[Benefits of cardiac magnetic resonance diagnostics in patients with heart rhythm disorders : From risk stratification to interventional procedures]. / Nutzen der kardialen Magnetresonanzdiagnostik für Patienten mit Herzrhythmusstörungen : Von der Risikostratifizierung bis zur Intervention.

Cardiac magnetic resonance imaging (cMRI) now rates among the established diagnostic procedures for the clarification of cardiac disease patterns. In modern clinical electrophysiology, apart from providing basic cardiac diagnostics of patients prior to interventional procedures, the imaging method enables the three-dimensional reconstruction of cardiac target structures of the planned ablation procedure, which can significantly improve the safety and efficacy of the intervention. Furthermore, cMRI has a high significance with respect to risk stratification during implantable cardioverter defibrillator (ICD) evaluation. In addition to an exact determination of ventricular function, its capability for detailed tissue characterization enables the visualization and quantification of fibrotic lesions and scar tissue as potential arrhythmogenic triggers. This anatomic assignment also enables an increased accuracy of the ablation of substrate-based arrhythmia. In comparison to this the interventional cMRI as a direct interface between cMRI and invasive electrophysiology represents a comparably new field of application. Initial clinical experiences in the field of ablation of typical atrial fibrillation could not only confirm the feasibility of the concept but also enabled recognition of the clear advantages of an imaging-guided electrophysiological procedure.

[MRI-based catheter ablation : Current status and outlook]. / MRT-basierte Katheterablation : Aktueller Stand und Ausblick.

Fluoroscopy-based catheter ablation has established itself as a standard procedure for the treatment of patients with cardiac arrhythmias. However, it is subject to certain limitations with regard to the visualization of arrhythmogenic substrate and ablation lesions and is associated with radiation exposure. Within the framework of studies, initial experience with MRI-based, radiation-free electrophysiological examinations and ablations could be gained. The integration of MRI technology into electrophysiological procedures promises numerous advantages. The ability to operate in a radiation-free environment during MRI-based catheter ablation is significant and promising. Furthermore, MRI provides important procedure-relevant information in terms of visualization of individual arrhythmogenic substrate. In order to further improve immediate and long-term ablation success, especially in the context of complex arrhythmias and structural heart disease, the direct and successful integration of MRI-generated findings into the ablation process is of utmost importance. The future of MRI-based catheter ablation could thus lie in particular in the treatment of more complex cardiac arrhythmias, which require personalized therapy paths. In this respect, however, the data situation is still extremely limited. Further technical developments and larger studies are indispensable in order to gain further important insights into the feasibility, safety and success rate of MRI-based invasive electrophysiological diagnostics and therapy in comparison to conventional ablation methods.

Evaluation of the right heart using cardiovascular magnetic resonance imaging in patients with cardiac devices.

BACKGROUND: Patients with cardiac implantable electronic devices (CIED) necessitate comprehensive cardiovascular magnetic resonance (CMR) examinations. The aim of this study was to provide data on CMR image quality and feasibility of functional assessment of the right heart in patients with CIED depending on the device type and imaging sequence used. METHODS: 120 CIED carriers (Insertable cardiac monitoring system, n = 13; implantable loop-recorder, n = 22; pacemaker, n = 30; implantable cardioverter-defibrillator (ICD), n = 43; and cardiac resynchronization therapy defibrillator (CRT-D), n = 12) underwent clinically indicated CMR imaging using a 1.5 T. CMR protocols consisted of cine imaging and myocardial tissue characterization including T1-and T2-weighted blackblood imaging and late gadolinium enhancement (LGE) imaging. Image quality was evaluated with regard to device-related imaging artifacts per right-ventricular (RV) segment. RESULTS: RV segmental evaluability was influenced by the device type and CMR imaging sequence: Cine steady-state-free-precision (SSFP) imaging was found to be non-diagnostic in patients with ICD/CRT-D and implantable loop recorders; a significant improvement of image quality was achieved when using cine turbo-field-echo (TFE) sequences with a further improvement on post-contrast TFE imaging. LGE scans were artifact-free in at least 91% of RV segments with best results in patients with a pacemaker or an insertable cardiac monitoring system. CONCLUSIONS: In patients with CIED, artifact-free CMR imaging of the right ventricle was performed in the majority of patients and resulted in highly reproducible evaluability of RV functional parameters. This finding is of particular importance for the diagnosis and follow-up of right-ventricular diseases.

[Consensus recommendations of the German Radiology Society (DRG), the German Cardiac Society (DGK) and the German Society for Pediatric Cardiology (DGPK) on the use of cardiac imaging with computed tomography and magnetic resonance imaging]. / Konsensusempfehlungen der DRG/DGK/DGPK zum Einsatz der Herzbildgebung mit Computertomografie und Magnetresonanztomografie.

Cardiac magnetic resonance imaging (MRI) and computed tomography (CT) have been developed rapidly in the last decade. Technical improvements and broad availability of modern CT and MRI scanners have led to an increasing and regular use of both diagnostic methods in clinical routine. Therefore, this German consensus document has been developed in collaboration by the German Cardiac Society, German Radiology Society, and the German Society for Pediatric Cardiology. It is not oriented on modalities and methods, but rather on disease entities. This consensus document deals with coronary artery disease, cardiomyopathies, arrhythmias, valvular diseases, pericardial diseases and structural changes, as well as with congenital heart defects. For different clinical scenarios both imaging modalities CT and MRI are compared and evaluated in the specific context.

High spatial resolution myocardial perfusion imaging during high dose dobutamine/atropine stress magnetic resonance using k-t SENSE.

PURPOSE: To prospectively evaluate the feasibility and diagnostic accuracy of high spatial resolution myocardial perfusion imaging during high dose dobutamine/atropine stress magnetic resonance (DSMR) for the detection of coronary artery disease (CAD). METHODS AND RESULTS: DSMR-wall motion was combined with perfusion imaging (DSMR-perfusion) in 78 patients prior to clinically indicated invasive coronary angiography. For DSMR-perfusion an in-plane spatial resolution of 1.5 × 1.5mm(2) was attained by using 8 × k-space and time sensitivity encoding (k-t SENSE). Image quality and extent of artifacts during perfusion imaging were evaluated. Wall motion and perfusion data were interpreted sequentially. Significant CAD (stenosis ≥ 70%) was present in 52 patients and involved 86 coronary territories. One patient did not reach target heart rate despite maximum infusion of dobutamine/atropine. Two studies (3%) were non-diagnostic due k-t SENSE related artifacts resulting from insufficient breathhold capability. Overall image quality was good. Dark-rim artifacts were limited to the endocardial border at a mean width of 1.8mm. The addition of DSMR-perfusion to DSMR-wall motion data improved sensitivity for the detection of CAD (92% vs. 81%, P=0.03) and accurate determination of disease extent (85% vs. 66% of territories, P<0.001). There were no significant differences between DSMR-perfusion and DSRM-wall motion regarding overall specificity (83% vs. 87%, P=1) and accuracy (89% vs. 83%, P=0.13). CONCLUSION: High spatial resolution DSMR-perfusion imaging at maximum stress level was feasible, improved sensitivity over DSMR-wall motion for the detection of CAD and allowed an accurate determination of disease extent. Specificity of DSMR-perfusion with k-t SENSE improved compared to prior studies using lower spatial resolution.

Value of additional myocardial perfusion imaging during dobutamine stress magnetic resonance for the assessment of intermediate coronary artery disease.

This study was performed to assess the role of additional myocardial perfusion imaging during high dose dobutamine/atropine stress magnetic resonance (DSMR-wall motion) for the evaluation of patients with intermediate (50-70%) coronary artery stenosis. Routine DSMR-wall motion was combined with perfusion imaging (DSMR-perfusion) in 174 consecutive patients with chest pain syndromes who were scheduled for a clinically indicated coronary angiography. When defining CAD as the presence of a ≥ 50% stenosis, the addition of perfusion imaging improved sensitivity (90 vs. 79%, P < 0.001) with a non-significant reduction in specificity (85 vs. 90%, P = 0.13) and an improvement in overall diagnostic accuracy (88 vs. 84%, P = 0.008). Adding perfusion imaging improved sensitivity in patients with intermediate stenosis (87 vs. 72%, P = 0.03), but not in patients with severe (≥70%) stenosis (93 vs. 84%, P = 0.06). In patients with severe stenosis specificity of DSMR-perfusion versus DSMR-wall motion decreased (61 vs 70%, P = 0.001) resulting in a lower overall accuracy (71 vs 74%, P = 0.03). Using a cutoff of ≥50% for the definition of CAD, sensitivity of DSMR-perfusion compared to DSMR-wall motion was significantly higher in patients with single vessel (88 vs. 77%, P = 0.03) and multi vessel disease (93 vs. 79%, P = 0.03), whereas no significant differences were found using a cutoff of ≥70% stenosis for the definition of CAD. The addition of perfusion imaging during DSMR-wall motion improved the sensitivity in patients with intermediate coronary artery stenosis. Overall diagnostic accuracy increased only when defining CAD as ≥50% stenosis. In patients with ≥70% stenosis DSMR-wall motion alone had higher accuracy due to more false-positive cases with DSMR-perfusion.

Dobutamine stress magnetic resonance imaging for the detection of coronary artery disease in women.

BACKGROUND: Dobutamine stress magnetic resonance (DSMR) imaging represents an excellent imaging approach for the detection of coronary artery disease (CAD). However, most studies have predominantly reported the utility of DSMR in men. OBJECTIVE: To evaluate the diagnostic value of DSMR in men and women. METHODS AND RESULTS: High-dose dobutamine/atropine stress magnetic resonance imaging was performed and new or worsening wall motion abnormalities evaluated in 745 consecutive patients (204 women, 541 men). Invasive coronary angiography was performed within 30 days and served as the reference standard (> or =70% stenosis). DSMR was technically successful and had diagnostic image quality in all patients except one woman and three men (p=NS). In the absence of ischaemia, target heart rate was not reached in 9.3% of women and 8.5% of men (P=NS) despite maximum pharmacological infusion (1% and 2.2%, respectively, p=NS) or owing to limiting side effects (8.3% and 6.3%, respectively, p=NS). Diagnostic values (sensitivity/specificity/accuracy) for the detection of significant coronary stenoses were similar for men (86%/83%/85%) and women (85%/86%/85%). There was no gender-based difference in regional diagnostic accuracy of DSMR for all three coronary vascular territories in patients with single-vessel CAD (81% vs 81%, p=NS, respectively). CONCLUSION: The diagnostic capability of DSMR for the detection of haemodynamically relevant, obstructive CAD is independent of gender.

MR coronary artery imaging with 3D motion adapted gating (MAG) in comparison to a standard prospective navigator technique.

Magnetic resonance coronary angiography (MRCA) has been proven to be feasible for imaging of the proximal and medial portions of the three main coronary arteries. Free breathing techniques allow for high resolution imaging but prolong scan time. This could potentially be shortened by improving the efficiency, robustness and accuracy of the navigator gating algorithm. Aim of this study was to determine the feasibility, efficiency, and image quality of a new motion compensation algorithm (3D-MAG) for coronary artery imaging with navigator techniques. In 21 patients the coronaries were imaged in plane with a 3D k-space segmented gradient echo sequence. A T2 preparation prepulse was used for suppression of myocardial signal, during free breathing and a navigator technique with using real time slice following and a gating window of 5 mm was applied to suppress breathing motion artefacts. Imaging was performed with standard gating and compared to 3D-MAG. Image quality was visually compared, contrast-to-noise and signal-to-noise ratio were calculated, the length of visualized coronary arteries was measured and scan duration and scan efficiency were calculated. Standard navigator imaging was feasible in 19 of 21 (90.5%) patients 3D-MAG in 21/21 (100%). Scan efficiency and duration was significantly improved with 3D-MAG (p < .05) without change in image quality. 3D-MAG is superior to conventional navigator correction algorithms. It improves feasibility and scan efficiency without reduction of image quality. This approach should be routinely used for MR coronary artery imaging with navigator techniques.

Primary fibrosarcoma of the liver infiltrating the right atrium of the heart.

A rare case of a primary fibrosarcoma of the liver infiltrating the right heart is described in a 72-year-old woman. The patient presented with a history of progressive dyspnea and ascites and her general condition was poor. Preoperative cardiac magnetic resonance (CMR) imaging revealed a large mass, which originated from the liver and had infiltrated the right atrium via the inferior vena cava. The patient underwent tumor resection yet died shortly afterwards. Histologically the mass was classified as a fibrosarcoma with positive immunostaining for vimentin. We report the CMR imaging characteristics in this uncommon case. Preoperative CMR proved to be useful for clinical decision making and the planning of surgery.

Determinants of myocardial response in CMR perfusion imaging using Gd-BOPTA (Multihance).

PURPOSE: Different centers and vendors use different sequences and contrast agent application schemes for MR myocardial perfusion imaging. The purpose of this study was to evaluate the role of different sequences, dosages, and injection speeds of contrast media for semiquantitative MR-perfusion assessment. METHODS: In a pilot study with 58 consecutive patients three of the most commonly used sequences for MR myocardial perfusion imaging (T1-GrE, GrE-EPI or SSFP) were compared to each other in terms of peak myocardial enhancement and image quality. For the main part of the study dynamic first pass MR perfusion imaging (Philips Intera CV, Best, Tthe Netherlands) was performed in 24 patients using the most favorable sequence from the pilot study (SSFP) after peripheral i.v. administration of Gd-BOPTA during adenosine stress. Two doses (0.05 mmol/kg bw and 0.025 mmol/kg bw) and four different injection speeds (8, 4, 3, 2 ml/s) were used. Signal intensity time curves were determined in the LV and myocardial segments supplied by normal coronary arteries and correlation between LV and myocardial upslope as well as peak enhancement were noted. RESULTS: The SSFP-sequence showed a higher peak enhancement when using 0.05 mmol/kg bw of Gd-BOPTA and a superior image quality for both dosage regimen compared with the other sequences and was consequently applied for the main study. A significant correlation was found between the upslopes in the LV and the myocardium (r square = 0.85, p < 0.001). However, LV and myocardial upslopes were largely independent of the dosage. Myocardial upslope was significantly slower at an injection rate of 2 ml/s compared to 3 and 4 ml/s. Higher Gd-doses led to significantly higher enhancement (p < 0.001). CONCLUSION: In healthy myocardial segments, the myocardial upslope is mainly determined from the LV upslope. Both myocardial enhancement and upslope are largely independent from the injection rate of a contrast agent bolus as long as the injection speed is not below 3 ml/s. Myocardial enhancement, however, is dose dependent. Thus, a simple correction for LV upslope allows to normalize a wide variety of input parameters. Differences of myocardial upslope or peak signal intensity after correction should be mainly dependent on blood flow.

Comparison of dobutamine stress magnetic resonance, adenosine stress magnetic resonance, and adenosine stress magnetic resonance perfusion.

BACKGROUND: Dobutamine stress MR (DSMR) is highly accurate for the detection of inducible wall motion abnormalities (IWMAs). Adenosine has a more favorable safety profile and is well established for the assessment of myocardial perfusion. We evaluated the diagnostic value of IWMAs during dobutamine and adenosine stress MR and adenosine MR perfusion compared with invasive coronary angiography. METHODS AND RESULTS: Seventy-nine consecutive patients (suspected or known coronary disease, no history of prior myocardial infarction) scheduled for cardiac catheterization underwent cardiac MR (1.5 T). After 4 minutes of adenosine infusion (140 microg x kg(-1) x min(-1) for 6 minutes), wall motion was assessed (steady-state free precession), and subsequently perfusion scans (3-slice turbo field echo-echo planar imaging; 0.05 mmol/kg Gd-BOPTA) were performed. After a 15-minute break, rest perfusion was imaged, followed by standard DSMR/atropine stress MR. Wall motion was classified as pathological if > or =1 segment showed IWMAs. The transmural extent of inducible perfusion deficits (<25%, 25% to 50%, 51% to 75%, and >75%) was used to grade segmental perfusion. Quantitative coronary angiography was performed with significant stenosis defined as >50% diameter stenosis. Fifty-three patients (67%) had coronary artery stenoses >50%; sensitivity and specificity for detection by dobutamine and adenosine stress and adenosine perfusion were 89% and 80%, 40% and 96%, and 91% and 62%, respectively. Adenosine IWMAs were seen only in segments with >75% transmural perfusion deficit. CONCLUSIONS: DSMR is superior to adenosine stress for the induction of IWMAs in patients with significant coronary artery disease. Visual assessment of adenosine stress perfusion is sensitive with a low specificity, whereas adenosine stress MR wall motion is highly specific because it identifies only patients with high-grade perfusion deficits. Thus, DSMR is the method of choice for current state-of-the-art treatment regimens to detect ischemia in patients with suspected or known coronary artery disease but no history of prior myocardial infarction.

Improved functional cardiac MR imaging using the intravascular contrast agent CLARISCAN.

PURPOSE: Using segmented k-space turbo gradient echo MR techniques (TGE) contrast between blood and myocardium is often reduced in long axis views due to reduced in plane spin-refreshment, particularly in patients with low ejection fraction. The application of an intravascular contrast agent (CA) may improve endocardial border delineation. MATERIALS AND METHODS: In 15 patients cardiac cine loops in two long axis and two short axis views were acquired during breath hold using a TGE sequence without and with increasing doses of CA (0.75, 2.0, 5.0 mg Fe/kg). Two independent observers evaluated left ventricular function (LVEF, modified Simpson's rule) and assigned a visual score (range: 0 = 'not visualized' to 6 = 'excellent visualization') for endocardial border delineation. Signal- and contrast-to-noise ratios (SNR; CNR) were determined. RESULTS: Endocardial border delineation score for TGE was 1.7 +/- 0.6 and 3.9 +/- 0.6**, 4.4 +/- 0.5**, 4.6 +/- 0.4** for 0.75, 2.0, 5.0 mg Fe/kg of CA, respectively (**p < 0.01 vs. TGE). SNR of blood increased significantly with any dose of CA with a mild drop of myocardial SNR resulting in a significant increase of CNR blood/myocardium. The maximum effect with 2.0 mg Fe/kg was a >2-fold CNR increase. Inter- and intraobserver variability assessed according to the method of Bland-Altmann was reduced at 2.0 mg Fe/kg for determination of LVEF and reached statistical significance for LVEF <50%. CONCLUSION: Intravascular CA increased CNR between blood and myocardium by a factor >2 and significantly improved the determination of cardiac volumes. The benefit in accuracy was most for patients with left ventricular ejection fraction <50%.

Functional cardiac MR imaging with steady-state free precession (SSFP) significantly improves endocardial border delineation without contrast agents.

Contrast between blood and myocardium in standard turbo gradient echo MR techniques (TFE) used routinely in clinical practice is mainly caused by unsaturated inflowing blood. Steady-state free precession (SSFP) has excellent contrast even in the absence of inflow effects. In 45 subjects cardiac cine loops in two long axis projections were acquired using TFE and compared with SSFP. A visual score (range 0 worst - 3 best) was assigned for endocardial border delineation for six myocardial segments in two long axis views. Endocardial border delineation score for TFE was 1.3 +/- 0.3 per segment and 2.4 +/- 0.3 for SSFP (P < 0.0001). Signal intensity blood/signal intensity myocardium was 1.5 +/- 0.4 at enddiastole and 1.4 +/- 0.3 at systole for TFE and 3.5 +/- 1.1 and 3.2 +/- 1.3 for SSFP, respectively (P < 0.0001). SSFP increases contrast between blood and myocardium more than twofold, resulting in an improved endocardial border definition. This may reduce variability for the determination of cardiac volumes and ejection fraction.

Improvement of myocardial perfusion reserve early after coronary intervention: assessment with cardiac magnetic resonance imaging.

OBJECTIVES: The purpose of this study was to determine the potential value of magnetic resonance myocardial perfusion in the follow-up of patients after coronary intervention. BACKGROUND: In some patients a residual impairment of myocardial perfusion reserve (MPR) early after successful coronary intervention has been observed. In this study we evaluated an MPR index before and after intervention with magnetic resonance. METHODS: Thirty-five patients with single- and multivessel coronary artery disease were studied before and 24 h after intervention. The signal intensity time curves of the first pass of a gadolinium-diethylene triamine pentacetic acid bolus injected via a central vein catheter were evaluated before and after dipyridamole infusion. The upslope was determined using a linear fit. Myocardial perfusion reserve index was estimated from the alterations of the upslope. RESULTS: The MPR index in segments perfused by the stenotic artery was significantly lower than in the control segments (1.07 +/- 0.24 vs. 2.18 +/- 0.35, p < 0.001) and improved significantly after intervention (1.89 +/- 0.39, p < 0.001) but did not normalize completely (p < 0.01). After intervention the MPR index remained significantly lower in the balloon percutaneous transluminal coronary angioplasty group (1.72 +/- 0.38; n = 13) in comparison with the stent group (1.99 +/- 0.36, n = 18, p < 0.05). In the stent group a complete normalization of the MPR index was found 24 h after stenting. CONCLUSIONS: Magnetic resonance perfusion measurements allow a reliable assessment of MPR index. An improvement of MPR index can be observed after coronary intervention, which is more pronounced after stenting. Magnetic resonance perfusion measurements allow the assessment and may be useful for the follow-up of patients with coronary artery disease after coronary intervention.

Modulation of contractions to ergonovine and methylergonovine by nitric oxide and thromboxane A2 in the human coronary artery.

This study explored the modulatory effects of nitric oxide and thromboxane A2 on contractions to ergonovine and methylergonovine in human coronary arteries. To elucidate the different role of nitric oxide synthase in the response to the ergot alkaloids, the serotonin (5-HT) receptors involved in nitric oxide synthase in the response to the ergot alkaloids, the 5-HT receptors involved in nitric oxide release and the contraction of the vascular smooth muscle were characterized with more selective 5-HT-receptor agonists and antagonists. Rings of human coronary arteries from explanted hearts were suspended in organ chambers for isometric tension recording. After testing for contractile (potassium chloride, 60 mM) and endothelial function (substance P, 10(-8) M), respectively, they were exposed to ergot alkaloids or other agonists in the absence or presence of U 46619 (10(-9) M), or nitro-L-arginine (10(-4) M), or both. Ergonovine and methylergonovine were comparable, weak vasoconstrictors in untreated preparations. Contractions to ergonovine were augmented by U 46619, but not by nitro-L-arginine. Contractions to methylergonovine were augmented only by combining U 46619 and nitro-L-arginine. Serotonin and methylergonovine, but not ergonovine, elicited endothelium-dependent, nitric oxide-mediated relaxations. Nonselective 5-HT(1B/1D)-receptor stimulation caused both contractions and relaxations; selective 5-HT1B stimulation caused relaxations only. In the human coronary artery, contractions to ergonovine are not dependent on NO release but are synergistically augmented by thromboxane. Methylergonovine causes similar effects on the vascular smooth muscle, but contractions are inhibited by the release of NO from the endothelium. The 5-HT receptor on the endothelium appears to be different from the receptor on the vascular smooth muscle, which mediates the contractile response to the ergot alkaloids.