Detection of paradoxical cerebral echo contrast embolization by transcranial Doppler ultrasound.

Abstract

Contrast echocardiography has been shown to be a sensitive method for detecting patent foramen ovale in embolic stroke, implying paradoxical embolization. However, not all twodimensional echocardiographic studies are of diagnostic quality, and direct evidence for paradoxical cerebral embolization remains lacking. We addressed these problems by simultaneously using transcranial Doppler ultrasound and contrast echocardiography to compare relative sensitivity and concordance in the detection of right-to-left vascular shunting. Forty-six patients with stroke, transient neurologic defect, or question of atrial septal defect underwent study at rest and during Valsalva strain. Two-dimensional echocardiography detected shunting in 26% at rest and 15% during Valsalva strain, whereas transcranial Doppler study returned rates of 41% and 41%, respectively. Concordance was 82% and 75%, respectively. Discordant studies almost always had evidence of paradoxical contrast embolization by transcranial T he etiology of stroke in more than a third of young adult patients may remain uncertain even after extensive clinical study. 1 Paradoxical embolization via patent atrial foramen ovale has become suspect as a cause of embolic strokes or transient ischemic attacks. "3 Contrast echocardiography with patients at rest and during provocative maneuvers has been shown to be a sensitive method for noninvasively detecting patent foramen ovale in these patients.1 -3 However, not all two-dimensional echocardiographic studies are of diagnostic quality. Moreover, the technique only reveals the substrate for paradoxical embolization; the arterial delivery of emboli originating in the venous system at critical target organs is not demonstrated.The objective of contrast echocardiography in the evaluation of interatrial shunting is the detection of microcavitation gas bubbles entering left heart chambers after intravenous injection. As an alternative to ultrasonic imaging, Doppler ultrasound has served as a sensitive detector of blood-borne gas bubbles in From the University of Oklahoma Health Sciences Center, Cardiology Section, Oklahoma City, Okla.Presented in part at the 61st Scientific Sessions of the American Heart Association.Address for correspondence: Steve M. Teague, MD, MetroHealth Medical Center, 3395 Scranton Road, Cleveland, OH 44109.Received August 14, 1990; accepted February 21, 1991. decompression sickness by demonstrating air bubbles in the pulmonary artery. 4 -7 Specially designed transcranial Doppler devices have been used to detect micro air emboli in the middle cerebral artery during surgery. -9The purpose of this study was to use transcranial Doppler ultrasound as a detector of gas bubbles in the middle cerebral artery simultaneously with two-dimensional apical echocardiography as a detector of bubbles in the left atrium and ventricle so as to compare relative sensitivity and demonstrate concordance in the detection of right-to-left vascular shunting. Subjects and MethodsWe studied 46 consecutive patients referred for contr...

A comparison of transesophageal echocardiography and transcranial Doppler sonography with contrast medium for detection of patent foramen ovale.

“…The time limit was chosen from our data to ensure high sensitivity and specificity and was longer than in other studies. Furthermore, the duration between injection and observation of bubbles appearing in the right atrium was longer than in other studies (5.2±1.2 seconds compared with 2.6±0.4 seconds during the Valsalva maneuver 6 ). The latencies registered in the right MCA were also longer than in other studies (mean of 11.5±3.5 seconds compared with 4.6±2.5 seconds during the Valsalva maneuver 6 ).…”

“…Furthermore, the duration between injection and observation of bubbles appearing in the right atrium was longer than in other studies (5.2±1.2 seconds compared with 2.6±0.4 seconds during the Valsalva maneuver 6 ). The latencies registered in the right MCA were also longer than in other studies (mean of 11.5±3.5 seconds compared with 4.6±2.5 seconds during the Valsalva maneuver 6 ). This may be due to the prolonged circulation time of galactose microparticles compared with air bubbles or gelatine.…”

“…Lower concordance was observed in studies using transthoracic echocardiography instead of TEE. 6 Discordant findings in our study in one patient were due to prolonged circulation time and delayed appearance of bubbles at the MCA. Detection of PFO with TCD is compromised in patients with chronic cardiac failure.…”

“…Therefore, a simpler method for detection of PFO with transcranial Doppler sonography (TCD), which may serve as a screening test, was introduced by Teague and Sharma. 6 Although the described method is simple to use, there are some unsolved problems: (1) How reliable is TCD with contrast medium in detection of PFO, and how do the sensitivity and specificity compare with those of Received December 17, 1993; final revision received March 3, 1994; accepted March 3, 1994.…”

Contrast Transcranial Doppler Ultrasound in the Detection of Right-to-Left Shunts

“…In case of a RLS, the contrast agent enters the arterial circulation and produces microembolic signals (MES) during the TCD recording, thus mimicking the pathway of paradoxical cerebral emboli. 9,10 There is no doubt that the performance of a VM increases the sensitivity of contrast TCD. Recent data suggest that the combination of the results of 2 contrast TCD tests with a provocation maneuver considerably increases the sensitivity of the method.…”