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(Arteriosclerosis, Thrombosis, and Vascular Biology. 2001;21:1618.)
© 2001 American Heart Association, Inc.

Atherosclerosis and Lipoproteins

Relationship of Clinical Presentation and Calcification of Culprit Coronary Artery Stenoses

Joshua A. Beckman; Jason Ganz; Mark A. Creager; Peter Ganz; Scott Kinlay

From the Cardiovascular Division, Brigham and Women’s Hospital, Harvard Medical School, Boston, Mass.

Correspondence to Joshua A. Beckman, MD, Cardiovascular Division, Brigham and Women’s Hospital, 75 Francis St, Boston, MA 02115. E-mail jbeckman{at}partners.org

	Abstract

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Abstract—— Coronary artery calcification is increased in the presence of atherosclerosis. However, there is great variability in the calcification of individual coronary stenoses, and the clinical significance of this finding remains unknown. We tested the hypothesis that culprit lesions associated with myocardial infarction or unstable angina are less calcified than are stenoses associated with stable angina. The study consisted of 78 patients who underwent intravascular ultrasound imaging of culprit stenoses after the placement of a stent. Seventeen patients presented with stable angina; 43, with unstable angina; and 18, with myocardial infarction. The extent of coronary calcification was measured by the angle of its arc and was quantified with a computer-based protractor. The arc of calcium was measured in the stented area at the point of maximal calcification and also as an average of the calcification found at proximal, middle, and distal stent segments. The maximal arc of calcium decreased progressively from patients with stable angina (91±10°) to those with unstable angina (59±8°) and to those with myocardial infarction (49±11°, P=0.014). Similarly, the average arc of calcium was greatest (32±7°) in patients with stable angina, less (15±4°) in patients with unstable angina, and least (10±5°) in patients with acute myocardial infarction (P=0.014). These associations remained significant after adjustment for other factors that potentially affect arterial calcification. Acute coronary syndromes are associated with a relative lack of calcium in the culprit stenoses compared with stenoses of patients with stable angina. These findings have implications for the understanding of the biology of acute coronary syndromes as well as for the identification of coronary stenoses by methods that rely solely on the presence of calcium.

Key Words: calcinosis • calcium • coronary vessels • ultrasonography, interventional • myocardial infarction

	Introduction

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Coronary artery calcification is an active process that is commonly observed in the setting of atherosclerosis.^1–3 Previous reports have found that arterial calcification is proportional to the overall burden of the atherosclerotic plaque but not necessarily to the severity of luminal narrowing.^3–7 Acute coronary syndromes, including myocardial infarction and unstable angina, arise from rupture or erosion of atherosclerotic plaques.⁴ The relationship of lesional calcium toward propensity to plaque rupture and, thus, to the pathogenesis of acute coronary syndromes remains uncertain.⁵

See editorial, page 1561

Furthermore, the association between coronary calcification and atherosclerosis has stimulated interest in using arterial calcification to detect coronary atherosclerosis. Noninvasive methods of quantifying coronary calcification, eg, electron beam CT (EBCT), have helped to define the relationship between coronary artery calcification and the atherosclerotic burden. Whether such calcium-based approaches can be useful in visualizing the most dangerous, ie, vulnerable plaques, is unknown.

In the present study, we tested the hypothesis that calcification of culprit lesions responsible is reduced for acute coronary syndromes compared with lesions associated with stable angina. Accordingly, we used intravascular ultrasound (IVUS) to assess the extent of calcification of culprit lesions in patients with stable angina, unstable angina, and myocardial infarction.

	Methods

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Patient Selection
We selected all 78 patients with de novo native lesions causing angina or myocardial infarction who underwent IVUS imaging of coronary arteries after stent placement at Brigham and Women’s Hospital between January 1997 and January 2000. At this institution, IVUS imaging is performed at the discretion of the attending interventional cardiologist to assess the adequacy of stent deployment. We excluded patients who had interventions for in-stent restenosis or for bypass graft disease. We also excluded patients who underwent directional or rotational atherectomy.

Clinical Demographics
Clinical information and laboratory results were collected from the medical record by 1 author unaware of the IVUS characteristics. Diabetes mellitus and hypertension were defined by medical treatment for these conditions. Current smoking included at least 1 cigarette per day in the previous month. The definition of unstable angina was based on the criteria of Braunwald⁶ as new onset (<2 months) of severe angina, accelerated angina, or angina at rest. Myocardial infarction was defined by requiring at least 2 of the following criteria: (1) chest discomfort typical of ischemic pain lasting for at least 30 minutes, (2) the presence of ST-segment elevations or new Q waves in 2 contiguous leads, and (3) the elevation of creatine kinase to more than twice the upper limit of our reference range obtained before catheterization. A vessel was defined as having significant atherosclerosis by the presence of a 50% stenosis. The culprit lesion was defined as the stented segment and was identified by the interventional cardiologist according to standard clinical, ECG, and noninvasive imaging and angiographic criteria.

IVUS Imaging Protocol
All IVUS studies were performed after intracoronary nitroglycerin (100 to 200 µg). One of 2 IVUS systems was used: a 30-MHz mechanical ultrasound catheter (Ultracross, Cardiovascular Imaging System) or a 25-MHz, 64-element, solid-state catheter (Visions Five-64 F/X, Endosonics). In all cases, an automated (0.5-mm/s) or slow manual pullback was recorded on high-resolution super-VHS tape for offline analysis.

Analysis of IVUS Images
Six frames from each IVUS study were grabbed from the super-VHS tape for measurement. These included 4 frames in the culprit lesion corresponding to the proximal, middle, and distal part of the stent and the frame showing the widest arc of calcification. Two reference segment frames were grabbed (a proximal and distal reference) within 10 mm of the ends of the stent and before any intervening branch.

Calcium was defined as a bright echogenic signal with an accompanying acoustic shadow in the arterial wall and was quantified in 2 ways for each patient: (1) by the widest arc of calcium found in the stented segment and (2) as the average angle of the arc of calcium in the proximal, middle, and distal stented segments. The arc of calcium was chosen as the descriptor because of the demonstrated relationship between arc of calcium defined by IVUS and pathological calcium content⁷ and because it was less likely to be changed by stenting than were other lesional components⁸ (Figure 1).

View larger version (67K): [in this window] [in a new window]   Figure 1. Intravascular images from 3 patients after coronary stenting showing the most calcified region in the culprit lesion. A, IVUS image from a patient with stable angina and an arc calcium of 116°. B, IVUS image from a patient with unstable angina and an arc of calcium of 64°. C, IVUS image from a patient with a myocardial infarction and an arc of calcium of 20°.

One author, who was unaware of the clinical data, measured the vessel, lumen, and plaque areas in the reference segments, the lumen area in the stented segment, and the angle of the arcs of calcium by using computer planimetry (TapeMeasure, INDEC Systems)^1–3,9–11 Vessel area was not reported in the stented segment because acoustic shadowing from calcium in the vessel wall partly obscured the external elastic membrane in many frames.

Statistical Analysis
All analyses compared patients presenting with myocardial infarction, unstable angina, and stable angina with the use of Stata statistical software (Statcorp). Descriptive statistics are presented as mean±SD or proportions, as appropriate. Experimental measures are presented as mean±SE. Fisher’s exact test was used to compare categorical data and regression analysis for continuous data across the 3 groups. The main hypothesis was tested by comparing the amount of culprit lesion calcium between the 3 patient groups, with stable angina patients used as the reference, and by performing an analysis of trend across increasing instability of the presenting syndrome (stable to unstable angina to myocardial infarction). Similar analyses were used to compare the risk factors between the 3 groups and to adjust the main analysis for other potential confounding variables.

	Results

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Baseline Characteristics
IVUS studies from 78 patients met the inclusion criteria for the present study. Of these, 17 patients presented with stable angina; 43, with unstable angina; and 18, with myocardial infarction. Their clinical characteristics are presented in Table 1. Among risk factors for coronary artery disease and arterial calcification, only hypertension was distributed unevenly among the 3 groups (P=0.03).

View this table: [in this window] [in a new window]   Table 1. Baseline Characteristics

Angiographic Characteristics
The angiographic characteristics are presented in Table 2. The left anterior descending coronary artery was the vessel most commonly imaged, and the left circumflex coronary artery was the least imaged vessel. The average number of vessels with a >50% stenosis did not differ significantly between groups.

View this table: [in this window] [in a new window]   Table 2. Angiographic Characteristics

Lesion Calcification
The maximal culprit lesion calcium (maximal width of the calcium arc) was greater in patients with stable angina (91±10°) than in patients with unstable angina (59±8°) and was smallest in patients with acute myocardial infarction (49±11°), as shown in Figure 2 (test of trend P=0.014). Similarly, the average angle of the arc of calcium in the culprit lesions was greater in patients with stable angina (32±7°), less in patients with unstable angina (15±4°), and least in patients with acute myocardial infarction (10±5°), as shown in Figure 3 (test of trend P=0.014). Subject age, sex, total and HDL cholesterol, diabetes, smoking, hypertension, and serum creatinine were not related to the amount of calcification by univariate or multivariate analysis.

View larger version (23K): [in this window] [in a new window]   Figure 2. Largest arc of calcium found within the culprit lesion expressed in degrees. The arc of calcium was greatest in stable angina pectoris (SAP), less in unstable angina pectoris (UAP), and least in acute myocardial infarction (AMI), with P=0.014. With a direct comparison, the arc of calcium was less in UAP than in SAP (*P=0.019) and less in AMI than in SAP (+P=0.013).

View larger version (16K): [in this window] [in a new window]   Figure 3. Average arc of calcium found within the culprit lesion expressed in degrees. The average arc of calcium was greatest in SAP, less in UAP, and least in AMI (P=0.014). With a direct comparison, the arc of calcium was less in UAP than in SAP (*P=0.013) and less in AMI than in SAP (+P=0.018).

Reference and Stented Segments
The maximal reference segment calcium was 20±32°in patients with stable angina, 25±35° in patients with unstable angina, and 4±10° in patients with acute myocardial infarction (test of trend P=NS). There were no significant relationships between the clinical presentation and vessel area, lumen area, or calcification in the reference segments.

	Discussion

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In the present study, we used IVUS to assess calcification of culprit coronary artery stenoses in patients with coronary artery disease and a range of clinical presentations. The novel finding in the present study is that culprit lesions of patients with stable angina are more extensively calcified than are those in patients with unstable angina and are least calcified in patients with myocardial infarction.

Arterial Calcification in Coronary Artery Disease
The introduction of EBCT has stimulated interest in the relationship between arterial calcification and atherosclerosis. Coronary artery calcification scores reported in several large EBCT studies of patients at varying risks of coronary artery disease suggest that, on average, calcification increases with the overall plaque burden. Detrano et al¹² demonstrated that subjects with risk factors but no ischemic symptoms had a mean calcification score of 44. In a multicenter study, symptomatic patients undergoing clinically indicated cardiac catheterization for coronary disease had a mean score of 336.¹³ Patients with angiographic evidence of left main or 3-vessel coronary disease had a mean calcium score of 491.¹⁴ These and other studies^15–17 suggest that calcification is more likely a feature of advanced obstructive coronary atherosclerosis. Increasing coronary calcinosis is likely related to an increasing burden of atherosclerosis and, therefore, implies an associated incremental risk of cardiovascular events. Nonetheless, the important findings from CT studies cannot be extrapolated to indicate that calcium, per se, contributes to the development of acute coronary syndromes.

Arterial Calcification in Acute Coronary Syndromes
Recent studies have suggested that myocardial infarction and unstable angina usually arise from the disruption of mildly stenosed atherosclerotic lesions.^18,19 For half of all patients with myocardial infarction, this event constitutes the initial clinical presentation of coronary artery disease, suggesting that severe stenoses that are likely to cause preexisting symptoms are frequently absent in this patient population.²⁰

The characteristics of plaques vulnerable to rupture and thereby likely to cause acute coronary syndromes have been elucidated in postmortem studies.^4,21,22 These studies have confirmed the angiographic observations that the mild stenoses are more frequently disrupted. Such vulnerable plaques typically contain a large amount of lipid and have a preponderance of inflammatory cells at the shoulders of the plaque and a thin fibrous cap. The large lipid core is soft and bears the circumferential stresses less well than fibrous components of the arterial wall.^21,23,24 Calcium is found infrequently in the culprit lesions of ruptured plaques.²³ In contrast to the destabilizing effects of the lipid core, it has been demonstrated theoretically by Huang et al,²⁵ who used large-strain finite-element analysis, that calcium is a stabilizing force, similar to the fibrous plaque.²⁵ Because only a minority of myocardial infarcts are fatal and even fewer are subject to postmortem examination, it is not clear whether inferences derived by postmortem examination apply to the general population of patients with coronary atherosclerosis.

Detection of Coronary Calcium by Noninvasive Approaches in Patients With Anginal Syndromes
Studies using double-helical CT support the observation that coronary arteries containing stable stenoses are more heavily calcified than are those containing unstable plaques. Shemesh et al²⁶ demonstrated that patients with stable angina had higher calcium scores than did patients with acute myocardial infarction and that the infarct-related arteries tended to have less calcium than did the other coronary arteries. Interestingly, African Americans with similar coronary risk factor profiles had less coronary artery calcification yet more coronary events than did white subjects.²⁷ IVUS extends these findings by focusing on the calcification of a single culprit stenosis and associating culprit lesion calcification with clinical stability.

Findings in the Present Study
We used IVUS because it is accepted as the most sensitive method for the detection of arterial wall calcium in vivo.^1,7,28–31 IVUS methods of quantifying arterial calcium rely on measuring the arc of calcium because the acoustic shadowing prohibits any measurement of the area of calcification. The ability of this approach to quantify the amount of calcium was confirmed by careful histological correlation.⁷ Although there are likely many factors that contribute to plaque rupture, the difference in average calcium allows us to study the effect of the variable of interest (calcium).

Calcium is more prevalent in older individuals and in some studies is more prevalent in patients with hypertension.³² We found no relationship between calcium and these variables in the present study. However, most of our subjects were older, and a wider age range may be required to find this relationship. Because there were more hypertensive individuals among our subjects with unstable angina, any effect of hypertension would have only underestimated the difference with stable angina. Finally, the vessel causing the intervention was most commonly the left anterior descending coronary artery, yet the extent of coronary artery disease was similar among the 3 groups. Adjustment for these and other factors did not change the results of the present study.

Implications
Calcium is stiffer than the surrounding components of atherosclerotic plaques. Potentially, it can concentrate stresses and serve as a nidus for plaque disruption.³³ Nevertheless, histological studies of postmortem specimens have demonstrated that intimal tears localized to the junction of calcium with adjacent fibrous tissue are infrequent and observed in only 4% of all disrupted lesions.²³ Furthermore, a recent publication by Huang et al²⁵ provides mechanistic insight by demonstrating that the lipid core is a destabilizing force, whereas calcium provides the stability of the fibrous cap. Our results, derived from a broad range of patients undergoing coronary intervention, support the concept that calcium is not a critical substrate for plaque disruption and is, in fact, associated with more stable plaques.

Interestingly, some have postulated that calcium in adjacent sections may create a rigid arterial segment and decrease arterial flexibility, creating a nidus for plaque rupture in culprit lesions.²⁴ Our data indicate that calcium in adjacent segments is not related to clinical presentation or the calcium extent of the culprit lesion. Thus, it seems that only calcium found in a specified lesion conveys information specific to clinical presentation.

Limitations of the Study
We have excluded patients who underwent rotational and directional atherectomy because those procedures remove tissue along with calcium. Inasmuch as rotational atherectomy (majority of excluded patients) is usually performed because of extensive lesional calcium and is typically confined to patients with stable angina, the findings of the present study would have only been strengthened had these patients not been excluded.

Patients at our institution do not regularly undergo IVUS examination, and these patients may not be an exact representation of the whole; however, the patients in the present study were similar in age, sex ratio, and indication for intervention as the entire population of patients undergoing intervention at our hospital.

Conclusions
In summary, we found that acute coronary syndromes are associated with a relative lack of calcium in the culprit stenoses compared with stenoses of patients with stable angina. These findings have implications for the understanding of the biology of acute coronary syndromes as well as for the identification of coronary stenoses by methods that rely on the presence of calcium.

Received April 20, 2001; accepted July 3, 2001.

	References

Top Abstract Introduction Methods Results Discussion References

 

1. Tobis JM, Mallery J, Mahon D, Lehmann K, Zalesky P, Griffith J, Gessert J, Moriuchi M, McRae M, Dwyer ML, et al. Intravascular ultrasound imaging of human coronary arteries in vivo: analysis of tissue characterizations with comparison to in vitro histological specimens. Circulation. 1991; 83: 913–926.[Abstract/Free Full Text]
2. Nishimura RA, Edwards WD, Warnes CA, Reeder GS, Holmes DR Jr, Tajik AJ, Yock PG. Intravascular ultrasound imaging: in vitro validation and pathologic correlation. J Am Coll Cardiol. 1990; 16: 145–154.[Abstract]
3. Potkin BN, Bartorelli AL, Gessert JM, Neville RF, Almagor Y, Roberts WC, Leon MB. Coronary artery imaging with intravascular high-frequency ultrasound. Circulation. 1990; 81: 1575–1585.[Abstract/Free Full Text]
4. Libby P. Molecular bases of the acute coronary syndromes. Circulation. 1995; 91: 2844–2850.[Free Full Text]
5. Taylor AJ, Burke AP, O’Malley PG, Farb A, Malcom GT, Smialek J, Virmani R. A comparison of the Framingham risk index, coronary artery calcification, and culprit plaque morphology in sudden cardiac death. Circulation. 2000; 101: 1243–1248.[Abstract/Free Full Text]
6. Braunwald E. Unstable angina: a classification. Circulation. 1989; 80: 410–414.[Free Full Text]
7. Kostamaa H, Donovan J, Kasaoka S, Tobis J, Fitzpatrick L. Calcified plaque cross-sectional area in human arteries: correlation between intravascular ultrasound and undecalcified histology. Am Heart J. 1999; 137: 482–488.[Medline] [Order article via Infotrieve]
8. Albrecht D, Kaspers S, Fussl R, Hopp HW, Sechtem U. Coronary plaque morphology affects stent deployment: assessment by intracoronary ultrasound. Cathet Cardiovasc Diagn. 1996; 38: 229–235.[Medline] [Order article via Infotrieve]
9. Anderson TJ, Meredith IT, Uehata A, Mudge GH, Selwyn AP, Ganz P, Yeung AC. Functional significance of intimal thickening as detected by intravascular ultrasound early and late after cardiac transplantation. Circulation. 1993; 88: 1093–1100.[Abstract/Free Full Text]
10. Davis SF, Yeung AC, Meredith IT, Charbonneau F, Ganz P, Selwyn AP, Anderson TJ. Early endothelial dysfunction predicts the development of transplant coronary artery disease at 1 year posttransplant. Circulation. 1996; 93: 457–462.[Abstract/Free Full Text]
11. Yeung AC, Davis SF, Hauptman PJ, Kobashigawa JA, Miller LW, Valantine HA, Ventura HO, Wiedermann J, Wilensky R. Incidence and progression of transplant coronary artery disease over 1 year: results of a multicenter trial with use of intravascular ultrasound: Multicenter Intravascular Ultrasound Transplant Study Group. J Heart Lung Transplant. 1995; 14: S215–S220.[Medline] [Order article via Infotrieve]
12. Detrano RC, Wong ND, Doherty TM, Shavelle RM, Tang W, Ginzton LE, Budoff MJ, Narahara KA. Coronary calcium does not accurately predict near-term future coronary events in high-risk adults. Circulation. 1999; 99: 2633–2638.[Abstract/Free Full Text]
13. Detrano R, Hsiai T, Wang S, Puentes G, Fallavollita J, Shields P, Stanford W, Wolfkiel C, Georgiou D, Budoff M, et al. Prognostic value of coronary calcification and angiographic stenoses in patients undergoing coronary angiography. J Am Coll Cardiol. 1996; 27: 285–290.[Abstract]
14. Schmermund A, Denktas AE, Rumberger JA, Christian TF, Sheedy PFII, Bailey KR, Schwartz RS. Independent and incremental value of coronary artery calcium for predicting the extent of angiographic coronary artery disease: comparison with cardiac risk factors and radionuclide perfusion imaging. J Am Coll Cardiol. 1999; 34: 777–786.[Abstract/Free Full Text]
15. Arad Y, Spadaro LA, Goodman K, Lledo-Perez A, Sherman S, Lerner G, Guerci AD. Predictive value of electron beam computed tomography of the coronary arteries: 19-month follow-up of 1173 asymptomatic subjects. Circulation. 1996; 93: 1951–1953.[Abstract/Free Full Text]
16. He ZX, Hedrick TD, Pratt CM, Verani MS, Aquino V, Roberts R, Mahmarian JJ. Severity of coronary artery calcification by electron beam computed tomography predicts silent myocardial ischemia. Circulation. 2000; 101: 244–251.[Abstract/Free Full Text]
17. Rumberger JA, Simons B, Fitzpatrick LA, Sheedy PF, Schwartz RS. Coronary artery calcium area by electron-beam computed tomography and coronary atherosclerotic plaque area. Circulation. 1995; 92: 2157–2162.[Abstract/Free Full Text]
18. Ambrose JA, Tannenbaum MA, Alexopoulos D, Hjemdahl-Monsen CE, Leavy J, Weiss M, Borrico S, Gorlin R, Fuster V. Angiographic progression of coronary artery disease and the development of myocardial infarction. J Am Coll Cardiol. 1988; 12: 56–62.[Abstract]
19. Hackett D, Davies G, Maseri A. Pre-existing coronary stenoses in patients with first myocardial infarction are not necessarily severe. Eur Heart J. 1988; 9: 1317–1323.[Abstract/Free Full Text]
20. Tunstall-Pedoe H, Morrison C, Woodward M, Fitzpatrick B, Watt G. Sex differences in myocardial infarction and coronary deaths in the Scottish MONICA population of Glasgow 1985 to 1991: presentation, diagnosis, treatment, and 28-day case fatality of 3991 events in men and 1551 events in women. Circulation. 1996; 93: 1981–1992.[Abstract/Free Full Text]
21. Mann JM, Davies MJ. Vulnerable plaque: relation of characteristics to degree of stenosis in human coronary arteries. Circulation. 1996; 94: 928–931.[Abstract/Free Full Text]
22. Falk E. Plaque rupture with severe pre-existing stenosis precipitating coronary thrombosis: characteristics of coronary atherosclerotic plaques underlying fatal occlusive thrombi. Br Heart J. 1983; 50: 127–134.[Abstract/Free Full Text]
23. Richardson PD, Davies MJ, Born GV. Influence of plaque configuration and stress distribution on fissuring of coronary atherosclerotic plaques. Lancet. 1989; 2: 941–944.[Medline] [Order article via Infotrieve]
24. Cheng GC, Loree HM, Kamm RD, Fishbein MC, Lee RT. Distribution of circumferential stress in ruptured and stable atherosclerotic lesions: a structural analysis with histopathological correlation. Circulation. 1993; 87: 1179–1187.[Abstract/Free Full Text]
25. Huang H, Virmani R, Younis H, Burke AP, Kamm RD, Lee RT. The impact of calcification on the biomechanical stability of atherosclerotic plaques. Circulation. 2001; 103: 1051–1056.[Abstract/Free Full Text]
26. Shemesh J, Stroh CI, Tenenbaum A, Hod H, Boyko V, Fisman EZ, Motro M. Comparison of coronary calcium in stable angina pectoris and in first acute myocardial infarction utilizing double helical computerized tomography. Am J Cardiol. 1998; 81: 271–275.[Medline] [Order article via Infotrieve]
27. Doherty TM, Tang W, Detrano RC. Racial differences in the significance of coronary calcium in asymptomatic black and white subjects with coronary risk factors. J Am Coll Cardiol. 1999; 34: 787–794.[Abstract/Free Full Text]
28. Mintz GS, Nissen SE, Anderson WD, Bailey SR, Erbel R, Fitzgerald PJ, Pinto FJ, Rosenfield K, Siegel RJ, Tuzcu EM, et al. American College of Cardiology Clinical Expert Consensus Document on Standards for Acquisition, Measurement, and Reporting of Intravascular Ultrasound Studies (IVUS). J Am Coll Cardiol. 2001; 37: 1478–1492.[Free Full Text]
29. Nissen SE, Yock P. Intravascular ultrasound: novel pathophysiological insights and current clinical applications. Circulation. 2001; 103: 604–616.[Abstract/Free Full Text]
30. Hausmann D, Lundkvist AJ, Friedrich GJ, Mullen WL, Fitzgerald PJ, Yock PG. Intracoronary ultrasound imaging: intraobserver and interobserver variability of morphometric measurements. Am Heart J. 1994; 128: 674–680.[Medline] [Order article via Infotrieve]
31. Hiro T, Leung CY, De Guzman S, Caiozzo VJ, Farvid AR, Karimi H, Helfant RH, Tobis JM. Are soft echoes really soft?: intravascular ultrasound assessment of mechanical properties in human atherosclerotic tissue. Am Heart J. 1997; 133: 1–7.[Medline] [Order article via Infotrieve]
32. Megnien JL, Simon A, Lemariey M, Plainfosse MC, Levenson J. Hypertension promotes coronary calcium deposit in asymptomatic men. Hypertension. 1996; 27: 949–954.[Abstract/Free Full Text]
33. Lee RT, Grodzinsky AJ, Frank EH, Kamm RD, Schoen FJ. Structure-dependent dynamic mechanical behavior of fibrous caps from human atherosclerotic plaques. Circulation. 1991; 83: 1764–1770.[Abstract/Free Full Text]

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				A. N. DeMaria, J. Narula, E. Mahmud, and S. Tsimikas Imaging vulnerable plaque by ultrasound. J. Am. Coll. Cardiol., April 18, 2006; 47(8 Suppl): C32 - C39. [Abstract] [Full Text] [PDF]

				J. H. Ix, M. G. Shlipak, V. M. Brandenburg, S. Ali, M. Ketteler, and M. A. Whooley Association Between Human Fetuin-A and the Metabolic Syndrome: Data From the Heart and Soul Study Circulation, April 11, 2006; 113(14): 1760 - 1767. [Abstract] [Full Text] [PDF]

				R. D. Brook, R. L. Bard, S. Patel, M. Rubenfire, N. S. Clarke, E. A. Kazerooni, T. W. Wakefield, P. K. Henke, and K. A. Eagle A Negative Carotid Plaque Area Test Is Superior to Other Noninvasive Atherosclerosis Studies for Reducing the Likelihood of Having Underlying Significant Coronary Artery Disease Arterioscler. Thromb. Vasc. Biol., March 1, 2006; 26(3): 656 - 662. [Abstract] [Full Text] [PDF]

				E. Larose, Y. Yeghiazarians, P. Libby, E.K. Yucel, M. Aikawa, D. F. Kacher, E. Aikawa, S. Kinlay, F. J. Schoen, A. P. Selwyn, et al. Characterization of Human Atherosclerotic Plaques by Intravascular Magnetic Resonance Imaging Circulation, October 11, 2005; 112(15): 2324 - 2331. [Abstract] [Full Text] [PDF]

				M. Fornage, C. R. Lee, P. A. Doris, M. S. Bray, G. Heiss, D. C. Zeldin, and E. Boerwinkle The soluble epoxide hydrolase gene harbors sequence variation associated with susceptibility to and protection from incident ischemic stroke Hum. Mol. Genet., October 1, 2005; 14(19): 2829 - 2837. [Abstract] [Full Text] [PDF]

				C. L. Higgins, S. A. Marvel, and J. D. Morrisett Quantification of Calcification in Atherosclerotic Lesions Arterioscler. Thromb. Vasc. Biol., August 1, 2005; 25(8): 1567 - 1576. [Abstract] [Full Text] [PDF]

				S. Ehara, Y. Kobayashi, M. Yoshiyama, K. Shimada, Y. Shimada, D. Fukuda, Y. Nakamura, H. Yamashita, H. Yamagishi, K. Takeuchi, et al. Spotty Calcification Typifies the Culprit Plaque in Patients With Acute Myocardial Infarction: An Intravascular Ultrasound Study Circulation, November 30, 2004; 110(22): 3424 - 3429. [Abstract] [Full Text] [PDF]

				J. Shemesh, N. Koren-Morag, S. Apter, J. Rozenman, B. A. Kirwan, Y. Itzchak, and M. Motro Accelerated Progression of Coronary Calcification: Four-year Follow-up in Patients with Stable Coronary Artery Disease Radiology, October 1, 2004; 233(1): 201 - 209. [Abstract] [Full Text] [PDF]

				U. J. Schoepf, C. R. Becker, B. M. Ohnesorge, and E. K. Yucel CT of Coronary Artery Disease Radiology, July 1, 2004; 232(1): 18 - 37. [Abstract] [Full Text] [PDF]

				M. Abedin, Y. Tintut, and L. L. Demer Vascular Calcification: Mechanisms and Clinical Ramifications Arterioscler. Thromb. Vasc. Biol., July 1, 2004; 24(7): 1161 - 1170. [Abstract] [Full Text] [PDF]

				J. Golledge, M. McCann, S. Mangan, A. Lam, and M. Karan Osteoprotegerin and Osteopontin Are Expressed at High Concentrations Within Symptomatic Carotid Atherosclerosis Stroke, July 1, 2004; 35(7): 1636 - 1641. [Abstract] [Full Text] [PDF]

				B. D. MacNeill, H. C. Lowe, M. Takano, V. Fuster, and I.-K. Jang Intravascular Modalities for Detection of Vulnerable Plaque: Current Status Arterioscler. Thromb. Vasc. Biol., August 1, 2003; 23(8): 1333 - 1342. [Abstract] [Full Text] [PDF]

				S. Mohlenkamp, N. Lehmann, A. Schmermund, H. Pump, S. Moebus, D. Baumgart, R. Seibel, D. H.W Gronemeyer, K.-H. Jockel, and R. Erbel Prognostic value of extensive coronary calcium quantities in symptomatic males--a 5-year follow-up study Eur. Heart J., May 1, 2003; 24(9): 845 - 854. [Abstract] [Full Text] [PDF]

				J. Shemesh, S. Apter, Y. Itzchak, and M. Motro Coronary Calcification Compared in Patients with Acute versus in Those with Chronic Coronary Events by Using Dual-Sector Spiral CT Radiology, February 1, 2003; 226(2): 483 - 488. [Abstract] [Full Text] [PDF]

				G. J. Blake and P. M. Ridker C-Reactive Protein, Subclinical Atherosclerosis, and Risk of Cardiovascular Events Arterioscler. Thromb. Vasc. Biol., October 1, 2002; 22(10): 1512 - 1513. [Full Text] [PDF]

E. Mohler III Vascular calcification: good, bad or ugly? Vascular Medicine, August 1, 2002; 7(3): 161 - 162.