Junbo Ge

Update on Myocardial Bridging

Muscle overlying the intramyocardial segment of an epicardial coronary artery, first mentioned by Reyman1 in 1737, is termed a myocardial bridge, and the artery coursing within the myocardium is called a tunneled artery (Figure 1). It is characterized by systolic compression of the tunneled segment, which remains clinically silent in the vast majority of cases. An in-depth analysis of autopsy samples was first presented by Geiringer et al2 in 1951, but clinical interest and systematic research was triggered by an observed association of myocardial bridging with myocardial ischemia.2–5 Figure 1. Typical systolic compression (arrows) of the mid LAD at two sites in series. Diastolic lumen dimensions are normal. The coronary tree shows no angiographic signs of coronary atherosclerosis. New imaging techniques have led to improved identification and functional quantitation of myocardial bridging in vivo, which is crucial for establishing a link between systolic compression and the clinical presentation, and hence for commencing appropriate therapy. In the present article, we summarize clinically relevant aspects of myocardial bridging with an emphasis on morphological and hemodynamic alterations and their representation in imaging techniques. The prevalence varies substantially among studies with a much higher rate at autopsy versus angiography (Table).2,4–28 Variation at autopsy may in part be attributable to the care taken at preparation and the selection of hearts. Polacek, who included myocardial loops, reports the highest rate with bridges or loops in 86% of cases.29 On average, myocardial bridges are present in about one third of adults. View this table: Prevalence of Myocardial Bridging at Autopsy and Angiography The rate of angiographic bridging is <5%, attributable to thin bridges causing little compression. In subjects with angiographically normal coronary arteries, the use of provocation tests may enhance systolic myocardial compression and thereby reveal myocardial bridges in ≤40% of cases.26,30 A …

Comparison of Electron Beam Computed Tomography With Intracoronary Ultrasound and Coronary Angiography for Detection of Coronary Atherosclerosis

OBJECTIVES This analysis compared the results of electron beam computed tomography (EBCT) with those of coronary angiography and intracoronary ultrasound (ICUS) for the in vivo detection of coronary atherosclerotic plaques. BACKGROUND EBCT is a new imaging modality for identification of coronary calcifications. Coronary angiography depicts advanced changes in coronary morphology, whereas ICUS is an established diagnostic tool that detects the early stages of coronary artery disease. METHODS In 57 patients (54 +/- 9 years old), 267 coronary segments were analyzed with EBCT (3-mm slices, acquisition time 100 ms, threshold definition of coronary calcification at 130 Hounsfield units in an area > or = 1 mm2, Agatston calcium score), coronary angiography and ICUS. The analysis was based on the number and extent of coronary calcifications on EBCT, coronary lumen reduction on coronary angiography and plaque formation with and without ultrasound signs of calcifications on ICUS. RESULTS Compared with coronary angiography, EBCT yielded a sensitivity of 66%, a specificity of 78%, a positive predictive value of 39% and a negative predictive value of 91%. Compared with ICUS, EBCT yielded an overall sensitivity of 66%, a specificity of 88% and an overall accuracy of 81%. For plaques with and without ultrasound signs of calcifications, the sensitivity of EBCT was 97% and 47%, specificity 80% and 75% and overall accuracy 82% and 69%, respectively. CONCLUSIONS This in vivo correlation between ICUS and EBCT demonstrates that EBCT is a noninvasive method that helps to visualize the atherosclerotic process by localization and quantification of coronary artery calcifications. EBCT detects calcified plaques with high accuracy. Plaques without ultrasound signs of calcifications can be detected by EBCT but with lower sensitivity but equivalent specificity.

Plaque Distribution and Vascular Remodeling of Ruptured and Nonruptured Coronary Plaques in the Same Vessel: An Intravascular Ultrasound Study In Vivo

OBJECTIVES This study was designed to identify potential differences between the intravascular ultrasound (IVUS) characteristics of spontaneously ruptured and nonruptured coronary plaques. BACKGROUND The identification of vulnerable plaques in vivo may allow targeted prevention of acute coronary events and more effective evaluation of novel therapeutic approaches. METHODS Intravascular ultrasound was used to identify 29 ruptured plaques in arteries containing another nonruptured plaque in an adjacent segment. Intravascular ultrasound characteristics of these plaques were compared with plaques of computer-matched controls without evidence of plaque rupture. Plaque distribution was assessed by measuring the eccentricity of lumen location (inside the total vessel). Lumen cross-sectional area narrowing was calculated as [1 - (target/reference lumen area)] x 100%. A remodeling index was calculated as lesion/reference arterial area (>1.05 = compensatory enlargement, <0.95 = shrinkage). RESULTS Among the three groups of plaques, there was no significant difference in quantitative angiographic parameters, IVUS reference dimensions and IVUS lumen cross-sectional area narrowing. There was a difference in plaque distribution; lumen location by IVUS was significantly more eccentric in ruptured than in nonruptured (p = 0.002) and control plaques (p < 0.0001). The arc of disease-free vessel wall was larger in ruptured than in control plaques (p < 0.0001). The remodeling pattern of ruptured and nonruptured plaques differed significantly from that of the control plaques (p = 0.0001 and 0.003); compensatory enlargement was found in 66%, 48%, and 17%, whereas shrinkage was found in 7%, 10% and 48%, respectively. CONCLUSIONS Intravascular ultrasound assessment of plaque distribution and vascular remodeling may help to classify plaques with the highest probability of spontaneous rupture.

Coronary Artery Calcium in Acute Coronary Syndromes A Comparative Study of Electron-Beam Computed Tomography, Coronary Angiography, and Intracoronary Ultrasound in Survivors of Acute Myocardial Infarction and Unstable Angina

BACKGROUND Quantification of coronary artery calcified plaques by electron-beam CT (EBCT) may predict cardiovascular events. However, whereas advanced coronary atherosclerotic plaques can be identified, mildly stenotic lipid-rich (soft) plaques may be difficult to detect. The value of EBCT in a subgroup of patients has therefore been questioned. To investigate this, we evaluated patients with acute coronary syndromes by EBCT and compared the results with coronary angiography and, in patients with an indeterminate angiogram, intracoronary ultrasound (ICUS). METHODS AND RESULTS EBCT was performed in 118 consecutive patients (57+/-11 years of age) with previous myocardial infarction (n=101) or unstable angina (n=17). A standard protocol requiring a CT density >130 Hounsfield units in an area > or =1.03 mm2 was used for the definition of coronary artery calcium. We found that 110 patients had moderate to severe coronary artery disease by coronary angiography, and 8 had either mildly stenotic plaques at a single site (4 patients, confirmed by ICUS) or nonatherosclerotic causes of the unstable coronary syndrome (4 patients). One hundred and five of the 110 patients (96%) with moderate to severe angiographic disease but only 1 of the 8 other patients (13%) had a positive EBCT. Patients with acute coronary syndromes and negative EBCTs were significantly younger than patients with positive EBCTs (46+/-12 versus 58+/-10 years, P<.001), and a higher percentage was actively smoking (100% of the smokers versus 46%, P<.05). CONCLUSIONS The vast majority of patients with acute coronary syndromes and at least moderate angiographic disease have identifiable coronary calcium by EBCT. Those patients with negative EBCTs have minimal or no atherosclerotic plaque formation. They are younger and tend to be active cigarette smokers.

Extent of atherosclerosis and remodeling of the left main coronary artery determined by intravascular ultrasound

This study used intravascular ultrasound (IU) to assess the incidence and extent of left main coronary artery (LMCA) disease and the effects of arterial remodeling. Sixty-nine patients undergoing cardiac catheterization were imaged with a 20 MHz rotational-tip IU device. Nine of the 69 studies (13%) could not be analyzed because of technical (n = 2) or anatomic (n = 7) reasons. Of the remaining 60 patients, 38 (63%) had at least 1 lesion in the left coronary artery perfusion territory by angiography; significant LMCA stenosis was present in 2 patients (3%). Intravascular ultrasonography demonstrated plaques in 27 of 60 LMCAs (45%), 6 of them in patients with normal angiograms. Twenty-four plaques (89%) were eccentric and calcium was present in 4 (15%). The mean minimal lumen diameter was 4.9 +/- 0.8 mm, the maximal lumen diameter was 5.6 +/- 0.8 mm, the planimetered lumen area was 22.6 +/- 6.0 mm2, the plaque area was 3.9 +/- 5.8 mm2, the vessel area was 26.5 +/- 5.9 mm2, and the area stenosis was 13 +/- 19%. In the 27 patients with plaque, plaque area was 8.7 +/- 5.7 mm2 and the area stenosis was 30 +/- 17%. The vessel area was significantly larger in diseased LMCAs (p < 0.001) and correlated with plaque area (r = 0.46). IU examination of the LMCA was feasible in 87% of patients and was more reliable for delineating plaques than angiography.

Improved Assessment of Coronary Stenosis Severity Using the Relative Flow Velocity Reserve

BACKGROUND Myocardial fractional flow reserve (FFR) is based on pressure measurements. We have now sought to establish a Doppler-based concept of relative flow velocity reserve (RFVR) for the functional assessment of stenosis severity in epicardial coronary arteries. A clear threshold value to discriminate the functional severity of a coronary stenosis does not exist for coronary flow velocity reserve (CVR) based on intracoronary Doppler measurements. In contrast, the concept of FFR, which is based on intracoronary pressure measurements, has been extensively validated. An FFR value below 0.75 reliably indicates a significant stenosis. METHODS AND RESULTS RFVR is calculated as the ratio between distal CVR in the stenosed target vessel and distal CVR in a nonstenotic reference vessel. In 21 patients, RFVR was determined in 24 target vessels by use of intracoronary adenosine and correlated to the FFR, determined as the ratio of mean poststenotic to aortic pressures, in the target vessel. Stenosis severity was classified according to quantitative coronary angiography analysis. Reference diameter was 3.0+/-0.4 mm (mean+/-SD), and area stenosis was 74+/-15% (range, 40% to 95%). CVRs in the target and reference vessels were 2.1+/-0.5 and 2.6+/-0.7, respectively. FFR ranged from 0.49 to 0.99 (mean, 0.81+/-0.15) and RFVR from 0.53 to 1.0 (mean, 0.82+/-0.13). Poststenotic CVR did not correlate with either percent area stenosis (r=0.27, P=NS) or FFR (r=0.33, P=NS). In contrast, FFR as well as RFVR showed a curvilinear relation to percent area stenosis (r=0.89, P<0.0001 and r=0.79, P<0.0001, respectively). There was a close linear correlation between FFR and RFVR (r=0.91, P<0.0001). CONCLUSIONS RFVR correlates closely to FFR and to percent area stenosis, whereas the correlation of CVR with FFR and percent area stenosis is rather poor. RFVR is a promising new concept for assessment of coronary stenosis severity and clinical decision making based on Doppler measurements.

Augmented α-Adrenergic Constriction of Atherosclerotic Human Coronary Arteries

Background—Although adrenergic activation plays a major role in the initiation of experimental myocardial ischemia, the significance of α-adrenergic coronary constriction in humans has been questioned. The present study assessed the impact of selective α-adrenergic receptor activation in patients with normal or atherosclerotic coronary arteries. Methods and Results—In 39 patients, coronary blood flow (CBF, mL/min) was determined from combined angiography and Doppler measurements. In 8 patients with normal coronary arteries (group 1) and 9 with single coronary artery stenosis (group 2), doses of 1, 2.5, 5, and 10 mg IC of the α1-agonist methoxamine (M) were injected. Identical doses of the α2-agonist BHT933 (B) were injected in 8 patients with normal coronary arteries (group 3) and 8 with single stenosis (group 4). In 6 additional patients with single stenosis (group 5), aortocoronary sinus lactate differences were measured in response to M and B. CBF remained unchanged in group 1. In contrast, CBF was dec...

Comparison of electron-beam computed tomography and intracoronary ultrasound in detecting calcified and noncalcified plaques in patients with acute coronary syndromes and no or minimal to moderate angiographic coronary artery disease

We compared intracoronary ultrasound (ICUS) and electron-beam computed tomography (EBCT) on a coronary segmental basis in 40 consecutive patients with acute coronary syndromes and no or minimal to moderate angiographic disease (53+/-10 years; 34 men, 6 women). ICUS was used to define plaques, and EBCT was used to quantify coronary calcium (using a threshold of a CT density > 130 Hounsfield units in an area > 1.03 mm2). In a site-by-site analysis, coronary segments were defined as normal if both methods were negative, as containing noncalcified plaques if only ICUS was positive, and as containing calcified plaques if both methods were positive. A total of 222 coronary segments were analyzed (5.6+/-1.9 segments per patient). In 36 patients (90%), a total of 95 segments with plaques were identified, whereas in 4 patients (10%), only normal segments were seen. Of the 95 segments with plaques, 61 (64%) were calcified, and 34 (36%) were noncalcified. There was a linear relationship between the number of segments with calcified and with noncalcified plaques (r = 0.86, p <0.0001), but the mean relative frequency of segments with calcified plaques (55+/-38%) was highly variable. Calcium was found in 15 of 16 patients (93%) with 3 or more segments with plaques, while it was found in only 12 of 20 patients (60%) with one or 2 segments with plaques (p = 0.026). Younger age, higher low-density lipoprotein-cholesterol levels, diabetes, and active smoking predicted a higher relative frequency of segments with noncalcified plaques. Thus, in patients with acute coronary syndromes but no angiographically critical stenoses, there is a linear relationship between segments with calcified plaques versus segments with noncalcified plaques. However, while the mean ratio of these segments is close to 1:1, it is highly variable among individual patients.

Coronary artery remodeling in atherosclerotic disease: An intravascular ultrasonic study in vivo

BackgroundPathologic studies have revealed that coronary arteries undergo compensatory enlargement in the presence of atherosclerosis. MethodsIn order to assess coronary artery remodeling in vivo, we used intravascular ultrasound to examine 46 patients (36 men and 10 women; aged 58.2 ± 6.8 years) with non-calcified plaques. The vessel, lumen, and plaque areas of the atherosclerotic and of normal proximal and distal segments were determined. ResultsA total of 92 atherosclerotic segments were analyzed. The degree of stenosis ranged from 9.2 to 92.8% (mean 34.1 ±16.9%) and the plaque area from 2 to 19.6 mm2 (mean 6.3 ± 3.6 mm2). The vessel area of the atherosclerotic segment (mean 20.4 ± 7.3 mm2) was larger than that of the proximal segment (mean 18.7 ± 7.3 mm2, P = 0.018). The vessel area increased in proportion to plaque area. This relationship can be described using the equation y = 23.5(1 -e -0.35x). The difference between the vessel area in the atherosclerotic segment and that in the proximal normal segment correlated with the percentage of stenosis (r = 0.53, P <; 0.005) until the degree of stenosis exceeded 45%. ConclusionThis study indicates that coronary artery remodeling, previously observed in pathologic studies, can be evaluated using intravascular ultrasound in vivo. As a result of the compensatory enlargement of the vessel, coronary angiography cannot be used to detect or exclude the early signs of coronary atherosclerosis.

Classification of morphologic effects of percutaneous transluminal coronary angioplasty assessed by intravascular ultrasound

The aim of this study was the assessment and classification of the morphologic effects of percutaneous transluminal angioplasty (PTCA) by intravascular ultrasound (IU). Fifty-eight patients were examined immediately after PTCA with a 4.8Fr, 20 MHz rotational tip IU system. In 10 patients (17%), IU images could not be analyzed due to failure of the imaging system or poor image quality. In 48 patients (83%; 40 men and 8 women, aged 55 +/- 9 years), IU images of 48 PTCA segments, as well as 41 distal and 44 proximal sites, were analyzed. The left anterior descending artery was studied in 30 patients, the right coronary artery in 17 and the left main coronary artery in 1. Calcium was present in 32 of 48 PTCA segments (67%). Plaque morphology was concentric in 18 patients (38%) and eccentric in 30 (62%). Seven distinct morphologic patterns were observed. In concentric plaques, plaque compression without significant wall alterations (type 1) was found in 2 patients (4%), superficial tears within the plaque (type 2) in 1 (2%) and deep tears (type 3) in 8 (17%). Deep tearing associated with submedial or subintimal dissection (type 4) was found in 2 patients (4%). Dissection between plaque and vessel wall without noticeable intimal tearing (type 5) was the most common morphology (n = 15; 31%) and occurred in concentric and eccentric plaques. In eccentric plaques, no significant tearing of the plaque (type 6) was found in 6 patients (13%), and tearing of the plaque close to its base with dissection (type 7) in 14 (29%).(ABSTRACT TRUNCATED AT 250 WORDS)