Systolic anterior motion of the tricuspid valve in idiopathic hypertrophic subaortic stenosis.

A 37 year man with combined subpulmonic and subaortic idiopathic hypertrophic stenosis proved by cardiac catheterization had typical echocardiographic findings of idiopathic hypertropic subaortic stenosis (IHSS) and systolic anterior motion of the anterior leaflet of the tricuspid valve. This motion of the tricuspid valve may relate to the subpulmonic infundibular gradient in the same way that the systolic anterior motion of the anterior mitral leaflet relates to the subaortic left ventricular gradient in patients with IHSS.

Correlations of electrocardiography and echocardiography in determination of left ventricular wall thickness: Study of apparently normal subjects.

To examine the usefulness of the surface electrocardiogram in predicting left ventricular wall thickness as determined with echocardiography, standard echocardiograms, electrocardiograms and Frank lead vectorcardiograms were obtained in 30 volunteers. End-diastolic thickness of the interventricular septum and free posterior wall was measured from the echocardiogram and compared with the sum of the S wave in lead V1 plus the R wave in lead V6 (VS1+R6) and the magnitude of the Frank lead vector (Vf), a scalar dunction obtained from a simple analog device. The maximum of Vf, the summated vector (Vf), was highly correlated with VS1+R6 (r=0.84). There was significant correlation between the summated vector and VS1+R6 and the thickness of the interventricular septum (IVS) (r=0.73 and 0.66, respectively). The best least mean square fit for the population was Vf=1.7 IVS-0.39. There was no significant correlation between these variables and the end-diastolic thickness of the posterior wall. Volunteers who were athletically inclined or were joggers tended to have larger summated vector values and evidence of symmetric or asymmetric left ventricular hypertrophy in the echocardiogram. It therefore appears that the thickness of the interventricular septum has a greater influence on the summated vector and VS1+R6 that the echocardiographically assessed thickness of the free posterior wall of the left ventricle. The implications of these findings in the light of recent reports about the incidence of echocardiographically diagnosed left ventricular hypertrophy are discussed.

Paradoxical motion of the interventricular septum with right ventricular dilatation in the absence of shunting: report of two cases.

A history, heart murmur, electrocardiogram and chest X-ray film suggesting an atrial septal defect associated with an echocardiogram revealing paradoxical motion of the interventricular septum with a dilated right ventricle may be considered indicative of a secundum or primum defect in a young adult or child. Two patients who fulfill all these criteria and had the presumptive diagnosis of an atrial septal defect were found at cardiac catheterization to have no demonstrable left to right shunt or other significant abnormality. The results of standard T-M mode echocardiograms were verified with B scan ultrasonograms. These cases may represent an early stage in the development of a cardiomyopathy. There is no echocardiogram pathognomonic of an atrial septal defect, and patients whose history and echocardiogram suggest this defect should have further diagnostic evaluation including technetium scan or cardiac catheterization.

Isotonic relaxation in cardiac muscle.

The force-velocity-length determinants of isotonic relaxation were studied in 12 cat papillary muscles. Isotonic relaxation velocity (VL) was found to be a function of total load (preload + afterload), with peak VL increasing to a maximum at loads approximately .3 to .4 Po(L') (Po(L') defined as maximum isometric force developed during a twitch at the experimental length) and falling with increasing loads. Initial muscle length (ML) had no effect on the peak VL with constant load. Increasing the initial length at which isotonic relaxation occurred (LL) decreased peak VL but did not alter the unique length-velocity trajectory at constant load. This unique length-velocity trajectory occurred, despite a wide variation in time during the contraction when peak VL was measured. Increasing Ca++ from 2.5 to 7.5 mM increased peak VL (1.73 +/- .16 to 2.32 +/- .20 ML/s) and shifted the entire length-velocity trajectory toward higher velocities of lengthening. The addition of 10 mM caffeine increased peak VL also (1.67 +/- .18 to 2.54 +/- .20 ML/s) and had a similar effect on the length-velocity trajectory during lengthening as Ca++. Both increased Ca++ and caffeine (10 mM) augmented the maximum VL measured on addition of load.

The dynamic properties of mammalian skeletal muscle.

The dynamic characteristics of the rat gracilis anticus muscle at 17.5 degrees C have been determined by isotonic and isometric loading. For a fixed initial length these characteristics were represented either as a family of length-velocity phase trajectories at various isotonic afterloads or as a series of force-velocity curves at different lengths. An alternate method of viewing these data, the length-external load-velocity phase space, was also generated. When the muscle was allowed to shorten from different initial lengths, the velocity of shortening achieved at a given length was lower for longer initial lengths. The amount of departure was also dependent upon the isotonic load, the greater the load the greater the departure. The departures were not caused by changes in the elastic elements of the muscle or fatigue in the ordinary sense. When the behavior of the muscle was investigated at different frequencies of stimulation, the shortening velocity was a function of the number of stimulating pulses received by the muscle at a given frequency. The shortening velocity of the rat gracilis anticus muscle is, therefore, not only a function of load and length, but also of an additional variable related to the time elapsed from onset of stimulation.

The active state of mammalian skeletal muscle.

A new technique is proposed for computing the active state of striated muscle, based on the three component model of Fenn and Marsh (8) and of Hill (7). The method permits calculation of the time course of the active state from its peak to the time at which maximum isometric twitch tension is reached. The intormation required for the calculation can be obtained from a single muscle without moving it from its mount in the lever system. The time course of the active state proved to be a function of the length of the muscle. This length dependency led to the predictions that (a) the length at which maximum force is developed during tetanic stimulation is different from that at which it is developed during a twitch, and (b) the tetanus-twitch tension ratio is a function of length. Both predictions were verified in a series of experiments on the rat gracilis anticus muscle at 17.5 degrees C.