Use of coronary calcium scanning for predicting inducible myocardial ischemia: Influence of patients’ clinical presentation

BACKGROUND

The selection of patients for cardiac stress tests is generally based on assessment of chest pain symptoms, age, gender, and risk factors, but recent data suggest that coronary artery calcium (CAC) measurements can also be used to predict inducible myocardial ischemia. However, the potential influence of clinical factors on the relationship between CAC measurements and inducible ischemia has not yet been investigated.

METHODS AND RESULTS

We prospectively performed CAC scanning in 648 patients undergoing exercise myocardial perfusion single photon emission computed tomography. The frequency of ischemia on myocardial perfusion single photon emission computed tomography was assessed according to CAC magnitude after dividing patients according to chest pain symptom class and Bayesian likelihood of angiographically significant coronary artery disease (ASCAD). Estimates of ASCAD likelihood and CAC scores were poorly correlated. The frequency of inducible myocardial ischemia was very low among patients with a low ASCAD likelihood if CAC scores were less than 400. By contrast, the threshold for increasing ischemia occurred at low CAC scores among patients with a high ASCAD likelihood. When characterized by chest pain classification, asymptomatic and nonanginal chest pain patients had a low frequency of ischemia if CAC scores were less than 400, whereas lower CAC scores did not exclude ischemia among typical angina or atypical angina patients.

CONCLUSIONS

CAC scores predict myocardial ischemia, with a threshold score of greater than 400 among patients with a low likelihood of ASCAD and those who are asymptomatic or have nonanginal chest pain. These data appear to extend the pool of patients for whom CAC scanning may be useful in ascertaining the need for cardiac stress testing.

Comparison of atherosclerotic calcification burden in persons with the cardiometabolic syndrome and diabetes

The cardiometabolic syndrome (CMS) and diabetes are associated with higher cardiovascular risk. The authors compared the association of CMS risk factors and diabetes with coronary and aortic calcium. A total of 4468 adults (42% female) underwent computed tomography for determination of coronary artery calcium (CAC) and thoracic aortic calcium (TAC) and were classified according to the presence of diabetes mellitus (DM) and number of CMS risk factors. The prevalence of CAC ranged from 51% in men and 35% in women with neither DM nor CMS to 75% in men and 58% in women with both DM and CMS, whereas TAC ranged from 29% to 44% in men and 36% to 55% in women. Women with four or five CMS risk factors more often had CAC (53%) and TAC (51%) than those with DM without CMS (40% and 35%, respectively) (p<0.001 across all disease groups). Adjusted odds (and 95% confidence intervals) of CAC for those with three CMS risk factors, four CMS risk factors, DM without CMS, and DM with CMS vs. those without CMS were 1.14 (0.93-1.39), 1.46 (1.12-1.90), 1.59 (1.06-2.38), and 2.10 (1.52-2.90) for CAC and 1.14 (0.91-1.42), 1.03 (0.77-1.37), 1.03 (0.68-1.54), and 1.41 (1.03-1.92) for TAC. Multiple CMS risk factors are associated with increased CAC, but not TAC; DM with CMS has the highest prevalence of CAC and TAC.

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.

Prognostic value of poststress left ventricular volume and ejection fraction by gated myocardial perfusion SPECT in women and men: Gender-related differences in normal limits and outcomes

BACKGROUND

Whether there are gender differences in the prognostic application of gated myocardial perfusion single photon emission computed tomography (SPECT) has not been assessed.

METHODS AND RESULTS

Gender-specific normal limits of poststress volume and ejection fraction (EF) were obtained in 597 women and 824 men with a low likelihood of coronary artery disease and normal perfusion and were applied in a prognostic evaluation of 6713 patients (2735 women and 3978 men). Patients underwent rest thallium-201/stress technetium-99m sestamibi gated myocardial perfusion SPECT and were followed up for 35 +/- 14 months. The upper limit of the end-systolic volume (ESV) index was 27 mL/m2 in women and 39 mL/m2 in men, and the upper limit of the end-diastolic volume index was 60 mL/m2 in women and 75 mL/m2 in men. The lower limit of the EF was 51% in women and 43% in men. Gated SPECT variables provided incremental prognostic information in both genders. Women with severe ischemia and an EF lower than 51% or an ESV index greater than 27 mL/m2 were at very high risk of cardiac death or myocardial infarction (3-year event rates of 39.8% and 35.1%, respectively), whereas women with severe ischemia but an EF of 51% or greater or an ESV index of 27 mL/m2 or less were at intermediate or high risk (3-year event rates of 10.8% and 15.2%, respectively).

CONCLUSION

Poststress EF and ESV index by gated myocardial perfusion SPECT provide comparable incremental prognostic information over perfusion in women and men. After separate criteria for abnormal EF and ESV index in women are used, the combination of severe ischemia and abnormal EF or ESV index identifies women at very high risk of cardiac events.

Computer-Aided Detection and Evaluation of Lipid-Rich Plaque on Noncontrast Cardiac CT

OBJECTIVE

Noncontrast electron beam CT (EBCT) and MDCT are established for the assessment of calcified plaque, but not lipid-rich plaque. We developed software to identify lipid-rich plaque with noncontrast electron beam tomography (EBT) and MDCT.

MATERIALS AND METHODS

A computer algorithm was developed to automatically find contiguous lipid-rich lesions with voxel intensities below a calculated patient-specific lipid threshold. Lipid density and lipid inhomogeneity in Hounsfield units were calculated in the proximal left coronaries of three populations: 34 low-risk patients (low-risk group < 6% Framingham risk score, no calcium), 31 high-risk patients (high-risk group > 20% Framingham risk score, no calcium), and 37 patients with calcified plaque (calcium group).

RESULTS

The mean lipid density was -19.6 +/- 3.0 (SD) H in the low-risk group, -25.3 +/- 8.2 H in the high-risk group, and -34.3 +/- 13.0 H in the calcium group (p < 0.05). The mean lipid inhomogeneity was 17.7 +/- 3.6 H in the low-risk group, 21.5 +/- 5.5 H in the high-risk group, and 29.0 +/- 7.6 H in the calcium group (p < 0.05). The mean interscan variability in lipid density and lipid inhomogeneity were 2.0 +/- 3.3 H and 2.1 +/- 3.6 H, respectively. In five patients, the locations of lipid-rich plaque correlated well with available intravascular sonography findings.

CONCLUSION

Our method may be able to identify lipid-rich plaque on noncontrast cardiac CT.

Prognostic value of myocardial perfusion SPECT versus exercise electrocardiography in patients with ST-segment depression on resting electrocardiography

BACKGROUND

The value of exercise-induced ST-segment depression for the prognostic evaluation of patients with 1 mm of ST depression or greater on the resting electrocardiogram is controversial.

METHODS AND RESULTS

Patients who underwent exercise myocardial perfusion single photon emission computed tomography (MPS) and had resting ST depression of 1 mm or greater with a nondiagnostic exercise electrocardiographic response (n = 1122) were followed up for 3.4 +/- 2.3 years. Those with paced rhythm, pre-excitation, left bundle branch block, or myocardial revascularization within the first 60 days after MPS were excluded. Additional exercise-induced ST-segment depression was considered significant if > or = 2 mm MPS was scored semiquantitatively by use of a 20-segment model of the left ventricle; the percentage of myocardium involved with stress defects (% myo) was derived by normalizing to the maximal possible score of 80. Hard events were defined as nonfatal myocardial infarction or cardiac death. A Cox analysis was used to determine independent predictors of hard events among clinical, exercise, and nuclear variables. Hard event rates increased as a function of % myo for either patients with exercise-induced ST depression (1.4%/y for normal MPS vs 4.1%/y for % myo >10%, P < .03) or those without it (0.7%/y for normal MPS vs 3.0%/y for % myo >10%, P = .0001). Age, diabetes mellitus, shortness of breath as the presenting symptom, and % myo were independent predictors of hard events. Exercise-induced ST depression was predictive of hard events only when it was 3 mm or greater. The presence and extent of perfusion defects, reflected in the % myo, had incremental prognostic value over clinical variables and also over all degrees of exercise-induced ST depression.

CONCLUSIONS

Although MPS effectively risk-stratifies patients with resting ST depression of 1 mm or greater, the prognostic value of exercise-induced ST depression is limited in these patients, with a small added risk when severe (> or = 3 mm).

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.

Social network and coronary artery calcification in asymptomatic individuals

BACKGROUND

Psychosocial factors are associated with the development of coronary artery disease. However, studies examining psychosocial factors as risk indicators for coronary artery calcification (CAC) have been inconclusive.

METHODS

Seven hundred eighty-three participants (mean age 57.4 +/- 9.3 years, 47% female) underwent CAC imaging using electron beam tomography. Psychosocial measures included social network (number of people in the household, marital status), socioeconomic status (education, income, and work status), history of depression, and current depressive symptoms as assessed with the Center for Epidemiologic Studies Depression (CES-D) scale. Assessments were also made for lipid profile, blood glucose, blood pressure, and health behaviors (smoking status, exercise, and diet).

RESULTS

Calcification was present in 351 (44.8%) participants (CAC score range 0-3022; mean 111.5 +/- 307.2). Indicators of social isolation (being single or widowed) were independently associated with elevated risk for the presence of CAC, even after adjustment for age, sex, systolic blood pressure, blood glucose, and low-density lipoprotein (adjusted odds ratios 1.80, 95% confidence interval [CI] = 1.05-3.10, and 2.48, 95% CI = 1.02-6.03, respectively). By contrast, health behaviors, socioeconomic status, and depressive symptoms were not related to CAC.

CONCLUSIONS

Social network indices such as being single or widowed are associated with CAC, independent of age and coronary risk factors. Because coronary calcification has been identified as a potential marker of early atherosclerosis, these findings may partially explain the predictive value of limited social networks for future adverse cardiovascular health outcomes.

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.