Development of coronary compensatory enlargement in vivo: sequential assessments with intravascular ultrasound

Potential quantitative magnetic resonance imaging biomarkers of coronary remodeling in older hypertensive patients

OBJECTIVE

To detect differences in potential magnetic resonance imaging biomarkers of coronary remodeling between older hypertensive patients and healthy controls.

METHODS AND RESULTS

Two-dimensional black-blood coronary wall magnetic resonance imaging and 3-dimensional whole-heart coronary magnetic resonance angiography were performed on 130 participants (65-84 years), including 65 hypertensive patients and 65 healthy controls. Coronary segments derived from hypertensive participants had a higher mean coronary wall thickness, a smaller vessel area, a smaller coronary wall area, a smaller lumen area, a lower coronary distensibility index, and a higher percent of the coronary wall occupying the vessel area (PWOV) than those from healthy controls. When the average PWOV was set as an ad hoc cutoff point, coronary segments with a high PWOV had a significantly higher mean wall thickness, a higher maximum wall thickness, a smaller vessel area, a smaller lumen area, a lower coronary distensibility index, and a higher coronary plaque index compared with coronary segments with a low PWOV.

CONCLUSIONS

Magnetic resonance techniques are able to noninvasively detect significant differences in potential imaging biomarkers of coronary remodeling between older hypertensive patients and healthy controls. The PWOV is a promising remodeling feature for quantitatively evaluating the progression of coronary atherosclerosis.

Brachial artery diameter measurement: a tool to simplify non-invasive vascular assessment

AIM

The mechanisms of vascular remodeling have attracted great interest since it is a phenomenon related to cardiovascular diseases. We would like to examine studies that contributed to clarify the remodeling mechanisms, to explore the different faces of atherosclerosis process.

DATA SYNTHESIS

A number of invasive and non-invasive vascular assessment methods were developed, to detect the early sign of atherosclerosis. It became clear that the invasive tests were not applicable to large-scale studies. Consequently, a non-invasive test was developed. Studies showed that the endothelial function evaluation is a predictor of future cardiac events in individuals at cardiovascular risk and in those with established disease. However, analyzing several works, an interesting concept emerged, i.e., the inverse relation between endothelium-dependent dilation and vessel size, since large vessel tend not to dilate significantly. This notion emphasized the role of basal diameter on vascular response. In particular, as brachial artery diameter is the measure on which FMD is based, it could add more information in clinical evaluation, simplifying the assessment. Several studies showed that morphological change of brachial artery is a better indicator of the extent of coronary disease rather than FMD. Other studies showed that brachial diameter has predictive significance in the stratification of cardiovascular risk.

CONCLUSION

Brachial diameter is a useful and simple tool. It should be incorporated into the overall assessment of cardiovascular risk but further studies are warranted to determine the final place of brachial diameter assessment in routine clinical setting.

An intravascular ultrasound analysis in women experiencing chest pain in the absence of obstructive coronary artery disease: a substudy from the National Heart, Lung and Blood Institute-Sponsored Women's Ischemia Syndrome Evaluation (WISE)

AIMS

Using intravascular ultrasound (IVUS), we sought to characterize coronary morphology in women with chest pain without major epicardial obstructive coronary artery disease (CAD). We have previously observed an unexpectedly high rate of adverse outcomes among women with chest pain and normal or insignificant obstructive CAD. Information about the presence and characteristics of coronary atherosclerosis in these women could provide insight into the mechanisms related to increased risk, as well as improved diagnosis, prevention, and treatment.

METHODS

Women (n = 100) with suspected ischemia without obstructive CAD (>50% stenosis) underwent IVUS of a left coronary segment with measurements by a core lab masked to clinical and angiographic findings.

RESULTS

Angiograhic core lab analysis found 69.6% of patients had no (≤20%) and 30.4% had minimal (20-<50%) CAD. IVUS segmental images were interpretable by the core lab in 92 women, with 19 (21%) having no atherosclerosis (intimal-medial thickness <0.5 mm). In the remaining 73 women (79%), percent atheroma volume was 27 ± 8% and mean maximum plaque thickness was 0.53 ± 0.22 mm. Thirty-eight women with atherosclerosis (53%) had ≥30% of interrogated vessel involved. The average vessel involvement was 40%, and the maximum plaque thickness was 1.27 mm. The number of risk factors strongly correlated with percent atheroma volume (r = 0.53, P < 0.0001) and percent vessel involvement (r = 0.51, P < 0.0001), with the strongest independent predictor of both being age. Remodeling was assessed in 59/73 women (81%), and 73% had evidence of positive remodeling.

CONCLUSIONS

In symptomatic women without significant luminal obstructive CAD, we observed a high prevalence of atherosclerosis with positive remodeling and preserved lumen size. These findings may help explain increased risk and emphasize need for improved diagnostic and treatment options for women with concealed CAD.

Intravascular ultrasound imaging of myocardial-infarction-related arteries after percutaneous transluminal coronary angioplasty reveals significant plaque burden and compensatory enlargement

We studied patients with acute myocardial infarction (MI) by intravascular ultrasound (IVUS) to elucidate the controversy as to the amount and severity of the atherosclerotic disease at the culprit lesion site in acute MI, as discrepancies exist between angiographic and pathological reports. Twenty-five consecutive patients (age 56 3 10.5 years), with acute MI, underwent IVUS study of the MI-related artery immediately following successful PTCA to the culprit lesion. The IVUS images were analyzed quantitatively and qualitatively and were compared with the angiography of the same arteries. At the PTCA site, 64% of the lesions had an area stenosis of 50-70% and the plaque cross-sectional area (CSA) averaged 0.5 3 0.18 of the arterial CSA. IVUS-defined atherosclerosis was found also in 72% of the segments proximal and distal to the culprit lesion with a plaque/artery CSA ratio of 0.25 3 0.2. The angiogram revealed only 30% of these segments to be abnormal (P 3 0.001). Sixty-nine per cent of all the plaques were defined as 'soft' (low echo-genecity) versus 31% 'hard' (high echo-genecity). The hard plaques were larger than the soft plaques (0.5 3 1.6 versus 0.37 3 0.19 CSA index, respectively, P 3 0.01). With the increase in plaque area there was a significant increase in arterial cross-sectional area. This was demonstrated for all the diseased segments with a correlation coefficient of 0.49 (P 3 0.0001) and for the diseased reference sites a similar correlation coefficient of 0.49 (P 3 0.003) was found. Contrary to coronary angiographic-based reports, this IVUS study revealed a significant atheromatous plaque burden at the culprit lesion of MI-related arteries as well as diffuse atherosclerosis in the reference segments proximal and distal to the lesion. The detection of compensatory enlargement may explain the discrepancies between the histopathological and the angiographic studies.

Three-dimensional reconstruction of the coronary artery wall by image fusion of intravascular ultrasound and bi-plane angiography

BACKGROUND

Intravascular ultrasound (IVUS) is becoming increasingly accepted for assessing coronary anatomy. However, its utility in visualizing and quantifying coronary morphology has been limited by its 2D tomographic nature. This study presents a 3D reconstruction technique that accurately preserves 3D geometric information.

METHODS AND RESULTS

Images obtained from manual IVUS pullbacks and continuous bi-plane angiography were fused, using angiography to reconstruct the transducer trajectory and aid in solving for the correct rotational orientation. A novel 3D active surface method automatically identified the luminal and medial-adventitial borders which, when superimposed on the transducer trajectory, could be surface-rendered for visualization and morphometry. Segmentation agreed well with manual assessment, and 3D luminal shape matched that of angiography when projected to 2D.

CONCLUSIONS

We conclude that this method provides an accurate reconstruction of the vessel's anatomy, which accounts for the true curvature of the vessel.

Role of beta1 and beta3 integrins in human smooth muscle cell adhesion to and contraction of fibrin clots in vitro

The degree of lumen narrowing in advanced lesions correlates poorly with the amount of intimal mass accumulated in the atherosclerotic plaque. As an alternate mechanism of stenosis, we propose that human smooth muscle cells bind to fibrin deposited in the matrix and exert contractile forces to cause a narrowing of the lumen. In the present study we demonstrated in vitro that human newborn aortic smooth muscle cell lines can contract and adhere to fibrin clots composed of either fibronectin-depleted plasma ("plasma") or recombinant fibrin. By using neutralizing antibodies and RGD peptides, we showed that members of the integrin family mediated the interaction between human newborn smooth muscle cells and fibrin. Neutralizing antibodies against the integrin alphavbeta3 (c7E3 Fab and LM609) did not inhibit either plasma clot contraction or recombinant fibrin clot contraction by human newborn smooth muscle cells. In contrast, antibodies against alpha5, beta1, and alpha5/beta1 inhibited contraction of clots composed of either plasma or recombinant fibrin. Anti-alphavbeta3, anti-alphav, anti-alpha5, anti-beta1, and anti-alpha5beta1 antibodies inhibited human newborn smooth muscle cell adhesion to plasma clots; however, only anti-alpha5, anti-beta1, and anti-alpha5beta1 antibodies significantly inhibited adhesion to recombinant fibrin. While the linear RGD peptides had no effect, the cyclic peptide penRGD inhibited adhesion to plasma clots and recombinant fibrin. However, it did not block contraction of recombinant fibrin clots. These results suggest that during the interaction of human newborn smooth muscle cell lines with fibrin, alpha5beta1 plays a significant role. This interaction is of potential interest as a target for efforts to block vascular contraction.

Compensatory enlargement, remodeling, and restenosis

Coronary atherosclerosis is associated with vessel remodeling and dilatation. Quantitative analysis of arterial morphometry documents that as the cross sectional area of the plaque increases within a diseased vessel segment, the outer wall of the artery expands in an attempt to compensate for the accumulation of plaque. This focal compensatory enlargement maintains cross sectional area at stenotic sites of arteries, and the angiographic appearance of the vessel may be normal, despite marked accumulation of atherosclerotic plaque. Compensatory enlargement may develop as a response to increased shear stress caused by atherosclerotic plaque in conjunction with endothelial dependent factors, or alternatively, due to medial attenuation with loss of underlying structural support. The mechanism of arterial remodeling plays an important role in the development of arterial restenosis late after balloon dilatation or other interventional modalities. Stents prevent the remodeling process and restenosis with stents is the result of a relatively uniform neointimal tissue proliferation throughout the stent. Endovascular stents induce tissue proliferation both within the endoluminal stent surface and in the tissue layers surrounding the metallic Palmaz-Schatz stent struts. The therapeutic goals to prevent restenosis have to be oriented towards prevention of acute recoil, reduction of intimal, medial and adventitial prolific response and the phenomenon of inadequate arterial remodeling.

Remodeling of atherosclerotic coronary arteries assessed with intravascular ultrasound in vitro

This study investigated remodeling in human coronary arteries with intravascular ultrasound. We conclude that regression analysis performed by Glagov et al and adopted by others is reproducible but is unable to discern shrinkage of the vessel area.