The left ventricular vibration mode in the ventricular transfer function method and at the moment of the first heart sound.

Several investigators have aimed to clarify the patient's left ventricular (LV) physical properties by free vibration analysis of heart sound. Recently we have developed a transfer function (TF) method to calculate the LV viscoelasticity. To clarify whether this TF method and a clinical first heart sound (1 HS) analysis are based on the identical ventricular vibration mode analysis, we examined (1) the visualized LV vibration image in the TF method and (2) the quantitative relationship between the peak frequency of the 1 HS spectrum and that of TF curve in the early and late phase of the 1 HS. Isolated isovolumic potassium arrested canine left ventricles were used to visualize the vibration mode in describing the TF (N = 2). Examination of stroboscopically illuminated, slow-motion images revealed the oscillation of the ventricle to be of mode 2 behavior. To analyze the quantitative relation between the TF method and 1 HS analysis we used ten open-chest dogs. The correlation was good (r = 0.917) when the peak frequency of the TF curve at the early phase of the 1 HS was compared to the peak frequency of the 1 HS. We concluded that both the TF method and 1 HS analysis were based on the common, second-order ventricular vibration mode. Therefore, some information on the ventricular physical properties suggeted by the TF method could also be included in the clinical data obtained by 1 HS analysis.