Electrophysiology lab efficiency comparison between cryoballoon and point-by-point radiofrequency ablation: a German sub-analysis of the FREEZE Cohort study

BACKGROUND

Pulmonary vein isolation (PVI) is recommended to treat paroxysmal and persistent atrial fibrillation (AF). This analysis aimed to assess the hospital efficiency of single-shot cryoballoon ablation (CBA) and point-by-point radiofrequency ablation (RFA).

METHODS

The discrete event simulation used PVI procedure times from the FREEZE Cohort study to establish the electrophysiology (EP) lab occupancy time. 1000 EP lab days were simulated according to an illustrative German hospital, including 3 PVI cases per day using CBA at one site and RFA at the other.

RESULTS

The analysis included 1560 CBA patients and 1344 RFA patients from the FREEZE Cohort. Some baseline patients' characteristics were different between groups (age, AF type, and some concomitant diseases), without being statistically associated to ablation procedure time. Mean procedure time was 122.2 ± 39.4 min for CBA and 160.3 ± 53.5 min for RFA (p < 0.0001). RFA was associated with a more than five-fold increase of cumulative overtime compared to CBA over the simulated period (1285 h with RFA and 253 h with CBA). 70.7% of RFA lab days included overtime versus 25.7% for CBA. CBA was associated with more days with an additional hour at the end of the EP lab shift compared to RFA (47.8% vs 11.5% days with one hour left, respectively).

CONCLUSION

CBA is faster and more predictable than point-by-point RFA, and enables improvements in EP lab efficiency, including: fewer cumulative overtime hours, more days where overtime is avoided and more days with remaining time for the staff or for any EP lab usage. Clinical trial registration NCT01360008 (first registration 25/05/2011).

Influence of sex on results and consequences of coronary fractional flow reserve in clinical practice: results of a prospective large-scale multicenter registry

Background

Measurement of fractional flow reserve (FFR) is clinically indicated in order to assess the hemodynamic relevance of coronary artery lesions and determine the need for revascularization. Preliminary data sugest that there may be significant differences regarding use and outcome of FFR measurements in men versus women.

Purpose

We therefore analyzed the influence of sex on FFR values and treatment consequences in a large-scale, prospective multicenter registry of consecutive patients undergoing clinically indicated FFR measurements in the setting of chronic or acute coronary syndromes.

Methods

In a large, multicenter prospective registry of patients undergoing FFR, the relationship of stenosis degree to FFR, the influence of FFR on revascularization decisions were compared between male and female patients. (clinicaltrials.gov NCT03055910)

Results

A cohort of 2000 patients from 8 centers was evaluated (73% male, 27% female, median age 69±10 years, 15% acute coronary syndromes). The median number of interrogated lesions was 2 in male and 2 in female patients. A total of 2958 lesions were interrogated by FFR (2156 male, 802 female; 67 LM, 1722 LAD, 646 LCX, 523 RCA). Median stenosis degree was 60% (IQR 50%-70%) in male and, identically, 60% (IQR 50%-70%) in female patients. All the same, median measured FFR values were 0.86 (IQR 0.81–0.92) in male and 0.89 (IQR 0.84–0.93) in female patients (p&lt;0.001). Of all lesions interrrogated, 488/2156 (23%) in men and only 100/802 (12%) in women displayed an FFR value ≤0.80 (p&lt;0.001). The median stenosis degree of lesions with an FFR value ≤0.80 was 70% (IQR 60–80%) in men and 70% (IQR 65–84%) in women (n.s.). In multivariable analysis, stenosis degree, lesion location in LAD, ACS culprit lesion, and male sex were independent predictors of an FFR value ≤0.80. The overall rate of revascularization was 24% in men and 14% in women (p&lt;0.001), driven by lower FFR values in men. In lesions with FFR values ≤0.80, revascularization rate was 94% both in men and in women (n.s.).

Conclusion

Female sex is independently associated with higher FFR values when used to determine the hemodynamic relevance of coronary lesions in the setting of chronic or acute coronary syndromes. Independent of stenosis degree, FFR measurements are significantly less frequently followed by revascularization in women.

Funding Acknowledgement

Type of funding sources: Private company. Main funding source(s): St. Jude Medical

6114Indications, procedural parameters, complications and consequences of fractional flow reserve measurements in a multicenter cohort

Background

Determination of the Fractional Flow Reserve (FFR) has become part of routine clinical practice. Contemporary clinical use, consequences as well as complications in consecutive, large cohorts have not been thoroughly investigated. We report the results of the prospective Fractional Flow Reserve Fax Registry F (FR2) conducted in Germany.

Purpose

To systematically analyze indications, procedural parameters, complications and consequences of intracoronary pressure measurements in a large contemporary cohort.

Methods

Data of 2000 consecutive patients undergoing clinically indicated FFR, iFR or pd/pa measurements in 8 interventional centres in Germany were prospectively collected in a systematic fashion. Data included basic patient characteristics, procedural aspects of intracoronary pressure measurements, associated complications, visual stenosis degree, measurement results and treatment decisions.

Results

Mean patient age was 68±11 years, 73% of patients were male. Of all patients, 300 patients (15%) had an acute coronary syndrome (STEMI: 9; NSTEMI: 94; unstable angina: 197) and 1002 patients (50%) had undergone previous revascularization. A mean of 1.7±0.9 measurements were performed per patient, for which an average of 1.02 pressure wires were required (more than 1 wire in 64 patients). For all 3373 interrogated lesions, median stenosis degree was 60%. Vasodilator-free measurements were performed in 415/3373 cases (12%, iFR: 346; pd/pa: 69). For vasodilation, i.v. adenosine was used in 396 cases (13%), i.c. adenosine in 2628 cases (87%), and other drugs in 10 cases (0.3%). Measurement was performed before potential revascularization in 3232 cases (96%) and during or following PCI in 141 cases. In 2958 lesions analyzed by FFR, mean FFR was 0.87, with 588 FFR measurements ≤0.80 (19.8%). Median FFR values were higher for i.c than i.v. adenosine administration (0.88 vs. 0.84), but not significantly different after adjustment for stenosis degree. In 735 cases (20.2%), intracoronary pressure measurement was followed by revascularization measures, while in 2637 cases (79.8%), no revascularization or no further revascularization was performed. In 36 out of 117 stenoses visually estimated to be ≥90%, revascularization was deferred following pressure measurement (31%). In 75 out of 2958 lesions analyzed by FFR, revascularization was performed even though FFR was >0.80 (3%). Severe complications (vessel dissection or occlusion) occurred in 5 out of 2000 patients as a consequence of intracoronary pressure measurement, resulting in death of 1 patient.

Conclusion

In clinical practice, the majority of intracoronary pressure measurements are performed in stenoses of intermediate angiographic severity and revascularization is deferred in approximately 80% of lesions. Vasodilator-free measurements are infrequent and route of adenosine administration has no effect on results. Complication rate is low but not negligible.

Acknowledgement/Funding

Abbott Vascular

Noninvasive coronary angiography by contrast-enhanced electron beam computed tomography

Electron beam computed tomography (EBCT) is a cross-sectional imaging method with high temporal and spatial resolution. So far, it has mainly been applied for the detection of coronary artery calcifications which permit the very sensitive detection of coronary atherosclerosis even in the very early stages. However, after intravenous injection of a contrast agent, EBCT also permits the direct visualization of the coronary artery lumen. For these investigations, a volume data set is acquired that consists of 40 axial cross-sections of the heart (3 mm slice thickness). To evaluate the coronary arteries as to the presence of stenoses and occlusions, various forms of post-processing, including shaded surface display, maximum intensity projection, and multiplanar reconstruction, are applied. The sensitivities and specificities for the detection of coronary artery stenoses and occlusions are about 90%. Best results are obtained for coronary artery bypass grafts, the left main coronary artery, and the left anterior descending coronary artery, while reduced image quality impairs the results for the right coronary artery and the left circumflex coronary artery.

[Detection of coronary calcifications by electron beam tomography and multislice spiral CT: clinical relevance]

Coronary calcifications can be detected and quantified using electron beam tomography (EBT) or newer generation multi-slice spiral CT (MSCT) scanners. An abundance of data has been acquired by EBT. It could be shown that the amount of coronary calcium correlates to the coronary plaque burden. The detection of coronary calcium with CT imaging methods therefore provides a unique opportunity to detect and quantify coronary atherosclerosis in a subclinical stage. Consequently, the presence and amount of coronary calcium has been shown to be indicative for an increased coronary event risk in symptomatic and asymptomatic individuals. Several clinical studies found a predictive value that was superior to conventional risk factors. Clinically, the use of coronary calcification assessment may therefore be beneficial in patients who, based on traditional risk factors, seem to be at "intermediate risk" for coronary events (10-year event risk 10-20%) in order to decide on the aggressiveness of risk factor modification. The role of coronary calcium quantification to monitor the progression of disease has not been clarified yet. Large, ongoing trials will provide further data as to the relative merit of coronary calcium assessment for risk stratification and will help to more clearly define its clinical role. The relationship between coronary calcium and coronary stenoses is more complex. While the absence of coronary calcifications makes significant coronary stenoses unlikely, even large amounts of coronary calcium do not necessarily indicate the presence of coronary artery stenoses. Pronounced coronary calcifications as an isolated finding should therefore not be the motivation for invasive diagnostic procedures in the absence of other evidence of ischemic heart disease.

Coronary calcifications in young patients with first, unheralded myocardial infarction: a risk factor matched analysis by electron beam tomography

OBJECTIVE

To compare the presence and extent of coronary calcifications in young patients with first, unheralded acute myocardial infarction with matched controls without a history of coronary artery disease.

METHODS

In 102 patients under 60 years of age (19-59 years, mean 41 years; 88% male), electron beam tomography was done 1-14 days after acute myocardial infarction, before any coronary intervention. Coronary calcifications were quantified using the Agatston score. Age related calcium centiles were determined based on the Mayo Clinic "epidemiology of coronary calcification" study, and results were compared with a group of 102 controls without coronary artery disease, matched for sex, age, and risk factors.

RESULTS

Calcifications were present in 95.1% of patients with acute myocardial infarction and in 59.1% of controls (p = 0.008). The mean (SD) Agatston score was 529 (901) in the infarct patients versus 119 (213) in the controls (p < 0.001). An Agatston score above the 50th centile was present in 87.2% of infarct patients and 47.0% of controls (p = 0.006), and above the 90th centile in 60.7% of infarct patients and only 5.8% of controls (p = 0.001).

CONCLUSIONS

In young patients with their first, unheralded acute myocardial infarction, the presence and extent of coronary calcium are significantly greater than in matched controls.

Multicentre study of fetal cardiac time intervals using magnetocardiography

OBJECTIVE

A database with reference values of the durations of the various waveforms in a magnetocardiogram of fetuses in uncomplicated pregnancies is assessed. This database will be of help to discriminate between pathologic and healthy fetuses. A fetal magnetocardiogram is a recording of the magnetic field in a location near the maternal abdomen and reflects the electric activity within the fetal heart. It is a non-invasive method, which can be used with nearly 100% reliability from the 20th week of gestation onward.

DESIGN

Durations of the waveforms were assembled from averaged magnetocardiograms and statistically processed.

SETTING

Fetal magnetocardiograms were measured with different magnetocardiographs. All measurements were carried out in magnetically shielded rooms.

SAMPLE

Fetal magnetocardiograms were obtained for 582 healthy patients.

METHOD

The durations of the waveforms were extracted from fetal magnetocardiograms measured at the cooperating centres. The variables collected included the duration of the P-wave, the PR interval, the PQ interval, the QRS complex, the QT interval and the T-wave and QTc value. The results were compared with values extracted from electrocardiograms of fetuses measured via electrodes attached to the maternal abdomen, from electrocardiograms measured during labour using a scalp electrode, and from electrocardiograms recorded in newborns, that were found in the literature.

MAIN OUTCOME MEASURES

Values of the durations are given as a function of gestational age including the regression line as well as the bounds marking the 90%, 95% and 98% prediction interval.

RESULTS

The durations of the P-wave, the PR interval, the QRS complex, the QT interval and QTc value increase linearly with gestational age. The durations of the PQ interval and the T-wave are independent of fetal age.

CONCLUSION

The values found agree with those found in the literature. The scatter of the data is wide due to the variation in normal physiology, the measuring system and signal processing and the subjectivity of the researcher. However, the system can define normal ranges and may be used in diagnosis.

Progression of aortic valve calcification: association with coronary atherosclerosis and cardiovascular risk factors

BACKGROUND

Recent studies demonstrated an influence of atherosclerotic risk factors on the progression of aortic valve stenosis. The extent of aortic valve calcification (AVC) was also found to be a strong predictor of stenosis progression. We investigated the influence of the LDL cholesterol level (LDL), other standard cardiovascular risk factors, and the extent of coronary calcification (CC) on the progression of AVC quantified by electron beam tomography (EBT).

METHODS AND RESULTS

In 104 patients (64.7+/-8 years, 89 male) with an EBT scan positive for AVC, CC and AVC were quantified using a volumetric score. EBT was repeated at a mean interval of 15 months (10 to 36 months), and the progression of AVC and CC was determined. Patients were divided into 2 groups according to LDL: group 1, LDL</=3.36 mmol/L (130 mg/dL), 57 patients; group 2, LDL>3.36 mmol/L (130 mg/dL), 47 patients. Mean values for CC were 546+/-932 mm(3) in scan 1 and 665+/-1085 mm(3) in scan 2 for AVC 324+/-796 mm(3) and 404+/-1076 mm(3), respectively. The mean progression of CC was 27+/-37% (group 1, 16+/-22%; group 2, 39+/-46%, P</=0.001) and of AVC was 25+/-38% (group 1, 9+/-22%; group 2, 43+/-44%, P</=0.001).

CONCLUSIONS

Quantification of AVC by EBT permits new insights into the progression of aortic valve sclerosis. We observed a strong influence of LDL cholesterol level on the progression of AVC and CC, suggesting that lipid-lowering therapy may decrease the progression of aortic valve calcification.

Noninvasive coronary angiography by magnetic resonance imaging, electron-beam computed tomography, and multislice computed tomography

In recent years, several techniques for noninvasive imaging of the coronary artery lumen (noninvasive coronary angiography) have been developed. These techniques include magnetic resonance imaging, electron-beam computed tomography, and, most recently, multislice computed tomography. Each of these techniques has specific advantages and disadvantages. Currently, EBCT seems to permit the most robust coronary artery imaging. In the future, imaging modalities will have to be further improved and validated in order to define specific areas for potential clinical applications.

Overlapping cross-sections significantly improve the reproducibility of coronary calcium measurements by electron beam tomography: a phantom study

PURPOSE

We conducted phantom studies to investigate whether overlapping cross-sections and volumetric scoring would significantly improve interscan reproducibility of electron beam tomography (EBT) for coronary artery calcium quantification.

METHOD

Fifteen phantoms simulating various amounts of coronary calcification were scanned in five different positions with a slice thickness of 3.0 mm and a table feed of 3.0, 2.5, and 2.0 mm. For the conventional "Agatston score" and a "volume score" (total volume of calcified lesions), interscan variabilities were compared between the three image acquisition protocols.

RESULTS

Agatston score variability was significantly lower for the 2.0 mm table feed than for the 3.0 or 2.5 mm table feed (3.0 mm: 22.9 +/- 10.3%; 2.5 mm: 13.6 +/- 8.2%; 2.0 mm: 8.9 +/- 5.5%). Volume score variability was significantly lower for 2.5 and 2.0 mm table feed than for 3.0 mm table feed (3.0 mm: 21.7 +/- 11.0%; 2.5 mm: 10.9 +/- 5.9%; 2.0 mm: 9.8 +/- 5.9%).

CONCLUSION

Overlapping cross-sections, especially in combination with volumetric scoring, significantly improved interscan reproducibility of EBT calcium quantification in a phantom study.

Recommendations for standardization of EBT and MSCT scanning

BACKGROUND

The detection and quantification of coronary calcifications by electron beam tomography (EBT) permits to diagnose coronary atherosclerosis in an early stage. Initial reports indicate that multislice spiral CT (MSCT) also permits the quantification of coronary calcium, while equivalency to EBT has not been definitely proven. Since image acquisition, reconstruction and evaluation parameters influence the results of calcium quantification with CT techniques, standardization of the investigation is mandatory to make results comparable.

AIM

The article summarizes guidelines for image acquisition and evaluation by EBT and describes guidelines and consensus reports that were issued concerning the clinical use of the method.

Detection of coronary artery stenoses by contrast-enhanced, retrospectively electrocardiographically-gated, multislice spiral computed tomography

BACKGROUND

Multislice spiral computed tomography (MSCT) with retrospectively ECG-gated image reconstruction permits coronary artery visualization. We investigated the method's ability to identify high-grade coronary artery stenoses and occlusions.

METHODS AND RESULTS

A total of 64 consecutive patients were studied by MSCT (4x1 mm cross-sections, 500-ms rotation, table feed 1.5 mm/rotation, intravenous contrast agent, retrospectively ECG-gated image reconstruction). All coronary arteries and side branches with a luminal diameter >/=2.0 mm were assessed concerning evaluability and the presence of high-grade stenoses (>70% diameter stenosis) or occlusions. Results were compared with quantitative coronary angiography. Of 256 coronary arteries (left main, left anterior descending, left circumflex and right coronary artery, including their respective side branches), 174 could be evaluated (68%). In 19 patients (30%), all arteries were evaluable. Artifacts caused by coronary motion were the most frequent reason for unevaluable arteries. Overall, 32 of 58 high-grade stenoses and occlusions were detected by MSCT (58%). In evaluable arteries, 32 of 35 lesions were detected, and the absence of stenosis was correctly identified in 117 of 139 arteries (sensitivity, 91%; specificity, 84%). If analysis was extended to all stenoses with >50% diameter reduction, sensitivity was 85% (40 of 47) and specificity was 76% (96 of 127).

CONCLUSIONS

MSCT with retrospective ECG gating permits the detection of coronary artery stenoses with high accuracy if image quality is sufficient, but its clinical use may presently be limited due to degraded image quality in a substantial number of cases, mainly due to rapid coronary motion.

Variability of repeated coronary artery calcium measurements by electron beam tomography

In 120 patients, the mean interscan variability of coronary calcium quantification by electron beam tomography was 19.9% (median 7.8%) for the traditional calcium score, and 16.2% (median 5.7%) for volumetric scoring. Although this difference was not significant, there was a significant influence of the total amount of calcium, number of acquired images, and image noise on interscan reproducibility.

Visualization of coronary artery anomalies and their anatomic course by contrast-enhanced electron beam tomography and three-dimensional reconstruction

Anomalous coronary arteries are rare conditions. However, they may cause myocardial ischemia and sudden death and their reliable identification is crucial for any imaging method that attempts coronary artery visualization. We studied the ability of contrast-enhanced electron beam tomography (EBT) to identify anomalous coronary arteries and their course. Thirty patients with previously identified coronary anomalies and 30 subjects with normal coronary anatomy were studied. By EBT, 40 to 50 axial images of the heart (3-mm slice thickness, 1 mm overlap, electrocardiographic trigger) were acquired in a single breathhold during continuous injection of contrast agent (160 ml, 4 ml/s). Based on the original images and 3-dimensional reconstructions, the EBT data were analyzed by 2 blinded observers as to the presence of coronary anomalies and their course. Results were compared with invasive angiography. EBT correctly identified all normal controls and all patients with coronary anomalies. The anatomic course of the coronary anomalies was correctly classified in 29 of 30 patients (97%), including right-sided origin of the left main coronary artery (n = 4) or of the left circumflex coronary artery (n = 15), left-sided origin of the right coronary artery (n = 9), and 1 coronary fistula from the left circumflex coronary artery to the right atrium. Only the distal anastomosis of a second fistula from the left circumflex coronary artery to a bronchial artery was not correctly identified. This study demonstrates that contrast-enhanced EBT is a reliable noninvasive technique to identify anomalous coronary arteries and their course.

Noninvasive coronary angiography by retrospectively ECG-gated multislice spiral CT

BACKGROUND

We investigated the applicability and image quality of contrast-enhanced coronary artery visualization by multislice spiral CT using retrospective ECG gating.

METHODS AND RESULTS

Twenty-five patients in sinus rhythm (significant coronary artery stenoses ruled out by invasive angiography) were studied with a multislice spiral CT (Siemens SOMATOM Volume Zoom). In inspiration (mean breath-hold, 37 seconds), a volume data set of the heart was acquired (intravenous contrast agent; 4 x 1-mm slice thickness; 500-ms rotation; table feed, 1.5 mm/360 degrees ). Simultaneous recording of the ECG permitted retrospective reconstruction of contiguous cross sections in intervals of 1 mm at any desired interval of the cardiac cycle. The mean duration of the image reconstruction window was 185 ms. Next to 3-dimensional reconstructions of the heart and coronary arteries, multiplanar reconstructions were rendered to determine the visualized length of the coronary arteries, the contrast-to-noise ratio, and the correlation of coronary artery diameters to quantitative coronary angiography.

CONCLUSIONS

The coronary arteries could be visualized over long segments (left main, 9+/-4 mm; left anterior descending, 112+/-34 mm; left circumflex, 80+/-29 mm; right coronary artery, 116+/-33 mm). On average, 78+/-16% of these distances were visualized free of motion artifacts. The mean contrast-to-noise ratio was 9.3+/-3.3. Coronary artery diameters in multislice spiral CT showed close correlation to quantitative coronary angiography (CT, 3.3+/-1.0 mm; angiography, 3. 2+/-0.9 mm; mean difference, 0.38 mm; r=0.86). Contrast-enhanced multislice spiral CT permits visualization of the coronary artery lumen. Further studies are necessary to determine whether image quality is sufficient to reliably detect coronary artery stenoses.

Contrast enhanced electron beam computed tomography to analyse the coronary arteries in patients after acute myocardial infarction

OBJECTIVE

To evaluate the accuracy of contrast enhanced electron beam computed tomography (EBCT) after acute myocardial infarction in determining patency of the infarct related artery and detecting high grade stenoses and occlusions in the coronary vessels.

DESIGN

Case study using blinded comparison with invasive coronary angiography.

PATIENTS

36 patients (mean age 53 years) 4-70 days after acute myocardial infarction.

INTERVENTIONS

The patients were studied by EBCT and invasive coronary angiography. For EBCT, 50 axial images of the heart (3 mm slice thickness) were acquired. They were triggered by the ECG during breath holding, after intravenous injection of contrast agent. The original images, surface reconstructions, and maximum intensity projections were evaluated for the presence of high grade stenoses and occlusions of the coronary arteries.

MAIN OUTCOME MEASURES

EBCT results were compared with invasive coronary angiography.

RESULTS

Of a total of 144 coronary arteries (left main, left anterior descending, left circumflex, and right coronary artery in 36 patients), 29 (20%) were unevaluable by EBCT. In the remaining arteries, 33 of 36 high grade lesions were correctly detected (92% sensitivity). Specificity was also 92% (73/79). Patency of the infarct related artery was correctly detected in 15 of 16 cases (94%). Five of the 14 occluded infarct related arteries (35%) were mistaken as stenotic but patent, and six could not be assessed.

CONCLUSIONS

EBCT is very accurate in detecting significant coronary artery lesions in patients after acute myocardial infarction, but differentiation between occluded and patent infarct related arteries is currently unreliable.

[Noninvasive imaging of coronary arteries with electron beam tomography (EBCT)]

Coronary angiography remains the diagnostic standard for establishing the presence, site, and severity of coronary artery disease. Electron beam computed tomography (EBCT), a non-invasive imaging method with very high spatial and temporal resolution, is well suited for cardiac imaging. Using a standard protocol, EBCT permits the visualization of the coronary arteries. Stenoses and occlusions of the native arteries and of coronary artery bypass grafts can be reliably diagnosed. Extremely calcified segments have to be excluded from evaluation. Reduced image quality, mainly due to fast vessel motion and superposition of large veins, impairs the results obtained for the right and left circumflex coronary artery. Possible clinical applications are the follow-up after angioplasty (PTCA without stent) and bypass surgery, the exclusion of coronary artery disease in patients with low likelihood of disease, and the evaluation of coronary anomalies.

Imaging of the coronary arteries using magnetic resonance angiography

Magnetic resonance imaging of the coronary arteries is difficult due to the tortuous course of these vessels, their small diameter, and their rapid movement caused by respiration and cardiac contraction. Initial investigations could demonstrate the feasibility of non-invasive magnetic resonance coronary angiography using 2-dimensional turbo-FLASH gradient-echo sequences in repeated breathholds of approximately 16 heart beats duration. Further developments, especially the design of navigator-echo-based respiratory gated 3-dimensional imaging sequences, permitted the acquisition of contiguous volume data sets of the heart which eliminated many limitations of 2-dimensional repeated breathhold sequences. With a spatial resolution of approximately 1.2 x 1.2 x 2 mm and a temporal resolution of approximately 126 ms, several authors reported sensitivities of 70-80% and specificities of approximately 90% for the detection of coronary artery stenoses. Further improvements can be expected from new, intravascular contrast agents and from ultrafast sequences which permit acquisition of a sufficiently large imaging volume within one single breathold.

Prenatal diagnosis of QT prolongation by magnetocardiography

Magnetocardiography constitutes a new tool for monitoring fetal cardiac activity. The fetal magnetocardiogram (FMCG) recorded noninvasively over the maternal abdomen is detectable with high temporal resolution and permits analysis of all parts of the PQRST waveform. In this way measurements of cardiac time intervals, including the QT interval, become possible. The following article constitutes the first report of antenatal detection of QT prolongation in two fetuses by FMCG.

In-plane coronary arterial motion velocity: measurement with electron-beam CT

PURPOSE

To determine the speed of and changes in the speed of coronary arterial movement during the cardiac cycle with electron-beam computed tomography (CT).

MATERIALS AND METHODS

With electron-beam CT, 20 consecutive cross-sectional images were acquired at the mid right coronary artery (with 50-msec acquisition time, 8-msec intersection delay, 7-mm section thickness, and intravenous administration of 40 mL of contrast agent) in 25 patients. On the basis of the displacement of the left anterior descending, left circumflex, and right coronary arterial cross sections from image to image, movement velocity in the transverse imaging plane was calculated and was correlated with the simultaneously recorded electrocardiogram.

RESULTS

The velocity of in-plane coronary arterial motion varied considerably during the cardiac cycle. Peaks were caused by ventricular systole and diastole and by atrial contraction. The mean velocity was 46.6 mm/sec +/- 12. 5 (SD). The mean velocity of right coronary arterial movement (69.5 mm/sec +/- 22.5) was significantly faster than that of the left anterior descending (22.4 mm/sec +/- 4.1) or the left circumflex coronary artery (48.4 mm/sec +/- 15.0). The lowest mean velocity (27. 9 mm/sec) was at 48% of the cardiac cycle.

CONCLUSION

The lowest velocity of coronary arterial movement, which displays considerable temporal variation, was at 48% of the cardiac cycle.

Noninvasive detection of coronary artery stenosis using contrast-enhanced three-dimensional breath-hold magnetic resonance coronary angiography

OBJECTIVES

The purpose of this study was to evaluate a contrast-enhanced three-dimensional (3D) breath-hold magnetic resonance (MR) technique for detection of coronary artery stenoses.

BACKGROUND

The accuracy of previously published MR coronary angiography protocols varies widely. Recently, coronary artery imaging using T1-shortening contrast agent has become possible, but so far there are no data concerning its clinical application.

METHODS

Magnetic resonance coronary angiography was performed in 50 patients with suspected coronary artery disease. Magnetic resonance data acquisition using an ultrafast 3D gradient-echo sequence lasted over 32 heartbeats within one single breath-hold. Twenty milliliters of gadopentetate dimeglumine was injected at a flow rate of 1 ml/s for two successive studies covering the main coronary arteries in single-oblique planes. Stenosis assessment by MR was compared with significant (diameter stenosis > 50%) stenoses on X-ray angiography. Evaluation was limited to the proximal and mid-coronary artery segments.

RESULTS

Two hundred sixty-eight of 350 artery segments (76.6%) could be evaluated. Left circumflex coronary artery was only evaluable in 50% of cases by MR. In the evaluable segments, 48 of 56 stenoses and 193 of 212 nonstenotic segments were correctly classified by MR. On a patient basis, MR correctly identified 34 of 36 patients with and 8 of 14 patients without significant coronary stenoses as demonstrated by X-ray angiography (sensitivity 94.4%, specificity 57.1%).

CONCLUSIONS

Oblique projection contrast-enhanced MR coronary angiograms obtained within one single breath-hold permit identification of patients with coronary stenoses in the proximal and mid segments of the major coronary arteries with satisfactory accuracy.

[Hypereosinophilia with myocardial involvement due to toxocariasis. Diagnosis of regional myocardial perfusion abnormalities by pulsed tissue Doppler echocardiography]

CASE REPORT

The case of a 57-year-old woman is reported who was admitted for peripheral hypereosinophilia.

DIAGNOSIS

Detailed investigations revealed first of all a hypereosinophilic syndrome with infiltration of bone marrow and lung. The patient suffered more and more from angina pectoris with signs of heart failure. Coronary angiography was therefore carried out which showed normal coronary arteries. With suspicion of myocardial involvement endomyocardial biopsies were performed which revealed the presence of Löfflers endocarditis parietalis fibroplastica. Finally, serological studies for parasites disclosed a positive ELISA test for Toxocara, confirmed later to be rising.

CONCLUSION

Myocardial involvement of hypereosinophilia, caused by Toxocara is not described until now. Further diagnostic by means of pulsed wave tissue Doppler echocardiography provided regional differentiation of a restrictive filling pattern which documented the importance of this new diagnostic tool in myocardial illness.

Coronary arteries: MR angiography with fast contrast-enhanced three-dimensional breath-hold imaging--initial experience

Gadolinium-enhanced, three-dimensional, breath-hold magnetic resonance (MR) coronary angiography was performed in two healthy volunteers and 11 patients suspected or known to have coronary artery disease. MR angiograms were compared with those obtained with retrospective respiratory gating. Of 52 main coronary arteries, 47 could be visualized with the breath-hold technique and 49 with the gating technique. Signal-to-noise and contrast-to-noise ratios were significantly higher with the breath-hold technique. Overall image quality was slightly lower with breath-hold imaging. With either technique, three of five, significant coronary stenoses were correctly identified.

Biomagnetic localization of electrical current sources in the human heart with realistic volume conductors using the single-current-dipole model

The boundary element method was applied in order to investigate the localization accuracy for focal sources measured from MCG data. Various homogeneous volume conductor models were composed: the individually shaped torso, a scaled standard torso, an unscaled standard torso, a scaled cuboid and a scaled ellipsoid. We implemented these models in single-dipole inverse solution techniques. High resolution multichannel data were analysed from two patients showing ventricular extrasystoles and two patients suffering from Wolff-Parkinson-White syndrome. Moreover, we report the localization of shallow- and deep-lying catheters (depth 9 cm and depth 17.5 cm below the measurement grid). Using an individually shaped homogeneous torso yields a localization error of less than 3 cm even for the deepest sources (mean error 2.4 cm). Probability-based dipole localization shows that the remaining error could only partly be explained by data noise statistics. Therefore it seems to be due to either inner inhomogeneities or the inadequacy of the single current dipole or a combination of the two. Thus clinically useful localization accuracy in the millimetre range requires more sophisticated volume conductor and source models. The evaluation of measurement data and simulation study shows that a scaled cuboid model can provide nearly the same localization accuracy as the individually shaped torso model. Single dipole reconstruction with this model is computationally faster than that with the individually shaped model of the human body and is fast enough for use in clinical applications.

Value of electron-beam computed tomography for the noninvasive detection of high-grade coronary-artery stenoses and occlusions

BACKGROUND

Reliable noninvasive assessment of coronary-artery stenoses and occlusions would constitute an advantage in the care of patients with known or suspected coronary artery disease. We investigated the accuracy of contrast-enhanced electron-beam computed tomography (CT) for the detection of high-grade coronary-artery stenoses and occlusions.

METHODS

Electron-beam CT was performed in 125 patients. After intravenous injection of a contrast agent, 40 cross-sectional images of the heart were acquired during inspiration, triggered by the electrocardiogram in diastole. Three-dimensional reconstructions of the heart and coronary arteries were rendered to facilitate evaluation of the images. The proximal and middle segments of the major coronary arteries were evaluated for the presence or absence of high-grade stenoses and occlusions. The results were compared with those of invasive coronary angiography in a blinded fashion.

RESULTS

Because of technical problems that impaired the quality of the images, 124 (25 percent) of the 500 coronary arteries studied (left main, left anterior descending, left circumflex, and right coronary) in a total of 125 patients were excluded from evaluation. No vessels could be evaluated in 19 patients (15 percent), and another 28 patients (22 percent) had one, two, or three vessels that could not be evaluated. In the remaining coronary arteries with adequate image quality, electron-beam CT permitted visualization of 69 of 75 high-grade stenoses and occlusions (sensitivity, 92 percent), whereas in 282 of 301 arteries, the absence of high-grade stenoses and occlusions was correctly detected (specificity, 94 percent).

CONCLUSIONS

When image quality is adequate, electron-beam CT may be useful to detect or rule out high-grade coronary-artery stenoses and occlusions.

[Possibilities and limits of electron beam tomography]

Electron beam CT, which does not require mechanical movement of an X-ray tube, has a temporal resolution which exceeds that of conventional computed tomography by a factor of about ten. Axial images of the heart can be acquired within 50 to 100 ms with a spatial resolution below 0.5 mm2 and permit precise visualization of all cardiac structures. ECG-triggered acquisition of 30 to 40 axial images (3 mm slice thickness) in a short inspiratory breathhold allows one to sample a 3-dimensional volume data set which covers the complete heart. Overall acquisition times are approximately 30 to 50 seconds. While electron beam CT in general permits a complete cardiac investigation, including morphology, function, and perfusion, the method's most important application is non-invasive imaging of the coronary arteries. Without contrast enhancement, coronary calcifications by EBCT currently constitutes the most sensitive non-invasive marker for the presence even of very early forms of coronary atherosclerosis. Intravenous injection of contrast agent during image acquisition additionally permits the selective visualization of the coronary artery lumen and detection of significant stenoses. This method is especially well suited in the follow-up of coronary interventions and coronary bypass grafting. Breathhold and movement artifacts, superposition of coronary arteries and veins, as well as severe coronary calcifications currently constitute the method's main problems. In spite of these limitations, electron beam CT has been shown to permit clinically valuable non-invasive investigations of the coronary arteries, which may be further refined as technology progresses.

Assessment of coronary blood flow in humans using phase difference MR imaging. Comparison with intracoronary Doppler flow measurement

Coronary blood flow quantification provides essential information on the hemodynamic significance of coronary artery stenoses. Recently, magnetic resonance (MR) flow mapping has emerged as a new promising method to noninvasively determine flow velocity and flow volume within the coronary arteries. The aim of this study was to compare phase difference (PD) MR flow quantification with intracoronary Doppler flow measurements in 15 patients with suspected or known coronary artery disease. Flow quantification was attempted before and after systemic application of 5mg Isosorbiddinitrate (ISDN) in order to determine possible alterations in coronary flow volume. PD MR flow mapping was performed successfully in 13 of the 15 patients. For flow velocities and flow volume values, a close correlation between PD MR and Doppler flow measurements was found (r = 0.79 and r = 0.90, respectively). However, average flow measured by PD MR was significantly lower than the invasively obtained values (9.0 +/- 4.4 cm/sec vs. 11.7 +/- 4.9 cm/sec; p < 0.001 and 46.3 +/- 28.7 ml/min vs. 53.4 +/- 32.8 ml/min; p < 0.05). Although the mean flow volume remained constant in the entire patient group after ISDN application, individual changes (increase in 6, decrease in 4 cases) could be documented with PD MR imaging and showed a good correlation to the Doppler method (r = 0.82). In conclusion, PD MR flow mapping is a promising method for the noninvasive quantification of coronary blood flow and therefore offers the potential of assessing coronary artery stenoses. However, technical improvements are mandatory in order to increase accuracy of the method.

Non-invasive diagnosis of a congenital coronary artery fistula

This report describes a large congenital coronary artery fistula of the left circumflex artery draining into the coronary sinus in a 46 year old woman. The fistula was initially diagnosed by cross-sectional and transesopha-geal echocardiography using multiplane probe. Additionally, the entire course of the fistula was visualised in electron beam tomography. Angiography confirmed echocardiographic and tomographic findings.

Curved multiplanar reconstructions for the evaluation of contrast-enhanced electron beam CT of the coronary arteries

OBJECTIVE

We investigated the applicability of curved multiplanar reconstructions for the evaluation of contrast-enhanced electron beam CT scans of the coronary arteries.

SUBJECTS AND METHODS

Thirty-two patients (43-72 years old; mean age, 58 years old) underwent electron beam CT. After injection of i.v. contrast medium, 40 axial cross sections of the heart were acquired, triggered to the ECG during breath-hold (3-mm slice thickness, 1-mm overlap). Curved multiplanar reconstructions were obtained separately for each coronary artery. The reconstructions were independently evaluated by two investigators for the presence of high-grade stenoses and occlusions. The results were then compared with coronary angiography results, of which the two investigators had been unaware.

RESULTS

Because of degraded image quality, 15 (12%) of the 128 vessels (left main, left anterior descending, left circumflex, and right coronary arteries in 32 patients) were excluded from evaluation. In the remaining 113 vessels, 16 (89%) of 18 high-grade stenoses and occlusions were correctly detected (89% sensitivity). Absence of significant stenosis was correctly detected in 87 (92%) of 95 vessels (92% specificity). The negative and positive predictive values were 98% and 67%, respectively.

CONCLUSION

Curved multiplanar reconstructions are useful in the evaluation of contrast-enhanced electron beam CT scans of coronary arteries.

A simple computer model to simulate ECG based on ionic channels

The presented computer model reconstructs the ECG with 500 myocardium cells based on seven ionic channels. The low hardware-requirement and the exact demonstration of physiological and pathophysiological coherence make this simulation model very useful for medical scientific education.