Effect of body positioning during transcranial Doppler detection of right-to-left shunts

Prevalence of patent foramen ovale in the Greek population is high and impacts on the interpretation of the risk of paradoxical embolism (RoPE) score

Background:

The risk of paradoxical embolism (RoPE) score calculates the probability that patent foramen ovale (PFO) is causally related to stroke (PFO attributable fraction, PFOAF), based on PFO prevalence in patients with cryptogenic stroke (CS) compared with that in the general population. The latter has been estimated at 25%; however, PFO prevalence in nonselected populations varies widely.

Methods:

Since PFO prevalence in Greece remains unknown, we evaluated it and we calculated PFOAF stratified by RoPE score in a cohort of patients with CS ⩽55 years old. PFO was detected according to the international consensus transcranial Doppler (TCD) criteria in 124 healthy subjects (H), in 102 patients with CS, and in 56 patients with stroke of known cause (nonCS). Each subject underwent unilateral middle cerebral artery recording after infusion of agitated saline, at rest, and after a controlled Valsalva maneuver. We characterized PFO as large (>20 microbubbles or curtain), moderate (11–20), and small (⩽10).

Results:

PFO was detected in 42.7% of H, 49% of CS, and 25% of nonCS (p = 0.013). Large PFOs were numerically higher in CS [28.4% (29/102)] compared with H [19.3% (24/124); p = 0.1] and to nonCS [7.1% (4/56), p = 0.04]. The median RoPE score in patients with CS and PFO was seven. Even patients with very high RoPE score (9–10) had moderate PFOAF (57%). For any individual stratum up to RopE score 8, PFOAF was <33%.

Conclusions:

PFO prevalence in the Greek population is much higher than the widely accepted 25%. PFO may be the cause of stroke in one out of nine Greek patients with CS. Among Greek CS patients who harbor a PFO, the latter is causal in one out of five. The established RoPE score cutoff of ⩾7 for having a probable PFO-associated stroke may overestimate the probability in patients deriving from populations with high PFO prevalence.

Relevance of small right-to-left shunt in contrast-enhanced transcranial Doppler in young and middle-aged patients with cryptogenic stroke: a report of two cases and literature review

AIM

The clinical relevance of small right-to-left shunt (RLS) in young patients with cryptogenic stroke is unknown. We aimed to analyze and understand the relationship between cryptogenic stroke and small RLS by studying specific cases.

MATERIALS AND METHODS

Clinical data from two cases of small RLS-related cryptogenic stroke in young patients were collected prospectively and analyzed. We followed up the patients for >1 year after discharge.

RESULTS

Case 1. A 50-year-old man was admitted for slurred speech and right hemiplegia and was diagnosed with acute cerebral infarction. Contrast-enhanced transcranial Doppler (c-TCD) and contrast-enhanced transthoracic echocardiography (c-TTE) revealed a microbubble and 20-30 microbubbles per section, respectively, in the resting state. Three months later, he was readmitted for stroke recurrence. Transesophageal echocardiography (TEE) confirmed a patent foramen ovale (PFO), and he underwent transcatheter closure of the PFO. Case 2. A 48-year-old man was admitted for right hemiplegia with slurred speech. Brain magnetic resonance imaging showed acute cerebral infarction. c-TCD and contrast-enhanced TEE (c-TEE) revealed <10 microbubbles and approximately 20 microbubbles per section, respectively. These findings suggested a PFO. Two months later, he was readmitted for stroke recurrence. He underwent transcatheter closure of the PFO. Follow-up of cases 1 and 2 at >1 and >1.5 years after discharge, respectively, showed no stroke recurrence.

CONCLUSION

We suspected that a small RLS may cause cryptogenic stroke. A small RLS in c-TCD in stroke patients may not be actually small, and c-TEE/c-TTE may be valuable in finding larger RLSs.

Comparison of Different Methods of Valsalva Maneuver for Right-to-left Shunt Detection by Contrast-Enhanced Transcranial Doppler

We evaluated 298 patients for right-to-left shunt (RLS) detection by contrast-enhanced transcranial Doppler at rest state (RS), during the conventional Valsalva maneuver (CM), and during the modified Valsalva maneuver (BM: blowing into the connecting tube of a sphygmomanometer at 40 mm Hg for 10 s) in random order, and the degree of RLS along the time of the first microbubble occurrence was recorded. The positive rates were 21.8%, 36.9% and 47.3% for RS, CM and BM, respectively (p < 0.001). BM resulted in a significantly higher positive rate (p = 0.010), and there was a significant difference between the two different methods of VM in terms of the degree of RLS detection (p < 0.001). Further, the first microbubble occurred later during BM than CM (10.22 ± 3.77 s vs. 9.44 ± 4.36 s, p < 0.05). This modified maneuver is an alternative to the conventional one, especially for those who cannot perform the conventional maneuver adequately, but are highly suspected of having RLS.

Transcranial Doppler: Techniques and advanced applications: Part 2

Transcranial Doppler (TCD) is the only diagnostic tool that can provide continuous information about cerebral hemodynamics in real time and over extended periods. In the previous paper (Part 1), we have already presented the basic ultrasound physics pertaining to TCD, insonation methods, and various flow patterns. This article describes various advanced applications of TCD such as detection of right-to-left shunt, emboli monitoring, vasomotor reactivity (VMR), monitoring of vasospasm in subarachnoid hemorrhage (SAH), monitoring of intracranial pressure, its role in stoke prevention in sickle cell disease, and as a supplementary test for confirmation of brain death.

Body positions in the diagnosis of right-to-left shunt by contrast transcranial Doppler

Contrast transcranial Doppler (c-TCD) is sensitive in detecting right-to-left shunt (RLS). However, the methodology and ideal posture are controversial. Consecutive migraine patients were prospectively examined for RLS using c-TCD. Each patient was examined while at rest and subsequently with the Valsalva maneuver (VM) in three positions: supine, left lateral decubitus and right lateral decubitus. RLS was diagnosed with at least one microbubble detected at any position. RLS was highest in the left lateral decubitus position, both during rest and with VM. The left lateral decubitus position was associated with the highest total number of microbubbles and greater shunt grades. Patients who tested positive in the other two positions had the lowest index position failure rate during rest in the left lateral decubitus position. In some patients in whom RLS is detected at rest, it may not be detected (false negative) under VM. To ensure c-TCD's the sensitivity to RLS, testing in the left lateral decubitus position at rest and under VM is suggested; testing in other positions is necessary to avoid false negatives.

Effects of patient position on right-to-left shunt detection by contrast transcranial Doppler

Contrast-enhanced transcranial Doppler (c-TCD) was performed on 117 patients to detect a right-to-left shunt (RLS). Each patient was examined during normal breathing and after performing the Valsalva maneuver (VM) in three randomly ordered positions: supine, left lateral decubitus and sitting upright. When breathing normally, RLS-positive rates were 15.4%, 23.1% and 28.2% for supine, left lateral decubitus and upright sitting positions, respectively. After VM, the positive rates were 25.6%, 28.2% and 36.8%, respectively. For each position, the RLS-positive rates were higher after VM than normal breathing and higher for the left lateral decubitus and upright sitting positions compared with the supine position, irrespective of breathing. There were no significant differences between findings for the left lateral decubitus and upright sitting positions. No significant differences in shunt grades were found across all groups. The choice of position for patients undergoing c-TCD can improve its sensitivity for the diagnosis of RLS.

Leftward bulging of atrial septum is provoked by nitroglycerin and by sustained valsalva strain

BACKGROUND

The motion of the interatrial septum primum (septum) is dependent on the interatrial pressure relation, normally with slightly higher pressure in the left atrium and the septum bulging toward the right atrium. The aim of this study was to explore the physiologic mechanisms that reverse interatrial pressures and provoke leftward bulging of septum (LBA). The hypothesis was that both left ventricular unloading with nitroglycerin and sustained Valsalva strain would independently provoke LBA and that their combination would further intensify the effect.

METHODS

Prospectively collected transesophageal echocardiography recordings from 13 patients with obstructive sleep apnea were retrospectively analyzed for the presence or absence of LBA during resting respiration and during Valsalva strain. In each condition, LBA beats were counted at time points before and after nitroglycerin spray had been administered, which enabled a comparison of the independent effects and the combined effect of the nitroglycerin and the Valsalva maneuver. An LBA beat was defined as a heartbeat displaying any LBA during the cardiac cycle.

RESULTS

Nitroglycerin increased the proportion of LBA beats significantly during resting respiration, from 21 ± 27% to 54 ± 43% (P = .008). During Valsalva strain, the proportion increased with nitroglycerin spray from 48 ± 21% to 80 ± 17% (P = .001). After nitroglycerin administration, LBA occurred in at least three beats during strain in all Valsalva periods.

CONCLUSIONS

Unloading of the left ventricle by nitroglycerin administration and by sustained Valsalva strain independently provoked LBA. The combination of these two interventions further intensified the effect.

Micro-bubble transcranial Doppler ultrasound for exclusion of right-to-left circulatory shunts: why should we provide the service?

Micro-bubble transcranial Doppler ultrasound is a study used for the identification and quantification of a right-to-left circulatory shunt which can be implicated in stroke. It is an underused technique in many centres. Micro-bubble transcranial Doppler ultrasound is non-invasive, innocuous, quick and requires no fasting or sedation. Published literature also suggests almost perfect concordance with transoesophageal echocardiography and potentially greater sensitivity. We believe there is a great potential for neuroradiologists to provide this service as part of the diagnostic workup in patients with cryptogenic stroke.

Transcranial doppler: Technique and common findings (Part 1)

Transcranial Doppler (TCD) can be aptly called as the doctor’s stethoscope of the brain. Since its introduction in 1982, by Rune Aaslid, TCD has evolved as a diagnostic, monitoring, and therapeutic tool. During evaluation of patients with acute ischemic stroke, TCD combined with cervical duplex ultrasonography provides physiological information on the cerebral hemodynamics, which is often complementary to structural imaging. Currently, TCD is the only diagnostic tool that can provide real time information about cerebral hemodynamics and can detect embolization to the cerebral vessels. TCD is a noninvasive, cost-effective, and bedside tool for obtaining information regarding the collateral flow across various branches of the circle of Willis in patients with cerebrovascular disorders. Advanced applications of TCD help in the detection of right-to-left shunts, vasomotor reactivity, diagnosis, and monitoring of vasospasm in subarachnoid hemorrhage and as a supplementary test for confirmation of brain death. This article describes the basic ultrasound physics pertaining to TCD insonation methods, for detecting the flow in intracranial vessels in addition to the normal and abnormal spectral flow patterns.

Transcranial Doppler with bubble study as a method to detect extracardiac right-to-left shunts in patients with ischemic stroke

BACKGROUND AND PURPOSE

Paradoxical embolism through extracardiac right-to-left shunts (ECRLS) may represent an under-detected stroke mechanism. Stroke patients without evidence of cardiac right-to-left shunt (RLS) on echocardiogram may benefit from transcranial Doppler with bubble study (TCD-b) to aid in recognition of stroke etiology. This study assesses the usefulness of TCD-b in the stroke evaluation.

METHODS

Retrospective cohort study of consecutive patients undergoing TCD-b performed in our neurovascular laboratory from February 2005 to August 2009. Echocardiography results were reviewed in patients with positive TCD-b. Detailed medical record review was performed on patients with positive TCD-b and negative echocardiogram findings for RLS.

RESULTS

Of 502 patients undergoing TCD-b, 48.4% (n = 243) had a positive study suggesting the presence of RLS. Of these, 59.2% (n = 144) had an echocardiogram demonstrating a cardiac RLS, 26% (n = 63) had echocardiograms without evidence of cardiac RLS, and 14.8% (n = 36) had no echocardiogram. Data on the evaluation to determine source of potential shunting in patients with discrepant findings was available in 11(17.5%). Of these, 63.6% (7/11) had potential mechanisms for positive TCD-b: one pulmonary arteriovenous malformation (AVM), one arteriovenous fistula thrombus, one parietal AVM, and four had malignancy.

CONCLUSIONS

TCD-bubble studies may prove useful in uncovering treatable causes of stroke.

Association between the Amount of Right-to-Left Shunt and Infarct Patterns in Patients with Cryptogenic Embolic Stroke: A Transcranial Doppler Study

Background

Paradoxical embolism has been documented as a mechanism of cryptogenic embolic stroke. We investigated the frequency of right-to-left shunt in patients with cryptogenic embolic stroke and evaluated the factors associated with diffusion-weighted imaging (DWI) lesion pattern.

Methods

We analyzed data on 157 consecutive patients with acute ischemic stroke because of presumed cryptogenic embolism. Agitated saline transcranial Doppler study was conducted in all patients to detect right-to-left shunt. We evaluated the association of the amount (microemboli ≥20 vs. ≥20) and activity (spontaneous vs. after Valsalva maneuver only) of right-to-left shunt with diffusion-weighted imaging lesion patterns.

Results

Right-to-left shunt was observed in 96 (61·1%) patients. The multiplicity and distribution of diffusion-weighted imaging lesions did not differ depending on the amount and activity of right-to-left shunt. However, the size of diffusion-weighted imaging lesions differed depending on the amount of right-to-left shunt ( P = 0·019). Right-to-left shunt was more frequently observed in patients with small (<1 cm) infarcts than in those with a large infarct (66·7% vs. 45·9%), and most patients with a larger amount of right-to-left shunt were found to have small infarcts on diffusion-weighted imaging (80%). The clinical characteristics, including Framingham stroke risk strategy, did not differ between the groups.

Conclusions

Our results indicate that the amount of right-to-left shunt determines the Diffusion-weighted imaging lesion patterns and suggest that mechanisms of stroke other than paradoxical mechanism may play an important role in patients with large cryptogenic embolic stroke.

Two different days of transcranial Doppler examinations should be performed for detection of right-to-left shunt in acute stroke patients

BACKGROUND

We investigated how many contrast-transcranial Doppler (c-TCD) examinations should be performed on different days in patients with acute stroke.

METHODS

Consecutive acute stroke patients within 24 hours of onset were enrolled. Presence of RLS was examined using c-TCD examinations on days 1, 7, and 14. Each c-TCD examination used one test without Valsalva maneuver (VM) and three tests with VM. Patients were diagnosed with RLS when TCD detected ≥1 microembolic signal on ≥1 c-TCD examination on any of the days 1, 7, or 14.

RESULTS

One hundred seventy patients (105 men [62%]; median age, 74 [IQR, 66-81] years) were enrolled. RLS was diagnosed in 45 patients (26%). RLS was identified on day 1 in 30 patients (18%), on day 7 in 28 patients (16%), and on day 14 in 23 patients (14%; P = .143). Detection rate of RLS by combining day 1 and 7 examinations was significantly higher than that of day 1 alone (25% vs. 18%, P < .001). However, the rate did not increase when results of day 14 were added (25% vs. 26%, P = .250).

CONCLUSIONS

c-TCD examinations should be performed on at least two different days to assess the prevalence of RLS.

Intracardiac shunting and stroke in children: a systematic review

In adults, patent foramen ovale or other potential intracardiac shunts are established risk factors for stroke via paradoxical embolization. Stroke is less common in children and risk factors differ. The authors examined the literature on intracardiac shunting and stroke in children, identifying the methods employed, the prevalence of detectible intracardiac shunts, associated conditions, and treatments. PubMed searches with keywords related to intracardiac shunting and stroke in children identified articles of interest. Additional articles were identified via citations in these articles or in reviews. The authors found that studies of intracardiac shunting in children with stroke are limited. No controlled studies were identified. Detection methods vary and the prevalence of echocardiographically detectible intracardiac shunting appears lower than reported in adults and autopsy studies. Defining the role of intracardiac shunting in pediatric stroke will require controlled studies with unified detection methods in populations stratified by additional risk factors for paradoxical embolization. Optimal treatment is unclear.

Alternatives to transtemporal approach of transcranial Doppler for the detection of right-to-left cardiac shunt

BACKGROUND

Transcranial Doppler (TCD) is reliable and reproducible for the diagnosis of right-to-left cardiac shunts (RLS).

METHODS

Various factors limiting the performance and diagnostic methods of RLS by TCD are discussed.

RESULTS

In patients with insufficient temporal acoustic windows, TCD may still be reliably used to monitor the microembolic signals at various alternative sites. Diagnostic yield of TCD may be further improved and better quantitative assessment of the 'functional potential' of the RLS by optimizing the preparation of the 'air-saline-blood' contrast-mixture, injecting the mixture in controlled body positions and using power M-mode TCD.

CONCLUSIONS

TCD may be used reliably for the detection as well as the quantification of RLS even in patients with insufficient temporal acoustic windows.

Postural Dependency of Right to Left Shunt

Background and Purpose— Right to left shunt is involved in conditions in which postural changes may be pathogenically relevant. The aim of this work was to assess the frequency of posturally dependent right to left shunt.

Methods— In 109 consecutive right to left shunt-positive subjects (male/female=40/69, age 43±12 years), we assessed with contrast-enhanced transcranial Doppler the bubble load during normal breathing and after the Valsalva maneuver in both standing and recumbent position randomizing the order of testing.

Results— During normal breathing, the average bubble count was 11±20 in the recumbent and 26±60 in the standing position. After the Valsalva maneuver, it was 40±38 and 42±37, respectively. The increase of bubble load in standing position occurred in 42% of patients and was independent of the order of testing.

Conclusions— The amount of permanent right to left shunt is posture-dependent in 40% of patients. Testing in the sitting position may thus be warranted in doubtful or inconclusive results obtained with the subject in the horizontal position.