Left Ventricular Torsional Hysteresis: A Global Parameter for Diastolic Function

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.

Inclusion Criteria:

Major inclusion criteria: Normal screening LV ejection fraction.

Exclusion Criteria:

1. Atrial fibrillation or other significant cardiac arrhythmia on ECG
2. Presence of pacemaker or defibrillator
3. Angioplasty or primary coronary intervention PCI/PTCA during index cardiac catheterization.
4. Patient is unable to undergo cardiac MRI due to contraindication to MRI (MRI incompatible metal prosthesis or implants or significant claustrophobia).
5. Patient taking phosphodiesterase 5 inhibitor (eg. sildenafil) will be excluded due to potential interaction with nitroglycerin.