Low-frequency pulsations (20 cycles a second or less) appearing on the surface of the chest over the region of the cardiac apex have been studied sporadically for many years, but recently they have attracted considerable attention Dimond, 1964;Tafur, Cohen, and Levine, 1964a;Coulshed and Epstein, 1963;Nixon and Wooler, 1963). These pulsations possess considerable amplitude in comparison with the higher frequency sound vibrations and generally can be recorded easily. Most observers would agree that motion of the left ventricle causes the major, if not the only, low-frequency deflections on the chest wall in this region; however, interpretation of the recordings has been hampered by lack of precise knowledge about how these vibrations correlate with hmmodynamic events within the left side of the heart.Benchimol and Dimond (1963) in their recent review of the apex cardiogram (ACG) indicated the relation between chest pulsations and intracardiac tracings, but their work was confined largely to the right heart, pulmonary capillary, and left atrial pressure curves. Others (Dimond, 1964;Tafur et al., 1964a;Coulshed and Epstein, 1963;Nixon and Wooler, 1963;Benchimol and Dimond, 1962) have correlated the ACG with left heart pressure dynamics, but these studies have been limited in number and require further elucidation. Animal studies have produced some additional information about the ACG (Benchimol and Dimond, 1963), but it is impossible to extrapolate human conditions from experience with animals, inasmuch as the intrathoracic relationships and chest contour are not necessarily comparable between species. The present study was undertaken, therefore, to ascertain the relation in humans between external chest pulsations and hemodynamic events recorded simultaneously in the left heart during cardiac catheterization.
SUBJECTS AND METHODSFifty-four patients undergoing left and right heart catheterization form the basis of this report. Catheterization in all instances was prompted by the usual clinical criteria, and patients were included in this study solely on the basis that technically satisfactory apex cardiograms could be made. Satisfactory tracings were most often impossible to obtain when right ventricular hypertrophy was present; unsuitability was evidenced by varying degrees of systolic retraction over the area normally occupied by the apex. All patients included in the study had typical left ventricular electrocardiographic QRS complexes overlying the apex (V4 to V6). This provided further evidence that the records obtained reflected left-sided cardiac events (Hartman, 1956).
