Cardiac Examination: Stethoscope or Pocket Echo—Why Not Both?
Portable echocardiographic devices were first introduced in 1978.1 As technology has evolved, they have become smaller and more comprehensive. At present, pocket echos (pocket-sized, hand-held cardiac ultrasounds), which cost less than $1000 can, in 5 to 10 minutes, produce data very similar to that obtained by a standard echo examination of the heart. At present (United States, 2016) there is no payment for examinations by the pocket device.
The pocket echo examination can be performed at the point of care, at the bedside or in the clinic, whereas a standard echo examination must be scheduled, takes 45 to 60 minutes, and costs several thousand dollars.
Multiple studies have shown that an echo examination of the heart performed with a hand-held device produces data very similar to that of a standard echo examination. How does a pocket echo examination, performed and interpreted by a cardiologist trained to interpret echos, compare with a cardiac examination by a cardiologist without an echo examination?
The pocket echo can accurately provide data regarding left ventricular (LV) function (LV ejection fraction, LV enlargement, LV hypertrophy, cardiomegaly) that the cardiologist can only infer by the patient’s signs and symptoms.
In addition to providing assessment of LV function at the bedside, the pocket echo may detect valvular lesions that may be missed on physical examination.
Several studies have shown that the pocket echo can recognize subtle evidence of rheumatic valve disease in asymptomatic patients who do not have an audible murmur. For this reason the pocket echo is preferred to the clinical examination for detecting asymptomatic rheumatic heart disease in children in underdeveloped nations. Detection of asymptomatic rheumatic heart disease is an indication for penicillin therapy to prevent further valvular damage.
How about interpretation of murmurs in symptomatic or asymptomatic patients? These patients are usually referred for a standard echo examination, which may involve a several day wait.
Can a pocket echo or a physical examination by a cardiologist exclude the presence of significant valvular heart disease and thereby decrease the need for a standard echo examination?
Multiple studies using the standard echo as the gold standard have shown that neither the pocket echo nor physical examination by a cardiologist is perfect.
In one of the largest studies, Vourvouri et al compared physical examination by a cardiologist with a pocket echo examination and with a standard echo examination in 52 patients with valvular heart disease. Compared with the standard echo, physical examination missed 23 of the 52 valvular lesions, compared with 4 of 52 missed by pocket echo.
In each case the valvular lesion was judged to be greater than mild by standard echo. However, some of the patients in whom the valvular lesion was missed by the cardiologist but detected by the pocket echo may have been asymptomatic, and the murmur may not have been audible.
Spencer et al compared the clinical examination and pocket echo examination with standard echo in patients with a total of 127 valvular lesions. Compared with a standard echo, cardiologists missed 43% of major findings, whereas the pocket echo missed 21% compared with standard echo.
Kahn et al compared the results by pocket echo with a standard echo in 288 patients with valvular lesions. Pocket echo failed to detect aortic insufficiency in 19 (21%) of 90 patients and in 12% of 142 patients with mitral insufficiency. All 13 patients with mitral stenosis and 43 with aortic stenosis were detected by the pocket echo.
Galasko et al performed pocket and standard echo examinations in 562 subjects in a community screening program. The pocket echo failed to detect 3 (16%) of 19 patients who were diagnosed with aortic or mitral insufficiency by standard echo.
In addition to missing some cases of aortic or mitral insufficiency, several investigators have reported that the pocket echo may over- or under-estimate the severity of these 2 lesions.
The pocket echo is least likely to miss the presence of aortic or mitral stenosis.
The pocket echo can help to reduce the number of unnecessary negative standard echos. When the physical examination by a cardiologist and the pocket echo agree that there is no evidence of significant heart disease, referral for a standard echo examination can be avoided. If the physical examination or echo shows evidence of valvular heart disease, a standard echo is indicated to determine the severity of the lesion.
If I were a young physician beginning a career as a cardiologist, I would obtain a pocket echo and become an expert in its use!
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-James E. Dalen, MD, MPH
This article originally appeared in the July 2016 issue of The American Journal of Medicine.