Alexander Harley

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.

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.

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.

Coronary artery disease and major conduction disturbances. A pathologic study designed to correlate vascular and conduction system abnormalities with electrocardiogram.

Abstract A technique for correlating vascular anatomy with conduction tissue structures in the human heart has been described. This technique was used to study eight selected cases of coronary artery disease who demonstrated major conduction disturbances by ECG. 1. The following conclusions are reached: 1. There is good correlation between histologic changes in the major pathways of the conduction system and demonstrable electrocardiographic abnormalities. 2. 2. There is poor correlation between specific vascular pathology and histologic changes in the major conduction pathways, except when related to fresh vascular occlusive disease. 3. 3. The development of collateral circulation in the upper interventricular septum is the one anatomic feature which appears to govern the relationship between vascular and conduction tissue pathology. 4. 4. The broad spectrum of pathologic processes in coronary artery disease associated with major conduction disturbances is felt to account for the marked variability in the clinical setting and course of these cases.

Evaluation of thoracic impedance plethysmography as an indicator of stroke volume in man.

The maximum negative first derivative of the systolic thoracic impedance change and duration of ejection were measured in eight patients with cardiomegaly, while stroke volume was computed continuously using the pressure gradient technique. Wide variations in heart rate and stroke volume were produced by atrial pacing and as pulsus alternans occurred spontaneously. Duration of ejection showed a close curvilinear relationship with stroke volume best expressed as a logarithmic function which was similar for all patients. A linear relationship existed between the maximum impedance derivative and stroke volume which was close in some patients but was poor or varied with heart rate in others. No independent characteristic could be found to predict in which patients the maximum impedance derivative reliably reflected changes in stroke volume. Wide variations in this relationship between individuals prevented its satisfactory description for all patients by any single equation. Computations employing the product of the maximum impedance derivative and duration of ejection did not reliably estimate absolute values for stroke volume and did not improve upon the simple relationship between duration of ejection and stroke volume.

Pressure Flow Studies in Patients Having a Pressor Response to the Valsalva Maneuver

Blood pressure and flow were measured in the ascending aorta by means of the pressure-gradient technique in five patients with congestive heart failure manifesting a pressor response to the Valsalva maneuver. Beat-to-beat changes in stroke volume, blood pressure, pulse pressure, peak blood flow, duration of systole, duration of ejection, and heart rate were calculated. Stroke volume and blood pressure rose with the onset of straining; blood pressure rose slightly further as stroke volume fell to below control levels at the end of the straining period. Pulse pressure, peak blood flow, and duration of ejection tended to follow stroke volume. Heart rate was unchanged throughout. All parameters returned toward control after release of the strain.

Computer Analysis of the Orthogonal Electrocardiogram and Vectorcardiogram in Mitral Stenosis

Orthogonal electrocardiograms (Frank lead system) from 191 patients with pure mitral stenosis (MS) were compared to electrocardiograms from 510 normal patients and 296 patients with pulmonary emphysema (PE). All patients with MS underwent right heart catheterization; 121 patients underwent both left and right heart catheterization. Three hundred and thirty electrocardiographic measurements were obtained from each record and tested for their ability to distinguish mitral stenosis from normal. Two sets of diagnostic discriminators were selected: (1) ECG measurements which can be easily obtained by hand and (2) measurements which performed best in multivariate analysis using linear discriminant functions. The patients with mitral stenosis were separated into three hemodynamic subgroups according to mean pulmonary artery pressure (PAP) (0-30, 31-40, and > 40 mm Hg). The ability of the selected measurements to recognize mitral stenosis increased as mean pulmonary artery pressure rose. The superiority of the multivariate technique, using nine measurements simultaneously, was readily demonstrated when compared to the hand measurements. At a constant level of 6% false positives, multivariate analysis allowed a 74% recognition rate of mitral stenosis compared to 44% with hand measurements.