Hemodynamic and pharmacologic influences on the left ventricular echo dimension-apex cardiogram loop in dogs.

Study of left ventricular pressure-volume relations has been limited by technical problems associated with left ventricular catheterization and angiography. A new approach using simultaneous recording of calibrated left ventricular apex cardiograms and echocardiographic M-mode dimensions was used to observe anesthetized dogs. The effect of various alterations in preload, afterload, and the inotropic state of the left ventricle on echo dimension-calibrated apex cardiogram plots sampled at 0.01 sec intervals was studied to test the method, and to clarify some of the determinants of the area of the loop. These areas were calculated in cm2 and the values of M-mode echo dimension-calibrated apex cardiogram loops and M-mode echo dimension-left ventricular pressure loops were similar in form and magnitude, and standard deviations under various hemodynamic interventions. Moreover, the impedance field, effective stroke field, and filing field were divided by the total surface of the loops. Whereas, alteration in afterload changed the impedance field, variation in preload especially affected the filling field; inotropic background was reflected in the effective stroke field. It is concluded that the value of both M-mode echocardiography and calibrated apex cardiography is enhanced by a combination of the two methods, and opens the possibility of a fresh approach to the noninvasive study of cardiac performance.

Influence of acute hemodynamic changes on the peak velocity of contractile element shortening and maximum velocity obtained by the calibrated apex cardiography in dogs.

The effect of various alterations in preload, afterload and inotropic state of the left ventricle on the noninvasive peak velocity of contractile element shortening (Vpm) and maximum velocity of contractile element shortening (Vmax) was studied in the anesthetized dogs in an attempt to test the methods and clarify some of the determinants of these parameters. Calibrated displacement left apex cardiogram obtained with time constant 3 sec and calibrated first derivative of apex cardiogram were recorded simultaneously with left ventricular pressure and its first derivative, electrocardiogram and phonocardiogram. The values of Vpm obtained from catheterization and calibrated apex cardiography were similar in magnitude and standard deviations under various hemodynamic interventions. A highly significant relation was found between these invasive and noninvasive parameters of myocardial contractility. Both Vpm and Vmax were elevated during the administrations of isoprenaline and strophanthin, where only Vpm showed a decrease after extreme volume or pressure load. In conclusion, the results from this study suggest that Vpm and Vmax of the calibrated apex cardiography are a reliable noninvasive tool for assessing left ventricular function; furthermore, Vpm is relatively load independent, whereas Vmax is virtually unchanged over a broad range of loading conditions.

Clinical value of calibrated and differentiated displacement apexcardiography in ischemic heart disease.

The calibrated left apexcardiogram with time constant 4 s and its first derivative (dA/dt) has been evaluated in 62 patients with ischemic heart disease and in 50 normal subjects. The normalized positive peak of dA/dt (max dA/dt/Ad), the peak velocity of contractile element shortening (Vpm), the normalized negative peak of dA/dt (min dA/dt/Ar), and the time constant of myocardial relaxation T as well as the time interval from R wave of the electrocardiogram to the peak positive dA/dt (R-max dA/dt) and the total apexcardiographic relaxation time interval divided to mean arterial pressure (TRI) were measured. In patients with ischemic heart disease we found a decrease of max dA/dt/Ad, Vpm, min dA/dt/Ar and an elongation of T, R-max dA/dt, and TRI, when compared to controls. Various indexes for myocardial contraction and relaxation were calculated in 21 of the patients who underwent left ventricular catheterization and biplane angiography. These parameters were used as dependent variables in the multiple regression analysis. Apexcardiographic indexes were used as independent variables. The indexes Vpm, max dA/dt/Ad, min dA/dt/Ar, and T were significantly correlated with all analogous invasive indexes. It is concluded that calibrated and differentiated apexcardiography provides useful information on left ventricular contraction and relaxation.

Influence of acute hemodynamic changes on the negative peak of the first derivative of apex cardiogram during ventricular relaxation in dogs.

The effect of various alterations in the preload, the afterload and the inotropic state of the left ventricle on the first derivative of apex cardiogram (dA/dt) was studied in 9 anesthetized dogs to clarify some of the determinants of the negative peak of dA/dt and isovolumic relaxation time. The first derivative of the apex cardiogram was recorded simultaneously with the left (ventricular pressure, conventional left apex cardiogram, first derivative of left ventricular pressure (dP/dt), electrocardiogram and phonocardiogram. Both dA/dt and dP/dt curves were similar in contour and occurred nearly simultaneously. This close relationship was preserved during various acute haemodynamic changes. The maximum negative dA/dt and the isovolumic relaxation period was closely related to the level of afterload. Large rapid augmentation of mean aortic pressure resulted in a significant increase in the negative dA/dt and shortening of the isovolumetric relaxation time, where reduction of afterload had an opposite effect. Isoprenaline acutely augmented minimum dA/dt. It is concluded that measurement of negative peak dA/dt under some conditions is a reliable noninvasive technique for assessing myocardial relaxation.

Influence of acute hemodynamic changes on the negative peak of the first derivative of apex cardiogram during ventricular relaxation in dogs.

The effect of various alterations in preload, afterload and inotropic state of the left ventricle on the first derivative of apex cardiogram (dA/dt) was studied in the anesthetized dogs, in an attempt to clarify some of the determinants of the negative peak of dA/dt and isovolumetric relaxation time. First derivative of apex cardiogram was recorded simultaneously with left ventricular pressure, conventional left apex cardiogram, first derivative of left ventricular pressure, electrocardiogram and phonocardiogram. Both dA/dt and dP/dt curves represent similarity in contour and were found to occur nearly simultaneously. This close relationship was preserved during various acutely hemodynamic changes. Maximum negative dA/dt and isovolumic relaxation period was closely related to the level of afterload. Large rapid augmentation of mean aortic pressure did results in statistically significant increase of negative dA/dt and shortening of isovolumic relaxation time, where reduction of after load had an opposite effect. Another interventions, which acutely augment min dA/dt was nitroprusside and isoprenalin. It is concluded, that negative peak dA/dt under some conditions provides a reliable noninvasive index for assessing myocardial relaxation.

Evaluation of contractile state of the left ventricle from the peak of the first derivative of the apexcardiogram.

Simultaneous records of the electrocardiogram, phonocardiogram, apexcardiogram (ACG), and the first derivative of the apexcardiogram (dA/dt) were obtained in 50 normal subjects and in 38 patients with ischemic heart disease. This allowed us to measure the ratio of peak dA/dt to total amplitude of the first derivative in percent and the interval from electrical stimulation to peak dA/dt (R to peak dA/dt). In 16 additional normal subjects the effects of pharmacological agents with positive and negative inotropic action were studied with the above parameters. During isoprenaline infusion the ratio of peak to total amplitude dA/dt was increased and the interval R to peak dA/dt was shortened, while after propranolol the ratio of peak dA/dt diminished and the interval R to peak dA/dt showed elongation. In normal subjects the ratio of peak dA/dt averaged 48 +/- 14% and it is significantly lower in patients with ischemic heart disease (32 +/- 13%, p < 0.001). In controls the interval R to peak dA/dt was 73 +/- 15 msec., whereas in ischemic heart disease it showed elongation (121 +/- 15 msec., p < 0.01). It is concluded that the ratio peak dA/dt and the interval R to peak dA/dt, expressing noninvasively the rate of pressure changes and the duration of the development of maximum tension during isovolumic contraction, provide useful information on left ventricular function.

The use of the first derivative of apexcardiogram for determining some systolic and diastolic time intervals in ischaemic heart disease.

In 50 normal subjects and in 63 patients with ischaemic heart disease, the left ventricular apexcardiogram with its first derivative (dA/dt), electrocardiogram and phonocardiogram were recorded simultaneously. This allowed to measure four systolic and diastolic time intervals using the first derivative of apexcardiogram. In patients with ischaemic heart disease in increase of the interval R to peak dA/dt, systolic upstoke time of dA/dt, and early apexcardiographic relaxation time (the time from the onset of the aortic component of the second heart sound in the phonocardiogram to the negative peak of the dA/dt) was established. It is concluded that dA/dt is a suitable technique for more exact non-invasive determination of some time intervals than conventional apexcardiogram in ischaemic heart disease.

Apex-carotis diagram as related to systolic and diastolic time intervals in mitral valve prolapse syndrome.

The electrocardiogram, phonocardiogram, carotid pulse tracing and apexcardiogram were simultaneously obtained in 25 patients with mitral valve prolapse syndrome and in 62 normal subjects. This allowed us to measure systolic and diastolic time intervals and to construct the apexcarotis diagram (ACD), a new mechanocardiographic method which integrated the catotid pulse tracing and the apexcardiogram in an orthogonal coordinate system. In mitral valve prolapse syndrome, the ACD showed curve of the segment of slow ventricular ejection (S-AC) to the right, and a decrease of the field of ventricular ejection. The measurement of time intervals gave statistically significant information on Q-I and A2-OS intervals.

Apex-carotis diagram in ischemic heart disease with angina pectoris.

The apex-carotis diagram (ACD) is a new mechanocardiographic, non-invasive method consisting of integration of the carotidogram and left apex-cardiogram synchronously recorded. The values of the amplitude height of these curves every 0.02 sec are transferred to an orthogonal coordinate system, and the points are then connected in chronological order, thus obtaining the ACD. In ischemic heart disease with angina pectoris, the ACD showed a decrease of the areas of ventricular filling and ventricular ejection, and an increase of the diastolic subsegment A. In 18 of the examined patients the decrease of the ventricular ejection area showed a significant negative correlation with the increase of left ventricular ejection time.

Apex-carotid diagram in systolic click-late systolic murmur syndrome.

A new non-invasive method based on mechanographic cycles has been developed for the study of heart function. It integrates synchronously recorded indirect carotid tracing and left apex cardiogram into an apex-carotid diagram. In 25 patients with systolic click-late systolic murmur syndrome, the diagram showed an elongation with a curvature of the segment of slow ventricular ejection to the right and a decrease in the area of ventricular ejection. It is concluded that apex-carotid diagram is an additional tool in diagnosis of the mitral valve prolapse syndrome.