Final Feigenbaum’s Echocardiography DIGITAL

Chapter 5 Evaluation of Systolic Function of the Left Ventricle

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Chapter 5 Evaluation of Systolic Function of the Left Ventricle

Table 5.7

ISCHEMIC VERSUS NONISCHEMIC WALL MOTION ABNORMALITIES

Abnormality

Location

Onset

Duration Multiphasic

Thickening

Left bundle branch block

Anterior septum

Early systole

Blunted

Paced rhythm

Distal septum

Early systole

Multiphasic

Blunted

Postoperative motion

Whole heart

Early systole

Whole cycle

Preserved

Very brief ( < 50 ms)

Ventricular pre-excitation (WPW)

Variable

Presystolic

Preserved

Constriction

Septum/posterior wall

Diastole

Last 3/4

Preserved

Distal > proximal

Ischemia/infarction

Early systole

All systole

Absent

time of cardiovascular stress. Perhaps the most valuable observation when attempting to separate le bundle branch block from ischemia is myocardial thickening. With le bundle branch block, myocar- dial thickening is typically preserved as is initial early ventricular contraction. By using M-mode echocardiography, or con‰ning wall motion analysis to the ‰rst half or third of systole, one can oen appreciate that systolic thickening is preserved. Additional valuable clues include the fact that ischemia involving the proximal le ante- rior descending coronary artery, which would be required to result in a proximal septal abnormality, will usually result in distal abnor- malities as well. In most instances, le bundle branch block does not result in abnormalities in the apex or distal anterior wall. is can be a valuable clue to the etiology of the wall motion abnormality. Right bundle branch block does not alter the initial sequence of activation of the le ventricle and, unless associated with intrinsic disease of the right heart, will not be associated with appreciable wall motion abnormalities. Premature Ventricular Contractions A premature ventricular contraction (PVC) results in segmental wall motion abnormality for the beat in which the le ventricle is activated by the PVC. e most extreme example is a PVC arising in the lateral wall that is temporally and anatomically as remote from normal contraction as possible. In this instance, there will be immediate myocardial thickening and contraction of the lateral wall, occasionally resulting in dyskinesis of the relaxed septum, fol- lowed by asynchronous contraction of the le ventricle. High tem- poral resolution, two-dimensional echocardiography can be used to identify the site of earliest mechanical activation. In practice, a skilled echocardiographer should rarely be confused by wall motion abnormalities arising from PVCs. Scrutiny of the accompanying electrocardiogram is obviously informative, and the nature of the wall motion abnormality is frequently inconsistent with the known distribution of coronary or other forms of commonly encoun- tered heart disease. Appreciation of the secondary eects of PVC is important. Aer a PVC, there is a “compensatory pause” and the subsequent le ventricular contraction is normally hyperdynamic (Fig. 5.47). It is important to appreciate this phenomenon so as not to then compare normal sinus beats and assume that the ventricle is hypokinetic. On occasion, an echocardiogram is performed in a patient with persistent bigeminy or trigeminy. is can result in confusion because each PVC will be accompanied by abnormal wall motion and frequently hypokinesis of the remaining walls, related to under‰lling during the shortened preceding diastole. e wall motion of the beat, following the compensator pause, will then be hyperdynamic. e third beat, representing normal contraction, provides the only assessment of true normal ventricular contrac- tility. is issue may be especially problematic when viewing sin- gle digital cardiac cycle cine loops, where the relationship of systole function to rhythm may not be obvious. e augmented post-PVC beat will also be associated with increased •ow velocity and TVI in the le ventricular out•ow tract (Fig. 5.48).

septum. On two-dimensional echocardiography, it may be noted as a “bounce” in the septum. In other instances, there will be a dramatic “paradoxical” motion of the ventricular septum. is range in activation abnormality is due to the variation in the degree to which le bundle branch block has delayed activation, the pres- ence or absence of more distal His-Purkinje system disease, and the impact of concurrent disease that may either mask or exaggerate the bundle branch block pattern. Another characteristic of the le bun- dle branch block pattern is that the magnitude of the abnormality is oen increased during pharmacologic stress with dobutamine. It is less oen noted to be augmented during the physiologic stress of exercise. In a subset of patients, the mechanical dyssynchrony results in deterioration of ventricular function and a cardiomyopathic syn- drome ensues. is can be reversed with biventricular pacing. A common scenario is for there to be a le bundle branch block in a patient for whom coronary artery disease is a diagnostic con- sideration. Separation of the wall motion abnormality due to the bundle branch block from the eects of coronary disease involving the le anterior descending coronary artery can be problematic, especially for the less experienced echocardiographer. Table 5.7 out- lines a number of features that can help separate le bundle branch block and other nonischemic abnormalities from an ischemic wall motion abnormality. It should be emphasized that none of these features is absolute, and even experienced echocardiographers may have di…culty in separating a le bundle branch block wall motion abnormality from an ischemic wall motion abnormality. It should also be recognized that le bundle branch block may coexist with resting ischemia, myocardial infarction, or inducible ischemia at the

Evaluation of Systolic Function of the Left Ventricle

FIGURE 5.46. M-mode echocardiogram recorded in a patient with a left bundle branch block. In the M-mode note the abrupt downward motion of the ventricular septum shortly after the onset of the QRS ( arrows ) and the relatively neutral position of the ventricular septum throughout the remainder of systole. In the accompanying parasternal long-axis two-dimensional image note the quivering of the septum in real time consistent with the left bundle branch block abnormality.

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