Rainer Rienmüller

The Emerging Role of Magnetic Resonance Imaging in the Diagnosis and Management of Pulmonary Hypertension

Pulmonary hypertension is a life-threatening chronic disorder of the pulmonary circulation. Elevated pressure and resistance in the pulmonary vessels lead to progressive right heart failure which results in functional limitations and ultimately the death of most patients. Thus, the monitoring of right ventricular (RV) function is of great importance. Cardiac magnetic resonance imaging (cardiac MRI) has several advantages over other imaging methods. The use of cine acquisition techniques allows precise description of characteristic volumetric and functional variables, such as right ventricular volumes, muscle mass, stroke volume, ejection fraction, or cardiac output. Impaired right ventricular contractility and function have also been assessed using measures like ventricular septal bowing and pressure-volume loops. MRI investigations have been performed to monitor medical treatment, and the improvement in well-established prognostic factors, such as the 6-min walk, were correlated with measures of right ventricular function. Flow-derived parameters of the pulmonary arteries (such as peak velocity, acceleration time and volume, or pulmonary flow profile) are available using velocity-encoded imaging, and may detect early signs of remodelling. Additionally, magnetic resonance angiography is a promising new tool to visualise pulmonary perfusion and to diagnose chronic thromboembolic pulmonary hypertension. The purpose of this review is to summarise recent advances of cardiovascular magnetic resonance imaging, which will play an increasing role in the comprehensive diagnostic work-up of patients with pulmonary hypertension as a tool to monitor the course of the disease and to evaluate new therapeutic approaches.

Intimal Sarcoma of the Pulmonary Valve

Pulmonary artery intimal sarcoma is a rare tumor of the cardiovascular system. Intimal sarcoma of the pulmonary valve itself has not been described. Embolization into pulmonary arteries originating from the pulmonary valve intimal sarcoma can mimic chronic thromboembolic pulmonary hypertension and mislead the diagnosis. We present and discuss a patient initially diagnosed as chronic thromboembolic pulmonary hypertension, treated by pulmonary endarterectomy. After 24 months, a tumor of the pulmonary valve was detected by echocardiography. The patient underwent removal and replacement of the pulmonary valve. Histology revealed pulmonary valve intimal sarcoma.

Quantitative Bestimmung der linksventrikulären Myokardperfusion mittels EBCT

ZusammenfassungDie myokardiale Perfusion stellt einen wesentlichen Parameter der funktionellen. Determinanten des Herzens dar. Die Bestimmung dieses Parameters mittels direkter Meßverfahren in vivo am Menschen ist nicht vertretbar. So kommen verschiedene indirekte Meßmethoden (Fremdgas-, Thermodilution-, Dopplerkatheter- und radioaktive Techniken) zum Ensatz. Seit der Entwicklung der Electron-Beam-computertomographischen Technologie ist es möglich geworden, nicht nur die linskventrikulären Volumina zu bestimmen, sondern auch die myokardiale Perfusion in ml/100 g/min zu berechnen. Die Messung der linksventrikulären Myokardperfusion erfolgt hierbei im sogenannten Multi-Slice-Flow-Mode in “short axis view”. Hierbei wird der Untersuchungstisch mit dem Patienten 25° nach rechts und 15° nach kaudal gekippt. Nach einem Lokalisationsscan zur Bestimmung der Lage des linken Ventrikels wird der Tisch mit dem Patienten so positioniert, daß sich die voraussichtliche Mitte des linken Ventrikels im Meßfeld der dritten und vierten CT-Schicht befindet. Nach intravenöser Kontrastmittelapplikation von 50 ml und einem Flow von 3 ml/s werden 13×6 CT-Schichten EKG-getriggert jeden zweiten oder dritten Herzschlag angefertigt. Auf der Befundkonsole werden die Regions of Interest so in das linksventrikuläre Myokard gelegt, daß ein Partialvolumeneffekt seitens der benachbarten Struktur möglichst gering gehalten wird. Dies erfolgt 13 mal in jeder CT-Schicht. Zusätzlich werden CT-Werte-Änderungen im Lumen des linken Ventrikels wiederum 13 mal bestimmt. Aus der maximalen Steigung der arteriellen myokardialen Zeit-CT-Werte-Kurve wird nach Division durch die Differenz des maximalen CT-Wertes und des Präkontrast-CT-Wertes im linken Ventrikel die myokardiale Perfusion in ml/100 g/min berechnet. Im Rahmen dieser Studie wurden zusätzlich die linksventrikulären Volumina, wie EDV, ESV, SV, bestimmt und daraus AF und HZV errechnet, und zwar aus CT-Aufnahmen des linken Ventrikels, angefertigt in “long axis view”. Bei neun untersuchten Patienten betrugen die gemessenen globalen myokardialen Perfusionswerte 70 ml/100 g/min (minimal 32 und maximal 116 ml/100 g/min). Dieser Mittelwert entspricht 5% des Herz-Zeit-Volumens unter der Annahme, daß das mittlere Herzgewicht dieser Patienten 300 g beträgt. Die mittels EBCT bestimmte linksventrikuläre Muskelmasse betrug in dieser Studie im Durchschnitt 130 g. Der Vergleich der koronarangiographischen Befunde dieser Patienten mit den gemessenen Perfusionswerten zeigte, daß es nicht ausreichend ist, nur die absolut gemessenen Perfusionswerte zu betrachten, sondern daß diese unter Berücksichtigung des jeweils gemessenen Herz-Zeit-Volumens beurteilt werden müssen. Weitere Studien genau definierter Patienten-gruppen sind erforderlich, um Perfusionsnormwerte unter Ruhebedingungen bei Patienten mit und ohne einer Koronargefäßerkrankung zu bestimmen, da vergleichende Auswertungen mit szintigraphischen Verfahren methodisch bedingt problematisch erscheinen. Die bisherigen Ergebnisse zeigen, daß es mittels EBCT trotz aufhärtungsbedingter Artefakte auch unter klinischen Bedingungen möglich ist, myokardiale Perfusionsmessungen durchzuführen. Ihre Interpretation muß jedoch vorläufig unter Berücksichtigung der funktionellen Parameter, einschließlich der Herzfrequenz, insbesondere jedoch unter Berücksichtigung des Herz-Zeit-Volumens erfolgen.SummaryMyocardial perfusion is one of the most important functional parameters of the heart. Presently various indirect methods are used to determine coronary blood flow or myocardial perfusion as inertgas-, thermodilution-, Doppler catheter- and radiopharmacological techniques.Electron-beam-computed-tomographical technology is able to perform CT data acquisition with a very short exposure time of 50 ms. Using this method it is not only possible to determine left ventricular volumes but also to measure myocardial perfusion in ml/100 g/min. The measurement of the left myocardial perfusion is performed using the short axis view. This position is obtained by moving the table 25 degrees to the patient’s right and 15 dégrees caudally. To determine the position of the left ventricle, a localization scan is obtained in multi-slice-mode using all for target-rings, thus obtaining 8 tomographic levels over 68 mm (each tomographic level having a slice thickness of 7 mm, with an interslice gap of 4 mm between each two adjacent tomographic levels). In this short axis position, using the multi slice flow mode with 3 target-rings and after administration of 50 ml of contrast medium intravenously with a flow of 3 ml/s, 6 tomographic levels are imaged Each tomographic level is obtained 13 times at 80% of the R-R-interval at each 2 or 3 heart beat (ECG-gated). The left ventricular myocardial contrast enhancement is measured by drawing manually the outline of the left ventricular myocardium using time-density-software of the Imatron workstation. For calculation of the myocardial perfusion the socalled “slope method” is used and the results are expressed as the maximum slope of enhancement of the myocardium divided by the difference of the precontrast and peak CT-value in the left ventricle. The global myocardial perfusion is calculated as a mean of all evaluated tomographic levels.In this study left ventricular volumes as enddiastolic volume endsystolic volume and stroke volume were measured and ejection fraction and cardiac output calculated. The measurements were performed in the long axis view. This view is obtained by moving the table 15 degrees to the patients left in a horizontal position. In this long axis position 6 tomographic levels are imaged using the multi-slice-cine-mode with 3 targetrings after administration of 50 ml of contrast medium intravenously with a flow of 3 ml/s. Each tomographic level is obtained 13 times starting at 0% of the R-R-interval (ECG-triggering). The exposure time is 50 ms with an interscan time delay of 8 ms. In 9 studied patients of whom one had 3 significant coronary artery stenotic, lesions (>50%), 2 patients had each 2 non significant stenotic lesions (<50%) and 6 revealed nearly normal coronary angiograms. The mean global myocardial perfusion was 70 ml/100 g/min (min. 32 and max. 116 ml/100 g/min). This mean value of 70 ml/100 g/min is reflecting 5% of the cardiac output supposing that the mean heart weight of these patients was 300 g. In this study the mean of the left ventricular muscle mass determined by the use of EBCT was 130 g. A comparative evaluation of coronary angiographic findings in these patients with the measured myocardial perfusion, values revealed, that it is not sufficient to look only at the absolute values of the measured myocardial perfusion. Furthermore it seems to be necessary to interprete these perfusion values with respect to the calculated cardiac output.Additional studies of well defined patients groups are necessary to determine normal values of myocardial perfusion at rest in patients with and without coronary artery disease. This seems to be important as comparative analysis of myocardial scintigraphic and EBCT-studies is difficult because of methodical inherent differences. The results of this study suggest that despite the presence of some beam hardening artifacts it is possible to measure myocardial perfusion using EBCT in patients with suspected coronary artery disease in the daily clinic workup. For the interpretation of these myocardial perfusion values it is necessary to pay special attention to heart rate and especially to the calculated cardiac output.

25 Years of Cardiac CT Imaging: Past, Present, and Future

Purpose: A brief summary of past, present, and future of cardiac CT is given. Past: As long as the CT exposure time was in a range between 1 and 5 s, it was only possible to image cardiac morphology. At that time, we have learned the diagnostic criteria of transverse cardiac imaging especially in the field of pericardial diseases. Diagnostic criteria of constrictive pericarditis were developed which were superior to all other imaging modalities as it became possible to image the complete cardiac structures and the organs of the chest simultaneously without overlap and without any anatomic or patient limitation and observer-independent. A new concept of approach and therapy of this disease was developed, and in those institutions where this method was applied, the mortality from pericardiectomy could be essentially reduced and the surgical outcome results improved. Present: The presence is characterized by an increase in functional imaging as there is a continuous reduction of the exposure time using the advanced multi-slice and multi-detector and electron-beam CT technology which is reflected by the integration of these methods in the daily evaluation of coronary heart disease. Coronary atherosclerosis, coronary arteries, functional parameters, and myocardial perfusion can be evaluated qualitatively and quantitatively. Future: Technically, in the future further shortening of the exposure time and the introduction of flat detectors for real-time volume imaging may be expected with changes of diagnostic and therapeutic algorithms.Ziel: Es soll eine kurze Zusammenfassung der Vergangenheit, Gegenwart und Zukunft der kardialen Computertomographie gegeben werden. Vergangenheit: Solange die CT-Technologie Expositionszeiten zwischen 1 und 5 s erlaubte, konnten nur morphologische Strukturen des Herzens abgebildet werden. Klinisch konzentrierte sich die Anwendung der kardialen CT auf die Evaluierung primär morphologisch begründeter Herzerkrankungen wie z.B. Erkrankungen des Perikards. Es wurden diagnostische Kriterien für den Nachweis bzw. Ausschluss konstriktiver perikardialer Erkrankungen mit einer Sensitivität und Spezifität von praktisch 100% entwickelt. An diesem Krankheitsbild konnten die Vorteile der überlagerungsfreien, schichtweisen, patienten- und untersucherunabhängigen Darstellung des Herzens und der benachbarten Strukturen überzeugend dargestellt werden. Verschiedene Formen perikardialer Konstriktion wurden definiert, die wiederum ihrerseits den operativen Zugang des Herzchirurgen und das Ausmaß der notwendigen Perikardfensterung bestimmten. Durch den präoperativen Nachweis bzw. Ausschluss myokardialer Atrophie und Fibrose ist es in denjenigen Zentren, die den CT-diagnostischen Zugang wählen, gelungen, die perioperative Mortalität entscheidend zu senken. Gegenwart: Die Gegenwart ist charakterisiert durch zunehmende funktionelle CT-Bildgebung, die auf einer Verkürzung der Expositionszeiten unter 1 s und der Einführung der Mehrschicht- und Multidetektor- sowie der Elektronenstrahl-CT basiert, verbunden mit zunehmender Integration in die tägliche Diagnostik der koronaren Herzkrankheit. Die Lokalisation und das Ausmaß koronarsklerotischer Veränderungen können qualitativ und quantitativ bestimmt werden, die proximalen subepikardialen Koronargefäße und die linksventrikulären Funktionsparameter mit einer der Koronarangio- und Ventrikulographie vergleichbaren Genauigkeit evaluiert werden, und die Myokardperfusion kann quantitativ global und regional angegeben werden. Zukunft: Technischerseits sind in der Zukunft eine weitere Verkürzung der Expositionszeiten sowie die Implementierung von Flachdetektorsystemen für Real-Time-Volumenimaging zu erwarten, wodurch ein wesentlicher Wechsel im Bereich der diagnostischen und therapeutischen Algorithmen der koronaren Herzkrankheit stattfinden wird.

Application of pharmacokinetics to electron-beam tomography of the abdomen

RATIONALE AND OBJECTIVES The purpose of this study was to evaluate the pharmacokinetics of abdominal time-attenuation curves obtained at electron-beam tomography. MATERIALS AND METHODS Computed tomographic enhancement data of the aorta, portal vein, vena cava, liver, spleen, and pancreas were obtained in 25 patients after injection of 50 mL of contrast medium. These data were used to calculate pharmacokinetic parameters such as half-lives, mean residence times, and areas under the curve with a computer program. RESULTS Maximal enhancement was observed in the aorta 24 seconds +/- 5 (mean +/- standard deviation) after starting the injection of contrast medium (178 HU +/- 56), in the portal vein after 42 seconds +/- 14 (60 HU +/- 17), in the vena cava after 35 seconds +/- 7 (66 HU +/- 23), in the liver after 58 seconds +/- 15 (24 HU +/- 6), in the spleen after 35 seconds +/- 12 (42 HU +/- 16), and in the pancreas after 39 seconds +/- 15 (42 HU +/- 10). Half-lives of the last phase observed were 108 seconds +/- 123 in the aorta, 33 seconds +/- 30 in the portal vein, 49 seconds +/- 40 in the vena cava, 50 seconds +/- 54 in the liver, 62 seconds +/- 33 in the spleen, and 22 seconds +/- 27 in the pancreas. The computer program allowed for excellent fitting curves to the measured attenuation values and for subsequent calculation of pharmacokinetic parameters. New dosage regimens also could be simulated successfully. CONCLUSION The pharmacokinetic parameters evaluated might be useful in the optimization of dosing and scanning parameters of the abdomen for ultrafast and helical CT.

Liver Cirrhosis Cured by Pericardiectomy-A Rare Case of Constrictive, Non-Calcifying Pericarditis

Constrictive pericarditis usually leads to heart failure but can also cause extra cardiacdiseases. We report a patient who presented with dyspnea, recurrent pericardial and pleural effusions as well as ascites. An initial cardiologic examination revealed a pericardial effusion without severe hemodynamic impairment, but without signs of additional pathologies. Abdominal sonography showed liver cirrhosis, which was laboratory classified as Child grade B. The patient was referred to a transplantation center for liver transplant evaluation. During the liver transplant evaluation process, Cardiac Magnetic Resonance Imaging (MRI) and Computed Tomography (CT) finally revealed a constrictive non-calcifying pericarditis as the origin of the cardiac cirrhosis and the patient was scheduled for periand partial epicardiectomy. Two years later, clinical and biochemical liver parameters were completely restored. There was no recurrence of ascites or pleural effusions. At follow-up, cardiac CT and MRI proved the absence of a pericardial constriction while liver sonography showed normal hepatic morphology. This case presents a highly rare cause for liver cirrhosis and underlines the importance of a complete cardiac evaluation in case of a present liver cirrhosis of unknown causes.

A multiple regression analysis of determinants of myocardial perfusion as measured by CT

Purpose: To gather opinions of radiographers regarding the use of humour among students and professionals, and to apprehend possible positive and/or negative impacts of its use on the care relationship. Methods: Sample. Six hundred forty-one senior radiographers and 411 first, second or third year undergraduate radiographers, for a total sample of 1052 subjects from all over France. Material. Within a quantitative phase, both professionals radiographers and radiographers-in-training were assessed on several Likert-type scales involving concepts such as the functions of humour, and a second, qualitative phase based on open survey questions further focused on investigating the most salient concepts, notably within the senior radiographer sample. Results: Although radiographer apprentices saw the major benefits of humour in their relationships with patients (i.e. building a trust relationship, distraction technique), the senior radiographers put forward benefits especially regarding their colleagues or their own person (pleasant working environment, coping strategy during stressful events). Positive aspects of humour do prevail over the negative ones in both radiographer groups, but professionals emphasize the contextualized aspects of humour and warn that it may infringe on patients and their dignity. Conclusion: Considering humour as a personal and a professional value among the samples studied opens new perspectives on use of humour and its training within both institutional and educational contexts, preventing any possible harmful use.

Contents Vol. 76, 2008

I. Adcock, London H.D. Becker, Heidelberg D. Bouros, Athens N.S. Cherniack, Newark, N.J. K.F. Chung, London V. Cottin, Lyon C. Dooms, Leuven S. Gasparini, Ancona P.M. Gustafsson, Göteborg J. Hammer, Basel C. Kroegel, Jena F. Kummer, Vienna P.N. Mathur, Indianapolis, Ind. L.P. Nicod, Lausanne T. Nishino, Chiba M. Noppen, Brussels D. Olivieri, Parma C.P. Page, London E.W. Russi, Zürich J. Vansteenkiste, Leuven Editorial Board

Flow-related magnetic resonance; visualization of a re-coarctation

Fig. 1. The preoperative MR image modified by the method described by Machler et al. (Eur J Cardiothoracic Surg 2007;32:102—7 and 2004;26:747—53) showed high velocity jets (red) within the stenosis as well as towards the lateral wall of the aneurysmatic sac. This lead to the conclusion that the risk of rupture might not be determined by the increased diameter of the aneurysmatic sac itself but mainly by the jet and consecutive increased wall tension of the lateral wall. With the use of conventional radiological imaging alone this significant flow-related fact would have been ignored. Fig. 2. (a) (Top) The preoperative MR image without the visualized flow pattern. (b) (Bottom) The postoperative CT scan mimics two aortic arches: the extra-anatomical conduit lateral to the native aortic arch. * Corresponding author. Tel.: +43 316 385 4671; fax: +43 316 385 4672. E-mail address: Heinrich.maechler@meduni-graz.at (H. Machler).

Non-invasive approach to coronary heart disease

Based on more than 2000 cardiac EBT studies using the above mentioned protocol it is possible like in an “One-Stop-Shop” to assess the extent of coronary atherosclerosis as Coronary Calcium Score (first part of the definition of coronary heart disease) to evaluate the degree, location and number of stenotic lesions in the proximal 5–6cm of the coronary arteries , to determine the severity of coronary heart disease by measuring the global and regional myocardial blood flow ( second part of the definition of coronary heart disease ) and to measure the functional left ventricular parameters giving the information if they are still in normal range or changed either as a sequel of the coronary heart disease or as a compensatory mechanism to keep myocardial blood flow as adequate as possible with respect to the balance of oxygen supply and demand.