Figure 1

(a–c) illustrate how we identified an area of interest that included the second heart sound (S2) using automated detection of the R and T waves in the ECG to an area of approximately 30% of the cardiac cycle on the phonocardiogram. The x –axis shows time in seconds and the y-axis is the relative amplitude of the signals. Figure 1a. Simultaneous phonocardiographic and electrocardiographic tracings. We illustrate simultaneous phonocardiographic and electrocardiographic tracings with an example of a 20 second recording of the phonocardiogram (top tracing) and electrocardiogram (lower tracing) in a patient with normal pulmonary artery pressures (mean PA pressure <25 mmHg). Automatically detected R-waves of the QRS complex are marked with an O, and T-waves are marked with an X. The second heart sound (S2) window is identified in the algorithm as 30% of the cardiac cycle around the T wave. Figure 1b. Simultaneous phonocardiographic and electrocardiographic tracings of a single cardiac cycle. The phonocardiographic and electrocardiographic tracing from a single cardiac cycle from the same subject and recording in Figure 1a,c. Identifying the window that included S2 on the phonocardiogram. There is a 0.25 second window around the T wave, which, identified the area of interest, used in the algorithm. The loudest signal in the boxed area was designated the second heart (S2) shown in the phonocardiogram at approximately 0.1 seconds on the x-axis.