Quantitative determination of the filling (diastolic) function of the heart has been
primarily correlative rather than causal and has been thwarted by the inability to
define sensitive and specific non-invasive numerical indexes. In analogy to impedance,
Z(omega)=V(omega)/I(omega) relating voltage V to current I in circuit theory, we introduce
the concept of frequency-based analysis of diastolic function (DF) by analyzing the
left ventricular (LV) filling pressure (P) to flow(Q) relation in terms of impedance
as, Z(omega)=P(omega)/Q(omega). This allows abnormal DF to be viewed as a state of
impedance mismatch between pressure and flow, relative to normal. Simultaneous pressure-flow
data in 11 subjects was recorded during catheterization. Analysis of variance between
groups (ANOVA) shows that the direct current (DC) component of impedance, Z(0) and
the first harmonic coefficient, Z(1), differentiated between normal and abnormal DF
groups (p<0.05). We conclude frequency-based analysis of DF differentiates between
normal and abnormal DF states, elucidates the physiology of normal filling as a low-pass
filter and has potential as a method for noninvasive DF quantitation.
