Right-to-left shunt assessed by contrast transcranial Doppler sonography: new insights

Ultrasound contrast agents

Endoscopic ultrasound (EUS) plays an important role in imaging of the mediastinum and abdominal organs. Since the introduction of US contrast agents (UCA) for transabdominal US, attempts have been made to apply contrast-enhanced US techniques also to EUS. Since 2003, specific contrast-enhanced imaging was possible using EUS. Important studies have been published regarding contrast-enhanced EUS and the characterization of focal pancreatic lesions, lymph nodes, and subepithelial tumors. In this manuscript, we describe the relevant UCA, their application, and specific image acquisition as well as the principles of image tissue characterization using contrast-enhanced EUS. Safety issues, potential future developments, and EUS-specific issues are reviewed.

Adding blood to agitated saline significantly improves detection of right-to-left shunt by contrast-transcranial color-coded duplex sonography

Contrast-transcranial Doppler and contrast-transcranial color-coded duplex sonography (c-TCCD) have been reported to have high sensitivity in detecting patent foramen ovale as compared with transesophageal echocardiography. An international consensus meeting (Jauss and Zanette 2000) recommended that the contrast agent for right-to left-shunt (RLS) detection using contrast-transcranial Doppler be prepared by mixing 9 mL of isotonic saline solution and 1 mL of air. The aim of our study was to determine whether adding blood to the contrast agent results in improved detection of RLS. We enrolled all consecutive patients admitted to our neurosonology laboratory for RLS diagnosis. For each patient, we performed c-TCCD both at rest and during the Valsalva maneuver using two different contrast agents: ANSs (1 mL of air mixed with 9 mL of normal saline) and ANSHBs (1 mL of air mixed with 8 mL of normal saline and 1 mL of the patient's blood). To classify RLS, we used a four-level visual categorization: (i) no occurrence of micro-embolic signals; (ii) grade I, 1-10 signals; (iii) grade II, >10 signals but no curtain; grade III, curtain pattern. We included 80 patients, 33 men and 47 women. RLS was detected in 18.8% at rest and in 35% during the Valsalva maneuver using ANSs, and in 31.3% and in 46.3% using ANSHBs, respectively (p < 0.0001). There was a statistically significant increase in the number of micro-embolic signals with the use of ANSHBs. The use of blood mixed with saline solution and air as a c-TCCD contrast agent produced an increase in positive tests and a higher grade of RLS compared with normal saline and air alone, either with or without the Valsalva maneuver.

[Detection of micro-embolic signals: a review of the literature]

BACKGROUND

The detection of micro-embolic signals (MES), by transcranial Doppler sonography might be useful for risk stratification in patients with symptomatic and asymptomatic carotid or cerebral artery stenosis, dissections, aortic atheroma, interventional procedures, and right to left cardiac shunts.

AIM

Review of the technique and clinical situations of MES detection.

METHODS

PubMed search from 1990 to 2012.

RESULTS

MES were found in 0,19, 48% versus 0,3, and 12% of patients with symptomatic and asymptomatic inferior than 30, 30 to 69, and 70 to 99% carotid stenosis, respectively. MES were related to the risk of recurrent stroke or transient ischemic attack (TIA). In the ACES study, the absolute annual risk of stroke or TIA after 2 years was 7% with vs 3% without MES. In patients with intracranial stenosis, the risk of stroke recurrence was 48% with vs 7% without MES at 13.6 months follow-up. MES were reported in 25% of the symptomatic versus none of the asymptomatic patients with intracranial stenosis.

CONCLUSION

Detection of MES is feasible and reproducible for multicenter studies, using rigourous methodology and long lasting recordings. It may contribute to risk stratification, especially in patients with extra- or intracranial stenosis.

Unilateral versus bilateral middle cerebral artery detection of right-to-left shunt by power M-mode transcranial doppler

BACKGROUND AND PURPOSE

Comparison was performed between unilateral and bilateral power M-mode transcranial Doppler to detect right-to-left circulatory shunt (RLS).

METHODS

Recorded Doppler data from 87 patients with confirmed RLS referred for transcatheter closure of patent foramen ovale were reanalyzed for embolic tracks (ET) counted from left and right temporal bone windows during bubble study. Unilateral counts were obtained by multiplying each side by 2; bilateral counts were obtained by summing left and right ET. Both unilateral and bilateral ET were converted to a 6-point logarithmic grade. Sex and age group subanalyses were performed.

RESULTS

At rest, significantly more ET were detected with bilateral versus unilateral detection (P= .01), but not following Valsalva (P= .13). Unilateral and bilateral detection were equally able to detect large RLS (grades IV or V) following Valsalva (P= 1.00). For the group aged > or =55 years, the right-hand side yielded greater ET than the left-hand side (mean difference 9%+/- 37; 95% confidence interval -3 to 21%) at rest (P= .01), but not following Valsalva (mean difference 1%+/- 25; 95% confidence interval -7 to 9%, P= .10).

CONCLUSIONS

Unilateral detection of ET by power M-mode transcranial Doppler is equivalent to bilateral detection to assess RLS.

Quantification of Microspheres Appearance in Brain Vessels

Background and Purpose— Characteristics of ultrasound-activated gaseous microspheres (μS) reflective of their size and quantities are needed for future dose-escalation and drug delivery trials.

Methods— A double-blind, interobserver-validated analysis of multi-gate power-motion Doppler μS traces included large (>8μ) μS from agitated saline injections in the right-to-left shunt (RLS) positive stroke patients and small (<5μ) μS from acute patients without shunts receiving thrombolysis and perflutren-lipid μS.

Results— In 101 μS traces from 50 RLS-positive and 10 thrombolysis+μS treated patients, a large μS passage had median maximum duration 30.8 ms (interquartile range [IQR] 22.0ms), multi-gate travel time (MGTT) 58.6±19.3 ms versus small μS: duration 8.3ms (IQR 4.3ms), MGTT 43.2±13.9ms, P <0.001. Small μS had higher embolus-to-blood ratio (EBR): 17.5 (IQR 9.3) versus 7.5 (IQR 4), P <0.001. Receiver-operating curve areas were: duration 0.989 (95% CI 0.968 to 1.000), MGTT 0.766 (0.672 to 0.859), and EBR (Embolus-to-Blood Ratio) 0.927 (0.871 to 0.982), P <0.001. A 15.1-ms duration discriminated size ranges with 98% to 99% accuracy. On average, 130 sequential large (range 51 to 260) and 500 (265–588) small μS can produce continuous flow enhancement for 4 seconds. Small μS velocities on m-mode in obstructed vessels (39.8±11.3 cm/s) were similar to large μS in patent vessels (40.8±11.5 cm/s; P =0.719) and higher than surrounding red blood cell velocities (28.8±13.8 cm/s, P <0.001).

Conclusions— With normal or reduced flow, activated μS passage duration through a small power motion Doppler gate can quantify the dose of delivered μS. Ultrasound can determine a minimum number of μS needed to achieve constant flow enhancement and targeted drug delivery. Propagation speed of μS smaller than red blood cells may reflect plasma flow velocities around acute occlusions.

[Detection of cardial and extracardial right-to-left shunts in young stroke patients]

BACKGROUND

The aim of this study was to determine the frequency of extracardial and particularly pulmonal right-to-left-shunts (RLS) in patients with acute cerebral ischemia of unknown origin.

PATIENTS AND METHODS

We investigated 52 patients under 60 years of age with cerebral ischemic stroke of unknown origin using transesophageal echocardiography (TEE) with special attention to the late phase of ultrasound contrast medium in the left atrium. Additionally we performed contrast transcranial doppler sonography (TCD).

RESULTS

In the TEE, 25 patients (48%) showed cardial RLS. In seven patients with normal TEE (13.5%) we found evidence of RLS with contrast TCD (spontaneous RLS n=4, RLS after valsalva n=3). In none of these seven patients did we find late-phase contrast in the left atrium.

CONCLUSION

The constellation of RLS detection in contrast TCD but not in TEE was frequently found. Particularly in spontaneous RLS, this constellation raises the suspicion of a pulmonary shunt. However our extended TEE protocol did not give additional evidence for a pulmonary location of the shunt.

In-hospital onset ischemic stroke may be associated with atrial fibrillation and right-to-left shunt

BACKGROUND AND PURPOSE

Ischemic stroke during hospitalization can occasionally be found, but the mechanisms and causes underlying stroke have not been investigated in detail. The present study aimed to identify differences in stroke etiology between in-hospital and out-of-hospital onset.

METHODS

Subjects comprised 357 consecutive patients (221 men, 136 women) with ischemic stroke prospectively enrolled within 24 h of onset. Contrast saline transcranial Doppler ultrasonography (c-TCD) or transesophageal echocardiography (TEE) was performed in all participants to identify right-to-left shunts (RLS). Patients were divided into 2 groups: in-hospital onset (IHO group, n=49); and out-of-hospital onset (OHO group, n=308). Clinical characteristics were compared between groups.

RESULTS

Mean age was 71.5+/-12.3 years. Mean National Institute of Health stroke scale score was 6.9+/-7.2. RLS, atrial fibrillation (AF) and malignancy were more frequent in the IHO group than in the OHO group (39% vs. 20%, p=0.006; 45% vs. 16%, p<0.001; 18% vs. 4%, p<0.001, respectively). AF and/or RLS was more frequent in the IHO group (61%) than in the OHO group (30%, p<0.001).

CONCLUSION

Ischemic stroke with in-hospital onset may be associated with AF and RLS.

Ischaemic stroke with malignancy may often be caused by paradoxical embolism

BACKGROUND

Although ischaemic stroke with malignancy occasionally occurs, the mechanisms of stroke in such cases have not been investigated in detail.

OBJECTIVE

To examine the mechanisms of ischaemic stroke with malignancy, particularly in relation to right-to-left shunt (RLS).

METHODS

Consecutive patients with ischaemic stroke within 24 h of stroke onset were prospectively studied. Contrast saline transcranial Doppler examination was carried out for all patients, to investigate the presence of RLS. When patients with stroke had RLS, deep venous thrombosis (DVT) or pulmonary embolism was assessed to diagnose paradoxical brain embolism.

RESULTS

Participants comprised 184 consecutive patients (115 men and 69 women) with a mean (standard deviation (SD)) age of 73 (11.8) years and mean (SD) National Institutes of Health Stroke Scale (NIHSS) score of 8 (7.4). RLS was detected in 32 of 184 (18%) patients. Malignancy was present in 11 (5%) patients. RLS was more frequent in patients with malignancy than in patients without malignancy (55% v 15%, respectively; p = 0.001). All six patients with RLS and malignancy displayed DVT or pulmonary embolism with severe disability (modified Rankin Scale 4-5) before stroke onset.

CONCLUSION

Paradoxical brain embolism should be considered to be an important mechanism in patients with stroke and malignancy.