The Expanding Role of Echocardiography in Patients with Heart Failure

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Systolic Function

The assessment of left ventricular systolic function was one of the earliest applications of echocardiography dating back to the M-mode era. Currently, 2-D approaches that incorporate both imaging and Doppler methodology are widely used for this purpose with realtime and reconstructive 3-D techniques recently added.

Echocardiographic methods can provide multiple indices of global function that include widely used but relatively load-dependent ejection phase indices such as left ventricular ejection fraction, fractional shortening and fractional area change. There is also a simple method for determining left and right ventricular dP/dT based on continuous wave Doppler recordings of mitral and tricuspid regurgitant jets respectively. This (dP/dT) is an afterload independent index of ventricular performance.

Until recently, echocardiographic determinations of load-independent indices of myocardial contractility such as end-systolic elastance and preload recruitable stroke work have been based on pressure-volume and pressure-area loops. These have required commercially available ultrasound equipment with automatic boundary detection capability and offline custom computer applications. Importantly, they have also 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 M-mode 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.

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References
  1. A full discussion of these techniques is beyond the scope of this article and the reader is referred to an excellent review on the subject by Nagueh, et al., in the American College of Cardiology Current Journal Review (Jan/Feb 2002).