15 research outputs found
Determination of the mean cross-sectional area of the thoracic aorta using a double indicator dilution technique
A double indicator dilution technique for determining the mean cross-sectional area (CSA) of a blood vessel in vivo is presented. Analogous to the thermodilution method, dilution of hypertonic saline was measured by an electrical conductance technique. Because the change in conductance rather than absolute conductance was used to calculate CSA, pulsatile changes in shear rate of blood and conductance of surrounding tissues had no effect on the data. To calculate CSA from an ion mass balance, cardiac output was needed and estimated from the thermodilution curve using the same 'cold' (hypertonic) saline injection. The mean CSA, obtained from this double indicator dilution method (CSA(GD)), was compared with the CSA obtained from the intravascular ultrasound method (IVUS) in 44 paired observations in six piglets. The regression line is close to the line of identity (CSA(GD) = -1.83 + 1.06 · CSA(IVUS), r = 0.96). The difference between both CSAs was independent of the diameter of the vessel, on average -0.99 mm2 ± 2.64 mm2 (mean CSA(GD) = 46.84 ± 8.21 mm2, mean CSA(IVUS) = 47.82 ± 9.08 mm2) and not significant. The results show that the double indicator dilution method is a reliable technique for estimating the CSA of blood vessels in vivo
What have we learned from in vitro intravascular ultrasound?
In vitro studies have established that intravascular ultrasound is a reliable technique for accurate assessment of vascular anatomic structure and disease conditions before and after intervention. In addition, quantitative data from intravascular ultrasound studies correspond well with histologic findings, which serve as the gold standard. These in vitro studies permit the understanding and interpretation of ultrasound images obtained in vivo, although differences between the two settings should be taken into account. New ultrasound modalities currently being developed may enhance the diagnostic differentiation of plaque morphologic characteristics and facilitate on-line quantitative assessment of vessel structure
Shrinkage of the distal renal artery 1 year after stent placement as evidenced with serial intravascular ultrasound
The objective of this study was to determine the quantitative
intravascular ultrasound (IVUS) and angiographic changes that occur during
1 year follow-up after renal artery stent placement, given that restenosis
continues to be a limitation of renal artery stent placement. 38
consecutive patients with symptomatic renal artery stenosis treated with
Palmaz stent placement were studied prospectively. IVUS and angiography
were performed at the time of stent placement and at 1 year follow-up. At
follow-up, angiographic restenosis was seen in 14% of patients. The lumen
area in the stent, seen with IVUS, was significantly decreased from
24+/-5.6 mm(2) to 17+/-5.6 mm(2) (p<0.001) solely due to plaque
accumulation. The distal main renal artery showed a significant decrease
in lumen area owing to a significant vessel area decrease from 39+/-14.0
mm(2) to 29+/-9.3 mm(2) (p<0.001) without plaque accumulation.
Angiographic analysis confirmed this reduction in luminal diameter and
showed that the distal renal artery diameter at follow-up was
significantly smaller than before stent placement (86+/-23.0% vs
104+/-23.9% of the contralateral renal artery diameter; p=0.003). Besides
plaque accumulation in the stent, unexplained shrinkage of the distal main
renal artery was evidenced with IVUS and angiography 1 year following
stent placement
Temporal averaging for quantification of lumen dimensions in intravascular ultrasound images
Quantitative analysis of arterial dimensions from high frequency intravascular ultrasound images (30 MHz) may be hampered by strong blood scattering. Replacement of blood by saline is one method to provide a clear view of the arterial lumen; another method is that of temporal averaging of successive ultrasound images. The accuracy of this latter method was tested by comparing the lumen area measurements on the temporal-averaged image, with the data of the same cross-section obtained from the single-frame and saline-filled images. The mean lumen area measured on the temporal-averaged images was similar to that measured on the single-frame images (mean difference: −0.02 ± 1.16 mm2; p = ns). The mean lumen a
Intravascular ultrasound evidence for coarctation causing symptomatic renal artery stenosis
BACKGROUND: A recent study of human cadaveric renal arteries revealed that
renal artery narrowing could be due not only to atherosclerotic plaque
compensated for by adaptive remodeling, but also to hitherto undescribed
focal narrowing of an otherwise normal renal arterial wall (ie,
coarctation). The present study investigated whether vessel coarctation
could be identified in patients with symptomatic renal artery stenosis
(RAS). METHODS AND RESULTS: Consecutive symptomatic patients with
angiographically proven atherosclerotic RAS who were referred for stent
placement were studied by 30-MHz intravascular ultrasound before
intervention (n=18) or after predilatation (n=18). Analysis included
assessment of the media-bounded area and plaque area (PLA) at the most
stenotic site and at a distal reference site (most distal cross-section in
the main renal artery with normal appearance). Coarctation was considered
present whenever the target/reference media-bounded area was </=85%.
Before intervention, coarctation was observed in 9 of 18 patients and
adaptive remodeling in 9 of 18 patients. Coarctation lesions had a
significantly smaller PLA than adaptive remodeled lesions (P=0.001).
Similarly, despite predilatation, coarctation was seen in 8 of 18 patients
who had significantly smaller PLAs (P=0. 008) when compared with those
patients who had adaptive remodeled lesions. No differences in severity of
RAS or angiographic or clinical parameters were observed. CONCLUSIONS:
Low-plaque coarctation may cause a considerable proportion of symptomatic
RAS, which is angiographically and clinically indistinguishable from
plaque-rich RAS
A comparison of balloon injury models of endovascular lesions in rat arteries
BACKGROUND: Balloon injury (BI) of the rat carotid artery (CCA) is widely
used to study intimal hyperplasia (IH) and decrease in lumen diameter
(LD), but CCA's small diameter impedes the evaluation of endovascular
therapies. Therefore, we validated BI in the aorta (AA) and iliac artery
(CIA) to compare it with CCA. METHODS: Rats underwent BI or a sham
procedure (control). Light microscopic evaluation was performed either
directly or at 1, 2, 3, 4 and 16 weeks follow-up. The area of IH and the
change in LD (LD at 16 weeks minus LD post BI) were compared. RESULTS: In
the BI-groups the area of IH increased to 0.14 +/- 0.08 mm2 (CCA), 0.14
+/- 0.03 mm2 (CIA) and 0.12 +/- 0.04 mm2 (AA) at 16 weeks (NS). The LD
decreased with 0.49 +/- 0.07 mm (CCA), compared to 0.22 +/- 0.07 mm (CIA)
and 0.07 +/- 0.10 mm (AA) at 16 weeks (p < 0.05). The constrictive
vascular remodelling (CVR = wall circumference loss combined with a
decrease in LD) was -0.17 +/- 0.05 mm in CIA but absent in CCA and AA. No
IH, no decrease in LD and no CVR was seen in the control groups.
CONCLUSIONS: BI resulted in: (1.) a decrease in LD in CCA due to IH, (2.)
a decrease in LD in CIA due to IH and CVR, (3.) no change in LD in AA,
(4.) Comparable IH development in all arteries, (5.) CCA has no vasa
vasorum compared to CIA and AA, (6.) The CIA model combines good access
for 2 F endovascular catheters with a decrease in LD due to IH and CVR
after BI
Stent placement for renal arterial stenosis: where do we stand? A meta-analysis
PURPOSE: To perform a meta-analysis of renal arterial stent placement in
comparison with renal percutaneous transluminal angioplasty (PTA) in
patients with renal arterial stenosis. MATERIALS AND METHODS: Studies
dealing with renal arterial stent placement (14 articles; 678 patients)
and renal PTA (10 articles; 644 patients) published up to August 1998 were
selected. A random-effects model was used to pool the data. RESULTS: Renal
arterial stent placement proved highly successful, with an initial
adequate performance in 98% and major complications in 11%. The overall
cure rate for hypertension was 20%, whereas hypertension was improved in
49%. Renal function improved in 30% and stabilized in 38% of patients. The
restenosis rate at follow-up of 6-29 months was 17%. Stent placement had a
higher technical success rate and a lower restenosis rate than did renal
PTA (98% vs 77% and 17% vs 26%, respectively; P <.001). The complication
rate was not different between the two treatments. The cure rate for
hypertension was higher and the improvement rate for renal function was
lower after stent placement than after renal PTA (20% vs 10% and 30% vs
38%, respectively; P <.001). CONCLUSION: Renal arterial stent placement is
technically superior and clinically comparable to renal PTA alone