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Hand-held Ultrasound and the Stethoscope

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The stethoscope was invented in the early 19th century. It is now the most readily recognized tool of the physician and healthcare worker, yet its demise has been wrongly but repeatedly foretold over the years. This usually occurs when other diagnostic tools are invented and gain popularity. There is an old tale of an early 20th-century radiologist who placed a stethoscope prominently for all to see in a coffin-shaped display case. It was his mistaken belief that X-ray of the heart would shortly render the stethoscope obsolete.

More recently, and the point of this article, a small ultrasound machine is being hailed as the new stethoscope.This is bolstered by recent medical literature bemoaning the loss of auscultation skills by the latest generation of doctors. Physician reliance on the stethoscope has indeed decreased. A 21st-century medical student is initially exposed to cardiac auscultation with inspiring lectures that often incorporate innovative electronic teaching techniques of heart sounds. This usually spurs their enthusiasm for the stethoscope. After all, it is the symbol of their chosen profession. This shortlived enthusiasm for auscultation is evident during their rotations in the clinical third and fourth years, where they examine real patients with a stethoscope. Unfortunately, soon afterwards, when time becomes precious during their internship and residency, they seem to come to the inevitable conclusion that the ultrasound machine is much more expeditious and accurate in establishing a cardiac diagnosis. Their interest in further learning the fine points and nuances of using a stethoscope wanes. This is especially true if there is no knowledgeable mentor available to teach them the fine art of honing their still immature auscultation skills. Auscultation role models are hard to find. It becomes more practical to order an ultrasound study than to spend time listening to the heart.

Over the last 30 years, cardiac ultrasound (usually referred to as echocardiography) has emerged as a powerful diagnostic tool for patients with heart disease. It has dramatically altered the diagnostic approach in children with congenital heart disease. Echocardiography has virtually replaced cardiac catheterization as the primary diagnostic tool in most of pediatric cardiology. In adult cardiology, echocardiography has emerged as a convenient and reliable first-line method of testing in most cardiac disorders. At the same time, the scientific literature on echocardiography has validated its extensive diagnostic capabilities.

Echocardiography provides extensive anatomic and functional information about the heart. It often clarifies stethoscopic, electrocardiographic, and X-ray findings. Both the stethoscope and the ultrasound exam of the heart provide physical evidence of abnormalities, but the ultrasound may be more informative at an earlier stage of a disease. For example, ultrasound can actually measure the strength of cardiac muscle in heart failure. The stethoscope will only provide such evidence late in the course of the disease when the heart actually begins to enlarge and fail. Ultrasound can help identify which coronary artery caused a heart attack. Readily available ultrasound may shorten the time it takes to make a diagnosis. It can identify causes of chest pain other than heart attacks, altering the treatment of patients dramatically and providing correct life-saving diagnosis in many cases.

Nevertheless, it is unwise to alter the customary sequence of evaluating a patient in most cases. After obtaining a history from a patient, a physical examination (including auscultation) should be performed. At that point, the stethoscope may reveal that a calcified valve has caused this patient to faint. Detailed ultrasound using the high-end equipment will still be required to decide whether to proceed with an operation to replace the valve. An out-of-sequence cursory or limited ultrasound examination performed during the initial evaluation may not reveal the true extent of the problem.

As ultrasound technology improves, the image resolution gets progressively better, but there is still a significant minority of patients that are difficult to image. In those people it is occasionally necessary to insert an ultrasound probe into the esophagus to image the heart without obstruction from ribs or from lung tissue. It is called transesophageal echocardiography (TEE).This is a semi invasive procedure that is fairly safe, but does carry some degree of discomfort. It has revolutionized the medical treatment of some heart rhythm disorders and the surgical treatment of heart valve disorders and has become an indispensable tool in specialized heart centres.

There are now briefcase-sized ultrasound TEE machines. Smaller book-sized machines can be hand carried to the bedside and a transducer applied to the chest in much the same way as the stethoscope. They are less expensive than the standard high-end ultrasound machines and their price is expected to continue to drop. Ultimately, ultrasound machines may shrink down even further to the size of a personal digital assistant (PDA) or even a cell phone. The ultrasound transducers may become small enough to fit in a medical coat pocket just as easily as the stethoscope. Wireless transmission of the images has long been possible, further expanding portability.

Echocardiographic studies were initially recorded on videotape, but images are now increasingly being stored on computers and viewed in digital form. Digital storage may enable one to go from patient to patient with a relatively small device to obtain, store, and electronically transmit diagnostic ultrasound information. It is therefore not surprising that these small hand-held ultrasound machines are being hailed as the future replacement of a non-electronic instrument approaching its bicentennial.

Echocardiographic knowledge and experience are key concerns. Both scanning and interpretation require training and experience. In the US, echocardiographic procedures are typically performed by technician sonographers. The level of training and the quality of the training can vary. To work as a sonographer, one usually goes to an ultrasound school and then receives hands-on training. Sonographers are encouraged but not required to take a certifying examination. Echocardiographic studies are usually interpreted by cardiologists with specialized training. Cardiologists can become board-certified in echocardiography. In addition, an increasing number of echocardiography laboratories are voluntarily submitting to a lengthy and rigorous accreditation process that invariably improves the quality of the laboratory.

A resident or inexperienced physician performing an ultrasound study is highly unlikely to obtain the same information as an experienced sonographer or an experienced specialist. In many cases, incorrect information may be more harmful than no information.

Ready availability of hand-held ultrasound equipment may help make a critical diagnosis quickly. This can be in an emergency room in the middle of the night, in a critical care unit, in an ambulance, or even on the battlefield. If confined to certain disorders, hand-held ultrasound far exceeds the capabilities of the stethoscope. However, proper training in the use and limitations of the ultrasound instrument is mandatory.

Many places around the world are reporting shortages of experienced sonographers. Unleashing inexperienced, untrained personnel with scaled-down equipment is not the answer. The power of hand-held ultrasound is its point-of-care availability - it can make a diagnosis quickly, yet this is precisely where experience is important. One cannot afford to make the wrong diagnosis in a critical care setting. There may not be a second chance.

One approach to this dilemma is to recognize the hand-held device for what it is. It is a miniature version of the larger but more capable standard high-end ultrasound machine. Recognizing the differences between the two is fairly easy to instill in healthcare providers because there is a precedent. It is well known that transesophageal echocardiography may be necessary in some patients because the standard echocardiogram will not provide all the required information. Similarly, the standard echocardiogram may be necessary to supplement incomplete information obtained by the hand-held device. Once complete information is gathered by the standard high-end echocardiogram, it may be perfectly acceptable to use a hand-held device for a focused, goal-oriented limited follow-up study. As with other aspects of the practise of medicine, a qualified, properly trained health practitioner will need to assume responsibility (and will be held accountable) for how the information is obtained and interpreted. Proper record-keeping is essential. Reimbursement issues will doubtless also influence the eventual role of hand-held ultrasound in cardiac diagnosis and treatment.

Proper utilization is further refined by a plan to use the hand-held device extensively for bedside teaching of both patients and healthcare providers. A sonographer performing a study in an echocardiography laboratory without a physician is legally prohibited from discussing the echocardiographic findings with the patient. As a result, patients usually leave the echocardiography laboratory somewhat disappointed that the images of their heart were not explained to them during the study. On the other hand, a properly trained and credentialled physician coming to the bedside with a hand-held device can use it to educate the patient as well as the rest of the healthcare team. Such an approach can integrate the visual information from the ultrasound device with the auditory information from the stethoscope, thereby increasing skills in both techniques.

Many people feel that the stethoscope hanging around the neck of healthcare workers is already just a symbol, and no longer provides adequate diagnostic information. For the near future at least, stethoscopes should continue to hang there, waiting to be used by those who know auscultation, while echocardiograms (hand-held or standard) should be performed and interpreted by those who know echocardiography. Ôûá