Left Ventricular Torsional Hysteresis: A Global Parameter for Diastolic Function

Diastolic dysfunction refers to abnormal mechanical properties of the myocardium and
includes abnormal LV diastolic distensibility, impaired filling and slow or delayed
relaxation- regardless of whether the ejection fraction is normal or depressed and whether
the patient is asymptomatic or symptomatic. Epidemiologic studies have demonstrated high
prevalence of diastolic heart failure (DHF). The quality of life of these patients is
impaired and the clinical outcomes are similar to those with heart failure with systolic
dysfunction. Therefore diastolic dysfunction has significant adverse economic impact that is
expected to grow further with time. Clinical characteristics alone may not be sufficient to
diagnose diastolic dysfunction. A number of invasive and non-invasive parameters have been
proposed to diagnose diastolic dysfunction. Most of the presently used non-invasive
parameters have a number of limitations. High fidelity measurement of the left ventricular
pressures is needed to accurately diagnose diastolic dysfunction. Obtaining it in routine
clinical practice is impractical.

In this protocol the investigators have proposed a novel non-invasive parameter called
'Torsional Hysteresis' as a measure of diastolic function. This will be measured using
non-invasive cardiac MRI technique. During left ventricular contraction and relaxation,
myocardium deforms. During cardiac cycle the myocardium goes back to baseline state prior to
beginning of each contraction. However the rate with which it returns to the baseline state
is variable. Torsion indicates relative wringing motion of the ventricle around a left
ventricular axis and is a global parameter of left ventricular deformation. The parameters
have defined a new parameter called torsional hysteresis based on non invasive cardiac MRI
assessment. The parameters have hypothesized that for diastolic dysfunction, the torsional
hysteresis area is increased as compared to no diastolic dysfunction group.