DK2985_C000 1..28 - AlSharqia Echo Club

Global Ventricular Function and Hemodynamics 193Figure 9.11 Changes in stroke volume, cardiac output, fractional area change, end-systolic elastance, maximal elastance, and preloadrecruitable stroke force in seven patients before and after cardiopulmonary bypass surgery (CPS). No significant changes were observedin stroke volume, cardiac output and fractional area change. However the indices based on the pressure–volume relationship were lowerafter CPS. [With permission of Gorcsan et al. (25).]B. Problems Confounding DiagnosisIn the evaluation of left ventricular function, several errorscan be made in the measurement of left ventricular dimensions.In the mid-esophageal four-chamber view, the apexof the LV can be foreshortened leading to underestimationof ventricular volume. Further retroflexion of the probe tipmay reduce the impact of this problem. A transgastricshort-axis view with an oblique cross section leads notonly to faulty measurements of left ventricular dimensions,but also to misinterpretation of regional wallmotion. Moderate to severe MR or ventricular septaldefect may result in a left ventricular ejection fractionwhich overestimates intrinsic myocardial contractility.The presence of MR allows the measurement of left ventriculardP/dt, a different index of left ventricular contractilityand function (Fig. 9.14) which can be used toestimate ejection fraction postoperatively (31). Finally,the estimation of left ventricular ejection fraction mayvary according to the site of measurement as one movesfrom the ventricular apex (75%) to the short axis (65%)to the base of the heart (50%). Longitudinal contraction(shortening of the left ventricle long axis) contributes10–15% of the ejection fraction.C. Transesophageal EchocardiographicEvaluationFigures 9.15–9.18 summarize our approach to the evaluationof ventricular function using four specific viewsthat allow the evaluation of both left and right ventricularsystolic and diastolic dysfunction and also mitral, aortic,and tricuspid valvular function.IV. ABNORMAL RIGHT VENTRICULARFUNCTIONA. ImportanceRight ventricular systolic dysfunction is associated withhigh morbidity after cardiac surgery (32,33), chest trauma(34) and with sepsis (35) and can be difficult to diagnose