We sought to elucidate the mechanism of mitral regurgitation (MR) in dilated cardiomyopathy (DCM). Quantitative two-dimensional echocardiographic examinations were performed in 27 patients, 18 with DCM (nine with MR on physical examination, nine without MR) and nine without underlying heart disease. The MR and "no MR" patients were clinically comparable. Spatial reconstructions from multiple apical cross sections were

The conductance catheter is a promising new instrument for continuously measuring left ventricular (LV) volume. Absolute LV volume (V[t]) is related to uncorrected conductance volume, B(t), according to the equation: V(t)=(1/a)(B(t)-aVe). The aV, factor represents parallel-conductance volume due to conducting material outside the LV blood pool, and may be estimated by transiently changing blood conductivity using a bolus injection of hypertonic saline.a is the slope in the relation between B(t) and true LV volume. We tested the assumption that aVc and av are constant over a range of hemodynamic conditions. We performed multiple hypertonic saline aV, determinations in seven intact dogs during control conditions and subsequent temporary balloon occlusions of inferior vena cava (IVCO), aorta (AO), and pulmonary artery (PAO). We also compared B(t) with simultaneous biplane angiographic LV volume during similar control and intervention conditions. The saline-derived cvV, was 76±2 ml during control and fell significantly by -7±2 ml during IVCO (p<0.001) but not during AO or PAO. According to multiple linear regression analyses, the strongest predictor of saline-derived aV, was uncorrected end-systolic Bes, with a sensitivity coefficient of 0.60+±0.06 ml/ml (p<0.001). Angiographically derived aVc showed a similar dependence on Bes, with a coefficient of 0.77±0.14 ml/ml (p<0.001).Angiographically determined a also showed significant variation with hemodynamic interventions, largely reflecting an underlying dependence on aV,. The variation in aV, and av with LV size may stem from nonlinearity in the B(t)-V(t) relation. Although the conductance catheter provides a useful measure of relative LV volume, measurement of absolute LV volume over a wide hemodynamic range using constant aVc and a factors is unrealistic. This result calls into question the current use of this technique for the measurement of the absolute end-systolicpressure-volume relation. (Circulation 1989;80:1360-1377

The new england journal of medicine 1914 n engl j med 351;18 www.nejm.org october 28, 2004 immediate therapy, need to be ruled out by funduscopy.CT is helpful to localize and diagnose other ocular problems and diseases, such as orbital or scleral ruptures, solid tumors, and the presence of foreign bodies. However, positioning the patient on his or her back during CT can influence the location of the floating lens, possibly leading to misinterpretation.

No abstract

The pressure of pericardial constraint was measured in 20 patients undergoing elective cardiac surgery (10 in Group I with normal cardiac size; 10 in Group II with cardiomegaly) using a catheter with a collapsible latex end balloon. Right atrial pressure and other hemodynamic variables including right ventricular stroke work index were also measured before and after the pericardium was widely opened. The pericardium was grossly normal in all patients and only small physiologic effusions were present. In Group I mean pericardial pressure was 8 +/- 2 mm Hg as was mean right atrial pressure. In Group II mean pericardial pressure was 6 +/- 2 mm Hg versus mean right atrial pressure of 10 +/- 5 mm Hg (p less than 0.05). Excluding 2 of the 20 patients with outlying data, pericardial pressure showed linear correlation with right atrial pressure (r = 0.689). In Group I right ventricular stroke work index rose from 5.0 +/- 2.0 to 6.4 +/- 2.1 g-m/m2 (p less than 0.01) after pericardiotomy with no significant increase in mean right atrial pressure; similar findings in Group II were consistent with removal of external constraint. Thus, even in the absence of an abnormal effusion the normal pericardium exerts a significant pressure on the heart, which is often similar in magnitude to right atrial pressure. In certain notable exceptions, however, right atrial pressure far exceeds pericardial pressure. Such pericardial constraint has important implications for ventricular diastolic mechanics.