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Biomedical subjects

A Harley

Publications and source records attributed to A Harley.

35 records · Page 2Linked to original sources
PubMed1970

Pressure-flow studies in man: effect of atrial systole on left ventricular function.

In order to evaluate the effects of atrial contraction on left ventricular function, the pressure gradient technique was used to measure instantaneous aortic blood flow and pressure in nine patients, six having complete heart block and three having normal sinus rhythm. From these data both left ventricular stroke volume and stroke work were calculated. Ventricular rate was controlled by transvenous right ventricular pacing over a range of 50-158 beats/min. At each heart rate, beats which were not preceded by a P wave served as controls. The other beats were divided into six groups according to the duration of the preceding PR interval. The results indicated that stroke volume and stroke work were always affected similarly. In one patient the presence of a P wave did not alter the subsequent stroke volume significantly. In the other patients, beats preceded by P waves had stroke volumes greater than the controls. In general, there was no difference in stroke volume for beats preceded by a P wave having a PR interval within the range of 0.05-0.20 sec. As the PR interval lengthened beyond 0.20 sec stroke volume tended to decrease, especially at more rapid heart rates. The absolute increase in stroke volume after a beat preceded by a P wave (PR interval 0.05-0.20 sec) was quite variable among the patients. For a given patient the absolute increase in stroke volume was essentially independent of heart rate. The percentage change in stroke volume, however, was always greater as the heart rate increased. These data indicate that in most patients atrial systole is important in augmenting ventricular stroke volume and stroke work especially at high heart rates, but the magnitude of these effects are quite variable among patients.

Adult↗
PubMed1969

Pressure-flow studies in man. An evaluation of the duration of the phases of systole.

This study was designed to assess the independent effects of stroke volume and heart rate on the phases of systole and other selected hemodynamic parameters. By means of the pressure gradient technique instantaneous blood pressure and flow were recorded in the ascending aorta at fixed ventricular rates in five patients with complete heart block and in four patients with atrio-ventricular dissociation induced by ventricular pacing. Because of the variable contribution of atrial systole to ventricular filling, a wide range of stroke volumes were observed at each heart rate. The results indicate that the duration of ejection bears a close direct linear relationship to stroke volume while heart rate has only a weak but independent relation. On the other hand, the duration of total systole is related chiefly to the heart rate but stroke volume exerts an important independent effect. In a given patient, both duration of ejection and pulse pressure reflect changes of stroke volume and the product of the duration of ejection and the pulse pressure shows a good correlation with the stroke volume.

Adult↗
PubMed1968

Pressure-flow studies in man during atrial fibrillation.

In 13 patients who had atrial fibrillation the ascending aortic pressure-flow relationships were measured by the pressure gradient technique. Both the pressure and flow curves were similar in contour to ones previously obtained by this method. From these recordings, relationships between the phases of systole, the ventricular filling time, and various derived parameters of pressure and flow such as the pulse pressure, stroke volume, peak flow, stroke work, and peak power were evaluated. For stroke volumes greater than 15 cm(3) there was little change in the duration of systole in an individual patient. In each patient both the preejection period and the duration of ejection showed a good correlation with stroke volume, peak flow, stroke work, and peak power. When data from all patients were examined, the relationship between stroke volume and duration of ejection was found to be curvilinear and had an overall correlation of r=0.91. There was marked variation from patient to patient in duration of both the preejection period and systole. Similar correlations between the phases of systole were noted with peak flow, peak power, and stroke work. A positive but mediocre correlation was found between the previous RR interval (an index of ventricular filling time) and the subsequent stroke volume. The correlation, in six patients, between two previous RR intervals and stroke volume was considerably better. The relationship between the pulse pressure and stroke volume was reasonably close except in one patient; however, the group correlation was poor due to differences between individuals.

Adult↗