Physicians with more experience are better able to detect a third heart sound that is an indicator of heart disease, according to a study on stethoscope accuracy in cardiac patients at UCSF Medical Center.
Greater experience in auscultation-- listening to body sounds with a stethoscope-- provides better outcomes in detecting pathologic heart disorders, underscoring the importance of skilled instruction in the use of a stethoscope, the researchers said. Their findings appear in the March 27, 2006, edition of The Archives of Internal Medicine.
The third heart sound, known as S3, is a low-pitched vibration that occurs in early diastole, a phase in the heart's pumping cycle characterized by the rhythmic relaxation and dilatation of the heart chambers. While present in children and adolescents, the sound normally diminishes in adulthood.
"The presence of an S3 is associated with adverse cardiovascular outcomes in adult patients," said senior author Andrew Michaels, MD, assistant professor of cardiology at UCSF and co-director of the Cardiac Catheterization Laboratory at UCSF Medical Center. "The pathologic S3 indicates decreased compliance of the ventricles of the heart and may be the earliest sign of heart failure."
The researchers compared auscultative abilities of four groups of physicians, each representing a different level of training and experience: board-certified cardiology attending physicians, cardiology fellows, internal medicine residents and internal medicine interns. Phonocardiography, a computerized heart sound analysis, was used as a comparison.
Ninety patients between the ages of 24-91 preparing to undergo non-emergency left-sided heart catheterization for a clinical evaluation were enrolled in the study. The phonocardiography detected a third heart sound in 23 percent of these patients. The researchers found agreement between physician and phonocardiography results improved with a greater level of physician experience, with attendings and fellows having the highest amount of agreement. Interns had no significant agreement with the phonocardiography results. Phonocardiography performed better than any physician group in identifying the third heart sound.
"These findings demonstrate the capacity for physicians to effectively auscultate a clinically important S3 and we believe they can be generalized to the practicing physician and physician-in-training," said lead author Gregory Marcus, MD, cardiology fellow at UCSF. "The full realization of this capacity requires both continuing interest on the part of the learner and mentorship and teaching by those with expertise."
Patients underwent additional tests to further determine the level of heart function, including echocardiography to measure left ventricular ejection fraction (LVEF), a measure of the strength of contraction, and cardiac catheterization for measurement of left ventricular end-diastolic pressure (LVEDP). Blood levels of B-type natriuretic peptide (BNP) were also measured in each patient. BNP is a neurohormone secreted from the cells of the heart in response to stretching of the heart walls and has been shown to be clinically useful in diagnosing heart failure.
Patients with an S3 generally had a significantly higher BNP, lower LVEF and higher LVEDP than those with no S3. Once again, the findings showed the more experienced physicians had a higher correlation between detecting S3 and these clinical markers.
The researchers point out that poor performance by physicians in hearing the third heart sound may be a cause for a lack of clinician confidence in the value of using auscultation as a diagnostic tool. Current research shows medical students receive little training in auscultation and physicians are increasingly reliant on more sophisticated technology, such as echocardiograms and BNP levels to provide information about heart function. Despite the current trend, the researchers argue that the presence of an S3 sound is clinically meaningful and should be utilized more often.
"Identifying the S3 sound is important in the diagnosis of heart disease, requires relatively little time and is accessible to any physician with a stethoscope," added Marcus. "This is especially important because patients and their physicians do not always have immediate access to the latest diagnostic tools capable of detecting problems with the heart."
The research was funded by an unrestricted educational grant from Inovise Medical Inc., and from the Division of Cardiology at UCSF.
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