Magnetic resonance assessment of aortic and mitral regurgitation

CMR in Evaluating Valvular Heart Disease: Diagnosis, Severity, and Outcomes

Cardiac magnetic resonance (CMR) is a versatile imaging tool that brings much to the assessment of valvular heart disease. Although it is best known for myocardial imaging (even in valve disease), it provides excellent assessment of all 4 heart valves, with some distinct advantages, including a free choice of image planes and accurate flow and volumetric quantification. These allow the severity of each valve lesion to be characterized, in addition to optimal visualization of the surrounding outflow tracts and vessels, to deliver a comprehensive package. It can assess each valve lesion separately (in multiple valve disease) and is not affected by hemodynamic status. The accurate quantitation of regurgitant lesions and the ability to characterize myocardial changes also provides an ability to predict future clinical outcomes in asymptomatic patients. This review outlines how CMR can be used in cardiac valve disease to compliment echocardiography and enhance the patient assessment. It covers the main CMR methods used, their strengths and limitations, and the optimal way to apply them to evaluate valve disease.

One year follow-up of patients with reduced left ventricular ejection fraction (LVEF) on lipoprotein apheresis

BACKGROUND

Left ventricular ejection fraction (LVEF) is a valuable measure to assess left ventricular systolic function. Lipid lowering therapy by statins has been shown to have an impact on LVEF already after a 6 months treatment. Higher doses of statins have been claimed to be more effective as compared to a conventional one and even a difference between lipophilic and hydrophilic compounds has been reported. The effect of regular lipoprotein-apheresis (LP-apheresis) on LVEF was previously poorly examined. Patients involved in a regular LP-apheresis program are supposed to undergo a number of follow-up investigations among them myocardial scintigraphy and LVEF, measured by radionuclide ventriculography.

METHODS

We examined 18 patients before initiation and after one year of ongoing LP-apheresis. 13 patients (11 males, 2 females, mean age 58.3 ± 5.3 years, groups A) were since more than a year on stable, unchanged statin treatment (atorvastatin 40 mg, simvastatin 40 mg, rosuvastatin 20 mg±ezetimibe), the other 5 patients (3 males, 2 females, mean age 57.1 ± 4.6 years, group B) were intolerant to statins being on micronized fenofibrate±resorption inhibitors (cholestyramine). All patients had a Lp(a) < 30 mg/dl. As part of the usual follow-up monitoring, LVEF was determined by means of radionuclide ventriculography after application of 550 MBq ^99m Tc-pertechnetate.

RESULTS

The follow-up LVEF was checked at a mean of 48.7 weeks in group A and 51.2 weeks in group B. Except in 1 patient (LVEF 46.8% before vs. 45.2% after LP-apheresis initiation) in group A we noted a significant increase in LVEF in 12 patients of group A (92%) and in all patients of group B. Mean LVEF increased significantly in both groups (A: 42.7±8.1 → 46.5±7.5% (p < 0.001) and B: 41.9±8.4 → 46.5±6.3 %; p < 0.001). The relative rise was nearly identical (group A 9.6%, in group B 9.7%).

CONCLUSIONS

Our findings indicate that regular long-term LP-apheresis treatment apparently increases LVEF, independently on current statin treatment. This implies a role of lowering of atherogenic lipoproteins as underlying mechanism. A prospective study should clarify the relative extent of LVEF improvement induced by LP-apheresis.

Clinical recommendations of cardiac magnetic resonance, Part I: ischemic and valvular heart disease: a position paper of the working group 'Applicazioni della Risonanza Magnetica' of the Italian Society of Cardiology

Cardiac magnetic resonance (CMR) has emerged as a reliable and accurate diagnostic tool for the evaluation of patients with cardiac disease in several clinical settings and with proven additional diagnostic and prognostic value compared with other imaging modalities. This document has been developed by the working group on the 'application of CMR' of the Italian Society of Cardiology to provide a perspective on the current state of technical advances and clinical applications of CMR and to inform cardiologists on how to implement their clinical and diagnostic pathways with the inclusion of this technique in clinical practice. The writing committee consisted of members of the working group of the Italian Society of Cardiology and two external peer reviewers with acknowledged experience in the field of CMR.

Global and regional functional assessment of ischemic heart disease with cardiac MR imaging

Cardiac MR imaging (CMR) combines assessment of myocardial function and tissue characterization, and is therefore ideally suited to evaluating patients with ischemic heart disease (IHD). This article discusses evaluation of left ventricular global function at CMR, reviewing the literature supporting global parameters in risk stratification and assessment of treatment response in IHD. Techniques for assessment of regional myocardial function are reviewed, and normal myocardial motion and fiber arrangement discussed. Despite barriers to clinical adoption, integration of this assessment into clinical routine should improve the ability to detect functional consequences of early myocardial structural alterations in patients with IHD.

Heart valve disease: investigation by cardiovascular magnetic resonance

Cardiovascular magnetic resonance (CMR) has become a valuable investigative tool in many areas of cardiac medicine. Its value in heart valve disease is less well appreciated however, particularly as echocardiography is a powerful and widely available technique in valve disease. This review highlights the added value that CMR can bring in valve disease, complementing echocardiography in many areas, but it has also become the first-line investigation in some, such as pulmonary valve disease and assessing the right ventricle. CMR has many advantages, including the ability to image in any plane, which allows full visualisation of valves and their inflow/outflow tracts, direct measurement of valve area (particularly for stenotic valves), and characterisation of the associated great vessel anatomy (e.g. the aortic root and arch in aortic valve disease). A particular strength is the ability to quantify flow, which allows accurate measurement of regurgitation, cardiac shunt volumes/ratios and differential flow volumes (e.g. left and right pulmonary arteries). Quantification of ventricular volumes and mass is vital for determining the impact of valve disease on the heart, and CMR is the 'Gold standard' for this. Limitations of the technique include partial volume effects due to image slice thickness, and a low ability to identify small, highly mobile objects (such as vegetations) due to the need to acquire images over several cardiac cycles. The review examines the advantages and disadvantages of each imaging aspect in detail, and considers how CMR can be used optimally for each valve lesion.

CMR of Ventricular Function

Cardiovascular magnetic resonance (CMR) is the reference standard for the assessment of ventricular dimensions, function, and mass in terms of accuracy and reproducibility. It has been thoroughly validated both ex vivo and against other imaging techniques. Measurements are highly accurate and no geometrical assumptions need to be made about the ventricle. A routine ventricular dataset of images can be acquired in less than 5 minutes and analyzed in about the same time. The field is rapidly advancing with increasing automation and simplification in both image acquisition and analysis. Using parallel and real time imaging techniques, good quality data can be obtained even in patients who are unable to hold their breath. While providing useful information in all patients with suspected heart failure, CMR should particularly be considered in those with poor echo windows, where it can also be combined with myocardial stress. Tagging techniques can provide highly detailed information about myocardial torsion and strain for individual myocardial segments. In a research environment, the very high degree of interscan reproducibility can dramatically reduce the number of patients needed to perform clinical trials.

Cardiovascular magnetic resonance in the quantitative assessment of left ventricular mass, volumes and contractile function

Cardiovascular magnetic resonance is a well validated, highly accurate and reproducible technique for the assessment of ventricular volumes, function and mass. State of the art cardiovascular magnetic resonance practice is capable of a ventricular assessment that includes not only systolic but also diastolic function. Thus, it provides an insight into the complex changes in ventricular morphology, physiology and function in cardiovascular disease. This has produced great interest not only in its clinical utilization but also as an important research tool. As refinement of the technique continues to incorporate hardware and software developments, the technique becomes quicker, more accurate and easier to analyse. Here, we review recent developments and current practice.

Regurgitant jet evaluation using three-dimensional echocardiography and magnetic resonance

BACKGROUND

Three-dimensional assessment of regurgitant jet volume is the prerequisite for stratifying valve insufficiency. However, systematic comparison of three-dimensional methods is lacking. Therefore, we evaluated magnetic resonance imaging and three-dimensional echocardiography experimentally.

METHODS

An insufficiency chamber (22 x 18.5 x 27 cm; ostia 10, 16, and 20 mm; regurgitant volumes 2.3 to 25 mL) within experimental circulation (BioMedicus pump, tubes, pulsatile flow 0.2 to 1.9 L/min) was used for three-dimensional echocardiography (HP Sonos 2500) and magnetic resonance imaging (Siemens Magnetom Vision). Doppler flowmeter served as a gold standard. Segmentation used thresholding and surface integration of velocity vectors. Jet volume was evaluated qualitatively by polynom fitting.

RESULTS

Jet volume calculated by magnetic resonance (r = 0.99, p < 0.0001) and by echocardiography (r = 0.99, p < 0.0001) correlated identically to the gold standard. Jet volume derived from imaging correlated with each other by r = 0.98 (p < 0.0001). Polynom fits indicated a more paraboloid shape of magnetic resonance jet volume.

CONCLUSIONS

Experimentally, three-dimensional echocardiography and magnetic resonance imaging possess identical accuracy for determining regurgitant jet volume. Magnetic resonance imaging seems to provide qualitatively better image data for three-dimensional reconstruction.

Computed tomography and magnetic resonance imaging of patients with valvular heart disease

Although computed tomographic (CT) and magnetic resonance (MR) evaluation of patients with valvular heart disease is almost never performed as a first line of diagnostic intervention, their performance does provide important morphologic and physiologic information concerning the etiology and the current status of the valvular dysfunction. Evaluation of chamber and great artery size as well as ventricular wall thickness provide the basis for diagnosing and analyzing severity of valvular heart disease. Furthermore, additional findings, including calcification and evidence of interstitial pulmonary edema, increase diagnostic sensitivity and confidence in diagnosis. MR examination has the advantage over CT of providing direct demonstration of the signal void jets of dysfunctional valves, as well as a means of quantitating regional and global ventricular function and severity of valvular pressure gradients.

Magnetic resonance imaging of valvular heart disease

The optimum management of patients with valvular heart diseases requires accurate and reproducible assessment of the valvular lesion and its hemodynamic consequences. Magnetic resonance imaging (MRI) techniques, such as volume measurements, signal-void phenomena, and velocity mapping, can be used in an integrated approach to gain qualitative and quantitative information on valvular heart disease as well as ventricular dimensions and functions. Thus, MRI may be advantageous to the established diagnostic tools in assessing the severity of valvular heart disease as well as monitoring the lesion and predicting the optimal timing for valvular surgery. This paper reviews the validation of these MRI techniques in assessing valvular heart disease and discusses some typical pitfalls of the techniques, including suggestions for solutions.J. Magn. Reson. Imaging 1999;10:627-638.

Imaging cardiac structure and pump function

This article describes magnetic resonance imaging approaches for assessing cardiac structure and myocardial pump function. The article is divided into cardiac structure and ventricular function. Throughout, representative images are included. There are numerous applications of magnetic resonance imaging for assessing cardiac structure and function, and magnetic resonance imaging compared favorably to other imaging modalities.

Echocardiographic quantitation of mitral regurgitation: a new Doppler technique

Our objective is to develop a new transthoracic Doppler echocardiographic technique to determine mitral regurgitant fraction. The standard color Doppler method for assessment of mitral regurgitation is semiquantitative and dependent on instrument gain. By using the mitral and aortic valve continuous wave Doppler velocities, one can determine regurgitant fraction. This technique takes into account the flow dependence of the mitral valve area. Two constants, A and B, which represent the flow dependence of the mitral valve area and the ratio of the mitral valve area to aortic valve area at zero flow, respectively, were determined by regression in 36 patients without valvular disease (r = .89). Thirty patients with isolated mitral regurgitation were then studied. The mitral regurgitant fraction was calculated from the following: Regurgitant fraction = 1 - TVIav/Bf[Vmv/(1 - AVmv)]dt, where TVIav is the time velocity integral across the aortic valve, Vmv is the continuous wave velocity across the mitral valve, and A and B are constants. The regurgitant fraction was then compared with color Doppler assessment of mitral regurgitation assessed by independent observers. In patients with mitral regurgitation, there was a strong correlation between standard visual assessment and our new Doppler method (Kendall's tau b rank correlation = 0.65; p < .001). The new Doppler method was able to correctly categorize 90% of patients with mild mitral regurgitation and 88% of patients with severe mitral regurgitation; however, there was poorer agreement with the color Doppler assessment of moderate mitral regurgitation. Mitral regurgitant fraction can be calculated with our new Doppler method. This method is quantitative, objective, nongain dependent, and separates mild from severe mitral regurgitation well.

Rapid assessment of left ventricular volume by short axis cine MRI

MRI is an established and accurate method of measuring left and right ventricular volumes by summing chamber areas in multiple contiguous slices. Acquisition time may be up to 45 min. We have estimated volumes with gradient echo imaging to test the accuracy of a more rapid method (total acquisition time 15 min) using a recognized echocardiographic algorithm. The results were compared with the spin echo method. We studied 20 patients (mean age 52 years, 15 male) within 6 months of anterior myocardial infarction and 20 normal subjects (mean age 40 years, 19 males). For the rapid method, cine acquisitions were made in the horizontal long axis plane and in two short axis planes which divided the long axis into three equal parts. Volume was calculated assuming the ventricle to be composed of a cylinder, a truncated cone and a cone. There was good agreement between the two methods at end diastole with a mean difference (+/- standard error, +/- 95% confidence interval for limits of agreement) of -3 ml (+/- 8.3, +/- 37%) for normal subjects and 1.5 ml (+/- 4.2, +/- 25%) for patients. Agreement was less good at end systole with mean difference of 12.1 (+/- 3.5, +/- 41%) for normal subjects and 25.7 (+/- 3.7, +/- 47%) for patients. The rapid method, therefore, significantly underestimated end systolic volume compared with the previous method. Rapid measurements of end diastolic volume are more accurate than those of end systolic volume and hence ejection fraction. Provided the potential error is recognized, the rapid technique can be used in routine clinical practice in both normal and abnormal ventricles.

Magnetic resonance imaging in congenital heart disease in children

Images

A segmented K-space velocity mapping protocol for quantification of renal artery blood flow during breath-holding

Two important prerequisites for MR velocity mapping of pulsatile motion are synchronization of the sequence execution to the time course of the flow pattern and robustness toward loss of signal in complex flow fields. Synchronization is normally accomplished by using either prospective ECG triggering or so-called retrospective gating. However, if the studied vessel moves periodically in space as a result of respiratory motion, as in the case of renal arteries, a second synchronization with respect to the vessel motion in space may be necessary. One method to overcome this problem is to use the segmented k-space technique, in which the entire data acquisition can be made within a breath-hold by the sampling of several phase-encoding lines within a small time window during each heart cycle. The aim of this study was to investigate the performance of a segmented k-space velocity mapping protocol for renal artery flow determination. The protocol uses 16 phase-encoding lines per heart beat during 16 heart cycles and gives a temporal velocity resolution of 160 msec. Comparison with a conventional ECG-triggered velocity mapping protocol was made in phantoms as well as in volunteers. In our study, both methods showed sufficient robustness toward complex flow in a phantom model. In comparison with the ECG technique, the segmentation technique reduced vessel blurring and pulsatility artifacts caused by respiratory motion, and average flow values obtained in vivo in the left renal artery agreed between the two methods studied.(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of mitral stenosis with velocity-encoded cine-magnetic resonance imaging

Velocity-encoded cine-magnetic resonance imaging (VEC-MRI) is a new method for quantitation of blood flow with the potential to measure high-velocity jets across stenotic valves. The objective of this study was to evaluate the ability of VEC-MRI to measure transmitral velocity in patients with mitral stenosis. Sixteen patients with known mitral stenosis were studied. A 1.5 Tesla superconducting magnet was used to obtain velocity-encoded images in the left ventricular short-axis plane. Images were obtained throughout the cardiac cycle at 3 consecutive slices beginning proximal to the mitral coaptation point. To determine the optimal slice thickness for MRI imaging, both 10 mm and 5 mm thicknesses were used. Echocardiography including continuous-wave Doppler was performed on every patient within 2 hours of MRI imaging. Peak velocity was determined for both VEC-MRI and Doppler-echo images. Two observers independently measured the VEC-MRI mitral inflow velocities. Of the 16 patients, imaged data were incomplete in only 1 study, and all images were adequate for analysis. Strong correlations were found for measurements of mitral valve gradient for both 10 mm (peak r = 0.89, mean r = 0.84) and 5 mm (peak r = 0.82, mean r = 0.95) slice thicknesses. Measurements of peak velocity with VEC-MRI (10 mm) agreed well with Doppler: mean 1.46 m/s, mean of differences (Doppler MRI) 0.38 m/s, standard deviation of differences 0.2 m/s. These findings suggest that VEC-MRI can noninvasively determine the severity of mitral stenosis.

Quantification of mitral regurgitation by velocity-encoded cine nuclear magnetic resonance imaging

OBJECTIVES

The feasibility of velocity-encoded cine nuclear magnetic resonance (NMR) imaging to measure regurgitant volume and regurgitant fraction in patients with mitral regurgitation was evaluated.

BACKGROUND

Velocity-encoded cine NMR imaging has been reported to provide accurate measurement of the volume of blood flow in the ascending aorta and through the mitral annulus. Therefore, we hypothesized that the difference between mitral inflow and aortic systolic flow provides the regurgitant volume in the setting of mitral regurgitation.

METHODS

Using velocity-encoded cine NMR imaging at a magnet field strength of 1.5 T and color Doppler echocardiography, 19 patients with isolated mitral regurgitation and 10 normal subjects were studied. Velocity-encoded cine NMR images were acquired in the short-axis plane of the ascending aorta and from the short-axis plane of the left ventricle at the level of the mitral annulus. Two independent observers measured the ascending aortic flow volume and left ventricular inflow volume to calculate the regurgitant volume as the difference between left ventricular inflow volume and aortic flow volume, and the regurgitant fraction was calculated. Using accepted criteria of color flow Doppler imaging and spectral analysis, the severity of mitral regurgitation was qualitatively graded as mild, moderate or severe and compared with regurgitant volume and regurgitant fraction, as determined by velocity-encoded cine NMR imaging.

RESULTS

In normal subjects the regurgitant volume was -6 +/- 345 ml/min (mean +/- SD). In patients with mild, moderate and severe mitral regurgitation, the regurgitant volume was 156 +/- 203, 1,384 +/- 437 and 4,763 +/- 2,449 ml/min, respectively. In normal subjects the regurgitant fraction was 0.7 +/- 6.1%. In patients with mild, moderate and severe mitral regurgitation, the regurgitant fraction was 3.1 +/- 3.4%, 24.5 +/- 8.9% and 48.6 +/- 7.6%, respectively. The regurgitant fraction correlated well with the echocardiographic severity of mitral regurgitation (r = 0.87). Interobserver reproducibilities for regurgitant volume and regurgitant fraction were excellent (r = 0.99, SEE = 238 ml; r = 0.98, SEE = 4.1%, respectively).

CONCLUSIONS

These findings suggest that velocity-encoded NMR imaging can be used to estimate regurgitant volume and regurgitant fraction in patients with mitral regurgitation and can discriminate patients with moderate or severe mitral regurgitation from normal subjects and patients with mild regurgitation. It may be useful for monitoring the effect of therapy intended to reduce the severity of mitral regurgitation.

Mitral and aortic valvular flow: quantification with MR phase mapping

When magnetic resonance phase mapping is used to quantitate valvular blood flow, the presence of higher-order-motion terms may cause a loss of phase information. To overcome this problem, a sequence with reduced encoding for higher-order motion was used, achieved by decreasing the duration of the flow-encoding gradient to 2.2 msec. Tested on a flow phantom simulating a severe valvular stenosis, the sequence was found to be robust for higher-order motion within the clinical velocity range. In eight healthy volunteers, mitral and aortic volume flow rates and peak velocities were quantified by means of phase mapping and compared with results of the indicator-dilution technique and Doppler echocardiography, respectively. Statistically significant correlations were found between phase mapping and the other two techniques. Similar studies in patients with valvular disease indicate that phase mapping is also valid for pathologic conditions. Phase mapping may be used as a noninvasive clinical tool for flow quantification in heart valve disease.

Assessment of mitral regurgitation by magnetic resonance imaging

To evaluate the potential of magnetic resonance imaging (MRI) in detection and quantification of mitral regurgitation, 26 pts. with echocardiographically or angiographically documented mitral regurgitation were examined using a 0.5 Tesla superconducting magnet. In each patient a multislice-multiphase study in a sagittal-coronal double angulated projection (four-chamber view equivalent) was performed to assess left and right ventricular volumes, ejection fraction and regurgitant fraction. Additionally a blood flow sensitive cine-study (fast field echo: FFE) was done to visualize direction and area of regurgitant jet. MRI data were compared with quantitative and quantitative assessment of mitral regurgitation by angiography, 2D echocardiography, Doppler sonography and color flow mapping. Using the FFE mode MRI was able to detect the regurgitant jet as a typical signal loss within the left atrium in all patients. The ratio of regurgitant jet area/left atrium area as determined by MRI showed a correlation with a comparable ratio from color Doppler sonography of R = 0.87 (p less than 0.001). There was also good agreement in semiquantitative grading of mitral regurgitation between MRI and angiography (R = 0.77, p less than 0.001). The determination of left and right ventricular stroke volume allowed the calculation of the regurgitant fraction, which showed a correlation with invasively determined regurgitation fraction of R = 0.84 (p less than 0.001). These data provide additional information that MRI may be useful as a noninvasive technique to detect and quantify mitral regurgitation.

Quantitation of antegrade and retrograde blood flow in the human aorta by magnetic resonance velocity mapping

Magnetic resonance velocity mapping was used in 24 normal subjects to study two-dimensional velocity profiles in the proximal and mid-ascending aorta, and to quantify both forward and reverse flow. The aortic flow measurements were validated by comparison with left ventricular stroke volume in all subjects and by comparison with pulmonary flow measurements in 12. Agreement was good with standard errors of the estimate of 7.8 and 7.1 ml, and correlation coefficients of 0.93 and 0.95, respectively. Systolic velocity maps were similar in the proximal aorta and the mid-ascending aorta, with maximum early systolic flow along the left posterior wall. Toward the end of systole and throughout diastole, a channel of reverse flow developed in the same region in the mid-ascending aorta, but in the proximal aorta it split to enter the sinuses of Valsalva, predominantly the left and the right coronary sinuses. Mean percentage ratio of retrograde-to-antegrade flow was 6.3%, with the majority of retrograde flow occurring in early diastole. The findings suggest that the retrograde flow is related to coronary artery flow and it is possible that aortic disease, which is known to influence aortic flow patterns, may also influence coronary flow.

Left ventricular volume measured rapidly by oblique magnetic resonance imaging

Magnetic resonance measurements of left ventricular volume and ejection fraction based on measurements of area and length in a single oblique plane containing the long axis of the ventricle were compared with measurements made by summing the areas of the chamber in multiple contiguous slices. The multislice technique is known to be accurate, but the single slice technique is much quicker; it takes only nine minutes of acquisition time for both volume and ejection fraction. In 25 normal subjects there was good agreement between the two methods of measuring volume with a mean (SD) difference between measurements of 2.0 (6.6) ml. In 20 patients with previous infarction it was less good with a mean (SD) difference of 4.5 (18.1) ml. The mean (SD) difference of ejection fraction measurements was -0.019 (0.038) in the normal subjects and -0.059 (0.106) in the patients, and the discrepancy between the two techniques was greatest in the patients with a pronounced abnormality of wall motion and low ejection fraction. In a further 25 normal subjects, the agreement between single plane volume measurements in the vertical and horizontal long axis planes was good, indicating that either plane is suitable for rapid measurement. Single plane measurements of left ventricular volume and ejection fraction can be made with the accuracies stated, which are sufficient for routine clinical use except in patients with a pronounced abnormality of wall motion. In combination with measurements of regional wall thickness and motion, previously described, the technique offers a rapid non-invasive assessment of both global and regional left ventricular function.

Comparison of magnetic resonance imaging with echocardiography and radionuclide angiography in assessing cardiac function and anatomy following Mustard's operation for transposition of the great arteries

The Mustard operation in infancy and childhood has successfully palliated many patients with transposition of the great arteries who have now survived to adulthood. Right ventricular dysfunction and tricuspid regurgitation are important determinants of late morbidity and mortality. The value of noninvasive magnetic resonance imaging (MRI) in the assessment of cardiac function and anatomy 9 to 20 years after this procedure has been investigated, and compared with findings on echocardiography, radionuclide ventriculography and angiography in 17 adult patients. Ejection fractions measured by MRI were higher compared with radionuclide ventriculography. The correlation for the left ventricle was closer (r = 0.75) than for the right ventricle (r = 0.49). Tricuspid regurgitation was assessed by Doppler echocardiography and by MRI using the right/left ventricular stroke volume ratio. The mean stroke volume ratio in those with Doppler evidence of tricuspid regurgitation was 1.6:1 compared to 1.1:1 in those without, and this difference reached significance (p less than 0.01). The anatomy of the great arteries was clearly visible in all patients. Five patients had a residual ventricular septal defect which, with the exception of 1 small defect, was easily visualized. The intraatrial baffle was best seen in transverse slices, and the systemic venous connection showed as a relatively narrow channel lying in the posterior part of the cavity. In general, baffle anatomy was easier to assess on 2-dimensional echocardiography.(ABSTRACT TRUNCATED AT 250 WORDS)

Magnetic resonance velocity mapping in aortic dissection

We describe three patients with chronic aortic dissection in whom both spin-echo magnetic resonance imaging (MRI) and cine field-echo imaging were performed. The field even-echo rephasing (FEER) sequence showed the intimal flaps much more clearly than the spin-echo sequence and provided a distinction between thrombus and static blood. Velocity mapping allowed flow measurements in the true and false lumens. The management of the three patients was based upon the information provided by MRI. It is suggested that MRI may avoid invasive investigation and be the method of choice in haemodynamically stable patients with aortic dissection provided that the FEER sequence is used.

Radionuclide detection of mild valvular regurgitation: its significance as assessed by Doppler sonography

Radionuclide ventriculography (RNV) indices of regurgitation, Fourier amplitude ratio (FAR) and additional RNV variables were prospectively compared to Doppler echocardiography (DE) in 108 consecutive patients with no or mild left ventricular regurgitation, to assess RNV accuracy in detecting regurgitation in patients with different cardiac disorders. Exclusion of left ventricular or tricuspid regurgitation allowed investigation of the FAR range at rest and during exercise in a sufficiently large appropriate reference group without regurgitation. FAR, as well as other RNV variables, failed to provide more information for the diagnosis of mild (clinically irrelevant) left ventricular regurgitation than the diagnosis upon admission alone. Despite the superiority of DE as a gold standard in the detection of mild regurgitation, at present evaluation of RNV regurgitation indices might be the only method to discover regurgitation arising during dynamic exercise.

Magnetic resonance velocity mapping: clinical application of a new technique

Magnetic resonance velocity mapping is a new technique which provides a display of velocity within the cardiovascular system at any point of the cardiac cycle. A short field echo sequence with even echo rephasing is used to obtain a signal from rapidly moving blood and a cine display is provided by rapid repetition of the sequence. The amplitude image shows the anatomy, with blood giving a high signal and areas of turbulent flow no signal. The phase image is a map of velocities at each point in the image plane. Thirteen cases are described in which the technique either provided a diagnosis or helped in functional assessment. Flow through atrial and ventricular septal defects was seen, although turbulent flow distal to the ventricular shunts led to some loss of quantitative information. In three patients with valve disease jets of abnormal flow were seen because of signal loss and it is suggested that the size of the area of turbulence may be used to quantify the severity of regurgitation. Velocities were measured in four coronary artery bypass grafts in two patients, and low velocity was seen in a graft with distal disease that supplied the infarcted territory. Velocity was reduced distal to an aortic coarctation and it was increased at the site of narrowing caused by thrombosis in a deep vein. The speed and direction of flow in the central vessels in a patient with complex congenital heart disease helped to establish the anatomy. The technique provides useful information in a wide range of disorders of the cardiovascular system, and in some cases may avoid the need for invasive investigation.