Page 11 - CBAC Newsletter 2015

(DT) has been fractionated into its stiffness (DT ) and compensation in radial motion in order to preserve
s
relaxation (DT) components (DT=DT +DT) by analyzing stroke volume. These directional-filling attributes can be
r
s
r
E-waves via the PDF formalism. The method has been quantified by determining the longitudinal and
validated (27) with DT and DT correlating with transverse impedance of the chamber during filling.
r
s
simultaneous catheterization (MILLAR) derived stiffness (30) The results quantify the propensity for longitudinal
(dP/dV) and relaxation (tau) with r=0.82 and r=0.94, volume accommodation to be 30 times greater than
respectively. PDF based E-wave analysis (of 763 transverse volume accommodation. (31)
E-waves) from 15 age-matched PN (elevated E/E’) and
15 NL subjects (k, c or DT and DT) was analyzed. Characterization of the Effects of Weight Loss on
r
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Additionally, blinded (E’ not provided) analysis of 42 Diastolic Function and Aging of the Heart
subjects (30 subjects from unblinded training set and
12 additional subjects from validation set, 581 E-waves) The PDF formalism has been used in the investigation
showed that R(=DT /DT) had high sensitivity (0.90) and of the effects of caloric restriction and exercise induced
r
specificity (0.86) in differentiating PN from NL once E’ weight loss on diastolic function. We found that both
revealed actual classification. These results indicate caloric restriction and exercise induced weight losses
that PDF based diastolic function analysis can have salutary effects on diastolic function (20). In
differentiate NL vs. PN filling patterns without requiring addition, the PDF parameters of subjects with caloric
knowledge of E’. (28) restriction were more in line with PDF parameters
observed in a younger cohort, implying that caloric
Doppler Tissue Imaging restriction slows ‘aging’ in the normal heart (11).

Doppler Tissue Imaging (DTI) has become routine in Load Independent Index of Diastolic Function
diastolic function assessment. However, past technology
made it difficult to appreciate the shape of the DTI A persistent challenge in clinical assessment of diastolic
generated E’-wave and subsequent multiple annular function relates to assessing diastolic function from
oscillations, which were previously noted (6, 24, 25). data confounded by load. As discussed above, diastolic
Such oscillations may have been considered to be noise. function is characterized in terms of intrinsic parameters
Importantly, these annular oscillations obey the laws of (stiffness and relaxation) and extrinsic parameters
oscillatory motion and thereby are amenable to (load). Despite advancing imaging capabilities,
modeling and quantitation (17-19). With current traditional (Epeak/Apeak, VTI, AT, DT) and newer
technology, the presence or absence of oscillations can echo-derived indices (E/E’, strain, strain rate, Vp, etc.)
be assessed, as shown in the figures of references have all been found to be load-dependent. Thus there
18-19. is no currently available diastolic function index that
is load-independent and measures chamber stiffness
The information obtained from DTI holds great potential and relaxation. Hence, solution of the load-independent
for diagnosis of diastolic relaxation abnormalities. The index of diastolic function (LIIDF) problem is a worthy
absence of mitral annulus oscillation (MAO) is a good undertaking.
predictor of relaxation related diastolic dysfunction. In a
recent study, we found that patient groups without MAO Importantly, because of load- conventional echocardio-
tend to have prolonged τ and IVRT, lower Epeak/Apeak graphic indexes (such as E peak /A peak ) in healthy subjects
and E’-waves, and increased Epeak/E’ (16). With (>1) can be abnormal (<1), or in subjects with
advancing technology, cardiologists can easily and pathophysiology (E peak /A peak <1) become pseudo-
reliably utilize MAO to gain additional information about normalized and appear >1.
diastolic function.
Conventionally multiple beats are averaged to determine
Longitudinal vs. Transverse Filling Attributes a reported value. For example, for Epeak, one would
measure several consecutive E-waves, and then report
The ability to image longitudinal motion and radial the average Epeak. Thus DF information present in the
motion to high precision has permitted characterization beat-to-beat variation is lost due to averaging.
of spatially distinct compensatory mechanisms in
diastole. In other words, because maintenance of In previous work we solved the LIIDF problem.
cardiac output and stroke volume constitute the prime Physiologic insight into the mechanism of filling and
directives for survival, it follows that impairment of mathematical analysis of E-waves allows derivation of an
longitudinal motion should be accompanied by index that is conserved during load variation (23). The

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