In recent years, some concepts regarding the etiology and hemodynamics present in the syndrome of mitral regurgitation have changed. Coronary artery disease and mitral valve prolapse have replaced rheumatic heart disease as the most frequent cause of mitral regurgitation. Hemodynamic studies have shown that tall V waves in the pulmonary capillary wedge tracings are neither specific nor sensitive in detecting the presence of mitral regurgitation. In this study, we evaluated the role of various clinical, echocardiographic, and hemodynamic findings with regard to left atrial (LA) size, pressure, and V wave height. We found that the mean pulmonary capillary wedge pressure (PCW) and V wave height for the subset of patients with acute mitral regurgitation (PCW = 24.1 +/- 10.9; V = 41.2 +/- 20.7 mm Hg) was similar to the subset with chronic mitral regurgitation (PCW = 17.9 +/- 7.5; V = 32.0 +/- 18.2 mm Hg). In addition, we found that there was a significant logarithmic relationship between the LA size and the duration of the mitral regurgitation (y = 1.404 [log X] + 3.948; R = 0.678; p less than 0.0005). Lastly, we found that LA size, compliance, regurgitant volume, and regurgitant valve orifice area all increase with time.

Summary:Recent studies have shown that rheumatic heart disease is no longer the main cause of isolated severe pure mitral regurgitation. In this study, we evaluated various clinical and echocardiographic features found in the syndrome of mitral regurgitation. Our data is consistent with recent reports that mitral valve prolapse and coronary artery disease are now the predominant causes of mitral regurgitation and that rheumatic heart disease is a much less common etiology. In addition, our data suggest that clinical evaluation alone is usually very accurate in identifying the correct etiology. Various clinical and echocardiographic features found in the subsets of acute and chronic mitral regurgitation are described. Specifically, patients with acute mitral regurgitation were more likely to have echocardiographic evidence of segmental left ventricular dysfunction and flail mitral valve leaflet. In chronic mitral regurgitation, atrial fibrillation and left atrial dilatation were more commonly present. Echocardiography was found to be more useful in the detection of the

Nitrogen and carbon electron densities of the toluidines and xylidines have been recalculated by the INDO method; previously published errors have been corrected. Although the nitrogen-15 chemical shifts of these compounds still display the earlier suggested correlation with u and total electron densities, the calculated inverse correlation with proton electron densities has been shown to be incorrect. Methyl proton chemical shifts of these compounds display no meaningful correlation with the nitrogen shitts. The nitrogen chemical shifts of the toluidinium and xylidinium ions correlate moderately well with the "C chemical shifts of the analogous di-and tri-methylbenzenes.Recently, Adler and Lichter reported a correlation between the I5N chemical shifts of toluidines and xylidines, and the INDO-MO total and sigma electron densities at the nitrogen atoms."* A corollary of that calculation was the possible existence of a relationship between the nitrogen and methyl proton resonance positions. After publication of this work, two errors were discovered, and it is the purpose of this note to correct these errors and assess the implications of the corrected results. In addition, we report the nitrogen chemical shifts of the corresponding toluidinium and xylidinium ions (1) to show that when the lone-pair is absent, the nitrogen shifts correlate with methyl carbon shifts of the corresponding methylbenzenes (2) in the manner suggested3 for aliphatic amines. EXPERIMENTALSamples were commercially available and were purified by distillation just before use. Carbon tetrachloride and deuteriochloroform, used for the proton spectra, were also distilled just before use. The anilinium ions were prepared as 2~ solutions in trifluoroacetic acid, and under these conditions the anilines are completely protonated. Approximately 10% deuteriobenzene was added as an internal lock. Several samples, noted in Table 3, were run as the hydrochlorides in water, containing c. 10% D,O as internal lock.Proton spectra of the methylanilines were recorded on a Varian A-60A spectrometer using a sweep width of 50Hz and a sweep rate of 0.2Hzs-'. Chemical shifts were measured with audio sideband calibration * Author to whom correspondence should be addressed.t Jonas E. Salk Awardee, City University of New York, 1975. with respect to c. 2% internal TMS. The values reported are the averages of three measurements each in the forward and reverse sweep directions, and are accurate to k0.005 ppm. Nitrogen chemical shifts of the anilinium ions were determined at 10.09 MHz on a JEOL PS/PFT-lOO spectrometer equipped with the JEOL EC-100 data system. Chemical shifts were determined with respect to a 2 . 9~ solution of 95% enriched ammonium chloride in 1~ HC1 contained in a 2 mm capillary placed concentrically inside the 10 mm sample tube. Spectra were determined with complete proton decoupling, and were accumulated over a 4kHz range and 8 K words of memory, using 30" pulse widths and a 1.1 s repetition rate. The chemical shifts are assumed accurate to ItO.1 pp...