Conventional phonocardiography is useful for objective assessment of cardiac auscultation, but its availabil-ity is limited. More recently, an ankle-brachial index (ABI) measurement system equipped with simple phono-cardiography has become widely used for diagnosing peripheral artery disease, however, whether this simple phonocardiography can be an alternative to conventional phonocardiography remains unclear. This retrospective study consisted of 48 patients with hypertrophic cardiomyopathy (HCM) and 107 con-trols. The presence of the fourth sound (S4) was assessed by conventional phonocardiography, in addition to apexcardiography and auscultation, in all patients with HCM. S4 was also estimated by the ABI measurement system with the phonocardiographic microphone on the sternum (the standard method) or at the apex (the apex method) in HCM patients and controls. S4 on conventional phonocardiography was detected in 42 of 48 patients (88%) with HCM. Auscultation for the detection of S4 had a sensitivity of 0.78, specificity of 0.57, and accuracy of 0.75. These diagnostic val-ues were generally superior to those of the standard method using the ABI measurement system, whereas the apex method using the ABI measurement system had better diagnostic values, with an excellent specificity of 1.0, sensitivity of 0.77, and accuracy of 0.80. No significant differences were observed in low ABI defined as < 0.9. Simple phonocardiography equipped with the ABI measurement system may be an alternative to conven-tional phonocardiography for the detection of S4 in patients with HCM when the phonocardiographic micro-phone is moved from the sternum to the apex.
