The decision for surgical intervention in the treatment of stenosis and for regurgitation of the mitral valve demands an objective and quantitative evaluation of the severity of mitral valve disease. The availability of ultrasound techniques capable of analysing flow velocities across valves and to produce representative images of valve orifices has increased the interest in the hydraulics of cardiac valves. To isolate and study the determinants of transmitral flow, an in vitro model of the human left heart was built. From the model it is possible to differentiate the influence of the different determinants of left heart performance on transmitral flow: preload, compliance of the left atrium and ventricle, peripheral resistance (afterload) and heart rate. The mechanical part of the model consists of a reservoir connected to an elastic closed circuit (Latex pulmonary veins, left atrium, left ventricle and aortic arch) with replaceable mitral and aortic valves. The electronic part of the model drives and controls the hydraulic part, allowing the independent regulation and monitoring of left atrial and left ventricular pressures p, volumes V and 'pV-loops' throughout the cardiac cycle at different cardiac rhythms. Left atrial filling pressure and aortic resistance are variable in a controlled fashion. Echo-Doppler study of the mitral valve and the transmitral valve flow is possible both from an atrial and a ventricular window in the model. This technical note describes the model.

A dual chamber pacemaker was implanted during the first trimester of pregnancy in a patient with second-degree heart block and syncope. Transesophageal echocardiography was used to confirm satisfactory position in the right atrial appendage.

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The haemodynamic basis for paradoxical embolization in patients with stroke and decompression sickness has not yet been fully elucidated. Therefore right and left atrial pressures were measured simultaneously with peroperatively placed catheters after coronary artery bypass grafting in 17 patients with sinus rhythm and normal left ventricular function. Recordings were made both during spontaneous breathing and positive pressure ventilation. A cyclic pressure reversal in which right atrial pressure exceeded left atrial pressure was reproducibly recorded. It started on average 215 +/- 5 ms (mean +/- SEM) after the onset of the electrocardiographic P-wave, lasted on average 179 +/- 14 ms and had a maximal amplitude of on average 4.1 +/- 0.3 mmHg. During the expiration phase of spontaneous breathing and inspiration phase of positive pressure ventilation, the onset of the pressure reversal occurred later, its duration was shorter and its amplitude smaller. These observations demonstrate the presence of a cyclic inter-atrial pressure reversal and illustrate the importance of the breathing mode for the time course and amplitude of this reversal.

A fatal case of paraquat poisoning is described. Postmortem concentration of paraquat in different tissues reveals that treatment in this case could not prevent lethal tissue accumulation. Although accumulation was more pronounced in renal tissue, lung toxicity caused death. The formation of enormous fecaliths and the appearance of hypercalcemia are reported. Both were most likely connected with Füllers earth therapy. In spite of the fact that the exact nature of the equilibrium between plasma levels and tissue accumulation of paraquat (static or dynamic) is not understood, aggressive treatment must be recommended, even after the distribution phase and despite likely "fatal" plasma levels.