Although the electrophysiologic derangement responsible for atrial
fibrillation (AF) has been elucidated, how AF remodels the ventricular chamber
and affects diastolic function (DF) has not been fully characterized. The
previously validated Parametrized Diastolic Filling (PDF) formalism models
suction-initiated filling kinematically and generates error-minimized fits to
E-wave contours using unique load (xo),
relaxation (c), and stiffness (k) parameters. It predicts that
E-wave deceleration time (DT) is a function of both stiffness and relaxation.
Ascribing DTs to stiffness and DTr to relaxation such
that DT=DTs+DTr is legitimate because of causality and
their predicted and observed high correlation (r=0.82 and r=0.94) with
simultaneous (diastatic) chamber stiffness (dP/dV) and isovolumic relaxation
(tau), respectively. We analyzed simultaneous echocardiography-cardiac catheterization data
and compared 16 age matched, chronic AF subjects to 16, normal sinus rhythm
(NSR) subjects (650 beats). All subjects had diastatic intervals. Conventional
DF parameters (DT, AT, Epeak, Edur, E-VTI, E/E’) and
E-wave derived PDF parameters (c, k, DTs, DTr)
were compared. Total DT and DTs, DTr in AF were shorter
than in NSR (p<0.005), chamber stiffness, (k) in AF was higher than in NSR (p<0.001). For NSR, 75% of DT
was due to stiffness and 25% was due to relaxation whereas for AF 81% of DT was
due to stiffness and 19% was due to relaxation (p<0.005). We conclude that compared
to NSR, increased chamber stiffness is one measurable consequence of chamber
remodeling in chronic, rate controlled AF. A larger fraction of E-wave DT in AF
is due to stiffness compared to NSR. By trending individual subjects, this
method can elucidate and characterize the beneficial or adverse long-term
effects on chamber remodeling due to alternative therapies in terms of chamber
stiffness and relaxation.
Credits: Sina Mossahebi; Sándor J. Kovács