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.

[Medical treatment after myocardial infarct: reflex prescription or thoughtful prescription]. / Le traitement médical après l'infarctus du myocarde: ordonnance réflexe ou ordonnance réfléchie.

There have been many therapeutic trials to determine the efficacy of given drugs prescribed after myocardial infarction. This may be explained by the very number of families of drugs which may intervene during the evolution of coronary artery disease. A common mistake is to think that the results of therapeutic trials can be automatically applied in clinical practice. In order for the demonstrated effect of a product to lead to its automatic prescription, there must be confirmation that the importance of the expected benefits does not depend on the type of infarction. This is probably the case for aspirin and the reduction of cholesterol levels which seem to be effective irrespective of the characteristics of the initial infarction. On the other hand, the efficacy or dangers of anti-ischaemic drugs, angiotensin converting enzyme inhibitors or antiarrhythmics, is very dependent on the impact of the infarct on left ventricular function. The prescription of drugs after myocardial infarction depends on individual parameters which lead to the adaptation of consensus recommendations to each particular case.

[Study of myocardial viability after recent infarction by echocardiography under dobutamine. Evidence of stunned myocardium]. / Etude de la viabilité myocardique après infarctus récent par l'échocardiographie sous dobutamine. Mise en évidence du myocarde sidéré.

After myocardial infarction treated by thrombolysis, secondary improvement of contractility may be observed due to the presence of viable but stunned myocardium in a zone of ischaemia. Echocardiography with lose dose Dobutamine has been proposed as a diagnostic test of myocardial viability. The inotropic effect of the pharmacological agent improves or induces myocardial thickening in zones of ischaemia. A positive response is observed in about one out of two cases. The sensitivity ranges from 79 to 86% and the specificity from 68 to 90% in the reported series. This mode of stress echocardiography for the study of post-infarction myocardial viability is under clinical evaluation: its advantages and limitations should be compared with those of other non-invasive methods, especially thallium myocardial scintigraphy.

[Medical treatment of patients with stable angina pectoris]. / Traitement médical des patients ayant un angor stable.

Stable angina is usually due to coronary atherosclerosis and complicated by myocardial lesions responsible for ischaemic myocardiopathy. Tobacco suppression, aspirin and cholesterol lowering drugs especially statins are the best way to slow coronary atherosclerosis progression. beta-blockers, physical conditioning are the two main medical means to suppress anginal symptoms. Converting enzyme inhibitors and beta-blockers are useful to slow the progression rate of ischaemic cardiomyopathy. Revascularisation procedures are combined with medical treatment and help treating symptoms and preventing myocardial lesions.

Velocity-encoded cine MRI in the evaluation of left ventricular diastolic function: measurement of mitral valve and pulmonary vein flow velocities and flow volume across the mitral valve.

Left ventricular diastolic function has been evaluated by means of analysis of the flow pattern through the mitral valve. Velocity-encoded cine magnetic resonance imaging (VEC-MR) is a new method for characterizing flow patterns in the heart. The feasibility of using VEC-MR to measure early diastolic (E) and atrial systolic (A) peak flow velocities and E/A ratios in the mitral inflow, as well as systolic (X), early diastolic (Y), and atrial systolic (Z) peak flow velocities and X/Y ratios in the pulmonary vein, was evaluated in 10 normal volunteers. The VEC-MR-derived velocities and indexes were compared with Doppler-derived results. Volumetric flow across the mitral valve was also used to measure stroke volume, cardiac output, and the left atrial contribution of left ventricular filling. VEC-MR yielded lower peak velocities than Doppler echocardiography. The velocities of the two measurements showed a significant linear correlation (Doppler E velocity = 1.30 x VEC-MR + 1.6 cm/sec, r = 0.68; Doppler A velocity = 1.83 x VEC-MR - 5.2 cm/sec, r = 0.83; and Doppler X velocity = 0.45 x VEC-MR + 0.09 cm/sec, r = 0.74). Consequently the E/A and X/Y ratios measured by these two methods showed statistically significant linear correlations with r values of 0.94 and 0.83. The volume of blood flow across the mitral valve measured by VEC-MR (5610 +/- 620 ml/min) was not statistically different from the cardiac output measured from the ascending aorta by VEC-MR (5670 +/- 590 ml/min) or by left ventricular cine magnetic resonance imaging (5440 +/- 614 ml/min). The left atrial contribution to left ventricular filling was 25.9 +/- 7.5%. Our results indicate that VEC-MR can be used not only for evaluation of left ventricular diastolic filling from the mitral valve and pulmonary vein flow velocities but also for quantitative measurement of the volume of blood flow across the mitral valve.