Second Heart sound recording quantitatively documents systemic pressure changes. Scatter plots demonstrating relationship between sensor Second Heart Sound amplitude % changes (y axis) and systemic pressure rest-peak changes values (x axis) in the whole group of 146 patients. Red symbols: exercise stress; green symbols: dipyridamole stress; blue symbols: pacing stress. Left panel: systolic pressure (SBP) changes. Middle panel: diastolic pressure (DBP) changes. Right panel: mean pressure (MP) changes.