AIM: Is pocket echo the new stethoscope?

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The rapid acquisition of images by skilled ultrasonagraphers who use pocket mobile echocardiography (PME) yields “accurate assessments” of ejection fraction, and some, but not all, cardiac structures in many patients, based on a cross-sectional, single-center study published July 4 in the Archives of Internal Medicine.

Recently, a cellphone-sized PME device (Vscan, GE Healthcare)  designed to do the same job as transthoracic echocardiography (TTE) became commercially available for clinical use. However, data on the accuracy of the device are limited.

Therefore, Max J. Liebo, MD, and colleagues from Scripps Clinic in La Jolla, Calif., sought to compare the accuracy of rapidly acquired PME images with those acquired by standard TTE.

For the study, at the time of referral for TTE, ultrasonagraphers acquired PME images first in five minutes or less. The ultrasonagraphers were not blinded to the clinical indication for imaging or to PME image results when obtaining standard TTE images. However, two experienced echocardiographers and two cardiology fellows who were blinded to the indication for the study and TTE results, but not to the device source, interpreted the PME images.

The researchers gathered a convenience sample of 97 patients consecutively referred by echocardiography. They measured for visualizability and accuracy (the sum of proportions of true-positive and true-negative readings and observer variability) for ejection fraction, wall motion abnormalities, left ventricular end diastolic dimension, inferior vena cava size, aortic and mitral valve pathology and pericardial effusion.

Liebo and colleagues reported that the physician-readers could visualize some, but not all, echocardiographic measurements obtained with the PME device in every study. The highest proportions were for ejection fraction and left ventricular end diastolic dimension (95 percent each); the lowest proportion was for inferior vena cava size (75 percent). Accuracy also varied by measurement (aortic valve was 96 percent [highest] and inferior vena cava size was 78 percent [lowest]) and decreased when non-visualizability was accounted for (aortic valve was 91 percent and inferior vena cava size was 58 percent).

“Observer agreement was fair to moderate for some measurements among less-experienced readers,” wrote the authors, who added that the rates of false-negatives ranged from 1 to 13 percent for attendings and 2 to 8 percent for fellows.
For cost considerations, the device currently costs $7,900, and there is no reimbursement category for performing or interpreting PME. However, the researchers said that the “rapid PME are free, in comparison with TTE, which is associated with a technical and professional fee exceeding $1,500 and an average of 40 minutes of an ultrasonagrapher’s time per study.”

Liebo et al noted that their findings are “promising,” but suggested further testing of the PME device in a larger patient cohort with diverse cardiac abnormalities and with untrained clinicians obtaining and interpreting images is required before wide dissemination of the device can be recommended.

The National Institutes of Health was the primary source of funding for the study.