Absence of coronary calcification on double-helical CT scans: predictor of angiographically normal coronary arteries in elderly women?

Non-traditional tools for predicting coronary artery disease

Background

The traditional coronary calcium score (CCS) is a time-tested tool for the evaluation of coronary atherosclerosis and predictor of future cardiovascular events. Non-traditional tools can also have a value in predicting and detecting subclinical coronary artery disease (CAD).

Methods

We studied the role of CCS, the traditional CAD risk predictor, and the less-recognized, non-traditional risk factors, i.e. epicardial fat volume (EFV) and thoracic extracoronary calcium (ECC), to assess the degree of subclinical CAD. In this cross-sectional observational study, we included 950 Indian patients (suspected to have CAD). Coronary computed tomography angiography was performed. Estimation of CCS, EFV and thoracic ECC was done.

Results

A CCS of 0 was seen in 583 patients (61.4%). Of these, 492 patients had normal coronary angiogram but 91 patients had CAD. The median values of EFV were statistically significantly higher in the ‘CAD present and CCS 0’ group compared to the ‘CAD absent and CCS 0’ group (p<0.001). The presence of thoracic ECC involving at least a single site was seen in only 6 of these 91 patients. When both EFV and CCS were considered together for the detection of CAD, the sensitivity and negative predictive value (NPV) were improved compared to either of these in isolation. When ECC was taken together with CCS and EFV, no further improvement in sensitivity or NPV was observed.

Conclusion

The combined use of traditional CCS along with non-traditional EFV may guide us in better profiling cardiovascular risk and supplement the various traditional cardiovascular risk factors/scores.

The Multi-Ethnic Study of Atherosclerosis-Calcium Score Improves Statin Treatment Allocation in Asymptomatic Adults

Background

The current categorization of cardiovascular (CV) risk broadens the indications for statin therapy. Coronary artery calcium (CAC) identifies those who are most likely to benefit from primary prevention with statin therapy. The multi-ethnic study of atherosclerosis-calcium (MESA-C) includes CAC for CV risk stratification.

Objective

We aimed to establish whether the MESA-C score improves allocation to statin treatment in a cohort of asymptomatic adults. We also analyzed patient survival according to their risk score calculation.

Design

A retrospective analysis of asymptomatic adults.

Participants

A total of 632 consecutive subjects free of coronary artery disease (CAD) and/or stroke, mean age 56 ± 7 years, 84% male, underwent clinical evaluations and CAC measurements.

Main Measures

PCE and MESA-C risk scores were calculated for each subject. According to the 10-year risk for CV events, subjects were classified into moderate and high CV risk (≥7.5%) for whom a statin is clearly indicated, or borderline and low CV risk (<7.5%).

Key Results

During mean follow-up of 6.5 ± 3.3 years, 52 subjects experienced their first CV event. Those with a MESA-C risk score < 7.5% had favorable outcomes even when the PCE indicated a risk of ≥ 7.5%. The MESA-C score improved the discrimination of CV risk with the ROC curves C-statistics increasing from 0.653 for the PCE to 0.770 for the MESA-C. Of those, 84% (99/118) with borderline CV risk (5–7.5%) according to the PCE score, were reallocated by the MESA-C score into a higher (≥7.5%) or lower (<5%) CV risk category. Furthermore, subjects with low MESA-C scores had the highest survival rate regardless of the PCE risk, while those with high MESA-C risks had the lowest survival rate regardless of the PCE risk.

Conclusion

In asymptomatic subjects, the MESA-C score improves allocation to statin treatment and CV risk discrimination, while both scores are essential for more precise survival estimations.

Assessment of subclinical atherosclerosis and cardiovascular risk

Conventional cardiac risk factors do not fully explain the incidence of coronary artery disease and coronary events. Risk stratification and therapy based solely on these conventional risk factors may exclude a population who would otherwise benefit from lifestyle and risk factor modification. Recent efforts to improve our ability to recognize individuals and populations at increased risk of coronary events have focused on the noninvasive imaging of atherosclerosis, both in coronary and extracoronary arterial beds, or the identification of "non-traditional" serum markers. We review the complimentary role of these newer methods of risk stratification in the context of conventional risk factor evaluation.

Coronary arterial calcification on low-dose ungated MDCT for lung cancer screening: concordance study with dedicated cardiac CT

OBJECTIVE

Coronary artery calcification (CAC) is frequently detected on low-dose ungated MDCT performed for lung cancer screening. We aimed to determine the concordance of CAC scores on low-dose ungated and regular-dose ECG-gated MDCT.

SUBJECTS AND METHODS

The subjects were 513 patients consecutively registered for health screening and undergoing both low-dose ungated (120 kVp, 20 mAs) and regular-dose ECG-gated MDCT (120 kVp, 150 mAs, retrospective ECG gating). The first 30 cases were used for protocol optimization and a training session. Agatston score on regular-dose ECG-gated and low-dose ungated MDCT in the other 483 cases (320 men; mean age, 62.2 +/- 13.2 [SD] years) was calculated by two observers in a blinded manner. Interobserver and intertechnique scoring variability and concordance were calculated.

RESULTS

The mean of interobserver scoring variability for regular-dose ECG-gated MDCT was 3.6% and for low-dose ungated MDCT was 9.6%. Regular-dose ECG-gated MDCT depicted CAC in 221 (46%) of the subjects. With low-dose ungated MDCT, observers 1 and 2, respectively, had five and seven false-positive and five and four false-negative predictions. All the miscategorized scores were 12 or less. The negative predictive values of CAC on low-dose ungated MDCT were 98% and 99% for observers 1 and 2, respectively. For patients with CAC, the mean intertechnique scoring variability was 40-43%. For all 483 subjects, the intertechnique concordance of the four major score ranks (0, 1-100, 101-400, > 400) was high (kappa = 0.89 for the two observers).

CONCLUSION

Low-dose ungated MDCT with an optimized protocol is reliable for prediction of the presence of CAC and categorization of the four major Agatston score ranks. This technique may be useful for coronary artery disease risk stratification of persons undergoing low-dose ungated MDCT for lung cancer screening.

Noninvasive cardiac imaging with computed tomography

Despite major improvements in the treatment of heart disease, it remains a major source of morbidity and mortality on a global scale. Currently, invasive coronary angiography remains the gold standard for identification of obstructive coronary artery disease. However, recent advances in computerized tomographic (CT) techniques of the heart allow for accurate, noninvasive characterization of atherosclerotic coronary disease and other cardiac abnormalities. The calculation of coronary artery calcium scores with electron beam CT has largely been supplanted by high-resolution CT angiography using multislice detectors (MSCT) which can provide detailed multidimensional visualization of cardiac structures. Although evaluation of obstructive coronary disease is the primary use of MSCT, its use in identifying congenital defects, planning thoracic procedures and characterizing cardiac function continues to grow. Accordingly, appropriate incorporation of MSCT/CT angiography into clinical practice continues to be defined. Several limitations to MSCT remain which reduce its accuracy, such as in patients with arrhythmia and in patients with either coronary stents or heavily calcified coronaries. Despite its current limitations, MSCT remains a rapidly advancing field and an increasingly valuable tool for the noninvasive evaluation of cardiac pathology.

CT of Coronary Artery Disease

The clinical relevance of coronary artery disease has considerably driven the recent development of radiologic tools for noninvasive cardiac imaging. Modern multidetector row computed tomographic (MDCT) systems combine high temporal and spatial resolution, electrocardiographic synchronization, and ease of use. In cardiac imaging, MDCT has not only replaced electron-beam CT, but also challenges competing methods such as magnetic resonance imaging, echocardiography, or even coronary catheterization. Noncontrast material-enhanced assessment of atherosclerotic plaques (CT calcium scoring) seems useful for the cardiac risk stratification in asymptomatic patients and monitoring of medical (statin) therapy. Contrast material-enhanced CT coronary angiography has become established as a valuable method for several clinical indications such as evaluation of coronary artery anomalies, bypass patency, or preoperative planning. Particularly, the high negative predictive value of a normal CT coronary angiogram allows reliable exclusion of coronary artery stenosis. Plaque characterization is another promising area of research in MDCT cardiac imaging. However, with current technology a reliable distinction between atheroma and fibroatheroma is impaired by restrictions in spatial resolution. Recent studies indicate that CT angiography may also be suited for other clinical applications such as triage of patients with acute coronary syndrome and inconclusive clinical presentation, patients with symptomatic chest pain, and intermediate risk profile or cardiac risk stratification in asymptomatic patients.

Frequency of coronary artery calcification on low-dose computed tomography screening for lung cancer

PURPOSE

The purpose of this study was to determine the frequency of coronary artery calcification (CAC) in high-risk people undergoing computed tomography (CT) screening for lung cancer.

METHODS

Between 1999 and 2004, we performed CT screening for lung cancer on 4250 participants, all without documented prior cardiovascular disease, using multidetector-row (MD) CT. Of the patients, 1102 underwent imaging with a four-detector-row CT at 120 kVp and 40 mA, with pitch 1.5 and collimation of 2.5 mm in a single breath hold of 15-20 seconds, and 3148 did with an eight-detector-row CT at the same kVp, mA, and pitch settings but with collimation of 1.25 mm. Visualized CACs in each coronary artery (main, left anterior descending, circumflex, and right) were scored separately as 0 (absent), 1 (mild), 2 (moderate), or 3 (severe), yielding a possible score of 0-12 for each person. Frequency distributions by gender, age, and pack-years of smoking were determined. Odds ratios (ORs) were calculated using logistic regression analysis of the prevalence of CAC as a joint function of gender, age, pack-years of smoking, and presence of diabetes.

RESULTS

Among the subjects younger than 50 years, positive CAC scores were three times more frequent for men than for women (22% vs. 7%); among those older than 50 years, the frequency increased for both men and women but the increase for women was greater than that for men. The frequency of positive CAC scores increased with increasing pack-years of smoking; it was always higher for men than for women. The ORs were 2.6 for male gender (P<.0001), 3.7 and 9.6 for ages 60-69 years and 70 years or older, respectively, for increasing age (P<.0001 for both), 1.6 and 2.3 for 30-59 pack-years and 60 pack-years or longer, respectively, for increasing pack-years of smoking (P<.0001 for both), and 1.6 for having diabetes (P=.016).

CONCLUSION

The CAC score can be derived from ungated low-dose MDCT images. This information can contribute to risk stratification and management of coronary artery disease.

Usefulness of helical computed tomography in detection of mitral annular calcification as a marker of coronary artery disease

BACKGROUND

Mitral annulus calcification (MAC) may be a form of atherosclerosis. The goal of the present work was to investigate whether helical CT can determine the presence of MAC and to clarify its possible association with coronary artery disease (CAD) in elderly patients.

DESIGN AND METHODS

Three hundred and twenty-nine consecutive elderly patients (165 men and 164 women, age range 60-79 years) underwent double helical CT of the heart to determine MAC and coronary calcifications (CC) according to a previously described protocol.

RESULTS

MAC was documented in 60 patients (25 men, 35 women; mean age 69 +/- 4.5 years, range 60-78 years). The non-MAC group (control) included 269 patients (140 men, 129 women; mean age 67 +/- 4.6 years, range 60-79 years). Age was the only risk factor which had significant association with MAC (p = 0.01). A significant difference was found between MAC and control group for mean total CC score and advanced CC (total CC > 300) (323 +/- 565 vs. 184 +/- 429, p = 0.033 and 30% vs. 16%, p = 0.017, respectively). A significant difference was also found between groups for the prevalent proven CAD (30% vs. 16%, p = 0.008). Stepwise logistic regression analysis identified age [odds ratio (OR) 3.3, 95% confidence interval (CI) 1.7-6.4, p < 0.001)], gender (male) (OR 3.1, 95% CI 1.6-6.0, p = 0.001), and MAC (OR 2.4, 95% CI 1.2-5.0, p = 0.016) as the independent variables significantly associated with CAD. The independent variables significantly associated with advanced CC (TCS > 300) were MAC (OR 2.6, 95% CI 1.3-5.2, p = 0.005), gender (male) (OR 2.3, 95% CI 1.2-4.2, p = 0.012) and age (OR 1.9, 95% CI 1.0-3.7, p = 0.052).

CONCLUSIONS

Our study demonstrated the usefulness of helical computed tomography in the detection of mitral annular calcification as an additional marker of prevalent CAD. However, the diagnostic significance of the MAC detection is relatively minor and should not be considered as a direct proof for coronary atherosclerosis.

Update on using coronary calcium screening by computed tomography to measure risk for coronary heart disease

Coronary artery disease (CAD) is the number one killer of adults in the United States, claiming one-half million deaths annually. Early detection and prevention strategies clearly remain a top priority for health care providers in order to reduce the high mortality rate of heart disease. As an unequivocal reflection of arteriosclerosis, coronary arterial calcium (CAC) may provide a means to qualitatively assess the overall disease severity and likewise serve as a means to assess risk for CHD. It is known that patients with heavy calcium burdens have more advanced CAD, a concomitantly a higher likelihood of coronary stenoses, and a concomitant higher risk for acute cardiac events. Computed tomography has been shown to be an accurate, non-invasive method to quantify coronary calcification burden in patients. Evidence shows that calcium measurements by CT correlate well with histological plaque analyses, and that CAC measurements accurately reflect disease severity and can be useful to assess individual risk for CHD. The purpose of this article is to summarize the currently available evidence that has attempted to validate CAC screening as a screening exam and risk predictor for coronary heart disease.

Coronary artery calcium outperforms carotid artery intima-media thickness as a noninvasive index of prevalent coronary artery stenosis

OBJECTIVE

Increased carotid artery intima-media thickness (IMT) and increased coronary artery calcium (CAC) are noninvasive surrogate indices of prevalent coronary artery disease (CAD). We compared CAC to IMT for noninvasive detection of prevalent CAD in participants whose coronary status was identified by coronary angiography.

METHODS AND RESULTS

Male and female CAD patients (> or =50% stenosis in one or more coronary artery, n=79) and controls (no lumen irregularities, n=93) were identified using coronary angiography. Mean maximum carotid IMT was quantified using B-mode ultrasound and total CAC was measured using ECG-gated helical computed tomography (HCT). Carotid IMT was approximately 20% higher in CAD cases compared with controls (P<0.001), whereas mean CAC was 1000% higher in CAD cases than controls (P<0.0001). In multivariable models adjusted for age and sex, IMT greater than the median (1.13 mm) was associated with 2-fold increase in likelihood of prevalent CAD compared with scores below that cut point (P=0.015). CAC scores that exceeded the median score of 92 were associated with 28-fold increase in likelihood of prevalent CAD (P<0.0001). Although associations of increased IMT with prevalent CAD were similar in males and females, CAC scores above the median in females were associated with 39-fold increase in odds of prevalent CAD, whereas males with elevated CAC had 19-fold risk of CAD.

CONCLUSIONS

HCT-measured CAC compares favorably with carotid IMT measured by B-mode ultrasound as a noninvasive index of prevalent CAD.

CT for imaging coronary artery disease: defining the paradigm for its application

Current generation multidetector-row CT (MDCT) enables high-resolution, motion-free imaging of the heart within a single, short breath-hold. MDCT allows highly accurate and reproducible quantification of coronary artery calcium, a marker that has been used for the detection, exclusion and monitoring of coronary atherosclerosis. The exact role of coronary calcium measurements for cardiac risk stratification remains unclear to date. At contrast enhanced MDCT coronary angiography coronary arteries can be visualized with unprecedented detail. The accurate non-invasive assessment of the presence and degree of coronary artery stenosis appears within reach. With increasing accuracy MDCT enables non-invasive patency evaluation of coronary artery bypass grafts and coronary stents. The cross-sectional nature of contrast enhanced MDCT coronary angiography allows assessment of the vessel wall and may permit more accurate quantification of total atherosclerotic plaque burden than measuring calcified components alone. For a limited time, future technical improvement will be pursued mainly by accelerated gantry rotation speed and additional detector rows. However, novel concepts of CT image acquisition are already under investigation and may bring about yet another quantum leap for medical CT. This communication discusses potential approaches for the beneficial utilization of MDCT for the assessment of patients with known or suspected coronary heart disease.

CT of coronary artery disease

The socioeconomic importance of heart disease provides considerable motivation for development of radiologic tools for noninvasive imaging of the coronary arteries. Current computed tomographic (CT) techniques combine high speed and spatial resolution with sophisticated electrocardiographic synchronization and robustness of use. Application of these modalities for evaluation of coronary artery disease is a topic of active current research. Coronary artery calcium measurements with different CT techniques have been used for determining the risk of coronary events, but the exact role of this marker for cardiac risk stratification remains unclear pending results of population-based studies. Contrast material-enhanced CT coronary angiography has become an established clinical indication for some scenarios (eg, coronary artery anomalies, bypass patency, surgical planning). With current technology, the accuracy of CT coronary angiography for detection of coronary artery stenoses appears promising enough to warrant pursuit of this application, but sensitivity is still not high enough for routine diagnostic needs. The high negative predictive value of a normal CT coronary angiogram, however, may be useful for reliable exclusion of coronary artery stenosis. The cross-sectional nature of CT may allow noninvasive assessment of the coronary artery wall. Use of contrast-enhanced CT coronary angiography for detection, characterization, and quantification of atherosclerotic changes and total disease burden in coronary arteries as a potential tool for cardiac risk stratification is currently being investigated.

Coronary Artery Calcification Scoring by Prospectively Triggered Multidetector-Row Computed Tomography

The objective of this study was to measure the interobserver and interscan variation of coronary artery calcium scores using multidetector-row computed tomography (MDCT). Seventy-five patients underwent 2 sequential MDCT scans for coronary artery calcification. Each patient's score was separately measured by 3-blinded radiologists. Scores were treated as discrete and continuous data, and independent statistical analysis was performed on all results. There was a high proportion of interscan and inter-reader concordance for the presence of coronary calcium (range, 0.893-0.973) and for its quantity (range, 0.936-0.988). Overall, prospectively triggered multidetector-row calcium scoring is reproducible though there is more variation in those patients with already high scores. There is no need to scan patients twice at the same sitting.

Imaging of coronary calcification by computed tomography

As an unequivocal biomarker for arteriosclerosis, the presence of coronary calcium serves as a qualitative reflection of the severity of coronary artery disease (CAD). Greater calcium burdens correlate with more advanced disease, a higher likelihood of coronary stenoses, and a higher risk for coronary heart disease (CHD). Empirically, the quantification of coronary calcium not only provides an accurate reflection of disease severity, but also has great potential as a screening tool for CHD. Computed tomography (CT) has been shown to be capable of providing accurate, noninvasive measurements of coronary calcification. Evidence shows that calcium measurements by CT correlate well with histological plaque analyses, and that calcium burdens accurately reflect disease severity and can be used to assess individual risk for CHD. The purpose of this review article is to examine the accumulated evidence that has attempted to validate CT as a diagnostic tool for CAD and as a screening exam for CHD.

Accelerated coronary artery calcification in mildly reduced renal function of high-risk hypertensives

OBJECTIVE

To examine the effect of mild renal dysfunction on coronary artery calcifications.

METHODS

We examined the progression of coronary atherosclerosis, as measured by dual-section spiral computed tomography, using the total coronary artery calcium score as a quantitative measure of the burden of atherosclerosis. Of 547 high-risk Israeli hypertensive patients, who were participants of the prospective calcification study (a side-arm of the international INSIGHT study), 313 patients completed the 3-year follow-up. Subjects were studied upon entry (on placebo) and again after 3 years of treatment (nifedipine or thiazide). Patients were divided into two groups depending on their creatinine clearance: (i) </= 60 ml/min, renal dysfunction (RD) (n = 53) and (ii) > 60 ml/min, normal renal function group (n = 263).

RESULTS

Blood pressure, hypercholesterolemia, and smoking did not differ between the groups. After 3 years of treatment, blood pressure control was similar, whereas the total coronary artery calcium score progression was two-fold greater in the RD than the normal group (156 +/- 32 versus 64 +/- 8, respectively) (P = 0.006). In a multiple logistic regression analysis, the odds ratio (OR) for total coronary artery calcium score progression was higher for the RD group (2.1) [95% confidence interval (CI) 1.2-3.7]. Gender, body mass index, smoking, cholesterol, family history of ischaemic heart disease and diabetes were not significant predictors. Thiazide-based antihypertensive therapy predicted a faster progression compared to nifedipine (OR 1.66, 95% CI 1.09-2.51).

CONCLUSIONS

Mild renal dysfunction accelerates coronary artery calcifications, above and beyond conventional risk factors.

Imaging in the evaluation of the patient with suspected acute coronary syndrome

Patients presenting to the emergency department with chest pain have a common problem. Definitive diagnosis at presentation is difficult due to limitations of the initial evaluation, and, thus, the majority of patients are admitted. Recognition of these limitations has driven the investigation of alternative evaluation techniques and protocols to attempt to improve diagnostic sensitivity without increasing overall costs. Acute myocardial perfusion imaging has been a highly valuable technique for risk stratification of intermediate to low-risk patients with chest pain. However, for a variety of reasons, it has not been widely embraced. In the past few years, alternative techniques have been investigated for use in the diagnosis of acute coronary syndromes in the acute setting. Coronary calcium scoring and cardiac magnetic resonance imaging show promise as new tools in the armamentarium for acute coronary syndromes. The challenge now lays in developing a strategy that uses these and future techniques most appropriately to support optimal medical decision making.

Multidetector-row CT of the heart

Despite worldwide efforts aimed at primary and secondary prevention, heart disease is still the leading cause of death in the western world. There is great interest in developing tools for noninvasive assessment of the presence and degree of coronary artery disease. The advent of multidetector-row CT allows high-resolution volume coverage of the entire thorax and motion-free imaging of the heart and adjacent vessels within one breathhold. An exciting application with significant potential for cardiac risk stratification, which may overcome the obvious limitations of coronary calcium imaging in the future, is the use of the cross-sectional nature of contrast-enhanced multidetector-row CT coronary angiography for assessment of total coronary artery plaque burden.

Assessment of calcium scoring performance in cardiac computed tomography

Electron beam tomography (EBT) has been used for cardiac diagnosis and the quantitative assessment of coronary calcium since the late 1980s. The introduction of mechanical multi-slice spiral CT (MSCT) scanners with shorter rotation times opened new possibilities of cardiac imaging with conventional CT scanners. The purpose of this work was to qualitatively and quantitatively evaluate the performance for EBT and MSCT for the task of coronary artery calcium imaging as a function of acquisition protocol, heart rate, spiral reconstruction algorithm (where applicable) and calcium scoring method. A cardiac CT semi-anthropomorphic phantom was designed and manufactured for the investigation of all relevant image quality parameters in cardiac CT. This phantom includes various test objects, some of which can be moved within the anthropomorphic phantom in a manner that mimics realistic heart motion. These tools were used to qualitatively and quantitatively demonstrate the accuracy of coronary calcium imaging using typical protocols for an electron beam (Evolution C-150XP, Imatron, South San Francisco, Calif.) and a 0.5-s four-slice spiral CT scanner (Sensation 4, Siemens, Erlangen, Germany). A special focus was put on the method of quantifying coronary calcium, and three scoring systems were evaluated (Agatston, volume, and mass scoring). Good reproducibility in coronary calcium scoring is always the result of a combination of high temporal and spatial resolution; consequently, thin-slice protocols in combination with retrospective gating on MSCT scanners yielded the best results. The Agatston score was found to be the least reproducible scoring method. The hydroxyapatite mass, being better reproducible and comparable on different scanners and being a physical quantitative measure, appears to be the method of choice for future clinical studies. The hydroxyapatite mass is highly correlated to the Agatston score. The introduced phantoms can be used to quantitatively assess the performance characteristics of, for example, different scanners, reconstruction algorithms, and quantification methods in cardiac CT. This is especially important for quantitative tasks, such as the determination of the amount of calcium in the coronary arteries, to achieve high and constant quality in this field.

Coronary calcium detected by digital cinefluoroscopy and coronary artery disease in patients undergoing coronary arteriography: effects of age and sex

BACKGROUND

Coronary artery calcium, detected non-invasively, correlates well with angiographically documented coronary artery disease (CAD). This study was conducted to evaluate the diagnostic efficacy of coronary artery calcium detected by digital cinefluoroscopy for CAD and assess the effects of age and sex on it.

METHODS

In 242 patients who underwent coronary angiography, coronary calcium status was determined and related to angiographic findings.

RESULTS

Calcium detection had a sensitivity 85%, specificity 52%, positive predictive value 92%, negative predictive value 33% and diagnostic accuracy 81% for significant CAD. There was a better positive predictive value in men (95% vs. 80%) and negative predictive value in women (65% vs. 16%), while a higher sensitivity and diagnostic accuracy was found in older than in younger (90% and 86% vs. 78% and 74%). The sensitivity of the method increased with the number of the diseased vessels.

CONCLUSIONS

Coronary calcium can be quite accurately detected by digital cinefluoroscopy. This, however, should be made in the context of sex and age.

Aortic valve calcium on spiral computed tomography (dual slice mode) is associated with advanced coronary calcium in hypertensive patients

BACKGROUND

Aortic valve calcium (AVC) is common in the elderly and is associated with an increase risk of death from cardiovascular causes and of myocardial infarction. The goal of the present study was to determine whether an association exists between the presence of AVC and coronary calcium (CC) in high-risk hypertensive patients as detected by spiral computed tomography (dual slice mode) (DHCT).

DESIGN AND METHODS

Three hundred and seventy-six hypertensive patients participating in the International Nifedipine Gastrointestinal Therapeutic System (GITS) Study of Intervention as a Goal in Hypertension Treatment (INSIGHT) in our region were included (197 men and 179 women, age range 55-79 years). All underwent DHCT of the heart for CC scoring using previously published methods. A positive test for the presence of CC was defined as the presence of at least one lesion with an area of 0.5 mm and DHCT density above 90 Hounsfield units (total CC score >0). CC was considered advanced when total calcium score was >300. AVC was defined by DHCT as any detected calcified deposit in the region of the aortic valve. Patients without AVC served as the control group.

RESULTS

AVC was documented in 70 patients (36 men, 34 women; mean age 66 +/- 5 years, range 57-79 years). The age- and sex-matched non-AVC group (control group) included 306 patients (161 men, 145 women; mean age 67 +/- 5 years, range 55-75 years). There were no intergroup differences in risk factors for atherosclerosis. Significant differences were found between AVC and the control groups for mean CC score (388 +/- 754 compared with 147 +/- 307, P< 0.001) and between the presence of advanced CC and the control group (27 compared with 15%, P= 0.02). Significant differences were also found for the presence of three-vessel calcification (36 compared with 21%, P= 0.01) and the number of vessels involved (1.8 +/- 1.1 compared with 1.4 +/- 1.1, P= 0.01). Stepwise logistic regression found age [odds ratio (OR) 1.08, 95% confidence intervals (CI) 1.03-1.15), gender (OR 0.45, 95% CI 0.25-0.82) and AVC (OR 2.07, 95% CI 1.06-4.02)] to be the only variables that predict advanced CC.

CONCLUSIONS

Our study demonstrated a significant association between the presence of AVC and advanced CC on spiral computed tomography. These results strengthen earlier findings of a high association between AVC and increased risk of death from cardiovascular causes.

LDL receptor mutation genotype and vascular disease phenotype in heterozygous familial hypercholesterolaemia

Patients with homozygous familial hypercholesterolaemia (FH) caused by receptor-negative, low-density lipoprotein (LDL) receptor gene mutations have higher concentrations of LDL-cholesterol in plasma and earlier onset of cardiovascular disease (CVD) than patients homozygous for receptor-defective, LDL receptor mutations. In contrast, it is uncertain whether the severity of atherosclerotic disease differs in heterozygous FH caused by receptor-negative and receptor-defective mutations. The present authors investigated the influence of LDL receptor mutation type on the clinical phenotype in 31 patients with heterozygous FH caused by the receptor-negative, Trp23-stop mutation and in 31 patients heterozygous for the receptor defective Trp66-Gly mutation. Untreated levels of plasma LDL-cholesterol and calculated cholesterol-years score did not differ significantly between the two groups of patients. Detection of vascular disease was based on two approaches: (1) measurement of coronary calcification by spiral computed tomography (CT) scanning; and (2) ultrasonic measurement of carotid intima-media thickness (IMT). Age was significantly correlated to the presence of coronary calcification, but controlling for relevant cofactors, there was no evidence that the receptor-negative mutation caused more calcification than the receptor-defective mutation. Furthermore, carotid IMT was significantly influenced by plasma concentrations of Lp(a) and triglycerides, as well as by age, sex and smoking status, but again, there was no statistically significant effect of LDL receptor gene mutational type. The similarity in vascular phenotypes was probably caused by a similar life-long burden of LDL-cholesterol in the two groups of patients.

Combined coronary and mitral annulus calcium detection in the non-invasive diagnosis of coronary artery disease in patients with systemic hypertension

BACKGROUND

Although the presence of coronary calcium (CC) on fast spiral computed tomography (FSCT) is a powerful predictor of coronary artery disease (CAD), both the specificity and positive predictive value (PPV) of CC in CAD diagnosis are modest. Since previous studies have shown an association between mitral annular calcification (MAC) and coronary atherosclerosis, we aimed to investigate whether combined coronary and MAC detection could improve the non-invasive diagnosis of CAD.

DESIGN AND METHODS

Our study comprised 522 patients (284 men and 238 women, age ranged from 52-80 years, mean 65 +/- 6 years) who underwent FSCT of the coronaries as well as echo-Doppler examination. Among them, 97 patients had prior diagnosis of prevalent proven CAD (CAD group) while 425 patients were without clinically manifested CAD (the No CAD group).

RESULTS

The prevalence of CC in the CAD group was 95 versus 68% in the No CAD group (P = 0.001). The prevalence of MAC in CAD group was 63 versus 51% in No CAD group (P = 0.03). Sensitivity and negative predictive value (NPV) of CC as a predictor of CAD were 95 and 96% respectively, but specificity and PPV were low: 32 and 24% respectively. Sensitivity and NPV of MAC as predictors of CAD were 63 and 85% respectively; specificity and PPV, 49 and 22% respectively. Using of combined CC and MAC evaluation in the prediction led to some specificity improvement at the expense of a similar sensitivity reduction, without a considerable gain in the total accuracy of the method.

CONCLUSIONS

Coronary calcium detection on FSCT in hypertensive patients yields excellent sensitivity and NPV but relatively low specificity and PPV for clinically manifested CAD. Mitral annular calcification assessment yields a low sensitivity and specificity and its addition to CC evaluation does not improve non-invasive diagnosis of CAD.

Coronary benefits of calcium antagonist therapy for patients with hypertension

Calcium antagonists effective in lowering blood pressure are a heterogeneous group including three main classes: phenylalkylamines, benzothiazepines and dihydropyridines. Dihydropyridines have a dual mode of action upon the endothelium contributing to their beneficial antihypertensive effects: (1) direct relaxation by inhibition of smooth muscle L-type calcium current, and (2) indirect relaxation through release of nitric oxide from the vascular endothelium. Calcium antagonists may affect many calcium-dependent events in the formation of atherosclerosis such as the localized accumulation of collagen, elastin, and calcium together with monocyte infiltration and smooth muscle proliferation and migration. In the INSIGHT calcification study, the overall treatment effect of nifedipine demonstrated significant inhibition of coronary calcium progression over a three-year period. Calcium antagonists improve symptoms and reduce ischemia in hypertensive patients with ischemic heart disease. Although in placebo-controlled trials calcium antagonists demonstrated a significant reduction in cardiovascular morbidity and mortality, they may be less effective than other types of antihypertensive drugs in preventing ischemic heart disease.

Calcium channel blocker nifedipine slows down progression of coronary calcification in hypertensive patients compared with diuretics

Calcium controls numerous events within the vessel wall. Permeability of the endothelium is calcium dependent, as are platelet activation and adhesion, vascular smooth muscle proliferation and migration, and synthesis of fibrous connective tissue. Double-helix computerized tomography is a noninvasive technique that can detect, measure, and compare coronary calcification in the coronary arteries. Using this method, our objective was to determine whether administration of nifedipine once daily in lieu of diuretics in high-risk hypertensive patients will arrest or slow down the progression of coronary artery calcification. The study was designed as a side arm of INSIGHT (International Nifedipine Study: Intervention as Goal for Hypertension Therapy), aimed to show the efficacy of nifedipine once daily versus co-amilozide (hydrochlorothiazide 25 mg, amiloride 2.5 mg) in high-risk hypertensive patients. A total of 201 patients with a total calcium score of >/=10 at the onset of study who underwent an annual double-helix computerized tomography for 3 years were analyzed for efficacy. Inhibition of coronary calcium progression was significant in the nifedipine versus the co-amilozide group during the first year (3.18% versus 27%, respectively, P=0.02), not significant during the second year (28.5% versus 47%, respectively, P=0.14), and significant during the third year (40% versus 78%, respectively, P=0.02). The results point to a slower progression of coronary calcification in hypertensive patients on nifedipine once daily versus co-amilozide.

Volumetric quantification of coronary artery calcifications using dual-slice spiral CT scanner: improved reproducibility of measurements with 180 degrees linear interpolation algorithm

PURPOSE

The purpose of this work was to determine the reproducibility of coronary total calcium score (TCS) with dual-slice helical CT and compare three acquisition protocols.

METHOD

Fifty patients (59 +/- 10 years old) underwent dual-slice helical CT (collimation = 2 x 2.5 mm) and coronary angiography. Two successive scans were performed, resulting in three sets of images: pitch = 1, 360 degrees linear interpolation (LI) (A360); pitch = 1, 180 degrees LI (A180); and pitch = 1.5, 180 degrees LI (B180). TCS values, calculated using a volumetric method with a threshold of 90 HU, were compared, and the interscan variation was determined. Diagnostic performances were compared with receiver operating characteristic curves.

RESULTS

Protocol A360 provided significantly lower TCS than protocols A180 and B180 (p < 0.0001). No statistical difference was seen between A180 and B180, which provided the lowest interscan variation (40 +/- 58%). However, no significant clinical impact of the observed interscan variations was found.

CONCLUSION

Reproducibility of TCS with dual-slice helical CT is improved by the 180 LI algorithm. However, dual-slice helical CT is not sufficiently reproducible to allow serial quantification of TCS over time.

Usefulness of spiral computed tomography (dual-slice mode) for the detection of coronary artery calcium in patients with chronic atypical chest pain, in typical angina pectoris, and in asymptomatic subjects with prominent atherosclerotic risk factors

The prevalence and extent of coronary calcium were retrospectively assessed by spiral computed tomography in 541 patients (mean age 62 +/- 9 years), of whom 101 had typical angina pectoris, 307 had atypical chest pain, and 133 were asymptomatic subjects with prominent atherosclerotic risk factors. The highest prevalence of coronary calcium was in men with angina pectoris (89%), whereas it was not detected in 48% of men and 56% of women with atypical chest pain.

Tracking coronary calcification by using dual-section spiral CT: a 3-year follow-up

PURPOSE

To investigate the accuracy of dual-section spiral computed tomography (CT) in tracking the progression of coronary calcification, as measured during a 3-year follow-up.

MATERIALS AND METHODS

Two hundred forty-six patients with hypertension (mean age, 66 years +/- 6 [SD]) were preselected in accordance with the International Nifedipine Study Intervention as a Goal for Hypertension Therapy protocol. Subjects had no clinical coronary arterial disease prior to the study and no cardiovascular events during follow-up. All participants underwent baseline CT (3.2-mm section thickness; reconstruction increment, 1.5 mm) and follow-up CT after 3 years. Calcification progression was defined as any increase in total calcification score (TCS) and analyzed in accordance with five baseline TCS categories: 1-9, 10-35, 36-100, 101-250, and greater than 250.

RESULTS

At baseline CT, 152 patients had a TCS greater than 0, and 106 (70%) showed progression after 3 years, while 94 had a baseline TCS of 0; of these, 26 (28%) showed progression (P: <.01 between groups). The mean TCS was significantly higher in each baseline TCS category after 3 years. The percentage increase was negatively correlated with baseline TCS (P: <.01) and ranged from 466% in the lowest category to 38% in the highest.

CONCLUSION

Dual-section spiral CT depicts significant change in TCS over time and is useful in tracking calcified coronary atherosclerosis.

Exercise testing and electron beam computed tomography in the evaluation of coronary artery disease

OBJECTIVES

This study compared coronary artery calcium (CC) as detected by electron beam computed tomography (EBCT) with conventional stress testing in the evaluation of patients with symptoms suggestive of coronary artery disease (CAD).

BACKGROUND

Exercise electrocardiogram treadmill stress testing (treadmill-ECG) is limited by its requirement of a normal resting ECG and the ability of the patient to exercise adequately. The addition of myocardial imaging agents such as technetium improves the sensitivity and specificity but substantially increases the cost and prolongs the testing time. The use of EBCT provides a noninvasive and rapid method for identifying the presence and amount of CC, which has been shown to be related to atherosclerosis, and may provide additional information in combination with more traditional noninvasive testing methods.

METHODS

A total of 97 patients underwent technetium stress testing (technetium-stress), treadmill-ECG, and EBCT coronary scanning within three months of coronary angiography for the evaluation of chest pain.

RESULTS

The relative risk (RR) of obstructive angiographic CAD for an abnormal test was higher for EBCT (4.53) than either treadmill-ECG (1.72) or technetium-stress (1.96). The low specificity of EBCT (47%) was improved by the addition of treadmill-ECG (83%, p < 0.05).

CONCLUSIONS

Electron beam computed tomography has a higher diagnostic ability than either treadmill-ECG or technetium-stress for the detection of obstructive angiographic CAD. Electron beam computed tomography is an accurate and noninvasive alternative to traditional stress testing for the detection of obstructive CAD in symptomatic patients.

Association of coronary heart disease with age-adjusted aortocoronary calcification in patients with familial hypercholesterolaemia

OBJECTIVES

Existing algorithms of risk of coronary heart disease (CHD) do not pertain to patients with familial hypercholesterolaemia (FH), whose arteries have been exposed to hypercholesterolaemia since birth. We studied a cohort of FH patients to compare four diagnostic models of CHD: traditional risk factors of CHD (age, sex, cholesterol, hypertension, smoking and body mass index), cholesterol year score, and aortic as well as coronary calcium measured by spiral computed tomography (CT).

SUBJECTS

We invited 88 individuals with molecularly defined FH of whom 80 (91%) decided to participate.

RESULTS

Analysis of receiver operating characteristic curves showed that the age-adjusted coronary calcium score was more strongly associated with clinical manifestations of CHD than were traditional risk factors (P < 0.002), cholesterol year score (P << 0.0001), and the age-adjusted aortic calcium score (P < 0.0004).

CONCLUSIONS

Age-adjusted coronary calcium score shows promise as an indicator of CHD in FH patients.

Evaluation of subsecond gated helical CT for quantification of coronary artery calcium and comparison with electron beam CT

OBJECTIVE

Since its introduction early in the 1990s, helical CT has become the predominant technology for obtaining CT images for medical applications. Recent improvements in the temporal resolution of helical CT (subsecond) and the addition of retrospective cardiac gating are combined in this report evaluating cardiac-gated helical CT for quantifying coronary artery calcium. We compare total calcium scores determined on subsecond gated helical CT with the current reference for coronary calcium evaluation, electron beam CT.

MATERIALS AND METHODS

We compared total calcium scores obtained using a general purpose, unmodified helical CT scanner with scores obtained using electron beam CT in 36 individuals who were 68+/-11 years old (age range, 41-85 years).

RESULTS

Correlation coefficients ranged from 0.97 to 0.98 (Pearson's product moment) and from 0.95 to 0.96 (Spearman's rank order), depending on the coronary calcium scoring method used. Agreement in the classification of participants as "healthy" or "diseased" at threshold total calcium scores of 10, 100, 160, 200, 400, and 680 was, respectively, 94%, 97%, 89%, 92%, 94%, and 100% using the conventional electron beam CT scoring method and an equivalent method with helical CT.

CONCLUSION

A general purpose, current generation helical CT scanner equipped for retrospective cardiac gating can accurately quantify coronary calcium, and the results are highly correlated to scores obtained with electron beam CT. As an alternative method for measuring coronary calcium, gated subsecond cardiac helical CT offers greater availability and lower cost, thereby making population-based screening for coronary artery calcium more feasible.

Advanced mitral annular calcification is associated with severe coronary calcification on fast dual spiral computed tomography

RATIONALE AND OBJECTIVES

Mitral annular calcification (MAC) may be a form of atherosclerosis and can lead to serious clinical consequences. The possible linkage between the presence and extent of MAC and coronary calcium score on CT is unknown. The goal of the present study was to investigate whether an association between MAC and coronary calcification (CC) exists in hypertensive patients with increased cardiovascular risk.

METHODS

Five hundred twenty-two patients (284 men and 238 women, age range 52-80 years, mean 65+/-6 years), who were recruited to the INSIGHT study in the authors' region, underwent fast spiral CT of the heart as well as an echo Doppler examination. MAC was defined as advanced when the thickness of the calcium deposit was 5 mm or more; it was defined as trivial otherwise.

RESULTS

The advanced MAC group comprised 62 patients, the trivial MAC group 215 patients, and the control group (without MAC) 245 patients. The prevalence of nonsevere CC was similar among the study groups, whereas the prevalence of severe CC (total calcium score >300) and the prevalence of proven coronary artery disease were associated with the presence and extent of MAC: respectively, 12% and 15% in control patients, 18% and 20% in patients with trivial MAC, and 29% and 29% in patients with advanced MAC. Multivariate analysis identified advanced MAC as an independent variable associated with severe CC and proved coronary artery disease.

CONCLUSIONS

The results of this study demonstrated an association of advanced MAC and severe CC on spiral CT and proved coronary artery disease on the clinical level. Thus, advanced but not trivial MAC makes the noninvasive diagnosis of coronary atherosclerosis more likely and presumably could be considered as a new indication for further coronary evaluation in high-risk patients.

Noninvasive imaging for the diagnosis of coronary artery disease: focusing the development of new diagnostic technology

BACKGROUND

New tests, such as magnetic resonance imaging (MRI) and electron-beam computed tomography (CT), are being developed for the diagnosis of coronary artery disease.

OBJECTIVE

To determine the conditions that a new test must meet to be a cost-effective alternative to established imaging tests.

DESIGN

Decision model and cost-effectiveness analysis.

DATA SOURCES

Literature review and meta-analysis.

TARGET POPULATION

55-year-old men and 65-year-old women presenting with chest pain.

TIME HORIZON

Lifetime of the patient.

PERSPECTIVE

Health care policy.

INTERVENTIONS

MRI, electron-beam CT, exercise echocardiography, exercise single-photon emission CT, and coronary angiography.

OUTCOME MEASURES

Target sensitivity and specificity values for a new noninvasive test.

RESULTS OF BASE-CASE ANALYSIS

Assuming that society is willing to pay $75000 per quality-adjusted life-year (QALY) gained, a new test that costs $1000 would need a sensitivity of 94% and a specificity of 90% to be cost-effective.

RESULTS OF SENSITIVITY ANALYSIS

Assuming that society is willing to pay $50000 per QALY gained, a new test that costs $1000 or more would never be cost-effective. For a test that costs $500, the sensitivity and specificity must each be 95%.

CONCLUSIONS

New imaging techniques, such as MRI and electron-beam CT, must be relatively inexpensive and have excellent sensitivity and specificity to be cost-effective compared with other techniques for the diagnosis of coronary artery disease. Similar analyses in other areas of health care may help to focus the development of new diagnostic technology.

Imaging of coronary artery calcification. Its importance in assessing atherosclerotic disease

Coronary artery calcification is a marker for atherosclerotic disease. The calcifications frequently occur early in the disease process and often before the development of luminal narrowing or cardiac events. Electron beam CT has a high accuracy in detecting calcifications, and thus has prognostic value in predicting luminal narrowing and future cardiac events.

Accuracy of spiral computed tomography for identifying arterial and venous coronary graft patency

Late outcome after coronary artery bypass grafting (CABG) mainly depends on the status of graft patency. The recent generation of spiral computed tomography (SCT) scanners may have potential in the long-term follow-up of CABG. In this study, graft patency in patients with internal mammary (IMA) and venous CABG was investigated using SCT and angiography. Forty-nine consecutive patients (age 61 +/- 8 years, 45 men) who had undergone CABG were examined by SCT and angiography 22 +/- 6 months after CABG. In total, 134 bypass grafts (42 IMA and 92 venous grafts) were analyzed. The angiographically determined patency rate of grafts was 86% for IMA (n = 36 of 42) and 74% for venous grafts (n = 68 of 92). By SCT, 32 IMA and 64 venous grafts were diagnosed correctly as patent. Sensitivity was 89% (IMA) and 94% (venous); overall sensitivity was 92%. None of the truly occluded venous grafts was diagnosed falsely patent by SCT (specificity 100%), whereas the specificity of IMA graft visualization was somewhat lower (88%, p = NS [overall 97%]). The accuracy for a patent graft was 88% (IMA) and 96% (venous CABG, p = NS). Compared with previous studies, these data suggest that SCT using one of the recent generation scanners (single scan time 0.75 second) is a highly accurate and relatively noninvasive approach for assessing not only saphenous vein graft patency, but also IMA graft patency. To date, this technique has only limited use in visualizing graft stenosis or distal anastomosis site patency.