38 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
Effect of balloon angioplasty in femoropopliteal arteries assessed by intravascular ultrasound
Objective:To study the effects of balloon angioplasty (PTA) of the femoropopliteal artery with intravascular ultrasound (IVUS).Materials and methods:Corresponding IVUS cross-sections (n = 1033) obtained before and after PTA from 115 procedures were analysed. Vascular damage including plaque rupture, dissection and media rupture was assessed. Free lumen area (FLA), media-bounded area (MBA) and plaque area (PLA) were measured.Results:After PTA vascular damage was seen at the target site in 83 (72%) arteries: plaque rupture in 30 (26%), dissection in 66 (57%) and media rupture in 20 (17%) arteries. The FLA increased from 5.4 ± 3.4 mm2 to 14.1 ± 5.0 mm2 (p<0.001), MBA increased from 26.9 ± 10.0 mm2 to 32.9 ± 10.7 mm2 (p<0.001) and PLA decreased from 21.6 ± 8.5 mm2 to 18.8 ± 8.0 mm2 (p<0.001). The increase in MBA accounted for 68% of lumen gain. The frequency of vascular damage and the relative contribution of MBA increase and PLA decrease to luminal gain were not different in procedures with balloon diameter ≤ 5 mm and ≥ 6 mm.Conclusions:Vascular damage is common following PTA. Lumen gain is mainly due to vessel expansion and, to a lesser extent, to a decrease in plaque area
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
Femorodistal venous bypass evaluated with intravascular ultrasound
Objective:To evaluate the feasibility of intravascular ultrasound imaging during femorodistal venous bypass procedures to assess qualitative and quantitative parameters of the greater saphenous vein and to detect potential causes for (re)stenosis and/or occlusion.Methods:Intravascular ultrasound data obtained from 15 patients were reviewed and compared with angiographic data.Results:Intravascular ultrasound enabled differentiation between normal and thickened vein wall. Venous side-branches could be located. Intact valves could be differentiated from valves disrupted by valve cutting. Patent anastomoses could be distinguished from anastomoses with some degree of obstruction. Intravascular ultrasound imaging of the inflow and outflow tracts revealed obstructive lesions, not evidenced angiographically. Quantitative analysis revealed that the median normal vein wall thickness (tunica intima and tunica media) was 0.25 mm (range 0.17–0.40 mm). The distinct vein wall thickening encountered in three patients measured 0.82, 0.95 and 1.06 mm, respectively, and was associated with narrowing in two patients. In five of 15 patients intravascular ultrasound findings altered surgical management.Conclusion:Intravascular ultrasound is able to assess qualitative and quantitative parameters of the venous bypass and has the potential to influence surgical management based on morphologic and quantitative data