required invasive monitoring of intraventricular pressure. Their use has been largely restricted to the research and intra-operative settings. Recently, however, advances in Doppler tissue imaging have created methods for realtime displays of myocardial strain and strain rate. These approaches overcome the fact that conventional Doppler tissue imaging is unable to differentiate active myocardial contraction from passive motion generated by translation of the heart or tethering of akinetic to contracting segments. Echocardiographic-derived strain and strain rates provide totally non-invasive load-independent indices of ventricular myocardial performance that correlate well with end-systolic elastance.

Diastolic Function

While echo-Doppler indices of diastolic function are widely used in patients with heart failure and normal systolic function, it is notable that these indices also have value in patients whose primary functional abnormality is systolic dysfunction. Echocardiographic methods for assessing left ventricular diastolic function include those based on pulsed Doppler recordings of mitral and pulmonary venous inflow, Doppler tissue imaging of the mitral annulus, and color Doppler Mmode recordings of mitral inflow.The latter is used to derive the propagation velocity, a load-independent index of relaxation. It is also possible to derive peak negative dP/DT by analyzing mitral regurgitant Doppler spectra.

The technology required to perform all these analyses is available on most commercially available systems and the time required to obtain a detailed assessment of diastolic function is minimal.

Myocardial erformance Index

The myocardial performance index, first introduced by Tei and colleagues, integrates myocardial systolic and diastolic function. It is defined as:

This easily derived index has been applied to both right and left ventricles.

Atrioventricular Valve Function

Functional mitral and tricuspid regurgitation frequently accompany left ventricular systolic dysfunction and may contribute significantly to patient symptomatology. Echocardiography has proved instrumental in delineating the pathophysiology of functional mitral regurgitation. A number of animal and clinical studies using both 2-D and 3-D techniques have demonstrated a path gnomonic pattern of leaflet closure termed apical tethering. One of the key causes of this disturbance of leaflet coaptation is increased tethering forces on the leaflets and chords created by geometric remodeling of the left ventricle and attendant papillary muscle displacement. By exerting traction at the site of leaflet insertion, annular dilation also contributes to pathologic leaflet tethering.

The other important causative factor is a reduced valvular closing force due to impaired left ventricular contraction. Functional tricuspid regurgitation appears to have a similar pathophysiology. It may occur on the basis of either primary right ventricular systolic dysfunction or due to the right ventricular remodeling that may develop in the setting of primary left-sided failure and secondary pulmonary hypertension.

Cardiovascular Hemodynamics

Over the last decade, the ability of echocardiography to define cardiac hemodynamics has been greatly expanded. One of the earliest applications of echocardiography was the determination of cardiac output based on calculating forward flow across the cardiac valves.This calculation is based on the fact that stroke volume equals the product of cross-sectional area and velocity time interval (the integrated area under the pulsed Doppler spectral curve) for flow per beat through that area. Although methods exist based on flow across each of the valves, those that relate to either the aortic or pulmonary outflow tracks are considered optimal since the orifice through which flow occurs is relatively constant in size and is easily modeled geometrically.

Echocardiography also provides simple methods for calculating pulmonary artery systolic and diastolic pressure based on the tricuspid and pulmonic regurgitant jets respectively.These methods are widely used clinically and have been extensively validated. Recently, a number of methods have been reported for determining left ventricular filling pressures.¹

These methods include approaches that are based on mitral and pulmonary venous inflow spectra, Doppler tissue imaging of the mitral annulus, and color Doppler M-mode of mitral inflow.