Temporal sequence of right and left atrial contractions during spontaneous sinus rhythm and paced left atrial rhythm

Patent foramen ovale and transcranial Doppler. Comparison of different procedures

BACKGROUND AND PURPOSE

The capability of transcranial Doppler sonography (TCD) to detect a patent foramen ovale (PFO) has been established. However, which provocative maneuver and what timing of contrast injection are most effective to induce a right-to-left shunt has not yet been determined.

METHODS

We selected 38 cerebrovascular patients (21 men, 17 women) with positive contrast study for PFO on transesophageal echocardiography. Patients underwent a TCD with bilateral monitoring of the middle cerebral arteries (MCAs) and injection of a contrast solution. The injection was repeated (1) during normal breathing (basal conditions); (2) before Valsalva maneuver (VM); (3) during VM; (4) immediately after VM; and (5) during cough. The latency time and the total number of microbubbles for each side were recorded.

RESULTS

TCD found positive results for PFO in 30 patients. Twenty were positive even during basal conditions. The number of positive cases varied according to the timing of the VM in relation to the contrast injection: 28, 25, and 27 cases were positive when the injection was performed before, during, and after VM, respectively, while 26 were positive during cough. There were significant differences in the number of microbubbles in the MCAs between the procedures (P < .001, ANOVA): the highest number was detected in the injection before VM and the lowest number during basal conditions (P < .001, Wilcoxon's test with Bonferroni's correction). The latency time was significantly shorter when the injection followed VM.

CONCLUSIONS

The injection performed before VM appeared to be the most effective TCD procedure in determining the transit of microbubbles through a PFO and subsequently in the MCAs.

Paradoxical embolism as a cause of ischemic stroke of uncertain etiology. A transcranial Doppler sonographic study

BACKGROUND AND PURPOSE

This study was designed to test the hypothesis that paradoxical embolization would be a cause of embolic strokes and transient ischemic attacks in patients with stroke of uncertain etiology in all age groups.

METHODS

Thirty patients who had stroke of uncertain etiology were studied. They were divided into the following three groups: 13 patients with sudden onset (group A), 11 patients with subacute onset (group B), and 6 asymptomatic stroke patients (group C). Eleven patients with stroke of obvious etiology (group D) and 11 normal healthy volunteers (group E) were also studied as controls. In all patients transcranial Doppler sonography and contrast echocardiography were recorded simultaneously after intravenous injection of the contrast medium. Findings of positive patient foramen ovale in contrast echocardiography or "chirp" sounds in transcranial Doppler sonography were defined as positive for paradoxical contrast embolization. Radioisotope phlebography of the lower extremities and pulmonary scintigraphy, using technetium-99 macroaggregated albumin, were performed in all 17 patients who had positive findings of paradoxical contrast embolization and in 12 patients whose findings were negative.

RESULTS

Positive findings of paradoxical contrast embolization were found in 17 subjects by transcranial Doppler sonography but in only 8 on contrast echocardiography. These positive findings were detected more frequently in group A (77%) than in groups B, D, and E (9%, 18%, and 9%, respectively) (P < .05). In group C, 4 of 6 patients (67%) had positive findings. There were positive findings on both phlebography and pulmonary scintigraphy only in 6 group A patients, with positive findings of paradoxical contrast embolization.

CONCLUSIONS

Transcranial Doppler sonography is a sensitive detector of right-to-left shunts. Paradoxical cerebral embolization might be frequent in patients with stroke of unknown etiology, especially when the stroke is of sudden onset.

Prevalence of patent foramen ovale in patients with stroke

The cause of ischemic stroke in younger adults is undefined in as many as 35 percent of patients. We studied the prevalence of patent foramen ovale as detected by contrast echocardiography in a population of 60 adults under 55 years old with ischemic stroke and a normal cardiac examination. We compared the results with those in a control group of 100 patients. The prevalence of patent foramen ovale was significantly higher in the patients with stroke (40 percent) than in the control group (10 percent, P less than 0.001). Among the patients with stroke, the prevalence of patent foramen ovale was 21 percent in 19 patients with an identifiable cause of their stroke, 40 percent in 15 patients with no identifiable cause but a risk factor for stroke, such as mitral valve prolapse, migraine, or use of contraceptive agents, and 54 percent in 26 patients with no identifiable cause (P less than 0.10). These results suggest that because of the high prevalence of clinically latent venous thrombosis, paradoxical embolism through a patent foramen ovale may be responsible for stroke more often than is usually suspected.

Repetitive paroxysmal tachycardia originating in the left atrium

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