; 95% CI, 1.059-4.479; p = 0.03), and age (HR, 1.031; 95% CI, 1.002-1.062; p = 0.04) were independent predictors of death and nonfatal MI.
The authors concluded that severe stress B-lines on LUS performed during SE predict death and nonfatal MI.
B-lines on LUS are a sign of pulmonary congestion (see central illustration). The appearance of B-lines during SE presumably is mediated by a stress-induced increase in pulmonary capillary wedge pressure; earlier work has correlated the appearance of B-lines during SE with LV ischemia and/or LV diastolic dysfunction. This manuscript suggests that the appearance of B-lines during (predominantly exercise and vasodilator) SE was associated with worse outcome in terms of death or nonfatal MI. It is not clear whether or how patient management was influenced by the SE results. It also is not clear whether these findings have incremental clinical value.
Keywords: Blood Pressure, Diagnostic Imaging, Dobutamine, Echocardiography, Stress, Exercise Test, Heart Failure, Myocardial Infarction, Myocardial Ischemia, Pulmonary Wedge Pressure, Ultrasonography, Vasodilator Agents, Ventricular Dysfunction, Left
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