During last years interest in diastolic function has increased
markedly. It has been reported that in two thirds of the patients with
congestive heart failure, there is a combined systolic and diastolic left
ventricular (LV) dysfunction, whereas in one third of the patients, systolic
function is normal and heart failure occurs solely on the basis of diastolic
dysfunction. Diastolic dysfunction is an important cause of morbidity in
patients with heart disease. It can be defined as the inability of the heart
to maintain normal pressure during left ventricular filling. It may be
caused by abnormalities in relaxation, increased stiffness or a
combination of both (Rodriguez, 1999).
The determination of diastolic dysfunction in patients with heart
failure is important in choosing the proper medical therapy (Bourdillon et
al., 1983; Soufer et al., 1985).
Hypertrophic cardiomyopathy (HCM) is a complex disorder
characterized by abroad spectrum of morphological, functional, and
genetic abnormalities (Brock 1957 and Spirito et al., 1989).
Many of the clinical and pathophysiological features of HCM
result from a complex disturbance of diastolic function (Sandersons, et
al., 1978, Pak, et al., 1996).
Altered diastolic function has been hypothesized to represent an
earlier manifestation of HCM before the development of left ventricular
hypertrophy (LVH), However data regarding the clinical utility of
imaging techniques that asses this parameter are limited (Carolyn, et al.,
2002).
Physical examination, electrocardiogram (ECG), and chest
radiographs are unreliable in making the diagnosis of LV diastolic
dysfunction in most individuals, and invasive measurements of cardiac
pressures, rates of LV relaxation, and LV compliance are costly,
clinically impracticable as they carry increased risk, and require special
catheters and software analysis programs (Little et al., 1990).
The situation changed with the development of echocardiography.
Because of its noninvasive nature, large numbers of normal individuals
and patients were studied and different LV filling patterns were
described, first with M-mode echocardiography (Hanrath et al., 1980)
and later using pulsed-wave (PW) Doppler technique interrogating mitral
inflow (Kitabatake et al., 1982; Takenaka et al., 1986).
Validation of these mitral filling patterns against radionuclide and
angiographic techniques soon followed (Rokey et al., 1985; Spirito et al.,
1986).
However, enthusiasm for relating LV filling patterns to diastolic
function was dampened by reports that the velocity and proportion of
early and late diastolic filling and their peak velocities were affected by
preload, (Stoddarad et al., 1989) afterload, and heart rate (Appleton,
1991).
Three basic abnormal filling patterns were described and were soon
found to have clinical significance and prognostic value regardless of
cardiac disease type. They are reversed E/A ratio, pseudonormalization
and restrictive patterns (Pinomontti et al., 1993; Oh et al., 1992).
The field of diastology using echo-Doppler evaluation was born
and steady progress continued (DeMaria and Blanchard D, 1999).
Today this LV diastolic evaluation includes interrogation of mitral andpulmonary venous flow velocities, and the evaluation of mitral annular
motion by Doppler tissue imaging (DTI). In addition, manipulation of
preload and afterload assesses how sensitive abnormal LV filling patterns
are to changes in loading conditions (Dumesnil et al., 1991; Hurrell et
al., 1997). Tissue Doppler echocardiography has the potential to
accurately measure the different phases of the cardiac cycle which until
now could only be determined invasively. It may provide a sensitive
method for the assessment of changes in both cardiac contraction and
relaxation in different clinical settings (Zamorano et al.,1997).
However, simple, practical indices for diastolic function evaluation
are lacking, but are much desired for clinical evaluation. |
