Two-dimensional guided M-mode color tissue Doppler echocardiography in artificial preexcitation models

Aortic atheroma and adverse cerebral outcome: risk, diagnosis, and management options

Aortic atheromatous disease is a common finding in the patient presenting for cardiac surgery. Adverse neurologic outcome has been closely linked to the extent of aortic atherosclerosis. In order to optimize perioperative outcomes, the location and severity of disease needs accurate characterization using multimodal techniques. Although various preoperative radiographic techniques have variably identified patients with significant atheroma, intraoperative echocardiographic imaging has proven most useful in localizing and characterizing the degree of aortic atheroma. Epiaortic assessment of the ascending aorta has been utilized in guiding surgical modifications and interventions aimed at reducing the risk of neurologic injury. Although no particular technique has been definitely studied, avoidance of the identifiable atheromatous aortic region has been a main feature of the various modifications employed to optimize neurologic outcome after cardiac surgery.

Asynchrony of ventricular activation affects magnitude and timing of fiber stretch in late-activated regions of the canine heart

Abnormal electrical activation of the left ventricle results in mechanical dyssynchrony, which is in part characterized by early stretch of late-activated myofibers. To describe the pattern of deformation during "prestretch" and gain insight into its causes and sequelae, we implanted midwall and transmural arrays of radiopaque markers into the left ventricular anterolateral wall of open-chest, isoflurane-anesthetized, adult mongrel dogs. Biplane cineradiography (125 Hz) was used to determine the time course of two- and three-dimensional strains while pacing from a remote, posterior wall site. Strain maps were generated as a function of time. Electrical activation was assessed with bipolar electrodes. Posterior wall pacing generated prestretch at the measurement site, which peaked 44 ms after local electrical activation. Overall magnitudes and transmural gradients of strain were reduced when compared with passive inflation. Fiber stretch was larger at aortic valve opening compared with end diastole (P < 0.05). Fiber stretch at aortic valve opening was weakly but significantly correlated with local activation time (r(2) = 0.319, P < 0.001). With a short atrioventricular delay, fiber lengths were not significantly different at the time of aortic valve opening during ventricular pacing compared with atrial pacing. However, ejection strain did significantly increase (P < 0.05). We conclude that the majority of fiber stretch occurs after local electrical activation and mitral valve closure and is different from passive inflation. The increased shortening of these regions appears to be because of a reduced afterload rather than an effect of length-dependent activation in this preparation.

A simple and accurate method to identify early ventricular contraction sites in Wolff-Parkinson-White syndrome using high frame-rate tissue-velocity imaging

The high frame-rate tissue-velocity imaging method may be superior to the conventional M-mode method in accurately localizing accessory pathways without consuming large amounts of time.

Tissue Doppler imaging for the assessment of left ventricular systolic and diastolic functions

Doppler tissue imaging is a technique that allows recording of the low Doppler shift frequencies of high energy generated by the ventricular walls motion that are purposely filtered out in standard Doppler blood flow studies. Doppler tissue imaging can be performed with the use of pulsed Doppler, color two-dimensional Doppler, and color M-mode Doppler. Pulsed Doppler tissue imaging offers a high temporal resolution and therefore can be appropriately used for analysis of temporal relation between myocardium systolic and diastolic velocity waves. Color two-dimensional Doppler provides a good spatial resolution that permits differentiation of the velocity profiles between subendocardial and subepicardial layers but is limited by its poor temporal resolution. M-mode color-coded tissue imaging is characterized by a high spatiotemporal resolution, but sampling is only performed on a single line. Both two-dimensional and M-mode color-coded tissue imaging require specific modification of the current ultrasound machines. The present article reviews how Doppler tissue imaging may contribute to the noninvasive assessment of systolic and diastolic myocardial functions.

Use of high-frame rate imaging and doppler tissue echocardiography in the diagnosis of fetal ventricular tachycardia

Ventricular tachycardia has rarely been diagnosed in the fetus. We describe a 31-week-old fetus with ventricular tachycardia and severely depressed ventricular function. M-mode and 2-dimensional Doppler tissue echocardiography were used in this study to assess the nature of the arrhythmia. The complete atrioventricular dissociation inherent to the diagnosis of ventricular tachycardia was particularly easy to detect with M-mode Doppler tissue echocardiography. Moreover, the onset and the pattern of propagation of the ventricular arrhythmia could be easily identified with 2-dimensional Doppler tissue echocardiography. Doppler tissue echocardiography facilitates the diagnosis of ventricular tachycardia and adds new information that is not available by other techniques.