Establishment of the Cardio-Ankle Vascular Index in Patients With Obstructive Sleep Apnea
Department of Clinical Physiology, Toranomon Hospital, Tokyo, Japan Chest
(Impact Factor: 7.48).
07/2009; 136(3):779-86. DOI: 10.1378/chest.09-0178
An arterial stiffness parameter, the cardio-ankle vascular index (CAVI), has been developed. CAVI is adjusted for BP and can be used to measure arterial stiffness with little influence of BP. The purpose of this study was to evaluate the reproducibility, validity, and clinical usefulness of CAVI among patients with obstructive sleep apnea (OSA), who often have elevated BP during measurement.
Overall, 543 consecutive patients with OSA were studied. CAVI was automatically calculated from the pulse volume record, BP, and the vascular length from the heart to the ankle. First, CAVI was measured three times on different days in 25 patients to evaluate its reproducibility. Second, the correlation between CAVI and BP was assessed. Third, patients were classified into two groups (mild OSA or moderate-to-severe OSA), and the CAVIs of these groups were compared. Fourth, the correlation between CAVI and carotid intima-media thickness (IMT) was also assessed in 74 patients.
The mean coefficient of variation was 2.8. CAVI demonstrated weak or no correlations with BP (with systolic BP, r = 0.184; with diastolic BP, r = 0.223). Patients with moderate-to-severe OSA (n = 469) had a significantly greater CAVI than patients with mild OSA (p = 0.034). CAVI was positively correlated with IMT (r = 0.487).
The measurement of CAVI demonstrated good reproducibility and was not affected by the BP during measurement. Additionally, CAVI was positively correlated with another arteriosclerosis indicator. CAVI was higher in patients with more severe OSA and is regarded as a clinically useful index for the progression of vascular damage.
Available from: PubMed Central
- "We have previously reported that the CAVI measures arterial stiffness independent of blood pressure6. Increased arterial stiffness has been reported to be complicated by metabolic syndrome7, sleep apnea syndrome8 and smoking9. However, a detailed relationship between hyperglycemia and arterial stiffness has not been fully clarified. "
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ABSTRACT: AbstractAims/IntroductionAlthough arteriosclerotic diseases have been reported to be frequently complicated by diabetes mellitus (DM), a detailed relationship between hyperglycemia and arterial stiffness has not been fully clarified. We investigated the influence of hyperglycemia on arterial stiffness using the cardio‐ankle vascular index (CAVI), which is a new method for estimating arterial stiffness.Materials and Methods
CAVI values of 52 early‐staged DM patients (duration <5 years, no microangiopathies) were compared with those of 43 age‐matched non‐diabetic (NDM) subjects. The association between CAVI and clinical background factors was evaluated. The effect of glycemic improvement on CAVI was examined in 36 DM patients who were hospitalized for 2 weeks to treat hyperglycemia. CAVI and clinical parameters were measured twice during hospitalization and again after 8 weeks. Additionally, we measured CAVI before and 2 h after breakfast in five DM and five NDM subjects.ResultsThe CAVI of DM patients was significantly higher than that of NDM subjects. Multiple regression analysis showed that neither hypertension, obesity nor dyslipidemia, but aging and hemoglobin A1c (HbA1c) were significantly related to CAVI elevation. The CAVI, HbA1c and total cholesterol (TC) had significantly improved. Improvement of CAVI was significantly associated with HbA1c improvement. In contrast, no significant association was observed between the improvements of TC and CAVI. CAVI values before and after breakfast did not change significantly.Conclusions
CAVI elevation seems to be a sensitive arteriosclerotic marker, which is closely associated with hyperglycemia and improved by glycemic control.
Available from: sciencedirect.com
- "CAVI was measured using a Vasera VS-1000 device (Fukuda Denshi, Tokyo, Japan) while the subjects were awake between 8:00 AM and 12:00 noon, and on the same day, blood pressure (BP) data, anthropometric data, and blood samples were collected. CAVI reflects the stiffness of the aorta, femoral arteries, and tibial arteries as a whole  . "
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ABSTRACT: It has been reported that patients with obstructive sleep apnea (OSA) have an elevated arterial stiffness, and alleviation of OSA by continuous positive airway pressure (CPAP) might attenuate this. Recently, the cardio-ankle vascular index (CAVI) has been reported to be a highly reproducible arterial stiffness parameter in OSA patients. However, the change in CAVI that occurs following long-term CPAP treatment for OSA remains unclear.
Patients with moderate-to-severe OSA were enrolled. Changes in CAVI at 1 and 12 months after CPAP initiation (ΔCAVI(1) and ΔCAVI(12), respectively) were assessed. Factors associated with ΔCAVI(1) and ΔCAVI(12) were determined by multivariable regression analyses.
Thirty subjects were assessed. CAVI was significantly reduced at 1 month compared with the baseline from 7.80 ± 1.19 to 7.56 ± 1.08 (p = 0.013). A non-significant reduction was observed at 12 months (7.72 ± 1.18, p = 0.365 versus baseline) and CAVI had actually increased compared with that measured at 1 month. In multivariable analyses, ΔCAVI(1) was inversely correlated with CPAP usage (coefficient: -0.500, p = 0.006) and was directly correlated with the change in the ratio of low frequency to high frequency in heart rate variability (coefficient: 0.607, p < 0.001), whereas ΔCAVI(12) was related to the use of angiotensin-converting enzyme inhibitors (ACE-I) or angiotensin-II-receptor blockers (ARB; coefficient: 0.464, p = 0.013), was directly correlated with the change in hemoglobin A1c levels (coefficient: 0.644, p < 0.001), and was inversely correlated with the change in CPAP usage (coefficient: -0.380, p = 0.046).
CAVI was significantly reduced by short-term CPAP and then slightly increased from 1 to 12 months, which was probably due to natural progression associated with the aging process. However, long-term CPAP treatment had the beneficial effect of maintaining CAVI below baseline levels when associated with the use of ACE-I/ARB, the control of blood glucose and the CPAP compliance.
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ABSTRACT: A three-layer adaptive clustering neural net is described for
distortion-invariant multiclass object recognition in difficult problems
requiring piecewise nonlinear discriminant surfaces. The number of
hidden-layer neurons is determined by an organized procedure (several
neurons are used per class as prototypes of each class). These are
chosen by clustering techniques. The vector description of each
prototype in the multidimensional input feature space specifies a set of
linear discriminant functions that are the initial input to the
hidden-layer weights used. These weights are then refined by a neural
net algorithm using conjugate gradient techniques to produce the final
weights. A neural net (NN) that marries pattern-recognition and NN
techniques is thus obtained. Various multiclass distortion-invariant
classification results are presented
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