The first heart sound in normal and pathological conditions.

Abstract

SUMMARYConsiderations of the physical basis of cardiac contraction and sound generation explain the mechanism of the first sound. Older theories examining this sound as the result of valve closure or stiffening are refuted.It has been demonstrated that the normal first sound originates in the left ventricle alone and that accelerations and decelerations, "timed" by mitral and aortic valves events, are its cause. Three components have been recognized in the first sound: a occurs when the left ventricular wall and septum have reached a certain tension; b when the aortic valve opens; c when the peak of the aortic pulse has been reached.The ventricular septum is an integral and essential part of the left ventricle. In left bundle branch block, abnormal activation of the septum transforms this into a passive structure resulting in a slower rise of left ventricular pressure and a longer isovolumic period. This causes a small and delayed first sound, whose components, however, are still separated by normal intervals.In right bundle branch block, the first sound has a normal amplitude and its components are separated by normal intervals.If there is a larger late component, it is a c component, similar to that of normal elderly subjects. A larger c component may also be found in atrial septal defect. The cannon sound of AV block is caused by more rapid deceleration due to higher atrial pressure at the onset of ventricular contraction resulting in intense vibrations. The first sound of arrhythmias varies in the different conditions and even in different subjects, due to the effect of several variable factors. Elevated left atrial pressure, stiffening of the mitral valve in mitral stenosis, causes a slow onset and a more rapid rise of LV pressure. This results in a delayed, but larger, first sound. The action of catecholamines on the myocardium dramatically increases the first sound. The latter

Predicting the Origin of Ventricular Arrhythmia Using Acoustic Cardiography

“…With RBBB the S1 tends to be widely spitted with a preserved amplitude and a larger late component. as shown in a previous study 7 , 8 . In this study, RBBB morphology PVC (LV origin) was characterized by increased S1 duration and complexity, which were compatible with previous findings.…”

“… 7 studied 20 right bundle branch block (RBBB) subjects and 67 normal subjects with simultaneous echocardiogram of valves, electrocardiogram, and phonocardiogram. Wide splitting of the S1 was observed in RBBB subjects 7 , 8 . These studies demonstrated the wavefront of ventricular myocardial activation affect the timing of valvular closure, which could be detected and quantified by well-designed acoustic cardiography device.…”

Estimation of left ventricular function using a novel acoustic‐based device

“…Multiple acoustic variables were found to be associated with LVEF. (i) E1, the acoustic correlate of the mitral component of the first heart sound that is related to LV contraction [6], was positively associated with LVEF. (ii) Diastolic acoustic signals (ED) were negatively associated with LVEF.…”

A tribute to Italian physiologists of Jewish descent evicted during the persecution ordered by the Fascist Regime in 1938

“…Also included was Aldo A. Luisada , a distinguished cardiologist from Ferrara who left Italy in 1939 to become a faculty member at the medical school of the University of Chicago. Luisada, founder and first president of the Laennec Society for Cardiovascular Sound, is remembered for his researches in phonocardiography to monitor cardiac performance and on the mechanisms of heart sound generation and cardiac contraction (40,41).…”