Correlation of coronary calcification and angiographically documented stenoses in patients with suspected coronary artery disease: results of 1,764 patients

OBJECTIVES

This study correlated the electron beam computed tomographic (EBCT) calcium scores with the results of coronary angiography in symptomatic patients in order to assess its value to predict or exclude significant coronary artery disease (CAD).

BACKGROUND

Electron beam computed tomography is a sensitive method to detect coronary calcium. However, it is unclear whether it may play a role as a filter before invasive procedures in symptomatic patients.

METHODS

A total of 1,764 patients (1,225 men and 539 women) with suspected CAD from a single center were included in our study. All patients underwent calcium screening with EBCT (C150XP Imatron) and conventional coronary angiography.

RESULTS

Fifty-six percent of men and 47% of women revealed significant coronary stenoses (> or =50%). Total exclusion of coronary calcium (14% of the study group) was associated with an extremely low probability of stenosis (<1%). With calcium scores > or =20th, > or =100th or > or =75th percentile of age groups, the sensitivity to detect stenoses decreased to 97%, 93% and 81%, respectively, in men and to 98%, 82% and 76%, respectively, in women. At the same time, the specificity increased up to 77% in men and women. There was a significant difference in coronary calcium between men and women in all age groups; however, receiver-operating characteristic curves indicated that the test can be performed with equal accuracy in all of these subgroups.

CONCLUSIONS

Calcium screening with EBCT is a highly sensitive and moderately specific test to predict stenotic disease. Exclusion of coronary calcium defines a substantial subgroup of patients, albeit symptomatic, with a very low probability of significant stenoses.

Coronary artery calcium measurement: agreement of multirow detector and electron beam CT

OBJECTIVE

The purpose of our study was to establish the most suitable algorithm to compare coronary artery calcium measurements performed with electron beam CT and multirow detector CT for the assessment of coronary artery disease.

SUBJECTS AND METHODS

Coronary artery screening was performed in 100 patients with both electron beam and multirow detector CT. The images were transferred to a dedicated workstation for determination of the calcium score, volume, mass, density, and number of lesions. In addition to the traditional threshold of 130 H, the score of multirow detector CT studies was reevaluated at a threshold of 90 H. Fifty-nine of the patients underwent conventional coronary catheterization. Receiver operating characteristic curve analysis of the different scoring algorithms for detection of significant coronary artery stenosis was performed.

RESULTS

The correlation between electron beam CT and multirow detector CT was high for every quantification algorithm. Determination of the score and the number of lesions with multirow detector CT revealed a systematic error of the measurement compared with electron beam CT. The areas under the curve in the receiver operating characteristic curve analyses for electron beam and multirow detector CT were similar for the score, volume, and mass, whereas they were lower for the density. No significant difference was found for the areas under the curve between scores using a 130-H and those using a 90-H threshold.

CONCLUSION

Volume and mass indexes are superior to the traditional score, density, and number of lesions for comparing the results of electron beam and multirow detector CT and for determining significant coronary artery disease.

A comparison of electrophysiologically guided antiarrhythmic drug therapy with beta-blocker therapy in patients with symptomatic, sustained ventricular tachyarrhythmias

BACKGROUND

Antiarrhythmic drug therapy guided by invasive electrophysiologic testing is now widely used in patients with symptomatic, sustained ventricular tachyarrhythmias.

METHODS

We conducted a prospective, randomized trial in 170 patients to investigate whether this approach would improve long-term outcome. Patients whose arrhythmia was inducible by programmed electrical stimulation were assigned to treatment with electrophysiologically guided drug therapy based on serial testing (61 patients) or with metoprolol (54 patients). Electrophysiologically guided therapy consisted of serial testing of antiarrhythmic agents to identify the first one that rendered the arrhythmia noninducible. The 55 patients whose arrhythmia was noninducible during the initial electrophysiologic test were also treated with metoprolol.

RESULTS

During a mean (+/- SD) follow-up period of 23 +/- 17 months, recurrent, nonfatal arrhythmia occurred in 44 patients and sudden death due to cardiac factors in 27. The incidence of symptomatic arrhythmia and sudden death combined was virtually the same in the two groups with inducible arrhythmia after two years of observation (electrophysiologically guided therapy vs. metoprolol therapy, 46 percent vs. 48 percent). The outcome was more favorable in the patients with noninducible arrhythmia at base line (75 percent had neither adverse event) than in those with inducible arrhythmia who were assigned to metoprolol therapy (P = 0.009 by log-rank test). Only 6 of the 29 patients (21 percent) with inducible arrhythmia that became noninducible during drug therapy had recurrent arrhythmia or sudden death, as compared with 21 of the 32 patients (66 percent) with arrhythmia that continued to be inducible (P less than 0.001). A multivariate regression analysis identified continued inducibility of the arrhythmia as an independent predictor of recurrent arrhythmia or sudden death (relative risk, 7.3; 95 percent confidence interval, 2.3 to 23.2; P less than 0.001).

CONCLUSIONS

As compared with metoprolol therapy, electrophysiologically guided antiarrhythmic drug therapy did not improve the overall outcome of patients with sustained ventricular tachyarrhythmias. However, effective suppression of inducible arrhythmia by antiarrhythmic drugs was associated with a better outcome than was lack of suppression.

Spectral mapping of the electrocardiogram with Fourier transform for identification of patients with sustained ventricular tachycardia and coronary artery disease

In time domain analysis, detection of late potentials is limited by high pass filtering, noise interference and the necessity to exclude patients with bundle branch block. We therefore used frequency analysis with Fourier transform of multiple segments of the surface electrocardiogram (25 segments, size 80 ms, time shift 3 ms) during sinus rhythm after signal averaging. Thirty-two post-myocardial infarction patients with sustained ventricular tachycardia (VT), 19 post-myocardial infarction patients without VT and 17 healthy subjects were studied. A total of 18 patients had bundle branch block. In 24 out of 32 patients with VT, three-dimensional spectral plots were characterized by spectral peaks greater than 10 dB in the range of 40-200 Hz in segments only at the end of QRS and the early ST wave, but not far outside the QRS. In only 2 out of 19 patients without VT and in 1 out of 17 healthy subjects could such peaks be observed. Noise caused spectral peaks throughout all segments. Sixteen out of 18 patients with bundle branch block were correctly classified with spectral mapping. With the Simson method, patients with bundle branch block had to be excluded, abnormal results were found in 10 out of 19 patients with VT, but also in 5 out of 15 patients without VT and in 3 out of 16 healthy subjects. Thus, spectral mapping of the electrocardiogram offers promise for better identification of patients prone to sustained VT in the presence of coronary artery disease.

Helical and single-slice conventional CT versus electron beam CT for the quantification of coronary artery calcification

OBJECTIVE

We compared electron beam CT with conventional CT to determine the best method for the assessment of the coronary calcium score. We used conventional CT to examine symptomatic and asymptomatic patients suspected of having coronary artery disease.

SUBJECTS AND METHODS

One hundred sixty male patients underwent electron beam CT and helical CT with a pitch of 1 (n = 30) and 2 (n = 30) and using a single-slice mode with (n = 50) and without (n = 50) prospective ECG triggering. In another 50 patients, we determined reproducibility for repeated scanning using electron beam CT. For all images, we derived the calcium score according to the Agatston method. We performed regression analysis and determined mean variability. Mean variability was calculated as the ratio of the absolute difference to the mean of the corresponding calcium scores.

RESULTS

The correlation coefficients for electron beam CT and all conventional CT modes were very high (range, 0.93-0.98). The mean variability was highest in the helical mode with a pitch of 2 (61.4%) and lowest for the single-slice mode with prospective ECG triggering (25.4%). For repeated electron beam CT, the correlation coefficient and mean variability were 0.99 and 22.1%, respectively.

CONCLUSION

ECG-triggered single-slice conventional CT had the best agreement with electron beam CT calcium scores.

Comparison of frequency and time domain analysis of the signal-averaged electrocardiogram in patients with ventricular tachycardia and coronary artery disease: methodologic validation and clinical relevance

Frequency analysis with fast Fourier transform and time domain analysis after signal averaging of the electrocardiogram (ECG) have given contradictory results in patients with sustained ventricular tachycardia after myocardial infarction. Therefore, the same orthogonal ECGs were analyzed in the frequency domain (Blackman-Harris window) and the time domain after signal averaging and high gain, low noise amplification (0 to 300 Hz) in 30 patients with sustained ventricular tachycardia after myocardial infarction, 15 patients without ventricular tachycardia after infarction and 15 healthy subjects. Patients with bundle branch block were not excluded. Twenty-one of the 30 patients with ventricular tachycardia had late potentials in the time domain and abnormal Fourier transform of the ST segment (defined as increased spectral area of 60 to 120 Hz and spectral peaks greater than 10 dB). Among the remaining nine patients with ventricular tachycardia all had no late potentials in the time domain and one manifested abnormal frequency spectra. In contrast, of the 15 patients without ventricular tachycardia after infarction, 2 had late potentials in the time domain and only 1 demonstrated abnormal frequency spectra; none of the healthy subjects manifested either phenomenon. Patients with bundle branch block were correctly classified by Fourier analysis, but were frequently missed by time domain analysis. Normalization of the spectra and area ratio proved potential pitfalls, and the choice of an appropriate ST segment was crucial: if the segment was long with respect to the duration of the late potentials and if it extended too far into the QRS complex, fast Fourier transform yielded random results.(ABSTRACT TRUNCATED AT 250 WORDS)

A dynamic approach to identifying desired physiological phases for cardiac imaging using multislice spiral CT

In this investigation, we describe a quantitative technique to measure coronary motion, which can be correlated with cardiac image quality using multislice computed tomography (MSCT) scanners. MSCT scanners, with subsecond scanning, thin-slice imaging (sub-millimeter) and volume scanning capabilities have paved the way for new clinical applications like noninvasive cardiac imaging. ECG-gated spiral CT using MSCT scanners has made it possible to scan the entire heart in a single breath-hold. The continuous data acquisition makes it possible for multiple phases to be reconstructed from a cardiac cycle. We measure the position and three-dimensional velocities of well-known landmarks along the proximal, mid, and distal regions of the major coronary arteries [left main (LM), left anterior descending (LAD), right coronary artery (RCA), and left circumflex (LCX)] during the cardiac cycle. A dynamic model (called the "delay algorithm") is described which enables us to capture the same physiological phase or "state" of the anatomy during the cardiac cycle as the instantaneous heart rate varies during the spiral scan. The coronary arteries are reconstructed from data obtained during different physiological cardiac phases and we correlate image quality of different parts of the coronary anatomy with phases at which minimum velocities occur. The motion characteristics varied depending on the artery, with the highest motion being observed for RCA. The phases with the lowest mean velocities provided the best visualization. Though more than one phase of relative minimum velocity was observed for each artery, the most consistent image quality was observed during mid-diastole ("diastasis") of the cardiac cycle and was judged to be superior to other reconstructed phases in 92% of the cases. In the process, we also investigated correlation between cardiac arterial states and other measures of motion, such as the left ventricular volume during a cardiac cycle, which earlier has been demonstrated as an example of how anatomic-specific information can be used in a knowledge-based cardiac CT algorithm. Using these estimates in characterizing cardiac motion also provides realistic simulation models for higher heart rates and also in optimizing volume reconstructions for individual segments of the cardiac anatomy.

Detection and quantification of coronary artery calcification with electron-beam and conventional CT

To identify patients with increased risk of having coronary artery disease (CAD), electron-beam computed tomography (EBCT) was used for years for quantifying calcifications of the coronary arteries. The first direct comparison between EBCT and conventional CT was performed to determine the reliability of widely available conventional CT for the assessment of the coronary calcium score. Fifty male patients with suspected CAD were investigated with both modalities, EBCT and conventional 500-ms non-spiral partial scan CT. Scoring of the coronary calcification was performed according to the Agatston method. Forty-two of these patients underwent coronary angiography for the assessment of significant luminal narrowing. The correlation coefficient of the score values of both modalities was highly significant (r = 0.982, p < 0.001). The variability between the two modalities was 42%. Mean calcium score in patients with significant coronary luminal narrowing (n = 37) was 1104 +/- 1089 with EBCT and 1229 +/- 1327 with conventional CT. In patients without luminal narrowing (n = 5) mean calcium score was 73 +/- 57 with EBCT and 26 +/- 35 with conventional CT. Although images of the heart from conventional CT may suffer from cardiac motion artifacts, conventional CT has the potential to identify patients with CAD with accuracy similar to EBCT.

Pulmonary embolism: comprehensive diagnosis by using electron-beam CT for detection of emboli and assessment of pulmonary blood flow

PURPOSE

To comprehensively assess thoracic anatomy and pulmonary microcirculation in pulmonary embolism by using computed tomographic (CT) angiography of the pulmonary arteries combined with functional CT imaging of blood flow.

MATERIALS AND METHODS

Twenty-two patients suspected of having acute pulmonary embolism underwent contrast material-enhanced thin-section electron-beam CT angiography of the pulmonary arteries. In addition, in each patient, a dynamic multisection blood flow CT study was performed on a 7.6-cm lung volume with electrocardiographic gating. Pulmonary blood flow was calculated, and perfusion parameters were visualized on color-coded maps. The color-coded maps and CT angiograms were independently evaluated, segment by segment, by two readers for perfusion deficits and the presence of clots, respectively. The results were compared.

RESULTS

Mean pulmonary blood flow was 0.63 mL/min/mL in the occluded segments versus 2.27 mL/min/mL in the nonoccluded segments (P: =.001). The sensitivity and specificity of perfusion maps for the presence of segmental pulmonary embolism compared with those of CT angiography were 75.4% and 82.3%, respectively, with positive and negative predictive values of 79.6% and 84.7%, respectively. The false-negative findings were caused mainly by partial occlusion of vessels. In eight patients, a substantial alternative or additional pathologic entity was diagnosed.

CONCLUSION

By combining CT angiography and dynamic CT imaging, a comprehensive and noninvasive diagnosis of thoracic structure and function is feasible with a single modality.

Temperature-controlled radiofrequency catheter ablation of AV conduction: first clinical experience

A new technique for catheter ablation of atrioventricular (AV) conduction, using temperature-controlled radiofrequency energy and a bipolar asymmetrical electrode configuration, was applied to 12 patients (mean age, 48 +/- 15 years; range, 18-69 years) with medically refractory atrioventricular nodal reentrant tachycardia (AVNRT) or rapid atrial rhythms. The energy source was a 500 kHz generator with automatic power regulation to a preselected temperature of 80 degrees C. A specially designed 7 F bipolar asymmetric thermo-catheter was used for ablation in all cases. The endpoints of the procedure were: first-degree AV block in patients with AVNRT and third-degree block in patients with atrial fibrillation or flutter. Energy was applied over a range of 1-14 times per patient. After a mean follow-up of 8 +/- 4 months, third- or first-degree AV block persisted in eight patients. In comparison to constant-power radiofrequency ablation, where impedance rises are commonly observed, no impedance rise or coating of the electrode occurred during any of the 97 energy applications in this study. Variable wall contact of the electrode was identified in 20 of 97 applications by a slow temperature rise or a drop in temperature and frequent power adjustments. Thus, monitoring temperature and automatic power regulation may help to reduce the total delivered energy. Temperature control during radiofrequency energy avoids coagulum formation and consequently the associated potential hazards of constant-power application.

Non-invasive intravenous coronary angiography using electron beam tomography and multislice computed tomography

BACKGROUND

Electron beam computed tomography (EBCT) and multislice computed tomography (MSCT) are both suitable for non-invasive identification of coronary stenoses.

OBJECTIVE

To compare intravenous coronary EBCT angiography (EBCTA) and MSCT angiography (MSCTA) with regard to image quality and diagnostic accuracy.

METHODS

EBCTA was done using an Imatron C-150 XP scanner in 101 patients following a standard protocol (slice thickness 3 mm, overlap 1 mm, acquisition time 100 ms, prospective ECG trigger). For MSCTA in a different set of 91 patients (using a Siemens Somatom Plus4VZ scanner), the whole volume of the heart was covered in a spiral technique by four simultaneous detector rows. Using retrospective ECG gating, the raw data were reconstructed in (mean (SD)) 215 (12) axial slices acquired in diastole (slice thickness 1.25 mm, overlap 0.5 mm, acquisition time 250 ms/slice).

RESULTS

With EBCTA, 76% of predetermined coronary segments in a nine segment model could be assessed with diagnostic image quality, and with MSCTA, 82%. A low contrast to noise ratio with EBCTA, and the presence of motion artefacts with MSCTA were the main reasons for inadequate image quality. Using conventional angiography as the gold standard, 77% of stenoses of > 50% could be identified correctly with EBCTA and 82% with MSCTA. Significant stenoses were correctly ruled out in 93% of segments with EBCTA, and in 96% of segments with MSCTA. The average contrast to noise ratio was higher with MSCTA than with EBCTA (9.4 v 6.5; p < 0.001).

CONCLUSIONS

EBCTA and MSCTA show similarly high levels of accuracy for determining and ruling out significant coronary artery stenoses. MSCTA is capable of providing good image quality in more coronary segments than EBCTA because of its better contrast to noise ratio and higher spatial resolution. Motion artefacts seen at heart rates of > 75 beats/min and a higher radiation exposure are the main limitations of MSCTA.

Electrophysiologic and antiarrhythmic efficacy of oral sotalol for sustained ventricular tachyarrhythmias: evaluation by programmed stimulation and ambulatory electrocardiogram

Programmed ventricular stimulation and ambulatory electrocardiography were performed both before and during oral sotalol therapy in 39 patients with ventricular tachyarrhythmia inducible by programmed stimulation (sustained ventricular tachycardia [n = 31], ventricular fibrillation [n = 3], nonsustained ventricular tachycardia [n = 5]). Oral sotalol was started at 80 mg twice daily and the dose thereafter was then gradually increased until a mean daily dose of 300 mg (range 160-480) was reached. In 12 of 34 patients with inducible sustained ventricular tachycardia or fibrillation the arrhythmia was suppressed; in 19 patients it was not and in 3 the spontaneous arrhythmia recurred. Reproducibly inducible nonsustained ventricular tachycardia was suppressed by sotalol in all five patients with this arrhythmia. Thus, a favorable electrophysiologic response was obtained in 17 (44%) of 39 patients. Arrhythmia suppression correlated with the type of arrhythmia (unsustained or sustained) induced during the control period (p less than 0.05), and nonresponders had a higher incidence of previously ineffective drug trials (p less than 0.05). In 22 patients treated long term with sotalol suppression of arrhythmia inducibility on programmed stimulation predicted freedom from recurrences (16 of 17), whereas continued inducibility indicated drug failure (5 of 5) (p less than 0.005). Serial ambulatory electrocardiograms performed in 37 of the 39 patients did not correlate with the results of electrophysiologic testing. For the patients on long-term treatment, invasive testing was superior to electrocardiographic monitoring in predicting outcome. These data indicate that in daily doses of 160 to 480 mg oral sotalol is a very useful agent in patients presenting with sustained ventricular tachycardia or fibrillation, and its efficacy is fairly well predicted by programmed stimulation.

Frequency analysis of the surface electrocardiogram for recognition of acute rejection after orthotopic cardiac transplantation in man

Recognition of acute rejection after heart transplantation has been based mainly on invasive methods until now. In this study we analyzed two well-defined surface electrocardiographic recordings by fast Fourier transform (FFT) (Blackman Harris window, 512 points) after low-noise, high-gain amplification (filter setting 0.5 to 300 Hz) each day for 4 weeks after cardiac transplantation in 27 patients. Twenty acute rejection crises requiring treatment were diagnosed by cytoimmunologic monitoring and endomyocardial biopsy. Single-beat analysis of the QRS complex by FFT revealed a progressive change of the spectral morphology (increase of the frequency content between 70 and 110 Hz) on the days of rejection in 19 of 20 patients. At that time there were no visible changes on the electrocardiogram in the time domain in most patients. At the same time, the frequency content of the ST segment decreased between 10 and 30 Hz in 16 of 20 patients. After successful treatment, the frequency spectra of the QRS complex and ST segment returned to control within 1 to 2 weeks in most patients. One false-positive result was seen in a patient with mediastinitis and large pericardial effusion. A drop in QRS amplitude (greater than 20%) occurred in 10 of 20 rejection crises and in 10 patients without rejection. Nine patients after cardiac transplantation without rejection and seven control patients after cardiac surgery (not transplantation) showed stable frequency plots from one day to the other after the first postoperative day, but with considerable changes in QRS amplitude.(ABSTRACT TRUNCATED AT 250 WORDS)

High Prevalence of Peripheral Arterial Disease and Low Treatment Rates in Elderly Primary Care Patients with Diabetes

Representative data on peripheral arterial disease (PAD) in community-based office practice are scarce while at the same time of high interest. Thus, we aimed to determine the prevalence of peripheral arterial disease (PAD), comorbidity of atherothrombotic manifestations, and treatment intensity among elderly diabetic patients in primary care. In this monitored cross-sectional study, 344 general practitioners throughout Germany determined the ankle-brachial index (ABI) of 6880 consecutive, unselected patients aged 65 years or older with bilateral Doppler ultrasound measurements. PAD was defined according to the recent American Heart Association guidelines (using the higher of the 2 systolic ankle pressures: ABI < 0.9) or peripheral revascularisation, or amputation because of PAD. Coronary events (CAD) and cerebrovascular events (CVD) were taken from the patient's history without additional diagnostic measures. Diabetes was defined according to the clinical diagnosis of the physician and/or HbA1c > or = 6.5 % and/or intake of oral antidiabetic medication and/or application of insulin. 1.743 patients were classified as diabetics: the median disease duration was 6 years (1st; 3rd quartile: 2; 11), median HbA1c 6.6 % (5.9; 7.3), mean age 72.5 +/- 5.4 years, and 51.4 % were females. Diabetics had in comparison with non-diabetics a higher prevalence of PAD defined as ABI < 0.9 (26.3 % vs. 15.3 %, univariate odds ratio 2.0 [95 % confidence interval: 1.7; 2.3]), intermittent claudication (5.1 % vs. 2.1 %, OR: 2.5 [1.9; 3.4]), known CAD (16.1 % vs. 10.6 %, OR: 1.6 [1.4; 1.9]), and known CVD (6.8 % vs. 4.8 %; OR: 1.4 [1.2; 1.8]). 57.4 % of the diabetics with previously known PAD (as only atherothrombotic manifestation) received antiplatelet therapy (vs. 75.1 % with CAD and/or CVD only). The ABI was suitable as screening measure in the primary care setting. In elderly diabetics in comparison to non-diabetics, the prevalence of PAD was very high. Despite the known benefits of antiplatelet therapy, PAD patients were less intensively treated than patients with CAD or CVD.

Pressure-guided nonsurgical myocardial reduction induced by small septal infarctions in hypertrophic obstructive cardiomyopathy

OBJECTIVES

We sought to assess the safety and efficacy of pressure-guided nonsurgical myocardial reduction (NSMR) with the induction of small septal infarctions in patients with hypertrophic obstructive cardiomyopathy (HOCM).

BACKGROUND

Nonsurgical myocardial reduction has been shown to decrease left ventricular outflow tract (LVOT) obstruction and to improve symptoms in patients with HOCM. Infarct sizes differ considerably among studies published so far.

METHODS

In 50 patients, the LVOT gradient was invasively determined at the time of the intervention, four to six months (n = 49) and 12 to 18 months (n = 25) after NSMR. New York Heart Association functional class and quality of life were assessed by using a standard questionnaire. Exercise capacity was tested by spiro-ergometry. Left ventricular (LV) mass was determined by electron beam computed tomography.

RESULTS

Small septal infarctions (mean creatine kinase value 413 +/- 193 U/l) resulted in a sustained decrease in LVOT gradients, from 80 +/- 33 to 18 +/- 17 mm Hg after four to six months (p < 0.001, n = 49) and to 17 +/- 15 mm Hg (p < 0.001, n = 25) after 12 to 18 months. Nonsurgical myocardial reduction was followed by a decrease in LV hypertrophy, which was associated with a sustained increase in exercise capacity, as well as improvement in quality of life.

CONCLUSIONS

Pressure-guided NSMR inducing small septal infarctions was sufficient to result in a sustained decrease in LVOT obstruction and to improve symptoms. The incidence of complications, such as complete heart block with necessary permanent pacemaker implantation (<10%), seems to be diminished by minimizing the infarct size.

Visualization and quantification of coronary calcifications with electron beam and spiral computed tomography

This contribution reviews the pathology and morphology of coronary calcifications. It summarizes the indications for investigation of the coronary arteries. The standard protocols for scan acquisition using electron beam and conventional computed tomography are described as well as various methods for evaluation such as the traditional Agatston scoring method and the newer three-dimensional scoring algorithms. Guidelines for interpreting scores are also reviewed. Major limitations of the reproducibility of the calcium score measurement are summarized. Future aspects of multirow-detector spiral computed tomography with retrospective electrocardiographic triggering for quantifying coronary calcium are discussed.

Segmental and subsegmental pulmonary arteries: evaluation with electron-beam versus spiral CT

PURPOSE

To compare contrast agent-enhanced spiral and electron-beam computed tomography (CT) for the analysis of segmental and subsegmental pulmonary arteries.

MATERIALS AND METHODS

CT angiography of the pulmonary arteries was performed in 56 patients to rule out pulmonary embolism. Electron-beam CT was performed in 28 patients. The other 28 patients underwent spiral CT with comparable scanning protocols. The depiction of segmental and subsegmental arteries was analyzed by three independent readers. The contrast enhancement in the main pulmonary artery was measured in each patient.

RESULTS

Analysis was performed in 1,120 segmental and 2, 240 subsegmental arteries. One segmental (RA7, P =.010) and two subsegmental (LA7b, P =.029; RA6a+b, P =.038) arteries in paracardiac and basal segments of the lung were depicted significantly better with electron-beam CT. There was no statistically significant difference between electron-beam and spiral CT in the total number of analyzable peripheral arteries depicted. The mean contrast enhancement in the main pulmonary artery was 362 HU in electron-beam CT studies versus 248 HU in spiral CT studies.

CONCLUSION

Detailed visualization of peripheral pulmonary arteries is well within the scope of advanced CT techniques. Electron-beam CT has minor advantages in analyzing paracardiac arteries, probably because of reduction of motion artifacts and higher contrast enhancement. Further studies are needed to establish whether electron-beam CT allows a more confident diagnosis of emboli in these vessels.

Usefulness of calcium scoring using electron beam computed tomography and noninvasive coronary angiography in patients with suspected coronary artery disease

The aim of this study was to investigate the reliability of calcium scoring (CS) and electron beam computed tomographic angiography (EBCTA) as a noninvasive tool in the diagnosis of coronary artery disease (CAD): 93 consecutive patients (aged 59 +/- 9 years) with symptoms suspicious for CAD underwent CS. In 87 of these subjects, an additional EBCTA investigation was performed. Using receiver-operating characteristic curve analysis, we determined a calcium score cut point providing an overall sensitivity of 80% and a specificity of 72% in detecting patients with CAD. For clinical purposes the use of cut points is difficult. We therefore determined score ranges providing >80% specificity (high score range) and >85% sensitivity (low score range) and determined the scores between these ranges as equivocal borderline scores. Calculated on a per-segment basis in assessable proximal and midcoronary segments, the sensitivity for detecting coronary stenoses >50% was 78%, and the specificity was 93%. Thus, 32 of 44 patients with significant CAD and 24 of 49 patients without CAD were correctly classified. The combination of CS and EBCTA predicted CAD in 77% (72 of 93) of patients. No or low calcium scores provided high specificity for ruling out CAD. The addition of EBCTA in those patients improved sensitivity. In patients with high calcium scores, accuracy of EBCTA was not significantly different from CS alone (72% vs 83%), whereas in patients with borderline scores it was significantly superior (80% vs 58%, p <0.03). Thus, the complementary use of CS and EBCTA appears beneficial, particularly in patients with borderline scores, and could improve sensitivity in the low score range. In the presence of high scores, no major diagnostic gain from an additional EBCTA versus CS alone could be observed.

The Use of Telemedicine in Combination With a New Stroke-Code-Box Significantly Increases t-PA Use in Rural Communities

BACKGROUND

The benefit of tissue plasminogen activator (t-PA) is strongly associated with the time to treatment. In Bavaria, Germany, only half of the population has the opportunity to be transferred to 1 of the 19 stroke units within the critical time window of less than 3 hours. The aim of this study was to investigate the benefit of a new stroke-code-box for t-PA thrombolysis combined with a telemedicine network system to increase the use of acute stroke thrombolysis.

METHODS

Two specialized stroke centers in Germany established a 24-hour telemedicine network (Telemedicine Pilot Project of an Integrated Stroke Care [TEMPiS]) to advise 12 community hospitals in eastern Bavaria. These clinics are linked via telemedicine in a 24-hour/7-day service network that allows patients to be examined by experts via a videoconference system Additionally, a special stroke-code-box for acute t-PA thrombolysis was designed to reduce time in the application and documentation process.

RESULTS

In the 12-month period before implementation of the TEMPiS network system, 10 patients had received systemic thrombolysis. In our 6-month study period (from July to December 2003) and after implementation of a stroke-code-box for t-PA thrombolysis within the telestroke network, 164 patients with acute stroke were presented with t-PA treatment indications. Of this patient population, 27.4% (45 of 164) received t-PA.

CONCLUSIONS

Stroke care, including t-PA thrombolysis in non-urban areas, is feasible using a modern stroke unit concept within a telestroke network. With the expertise of specialized stroke centers accessed via telemedicine and the design of a stroke-code-box for t-PA thrombolysis, nearly one-third of patients presented with a possible indication for systemic thrombolysis can be treated with t-PA, thereby increasing the options for a successful stroke treatment.

Frequency analysis of the electrocardiogram with maximum entropy method for identification of patients with sustained ventricular tachycardia

Late potentials in the terminal phase of the QRS-complex during sinus rhythm have been proposed to identify a subgroup of patients with myocardial infarction at risk of ventricular tachycardia (VT). Frequency analysis of the ECG with Fourier transform (FFT) has been applied for detection of these microvolt level signals, but is limited by poor frequency resolution of short data segments and spectral leakage. We therefore developed frequency analysis using the maximum entropy method (MEM) based on an autoregressive (AR) model. Orthogonal electrocardiograms were recorded from the body surface of patients with and without VT, and healthy persons after low noise, high-gain amplification. Multiple 40 ms segments (time intervals 2 ms, AR-parameters tapered) were analyzed (spectrotemporal mapping): low-frequency components were eliminated by building difference spectra with optimal high order and fixed low order. The MEM-spectra revealed high frequency components (40-200 Hz) in the terminal phase of the QRS-complex and in the ST-section in 26/38 patients with VT, but only in 2/20 without VT and in 1/20 healthy persons (p less than 0.05). Unlike FFT, MEM allowed localization of late potentials by the analysis of short data segments. Thus, MEM offers promise for noninvasive identification of patients with sustained VT after myocardial infarction and detailed analysis of late potentials.

Diagnosis and results of different treatment regimens in patients with spinal abscesses

Bacterial abscesses involving the spinal canal are associated with a high morbidity and mortality. Most frequently, these lesions are found in the epidural, rarely in the subdural space. In this report, our clinical material consists of a series of 16 patients treated during the last seven years. The clinical presentation included local neurological signs (back pain, para-/tetraparesis, bladder dysfunction), disturbances of consciousness (ranging from drowsiness to deep coma) and general inflammatory signs (meningism, fever). All patients presented with risk factors (septic foci, chronic diseases, and iatrogenic causes). Laboratory investigations revealed typically pathological blood sedimentation rate, leucocytosis and CSF-pleocytosis. Radiologically, the diagnosis was confirmed by myelography, CT and preferably MRI. The abscesses were located epidurally in 14 and subdurally in 2 cases. The surgical treatment included laminectomy, or multiple flavectomies in extensive lesions. Drainage systems (either simple silicon outflow drains or suction-/irrigation systems) were installed in all cases, as well as antibiotic treatment. Results of treatment: Following an observation period of 0.5-6 years, we found complete recovery in six (38%) cases, six (38%) others were mildly disabled and four (25%) patients died. Focussing on the results of the two different drainage systems, we found a statistically significant superiority of the inflow-/outflow system. Complications included mandatory re-exploration, post-inflammatory hydrocephalus, syringomyelia, spinal instability, surgical treatment of peripheral septic foci and therapy resistant septicaemia. In conclusion, we propose that spinal epi- or subdural abscesses require surgical evacuation, using a suction-/irrigation drainage system, as well as antibiotic and intensive care treatment.

Are elevated homocysteine plasma levels related to peripheral arterial disease? Results from a cross-sectional study of 6880 primary care patients

BACKGROUND

It is still unclear whether the strength of the association between elevated plasma homocysteine (HC) levels and peripheral arterial disease (PAD), coronary artery disease (CAD) and cerebrovascular disease (CVD) is similar.

METHODS

Fasting homocysteine plasma levels were measured in 6880 unselected primary care patients aged 65 years or older. Presence of PAD was determined with the ankle brachial index, and both CAD and CVD were recorded according to patient history.

RESULTS

Median homocysteine levels in the total sample (58.0% females, mean age 72.5 years, mean body mass index 27.3 kg m-2) differed between patients with and without PAD: 15.2 micro mol L-1 (95% confidence interval [CI] 14.8; 15.7, vs. 13.9 micro mol L-1 (CI: 13.8; 14.1; P < 0.001). Peripheral arterial disease prevalence moderately increased from 13.0% in the lowest HC quintile to 24.3% in the highest quintile (crude odds ratio [OR], 2.1 [CI: 1.7; 2.6]). The frequency of atherothrombotic manifestations in the patients' history increased nearly linearly across the homocysteine quintiles in the univariate analysis. However, the association diminished substantially after adjusting for known interfering variables: the ORs between the HC highest fifth vs. lowest fifth (adjusted for age, gender, smoking status, diabetes, hypertension lipid disorders, and estimated glomerular filtration rate levels) for PAD decreased to 1.4, for CAD to 1.0 (NS), and for CVD to 1.1. (NS).

CONCLUSIONS

Elevated HC is only slightly more related to PAD than to CAD and CVD. After adjustment for known risk factors, the effect size is small, and an association can no longer be observed between homocysteine and CAD and CVD.

Top-resolution frequency analysis of electrocardiogram with adaptive frequency determination. Identification of late potentials in patients with coronary artery disease

Frequency analysis of the electrocardiogram with Fourier transform is a sensitive method of detecting late potentials. However, information about localization of late potentials is lost, frequency resolution is poor, and window functions have to be applied. We therefore analyzed multiple segments (25 msec long) of the surface electrocardiogram ("spectrotemporal mapping") with adaptive frequency determination (AFD), an autoregressive algorithm that is characterized by high-frequency resolution in very short segments without the use of window functions. Results were compared with those from Fourier transform and the Simson method. We studied 38 patients after myocardial infarction (MI) with sustained ventricular tachycardia (VT), 21 patients after MI without VT, and 18 healthy subjects. Frequency peaks could be clearly differentiated until a minimal interval of 6 Hz; with fast Fourier transform (Blackman Harris window) in a much longer segment (80 msec), the spectral peaks merged into one another at an interval of about 30 Hz. AFD revealed high-frequency components as narrow peaks in the range of 40-160 Hz in 28 of 38 patients (74%) after MI with VT. Because of the short segment size, exact localization of late potentials was possible; in most of the patients, the peaks occurred in segments inside the QRS complex and ended 20 +/- 10 msec after termination of the QRS complex. In patients after MI without VT, only four of 21 patients (19%) had spectral peaks in segments after the end of the QRS complex; however, 13 of 21 patients demonstrated microvolt potentials in segments within the QRS complex. These potentials did not extend beyond the end of normal ventricular activation. Only two of 18 healthy subjects showed abnormal AFD results. Patients with bundle branch block did not need to be excluded. AFD allowed good differentiation between late potentials and noise by a characteristic pattern of the spectral peaks. For the Simson method, patients with bundle branch block had to be excluded, and overall sensitivity was 42%. In five cases, the cause of failure of the Simson method could be identified as incorrect determination of the QRS limits due to noise. Thus, AFD is a promising method for detailed analysis of late potentials; it combines the advantages of frequency analysis (good differentiation between signal and noise and high-pass filters not necessary) and time domain analysis (localization of late potentials).