First Derivative Of Apex Cardiogram Research Articles

Influence of acute hemodynamic changes on the normalized negative peak of the first derivative of the apex cardiogram and time constant of ventricular relaxation in dogs.

The effect of various alterations in preload, afterload and inotropic state of the left ventricle on two non-invasive indices of myocardial relaxation was studied in anesthetized dogs, in an attempt to clarify some of the determinants of myocardial relaxation. The first derivative of the displacement left apex cardiogram (dA/dt), the apex cardiogram, left ventricular pressure, the first derivative of left ventricular pressure, electrocardiogram and phonocardiogram were recorded simultaneously. The following mechanocardiographic parameters of myocardial relaxation were investigated: (1) normalized negative peak of dA/dt for simultaneous isovolumic apex cardiographic amplitude (min dA/dt/Ar). and (2) time constant of myocardial relaxation T. The non-invasive time constant was derived from a logarithmic isovolumic calibrated apex cardiographic amplitude v. time plot subsequent to min dA/dt. The indices min dA/dt/Ar and T compared with analogue parameters of left ventricular catheterization (min dP/dt/Pr and T) showed similarity in magnitude and standard deviation during various acute hemodynamic interventions. The min dA/dt/Ar was related to the level of afterload; furthermore isoprenaline accelerated relaxation as determined by the two investigated indices. During the various hemodynamic changes a high correlation existed between invasive and non-invasive indices. The results presented indicate that the apexcardiographic time constant of myocardial relaxation may be a reliable index for ventricular relaxation since it is independent of pre- and afterload, whereas min dA/dt/Ar are load-dependent.

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.

The use of the first derivative of apex cardiogram and echocardiographic dimensions for assessing left ventricular relaxation and mean velocity of circumferential fibre lengthening in cardiomyopathy.

Eleven patients with hypertrophic obstructive cardiomyopathy (HOCM) and nine patients with congestive cardiomyopathy (COCM) were studied to determine the usefulness of relaxation time and mean velocity of circumferential fibre lengthening (VCFJ obtained from the first derivative of apex cardiogram and echocardiographic left ventricular dimensions. Twenty-two normal patients were ± investigated by echo and apex cardiography and served as controls. In HOCM both early apex cardiographic relaxation time interval (ERT) and total apex cardiographic relaxation time interval (TRT) were increased (ERT: 16 ±9 ms v. 5 ± 4 ms in controls, P<O.001; TRT: 127 ± 22 ms v. 94 ± 21 ms in controls, P<O.01) and VCFL was decreased (0.87 ± O.08 circs v. 1.21± O.09 circ/s for controls, P<0.02). In COCM both ERT and TRT were diminished (ERT: 1 ± 3.5 ms v.7±4 ms in controls, P<O001; TRT: 53 ± 14 ms v. 94 ± 21 ms for controls, P<O.01) and VCFL was decreased (0.69 ± 0.08 circ/s v. 1.21 ±0.09 circ/s in controls, P<O.01). There was a significant correlation between min dp/dt determined at catheterization and both ERT (r = O.86) and TRT (r=O.81). These findings indicate that alterations in relaxation and mean velocity of circumferential fibre a lengthening take place in cardiomyopathy and they may be detected non-invasively by the first derivative of the apex cardiogram and the left ventricular echocardiogram.

Assessment of left ventricular contraction and relaxation by systolic and diastolic time intervals measured from the first derivative of apexcardiogram in cardiomyopathy.

To determine the usefulness of the time intervals obtained from the first derivative of apexcardiogram (dA/dt) in assessing contraction and relaxation in cardiomyopathy, 11 patients with hypertrophic obstructive cardiomyopathy (HOCM) and 9 patients with congestive cardiomyopathy (COCM) with hemodynamically and angiographically documented diagnosis were studied. As a control group 50 normal subjects were used. Since contraction and relaxation is dependent on preload and afterload, the time interval from R wave of electrocardiogram to the positive peak of dA/dt (R to dA/dt) and 2 relaxation parameters derived from negative peak dA/dt, early relaxation index (ERI) and total relaxation index (TRI) were investigated. In HOCM the R to dA/dt were shortened (55 +/- 13 msec versus 76 +/- 14 msec in controls, P less than 0.01) and both ERI and TRI were augmented (ERI: 12.5 +/- 9 versus 4.3 +/- 5 in controls, p less than 0.001; TRI: 147 +/- 29 versus 70 +/- 18 in controls, p less than 0.02). In COCM the R to dA/dt were elongated (124 +/- 14 msec versus 76 +/- 14 msec in controls, P less than 09.001) and both ERI and TRI were decreased (ERI: 2.1 +/- 4 versus 4.3 +/- 5 in controls, p less than 0.005; TRI: 41 +/- 17 versus 70 +/- 18 in controls, p less than 0.002)., Significant correlation between these indices and some internal parameters of myocardial performance were observed. These findings indicate that systolic and diastolic time intervals measured from the first derivative of apexcardiogram may be used as a reliable indices for evaluation of contraction and relaxation independently of preload and afterload.