Contrast M-Mode Power Doppler Ultrasound in the Detection of Right-to-Left Shunts: Utility of Submandibular Internal Carotid Artery Recording

Right-to-left shunt detection using transforaminal insonation of the basilar artery

BACKGROUND AND PURPOSE

Investigation for patent foramen ovale (PFO) is warranted in patients with cryptogenic stroke (CS), as PFO closure is recommended in select CS patients for secondary stroke prevention. Transcranial Doppler (TCD) is noninvasive and has high sensitivity for PFO screening. However, 10% of the population has insufficient temporal bone windows to perform standard TCD monitoring of the middle cerebral arteries (MCAs). Prior reports showed similar diagnostic accuracy between the basilar artery and MCAs insonation. Our objective was to assess the accuracy of transforaminal insonation of the basilar artery (TIBA) in diagnosis of right-to-left shunt (RLS) in patients with inadequate temporal windows.

METHODS

We performed a retrospective, single-center, observational study of TIBA in patients with CS and inadequate temporal windows. We compared the PFO screening accuracy using TIBA versus echocardiogram, either transthoracic (TTE) or transesophageal echocardiogram (TEE).

RESULTS

Sixteen females and four males were included (mean age 63.2). All patients underwent TTE, 10 (50%) underwent gold-standard TEE. Nine patients had positive PFO with both TCD and echocardiogram. Two patients with negative echocardiogram had TCD-positive shunt. Three patients had PFO present on echocardiogram, whereas TCD was negative. Six patients had absent shunt with both TCD and echocardiogram. The sensitivity and specificity of TIBA for RLS detection were 75%, positive predictive value 82%, and negative predictive value 67%.

CONCLUSION

PFO screening accuracy using TIBA was 75%. Prospective evaluation of CS patients with TIBA and comparison to the gold-standard TEE should be performed to further guide clinical practice.

Comparison of Vertebral Artery and Middle Cerebral Artery Monitoring for Right-to-left Shunt Detection by Contrast-enhanced Transcranial Doppler

Contrast-enhanced transcranial Doppler (c-TCD) is a reliable and reproducible method for right-to-left shunt (RLS) detection, with high sensitivity. Monitoring the middle cerebral artery (MCA) is an optimal choice, yet for patients with insufficient temporal bone windows or severe stenosis of carotid arteries, an alternative should be established. The aim of the present study was to further establish whether c-TCD with vertebral artery (VA) monitoring is as effective as MCA monitoring for RLS detection. We evaluated 194 subjects for RLS detection with VA and MCA monitoring simultaneously. There was no significant difference between the positive rates of VA and MCA monitoring for RLS detection. c-TCD with VA monitoring could be an alternative for RLS detection, with high sensitivity and specificity both at rest and during the Valsalva manoeuvre.

Detection of Right-to-Left Cardiac Shunt in the Absence of Transcranial Acoustic Bone

PURPOSE

Paradoxical thrombotic embolism via right-to-left cardiac shunt (RLS) is a risk factor of cryptogenic ischemic stroke. Transtemporal Doppler (TTD) is a valid method used in the detection of patent foramen ovale (PFO). Temporal acoustic bone windows are missing with increasing age and in some younger subjects. We studied prospectively whether Doppler ultrasound of the cervical arteries (submandibular internal carotid artery [ICA] and vertebral artery [VA]) is an alternative, when compared to TTD, in the detection and quantification of PFO.

MATERIAL AND METHODS

A total of 94 patients with sufficient temporal bone windows suffering from recent ischemic stroke underwent TTD and ICA (n = 51) or TTD and VA (n = 43). After injection of microbubbles, the numbers of artificial high-intensity signals (HITS) were recorded at rest and after Valsalva maneuver.

RESULTS

For 47 patients in the ICA group, an RLS was found at rest in 23 patients and after Valsalva in 28 patients. At rest, sensitivity was 100%, specificity 96%, positive predictive value (ppv) 95.6%, and negative predictive value (npv) 100%. After Valsalva, sensitivity was 100%, specificity 95%, ppv 96.4%, npv 100%. For 43 patients in the VA group an RLS was found at rest in 14 patients and after Valsalva in 19 patients. At rest, sensitivity was 71.4%, specificity 100%, ppv 100%, and npv 87.8%. After Valsalva, 94.4%, 96%, 94.4%, and 96%, respectively. Pearson's correlations of the number of HITS between TTD and ICA and between TTD and VA were highly significant.

CONCLUSIONS

When transcranial acoustic bone windows are missing, Doppler ultrasound of the cervical submandibular ICA and VAs are valid screening methods to detect RLS due to a PFO.

The carotid artery as an alternative site to the middle cerebral artery for reproducible estimates of autoregulation index

Temporal insonation is not always possible for the middle cerebral artery (MCA) for blood flow velocity (BFV) measurements, to estimate cerebral autoregulation. We compared BFV and cerebral autoregulation estimates from the common-carotid (CCA) and internal-carotid arteries (ICA) with the MCA. BFV was measured at the CCA, ICA and MCA, synchronously with blood pressure, heart rate and end-tidal CO2 and was recorded onto a data acquisition system. The autoregulation index (ARI) estimated using the Tiecks model. Eleven healthy volunteers (7 women, 33 ± 9 years old) were recruited. BFVs in the MCA, CCA and ICA were 60.3 ± 8.9, 64.4 ± 6.5 and 69.2 ± 4.8 cm/s, respectively. ARI estimates were not significantly different (5.6 ± 0.8, 6.0 ± 1.1 and 5.9 ± 0.5, respectively). Good reproducibility over repeated measurements was evidenced by low coefficient of variation of standard error of measurement for BFV and ARI. The CCA and ICA are alternatives to the MCA, where insonation is impossible, because of an absent trans-temporal window or where it cannot be tolerated, such as in patients with head injury.

Common carotid artery duplex for the bubble test to detect right-to-left shunt

We prospectively compared the bubble test with agitated saline for right-to-left shunt using transcranial Doppler (TCD) of the right middle cerebral artery and second harmonic imaging duplex of the right common carotid artery (CCA) in 100 consecutive patients. Microembolic signals (MES) were counted offline. MES were classified into 6 classes: absent (class 0), 1-10 MES (class 1), 11-20 MES (class 2), 21-30 MES (class 3), 31-50 MES (class 4) and >50 MES or "curtain effect" (class 5). For TCD, classes 2-5 combined (i.e., "large" shunts), the sensitivity of duplex with the Valsalva maneuver was 95.3%, the specificity was 100%, the positive predictive 100%, the negative predictive value 96.6% and accuracy 98.0%. Second harmonic imaging duplex of the CCA may substitute TCD for the bubble test when an adequate cranial bone window is not available. This technique may also greatly increase the number of facilities where the bubble test can be carried out. However, tests with few or no MES need to be confirmed by TCD or transesophageal echocardiography.

An Association of Migraine with Hereditary Haemorrhagic Telangiectasia Independently of Pulmonary Right-to-Left Shunts

Hereditary haemorrhagic telangiectasia (HHT) is a genetic disorder characterized by epistaxis, telangiectasia and visceral vascular manifestations. It is associated with migraine with aura due to pulmonary arteriovenous malformations (pAVMs). The aim of the study was to evaluate headache prevalence in 106 consecutive HHT patients (67 female, 39 male, age 53.5 ± 14.5 years) and age- and gender-matched controls. An extensive clinical work-up was performed and headache prevalence was determined. Lifetime prevalence of migraine was higher in HHT patients (39.6%) than in controls (19.8%) [ P < 0.001, χ2 = 12.17, odds ratio (OR) 3.0; 95% confidence interval 1.6 < OR < 5.7]. A positive association was confirmed between HHT patients with pAVMs and migraine with aura (38.5% vs. 10%). Furthermore, HHT patients without pAVMs had a higher prevalence of migraine without aura (11.5% vs. 26.3%; χ2 = 11.85; d.f. = 2; P = 0.003). We speculate that pathophysiological mechanisms, including dysfunction of the transforming growth factor-beta pathways and resulting vascular changes, contribute to the higher prevalence of migraine without aura in HHT patients without pAVMs.