Suppressing apoptosis with milrinone simulating extracorporeal circulation: a pilot study.

BACKGROUND: After cardioplegia, ischemia/reperfusion injury can induce apoptosis. The aim of this study was to evaluate our ex vivo microperfusion model on human myocardium during simulated cardioplegia (cp) and reperfusion (rep). In addition, the aim was to verify the anti-apoptotic properties of the phosphodiesterase 3 inhibitor milrinone. METHODS: Cardiac biopsies were retrieved from the right auricle of patients undergoing elective CABG prior to induction of cardiopulmonary bypass. Biopsies were exposed to ex vivo conditions with varying periods of cp/rep (30/10, 60/20, 120/40 min). Group I consisted of untreated controls (n=15), Group II of treated controls who had cp/rep (n=15) while Group III had cp/rep+milrinone (n=15). For the detection of apoptosis, anti-activated caspase-3 and PARP-1 cleavage immunostaining were used. RESULTS: The percentage of apoptotic cardiomyocytes in Group I was significantly (P<0.05) lower compared to Group II, revealing a time-dependent increase. In Group III with milrinone treatment, apoptosis was significantly suppressed (P<0.05). CONCLUSIONS: Milrinone significantly suppressed apoptosis in our ex vivo setting. This finding warrants further study aiming to evaluate the potential beneficial effects of milrinone on the suppression of ischemia/reperfusion injury in a clinical setting.

Endovascular repair of infrarenal abdominal aortic aneurysm associated with a horseshoe kidney and graft thrombosis in early follow-up.

Endovascular aneurysm repair (EVAR) is a well-established alternative to open surgery. The presented case underwent endovascular therapy of an abdominal aortic aneurysm (AAA) with the anatomical prerequisite of a horseshoe kidney. We describe the technique used, including the embolization of aortic side branches, to avoid endoleaks, and the management of thrombotic complications during follow-up.

Sixty-four-MSCT in the characterization of porcine acute and subacute myocardial infarction: determination of transmurality in comparison to magnetic resonance imaging and histopathology.

OBJECTIVE: The aim of this study was to assess the accuracy of MSCT in characterizing myocardial infarction (MI) and, thereby, determine the extent of early perfusion defect (ED), microvascular obstruction (MO) and transmural depth of late enhancement (LE) in comparison to MRI and histology. MATERIALS AND METHODS: Seven pigs were studied with MSCT (Somatom Sensation 64) and MRI (Magnetom Sonata) a median 1 and 21 days following temporary occlusion of a diagonal branch and creation of small reperfused infarction. For depiction of ED, CT images were acquired in the early arterial phase and following 35 s; LE and MO were evaluated on images obtained at 3, 5, 10 and 15 min. Thereby, a bolus/low-flow contrast injection protocol was used. Triphenyltetrazolium-chloride (TTC) stain and histology were obtained. Volumes of enhancement patterns were assessed as percentage of the ventricle and compared by Bland-Altman analysis. Segmental co-localization and graded transmurality was evaluated with weighted-kappa-test. RESULTS: Close spatial agreement was observed for MRI-MO and MSCT-MO (bias=0.55; CI=-1.49 to 2.60 at 5 min MSCT), TTC and MSCT-LE (bias=-1.28; CI=-3.76 to 1.19) or MRI-LE and MSCT-LE (bias=-0.79; CI=-4.19 to 2.60). There was good segmental co-localization for MO (weighted kappa=0.93) and high agreement for transmural extent of TTC, MRI-LE and MSCT-LE (weighted kappa=0.84 TTC versus MSCT; 0.86 MRI versus MSCT). Arterial and 35s ED significantly underestimated infarct size and showed poor segmental or transmural agreement (weighted kappa=0.33; 0.44). CONCLUSIONS: MSCT late-scans not only reliably depict size of MO and LE in acute or subacute infarct phases but, moreover, allow for accurate determination of LE transmurality.

Aptamer-based isolation and subsequent imaging of mesenchymal stem cells in ischemic myocard by magnetic resonance imaging.

PURPOSE: Mesenchymal stem cells (MSC) seem to be a promising cell source for cellular cardiomyoplasty. We recently developed a new aptamer-based specific selection of MSC to provide "ready to transplant" cells directly after isolation. We evaluated MRI tracking of newly isolated and freshly transplanted MSC in the heart using one short ex vivo selection step combining specific aptamer-based isolation and labeling of the cells. MATERIALS AND METHODS: Bone marrow (BM) was collected from healthy pigs. The animals were euthanized and the heart was placed in a perfusion model. During cold ischemia, immunomagnetic isolation of MSC from the BM by MSC-specific aptamers labeled with Dynabeads was performed within 2 h. For histological identification the cells were additionally stained with PKH26. Approx. 3 x 10(6) of the freshly aptamer-isolated cells were injected into the ramus interventricularis anterior (RIVA) and 5 x 10(5) cells were injected directly into myocardial tissue after damaging the respective area by freezing (cryo-scar). 3 x 10(6) of the aptamer-isolated cells were kept for further characterization (FACS and differentiation assays). 20 h after cell transplantation, MRI of the heart using a clinical 3.0 Tesla whole body scanner (Magnetom Trio, Siemens, Germany) was performed followed by histological examinations. RESULTS: The average yield of sorted cells from 120 ml BM was 7 x 10(6) cells. The cells were cultured and showed MSC-like properties. MRI showed reproducible artifacts within the RIVA-perfusion area and the cryo-scar with surprisingly excellent quality. The histological examination of the biopsies showed PKH26-positive cells within the areas which were positive in the MRI in contrast to the control biopsies. CONCLUSION: Immunomagnetic separation of MSC by specific aptamers linked to magnetic particles is feasible, effective and combines a specific separation and labeling technique to a "one stop shop" strategy.

Perioperative monitoring of flow and patency in native and grafted internal mammary arteries using a combined MR protocol.

The objective of this study was to evaluate graft flow (f) and patency (p) in patients with internal mammary artery (f,p) and venous (p only) grafts using a combined MR protocol with phase-contrast technique and MR angiography. 42 patients with 42 left internal mammary artery (LIMA) and 63 venous grafts were examined pre and 6 months post coronary artery bypass graft (CABG) surgery. Phase-contrast flow measurements were applied to the IMA. Post-operatively, a contrast enhanced MR angiogram was performed to assess bypass patency. LIMA/venous grafts were occluded in 3/42 and 13/63, respectively. Flow in LIMA decreased from 19.4+/-10.4 ml min(-1) m(-2) pre-operatively to 13.4+/-9.7 ml min(-1) m(-2) post-operatively (p<0.002). In contrast, flow in the native right IMA increased from 17.6+/-8.7 ml min(-1) m(-2) pre-operatively to 24.8+/-9.0 ml min(-1) m(-2) post-operatively (p<0.001). MRI allows a combined assessment of bypass patency and flow. This study protocol may be applicable to perioperative follow-up studies in patients after CABG surgery.

[MR angiography and determination of the flow reserve after minimal invasive direct coronary artery bypass (MIDCAB) surgery of the left internal mammary artery in comparison to multirow CT]. / MR-Angiographie und Flussreservenbestimmung nach minimalinvasiver direkter Koronararterien-Bypass(MIDCAB)-Operation der linken Arteria mammaria interna im Vergleich zur Mehrzeilen-CT.

PURPOSE: To evaluate graft patency, flow and flow reserve in patients with minimal invasive direct coronary artery bypass (MIDCAB) of internal mammary artery (IMA) grafts using a combined MR protocol with phase-contrast technique and MR angiography. MATERIAL AND METHODS: At a 1.5T Magnetom Sonata (SIEMENS), 19 symptomatic (angina CCS I-III, intermittent thoracic discomfort, scar disorders) patients (59.9 +/- 7.9 years old) with 19 left internal mammary artery (LIMA) grafts implanted in minimal invasive technique were examined 6.9 +/- 1.5 years post surgery. Contrast enhanced MR angiography (TR 2.5 ms, TE 1 ms, flip angle 20 (o), spatial resolution 1.4 x 0.9 x 1.0 mm(3), breath hold technique, no ECG-triggering, 25 ml Gd-DTPA) was performed to assess bypass patency. Phase-contrast flow measurements with retrospective gating (TR 41 msec, TE 3.2 msec, flip angle 30 degrees , spatial resolution 1.1 x 1.1 x 5 mm(3), temporal resolution 42 msec, venc 90 cm/sec) were applied in the IMA grafts at rest and after stress induction with dipyridamole (0.56 mg/kg/BW). For comparison, graft patency was evaluated by multidetector-row computed tomography (16-row CT). In 9 patients a selective catheter angiography was performed. RESULTS: MIDCAB grafts were occluded in 4/19 patients. In 4 patients the anastomosis to LAD was highly stenotic (> 70 %) at MDCT (2 experienced investigators in consensus reading). In MRA 9 grafts could be delineated completely including the distal anastomosis to LAD (47 %). In 9 patients the distal part could not be evaluated. In patients with patent grafts (MDCT), a significant improvement of graft flow (at rest 75.4 +/- 33.3 ml/min; after stress 202.7 +/- 49.6; P < 0.002) and flow reserve (patent grafts 3.0 +/- 1.1; stenotic grafts 1.5 +/- 0.2, P < 0.02; occluded grafts 0.9 +/- 0.2, P < 0.01) after stress induction was detected. Diastolic-to-systolic peak velocity ratios (D/S-PVR) at baseline were not significant between patent and stenotic grafts. Mean flow at baseline and after stress induction and flow reserve show a high sensitivity (91/92 /83 %) and specificity (86 /100/83 %) for detection of graft stenosis. MR angiography combined with flow reserve measurements could distinguish between occluded/stenotic and patent grafts in all MIDCAB grafts. CONCLUSION: MR imaging allows combined assessment of bypass patency and flow with flow reserve in patients after MIDCAB. The protocol of this study is applicable for the evaluation of graft patency in patients after revascularization.

Aprotinin in fibrin tissue adhesives induces specific antibody response and increases antibody response of high-dose intravenous application.

BACKGROUND: In cardiac operations, aprotinin therapy is used either locally as a component of commercially available fibrin tissue adhesives, intravenously, or combined. Our aim was to examine the formation of aprotinin-specific antibodies with regard to the application mode. METHODS: Sera of 150 patients who had undergone cardiac operations and were receiving aprotinin therapy for the first time were sampled before the operation and at medians of 3.5 and 13.3 months after the operation. Aprotinin-specific IgG including all subgroups and aprotinin-specific IgE were analyzed. Aprotinin was given locally (as contained in fibrin sealant; n = 45; median dose, 6000 KIU), intravenously (n = 46; 2.000 x 10(6) KIU), and combined (n = 59; 2.012 x 10(6) KIU). RESULTS: At 3.5 months, the prevalence of aprotinin-specific IgG antibodies was 33% (15/45 patients) after local, 28% (13/46 patients) after intravenous, and 69% (41/59 patients) after combined exposure (P =.0001). At 13.3 months, the prevalence of aprotinin-specific IgG antibodies was 10% (4/41 patients) after local, 31% (13/42 patients) after intravenous, and 49% (28/57 patients) after combined exposure. Total aprotinin dose was similar in patients who were antibody positive and negative. Before the operation, no aprotinin-specific antibodies were detected. Aprotinin-specific IgE were not found after the operation. CONCLUSION: Local aprotinin contact induces a specific immune response and reinforces that of intravenous exposure. The antibody spectrum is identical to the immune response induced by intravenous exposure. Any exposure should be documented. For use in cardiac operations as a hemostyptic, the necessity itself and alternatives for aprotinin as a stabilizing agent merit consideration.

Fibrin sealant, aprotinin, and immune response in children undergoing operations for congenital heart disease.

OBJECTIVE: Most commercially available fibrin sealants contain aprotinin in doses of 1500 kallikrein inactivator units per milliliter. They are used in many operative disciplines. An elevated risk of hypersensitivity reactions exists at reexposure to aprotinin. Our aim was to examine the immunogenic potency of aprotinin as a fibrin sealant content. METHODS: We investigated 49 children with operatively treated congenital heart disease. All patients received aprotinin only topically as contained in fibrin sealant. Serum samples were drawn preoperatively, 1 week, 2 weeks, 6 weeks, and approximately 1 year after operation. They were analyzed for aprotinin-specific immunoglobulin G antibodies with a standard enzyme-linked immunosorbent assay and a fluorescence enzyme immunoassay for aprotinin-specific immunoglobulin E antibodies. RESULTS: At 1 week, 2 weeks, 6 weeks, and 1 year, we found prevalences of 8% (2 of 26), 8% (2 of 24), 6% (3 of 49), and 0% for aprotinin-specific Immunoglobulin E, and for aprotinin-specific immunoglobulin G 8% (2 of 26), 17% (4 of 24), 39% (19 of 49), and 12% (5 of 41). The doses of aprotinin given did not differ significantly in antibody-negative and antibody-positive patients; no significant factors could predict the immune response. CONCLUSIONS: Our findings show the existence of a subgroup of patients who had aprotinin-specific antibodies develop after topical aprotinin application. Any use of aprotinin must be carefully documented. If aprotinin use is planned in patients who previously underwent a surgical procedure, preexposure to aprotinin in any form must be sought to avoid unexpected anaphylactic reactions. The necessity itself and alternatives for aprotinin as a stabilizing agent in fibrin sealants merit consideration.

Long-term results after early primary repair of tetralogy of Fallot.

OBJECTIVE: Early primary repair of tetralogy of Fallot has been routinely performed at Children's Hospital, Boston, since 1972. We evaluated the long-term outcome of this treatment strategy including the influence of a transannular patch. METHODS: Fifty-seven patients less than 24 months of age (median 8 months) underwent primary repair of tetralogy of Fallot between January 1972 and December 1977. Thirty-one patients had a transannular patch. Survival and freedom from reintervention were determined by the Kaplan-Meier method with 95% confidence intervals. RESULTS: There were 8 early deaths, and 1 patient died 24 years after initial repair. Recent follow-up was obtained for 45 of the 49 long-term survivors (92%). Median follow-up was 23.5 years. Ten patients underwent reintervention, 8 of whom underwent relief of right ventricular outflow tract obstruction. Right ventricular outflow tract obstruction occurred in 6 patients without a transannular patch and 2 with a transannular patch (33% vs 6%, P =.04). One pulmonary valve replacement was performed at another institution 20 years after the repair. Forty-one long-term survivors were in New York Heart Association class I and 4 were in class II. Actuarial survival was 86% at 20 years (95% confidence intervals = 80%-92%). Freedom from reintervention was 93% at 5 years (95% confidence intervals = 87%-99%) and 79% at 20 years (95% confidence intervals = 70%-86%). No significant differences were found between patients with and without a transannular patch (survival, P =.34; freedom from reintervention, P =.09, log-rank tests). CONCLUSIONS: Long-term survival is excellent and the freedom from reintervention is satisfactory after early primary repair of tetralogy of Fallot in the 1970s. Use of a transannular patch does not reduce late survival and is associated with a lower incidence of right ventricular outflow tract obstruction.

Anaphylactic shock after aprotinin reexposure: time course of aprotinin-specific antibodies.

We report a case of severe anaphylactic shock during a cardiac operation that occurred as a consequence of aprotinin readministration in the presence of preformed aprotinin-specific antibodies. Both immunoglobulin G (3 hours) and immunoglobulin E (5 minutes) antibody levels dropped early after the clinical event. Despite their possibly limited clinical significance, we still recommend the conductance of specific antibody screening tests before readministration of aprotinin.

Surgical management of persistent mediastinitis after coronary bypass grafting.

Persistent mediastinitis despite primary revision, closed irrigation therapy, and additional secondary omental plasty is a life threatening situation in cardiac surgery. We managed this rare complication in one instance by sternectomy and hemirectus plasty as well as bilateral pectoralis plasty.

Conventional high resolution versus fast T(2)-weighted MR imaging of the heart: assessment of reperfusion induced myocardial injury in an animal model.

Cardiac image quality in terms of spatial resolution and signal contrast was assessed for conventional and newly developed T(2)-weighted fast spin-echo imaging with high k-space segmentation. The capability in revealing regional myocardial edema and cellular damage was examined by a porcine model using histopathologic correlation. Twelve porcine hearts were excised from slaughtered animals and instantly perfused with 1000 mL cold cardioplegic solution. After 4 h of cold ischemia the hearts were reperfused for one hour using a "Langendorff" perfusion model followed by MR imaging at 1.5 Tesla. Three additional pig hearts served as controls and were studied by MR directly after harvesting. Histopathological analysis of regional tissue changes was performed macro- and microscopically. Short axis T(2)-weighted (3000/45 and 90) high quality fast spin-echo (FSE) images were recorded without cardiac action and signal intensity was correlated with histology. These images also served as gold standard for evaluation of newly developed faster sequences allowing measuring times shorter than 20 s. Fast T(2)-weighted imaging comprised single-slice fast spin echo (moderate echo train length of 23 echoes, FSE(m)), and multi-slice single-shot half-Fourier fast spin-echo (71 echoes, FSE(HASTE)) sequences, supplemented by versions with inversion recovery preparation (FSE(m)IR and FSE(HASTE)IR). Systolic function after reperfusion was restored in 10 porcine hearts. Tissue alterations included myocardial edema and contraction band necrosis which was found to be most severe in myocardium with maximum T(2) SI. Especially FSE(m) and FSE(m)IR sequences allowed differentiation of all categories of tissue damage on a high level of significance. In contrast, single-shot FSE(HASTE) and FSE(HASTE)IR sequences did not provide sufficient image quality to discriminate moderate and severe myocardial damage (p > 0.05). Different degrees of myocardial injury after ischemia and reperfusion can be staged by MR imaging, especially using conventional high resolution T(2)-weighted FSE sequences. The animal study indicates that fast T(2)-weighted FSE(m) and FSE(m)IR sequences lead to superior image quality and diagnostic accuracy compared to FSE(HASTE) and FSE(HASTE)IR imaging.

Postischemic synthesis of high energy phosphates in isolated porcine hearts during reperfusion with 11 or 25 degrees C hypothermic perfluorocarbon emulsion FC 43. A 31P magnetic resonance spectroscopy study.

OBJECTIVE: One aim of coronary reperfusion after myocardial ischemia is to restore the myocardial content of high energy phosphates. The superiority of the artificial oxygen carrier perfluorocarbon emulsion FC43 over blood solution is known, therefore, in this paper we examined the temperature-dependence of this substance. METHOD: The changes of the high energy phosphates phosphocreatine (PCr) and inorganic phosphate (Pi) were documented in 29 isolated pig hearts, employing a 4.7 Tesla magnetic-resonance-spectroscope (MRS). After 15 min warm ischemia, reperfusion with warm blood and a cardioplegic ischemia period of 45 min, these hearts were reperfused with either 11 or 25 degrees C hypothermic oxygenated perfluorocarbon emulsion FC43, both under continuous spectroscopy. MRS is able to directly measure PCr as well as Pi. Their relation expresses the state of myocardial energy stores. RESULTS: Reperfusion with 11 degrees C hypothermic FC43 (n = 14) caused an increase of the relation PCr to Pi by a factor of 9, compared to an increase by a factor of 4 with 25 degrees C emulsion (n = 15) (P < 0.05). During 80 min of reperfusion with 11 degrees C cold FC43 emulsion the average flow rate was 90 +/- 12 and 96 +/- 11 ml/min during reperfusion with 25 degrees C hypothermic FC43 emulsion. Both rates fell only slightly in the course of time. CONCLUSION: We conclude that reperfusion with 11 degrees C hypothermic oxygenated FC43 in isolated ischemic porcine hearts leads to a clear increase of the index PCr/Pi compared with reperfusion at 25 degrees C. The correlation between the synthesis of myocardial high energy phosphates with postcardioplegic ventricular function is questionable. If further studies will show an improvement of myocardial function after perfusion with hypothermic oxygenated perfluorocarbon emulsion FC43, this solution may find clinical application in the storage of explanted human hearts for transplantation, during transportation to the recipient.

Transmyocardial laser revascularization in the acute ischaemic heart: no improvement of acute myocardial perfusion or prevention of myocardial infarction.

OBJECTIVE: Transmyocardial laser revascularization (TMLR) has been used to provide enhanced myocardial perfusion in patients not suitable for coronary revascularization or angioplasty. This study investigates the acute changes in myocardial perfusion after TMLR with a Holmium:Yttrium-Aluminium-Garnet (YAG) laser with a thermal imaging camera in a model of acute ischaemia, and confirms its midterm effects by post-mortem investigation of magnetic resonance imaging and histopathological examination. METHODS: Acute myocardial ischaemia was induced by occlusion of the dominant diagonal branch in ten sheep. Perfusion measurements were undertaken first in the unaffected myocardium, then after temporary occlusion of the coronary to obtain a control measurement for ischaemic myocardium. Myocardial perfusion was then evaluated during reperfusion after release of coronary occlusion. Then the coronary was permanently occluded and 20.5+/-2 channels were drilled with the Holmium:YAG laser and perfusion was measured again. The other four sheep served as control with untreated ischaemia. All animals were sacrificed after 28 days following administration of gadolinium i.v. to serve as contrast medium for magnetic resonance tomography. The hearts were subjected to magnetic resonance tomography and histopathological examination. RESULTS: Intraoperative perfusion measurements revealed a decreased perfusion after temporary occlusion and an increased perfusion in reperfused myocardium. After TMLR, no improvement of myocardial perfusion above the ischaemic level could be shown. Magnetic resonance images could neither confirm patent laser channels nor viable myocardium within ischaemic areas. On histology no patent endocardial laser channel could be detected. The transmural features were myocardial infarct with scar tissue. CONCLUSIONS: In the presented sheep model with acute ischaemia, TMLR with a Holmium:YAG laser did not provide acute improvement of myocardial perfusion as assessed by a thermal imaging camera. This would suggest no direct contribution of newly created laser channels to myocardial perfusion. As chronic effects are concerned, no perfused laser channels could be identified by later magnetic resonance imaging or histology.

MRI diagnosis of a previously undiagnosed large trabecular ventricular septal defect in an adult after multiple catheterizations and angiocardiograms.

Ventricular septal defect (VSD) is the most frequent congenital heart disease (25-30%). The diagnosis of VSD is usually made echocardiographically by means of colour Doppler ultrasound, and is confirmed by angiocardiography in most cases. We describe a case in which an additional large trabecular VSD was demonstrated by MRI after previous cardiac catheterizations and angiocardiography in various hospitals. MRI allows an exact presentation of the anatomy, including areas that are difficult to assess, for instance the apical septum. Determination of cardiac output, regurgitation volume and the Qp/Qs quotient in patients with shunt volume in heart defects is also possible with one examination.

[The MR signal behavior of a 4-week-old occlusive myocardial infarct in an animal experiment]. / MR-Signalverhalten des 4 Wochen alten okklusiven Myokardinfarktes im Tierexperiment.

PURPOSE: To correlate signal behaviour in T1- and T2-weighted images after Gd-DTPA with regional histopathology in occlusive myocardial infarction (MI). METHODS: Ligation of a diagonal branch of the LAD was performed in seven sheep. Four weeks later 0.1 mmol Gd-DTPA/kg were injected in five sheep 15 min before cardiac arrest and the sheep were slaughtered. In vitro imaging was performed at 1.5 T included T1- and T2-weighted spin echo sequences in long and short axis views. Signal intensities (SI) were determined in 36 myocardial segments per slice and compared to macro- and microscopy. RESULTS: In all animals an antero-lateral infarct region was evident histologically. This region presented with increased T2 SI and T1 SI after Gd-DTPA. The number of segments with increased SI in T1-weighted images was higher (n = 195 segments) compared to segments with increased T2 SI (n = 122 segments). Granulation tissue could be differentiated from rarely vascularized connective tissue at a high level of significance (p < 0.001) by T1 and T2 SI analysis. Wall thickness was significantly decreased in necrotic myocardium (3.8 +/- 1.2 mm) compared to normal tissue (9.8 +/- 1.1 mm, p < 0.001). CONCLUSION: In four-week-old occlusive MI the extent of necrosis can be accurately assessed by analysis of post contrast T1-weighted images. Considering regional T2 SI, granulation tissue can be differentiated from regions with predominant fibrous organisation.

[Cardiac MRI for determining functional left ventricular parameters]. / Kardio-MR zur Bestimmung linksventrikulärer Funktionsparameter.

PURPOSE: To prove the accuracy of MR methods in the determination of left ventricular (LV) functional parameters and anatomy. MATERIALS AND METHODS: At 1.5 T, 20 healthy volunteers and 22 patients with aortic valvular disease (stenosis n = 15, regurgitation n = 7) were examined. Functional parameters like cardiac output, ejection fraction, end-diastolic volume, aortic flow maximum, and time interval from the R-wave to maximum flow were obtained using a velocity encoding 2D FLASH sequence (TR 24 ms, TE 5 ms, venc 250 cm/sec) and segmented breath-hold cine FLASH 2D technique (TR 100 ms, TE 4.8 ms, flip angle 25 degrees, temporal resolution 50 ms). Invasive measurements (Fick principle) served as gold standard, intra- and interobserver variability were determined. RESULTS: Differences of functional parameters between normal volunteers and patients were detectable at a high level of significance (p < 0.0001). For cardiac output a superior correlation with the gold standard was found using flow measurements (r = 0.66, p < 0.0007) compared to volumetric calculations from cine studies (r = 0.47, p < 0.02). Interobserver variability was 2.5 +/- 2.7%/4.5 +/- 6.9% (flow quantification/calculations from cine studies), intraobserver variability was 1.7 +/- 1.6%/3.3 +/- 2.2%. CONCLUSIONS: MRI is an appropriate tool for determining LV functional parameters and anatomy. Differences between normal volunteers and patients with aortic valvular disease can be detected reliably. Flow measurements turned out to be more accurate than calculations from cine images. Therefore, flow quantification techniques should be preferred for clinical use.

[Diagnosis of renal artery stenosis in 1.0 T using 3D phase contrast magnetic resonance angiography and dynamic contrast medium perfusion]. / Diagnostik von Nierenarterienstenosen bei 1.0 T mittels 3D-Phasenkontrast-MR-Angiographie und dynamischer Kontrastmittelanflutung.

PURPOSE: To assess renal artery stenosis (RAS) by 3D phase contrast (PC) MR angiography and dynamic perfusion imaging of the kidneys. METHODS: On a standard 1.0 T MR imaging system (Magnetom Expert, Siemens), 32 patients with angiographically proven unilateral RAS were examined using a 3D PC sequence (TR 40 ms/TE 9 ms/venc 30 cm/s). An ECG-gated Turbo-FLASH 2D sequence (TR 4.5 ms/TE 2.2 ms/TIeff. 400 ms) was applied to study the first pass of paramagnetic contrast agent (0.1 mmol Gd-DTPA/kg) through the kidneys. Signal intensity (SI) over time curves of the renal cortex were obtained and evaluated considering temporal relation and percentage of maximum SI compared to the aorta and normal kidneys. Analysis of the MRA was performed by two independent blinded readers. The gold-standard DSA was interpreted by consensus reading of two experienced radiologists. RESULTS: RAS was detected by 3D PC MRA with a sensitivity of 93% and specificity of 81% (ppv 82%, npv 93%, accuracy 87%, kappa = 0.61). Maximum SI in RAS was significantly decreased (p < 0.001-0.0001). A temporally delayed enhancement of 1.5 +/- 1.3 s was found for RAS > 75% (p < 0.002) but not for RAS < 75% (p > 0.1). CONCLUSIONS: 3D PC MRA is capable of detecting RAS in a high percentage of patients. Dynamic perfusion imaging of the kidneys, applied additionally, can confirm the diagnosis and give valuable information about the hemodynamic relevance of RAS in suspected unilateral disease.

[2D-phase contrast flow evaluation and contrast-enhanced MR angiography for perioperative assessment of internal mammary artery grafts]. / 2D-Phasenkontrast-Flussquantifizierung und kontrastangehobene 3D-MR-Angiographie zur perioperativen Untersuchung des Arteria-mammaria-interna-Bypasses.

PURPOSE: To evaluate LV functional parameters, graft flow and patency in patients with IMA grafts using a combined MR protocol with phase-contrast technique and contrast enhanced MR angiography. MATERIAL AND METHODS: Using a 1.5 T MR system 27 patients with 27 left internal mammary artery (LIMA) and 41 venous grafts were examined before and 6 months after CABG surgery. A T(1)w-TSE sequence (slice thickness 5 mm) was applied for morphological imaging. LV function (EF, CO) was evaluated on cine images (segmented FLASH 2D, TR(eff) 11 ms, TE 4.8 ms, flip angle 25 degrees ). A phase-contrast FLASH 2D (TR 24 ms, TE 5 ms, flip angle 20 degrees ) sequence was applied for aortic and IMA flow measurements. Postoperatively, a contrast enhanced FLASH 3D MR angiography (TR 3.8 ms, TE 1.4 ms, flip angle 30 degrees ) with 25 ml Gd-DTPA was performed to assess bypass patency. RESULTS: In patients with reduced LV function (ejection fraction < 50 %) an improvement of the ejection fraction from 38.4 +/- 10.3 % to 49.8 +/- 15.3 % (p < 0.05) was found postoperatively. LIMA grafts were occluded in 1/27 patients, while 6/41 venous grafts were occluded. Distal LIMA anastomoses were demonstrated in 33 % by MRA. Flow of LIMA decreased from 21.2 +/- 11 ml/min/m(2) preoperatively to 14.4 +/- 9.6 ml/min/m(2) postoperatively (p < 0.01). CONCLUSION: MR imaging allows accurate combined assessment of LV function, bypass patency and flow. The protocol of this study may be applicable for perioperative follow-up studies in patients after CABG surgery.

Management of transposition of the great arteries with single coronary artery.

Approximately 5% of patients with transposition of the great arteries have a single coronary artery. In the early years of the arterial switch procedure a single coronary artery was associated with an increased risk of mortality. This was particularly true for the most common type of single coronary artery in which there is a right posterior ostium giving rise to a right coronary artery that passes to the right atrioventricular groove and a left coronary artery that passes posterior to the pulmonary artery. An understanding of the mechanisms by which this coronary pattern increases the risk of mortality has led to neutralization of this risk factor. The risk of late reintervention after an arterial switch with single coronary artery is increased with a single left posterior ostium with the right coronary passing anterior to the aorta. The mechanism remains unclear.