Clinical use of coronary calcium scanning with computed tomography

Midday naps and the risk of coronary artery disease: results of the Heinz Nixdorf Recall Study

STUDY OBJECTIVES

Several studies have assessed the association between midday nap and cardiovascular outcomes and reported heterogenous results. Concern exists that confounding might have distorted these results and contributed to discrepancies among them. This study prospectively examines the association between midday nap habits and the occurrence of coronary artery disease in a non-Mediterranean population.

PARTICIPANTS

The baseline examination of 4,123 participants aged 45-75 years.

MEASUREMENTS

Measurements included interviews, physical examinations, laboratory tests, and electron beam computed tomography. We studied the influence of midday nap habits on risk of coronary artery disease. We adjusted for several potential confounders including measures of subclinical atherosclerosis-such as coronary calcium score and ankle brachial index-at baseline. Cardiac events during a median follow-up of 8.1 years were defined as nonfatal myocardial infarction and sudden cardiac death.

RESULTS

Overall, 135 of 4,123 subjects (3.3%) either suffered from acute myocardial infarction (81 subjects) or died due to a sudden cardiac death (54 subjects) during follow-up. After adjustment for several confounders including measures of subclinical atherosclerosis, regular long (> 60 min) midday nap was associated with an increased hazard ratio of cardiac events (hazard ratio 2.12, 95% confidence interval 1.11-4.05).

CONCLUSIONS

As our detailed confounder analyses showed, confounding is not the sole explanation for this finding. Future research on midday naps should focus on biological mechanisms that may be responsible for increasing the risk of coronary artery disease among subjects taking regular long midday naps.

Prevalence of the metabolic syndrome is increased in rheumatoid arthritis and is associated with coronary atherosclerosis

Patients with rheumatoid arthritis (RA) have accelerated atherosclerosis. The metabolic syndrome, a cluster of cardiovascular risk factors, identifies cardiovascular risk. We tested the hypotheses that patients with RA have a higher prevalence of the metabolic syndrome, particularly the WHO-defined syndrome that requires insulin resistance, and that this is associated with coronary atherosclerosis. The prevalence of the metabolic syndrome was determined using the modified WHO and NCEP III criteria in 154 patients with RA (88 with early RA and 66 with long-standing RA) and 85 control subjects. Coronary-artery atherosclerosis was detected by electron beam computed tomography. The WHO-defined metabolic syndrome was present in 42% of patients with long-standing RA, 31% with early RA and 11% of controls (P<0.001); the NCEP-defined metabolic syndrome was present in 42% of patients with long-standing RA, 30% with early RA and 22% of controls (P=0.03). Patients with the WHO-defined metabolic syndrome had an increased risk of having higher coronary-artery calcification scores, independent of age and sex (OR=2.02, 95% CI: 1.03-3.97, P=0.04). In conclusion, patients with RA have a higher prevalence of the metabolic syndrome than control subjects. Inflammation-associated metabolic syndrome is a mechanism that may contribute to increased coronary-artery atherosclerosis in RA.

Daily siesta, cardiovascular risk factors, and measures of subclinical atherosclerosis: results of the Heinz Nixdorf Recall Study

BACKGROUND

Several studies have assessed the association between siesta and cardiovascular outcomes. Concern exists that confounding might have distorted these results and contributed to discrepancies among them. This report examines the association between siesta habits and cardiovascular risk factors, including sleep disturbances at night, depressed mood, and measures of subclinical atherosclerosis such as coronary calcium score and ankle brachial index.

METHODS

The baseline examination of 4,797 participants aged 45-74 years included interviews, physical examinations, laboratory tests, and electron beam computed tomography. We compared the baseline prevalence of depressed mood, nighttime sleep disturbances, and health status in 3 categories of siesta habits: irregular or no siestas; daily short siestas (1 hour or less); and daily long siestas (>1 hour). We also characterized cardiovascular risk factor distributions in the 3 siesta groups and conducted a sensitivity analysis of the potential for confounding by these factors in studies of incident cardiovascular disease.

RESULTS

Depressed mood and poor self-perceived health status at baseline had positive associations with the age-standardized prevalence of daily long siestas among both men and women. Daily takers of long siestas had a considerably higher prevalence of cardiovascular risk factors in both sexes and appreciably worse measures of subclinical atherosclerosis in men only, in comparison with either of the other siesta groups. Daily long siestas had positive associations with prevalence of several cardiovascular risk factors and measures of subclinical atherosclerosis.

CONCLUSIONS

If uncontrolled, these associations could produce appreciable confounding in studies of siesta habits and incidence of cardiovascular events.

Noninvasive Imaging Techniques to Aid in the Triage of Patients with Suspected Acute Coronary Syndrome: A Review

The evaluation, treatment, and disposition of patients with symptoms suggestive of acute coronary syndrome (ACS) in the Emergency Department continues to be a clinical challenge. Many patients with suggestive symptoms are admitted to the hospital to rule out a myocardial infarction by serial enzyme tests and EKGs and receive an expedited work-up for ischemia. However, the diagnosis can be difficult, given the wide range of potentially atypical symptoms that can signal ACS, which remains a major clinical risk for patients and a liability risk for emergency physicians. This article reviews imaging technologies such as echocardiography and nuclear perfusion imaging used currently in the diagnosis of ACS and rapidly advancing technologies such as CT and MRI that may be able to visualize calcifications, plaques, occlusions, and infarctions noninvasively in real time. Some noninvasive tests used to complete an ischemia work-up after serial enzyme testing and EKGs, such as exercise EKG, stress echocardiography, and stress perfusion imaging, also are reviewed.

Effect of Acquisition Technique on Radiation Dose and Image Quality in Multidetector Row Computed Tomography Coronary Angiography With Submillimeter Collimation

RATIONALE AND OBJECTIVES

We sought to examine effects of tube voltage and current on radiation dose and image quality for minimally invasive coronary angiography with a 16-slice multidetector row computed tomography (MDCT) scanner.

MATERIALS AND METHODS

We scanned the phantom used in the American College of Radiology Computed Tomography Accreditation Program at tube voltages of 80 and 120 kVp at 550, 650, and 750 mAseff, with and without a reduction in radiation dose by electrocardiographically (ECG) controlled tube current modulation (ECG pulsing).

RESULTS

Without ECG pulsing, the effective dose was 3 to 13 mSv. On average, a 50% increase in tube voltage led to increased radiation dose (215%), contrast-to-noise ratio (150%), and decreased image noise (-48%). On average, a 17% increase in mAseff led to increased radiation dose (17%) and contrast-to-noise ratio (4%) and decreased image noise (-9%). Dose reduction by ECG pulsing (simulated heart rate, 70 beats per minute) was 28%. With ECG pulsing, noise in images reconstructed during ventricular systole was double that in images reconstructed during ventricular diastole.

CONCLUSIONS

These quantitative findings about the relationships among scan acquisition parameters, radiation dose, and image quality have practical implications for using ECG pulsing to reduce radiation doses in MDCT coronary angiography.

Population-based assessment of subclinical coronary atherosclerosis using electron-beam computed tomography

AIMS

Coronary artery calcification (CAC) is determined as a measure of the extent of coronary atherosclerosis and can be used for expanded cardiovascular risk stratification. It was our aim to establish reference CAC scores in a population-based unselected European cohort.

METHODS AND RESULTS

The Heinz Nixdorf Recall study (HNR) recruited a total of 4814 participants aged 45-74 years. Cardiovascular risk factors and medications were recorded, and CAC was measured using electron-beam CT (EBCT). CAC score distribution was compared with previous studies in subjects who were self-referred, volunteered, or were physician-referred. Of the 4472 (92.9%) subjects free of clinical coronary artery disease, the CAC score was available in 4275 (95.3%) (2027 men, 2248 women). CAC scores were lower in particular in the higher age groups (> or = 60 years) in men than in the previous studies. Also, in most age groups (except the highest, 70-74 years), subjects with no cardiovascular medications had significantly lower CAC scores than subjects using cardiovascular medications.

CONCLUSIONS

The current report characterises the distribution of EBCT-derived CAC scores in a European unselected population. Compared with previous reports, CAC scores were lower in our cohort, in particular in subjects not receiving cardiovascular medications. Classification of the CAC score may underestimate true risk if previously published referral cohorts are used as the reference.

Imaging of congenital coronary anomalies with multislice computed tomography

OBJECTIVE

To describe a single-center experience of using retrospectively gated multislice computed tomographic (MSCT) coronary angiography for imaging congenital coronary anomalies.

PATIENTS AND METHODS

We retrospectively reviewed the clinical information and imaging studies for 9 patients diagnosed as having congenital coronary anomalies on invasive, selective coronary angiography between February 2001 and October 2003 at the Mayo Clinic in Jacksonville, Fla. Two experienced observers classified by consensus the origin and proximal course of the abnormal coronary arteries as seen on MSCT.

RESULTS

In 1 patient, MSCT showed a normal but extremely anterior origin of the right coronary artery from the right aortic sinus of Valsalva. In the other 8 patients, the origin and course of 4 anomalous right coronary arteries, 2 anomalous left circumflex coronary arteries, and 2 single coronary arteries were recognized easily on MSCT.

CONCLUSION

Similar to electron beam computed tomography and magnetic resonance imaging, widely available MSCT can characterize the proximal course of congenitally abnormal coronary arteries and thus aid in clinical decision making for patients with such anomalies.