Short-term external counterpulsation augments cerebral blood flow and tissue oxygenation in chronic cerebrovascular occlusive disease.

BACKGROUND AND PURPOSE: External counterpulsation improves cerebral perfusion velocity in acute stroke and may stimulate collateral artery growth. However, whether (non-acute) at-risk patients with high-grade carotid artery disease may benefit from counterpulsation needs to be validated. METHODS: Twenty-eight patients (71 ± 6.5 years, five women) with asymptomatic unilateral chronic severe internal carotid artery stenosis (>70%) or occlusion were randomized to receive 20 min active counterpulsation followed by sham treatment or vice versa. Cerebral blood flow velocity (CBFV) (measured bilaterally by transcranial middle cerebral artery Doppler), tissue oxygenation index (TOI) (measured over the bilateral prefrontal cortex by near-infrared spectroscopy) and cerebral hemodynamic parameters, such as relative pulse slope index (RPSI), were monitored. RESULTS: Ipsilateral mean CBFV (ΔVmean +3.5 ± 1.2 cm/s) and tissue oxygenation (ΔTOI +2.86 ± 0.8) increased significantly during active counterpulsation compared to baseline, whilst the sham had little effect (ΔVmean +1.13 ± 1.1 cm/s; ΔTOI +1.25 ± 0.65). On contralateral sides, neither counterpulsation nor sham control had any effect on either parameter. During counterpulsation, early dynamic changes in ΔRPSI of the ipsilateral CBFV signal predicted improved tissue oxygenation during counterpulsation (odds ratio 1.179, 95% confidence interval 1.01-1.51), whilst baseline cerebrovascular reactivity to hypercapnia failed to show an association. CONCLUSIONS: In patients with high-grade carotid disease, ipsilateral cerebral oxygenation and blood flow velocity are increased by counterpulsation. This is a necessary condition for the stimulation of regenerative collateral artery growth and thus a therapeutic concept for the prevention of cerebral ischaemia. This study provides a rationale for further clinical investigations on the long-term effects of counterpulsation on cerebral hemodynamics and collateral growth.

Investigating the potential of pyrazine dioxide based-compounds as organic electrodes for batteries.

Understanding structure-property relationship in redox-active molecular species is of central importance in various fields, including many medicinal and chemical applications. The quest for performant organic electrodes in the context of energy storage calls for pioneering studies to develop new and possibly optimal materials. Beyond modifying the molecular design of the existing compounds through functionalization, expansion of the search enabling the advent of efficient new backbones can potentially lead to breakthroughs in this research area. The number of already identified families able to constitute negative organic electrodes is much lower than that of their positive counterparts, which calls for finding ways to bridge this gap. To expand the dataset of known predicted redox potentials and in view of reaching an educated guess about the abilities of some eventual new redox active electrodes, we examined the properties of pyrazine N,N'-dioxide (PZDO) and its fully methylated functionalized derivative (TeMePzDO). The aspects and mechanisms driving the various features characteristic of these compounds were unraveled through molecular and periodic DFT calculations combined with accurate electronic structure analysis. The predicted molecular redox/crystalline intercalation potentials lead to the classification of PZDO and TeMePzDO systems within the class of negative electrodes, with features that are significantly appealing compared to those of some existing systems with backbones suited for such kind of application.

Dynamic cerebral autoregulation associates with infarct size and outcome after ischemic stroke.

OBJECTIVES: Cerebral autoregulation is particularly challenged in acute ischemic stroke. We investigated (1) clinical and radiological factors related to dynamic cerebral autoregulation (DCA) in acute stroke and (2) the relationship between DCA and clinical outcome of stroke. METHODS: A total of 45 patients with middle cerebral artery (MCA) stroke were analyzed pooling two previous studies. DCA was measured by transcranial Doppler in both MCAs early (within 48 h from onset) and late (day 5-7) using low-frequency phase and correlation analysis (index Mx). Outcome was assessed by modified Rankin scale after a mean period of 4 months. RESULTS: Mx increased (i.e. autoregulation worsened) between the early and late measurement, more so on affected (P = 0.005) than on unaffected sides (P = 0.014). Poorer autoregulation as indicated by lower ipsilateral phase (early and late) and higher Mx (late measurement) were significantly related to larger infarction. More severe stroke was significantly related to poorer ipsilateral Mx and phase. Ipsilateral phase in the early (P = 0.019) and Mx in the late measurement (P =0..016) were related to poor clinical outcome according to univariate analysis. CONCLUSIONS: Impairment of DCA ipsilateral to acute ischemic stroke is associated with larger infarction. Dysautoregulation tends to worsen and spread to the contralateral side over the first days post-stroke and is associated with poor clinical outcome.

3D blood flow characteristics in the carotid artery bifurcation assessed by flow-sensitive 4D MRI at 3T.

To determine three-dimensional (3D) blood flow patterns in the carotid bifurcation, 10 healthy volunteers and nine patients with internal carotid artery (ICA) stenosis > or =50% were examined by flow-sensitive 4D MRI at 3T. Absolute and mean blood velocities, pulsatility index (PI), and resistance index (RI) were measured in the common carotid arteries (CCAs) by duplex sonography (DS) and compared with flow-sensitive 4D MRI. Furthermore, 3D MRI blood flow patterns in the carotid bifurcation of volunteers and patients before and after recanalization were graded by two independent readers. Blood flow velocities measured by MRI were 31-39% lower than in DS. However, PI and RI differed by only 13-16%. Rating of 3D flow characteristics in the ICA revealed consistent patterns for filling and helical flow in volunteers. In patients with ICA stenosis, 3D blood flow visualization was successfully employed to detect markedly altered filling and helical flow patterns (forward-moving spiral flow) in the ICA bulb and to evaluate the effect of revascularization, which restored filling and helical flow. Our results demonstrate the feasibility of flow-sensitive 4D MRI for the quantification and 3D visualization of physiological and pathological flow patterns in the carotid artery bifurcation.

[Imaging techniques for giant cell arteritis. Ultrasound and MRI]. / Bildgebung der Riesenzellarteriitis. Sonographie und MRT.

This article summarizes the examination technique, typical findings, interpretation and limitations of ultrasound diagnosis in patients with giant cell arteritis. Colour-coded sonography of the temporal artery has gained increasing attention. If experienced ultrasound examiners are available, diagnosis of giant cell arteritis in patients with a typical clinical constellation can be made based solely on sonographic findings, in particular by a hypoechogenic halo. The hitherto probably under-diagnosed large vessel variant of giant cell arteritis shows characteristic findings with a simple and quick ultrasound examination of the proximal arm arteries. High resolution MRI has been shown to be a promising technique for non-invasive imaging of giant cell arteritis. Mural inflammatory changes of the superficial temporal arteries can be depicted and the cranial involvement pattern can be readily assessed and in combination with MR angiography extracranial involvement can be determined within the same investigation. Aortitis is a feared complication of giant cell arteritis but can be detected and inflammatory stenoses of the aortic branch vessels can also be revealed. In the hands of an experienced operator ultrasonography can be regarded as the non-invasive imaging modality of first choice whereas MRI is more expensive and may not be as widely available. However, its imaging acquisition is standardized and is more observer-independent. Reading of the images is a routine task for a vascular radiologist and larger areas of the vasculature can be simultaneously assessed.

Angioplasty in asymptomatic carotid artery stenosis vs. endarterectomy compared to best medical treatment: One-year interim results of SPACE-2.

BACKGROUND: Treatment of individuals with asymptomatic carotid artery stenosis is still handled controversially. Recommendations for treatment of asymptomatic carotid stenosis with carotid endarterectomy (CEA) are based on trials having recruited patients more than 15 years ago. Registry data indicate that advances in best medical treatment (BMT) may lead to a markedly decreasing risk of stroke in asymptomatic carotid stenosis. The aim of the SPACE-2 trial (ISRCTN78592017) was to compare the stroke preventive effects of BMT alone with that of BMT in combination with CEA or carotid artery stenting (CAS), respectively, in patients with asymptomatic carotid artery stenosis of ≥70% European Carotid Surgery Trial (ECST) criteria. METHODS: SPACE-2 is a randomized, controlled, multicenter, open study. A major secondary endpoint was the cumulative rate of any stroke (ischemic or hemorrhagic) or death from any cause within 30 days plus an ipsilateral ischemic stroke within one year of follow-up. Safety was assessed as the rate of any stroke and death from any cause within 30 days after CEA or CAS. Protocol changes had to be implemented. The results on the one-year period after treatment are reported. FINDINGS: It was planned to enroll 3550 patients. Due to low recruitment, the enrollment of patients was stopped prematurely after randomization of 513 patients in 36 centers to CEA (n = 203), CAS (n = 197), or BMT (n = 113). The one-year rate of the major secondary endpoint did not significantly differ between groups (CEA 2.5%, CAS 3.0%, BMT 0.9%; p = 0.530) as well as rates of any stroke (CEA 3.9%, CAS 4.1%, BMT 0.9%; p = 0.256) and all-cause mortality (CEA 2.5%, CAS 1.0%, BMT 3.5%; p = 0.304). About half of all strokes occurred in the peri-interventional period. Higher albeit statistically non-significant rates of restenosis occurred in the stenting group (CEA 2.0% vs. CAS 5.6%; p = 0.068) without evidence of increased stroke rates. INTERPRETATION: The low sample size of this prematurely stopped trial of 513 patients implies that its power is not sufficient to show that CEA or CAS is superior to a modern medical therapy (BMT) in the primary prevention of ischemic stroke in patients with an asymptomatic carotid stenosis up to one year after treatment. Also, no evidence for differences in safety between CAS and CEA during the first year after treatment could be derived. Follow-up will be performed up to five years. Data may be used for pooled analysis with ongoing trials.

Reliability of aortic MRI at 3 Tesla in patients with acute cryptogenic stroke.

OBJECTIVES: To evaluate a new three dimensional (3D) MRI protocol for the reliable detection of aortic high risk plaques compared with transoesophageal echocardiography (TOE) and to test the reliability of additional MRI in stroke of undetermined aetiology. METHODS: 74 acute stroke patients were examined by both TOE and MRI at 3 Tesla with special regard to aortic high risk plaques (ie, > OR = 4 mm, superimposed thrombi). ECG synchronised pre- and post-contrast T1 weighted 3D imaging (spatial resolution approximately 1 mm3) covering the thoracic aorta was employed. In plaques > OR = 3 mm, additional two dimensional T2 imaging and time resolved (CINE) imaging sequences were performed. Aetiology of brain ischaemia was classified according to modified TOAST (Trial of Org 10172 in Acute Stroke Treatment) criteria. Aortic high risk embolic sources detected by MRI in patients with cryptogenic stroke were evaluated. RESULTS: Differences in maximum aortic wall thickness for TOE and MRI were not statistically significant for all aortic segments. The overall number of high risk plaques detected by MRI (n = 74) was substantially higher compared with TOE (n = 47). Most noticeably, MRI identified aortic high risk pathologies in 8/26 (30.8%) patients with cryptogenic stroke after standard diagnostics, including TOE (n = 2: dissection or thrombus; n = 6: plaques > OR = 4 mm). CONCLUSIONS: Our results demonstrate the feasibility of this 3D MRI protocol for the reliable detection of aortic high risk plaques in acute stroke patients. Because of improved visualisation of the aortic arch and the detection of additional embolic sources not seen by standard diagnostics, this novel technique may become a valuable tool for future patients with cryptogenic stroke.

Systemic diseases in non-inflammatory branch and central retinal artery occlusion--an overview of 416 patients.

BACKGROUND: To determine the frequency of essential cardiovascular risk factors in different vascular ocular diseases. - METHODS: We compiled cardiovascular risk factor findings (RFs) from 416 patients with non-inflammatory ocular vascular occlusions in a retrospective study: 134 patients with BRAO, 253 patients with CRAO, and 29 patients with hemi-CRAO. 274 (65.9 %) male and 142 (34.1 %) female patients were examined. Mean age of all patients was 66 years (range: 18-90). The right eye was involved in 221 (53.1 %), left eye in 193 (46.4 %), and both eyes in 2 patients (0.5 %). - RESULTS: Cardiovascular risk factors (RFs) were found in 243 patients. Three hundred and eight (308) out of 406 patients (75.9 %) presented with arterial hypertension. Hypertension was present in 96 patients with BRAO (73.8 %), in 197 patients with CRAO (79.8 %), and in 15 patients with hemi-CRAO (78.9 %). - RFs such as arterial hypertension, carotid artery diseases, diabetes mellitus, hyperlipidemia, hyperuricemia, and chronic smoking did not differ statistically between patients with BRAO, CRAO or hemi--CRAO. But visible emboli in retinal arteries were observed in patients with BRAO (47 %,), or hemi-CRAO (41.4 %), much more often than in patients with CRAO (11.1 %). - CONCLUSIONS: No statistical differences between the RFs of patients with BRAO, CRAO, or hemi-CRAO were noted. We maintain that every patient with retinal arterial obstruction should undergo extensive examination of essential RFs.

[Von Hippel-Lindau disease. Interdisciplinary patient care]. / Von-Hippel-Lindau-Erkrankung. Interdisziplinäre Patientenversorgung.

Von Hippel-Lindau disease is an important hereditary tumor syndrome with a clear option for effective treatment if diagnosed in time. Interdisciplinary cooperation is the key to successful management. Major components of the disease are retinal capillary hemangioblastomas, hemangioblastomas of cerebellum, brain stem and spine, renal clear cell carcinomas, pheochromocytomas, multiple pancreatic cysts and islet cell carcinomas, tumors of the endolymphatic sac of the inner ear, and cystadenomas of the epididymis and broad ligament. A well structured screening program should be performed at yearly intervals.

Dynamic cerebral autoregulation in acute ischemic stroke assessed from spontaneous blood pressure fluctuations.

BACKGROUND AND PURPOSE: This study investigates dynamic cerebral autoregulation assessed from spontaneous blood pressure (ABP) and cerebral blood flow velocity (CBFV) fluctuations and its time course in acute ischemic stroke. METHODS: Forty patients admitted with acute ischemic stroke in the territory of the middle cerebral artery (MCA) were enrolled. Admission National Institutes of Health Stroke score was 6+/-4. Study 1 was performed within 22 (+/-11) hours and study 2 was performed within 134 (+/-25) hours of ictus. The final analysis comprised 33 and 29 patients for study 1 and study 2, respectively. Twenty-five age- and sex-matched controls were studied. ABP (Finapres method) and CBFV in both MCAs (transcranial Doppler) were recorded over 10 minutes. Correlations between diastolic and mean ABP and CBFV fluctuations were averaged, yielding the correlation coefficient indices (Dx, Mx). Transfer function analysis was applied to obtain phase shift and gain between ABP and CBFV oscillations. RESULTS: No disturbance of autoregulation was indicated by all parameters at study 1. Separate analyses for clinical severity, stroke side, and size did not reveal significant differences for the various autoregulatory indices at study 1 and 2. At study 2, MCA flow velocity was significantly increased on both sides, the autoregulation index Mx was slightly but significantly (P<0.05) worse on both sides in comparison to study 1, and phase showed a trend toward poorer values on affected sides. No significant differences to controls occurred. Clinical outcome in patients completing both studies was good in all but one patient. CONCLUSIONS: Dynamic cerebral autoregulation assessed from spontaneous blood pressure fluctuations does not seem to be relevantly disturbed in early minor MCA stroke. At the subacute stage, slight autoregulatory disturbance may be present.

Retinal arterial occlusion due to embolism of suspected cardiac tumors -- report on two patients and review of the topic.

BACKGROUND: Ophthalmic complications due to heart tumors are rare. PATIENTS: This case report describes two patients with ocular complications, caused by a suspected cardiac tumor. A 56-year-old woman with arterial hypertension had a severe episode of headache coinciding with an acute loss of vision in her right eye and left-sided hemiparesis. A 20-year-old woman noticed sudden transient visual loss in her right eye. RESULT: The 56-year-old woman had an infarction on the right side of the middle and posterior cerebral arteries and, simultaneously, a central retinal artery occlusion (CRAO) in her right eye. Echocardiography revealed a tumor in the left atrium. The tumor disappeared after treatment with phenprocoumon within a few days. The diagnosis of a cardiac thrombus was made. The 20-year-old woman noticed recurrent episodes of sudden, transient visual loss in her right eye. A branch retinal arterial occlusion (BRAO) in her right eye was diagnosed. Echocardiography revealed a myxoma in the left atrium. The tumor was successfully excised surgically. CONCLUSION: In any vascular disturbance in the eye suspected to be embolic in origin, echocardiography should be carried out in order to exclude the presence of a heart disease.

The effect of carpal tunnel release on median nerve flattening and nerve conduction.

Carpal tunnel syndrome (CTS) is the most common entrapment neuropathy and extensive surveys have been given on the time course of electrophysiological findings pre- and postoperatively. In patients with clinical and electrophysiological confirmed diagnosis of CTS surgical decompression of the carpal tunnel is a first line treatment and has proven to be successfull in 70 to 90% of all cases. The objective of this work was to study the morphological changes of the median nerve after endoscopic release of the carpal tunnel. We used high resolution ultrasound to quantify flattening of the median nerve and to calculate a flattening ratio before endoscopic release as well as 2 weeks and 3 months postoperatively. Ten patients with clinical and electrophysiological confirmed CTS were included in the study. There was significant normalization of the calculated flattening ratio of the median nerve already 2 weeks after surgical release, whereas nerve conduction studies needed a longer period of time to normalize and thus were still abnormal 3 months postoperatively. We conclude that ultrasound is a simple and excellent objective method for visualizing the morphological recovery of the median nerve very early after decompression surgery. In complex cases with unsatisfactory outcome ultrasonography may prove useful in confirming successfull or failed decompression of the median nerve.

Effect of carotid endarterectomy or stenting on impairment of dynamic cerebral autoregulation.

BACKGROUND AND PURPOSE: Analysis of dynamic cerebral autoregulation (DCA) from spontaneous blood pressure fluctuations might contribute to prognosis of severe internal carotid artery stenosis, but its response to carotid recanalization has not been investigated so far. This study investigates the effect of carotid endarterectomy or stenting on various DCA parameters. METHODS: In 58 patients with severe unilateral stenosis undergoing carotid endarterectomy (n=41) or stenting (n=17), cerebral blood flow velocity (CBFV, transcranial Doppler) and arterial blood pressure (ABP, Finapres method) were recorded over 10 minutes before and on average 3 days after carotid recanalization. Nineteen patients were additionally examined after 7 months. Correlations between diastolic and mean ABP and CBFV fluctuations were averaged to form the correlation coefficient indices (diastolic [Dx] and mean values [Mx]). Transfer function parameters (low-frequency phase and high-frequency gain between ABP and CBFV oscillations) were calculated over the same 10 minutes. CO2 reactivity was assessed via inhalation of 7% CO2. RESULTS: Before recanalization, all DCA parameters were clearly impaired ipsilaterally compared with contralateral sides. Phase, Dx, and Mx indicated early normalization of DCA after both endarterectomy and stenting. By multiple regression, the degree of DCA improvement was highly significantly related to the extent of impairment before recanalization. No significant change in DCA was found at follow-up. Ipsilateral gain and CO2 reactivity increased significantly less after endarterectomy than after stenting (P<0.05). CONCLUSIONS: Dynamic cerebral dysautoregulation in patients with severe carotid obstruction is readily and completely remedied by carotid recanalization.

Cerebral autoregulation in carotid artery occlusive disease assessed from spontaneous blood pressure fluctuations by the correlation coefficient index.

BACKGROUND AND PURPOSE: Estimation of dynamic cerebral autoregulation from spontaneous fluctuations of arterial blood pressure (ABP) and cerebral blood flow velocity (CBFV) is an attractive monitoring option for cerebral hemodynamic impairment. We evaluated the correlation coefficient index method in patients with severe obstructive carotid disease and compared it with transfer function analysis (frequency domain approach to cerebral autoregulation) and CO2 vasomotor reactivity. METHODS: In 139 patients with severe unilateral carotid stenosis (>or=70%) or occlusion, CBFV (transcranial Doppler) and ABP (Finapres method) were recorded over 10 minutes. Correlations between systolic pressure, diastolic pressure, and mean ABP and CBFV oscillations over 1-minute epochs were averaged over 10 minutes to form the correlation coefficient indexes (Sx, Dx, Mx, respectively). Transfer function parameters (phase shift and gain between ABP and CBFV oscillations) were determined from the entire 10-minute period. CO2 reactivity was assessed by inhalation of 7% CO2. RESULTS: The correlation indexes Dx and Mx were significantly higher ipsilateral to stenosis and increased with degree of stenosis, indicating increasing dependence of CBFV on ABP and thus impairment of cerebral autoregulation. Dx and Mx correlated moderately but highly significantly with transfer function parameters and CO2 reactivity and showed a good level of agreement in detecting pathological values. Patients with a small variance of the 1-minute source correlations of Dx and Mx showed clearly better correlation values. Transfer function parameters and CO2 reactivity but not Dx and Mx were significantly poorer in patients with symptomatic stenosis or occlusion. CONCLUSIONS: The potential of the correlation coefficient indexes Dx and Mx in detecting hemodynamic impairment in patients with carotid stenosis is comparable to that of transfer function analysis and CO2 reactivity testing. In future, a combination of various hemodynamic tests might help to identify patients at risk for ischemic events.

Dissection of the vertebral artery with cervical nerve root lesions.

Vertebral artery dissection may cause upper limb peripheral motor deficit. We report three young patients presenting with nuchal pain followed by a nearly painless proximal paresis of the arm several days later. The cause, as detected by colour-coded Duplex sonography and MRI, was an extracranial dissection of the vertebral artery. The proximity of the intervertebral segment to the vertebral artery and the nerve roots indicated that compression by an intramural haematoma was the likely cause of the disorder. Subsequent examinations during anticoagulation treatment showed almost complete disappearance of the intramural haematoma and of the neurological deficits within a few weeks. We believe that the occurrence of an upper limb peripheral motor deficit should be added to the spectrum of potentially misleading signs of vertebral artery dissection.

Prevention of serious ophthalmic and cerebral complications in temporal arteritis?

PATIENTS: Five patients (mean age 81.6 years) developed bilateral blindness and 3 additional patients suffered cerebral strokes (mean age 58 years) due to temporal arteritis. Bilateral blindness and strokes occurred despite corticosteroid treatment. RESULTS: In all patients with temporal arteritis, the diagnosis was made too late. Patients with bilateral blindness were referred to the Eye Hospital when one eye had already become blind. The delay between the first symptoms and blindness in one eye was (average) 7 weeks. The interval between blindness of the first and second eyes was (average) 5 days in 3 patients, and simultaneous blindness in both eyes occurred in 2 patients. The other eye also became blind despite mega-doses of prednisone in 3 patients. Three additional patients already showed neurological signs and symptoms at the beginning of the temporal headache. All 3 patients developed strokes after some weeks or months. The wrong diagnosis was made in the first examination(s) by the physician with patients having prodromal signs or symptoms, but who also showed signs of other vascular diseases (diabetes mellitus, hypertension or occlusion of the internal carotid artery) which masked the inflammatory disease of temporal arteritis. CONCLUSIONS: Early diagnosis is essential to prevent severe complications. In patients with a cerebral stroke the early neurological deficits are warning signs which means that one must observe the patient regularly at short intervals. After the diagnosis has been settled, treatment of the patients for several months with a high dosage of corticosteroids is mandatory.

Dynamic cerebral autoregulation testing as a diagnostic tool in patients with carotid artery stenosis.

Evaluation of dynamic cerebral autoregulation might yield a physiologically more adequate measure of cerebral hemodynamic impairment in carotid artery stenosis than CO2-reactivity. This study re-evaluates and compares the Valsalva maneuver (VM) and phase shift during deep breathing. Nineteen patients with severe carotid artery stenosis and 17 age-matched controls were examined using transcranial Doppler sonography and non-invasive blood pressure recordings (Finapres). Phase shift was determined by cross-spectral analysis, responses to VM were graded by the formerly-introduced autoregulation slope index (ASI) and the new Valsalva time index (VTI). Phase shift and autoregulatory indices were significantly reduced on the affected side (p < 0.001). Correlations with CO2-reactivity were significant when pooling values of controls and patients (r from 0.54 to 0.78; p < 0.001). Correlations except for the VTI (r = -0.65; p = 0.002) were not significant considering only the affected side in patients. Correlations of pooled values between phase shift and VM-derived indices were significant (VTI r = -0.62; p < 0.001; ASI r = 0.49; p < 0.001), within patients only when comparing side-to-side differences (VTI r = -0.58; p = 0.009; ASI r = 0.52; p = 0.023). In conclusion, detection of impaired cerebral autoregulation is possible both by deep breathing and VM. The new VTI seems to be more suitable than the conventional ASI. Inter-method agreement concerning the extent of impairment is only acceptable for intra-individual side-to-side differences. Since absolute values of one autoregulation testing method or CO2-reactivity alone might fail, various tests should be combined for comprehensive assessment of cerebral hemodynamic impairment.

Optimized transcranial Doppler technique for the diagnosis of cardiac right-to-left shunts.

Transcranial Doppler sonography (TCD) is a simple method to detect a right-to-left cardiac shunt, although standardized procedures do not exist. In this study 69 patients were tested according to predetermined criteria and procedures (cluster of > 10 microbubbles, duration between injection in the cubital vein and detection in the middle cerebral artery [MCA] < or = 10 sec). Agitated saline solution was compared to oxypolygelatine, a plasma volume expander, as contrast media. Valsalva's maneuver and coughing were used to provoke right-to-left cardiac shunting, detected by TCD, transthoracic echocardiography (TTE), and transesophageal echocardiography (TEE). Oxypolygelatine caused a significantly higher number of microbubbles in the right atrium and MCA than did the saline solution, leading to a greater diagnostic reliability of TCD (paired t test, p < 0.001). Coughing did not provoke right-to-left cardiac shunts (x2 analysis, p < 0.001). The technique used for carrying out Valsalva's maneuver was important for the detection of right-to-left cardiac shunts. Twenty-five right-to-left shunts were diagnosed with TCD and 18 with TTE (36 vs 26%; x2 analysis, p = 0.1). The findings indicate that TCD when properly done is highly sensitive and specific for the diagnosis of right-to-left cardiac shunts.

Intravascular ultrasound Doppler measurement of blood flow velocity.

BACKGROUND AND PURPOSE: The authors investigated the feasibility and accuracy of intravascular Doppler sonography (IVDS) with a newly developed microprobe. METHODS: The known method to determine blood flow velocity by transcutaneous Doppler sonography was transferred to an intravascular usable Doppler probe. With the improved technique, a microprobe measuring 0.3 mm in diameter can be advanced through a 5F catheter used in routine diagnostic angiography to perform intravascular Doppler sonography. In a first step, the conditions for application and measurement were studied in a flow tube model and were transferred in a second step to patients undergoing routine angiography and patients with arterial stenoses. RESULTS: Measurements with nondegassed liquids showed a high intensive acoustic signal, but no echo effect could be recorded in degassed liquids. IVDS of healthy vessels in 40 patients showed the same typical flow pulse curve as seen in transcutaneous measurements. The optimal position of the microprobe with respect to the contact of the vessel wall, the diastolic and systolic phase, and the distance to the tip of the catheter could be evaluated. In 95.6% of the 40 patients with healthy vessels, IVDS was successful. Fourteen patients with arterial stenotic diseases were investigated before and after percutaneous transluminal angioplasty, and the results of these investigations correlated well with the angiographical results. CONCLUSIONS: For percutaneously directly reachable vessels, the transcutaneous Doppler sonography is the choice for easy noninvasive and inexpensive measurement of blood flow velocity. However, for vessels that are difficult or impossible to reach percutaneously, intravascular measurement is a valid procedure.

Multimodality monitoring during passive tilt and Valsalva maneuver under hypercapnia.

In occlusive cerebrovascular disease cerebral blood flow (CBF) autoregulation can be impaired and constant CBF during fluctuations in blood pressure (BP) cannot be guaranteed. Therefore, an assessment of cerebral autoregulation should consider not only responsiveness to CO2 or Diamox. Passive tilting (PT) and Valsalva maneuver (VM) are established tests for cardiovascular autoregulatory function by provoking BP changes. To develop a comprehensive test for vasomotor reactivity with a potential increase of sensitivity and specificity, the authors combined these maneuvers. Blood pressure, corrected to represent arterial pressure at the level of the circle of Willis, middle cerebral artery Doppler frequencies (DF), heart rate (HR) and endtidal partial pressure of CO2 (PtCO2) were measured continuously and noninvasively in 81 healthy subjects (19-74 years). Passive tilt and Valsalva maneuver were performed under normocapnia (mean, 39 + 4 mmHg CO2) and under hypercapnia (mean, 51 + 5 mm Hg CO2). Resting BP, HR, and DF increased significantly under hypercapnia. Under normocapnia and hypercapnia, PT induced only minor, nonsignificant changes in mean BP at the level of the circle of Willis compared to baseline (normocapnia: + 2 + 15 mm Hg; hypercapnia: -3 +/- 13 mm Hg). This corresponded with a nonsignificant decrease of the mean of DF (normocapnia: -4 +/- 11%; hypercapnia -6 +/- 12%). Orthostasis reduced pulsatility of BP by a predominantly diastolic increase of BP without significant changes in pulsatility of DF. Valsalva maneuver, with its characteristic rapid changes of BP due to elevated intrathoracic pressure, showed no significant BP differences in changes to baseline between normocapnic and hypercapnic conditions. Under both conditions the decrease in BP in phase II was accompanied by significantly increased pulsatility index ratio (PIDF/PIBP). Valsalva maneuver and PT as established tests in autonomic control of circulation provoked not only changes in time-mean of BP but also in pulsatility of BP. The significant increase in pulsatility ratio and decrease of the DF/BP ratio during normocapnia and hypercapnia indicated preserved CBF autoregulation within a wide range of CO2 partial pressures. Hypercapnia did not significantly influence the autoregulatory indices during VM and PT. Physiologically submaximally dilated cerebral arterioles can guarantee unchanged dynamics of cerebral autoregulation. Combined BP and MCA-DF assessment under hypercapnia enables investigating the effect of rapid changes of blood pressure on CO2-induced predilated cerebral arterioles. Assuming no interference of hypercapnia-induced vasodilation, VM, with its rapid, distinct changes in BP, seems especially to be adequate provocation for CBF autoregulation. This combined vasomotor reactivity might provide a more sensitive diagnostic tool to detect impaired cerebral autoregulation very early.