Thomas Wittlinger

Quantification of shunt volumes in congenital heart diseases using a breath-hold MR phase contrast technique: comparison with oximetry

Aims: Comparison of breath-hold MR phase contrast technique in the estimation of cardiac shunt volumes with the invasive oximetric technique. Methods and Results: Seventeen patients with various cardiac shunts (10 ASD, 3 VSD, 1 PDA, 3 PFO) and five healthy volunteers were investigated using a 1.5 Tesla system. The mean flow velocity, the mean volume flow and the transverse area in the ascending aorta and the left and right pulmonary artery were measured using the MR phase contrast breath-hold technique (through plane, FLASH 2D-sequence, TR/TE 11/5 ms, phase length 106 ms, VENC 250 cm/s). The ratio of mean flow in the pulmonary (Qp: sum of mean flows in the left and right pulmonary arteries) and the systemic circulation (Qs: mean flow in the ascending aorta) was calculated and compared with invasively measured Qp:Qs ratios. Oximetry was performed within 24 h of the MR investigation. The non-invasive shunt measurement in the 17 patients showed a mean Qp:Qs ratio of 2.00 ± 0.86. Comparing the MR data with the invasively measured Qp:Qs showed a correlation coefficient of r = 0.91 (p < 0.001). Conclusion: Cardiac shunt volumes can be measured reliably using a shorter acquisition time with breath-hold MR phase contrast technique.

Magnetic resonance imaging of coronary artery occlusions in the navigator technique

Non-invasive assessment of coronary arteries is possible with magnetic resonance imaging (MRI). Respiratory gated MR coronary angiography is a new imaging technique that permits reconstruction of the coronary arteries based on a three-dimensional (3D) data set obtained from the free-breathing patient. In this study, respiratory gated MR angiography (MRA) was performed to assess coronary artery occlusions. MRI was performed in 25 patients who had been referred for conventional coronary angiography because of suspected coronary artery disease. Coronary artery occlusion was evaluated in the proximal and middle vessel segments after multiplanar coronary reconstruction of the MR images. Five patients were excluded from the study; in the remaining 20 patients 120 coronary artery segments were analyzed. Good image quality could be obtained for 85% of the segments. Eighteen of the 24 occlusions were confirmed by MRI, the overall sensitivity was 75% and the specificity was 100%. The best results were found in the proximal left anterior descending (LAD) and descending parts of the right coronary artery (RCA), where all occlusions were confirmed. These results showed that coronary artery occlusions can be detected in the proximal and middle LAD and RCA using 3D respiratory gated MRA. Further technical improvements, especially in spatial resolution, are necessary before MRA can become a reliable diagnostic tool in the non-invasive evaluation of coronary arteries.

Late improvement of regional wall motion after the subacute phase of myocardial infarction treated by acute PTCA in a 6-month follow-up.

BACKGROUND The aim of this follow-up study was to investigate the late effects of acute coronary angioplasty (PTCA) on regional wall motion after the subacute phase of myocardial infarction (MI). METHODS AND RESULTS Seventeen patients were investigated initially at a median of 11 days and again at 6 months after acute PTCA for myocardial infarction (< 8 hours after onset of symptoms) by cardiac magnetic resonance imaging. Corresponding short-axis slices encompassing the left ventricle (LV) were acquired using a standard cine MR for regional wall motion analysis and using delayed contrast enhanced magnetic resonance imaging (ceMRI) for infarct size quantification. The infarct size was similar in the subacute phase and the 6 month follow-up (20.8 and 21.9%, respectively; n.s.). Regional wall motion improved significantly in the area of hyperenhancement [percentage wall thickening (PWT) 21.9% and 37.9%, p < 0.05] in contrast to remote normal myocardium (46.4% and 38.4%; n.s.). Regional wall motion was significantly poorer in transmural compared with nontransmural MI in the subacute stage, and a late improvement could only be observed in transmural MI. CONCLUSION Transmural areas of hyperenhancement displayed significant late long-term improvement of regional wall motion after acute PTCA, possibly related to prolonged stunning compared with nontransmural areas.

Diagnostic value of routine clinical parameters in acute myocardial infarction: a comparison to delayed contrast enhanced magnetic resonance imaging

Aims: Contrast enhanced magnetic resonance imaging (ceMRI) has been shown to reliably identify irreversible myocardial injury. The aim of this study was to compare the findings on ceMRI with routine clinical markers of myocardial injury in patients with acute myocardial infarction (MI). Methods and results: Twenty-four patients with acute MI were investigated at 1.5 T. The global myocardial function was analysed with a standard cine MR protocol and a stack of short axis slices encompassing the entire left ventricle. Corresponding short axis slices were acquired for delayed ceMRI 15–20 min after the administration of 0.2 mmol gadolinium–DTPA/kg body weight. Mass of hyperenhancement and peak creatine kinase release (peak CK) was determined for each patient. The presenting 12-lead ECG was analysed for ST-elevation on admission and later development of Q-waves. Mass of hyperenhancement correlated moderately well to peak CK (r = 0.65, p < 0.01) and endsystolic volume index (r = 0.55, p < 0.01). Mass of hyperenhancement was inversely correlated to ejection fraction (r = −0.50, p = 0.02). Neither the presence of ST elevation on the admission ECG nor the later development of Q-waves did relate to the transmural extent of hyperenhancement and to the mass of hyperenhancement. Conclusion: Mass of hyperenhancement significantly correlates to global myocardial function and to peak CK. However, there is no relationship between the findings in ceMRI and 12-lead ECG abnormalities on admission suggesting an advantage of ceMRI in defining transmural extent and depicting small areas of necrosis.

Linksventrikuläre Muskelmassenbestimmung bei Patienten mit dilatativer Kardiomyopathie mittels transthorakaler dreidimensionaler Echokardiographie

Conventional echocardiographic methods of measuring left ventricular mass (LVM) are limited by assumptions of ventricular geometry and image plane positioning. Three-dimensional (3D) echocardiography offers a promising new approach for more accurate determination of LVM. This study was performed to compare LVM measurement by one- (1D), two- (2D), and 3D echocardiography with magnetic resonance imaging (MRI) in patients (pts) with dilated cardiomyopathy (DCM). 36 pts (age 18 –74) with DCM underwent imaging by conventional 1D and 2D echocardiography as well as transthoracic 3D echocardiographic data acquisition. Also, pts were imaged with cardiac MRI. Due to echocardiographic and MRI quality and because of exclusion criterias from MRI, it was not possible to accomplish each LVM determination method for each patient. LVM was determined by Devereux and area-length algorithm for the conventional echocardiography. 3D echocardiographic data was calculated after manual delineation of endo- and epicardial boundaries – slice by slice (5 mm) – in 3 perpendicular cut planes. LVM was determined by multiplying the myocardial volume by the specific density of the myocardium. To determine LVM in MRI, the even summation of slices method for myocardial volume measurement was used defined by the endo- and epicardium in short axis images. There was no significant correlation (r = 0.42) for measuring LVM between 1D echocardiography and MRI in pts with DCM. A significant correlation was obtained between 2D (r = 0.64, p < 0.01) echocardiography and MRI as well between 3D (r = 0.78, p < 0.01) and MRI in determination of LVM. Compared with 1D and 2D echocardiography, the 3D analysis achieved a significantly higher agreement with the results of the MRI (1D: 399.2 g, 2D: 285.9 g, 3D: 172.6 g versus MRI: 199.1 g). Interobserver variability was 5.1% for measuring LVM by 3D echocardiography (1D: 11.2%, 2D: 9.1%). In conclusion, in pts with DCM the determination of LVM was incompletely characterized by 1D and 2D echocardiography compared with results of MRI. The best correlation and high agreement for determination of LVM was obtained with 3D echocardiography compared with MRI. Die Muskelmassenbestimmung bei Patienten mit dilatativer Kardiomyopathie (DCM) mittels der herkömmlichen Algorithmen der ein- (1D) und zweidimensionalen (2D) Echokardiographie gilt aufgrund der individuellen Konfiguration der vergrößerten Herzen bei diesen Patienten als unzuverlässig. Die echokardiographische Muskelmassenbestimmung (MMB) im transthorakal dreidimensionalen (3D) Verfahren läßt diesbezüglich exaktere Ergebnisse erwarten. Dies soll im Vergleich zur MMB mittels der Magnetresonanztomographie (MRT) überprüft werden. Untersucht wurden 36 Patienten (Alter 18–74 Jahre) mit DCM mittels herkömmlicher transthorakaler ein- und zweidimensionaler Echokardiographie sowie durch eine transthorakale 3D-Datenakquisition. Zudem wurden die Patienten einer MRT-Untersuchung des Herzens unterzogen. Eindimensional wurde die Muskelmasse nach Devereux bestimmt, zweidimensional nach der Flächenlängenmethode. Der 3D-Datensatz wurde durch manuelle Konturierung des Endo- und Epikards in 3 orthogonalen Schnittebenen “scheibchenweise” rekonstruiert, um dann aus dem algorithmisch bestimmten Muskelvolumen die linksventrikuläre Muskelmasse zu bestimmen. Diese wurde aus den MRT-Daten anhand von maximal 15 Kurzachsenschnitten durch Markierung der Endo- und Epikardgrenzen ermittelt. Hiernach zeigt sich, daß die MMB mittels des Algorithmus der 1D-Echokardiographie (r = 0,42, n. s.) nicht signifikant mit den Ergebnissen der Muskelmassenbestimmung durch die MRT korreliert. Dahingegen zeigt sich für die 2D-Echokardiographie (r = 0,64, p < 0,01) sowie die Berechnung aus dem 3D-Datensatz (r = 0,78, p < 0,01) bei Patienten mit DCM eine befriedigende Korrelation mit den Ergebnissen der MRT. Die echokardiographischen 1D- (MW: 399,2 g, p < 0,01) und 2D- (MW: 285,9 g, p < 0,01) Verfahren überschätzen die durch die MRT (MW: 199,1 g) bestimmte linksventrikuläre Muskelmasse, wohingegen die 3D-Analyse (MW: 172,6 g, n. s.) diesen Ergebnissen am nächsten kommt. Die Interobservervariabilität lag für die 3D-Muskelmassenbestimmung bei 5,1% (1D: 11,2%, 2D: 9,1%).

MR-Angiographie und Flussmessung in Koronararterien und koronaren Bypassgefäßen

Better MR image quality of coronary arteries and coronary grafts is the product of increased spatial and temporal resolution. Breathing artifacts could be reduced by implementing breath-holding and navigator techniques. With these developments normal coronary arteries can often be imaged reliably. Several trials have been performed in order to test the reliability of MR angiography to detect coronary artery stenosis. But up to now, sensitivity and specificity have proven to be too low to introduce these techniques in clinical routine. The patency of coronary grafts can be detected reliably using different MR techniques. Coronary flow reserve can be measured using the MR phase contrast technique. This noninvasive approach was tested in diseased coronary arteries and in graft stenoses. A reduced MR coronary flow reserve corresponded to reduced flow reserve measured invasively. Measurement of MR flow reserve in normal and diseased coronary grafts revealed significant differences (3.3±0.4 vs. 1.3±0.2). Die neuen Techniken der Magnetresonanztomographie ermöglichen eine verbesserte örtliche und zeitliche Auflösung und eine deutliche Reduktion der Störung der Bildgebung durch die Atembewegung. Dadurch ist die Bildgebung der nativen Koronaraterien und der koronaren Bypassgefäße erheblich verbessert worden, und normale Koronararterien können häufig gut dargestellt werden. Bei der Diagnose von Koronarstenosen haben die bisherigen klinischen Studien keine ausreichende Zuverlässigkeit gezeigt. Die Offenheitsbestimmung von Bypassgefäßen ist jedoch zuverlässig möglich. Die MR-Phasenkontrastmethode ist geeignet, die koronare Flussreserve in nativen Koronararterien und in koronaren Bypassgefäßen zu messen. Die Ergebnisse der MR-Messung der koronaren Flussreserve in normalen und stenosierten Koronararterien korrespondieren mit den Ergebnissen der invasiven Dopplermessung. Angiographisch normale und stenosierte koronare Bypassgefäße unterscheiden sich signifikant hinsichtlich der MR-Flussresreve (3,3±0,4 vs. 1,3±0,2).

ECTASIA AND ANEURYSM OF THE RIGHT CORONARY ARTERY RESULTING FROM A SHUNT TO THE CORONARY SINUS

A 65-year-old woman presented with a systolic-diastolic murmur. Further MRI investigations as well as angiography revealed an arteriovenous shunt to the coronary sinus via an enlarged right coronary artery (Figure 1A⇓ and 1B⇓). The distal part of this coronary artery was transformed to a large coronary aneurysm of such extent that the left atrium was compressed …

Diagnose eines intramyokardialen Hämatoms nach traumatischem Myokardinfarkt durch Magnetresonanztomographie

Thoraxverletzungen treten bei etwa 30% aller traumatisierten Patienten auf, wobei in den meisten Fällen Verkehrsunfälle die Ursache sind. Wir berichten über den Fall eines Patienten, der nach einem Skiunfall einen traumatischen Vorderwandinfarkt erlitt. Im weiteren Verlauf kam es zu einer ausgedehnten intramyokardialen Einblutung. Differentialdiagnostisch kam zunächst ein linksventrikuläres Pseudo- bzw. Pseudopseudoaneurysma in Frage, kernspintomographisch konnte jedoch durch den Nachweis eines schmalen Myokardsaums sowohl ventral als auch dorsal der Raumforderung die Diagnose eines intramyokardialen Hämatoms gestellt werden. Bei dem Patienten wurde daraufhin eine aortokoronare Bypass-Operation sowie eine Resektion des intramyokardialen Hämatoms durchgeführt. Die Diagnose konnte intraoperativ sowie histologisch bestätigt werden. Traumatic cardiac lesions occur in about 30% of all traumatized patients, in most cases they are due to traffic accidents. We report a patient who suffered from a traumatic anterior wall infarction following a ski accident. Consecutively, an extended intramyocardial hemorrhage occurred. A left ventricular pseudoaneurysm was considered first by echocardiography. Using MRI, an intramyocardial hemorrhage could be diagnosed because of a thin myocardial border surrounding the hematoma. Consecutively, the patient underwent CABG surgery as well as a resection of the intramyocardial hematoma. This diagnosis could be manifested surgically and histologically.

Möglichkeiten und Perspektiven der nichtinvasiven Bypassdiagnostik: Vergleich verschiedener kernspintomographischer Methoden mit der konventionellen Koronarangiographie

ZusammenfassungZiel: Das Studienziel war die kernspintomographische Evaluierung koronarer Bypassgefäße mit der Hast-, Fisp-3-D- und Navigatorsequenz unter besonderer Berücksichtigung der distalen Bypassanastomose. Patienten: Eingeschlossen wurden 25 Patienten mit 63 Bypassgefäßen und insgesamt 78 distalen Anastomosen. Ergebnisse: Mit der Haste- und der Fisp-3-D-Sequenz konnten 44 der 47 offenen und 14 der 16 verschlossenen Bypasses korrekt beurteilt werden, die Sensitivität und Spezifität betrugen 94% und 88%. Überlegen war die Haste-Sequenz (43/54) der Fisp-3-D-Sequenz (38/54) in der Beurteilung der distalen Anastomosen. Die Navigatorsequenz wies aufgrund der eingeschränkten Bildqualität lediglich eine Sensitivität von 74% und eine Spezifität von 63% auf. Schlussfolgerung: Mit der Kernspintomographie ist eine nichtinvasive Evaluierung koronarer Bypassgefäße möglich, wobei die Haste-Sequenz in der Beurteilung distaler Bypassanteile überlegen ist. Eine Verbesserung der Aussagekraft der Methode ist durch den Einsatz gefäßständiger Kontrastmittel sowie durch eine Verbesserung der räumlichen Auflösung zu erwarten.AbstractObjective: The aim of the study was to evaluate the patency of coronary artery bypass grafts (CABGs) with different MR imaging techniques. Patients: 25 patients with 63 bypass grafts and a total of 78 distal anastomoses were studied at a 1.5-Tesla scanner. A 2-D T2-weighted breath-hold turbo spin echo sequence (Haste), a 3-D breath-hold contrast-enhanced MR angiography sequence (Fisp-3-D), and 3-D angiography sequence in navigator techniques were used. Results: With the Haste and Fisp-3-D sequences, 44 of the 47 patent and 14 of the 16 occluded grafts were recognized, the sensitivity and specificity were 94% and 88%, respectively. With the Haste sequence, 80% (43/54) of the distal anastomoses were seen in good image quality, and with the Fish-3-D sequence 70% (38/54). The navigator sequence showed less sensitivity and specificity (74% and 63%, respectively). Conclusion: The patency of CABGs can be evaluated noninvasively with the Haste and the Fisp-3-D angiography sequences. Better results can be expected with the development of a blood-pool contrast medium and an improvement of the spatial resolution.

Kernspintomographische Flussquantifizierung in Koronargefäßen zur Evaluierung hochgradiger Koronarstenosen

Zusammenfassung.Ziel: Zweck der Studie war die Bestimmung des intrakoronaren Blutflusses im Verhältnis zum Aortenfluss bei Patienten mit hochgradigen Koronarstenosen. Die MR-Flussmessung wurde bei 15 Patienten in 18 Koronargefäßen durchgeführt. Zur Flussmessung eine segmentierte 2-D-Flash-Sequenz mit einer zeitlichen Auflösung von 110 bzw. 125 ms verwendet. Der mittlere Koronarfluss im Verhältnis zum aortalen Fluss war bei Patienten mit hochgradigen Koronarstenosen signifikant (p < 0,001) erniedrigt. Die MR-Phasenkontrastmethode ermöglicht eine genaue Bestimmung des Blutflusses in Koronargefässen und in Korrelation zum Aortenfluss eine Aussage über hochgradige Koronarstenosen. Weiterentwicklungen der Methode müssen eine Verbesserung der räumlichen und zeitlichen Auflösung zum Ziel haben.Abstract.Aim: The purpose of the study was to evaluate the accuracy of velocity encoded cine MR imaging for the determination of blood flow in patients with coronary artery stenoses. Flow measurements were performed in 18 coronary arteries in 15 patients. We used velocity-encoded k-space segmented gradient echo sequences with a temporal resolution of 110–125 ms. The mean coronary flow in correlation to aortic flow was significantly reduced in patients with severely stenosed arteries. Velocity-encoded MR imaging enables determination of flow in coronary arteries and in correlation of the aortic flow the detection of coronary artery stenoses. Future developments should aim at the improvement of spatial and temporal resolution of the method.