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Fast breathhold cardiovascular magnetic resonance (CMR) has become a reference standard for the measurement of cardiac volumes, function, and mass. The implications of this for sample sizes for remodeling studies in heart failure (HF) have not been elucidated. We determined the reproducibility of CMR in HF and calculated the sample size requirements and compared them with published values for echocardiography. Breathhold gradient echo cines of the left ventricle were acquired in 20 patients with HF and 20 normal subjects. Sample size values were calculated from the interstudy standard deviation of the difference. The percentage variability of the measured parameters in our HF group of intraobserver (2.0-7.4%), interobserver (3.3-7.7%), and interstudy (2.5-4.8%) measurements was slightly larger than for our normal group (1.6-6.6%, 1.6-7.3%, and 2.0-7.3%, respectively) but remained comparable with previous studies in normal subjects. The calculated sample sizes in patients with HF for CMR to detect a 10-ml change in end-diastolic volume (n = 12) and end-systolic volume (n = 10), a 3% change in ejection fraction (n = 15), and a 10-g change in mass was (n = 9) were substantially smaller than recently published values for two-dimensional echocardiography (reduction of 81-97%). Breathhold CMR is a fast comprehensive technique for the assessment of cardiac volumes, function, and mass in HF that is accurate but also highly reproducible. This allows a considerable reduction in the patient numbers required to prove a hypothesis in research studies, which suggests a potential for important research cost savings.

Abstract-Left ventricular hypertrophy is associated with significant excess mortality and morbidity. The study and treatment of this condition, in particular the prognostic implications of changes in left ventricular mass, require an accurate, safe, and reproducible method of measurement. Cardiovascular magnetic resonance is a suitable tool for this purpose, and this review assesses the technique in comparison with others and examines the clinical and research implications of the improved reproducibility. Key Words: myocardium Ⅲ hypertrophy Ⅲ magnetic resonance imaging T he importance of left ventricular hypertrophy (LVH) in medicine is not widely appreciated. The Framingham Study, among others, showed that increased left ventricular (LV) mass is associated with a significant excess of cardiovascular mortality and morbidity. 1 This is independent of the presence of coronary artery disease 2 or hypertension, 1 with a tripling of the mortality rate in subjects with 1-3 and without 2 either of these. The risks of coronary, peripheral, or cerebrovascular disease are also raised, even among normotensive subjects with LVH. 1,4,5 The accurate measurement of LV mass has in the past been difficult, partly because of the oblique angle at which the heart lies within the chest, its continuous movement, and the lack of a technique for imaging the whole left ventricle. Initial measurements with ECG data were surrogate markers for LV mass, with values affected by positioning of the leads, orientation of the heart, and obesity. 6 -8 Nevertheless, criteria were developed for identifying LVH with ECG 9,10 that correlated to an extent with true LVH but were insensitive and nonspecific (specificity, 6% to 56%). 11-13 Imaging techniques have now supplanted the ECG, and we review these with particular reference to cardiovascular magnetic resonance (CMR). EchocardiographyEchocardiography (echo) was a distinct advance for LV mass measurement over the ECG, with direct visualization of the myocardium and real-time imaging, and many important studies examining the prognostic effects of LVH have used this method. 1,2,14 However, obtaining good quality images is dependent on a skilled operator, patient position and anatomy, obesity, and angle of the transducer beam, 15,16 and images of sufficient quality for LV mass measurement may not be obtained in up to one third of cases. 16 -18 The assumed geometric shape for both M-mode and 2D echo may lead to error, particularly as variations in ventricular geometry affect calculated LV mass. 19 The landmark trials, such as Framingham, 1 overcame the deficiencies in accuracy and reproducibility of echo with large numbers of subjects.M-mode is the commonest echocardiographic method for measuring LV mass, the images being easier to obtain and the calculations straightforward. Although validated against postmortem mainly normal hearts, 20,21 it suffers most from the assumption of geometric shape, and this variability is reflected in the poor accuracy of the technique, with standard errors of the estima...

Background-Increased extravascular compression and reduced diastolic perfusion time (DPT), rather than vascular remodeling, influence coronary microcirculatory dysfunction in aortic stenosis (AS). However, alterations after aortic valve replacement (AVR) remain unclear. The aim of the present study was to quantify changes in transmural perfusion and coronary vasodilator reserve (CVR), a measure of microcirculatory function, after AVR and determine the relative contribution of left ventricular mass (LVM) regression, change in aortic valve area (AVA), and DPT. Methods and Results-Twenty-two patients with AS were studied before and 1 year after AVR using echocardiography to measure AVA, cardiovascular magnetic resonance to assess LVM, and positron emission tomography to quantify resting and hyperemic myocardial blood flow (MBF) and CVR. Regression of LVM occurred in all patients (from 129Ϯ30 to 94Ϯ24 g/m 2 ; PϽ0.0001), and there was a significant reduction in resting MBF and increase in CVR corrected for rate-pressure product after AVR, although these changes displayed marked heterogeneity. Regression of LVM was linearly related to change in resting total LV blood flow but not CVR. Increase in hyperemic MBF and CVR transmurally was directly related to the increase in AVA after AVR. A significant relationship existed between the change in hyperemic DPT (1.0Ϯ4.7 s/min [range, 6.8 to 9.6]) and change in transmural CVR (yϭ0.08xϩ0.18; rϭ0.44; Pϭ0.04). Conclusions-Changes

Our objective was to establish a cardiovascular magnetic resonance (CMR) cardiac function clinic to provide an assessment of cardiac volume, mass, and function in patients with heart failure on the same day as their cardiology outpatient clinic appointment. Sixty-four patients attended the CMR function clinic. The reproducibility, patient acceptability, and time efficiency of the CMR clinic were assessed and compared with radionuclide ventriculography (RNV) and echocardiography (echo). Reports were available in the cardiology outpatient clinic within 2 hr of the CMR appointment time. The reproducibility of volumes, ejection fraction, and mass in this heart failure population was good and comparable with CMR studies in the normal population. CMR was more acceptable to the patients than both RNV and echo (p < 0.05). The total time for CMR was less than that of RNV (42 +/- 4 and 61 +/- 4 min, respectively; p < 0.001) but more than that of echo (echo, 23 +/- 2 min; p < 0.001). Comparison of ejection fractions revealed a correlation between CMR and RNV of 0.7, but Bland-Altman limits of agreement were wide (-10.5% to 18.9%). For CMR versus echo, the correlation was 0.6, and the limits of agreement were wider (-29.9% to 23.3%). The correlation between RNV and echo was 0.2 with wider limits of agreement (-29.8% to 24. 9%). In conclusion, CMR can provide a rapid, reproducible, and patient acceptable assessment of cardiac function in heart failure patients, whereas other methods appear to have a wider variance. The high reproducibility of CMR lends itself to the follow-up of clinical progression and the effect of treatment in patients with heart failure.

The EF measurement by echo, angio, RNV, and CMR are not interchangeable in patients following heart transplantation. The CMR and RNV provided the best agreement in EF and appear preferable for research studies. Echocardiography systematically overestimated LV EF and showed poor agreement with other techniques. Angiography overestimated LV function, and its routine use did not add to information gained from noninvasive studies.

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