Chin Med J (Taipei) 1998;61:S104.

Noninvasive Evaluation of the Cardio-vascular Function

Chen-Huan Chen, M.D.

Veterans General Hospital-Taipei, Taipei, Taiwan, R.O.C.

Abstract

Mechanical properties of the heart and vessels are important to both the understanding of the pathophysiology of heart diseases and the implication of effective therapy. Previously cardiovascular functions can only be assessed by invasive catheterization techniques. Recently, several noninvasive approaches are emerging for routine clinical use. This presentation will describe some of the available methods that can be applied clinically easily.

Vascular function: Distensibility of a segment of artery can be evaluated by measuring pulse wave velocity using arterial tonometry or Doppler flow. The extent of peripheral arterial wave reflection can be assessed by registering the wave contour of the common carotid artery and estimate the augmentation index. The central aortic wave contour can be synthesized by mathematical transformation of the noninvasively derived radial pressure wave and it can be used to calculated several cardiovascular index, including total compliance, tension time index, diastolic time index, and subendocardial viability.

Ventricular function: Left ventricular systolic function is most frequently assessed by ejection fraction or cardiac output, which are affected profoundly by loading conditions. Ventricular systolic property can be effectively characterized by the instantaneous change of the ratio of pressure versus volume (elastance function). The maximal value of the elastance function (Emax) is considered as a loadindependent contractility index. It was demonstrated that the normalized left ventricular elastance function curves are very similar across a large number of cardiac patients regardless of their disease status. By applying a generalized normalized left ventricular elastance function, it is now possible to estimate Emax from several simple measurements during steady state, including systolic and diastolic blood pressures, left ventricular end-sytolic and end-diastolic volumes, and timing of the ventricular systole and diastole relative to the peak of R wave of ECG. This novel approach has great potential for wide clinical use because all parameters required for calculation can easily be obtained noninvasively.

In conclusion, with the emerging new techniques, precise evaluation of the cardiovascular function can now be performed by simple noninvasive approaches. It is expected that these new noninvasive methodologies will be used widely both in research and clinical judgement in the near future.

[Chin Med J (Taipei) 1998;61:S104.]