Final Feigenbaum’s Echocardiography DIGITAL

Chapter 5 Evaluation of Systolic Function of the Left Ventricle

119

Chapter 5 Evaluation of Systolic Function of the Left Ventricle

Evaluation of Systolic Function of the Left Ventricle

FIGURE 5.39. Composite illustration of myocardial performance index (MPI) calculated in three different patients. For each patient, the mitral inflow and left ventricular outflow track velocities are provided from which the time from mitral closure to mitral opening and ejection time are calculated. The upper panels were recorded in a normal individual with mild hypertensive cardiovascular disease and an ejection fraction of 63% who has a normal MPI of 0.34. The middle panels were recorded in a patient with a mild dilated cardiomyopathy, ejection fraction of 30%, and more severe diastolic dysfunction. Note the MPI of 0.69. The bottom panels were recorded in a patient with a severe dilated cardiomy opathy, pseudonor- mal mitral filling related to Grade 2 diastolic dysfunction, and ejection fraction of 22%. Note the calculated MPI of 1.0.

Determination of Left Ventricular d P /d t An additional parameter of le ventricular global function is le ventricular d P /d t which has long been a standard calculation using a high- delity micrometer catheter in the catheterization laboratory. d P /d t represents the rate of increase in pressure within the le ven- tricle. If con ned to early systole, during isovolumic contraction, it is a relatively load-independent measure of ventricular contractility. Using the spectral display of a mitral regurgitation jet, it is pos- sible to derive similar information regarding the rate of pressure development within the le ventricle. If this measurement is under- taken in early systole while the increasing ventricular pressure is less than the aortic pressure, it is relatively load independent. e method by which this is performed is to record the mitral regurgi- tation spectral pro le at a high sweep speed (typically 100 mm/s), as shown in Figures 5.40 and 5.41. Examination of the early velocity curve can then be used to derive instantaneous pressure measure- ments. To determine the d P /d t , one calculates the time di‡erence in milliseconds from the point at which the velocity is at 1 m/s and at 3 m/s. e time between these two points represents the time that it takes for a pressure change of 32 mm Hg to occur in the le ventricular cavity. d P /d t is then calculated as d P /d t = 32 mm Hg/ time (ms). Determination of d P /d t using this method has been val- idated against invasive hemodynamics. In addition to determining this parameter in early phases of systole, the negative d P /d t over the analogous pressure change (36 to 4 mm Hg) in diastole can also be calculated and provides information regarding diastolic function.

FIGURE 5.40. Schematic representation and example of calculating the left ventricu- lar d P/ d t from the continuous-wave Doppler mitral regurgitation spectral signal. Left: A continuous-wave spectral Doppler image recorded in a patient with severe left ventricular systolic dysfunction in which the online measurement of d P/ d t is noted to be 482 mm Hg/s. Right: The methodology for this determination, which includes recording continuous-wave Doppler imaging of mitral regurgitation at a high sweep speed (150 mm/s in this example) and defining points for which the mitral regurgitation velocity has reached 1 and 3 m/s, is depicted. This represents a 32 mm Hg/s pressure increase in the left ventricle into a low-compliance left atrium, thus making this a relatively load-independent measure of con- tractility. The time between the two points required to reach 1 and 3 m/s( ∆ t ) is then divided into the pressure difference (32 mm Hg) for calculation of d P/ d t.

[AQ3]

25

LWBK1670_C05_100-127.indd 119

5/15/18 11:27 A