Severity of coronary artery calcification by electron beam computed tomography predicts silent myocardial ischemia

Severe coronary artery calcifications are associated with ischemia in patients undergoing medical therapy

BACKGROUND

The role of coronary artery calcification (CAC) detection in individuals undergoing medical therapy is controversial. These patients frequently exhibit an artificially low clinical suspicion for obstructive heart disease. Whether detection of CAC adds value to their assessment is unknown.

METHODS AND RESULTS

We conducted a cross-sectional analysis of 703 adequately treated individuals who had CAC scoring with electron beam computed tomography and myocardial perfusion imaging within 6 months. We assessed the association of risk factor analysis and CAC scoring with myocardial perfusion imaging abnormalities. Univariate associations between ischemia and male gender, low high-density lipoprotein, high body mass index, diabetes, and CAC score were noted. Despite reasonable control of blood pressure and low-density lipoprotein, the prevalence of inducible ischemia was 0.8%, 4.8%, 5.7%, 8.0%, and 15.1% across CAC scores of 0 to 10, 11 to 100, 101 to 400, 401 to 1000, and greater than 1000, respectively (P < .001 for trend). Logistic regression analysis demonstrated that, after adjustment for risk factors, the odds of ischemia was 3.0 (95% confidence interval, 1.5-5.7) in individuals with CAC scores greater than 400 compared with those with CAC scores of 400 or less.

CONCLUSIONS

The presence of a CAC score greater than 400 is associated with ischemia in a population receiving good medical therapy. The detection of significant CAC in these individuals warrants additional evaluation for ischemia.

Abdominal obesity and coronary artery calcification in young adults: the Coronary Artery Risk Development in Young Adults (CARDIA) Study

BACKGROUND

Whether abdominal obesity is related to coronary artery calcification (CAC) is not known.

OBJECTIVE

We investigated the relations of waist girth and waist-hip ratio (WHR) to CAC in 2951 African American and white young adults from the Coronary Artery Risk Development in Young Adults Study.

DESIGN

The present study was a cross-sectional and observational cohort study. Using standardized protocols, we measured CAC in 2001-2002 by using computed tomography and measured waist and hip girths in 1985-1986 (baseline), 1995-1996 (year 10), and 2001-2002 (year 15, waist girth only). CAC was classified as present or absent, whereas waist girth and WHR were placed in sex-specific tertiles.

RESULTS

After adjustment for age, sex, race, clinical center, physical activity, cigarette smoking, education, and alcohol intake, baseline waist girth and WHR were directly associated with a higher prevalence of CAC 15 y later (P for trend < 0.001 for both). The odds ratios (ORs) for CAC in the highest versus lowest tertiles of waist girth and WHR were 1.9 (95% CI: 1.36, 2.65) and 1.7 (1.23, 2.41), respectively. Waist girth and WHR at year 10 and waist girth at year 15 similarly predicted CAC. These associations persisted after additional adjustment for systolic blood pressure, fasting insulin concentrations, diabetes, and antihypertensive medication use but became nonsignificant after additional adjustment for blood lipids.

CONCLUSIONS

Abdominal obesity measured by waist girth or WHR is associated with early atherosclerosis as measured by the presence of CAC in African American and white young adults. This is consistent with an involvement of visceral fat in the occurrence of coronary artery calcium in young adults.

Relation of aortic valve calcium to myocardial ischemic perfusion in individuals with a low coronary artery calcium score

The absence of coronary artery calcium (CAC) is associated with minimal atherosclerosis. Nonetheless, morbid and mortal cardiovascular events occur in patients with low CAC. This study attempts to identify whether calcific deposits outside the coronary arteries or traditional cardiovascular risk variables are associated with myocardial ischemia in patients with low CAC scores. From 1998 to 2006, a total of 605 patients with an Agatston CAC score of 0 to 10 were referred for stress echocardiography or myocardial perfusion imaging. There was a low rate (1.2%) of myocardial ischemia. Seven of 303 patients (2.3%) had ischemia on perfusion imaging. Zero of 302 stress echocardiograms were abnormal. Traditional risk-factor analysis did not predict the presence of ischemia. No differences in age, gender, or self-reported hyperlipidemia, diabetes mellitus, tobacco use, hypertension, or family history of premature heart disease were noted. Contrary to previous belief, patients with myocardial ischemia were not younger or female. Aortic valve calcium (AVC) was associated with ischemia (p = 0.02), with a >10-fold likelihood of having ischemia detected by MPS versus those without AVC (20.0% vs 1.7%). In conclusion, a CAC score <10 is associated with a low rate of myocardial ischemia. AVC may identify a subset of patients who may be at higher risk.

Relationship and prognostic value of coronary artery calcification by electron beam computed tomography to stress-induced ischemia by single photon emission computed tomography

BACKGROUND

Stress single photon emission computed tomography (SPECT) is commonly performed in patients with abnormal electron beam computed tomography (EBCT) to define risk stratification, but the published prognostic data for patients undergoing both SPECT and EBCT are limited. The objective of the study was to examine the association and prognostic value between EBCT, coronary artery calcium score (CACS), and stress SPECT imaging.

METHODS

We identified 835 patients (age 54.8 +/- 10.0 years, 77% male) who underwent EBCT and stress SPECT within a 3-month period. Coronary artery calcium score was categorized as normal (0), minimal (1-10), mild (11-100), moderate (101-400), and severe (>400). Single photon emission computed tomography summed stress score (SSS) was categorized as normal, low risk, intermediate risk, and high risk per Cedar Sinai criteria. Average follow-up was 4.8 +/- 3.2 years. End points were all-cause death, death/myocardial infarction (MI), and death/MI/late revascularization.

RESULTS

The correlation of CACS to SSS was weak but statistically significant (r = +0.19, P < .001). The percentage of high-risk SSS increased with higher CACS scores; 4% of patients with normal EBCT and 18% with severe CACS had high-risk SSS. Coronary artery calcium score (chi2 = 11.4, P < .001), diabetes mellitus (chi2 = 4.6, P = .031), and chest pain class (chi2 = 8.7, P = .003) were independently associated with high-risk SPECT. The SSS (chi2 = 6.9, P = .009) and CACS (chi2 = 7.8, P = .005) were independently associated with mortality, as well as with both secondary end points of death/MI and death/MI/late revascularization. Only CACS predicted mortality in the 408 asymptomatic patients (chi2 = 5.2, P = .02), but these patients had an annual mortality of only 0.4% over the next 5 years.

CONCLUSIONS

In selected patients undergoing both EBCT and SPECT, CACS is weakly correlated with SPECT SSS, likely reflecting the different information provided by EBCT and SPECT. Coronary artery calcium score is independently associated with high-risk SPECT after adjustment for clinical variables. Coronary artery calcium score and SSS are complementary for the prediction of mortality in symptomatic patients. Only CACS predicted mortality in the asymptomatic patients, but they had a low annual mortality.

Noninvasive Screening for Coronary Atherosclerosis and Silent Ischemia in Asymptomatic Type 2 Diabetic Patients

Coronary artery disease (CAD) accounts for 65% to 80% of deaths in diabetic patients. The merits of screening asymptomatic type 2 diabetic patients for either (A) the presence of coronary atherosclerosis by imaging of coronary calcification using cardiac computed tomography or (B) silent ischemia by stress myocardial perfusion imaging (MPI) remain controversial. Some observers have advocated for such noninvasive screening in at least the subset of the diabetic population who have significant clinical CAD risk factors, so that the highest risk patients for future cardiac events can be identified and offered more aggressive intensive medical therapy or coronary revascularization and optimum medical therapy. Computed tomography coronary calcium scanning could be the first noninvasive screening test in these clinically high-risk diabetic patients, followed by stress MPI to detect silent ischemia in those who exhibit high coronary calcium scores.

Diagnostic and prognostic value of ambulatory ECG (Holter) monitoring in patients with coronary heart disease: a review

Silent ischemia, the most common expression of atherosclerotic heart disease, affects approximately 30-50% of patients during their activities of daily living. The present review provides a comprehensive and practical summary of current knowledge on perioperative myocardial ischemia through MEDLINE searches up to June 2005, using keywords including "silent ischemia," "transient ischemia," and "Holter monitoring." Holter monitoring (i.e., continuous ambulatory ST-segment monitoring) is an effective tool for assessing the frequency and duration of silent transient myocardial ischemia, particularly in patients who are post-acute myocardial infarction (MI), those with acute coronary syndromes (ACS), and in patients in the acute post-operative period. Holter monitoring allows for further risk stratification of patients who have a positive exercise ECG by collecting long-term ECG data on ischemic and arrhythmic events while patients perform routine activities. Both the presence and increased duration of transient ischemia as detected by continuous ST-segment Holter monitoring are associated with increased rates of coronary events and mortality. Holter monitoring may aid in the identification of patients and subgroups of patients with ACS who may derive the greatest benefit from antiplatelet and antithrombotic therapy. Indeed, many ongoing and upcoming trials of pharmacotherapy include ischemia on Holter monitoring as an endpoint.

Hybrid SPECT-CT: Integration of CT coronary artery calcium scoring and angiography with myocardial perfusion

A natural extension of current imaging paradigms for diagnosing coronary artery disease may well be the integration of CT with myocardial perfusion single-photon CT (SPECT). Although there is a wealth of clinical information regarding the utility of SPECT, the value of CT in the cardiology arena has only recently been explored. CT has the advantage of detecting coronary atherosclerosis at its earliest stages, allowing initiation of appropriate therapeutic measures well before development of obstructive coronary artery disease. However, SPECT can clarify the anatomic findings of CT based on a functional assessment of myocardial blood flow, thereby guiding management decisions. Hybrid imaging with SPECT and CT angiography may prove important from a diagnostic and therapeutic view point in several clinical scenarios, and it is likely that over the next decade fusion imaging may more precisely tailor therapy, reduce healthcare costs, and improve patient outcome.

Clinical Outcomes After Both Coronary Calcium Scanning and Exercise Myocardial Perfusion Scintigraphy

OBJECTIVES

The purpose of this work was to assess the prognosis in patients undergoing both coronary artery calcium (CAC) scanning and exercise myocardial perfusion scintigraphy (MPS).

BACKGROUND

Whereas the prognostic effectiveness of MPS is well established, recent studies indicate that quantification of CAC also predicts cardiac outcomes. However, prognostic information is not yet available upon which to guide the management of patients who have had both tests.

METHODS

We assessed the frequency of cardiac death and myocardial infarction over a mean follow-up of 32 +/- 16 months in 1,153 patients undergoing both CAC scanning and MPS. Results were compared with those from a referent cohort of 9,308 patients who had earlier undergone MPS only.

RESULTS

The frequency of myocardial ischemia rose with increasing CAC scores (p < 0.001), but ischemia was present in only 64 patients. Among the 1,089 nonischemic patients, of which only 3 (0.3%) underwent early revascularization, the annualized cardiac event rate was <1% in all CAC subgroups, including those with CAC scores >1,000. Kaplan-Meier analysis revealed similarly low cardiac event rates among nonischemic patients with CAC scores >1,000 and nonischemic patients with Bayesian coronary artery disease likelihood > or =85%. Late myocardial revascularization rates were also similar in these 2 groups.

CONCLUSIONS

Among patients with nonischemic MPS studies, high CAC scores do not confer an increased risk for cardiac events. Thus, although patients with high CAC scores may be considered for intensive medical therapy to prevent future coronary artery disease events, a normal MPS study in such patients suggests no need for more aggressive interventions.

Lack of correlation between coronary artery calcium and myocardial perfusion imaging

BACKGROUND

Coronary artery calcium (CAC) provides evidence of coronary atherosclerosis and has significant prognostic power. Although prior studies have documented a relationship between CAC and hemodynamically significant coronary artery stenosis, the results have not been conclusive.

METHODS AND RESULTS

We evaluated 126 consecutive patients who underwent electron beam computed tomography CAC scoring by use of the Agatston method and stress myocardial perfusion imaging (MPI) within 3 months of each other. The analysis revealed no correlation between absolute CAC score and age- and gender-adjusted CAC scores with MPI. Overall, 18% of patients had abnormal MPI results irrespective of their CAC.

CONCLUSION

CAC scoring and stress MPI should be thus considered complementary approaches rather than exclusionary in the evaluation of the patient at risk for coronary artery disease.

Applications of multislice computed tomography in coronary artery disease

Multislice computed tomography (MSCT) provides high accuracy for noninvasive assessment of coronary artery disease (CAD). The introduction of the latest computed tomography (CT) technology allows comprehensive evaluation of various aspects of CAD, including the coronary calcium score, coronary artery stenoses, bypass patency, and myocardial function. Other applications, such as plaque characterization, first-pass perfusion imaging, and viability imaging using delayed contrast enhancement, are still under development and may demonstrate clinical utility in the future. Further improvements in CT hardware and imaging protocols are expected that may result in improved coronary artery imaging, new applications, and a significant reduction of radiation dose.

Comparative Use of Radionuclide Stress Testing, Coronary Artery Calcium Scanning, and Noninvasive Coronary Angiography for Diagnostic and Prognostic Cardiac Assessment

Noninvasive cardiac imaging has undergone a recent resurgence with the development of new approaches for imaging coronary atherosclerosis. Non-contrast computed tomography (CT) for imaging the extent of coronary artery calcification (CAC) and contrast CT for noninvasive coronary angiography (CTA) are developments with a growing evidence base regarding risk assessment and the diagnosis of obstructive coronary disease. This review discusses the role of CAC for risk assessment of asymptomatic individuals and for the use of coronary CTA in symptomatic patients. By comparison, gated myocardial perfusion scintigraphy (MPS) is a well-established noninvasive imaging modality that is a core element in evaluation of patients with stable chest pain syndromes. Stress MPS is the most commonly used stress imaging technique for patients with suspected or known coronary disease. In contrast to the nascent evidence noted with coronary CTA, MPS has a robust evidence base, including the support of numerous clinical guidelines. We highlight the current evidence supporting the diagnostic accuracy and risk stratification data for MPS for symptomatic patients with known or suspected coronary artery disease. It is likely that assessing the extent of atherosclerosis using CAC or coronary CTA will become an increasing part of mainstream cardiovascular imaging practices. In some patients, further ischemia testing with MPS will be required. Similarly, in some patients referred for MPS, anatomic definition of atherosclerosis using CAC by CT may be appropriate. Thus, this review also provides a synopsis of the available literature on imaging that integrates both CT and MPS in combined strategies for the assessment of atherosclerotic and obstructive coronary disease burden. We also propose possible risk-based strategies through which imaging might be used to identifying candidates for more intensive prevention and risk factor modification strategies as well as those who would benefit from referral to coronary angiography and revascularization.

Coronary artery disease screening, treatment, and follow-up

Heart disease causes more than 30% of US deaths. Evidence-based screening allows a primary care physician to identify patients at risk before symptom onset. Estimating disease probability before screening affects which tests are appropriate. Low-risk adults should not be screened. ECG, exercise treadmill testing, cardiac stress imaging, electron beam computed tomography, and angiography are possible screening tests. Special populations may have additional screening indications. Management of patients who have coronary artery disease includes antiplatelet therapy; aggressive lipid lowering; management of hypertension with beta blockers and angiotensin-converting enzyme inhibitors; risk factor management, including smoking cessation, diet, and exercise; symptom management; and sometimes revascularization. Primary care physicians are well-suited to the monitoring and care of patients who have known coronary artery disease.

Relationship between coronary artery calcification detected by electron-beam computed tomography and abnormal stress echocardiography: association and prognostic implications

OBJECTIVES

The purpose of this study was to compare the results and prognostic value of electron-beam computed tomography (EBCT) and exercise echocardiography.

BACKGROUND

Although patients with elevated coronary artery calcium scores (CACS) might be referred for exercise echocardiography, the association of EBCT CACS with wall motion score index (WMSI) is not known.

METHODS

Patients without known coronary artery disease who underwent both clinically indicated EBCT and exercise echocardiography within a 3-month period were identified. Exercise WMSI was based on a 16-segment model (normal = 1; abnormal >1). The EBCT CACS was derived with the Agatston scoring system. Follow-up was obtained for the combined end point of death and myocardial infarction.

RESULTS

The study population included 556 patients (age 54 +/- 10 years; 65% male). Correlation between EBCT CACS and exercise WMSI was limited (r = 0.17, p < 0.0001) but statistically significant. The proportion of patients with abnormal exercise WMSI increased with increasing CACS severity (chi-square = 19.1, p < 0.001). However, even in those with CACS >400, 66% had normal exercise WMSI. Age, CACS, and chest pain were independently associated with abnormal exercise WMSI. Events occurred in 12 (2%) patients. Wall motion score index (risk ratio [RR] 3.7, p = 0.023) and age (RR 1.9, p = 0.019) were associated with events.

CONCLUSIONS

Electron-beam computed tomography CACS was predictive of abnormal exercise WMSI, but the majority of patients with elevated CACS had normal WMSI. Wall motion score index and age were the best predictors of events. Prospective studies are indicated to establish the relative roles of these tests in risk stratification.

Coronary artery calcification and myocardial perfusion in asymptomatic adults: the MESA (Multi-Ethnic Study of Atherosclerosis)

OBJECTIVES

This study assessed the cross-sectional association between coronary artery calcification (CAC) and myocardial perfusion in an asymptomatic population.

BACKGROUND

Clinical studies showed that the prevalence of stress-induced ischemia increased with CAC burden among patients with coronary heart disease (CHD). Whether an association between CAC and myocardial perfusion exists in subjects without a history of CHD remains largely unknown.

METHODS

A total of 222 men and women, ages 45 to 84 years old and free of CHD diagnosis, in the Minnesota field center of the MESA (Multi-Ethnic Study of Atherosclerosis) were studied. Myocardial blood flow (MBF) was measured using magnetic resonance imaging during rest and adenosine-induced hyperemia. Perfusion reserve was calculated as the ratio of hyperemic to resting MBF. Agatston CAC score was determined from chest multidetector computed tomography.

RESULTS

Mean values of hyperemic MBF and perfusion reserve, but not resting MBF, were monotonically lower across increasing CAC levels. After adjusting for age and gender, odds ratios (95% confidence intervals) of reduced perfusion reserve (<2.5) for subjects with CAC scores of 0, 0.1 to 99.9, 100 to 399, and > or =400 were 1.00 (reference), 2.16 (0.96 to 4.84), 2.81 (1.04 to 7.58), and 4.99 (1.73 to 14.4), respectively. Further adjustment for other coronary risk factors did not substantially modify the association. However, the inverse association between perfusion reserve and CAC attenuated with advancing age (p for interaction < 0.05).

CONCLUSIONS

Coronary vasodilatory response was associated inversely with the presence and severity of CAC in asymptomatic adults. Myocardial perfusion could be impaired by or manifest the progression to subclinical coronary atherosclerosis in the absence of clinical CHD.

Low blood flow estimates in lower-leg arteries predict cardiovascular events in Japanese patients with type 2 diabetes with normal ankle-brachial indexes

OBJECTIVE

To examine the association of baseline measures in lower-leg arteries and conventional cardiovascular risk factors with the incidence of cardiovascular disease (CVD) events in type 2 diabetic patients with normal ankle-brachial indexes (ABIs) (>0.9).

RESEARCH DESIGN AND METHODS

We studied 129 type 2 diabetic patients and 35 age-matched nondiabetic subjects with no apparent CVD consecutively admitted to our hospital. At baseline, total flow volume and resistive index, as an index of vascular resistance, at the popliteal artery was evaluated using gated two-dimensional cine-mode phase-contrast magnetic resonance imaging. Patients were followed 4.8 +/- 1.5 years (range 3.0-8.2) or until their first event of CVD.

RESULTS

On follow-up, 16 patients developed primary CVD events. Patients with CVD had lower blood flow (P < 0.01) and higher vascular resistance (P < 0.05) than patients without CVD. When the patients were grouped into tertiles according to their levels of total flow volume (129.6-85.5, 85.3-63.3, and 62.7-23.8 ml/min), Kaplan-Meier analysis showed a higher probability of developing CVD events in patients in the lowest than in patients in the highest (P = 0.0199, log-rank test) tertile. Multivariate Cox proportional hazards analysis revealed that the lowest tertile for flow volume (hazard ratio [HR] 8.60, 95% CI 1.61-45.97, P = 0.012), hypertension (3.99, 1.12-14.25, P = 0.033), and smoking status (12.01, 1.21-119.28, P = 0.034) were significant independent predictors of CVD events.

CONCLUSIONS

We have demonstrated that low blood flow estimates in lower-leg arteries may be predictive for CVD events among Japanese patients with type 2 diabetes even though they have a normal ABI.

Analysis of coronary calcifications versus Framingham and PROCAM risk assessment in patients with a first myocardial infarction

We compared the extent of coronary calcifications as quantified by electron beam tomography (EBT) to the predicted 10-year cardiovascular event risk based on Framingham and PROCAM algorithms in patients with a first myocardial infarction (MI).

METHODS

In 156 patients (56.7 +/- 22 years), EBT was performed <4 weeks after MI. Coronary calcifications were quantified using the "Agatston Score" and age-related calcium percentiles were determined. The predicted 10-year event risk was determined using Framingham and PROCAM algorithms.

RESULTS

Coronary calcifications were present in 148 patients with a mean "Agatston Score" of 589.2 +/- 976. The "Agatston Score" was >400 in 44% and >90th percentile in 42% of the patients. Framingham risk was >20% in 32% and PROCAM risk was >20% in 28%.

CONCLUSION

Coronary calcifications were detected in the vast majority of patients with a first MI, independent from the patient's age. The determination of age-related percentiles was superior to the Framingham or PROCAM algorithm.

Coronary artery calcium scanning: Clinical paradigms for cardiac risk assessment and treatment

BACKGROUND

Coronary artery calcium (CAC) scanning is being increasingly used for cardiac risk assessment in asymptomatic patients, particularly in those with a Framingham 10-year risk of 10% to 20%. Physician awareness of this technology and its appropriate uses and limitations is crucial to appropriate use.

METHODS

With the goal of establishing clinical paradigms, this document integrates the results of key published articles, Framingham Risk Score, National Cholesterol Education Program Adult Treatment Plan III guidelines, American College of Cardiology/American Heart Association exercise testing and angiographic guidelines, and the authors' extensive clinical experience.

RESULTS

Coronary artery calcium scanning is best used in the asymptomatic population with a 10% to 20% risk of cardiac events over 10 years, with selected application in higher and lower risk categories. In the 10%-20% risk patient, coronary artery calcium scores >100 or >75th percentile for age and sex transform the moderately high-risk patient to higher risk status with the attendant recommendation for more aggressive therapy; scores from 11 to 100 and <75th percentile are consistent with the 10%-20% 10-year risk status and scores from 0 to 10 and <75th percentile convert the patient to lesser risk categories. If stress testing is planned in the asymptomatic patient, it should be preceded by coronary artery calcium scanning and performed only for scores >400; it should always precede coronary angiography in these patients.

CONCLUSIONS

Coronary artery calcium scanning is an important risk assessment tool with direct clinical applications; it is of particular utility in the Framingham 10%-20% 10-year risk population.

The value of computed tomography-derived coronary artery calcification score in coronary artery disease detection in asymptomatic hemodialysis patients

BACKGROUND

We evaluated the value of coronary artery calcification (CAC) score in coronary artery disease (CAD) detection in asymptomatic hemodialysis (HD) patients by evaluating the association among CAC score, exercise electrocardiography (EECG), and Thallium-201 dipyridamole scintigraphy. Correlation between aortic pulse wave velocity (PWV) and CAC score was also evaluated.

METHODS

CAC score was assessed with conventional computed tomography in 40 patients. Thirty patients completed EECG and 25; those with a positive CAC score and/or a positive EECG performed Thallium dipyridamole scintigraphy. Carotid-femoral PWV was assessed in all patients.

RESULTS

There was no association among CAC score and EECG or Thallium dipyridamole scintigraphy. In contrast, CAC score was correlated with aortic PWV.

CONCLUSION

The previous results question the role of CAC score in the detection of CAD in asymptomatic HD patients. The correlation between CAC score and aortic PWV raises the possibility that CAC score represents more an indicator of coronary artery medial wall calcification than a marker of CAD.

Risk stratification in uncomplicated type 2 diabetes: prospective evaluation of the combined use of coronary artery calcium imaging and selective myocardial perfusion scintigraphy

AIMS

To determine the prevalence and clinical predictors of subclinical atherosclerosis and myocardial ischaemia in uncomplicated type 2 diabetes and assess their relationship to short-term outcome.

METHODS AND RESULTS

Established risk factors and coronary artery calcium (CAC) scores were prospectively measured in 510 asymptomatic type 2 diabetic subjects (mean age 53+/-8 years, 61% males) without prior cardiovascular disease. Myocardial perfusion scintigraphy (MPS) was performed in all subjects with CAC > 100 Agatston units (AU) (n=127), and a random sample of the remaining patients with CAC < or = 100 AU (n=53). Significant CAC (> 10 AU) was found in 46.3%. Twenty events occurred (two coronary deaths, nine non-fatal myocardial infarctions, three acute coronary syndromes, three non-haemorrhagic strokes, and three late revascularisations) during a median follow-up of 2.2 years (25th-75th percentile = 1.9-2.5 years). The age, systolic blood pressure, the duration of diabetes, United Kingdom Prospective Diabetes Study risk score, CAC score, and extent of myocardial perfusion abnormality were significant predictors of time to cardiovascular events in a univariable Cox proportional hazard model. No cardiac events or perfusion abnormalities occurred in subjects with CAC < or = 10 AU up until 2 years of follow-up. CAC and MPS findings were synergistic for the prediction of short-term cardiovascular events.

CONCLUSION

Subclinical atherosclerosis, measured by CAC imaging, is superior to the established cardiovascular risk factors for predicting silent myocardial ischaemia and short-term outcome. Further studies evaluating the impact of CAC imaging on clinical outcomes and its cost effectiveness are warranted.

Comparison of coronary calcium and stress myocardial perfusion imaging in apparently healthy siblings of individuals with premature coronary artery disease

Detection of subclinical coronary atherosclerosis is possible using exercise myocardial perfusion imaging for inducible ischemia or multidetector computed tomography for coronary artery calcium (CAC), which is used to detect subclinical coronary atherosclerosis. The extent to which these screening tests converge in an asymptomatic population that is at increased risk for coronary artery disease remains unknown. We compared the concordance of findings in 260 asymptomatic middle-age siblings of hospitalized index patients <60 years of age with documented coronary artery disease. All subjects underwent maximal exercise testing with postexercise and delayed attenuation-corrected thallium single-photon emission computed tomography and multidetector computed tomography for CAC. An abnormal exercise single-photon emission computed tomographic (SPECT) result occurred in >50% of subjects with a CAC score >100, but also in 12% with no CAC, 9% with CAC scores of 1 to 10, and 20% with CAC scores of 11 to 100. In subjects with an abnormal exercise SPECT result, 59% had CAC scores < or =100. Overall, there was only a modest agreement between an abnormal exercise SPECT result and high CAC scores. In conclusion, although moderate or severe CAC is often associated with inducible ischemia, the absence of CAC or the presence of only mild CAC by no means precludes inducible myocardial ischemia. These screening tests may reflect different aspects or stages of coronary disease in an asymptomatic middle-age population.

Clinical utility of coronary calcium scoring after nonischemic myocardial perfusion imaging

BACKGROUND

Coronary artery calcium (CAC) scoring is increasingly being used after myocardial perfusion imaging (MPI) to detect preclinical coronary artery disease (CAD). However, there are few data to support this approach.

METHODS AND RESULTS

We reviewed 200 consecutive patients without known CAD who were referred for CAC scoring shortly after nonischemic MPI. Of these, 13 (6.5%) had CAC scores greater than 400, indicating significant CAD; 22 (11%) had CAC scores of 101 to 400; 27 had CAC scores of 11 to 100; and the remainder (n = 138) has CAC scores of 1 to 10. Traditional risk factors and patient characteristics were not significant predictors of CAC scores of 101 or greater. However, age and the Framingham risk score were predictors of CAC scores greater than 0. At follow-up, significantly more patients with CAC scores of 101 or greater had been given the advice to take lipid-lowering medication and aspirin compared with those with CAC scores of 0.

CONCLUSIONS

Of patients referred for CAC scoring after nonischemic MPI, 17.5% were identified as having CAD based on a CAC score greater than 100, allowing intervention with aggressive medical therapy. Patients who were reclassified were not easily identifiable by traditional risk factors, but Framingham risk score did predict the presence of CAC. Clinicians modified medical therapy based on the results of CAC scoring.

Ischemia imaging and plaque imaging in diabetes: complementary tools to improve cardiovascular risk management

Cardiovascular disease is the most frequent cause of death and disability in diabetes, and the morbidity and mortality for coronary artery disease (CAD) in this population is two to four times higher than in nondiabetic subjects. Traditional risk factors do not fully explain the level of cardiovascular risk, and coronary disease events are often silent in diabetic patients. Thus, research has recently focused on improving the risk assessment of an individual patient with new tools in an effort to better identify subjects at highest risk and in need of aggressive management. Cardiovascular imaging has proven very helpful in this regard. Traditional methods to assess CAD are based on detection of obstructive luminal disease responsible for myocardial ischemia. However, acute coronary syndromes often occur in the absence of luminal stenoses. Hence, the utilization of imaging methodologies to visualize atherosclerosis in its presymptomatic stages has received mounting attention in recent years. In this article, we review the current literature on the utility of traditional imaging modalities for obstructive CAD (nuclear and echocardiographic stress testing) as well as atherosclerosis plaque imaging with carotid intima-media thickness and coronary artery calcium for risk stratification of diabetic patients.

Relation of coronary atherosclerosis determined by electron beam computed tomography and plasma levels of n-terminal pro-brain natriuretic peptide in a multiethnic population-based sample (the Dallas Heart Study)

Elevated plasma levels of B-type natriuretic peptide (BNP) and N-terminal pro-BNP (NT-pro-BNP) are seen in the setting of cardiac ischemia and are associated with adverse outcomes in patients with coronary artery disease. The mechanisms leading to natriuretic peptide elevation in patients with coronary artery disease, including the contribution of coronary atherosclerosis itself, have not been fully elucidated. Measurement of NT-pro-BNP, electron beam computed tomography, and cardiac magnetic resonance imaging were performed in 2,445 subjects from the Dallas Heart Study who were free of heart failure and renal insufficiency. Electron beam computed tomography-determined coronary artery calcium scores were categorized as none (<10), mild (> or =10 to <100), moderate (> or =100 to <400), and severe (> or =400). NT-pro-BNP levels increased significantly across increasing coronary artery calcium score categories (p <0.0001 for trend). In multivariate models adjusted for age, gender, race, body mass index, hypertension, history of myocardial infarction, angina, angiotensin-converting enzyme inhibitor use, beta-blocker use, left ventricular (LV) ejection fraction, and LV mass, higher coronary artery calcium scores remained independently associated with higher log NT-pro-BNP levels (p = 0.03). This association persisted in similar models excluding patients with low LV ejection fractions, LV hypertrophy, angina pectoris, and a history of myocardial infarction. In conclusion, these findings support the hypothesis that coronary atherosclerosis may directly influence the activation of the cardiac neurohormonal system.

Role of electron-beam computed tomography and nuclear stress testing in cardiovascular risk assessment

Although it is well recognized that stenotic coronary artery lesions carry a significant risk for cardiac events, the importance of nonstenotic lesions is generally underappreciated. However, many acute myocardial infarctions are caused by lesions that cause <50% stenosis. Coronary artery calcification is being increasingly studied as a marker of risk for cardiac events. Measurement of coronary artery calcium using electron-beam computed tomography is emerging as a useful tool to further risk-stratify patients who are otherwise at intermediate risk for events. Coronary calcium scores have been shown to add independent predictive value to traditional risk assessment.

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.

Differential effects of 17beta-estradiol and raloxifene on VSMC phenotype and expression of osteoblast-associated proteins

Several studies demonstrate an association between osteoporosis and arterial calcific disease, both of which being common in elderly women. Estradiol and raloxifene, a selective estrogen receptor modulator, prevent bone loss in postmenopausal women. Little is known regarding how these agents affect arterial calcification. The aim of this study was to determine whether or not 17beta-estradiol and raloxifene reduced vascular smooth muscle cell (VSMC) differentiation and expression of bone-associated proteins during phosphate-induced calcification in vitro. Aortic VSMC were cultured from adult, gonadally intact, and ovariectomized (OVX) female pigs. Calcifying medium was added, and cells were treated with solvent (control), 17beta-estradiol (E(2)), or raloxifene. Extent of calcification and phenotypic expression of bone-associated proteins [matrix gla protein (MGP), osteoprotegerin (OPG), and bone sialoprotein (BSP)] were examined at 3-day intervals over 2 wk. Calcium content increased in all groups but was greater in VSMC derived from intact compared with OVX animals. E(2) reduced calcification and preserved a contractile phenotype. Expression of OPG significantly decreased with time; this decrease was significantly greater in VSMC derived from OVX compared with gonadally intact pigs. E(2) and raloxifene preserved expression of OPG only in VSMC from intact pigs. Expression of MGP increased significantly with time and was not affected by E(2) or raloxifene treatments. E(2) treatment significantly inhibited synthesis of BSP in cells from both groups. In conclusion, E(2) slows differentiation of VSMC induced by excess phosphate. Effectiveness of raloxifene to preserve expression of bone cell-associated proteins depends on the hormonal status of the tissue donor.

Metabolic syndrome and diabetes are associated with an increased likelihood of inducible myocardial ischemia among patients with subclinical atherosclerosis

OBJECTIVE

Coronary artery calcification (CAC) is associated with cardiac events and the likelihood of inducible myocardial ischemia. Because metabolic syndrome contributes to atherosclerosis, we assessed whether it also influences the relationship between CAC levels and myocardial ischemia.

RESEARCH DESIGN AND METHODS

We evaluated 1,043 patients without known coronary artery disease (CAD) who underwent stress myocardial perfusion scintigraphy (MPS) and computed tomography. Metabolic syndrome was defined by modified National Cholesterol Education Program criteria. Metabolic abnormalities were present in 313 patients (30%), including 140 with diabetes (with or without metabolic syndrome) and 173 who had metabolic syndrome without diabetes.

RESULTS

Although CAC scores <100 identified a low likelihood ( approximately 2%) of ischemia, the presence (versus absence) of metabolic abnormalities (metabolic syndrome or diabetes) was a predictor of more frequent ischemia among patients with CAC scores of 100-399 (13.0 vs. 3.6%, P < 0.02) and CAC scores >/=400 (23.4 vs. 13.6%, P = 0.03). Similar trends were observed when patients with metabolic syndrome and diabetes were considered separately. Multiple logistic regression revealed the odds of MPS ischemia to be 4.3-fold greater per SD of log CAC (P < 0.001) and 2.0-fold greater in the presence of metabolic abnormalities (P < 0.01).

CONCLUSIONS

Among patients with CAC scores >/=100, metabolic abnormalities, and even metabolic syndrome in the absence of diabetes predicted a higher likelihood of inducible ischemia. These findings suggest the need for assessment of metabolic status when interpreting the results of CAC imaging among patients undergoing such testing because of suspected CAD.

Silent myocardial ischemia: Recent developments

Silent myocardial ischemia is now in its fourth decade of recognition as a clinical syndrome within the spectrum of coronary artery disease. Prior decades have seen important research into the pathophysiology, detection, prevalence, prognosis, and therapy of this syndrome. More recent developments have continued to add data to each of these areas, with particular emphasis on the comparative value of various diagnostic procedures and the effect of therapy on prognosis. While controversy still exists concerning proper screening guidelines for the asymptomatic population, there is a growing consensus that some form of stress testing in high-risk individuals (ie, those with multiple coronary risk factors) is appropriate.

Coronary artery calcification score by multislice computed tomography predicts the outcome of dobutamine cardiovascular magnetic resonance imaging

The aim of this study was to determine whether a coronary artery calcium (CAC) score of less than 11 can reliably rule out myocardial ischemia detected by dobutamine cardiovascular magnetic resonance imaging (CMR) in patients suspected of having myocardial ischemia. In 114 of 136 consecutive patients clinically suspected of myocardial ischemia with an inconclusive diagnosis of myocardial ischemia, dobutamine CMR was performed and the CAC score was determined. The CAC score was obtained by 16-row multidetector compued tomography (MDCT) and was calculated according to the method of Agatston. The CAC score and the results of the dobutamine CMR were correlated and the positive predictive value (PPV) and the negative predictive value (NPV) of the CAC score for dobutamine CMR were calculated. A total of 114 (87%) of the patients were eligible for this study. There was a significant correlation between the CAC score and dobutamine CMR (p<0.001). Patients with a CAC score of less than 11 showed no signs of inducible ischemia during dobutamine CMR. For a CAC score of less than 101, the NPV and the PPV of the CAC score for the outcome of dobutamine CMR were, respectively, 0.96 and 0.29. In patients with an inconclusive diagnosis of myocardial ischemia a MDCT CAC score of less than 11 reliably rules out myocardial ischemia detected by dobutamine CMR.

Should we screen for occult coronary artery disease among asymptomatic patients with diabetes?

Diabetes mellitus predisposes people to premature atherosclerotic coronary artery disease (CAD). The risk of a myocardial infarction in diabetics without overt evidence of obstructive CAD matches that of patients without diabetes who have had a previous myocardial infarction. The available data suggest that occult CAD is a common finding among asymptomatic diabetics, ranging from 20% to >50%. The diagnostic accuracy of myocardial perfusion single-photon emission computed tomography (SPECT) in diabetics appears to be comparable to that observed in nondiabetic individuals. As shown in other patient groups, the ischemic burden assessed by stress SPECT in subjects with diabetes is also linked to their increased risk of adverse cardiovascular events. Among patients with normal stress SPECT, however, those with diabetes are at significantly greater risk than non-diabetics. Testing diabetics with an abnormal resting electrocardiogram or with evidence of peripheral or carotid occlusive arterial disease appears to result in an excellent yield of abnormal SPECT findings, as does testing in the setting of dyspnea. However, recent evidence suggests that achieving an adequate yield in asymptomatic diabetics without overt evidence of CAD is a greater challenge. Further investigation of sequential testing strategies is needed in order to identify an efficient means for screening asymptomatic patients with diabetes.

Diagnostic Value of Simultaneous Brachial and Ankle Blood Pressure Measurements for the Extent and Severity of Coronary Artery Disease as Assessed by Myocardial Perfusion Imaging

BACKGROUND

Although the simultaneous measurement of brachial and ankle blood pressure is a simple method of evaluating atherosclerosis, its diagnostic value for coronary artery disease (CAD) is undetermined.

METHODS AND RESULTS

To evaluate the diagnostic value of ankle-brachial pressure index (ABI) and brachial-to-ankle pulse wave velocity (baPWV), 334 consecutive patients with suspected CAD were evaluated. Patients with a previous myocardial infarction or coronary intervention were not included. The magnitude of myocardial ischemia was evaluated by myocardial perfusion imaging. Using a 20-segment model, the percent of ischemic segments to total segments was expressed as %myocardium ischemic. In patients with < or =1, 2 and > or =3 coronary risk factors, %myocardium ischemic was 2.7+/-0.4, 4.0+/-0.5, 7.9+/-0.8%, respectively (p<0.0001 for trend). Performing ABI with a cutoff of 1, the %myocardium ischemic was similar in patients with < or =1 or 2 risk factors. In patients with > or =3 coronary risk factors, however, an ABI <1 reflected greater %myocardium ischemic than an ABI > or =1 (10.1+/-1.3, 6.6+/-1.0%; p=0.03). No such additional value was observed with baPWV.

CONCLUSIONS

The addition of simultaneous brachial and ankle blood pressure measurements will help further stratify patients with multiple risk factors. Although this approach is simple, it facilitates the identification of high-risk patients who require aggressive treatment because >10% myocardium ischemic is regarded as a scintigraphic indicator for coronary revascularization.

Computed tomography coronary calcium screening and myocardial perfusion imaging

Cardiac computed tomography (CT) has seen an exponential increase in interest as applications expanded from identification of coronary artery calcification to noninvasive coronary angiography and, more recently, identification of soft and noncalcified plaques. The interest arises from the well-known fact that cardiovascular disease remains the most prevalent cause of death in the Western hemisphere and the fact that in a large proportion of patients the initial event is either sudden death or a disabling myocardial infarction or stroke. Although traditional risk factors are extremely helpful in determining risk in a population, the prognostic ability of risk factors alone in the individual patient is limited. Hence, researchers have turned their attention to noninvasive modalities to image the atherosclerotic plaque in its preclinical stages, hoping to better address this ailment at its inception and change the natural history of the disease. Measurements of coronary artery calcium (CAC) serve as a quantitative reflection of the severity of coronary artery atherosclerosis, and greater calcium burdens correlate with more advanced disease. Indeed, CAC has been shown to add prognostic value to traditional risk factors in patients at intermediate risk, and in this group of patients, it is most cost-effective. Furthermore, CAC measurements providing an assessment of coronary atherosclerotic plaque burden appear to be complementary to myocardial perfusion single photon emission computed tomography that offers information regarding inducible ischemia. In this manner, a better assessment of risk in a patient suspected of harboring preclinical or early coronary artery disease can be achieved. In this article we review the most relevant literature regarding the utilization of CAC testing as a tool to refine risk assessment and use several case studies to exemplify the combination of CT imaging and functional myocardial perfusion studies, which may provide a better identification of patients in need of aggressive medical therapy and those needing invasive assessment for possible coronary revascularization.

Stiffness and impaired blood flow in lower-leg arteries are associated with severity of coronary artery calcification among asymptomatic type 2 diabetic patients

OBJECTIVE

To clarify whether stiffness and impaired blood flow in lower-leg arteries are associated with severity of coronary artery calcification among asymptomatic diabetic patients.

RESEARCH DESIGN AND METHODS

We enrolled 102 asymptomatic type 2 diabetic patients with no history of cardiovascular complications consecutively admitted to our hospital. Agatston coronary artery calcium (CAC) score, as a marker of coronary artery calcification, was obtained using electron-beam computed tomography. Total flow volume and resistive index, as an index of vascular resistance, at the popliteal artery were evaluated using gated two-dimensional cine-mode phase-contrast magnetic resonance imaging. Brachial-ankle pulse-wave velocity (PWV), as an index of distensibility in the lower-extremity arteries, was also measured using an automatic device.

RESULTS

When the patients were grouped according to CAC scores of 0-10 (n = 54), 11-100 (n = 25), and > 100 (n = 23), those with the highest scores, which is considered to show possible coronary artery disease, showed the highest brachial-ankle PWV (P < 0.001) and resistive index (P < 0.001) and the lowest total flow volume (P < 0.001) among the groups. Simple linear regression analyses showed that both brachial-ankle PWV (r = 0.508, P < 0.001) and resistive index (r = 0.500, P < 0.001) were positively correlated and total flow volume (r = -0.528, P < 0.001) was negatively correlated with the log-transformed CAC score. Receiver operator characteristic curve analyses indicated that 1,800 cm/s for brachial-ankle PWV, 1.03 for resistive index, and 70 ml/min for total flow volume were diagnostic values for identifying patients with the highest scores.

CONCLUSIONS

Quantitatively assessed stiffness and impaired blood flow in lower-leg arteries may help identify diabetic patients with possible coronary artery disease.

Relationship between stress-induced myocardial ischemia and atherosclerosis measured by coronary calcium tomography

OBJECTIVES

We assessed the relationship between stress-induced myocardial ischemia on myocardial perfusion single-photon emission computed tomography (MPS) and magnitude of coronary artery calcification (CAC) by X-ray tomography in patients undergoing both tests.

BACKGROUND

There has been little evaluation regarding the relationship between CAC and inducible ischemia or parameters that might modify this relationship.

METHODS

A total of 1,195 patients without known coronary disease, 51% asymptomatic, underwent stress MPS and CAC tomography within 7.2 +/- 44.8 days. The frequency of ischemia by MPS was compared to the magnitude of CAC abnormality.

RESULTS

Among 76 patients with ischemic MPS, the CAC scores were >0 in 95%, >or=100 in 88%, and >or=400 in 68%. Of 1,119 normal MPS patients, CAC scores were >0, >or=100, and >or=400 in 78%, 56%, and 31%, respectively. The frequency of ischemic MPS was <2% with CAC scores <100 and increased progressively with CAC >or=100 (p for trend <0.0001). Patients with symptoms with CAC scores >or=400 had increased likelihood of MPS ischemia versus those without symptoms (p = 0.025). Absolute rather than percentile CAC score was the most potent predictor of MPS ischemia by multivariable analysis. Importantly, 56% of patients with normal MPS had CAC scores >or=100.

CONCLUSIONS

Ischemic MPS is associated with a high likelihood of subclinical atherosclerosis by CAC, but is rarely seen for CAC scores <100. In most patients, low CAC scores appear to obviate the need for subsequent noninvasive testing. Normal MPS patients, however, frequently have extensive atherosclerosis by CAC criteria. These findings imply a potential role for applying CAC screening after MPS among patients manifesting normal MPS.

Clinical application of genetic risk assessment strategies for coronary artery disease: genotypes, phenotypes, and family history

Individuals with genetic predisposition to atherosclerosis have an increased risk for developing coronary artery disease (CAD), especially at young ages. They may derive the greatest benefit from traditional preventive strategies and strategies targeting novel,emerging risk factors. Because CAD is a complex, multifactorial disorder, global risk assessment has been recognized as an effective approach in preventing CAD and its manifestations. The systematic collection and interpretation of family history information is currently the most appropriate screening approach to identify individuals with genetic susceptibility to CAD. Much of the familial aggregation of CAD might be explained by familial aggregation of established risk factors and emerging CAD risk factors. Tests to assess genetic risk for CAD are primarily biochemical analyses that measure the different pathways involved in development and progression of disease. Some of these can guide and explain responses to treatment.

Coronary calcium screening in asymptomatic patients as a guide to risk factor modification and stress myocardial perfusion imaging

BACKGROUND

Previous studies have demonstrated a correlation between the extent of coronary artery calcification (CAC) and atherosclerotic plaque. As a result, CAC screening could be useful in predicting cardiovascular risk in individuals in whom atherosclerosis is developing. One possible method of detecting and quantifying CAC is by x-ray computed tomography, which potentially allows one to stratify patients into groups requiring risk factor modification or follow-up testing such as myocardial perfusion single photon emission computed tomography (SPECT).

METHODS AND RESULTS

This study was designed to evaluate the clinical utility of multidetector computed tomography (MDCT) in a cardiology practice setting. A retrospective analysis was performed on data from 794 asymptomatic patients who underwent CAC screening over an 8-month period. On the basis of the CAC score and physician consultation, 102 patients underwent subsequent myocardial perfusion SPECT imaging. A substudy was also conducted in 306 patients to measure the interscan variability of MDCT across different CAC score ranges. CAC was detected in 422 of 794 patients. Of these, the CAC was moderate (Agatston score = 101-400) in 14% and severe (>400) in 9%. Patients with 3 or more cardiac risk factors were most likely to exhibit moderate to severe CAC. In myocardial perfusion SPECT testing, no patient with an Agatston score lower than 100 had an abnormal study. In contrast, 41% of patients with severe CAC had an abnormal SPECT study. In the reproducibility substudy the minimal CAC group had the largest variability (86.0%) whereas the severe CAC group had the lowest variability (9.5%).

CONCLUSION

CAC screening with MDCT is justified for asymptomatic patients with 3 or more cardiac risk factors. However, risk factor assessment is poor at predicting which individuals will have CAC if fewer risk factors are present. In terms of the interscan variability, MDCT is capable of following changes in CAC for patients with Agatston scores greater than 100. Finally, this study demonstrated that an Agatston score of 400 is a logical threshold to initiate follow-up myocardial perfusion SPECT testing.

Interscan variability of coronary artery calcium quantification using an electrocardiographically pulsed spiral computed tomographic protocol

The use of an electrocardiographically pulsed spiral computed tomographic protocol significantly reduced the radiation dose to patients who underwent coronary calcium screening. For Agatston scores <10, the interscan variability of such a protocol was significantly lower than that for a sequential acquisition protocol. At higher Agatston scores, the 2 protocols had similar variability characteristics.

The role of electron beam computed tomography for measuring coronary artery atherosclerosis

It is generally agreed that the coronary artery calcium score provides significant information for the prediction of future cardiac events. However, additional information is needed to determine whether or not this information is significantly greater than that available from the analysis of established risk factors. Until this is resolved, it is unlikely that electron beam computed tomography can be justified for routine evaluation of patients. However, measurement of coronary artery calcium may be valuable in selected clinical situations, and has potential as a research tool for studying the pathogenesis or treatment of stable coronary artery disease.

Relation of coronary vasoreactivity and coronary calcification in asymptomatic subjects with a family history of premature coronary artery disease

Electron-beam computed tomography (EBCT) allows non-invasive imaging of coronary calcification and has been promoted as a screening tool for coronary artery disease (CAD) in asymptomatic high-risk subjects. This study assessed the relation of coronary calcifications to alterations in coronary vascular reactivity by means of positron emission tomography (PET) in asymptomatic subjects with a familial history of premature CAD. Twenty-one subjects (mean age 51+/-10 years) underwent EBCT imaging for coronary calcifications expressed as the coronary calcium score (CCS according to Agatston) and rest/adenosine-stress nitrogen-13 ammonia PET with quantification of myocardial blood flow (MBF) and coronary flow reserve (CFR). The mean CCS was 237+/-256 (median 146, range 0-915). The CCS was <100 in eight subjects and >100 units in 13. As defined by age-related thresholds, 15 subjects had an increased CCS (>75th percentile). Overall mean resting and stress MBF and CFR were 71+/-16 ml 100 g(-1) min(-1), 218+/-54 ml 100 g(-1) min(-1) and 3.20+/-0.77, respectively. Three subjects with CCS ranging from 114 to 451 units had an abnormal CFR (<2.5). There was no relation between CCS and resting or stress MBF or CFR ( r=0.17, 0.18 and 0.10, respectively). In asymptomatic subjects a pathological CCS was five times more prevalent than an abnormal CFR. The absence of any close relationship between CCS and CFR reflects the fact that quantitative myocardial perfusion imaging with PET characterises the dynamic process of vascular reactivity while EBCT is a measure of more stable calcified lesions in the arterial wall whose presence is closely related to age.