Selective use of embolic protection devices during saphenous vein grafts interventions: a single-center experience

OBJECTIVES

To report on outcomes with selective use of embolic protection devices (EPD) during percutaneous coronary intervention (PCI) to saphenous vein grafts (SVG).

BACKGROUND

PCI to SVG is associated with increased risk and the use of EPD is recommended in this setting.

METHODS

Angiographic and clinical outcomes were prospectively obtained from 534 consecutive patients who underwent PCI to SVG with or without EPD at a tertiary cardiac centre. Long-term outcomes were obtained by linkage to a provincial registry.

RESULTS

EPD, deployed in 198 of 373 SVGs (53%) suitable for deployment of a distal EPD, were used more often in ectatic (33% vs. 19%, P = 0.003), ulcerated (17% vs. 9%, P = 0.03), thrombotic (26% vs. 10%, P < 0.0001) vein grafts, with longer degenerated segments (P = 0.002), and in lesions involving the body of the graft (85% vs. 66%, P < 0.0001), and less with lesions involving the graft ostium (29% vs. 44%, P = 0.003). Patients suitable for but not receiving EPD tended to be more likely to have a periprocedural myocardial infarction. During 3 years of follow-up, 49% of the patients had a cardiovascular event. Cumulative mortality was 8.4%, 18.8% and 14.7% in patients unsuitable for distal EPD, suitable but without EPD, and with EPD (p = 0.11). Nonuse of EPD was an independent predictor of MACE at 3 years. (P = 0.02).

CONCLUSIONS

Selective use of EPD is associated with low in-hospital cardiovascular event rates. Long-term outcomes are manifested by a high rate of events, especially in patients with SVG's suitable for but not receiving EPD. This suggests that routine use of distal EPD may be warranted in unselected patients with suitable SVG anatomy.

Assessment of endothelial function by non-invasive peripheral arterial tonometry predicts late cardiovascular adverse events

AIMS

There is growing need for the identification of novel non-invasive methodologies for the identification of individuals at risk for adverse cardiovascular (CV) events. We examined whether endothelial dysfunction, as detected by non-invasive peripheral arterial tonometry (EndoPAT), can predict late CV events.

METHODS AND RESULTS

Reactive hyperaemia (RH) was induced following upper arm occlusion of systolic blood pressure in 270 outpatients (54 +/- 12 years, 48% female). The natural logarithmic scaled RH index (L_RHI) was calculated from the ratio between the digital pulse volume during RH and at baseline. The patients were followed for CV adverse events (AE: cardiac death, myocardial infarction, revascularization or cardiac hospitalization) during a 7-year follow-up (inter-quartile range = 4.4-8). Cox models were used to estimate the association of EndoPAT results with AE adjusted for age. During the follow-up, AE occurred in 86 patients (31%). Seven-year AE rate was 48% in patients with L_RHI < 0.4 vs. 28% in those with L_RHI >or= 0.4 (P = 0.03). Additional univariate predictors of AE were advancing age (P = 0.02) and prior coronary bypass surgery (P = 0.01). The traditional Framingham risk score was not higher in patients with AE. Multivariate analysis identified L_RHI < 0.4 as an independent predictor of AE (P = 0.03).

CONCLUSION

A low RH signal detected by EndoPAT, consistent with endothelial dysfunction, was associated with higher AE rate during follow-up. L_RHI was an independent predictor of AE. Non-invasive assessment of peripheral vascular function may be useful for the identification of patients at risk for cardiac AEs.

Segmental coronary endothelial dysfunction in patients with minimal atherosclerosis is associated with necrotic core plaques

BACKGROUND/OBJECTIVE

Endothelial dysfunction and atherosclerosis are systemic disorders, but are often characterised by segmental involvement and complications. A potential mechanism for local involvement early in the disease process may be related to plaque composition. This study was designed to test the hypothesis that in patients with minimal coronary atherosclerosis, coronary artery segments with abnormal endothelial function have specific plaque characteristics.

METHODS

Intravascular ultrasound (IVUS) images were obtained from 30 patients who underwent coronary endothelial function assessment. Spectral analysis of the IVUS radiofrequency data was used for assessment of plaque composition. IVUS findings of the coronary sections were compared according to the corresponding endothelial response to acetylcholine.

RESULTS

Sections with a decrease epicardial coronary arterial diameter in response to acetylcholine had smaller baseline lumen (7.5 (2.4) mm(2) vs 8.8 (3.3) mm(2), p = 0.006) but larger plaque burden (37.1% (9.4%) vs 31% (7%), p = 0.003) than sections with normal endothelial response. Sections with endothelial dysfunction had larger necrotic core plaques: 0.13 (0.03-0.33) mm(2) vs 0.0 (0.0-0.07), p<0.001 and more dense calcium: 0.03 (IQR 0.0-0.13) mm(2) vs 0.0 (0.0-0.10) mm(2), p<0.01), than those with normal endothelial response. Only necrotic core area was associated with endothelial dysfunction (p<0.001) after adjusting for other measures.

CONCLUSIONS

This study suggests that local coronary endothelial dysfunction in patients with minimal coronary atherosclerosis is associated with plaque characteristics that are typical of vulnerable plaques.

Identification of the gene causing long QT syndrome in an Israeli family

BACKGROUND

Long QT syndrome is an inherited cardiac disease, associated with malignant arrhythmias and sudden cardiac death.

OBJECTIVES

To map and identify the gene responsible for LQTS in an Israeli family.

METHODS

A large family was screened for LQTS after one of them was successfully resuscitated from ventricular fibrillation. The DNA was examined for suspicious loci by whole genome screening and the coding region of the LQT2 gene was sequenced.

RESULTS

Nine family members, 6 males and 3 females, age (median and interquartile range) 26 years (13, 46), who were characterized by a unique T wave pattern were diagnosed as carrying the mutant gene. The LQTS-causing gene was mapped to chromosome 7 with the A614V mutation. All of the affected members in the family were correctly identified by electrocardiogram. Corrected QT duration was inversely associated with age in the affected family members and decreased with age.

CONCLUSIONS

Careful inspection of the ECG can correctly identify LQTS in some families. Genetic analysis is needed to confirm the diagnosis and enable the correct therapy in this disease.

Sex differences in vascular and endothelial responses to acute mental stress

OBJECTIVE

Our objective was to assess the differences in systemic vascular and endothelial function in response to acute mental stress between men and women. The endothelium plays a pivotal role in vascular homeostasis and the development of atherosclerotic heart disease. The mechanism and presentation of cardiovascular events show a sex-based difference, although the sex difference in the vascular and endothelial response to mental stress is not known.

METHODS

Male (n = 34) and female (n = 53) subjects participated in a series of three different mental stress tasks during which vascular response was measured non-invasively using peripheral arterial tonometry. Endothelial function was assessed using reactive hyperemia peripheral arterial tonometry. Double product (systolic blood pressure x heart rate) was calculated.

RESULTS

Males had a greater double product response (27.2 + 3.6% increase in double product vs. 19.2 + 1.7%; P = 0.01), and a greater vascular reactivity to mental stress. Females demonstrated a reduced response to reactive hyperemia (-0.47 vs. 13.74%; P = 0.01). Furthermore, a subgroup of females who showed the least vaso-reactivity to mental stress showed the greatest decline in endothelial function (-10.5 + 4% vs. 17.4 + 6.3%; P < 0.001).

INTERPRETATION

This study demonstrates sex-based differences in the vascular and endothelial responses to mental stress. The mental stress-induced reduction in endothelial function and increased double product seen in the females might manifest clinically as contributing to the pathophysiology of mental stress-mediated cardiovascular events in female patients and provide further information regarding the potential mechanism for sex differences in cardiac events.

Hormonal and volume dysregulation in women with premenstrual syndrome

Premenstrual syndrome (PMS) presents with emotional and physical symptoms. Although the emotional symptoms have been extensively studied, the pathophysiology of the fluid-retention symptoms is not currently known. We tested the hypothesis that the fluid regulatory mechanisms are disturbed in PMS. Nine regularly menstruating women with PMS were compared with 9 healthy age-matched women. Hemodynamic parameters and upright plasma volume shift (extrapolated from changes in hematocrit), plasma renin activity (PRA), and plasma aldosterone and sex hormones were measured at different times during the menstrual cycle. During the early follicular and the midluteal phases, the plasma volume shift, supine and upright PRA, and plasma aldosterone were similar in both groups, and none of the participants had edema. However, during the late luteal phase, ankle edema was present only in women with PMS, and their maximal plasma volume shift was lower compared with controls (11.7+/-1.3 versus 15.6+/-0.6; P=0.004). The area under the curve (estimates the amount of the total plasma shift during 30 minutes standing) was 300+/-28 and 406+/-16 in PMS and controls, respectively (P=0.01). PRA and aldosterone levels were higher during the late luteal phase in women with PMS compared with controls (supine PRA: 1.4+/-0.3 [PMS] versus 1.1+/-0.4 [control; P value not significant], upright PRA: 3.9+/-0.08 versus 1.6+/-0.3 ng/mL per hour [P=0.015], supine plasma aldosterone: 131+/-30 versus 68+/-17 pg/mL [P=0.09], and upright plasma aldosterone: 208+/-40 versus 102+/-16 pg/mL [P=0.03]). We, therefore, conclude that women with PMS have increased plasma fluid-regulatory hormones and disturbed fluid distribution only during their late luteal menstrual phase.

Association between the paraoxonase-1 192Q>R allelic variant and coronary endothelial dysfunction in patients with early coronary artery disease

OBJECTIVE

To test the hypothesis that allelic variants of the paraoxonase-1 gene are associated with endothelial dysfunction, an early stage of atherosclerosis.

PATIENTS AND METHODS

We assessed 192Q>R and 55L>M allelic variants of the paraoxonase gene and coronary endothelial function in response to intracoronary acetylcholine in 99 patients (52 with homozygous QQ, 47 with homozygous RR or heterozygous QR). The study was conducted from September 1, 2002, through November 30, 2004.

RESULTS

Of 52 homozygous QQ patients, 39 (75%) had endothelial dysfunction vs 20 (43%) of the 47 RR/QR patients (P=.001), and this association remained significant after adjustment in a multivariable linear regression model (P=.005). In homozygous QQ vs RR/QR patients, epicardial arterial diameter decreased more (% change in diameter, -22%+/-21% vs -9%+/-16%, respectively, P=.002), coronary blood flow increased less (+37%+/-77% vs +75%+/-75%, P=.02) in response to acetylcholine, and oxidized LDL levels were higher. The 55L>M allelic variant was not significantly associated with endothelial dysfunction and had no effect on the association between endothelial dysfunction and the 192Q>R allelic variant.

CONCLUSION

The 192Q>R allelic variant of the paraoxonase-1 gene is associated with coronary endothelial dysfunction. The current study provides further information regarding the potential mechanisms by which this allelic variant contributes to early atherosclerosis in humans.

The effect of drug eluting stents on cardiovascular events in patients with intermediate lesions and borderline fractional flow reserve

OBJECTIVE

To assess the role of fractional flow reserve (FFR) in guiding therapy in the drug eluting stent (DES) era.

BACKGROUND

FFR is a useful index for evaluation of the physiological significance of angiographically indeterminate coronary artery lesions. However, its role in the DES era is unknown.

METHODS

Long term outcome of 281 patients with angiographically indeterminate coronary lesions and borderline FFR (0.75 </= FFR < 0.9) was obtained. The outcome of patients who had a DES placed (n = 58), was compared with that of consecutive patients with borderline FFR that were treated by PCI with bare metal stents (BMS, n = 58), or were deferred from revascularization (n = 165).

RESULTS

FFR was significantly higher in the deferred group (median and IQR); 0.85 (0.82 to 0.88) compared with the BMS (0.78; 0.76 to 0.82) and the DES (0.79; 0.77 to 0.82), P < 0.001. Pretreatment FFR was a significant determinant of long term event rates in the deferred patients (P = 0.002) but had no effect in patients treated by PCI. In the deferred group, there were fewer events (death, myocardial infarction, target vessel revascularization) compared with the BMS group; but no significant difference was observed between the DES and the deferred groups.

CONCLUSIONS

In borderline FFR, long term outcome after PCI with BMS is inferior to conservative therapy or PCI with DES. While conservative management is preferable in these patients, PCI with DES may be considered in specific circumstances.

The interaction between coronary endothelial dysfunction, local oxidative stress, and endogenous nitric oxide in humans

In vitro and animal studies suggest that oxidative stress is associated with endothelial dysfunction. We tested whether local oxidative stress and nitric oxide (NO) bioavailability in the coronary circulation is associated with coronary endothelial dysfunction in humans. Blood samples were obtained simultaneously from the left main coronary artery and the coronary sinus for measurement of F2-isoprostanes, myeloperoxidase, nitrotyrosine, and superoxide dismutase in 20 patients without significant coronary disease. Afterward, coronary blood flow and the vascular response to intracoronary acetylcholine and NG-monomethyl-L-arginine (L-NMMA) were assessed. The gradient of isoprostanes between the arterial levels and coronary sinus correlated with the change in coronary artery diameter in response to acetylcholine (r=-0.79, P<0.0001). Isoprostanes net production across the left anterior descending artery territory correlated with a decrease in superoxide dismutase activity (r=0.66, P=0.002) and decrease in coronary artery diameter in response to L-NMMA (rs=0.48, P<0.05). Myeloperoxidase and nitrotyrosine gradients were similar in patients with endothelial dysfunction and controls. The effect of L-NMMA was similar in both groups. We conclude that coronary endothelial dysfunction in humans is characterized by local enhancement of oxidative stress without a decrease in basal NO release. This study supports the hypothesis that local oxidative stress has a role in reduction of NO bioavailability in humans with coronary endothelial dysfunction.

Coronary endothelial dysfunction and hyperlipidemia are independently associated with diastolic dysfunction in humans

BACKGROUND

Coronary endothelial dysfunction (CED) and DHF are both associated with myocardial ischemia and CAD risk factors. The objective of the this study was to determine if CED and CAD factors are associated with diastolic dysfunction before the development of occlusive CAD or clinical heart failure.

METHODS

Patients with normal ejection fraction and nonocclusive CAD who underwent coronary endothelial function studies were identified. Left ventricular relaxation was assessed by tissue Doppler assessment of early diastolic ascent of the septal mitral annulus (Ea). Multiple linear regression was used to investigate whether coronary risk factors influenced diastolic function after adjusting for the presence of CED.

RESULTS

A total of 160 patients had adequate assessment of diastolic relaxation. With multiple linear regression models, %deltaCBF (P = .018) was associated with a higher Ea; in contrast, older age (P < .001), female sex (P = .028), higher left ventricular mass index (P = .016), and higher nonhigh-density lipoprotein cholesterol (P = .022) were associated with a lower Ea.

CONCLUSION

Coronary endothelial dysfunction and hyperlipidemia are independently associated with impaired relaxation in patients with normal ejection fraction in the absence of occlusive CAD and heart failure. The current study suggests a new potential mechanism for the development of endothelial and diastolic dysfunction in humans.

Local Production of Lipoprotein-Associated Phospholipase A 2 and Lysophosphatidylcholine in the Coronary Circulation

Background— Lipoprotein-associated phospholipase A 2 (Lp-PLA 2 ) is a novel marker and participant in vascular inflammation. Inflammation also is associated with coronary atherosclerosis. We tested the hypothesis that local coronary production of Lp-PLA 2 is enhanced in patients with early coronary atherosclerosis and associated with local endothelial function.

Methods and Results— Coronary angiography, blood flow, flow reserve, endothelial function assessment, and intravascular ultrasound with volumetric analysis were performed in 15 patients with mild coronary atherosclerosis and in 15 control subjects. Plasma samples were collected simultaneously from the left main coronary artery and coronary sinus for measurement of Lp-PLA 2 , lysophosphatidylcholine (a product of Lp-PLA 2 ), and C-reactive protein. Hemodynamic parameters and cholesterol were similar in both groups. Arterial Lp-PLA 2 levels were similar in patients and control subjects: 225 ng/mL (interquartile range [IQR], 196 to 273 ng/mL) versus 221 ng/mL (IQR, 177 to 294 ng/mL). Lp-PLA 2 net production in the coronary circulation was higher in patients compared with control subjects: 519 ng/min (IQR, 198 to 1276 ng/min) versus −529 ng/min (IQR, −872 to −79 ng/min; P =0.001) and correlated with percent atheroma volume ( r s =0.37, P =0.04). Net production of lysophosphatidylcholine was higher in patients compared with control subjects: 199 ng/min (IQR, −592 to 470 ng/min) versus −505 ng/min (IQR, −1119 to 0 ng/min; P =0.03) and correlated with coronary endothelial dysfunction ( r s =0.5, P =0.005). C-reactive protein was not significantly different between the groups.

Conclusions— Early coronary atherosclerosis in humans is characterized by local production of Lp-PLA 2 . Local coronary production of lysophosphatidylcholine, the active product of Lp-PLA 2 , is associated with endothelial dysfunction. These results support the role for Lp-PLA 2 in the mechanism of regional vascular inflammation and atherosclerosis in humans.

Smoking is associated with epicardial coronary endothelial dysfunction and elevated white blood cell count in patients with chest pain and early coronary artery disease

BACKGROUND

Smoking is a major risk factor for cardiovascular events. One of the potential mechanisms may be related to both coronary endothelial dysfunction and increased inflammatory response. The present study was designed to test the hypothesis that smoking is associated with epicardial coronary endothelial dysfunction and inflammation.

METHODS AND RESULTS

Coronary endothelial function in response to acetylcholine was assessed in 881 patients (115 current smokers and 766 nonsmokers, including 314 previous smokers). Smokers were significantly younger than nonsmokers (43+/-1 versus 51+/-1 years, P<0.0001), had more epicardial vasoconstriction in response to intracoronary acetylcholine (-19+/-2% versus -14+/-1% change in coronary artery diameter, P=0.03), and were more likely than nonsmokers to have epicardial endothelial dysfunction (46% versus 35%, P=0.005), but their microvascular endothelial function was intact. Smokers had higher white blood cell counts than nonsmokers (7.7+/-0.2 versus 6.6+/-0.1x10(9)/L, P<0.0001), higher myeloperoxidase (156+/-19 versus 89+/-8 ng/mL), higher lipoprotein-associated phospholipase A2 (242+/-12 versus 215+/-5 ng/mL), and higher levels of intracellular adhesion molecule (283+/-14 versus 252+/-5 ng/mL). There were no differences in the levels of C-reactive protein, fibrinogen, or vascular cell adhesion molecule between the groups.

CONCLUSIONS

Young smokers are characterized by epicardial coronary endothelial dysfunction, preserved microvascular endothelial function, and increased levels of inflammatory biomarkers and oxidative stress. The present study provides further information regarding the potential mechanisms by which smoking contributes to cardiovascular events.

Defective ubiquitinylation of EGFR mutants of lung cancer confers prolonged signaling

Several distinct mutations within the kinase domain of the epidermal growth factor receptor (EGFR) are associated with non-small cell lung cancer, but mechanisms underlying their oncogenic potential are incompletely understood. Although normally ligand-induced kinase activation targets EGFR to Cbl-mediated receptor ubiquitinylation and subsequent degradation in lysosomes, we report that certain EGFR mutants escape this regulation. Defective endocytosis characterizes a deletion mutant of EGFR, as well as a point mutant (L858R-EGFR), whose association with c-Cbl and ubiquitinylation are impaired. Our data raise the possibility that refractoriness of L858R-EGFR to downregulation is due to enhanced heterodimerization with the oncogene product HER2, which leads to persistent stimulation.

Hyperglycemia during acute myocardial infarction in patients who are treated by primary percutaneous coronary intervention: impact on long-term prognosis

BACKGROUND

Transient hyperglycemia is common during acute myocardial infarction in non-diabetic patients and is associated with a worse outcome. There is limited data on the outcome of patients who undergo primary percutaneous coronary intervention and have transient hyperglycemia.

METHODS

Fasting plasma glucose was measured in 431 consecutive acute myocardial infarction patients who underwent primary percutaneous coronary interventions. Patients were classified into three groups: non-diabetics/non-hyperglycemic (NDNH, glucose < 126 mg/dL; n=224); non-diabetics/hyperglycemic (NDH, glucose > or = 126 mg/dL; n=119); and diabetics (n=88). Data were analyzed according to the different groups and according to exact glucose levels.

RESULTS

In-hospital mortality was significantly lower in NDNH (1%) compared to NDH (8%) and diabetic (5%) patients (p=0.01). One-year cumulative mortality was highest (10%) in patients with NDH (p<0.001). One year target lesion revascularization rates were identical in NDNH and NDH patients (6% vs. 8%) and higher in diabetic patients (19%, p=0.001). In a multivariate model, a striking increase in the risk of death (0.6%, p=0.05) and target lesion revascularization (2%, p<0.0001) was found for every increment of 1 mg/dL in glucose level.

CONCLUSIONS

Transient hyperglycemia in non-diabetic acute myocardial infarction patients who undergo primary percutaneous coronary interventions is associated with high one-year mortality. One year target lesion revascularization rates were significantly higher in diabetics compared to non-diabetics with normoglycemia or transient hyperglycemia.

Effect of aging on the cardiovascular regulatory systems in healthy women

Aging, independently from the hormonal status, is a major risk factor for cardiovascular morbidity in healthy women. Therefore, we studied the effect of healthy aging on the cardiovascular homeostatic mechanisms in premenopausal and postmenopausal women with similar estrogen levels. Twelve healthy postmenopausal women, confirmed by follicular-stimulating hormone (FSH) and luteal hormone (LH) levels, were compared with 14 normally menstruating women during the early follicular phase (young-EF), to avoid as much as possible the effects of estrogen. Systolic BP was 108 ± 1.5 vs. 123 ± 2.5 ( P < 0.001), supine norepinephrine was 260 ± 30 vs. 216 ± 45 and upright 640 ± 100 vs. 395 ± 50 pg/ml ( P = 0.05) in young-EF vs. postmenopausal, respectively. Plasma renin activity and aldosterone remained unchanged. Vagal cardiac tone indices decreased significantly with aging (young-EF vs. postmenopausal): high-frequency (HF) band, root mean square successive differences (rMSSD) and proportion of R-R intervals >50 ms (PNN50%) were 620 ± 140 vs. 270 ± 70 ( P = 0.04), 53 ± 7 vs. 30 ± 3 ( P = 0.02), and 23 ± 5 vs. 10 ± 3 ( P = 0.04), respectively. LF to HF ratio was 0.85 ± 0.17 in young-EF and became 1.5 ± 0.22 in postmenopausal ( P = 0.03). Both arms of the baroreflex, +BRS (29 ± 5 vs. 13.5 ± 2.5, P = 0.01) and −BRS (26 ± 4 vs. 15 ± 1.5, P = 0.02) decreased with aging. Cardiovascular α1-adrenoreceptor responsiveness significantly increased and β-decreased in postmenopausal compared with young EF ( P < 0.001, both). The corrected QT intervals (QTc) were similar, whereas corrected JT intervals (JTc) and JTc to QTc ratio were prolonged in the postmenopausal group. We conclude that in young women, parasympathetic control is the main regulator of the cardiovascular system and in postmenopausal women, sympathetic tone dominates. The transition from parasympathetic to sympathetic control may contribute to the increased cardiovascular morbidity with aging.

Impaired cerebral CO2 vasoreactivity: association with endothelial dysfunction

Conflicting data exist on the role of nitric oxide (NO) in cerebral blood flow (CBF) autoregulation. Previous studies involving human and animal subjects seem to indicate that NO involvement is limited to the CO(2)-dependent mechanism (chemoregulation) and not to the pressure-dependent autoregulation (mechanoregulation). We tested this hypothesis in patients with impaired endothelial function compared with healthy controls. Blood pressure, heart rate, end-tidal Pco(2), CBF velocities (CBFV), forearm blood flow, and reactive hyperemia were assessed in 16 patients with diabetes mellitus and/or hypertension and compared with 12 age- and sex-matched healthy controls. Pressure-dependent autoregulation was determined by escalating doses of phenylephrine. CO(2) vasoreactivity index was extrapolated from individual slopes of mean CBFV during normocapnia, hyperventilation, and CO(2) inhalation. Measurements were repeated after sodium nitroprusside infusion. Indexes of endothelial function, maximal and area under the curve (AUC) of forearm blood flow (FBF) changes, were significantly impaired in patients (maximal flow: 488 +/- 75 vs. 297 +/- 31%; P = 0.01, AUC DeltaFBF: 173 +/- 17 vs. 127 +/- 11; P = 0.03). Patients and controls showed similar changes in cerebrovascular resistance during blood pressure challenges (identical slopes). CO(2) vasoreactivity was impaired in patients compared with controls: 1.19 +/- 0.1 vs. 1.54 +/- 0.1 cm.s(-1).mmHg(-1); P = 0.04. NO donor (sodium nitroprusside) offsets this disparity. These results suggest that patients with endothelial dysfunction have impaired CO(2) vasoreactivity and preserved pressure-dependent autoregulation. This supports our hypothesis that NO is involved in CO(2)-dependent CBF regulation alone. CBFV chemoregulation could therefore be a surrogate of local cerebral endothelial function.