Use of acoustic cardiography—combining a 12-lead ECG with cardiac acoustic data—rather than a stethoscope, can help physicians detect the abnorm al S3 rhythm that has been linked to cardiac disease and heart failure (HF) in certain subsets of patients, according to a substudy of the HEARD-IT tri al published online July 14 in the American Journal of Emergency Medicine.
“The S3, although highly specific for acute HF and predicting death and readmission, is often difficult to auscultate,” the authors wrote. “The low-frequency, low-pitch sound is notoriously very difficult to hear with a stethoscope alone.”
Acoustic cardiography technology uses two dual-function sensors capable of simultaneously capturing the heart's electrical and sound characteristics.
Alan S. Maisel, MD, of the Veterans Affairs San Diego HealthCare System, and colleagues analyzed data of 995 patients enrolled in the HEARD-IT ( HEart failure and Audicor technology for Rapid Diagnosis and Initi al Treatment) tri al conducted across nine sites from March 2006 to October 2006. The HEARD-IT tri al assessed the diagnostic accuracy of adding the acoustic cardiography tool (Audicor, Inovise Medical) to an emergency medicine physician’s toolkit.
During this study, Maisel et al focused on three subsets of patients: the obese, those with kidney failure and those with an intermediate level of B-type natriuretic peptides, a biomarker linked to HF and cardiovascular risk.
The patients analyzed were all dyspneic emergency department patients who were 40 years of age or older and not on dialysis.
Two cardiologists who were blinded to the acoustic cardiography results determined the gold standard of acute HF diagnosis.
The researchers found that “S3 strength was a significant prognosticator in univariate analysis for adverse events but not in a multivariable model.”
However, use of acoustic cardiography in patients who had levels of a B-type natriuretic peptides between 100 pg/mL and 499 pg/mL increased the diagnostic accuracy of acute HF by 22 percent, from 47 percent to 69 percent.
Similarly, researchers found that use of acoustic cardiography in obese patients improved S3 detection sensitivity compared to the use of auscultation.
"Our findings suggest we diagnose heart failure only about half the time in these patients without acoustic cardiography,” says Collins. "With it, we improve the accuracy to about 70 percent. It’s pretty helpful in this subs et of patients.”
Collins offered that use of this technology could help better diagnose patients with HF, especially patients who have other cardiac conditions, such as chronic obstructive pulmonary disease, that often make diagnosis more difficult.
“The strength of the S3 gallop provides rapid results that assist with identification of acute HF in selected populations. S3 detection complements the use of B-type natriuretic peptides in the gray zone, and its diagnostic/prognostic ability is largely unaffected by body mass index and ren al function,” the authors concluded.
“S3 strength shows promise as a diagnostic and prognostic tool in problematic HF subgroups.”
The study was funded by Inovise Medic al.