Noninvasive anatomical coronary artery imaging versus myocardial perfusion imaging: which confers superior diagnostic and prognostic information?

Serum protein profiles predict coronary artery disease in symptomatic patients referred for coronary angiography

BACKGROUND

More than a million diagnostic cardiac catheterizations are performed annually in the US for evaluation of coronary artery anatomy and the presence of atherosclerosis. Nearly half of these patients have no significant coronary lesions or do not require mechanical or surgical revascularization. Consequently, the ability to rule out clinically significant coronary artery disease (CAD) using low cost, low risk tests of serum biomarkers in even a small percentage of patients with normal coronary arteries could be highly beneficial.

METHODS

Serum from 359 symptomatic subjects referred for catheterization was interrogated for proteins involved in atherogenesis, atherosclerosis, and plaque vulnerability. Coronary angiography classified 150 patients without flow-limiting CAD who did not require percutaneous intervention (PCI) while 209 required coronary revascularization (stents, angioplasty, or coronary artery bypass graft surgery). Continuous variables were compared across the two patient groups for each analyte including calculation of false discovery rate (FDR ≤ 1%) and Q value (P value for statistical significance adjusted to ≤ 0.01).

RESULTS

Significant differences were detected in circulating proteins from patients requiring revascularization including increased apolipoprotein B100 (APO-B100), C-reactive protein (CRP), fibrinogen, vascular cell adhesion molecule 1 (VCAM-1), myeloperoxidase (MPO), resistin, osteopontin, interleukin (IL)-1β, IL-6, IL-10 and N-terminal fragment protein precursor brain natriuretic peptide (NT-pBNP) and decreased apolipoprotein A1 (APO-A1). Biomarker classification signatures comprising up to 5 analytes were identified using a tunable scoring function trained against 239 samples and validated with 120 additional samples. A total of 14 overlapping signatures classified patients without significant coronary disease (38% to 59% specificity) while maintaining 95% sensitivity for patients requiring revascularization. Osteopontin (14 times) and resistin (10 times) were most frequently represented among these diagnostic signatures. The most efficacious protein signature in validation studies comprised osteopontin (OPN), resistin, matrix metalloproteinase 7 (MMP7) and interferon γ (IFNγ) as a four-marker panel while the addition of either CRP or adiponectin (ACRP-30) yielded comparable results in five protein signatures.

CONCLUSIONS

Proteins in the serum of CAD patients predominantly reflected (1) a positive acute phase, inflammatory response and (2) alterations in lipid metabolism, transport, peroxidation and accumulation. There were surprisingly few indicators of growth factor activation or extracellular matrix remodeling in the serum of CAD patients except for elevated OPN. These data suggest that many symptomatic patients without significant CAD could be identified by a targeted multiplex serum protein test without cardiac catheterization thereby eliminating exposure to ionizing radiation and decreasing the economic burden of angiographic testing for these patients.

Association of coronary artery calcium with severity of myocardial ischemia in left anterior descending, left circumflex, and right coronary artery territories

BACKGROUND

An increasing coronary artery calcium score is associated with a higher likelihood of myocardial ischemia.

HYPOTHESIS

The association of the coronary calcium score with myocardial ischemia in different coronary arteries needed to be investigated.

METHODS

We correlated the coronary artery calcium (CAC) score with the severity of myocardial ischemia diagnosed by myocardial perfusion imaging in the left anterior descending (LAD), left circumflex (LCX), and right coronary artery (RCA) territories in 206 patients, mean age 66 years, without cardiac stents or coronary artery surgery.

RESULTS

The mean CAC score in the LAD coronary artery was 160 ± 218 in patients with no or mild ischemia and 336 ± 379 in patients with moderate or severe ischemia (P = 0.039). The mean CAC score in the LCX coronary artery was 57 ± 117 in patients with no or mild ischemia and 161 ± 191 in patients with moderate or severe ischemia (P = 0.018). The mean CAC score in the RCA was 114 ± 237 in patients with no or mild ischemia and 261 ± 321 in patients with moderate or severe ischemia (P = 0.045). Stepwise linear regression analysis showed that male gender (P < 0.0001), age (P < 0.0001), and moderate or severe ischemia (P = 0.023) were significantly associated with high LAD coronary artery CAC scores. Male gender (P < 0.0001), age (P = 0.0002), and moderate or severe ischemia (P = 0.006) were significantly associated with high LCX coronary artery CAC scores. Male gender (P < 0.0001) and age (P < 0.0001) were significantly associated with high RCA CAC scores.

CONCLUSIONS

Higher CAC scores are significantly associated with moderate or severe ischemia in the LAD and LCX coronary arteries.

[Exclusion of coronary artery disease using cardiac CT. What impact do CT results have on patient management?]

Rapid advancement of multidetector head computed tomography (MDCT) during the past 10 years has facilitated noninvasive evaluation of CAD (coronary artery disease). Since the introduction of 320-row technology, examination of the whole heart in a single heart beat with diagnostic quality has become feasible. Direct imaging of vessel morphology, a high sensitivity for CAD above 96%, and low requirements of patient compliance represent advantages over other imaging modalities, such as MRI (magnetic resonance imaging), scintigraphy, and echocardiography. In some cases radiation exposure can be reduced to an effective dose below 1 mSV.Current data suggest that cardiac CT represents a more effective diagnostic tool than treadmill testing in order to decide whether cardiac catheterization is indicated. Treadmill testing has been an integral procedure of cardiac examinations for decades, although sensitivity for detecting CAD is as low as 70%.Cardiac CT represents a rather new modality and is almost exclusively performed in diagnostic imaging centers. Innovative concepts in the evaluation of CAD including CT are expected. Some authors propose cardiac CT as a major diagnostic tool for the exclusion of CAD. MRI, scintigraphy, or echocardiography in combination with a stress test remain important procedures in order to evaluate the hemodynamic relevance of coronary artery stenosis. Treadmill testing prior to cardiac CT has become questionable.The future role of cardiac CT in CAD in "change of management" concepts is promising. In order to optimize decisions of patient management on the basis of a cardiac CT examinations, awareness of current data is mandatory for the referring clinician and the performing radiological department.

64-multidetector computed tomographic angiography of the canine coronary arteries

Canine coronary artery angiography (CTA) was performed in four anesthetized healthy dogs using 64-multidetector computed tomography. Esmolol, a β-1 adrenergic receptor antagonist, and sodium nitroprusside, an arteriolar and venous dilator, were administered to enhance visualization of the coronary arteries by reducing heart rate and creating vasodilation. The left main coronary artery with its three main branches and the right coronary artery were visualized and subdivided in 13 segments for evaluation. Optimal reconstruction interval, expressed as percentage of the R-to-R interval, was determined at 5% in 2.9%, 35% in 1%, 75% in 21.2%, 85% in 43.3%, and 95% in 31.7% of the segments. Overall image quality was good in 41.3% of the segments and excellent in 14.4%. There was blur in 98.1%, motion in 17.3%, and stair step in 6.7% of the evaluated segments, but these artifacts did not interfere with anatomic depiction of the arteries. Cross-sectional anatomy of the coronary arteries as evaluated from the coronary CTA agreed well with gross anatomic evaluation and published information. The use of esmolol did not lead to the target heart rate of 60-65 beats/min. Nitroprusside had no significant effect on visualized length or diameter of the coronary artery branches. Coronary CTA is useful for the anatomic depiction of coronary artery branches in the dog.