Ernst Wellnhofer

Improved Accuracy of Quantitative Assessment of Left Ventricular Volume and Ejection Fraction by Geometric Models with Steady-State Free Precession

The purpose of this study was to determine whether steady-state free precession (SSFP) could improve accuracy of geometric models for evaluation of left ventricular (LV) function in comparison to turbo gradient echo (TGrE) and thereby reduce the acquisition and post-processing times, which are commonly long by use of the Simpsons Rule. In 25 subjects, cine loops of the complete heart in short and horizontal long-axis planes were acquired using TGrE (TR/TE/flip = 5.0/1.9/25) compared with SSFP (TR/TE/flip = 3.2/1.2/60). LV volumes and EF were measured with various geometric models for TGrE and SSFP. With three-dimensional data, the LV volumes were higher and the resulting EF lower for SSFP in contrast to TGrE (51 +/- 15% vs. 57 +/- 15%, p < 0.001). With SSFP, various geometric models yielded good to excellent correlations for LV volumes and LVEF compared to volumetric data (r = 0.94-0.98, mean relative difference 7.0-11.4%). In contrast, correlations were low using biplane or single-plane ellipsoid models in TGrE (r = 0.71-0.75, mean relative difference 15.9-30.2%). A new combined geometric model, taking all three dimensions into account, yielded the highest accuracy for SSFP in comparison to volumetric data (r = 0.99, mean relative difference 4.7%). Geometric models for assessment of LV volumes and EF yield higher accuracy and reproducibility by use of the SSFP sequence than by standard TGrE. This may increase clinical utility of magnetic resonance by shorter acquisition and processing times.

Noninvasive determination of coronary blood flow velocity with magnetic resonance imaging: comparison of breath-hold and navigator techniques with intravascular ultrasound.

The aim of this study was to evaluate two different magnetic resonance (MR) techniques for the noninvasive assessment of intracoronary blood flow. Coronary blood flow velocities were measured invasively in 26 angiographically normal segments of 12 patients. Noninvasive measurements were performed in identical segments with two MR techniques using a 1.5 T MR tomograph (ACS NT, Philips). A single breath‐hold technique (temporal resolution: 140 msec) and a similar non‐breath‐hold technique with prospective navigator correction and improved temporal resolution (45 msec) were used. Maximal coronary flow velocities determined by MR correlated closely with invasive measurements (breath‐hold: r = 0.70; navigator: r = 0.86); however, a significant underestimation of the MR measurements was found (slope = 0.33 and 0.37). The relative difference from the invasive method was lower for the navigator technique compared with the breath‐hold technique (P < 0.02). Both MR techniques allow the determination of coronary blood flow velocities. The higher temporal resolution and shorter acquisition window of navigator‐corrected non‐breath‐hold techniques lead to increased accuracy. This approach is a further step toward the diagnostic use of MR flow measurements in coronary artery disease. Magn Reson Med 41:544–549, 1999.

Non-HLA antibodies targeting vascular receptors enhance alloimmune response and microvasculopathy after heart transplantation.

Background Non–human leukocyte antigen antibodies (Abs) targeting vascular receptors are implicated in the pathogenesis of renal allograft vascular rejection and in progressive vasculopathy in patients with systemic sclerosis. Methods We prospectively tested in 30 heart transplant recipients the impact of Abs directed against endothelin-1 type A (ETAR) and angiotensin II type 1 receptors (AT1R, cell-enzyme–linked immunosorbent assay) at time of transplantation and during the first posttransplantation year on cellular and Ab-mediated rejection (immunohistochemistry, C3d, and immunoglobulins) and microvasculopathy in endomyocardial biopsy. Results Cellular rejection, Ab-mediated rejection, and microvasculopathy was found in 40% and 13%, 57% and 18%, and 37% and 40% of biopsies at 1 month and 1 year posttransplantation, respectively. Maximum levels of AT1R and ETAR Abs were higher in patients with cellular (16.5±2.6 vs. 9.4±1.3; P=0.021 and 16.5±2.5 vs. 9.9±1.9; P=0.041) and Ab-mediated rejection (19.0±2.6 vs. 10.0±1.3; P=0.004 and 19.4±2.7 vs. 9.0±1.7; P=0.002), as compared with patients who had no rejection. Patients with elevated AT1R Abs (53% [16/30]) or ETAR Abs (50% [15/30]; pretransplantation prognostic rejection cutoff >16.5 U/L) presented more often with microvasculopathy (both, 67% vs. 23%; P=0.048) than patients without. Conclusions Elevated levels of AT1R and ETAR Abs are associated with cellular and Ab-mediated rejection and early onset of microvasculopathy and should be routinely monitored after heart transplantation.

Improved assessment of intravascular Doppler coronary flow velocity profile

Easy and safe in- vivo flow velocity studies in small coronary arteries have become feasible using a 0.014 ‘ or 0.018 ’ guidewire with an integrated Doppler probe in its tip (FloWire, Cardiometrics). Assessment of the flow velocity profile by the ratio of diastolic to systolic flow velocity (DSVR) is used as a diagnostic parameter. However, DSVR is a coarse quantifier of the flow velocity profile, and is subject to large physiologic variance and depends crucially on the quality of the Doppler signal. The aim of our study was to test parameters derived from statistical time series analysis for monitoring the quality of the instantaneous peak velocity (IPV) signal. Improvement of quantification of changes in quality and shape of flow velocity profiles by these parameters as compared to DSVR was a second goal.We investigated analog-digital converted IPV- signals and video registrations of corresponding greyscale spectra of intracoronary Doppler flow velocity signals. The signals were analyzed by using the autocorrelation function (ACF) in the time domain and a fast Fourier transform (FFT) in the frequency domain (standard time series statistics). The first minimum of autocorrelation function turned out to be very sensitive to signal quality, and Fishers g of the periodogram was the parameter of choice for shape analysis. In 11 patients with coronary artery disease, pre and post PTCA, the sensitivity of DSVR and signal to noise ratio to changes in shape and quality of the flow velocity signals was compared to that of the new parameters. Nineteen Doppler flow velocity samples of good quality from measurements in nonstenotic vessels and 7 flow velocity tracings with visible artefacts were used to assess the value of these parameters in monitoring signal quality.By comparison with corresponding parameters in use (SNR and DSVR) a significantly improved performance of the new statistical parameters was observed with respect to sensitivity to changes in signal quality and flow profile. In view of these results and because of the short calculation time of these variables they should be used for on-line quality control and analysis of flow velocity profiles.

Zuverlässigkeit der linksventrikulären Wandbewegungsanalyse mit dem gepulsten Gewebedopplerverfahren für das Timing von Myokardbiopsien und Koronarangiographien nach Herztransplantation

ZusammenfassungHintergrundRoutinemäßige invasive Screeningsnzur Überwachung akuter Abstoßungen (AR) und Suche nach Transplantatvaskulopathien(TVP) sind Standardprozeduren nach Herztransplantation.nDie Endomyokardbiopsien (EMB) und Kornarangiographien sindnjedoch teuer und für Patienten unangenehm und außerdem nicht risikofrei.nIm Rahmen unseres allgemeinen Bestrebens die invasiven Verlaufsuntersuchungennindikationsbedingt zu steuern, untersuchten wirndie Zuverlässigkeit des gepulsten Gewebedopplerverfahrens (PW-TDI)nfür das Timing invasiver Untersuchungen zwecks Verbesserung dernÜberwachung und Vermeidung unnötiger EMB und Herzkatheter(HK)–nUntersuchungen.MethodikWir testeten die diagnostische Wertigkeitnder an der basalen linksventrikulären (LV) Hinterwand gemessenennPW–TDI–Parameter für die Früherkennung der AR und TVP, indem wirndie Ergebnisse der vor 408 EMB– und 293 HK–Untersuchungen durchgeführtennPW–TDI–Wandbewegungsanalyse mit den als Standard benütztennErgebnissen der EMB (ISHLT–Klassifikation) und Koronarangiographien(mit oder ohne ergänzenden intravaskulären Ultraschall)nverglichen.ErgebnisseDie frühdiastolische Wandgeschwindigkeit undnRelaxationszeit erwiesen sich als sensitivste Parameter für die AR-Diagnosen(91,7 bzw. 93,3%) und besonders geeignet für die Früherkennungneiner AR. Der negative und positive prädiktive Wert dieser Parameternfür die AR-Diagnose ereichte 96 bzw. 92%. Für die funktionelle Beurteilungndes Schweregrades der AR, sowie für die Früherkennung einernTVP erwiesen sich die systolischen PW–TDI–Parameter als nützlicher.nBei Verschlechterung der systolischen PW–TDI–Funktionsparameter jenseitsnbestimmter „cutt–off“–Werte erreichte der positiv prädiktive Wertnfür eine TVP, je nach Parameter, 92–97%. Ab bestimmten Werten erlaubenndie systolischen Parameter den Ausschluss einer angiographischennTVP mit einer Wahrscheinlichkeit von bis zu 93%.SchlussfolgerungUnserenErgebnisse zeigen, dass mit dem PW–TDI ein zuverlässiges Abstoßungsmonitorinnmöglich ist, welches dem Patienten unnötige Routinebiopsiennersparen kann. Mit Hilfe der systolischen PW–TDI–Parameternist, aufgrund des hohen positiven und negativen prädiktiven Wertesnbestimmter Parametergrößen, auch eine Optimierung des Timings dernHK–Untersuchungen möglich.SummaryBackgroundInvasive screenings at predefined time intervalsnfor acute rejection (AR) and transplant coronary artery diseasen(TxCAD) are standard procedures. However cardiac biopsies and catheterizationsnare distressing and risky for the patients and are also costly.nWe assessed the reliability of pulsed–wave tissue Doppler imaging (PWTDI)nfor timing of invasive examinations in heart recipients, in an attemptnto avoid unnecessary endomyocardial biopsies (EMB) and catheterizations.MethodsPW–TDI, obtained at the basal left ventricular posteriornwall before 408 EMB and 293 catheterizations, was tested for itsndiagnostic value with regard to AR and TxCAD using ISHLT biopsyngrading, coronary angiography and intravascular ultrasound as standards.ResultsEarly diastolic peak wall motion velocity and relaxationntime showed high sensitivities for AR diagnosis (90.0 and 93.3% respectively)nand appeared particularly suited for the early detection of AR.nThe negative and positive predictive values for rejection of diastolicnparameter changes reached 96 and 92% respectively. Systolic PW–TDInparameters appeared to be useful for the evaluation of AR severity andnearly detection of wall motion alterations linked to TxCAD. At definitencutoff values for systolic parameters, the probability for TxCAD reachedn92 to 97%. Fischer’s classification functions allowed TxCAD exclusionnwith 80% probability.ConclusionsWithout diastolic parameter changes,nAR can be practically excluded and serial PW–TDI can save patientsnfrom routine EMB. The high specificity and negative predictive valuenfor TxCAD of reduced systolic peak velocities (Sm) and extended systolicntime (TSm) allow optimized timed catheterizations. Sm and TSm allowndiagnostic classifications that enable patients without alreadynknown TxCAD, but with high risk for catheterization, to be spared routinenangiographies.