Presystolic murmur in atrial fibrillation: fact or fiction?

Age and sex differences in cardiovascular reactivity to adrenergic agonists, mental stress and isometric exercise in normal subjects

Dose-response curves for intravenous bolus injections of isoprenaline were carried out in 40 normal subjects, in four groups of 10 comprising young and middle-aged males and females. The isoprenaline dose required to raise the heart rate by 50 beats/min, the CD50 (chronotropic dose 50 beats/min), was calculated individually and taken as a measure of the beta-adrenergic responsiveness. Females had significantly higher sensitivity to isoprenaline than males, i.e. lower CD50 values (95% confidence interval 0.07-0.11 versus 0.12-0.17 micrograms/kg body weight, p less than 0.001), and young subjects had higher sensitivity than middle-aged subjects (95% confidence interval for CD50 0.07-0.10 versus 0.12-0.18 microgram/kg body weight, p less than 0.001). Dose-response curves were also carried out for intravenous prenalterol, a partial beta 1-adrenergic agonist. The maximal heart-rate response to prenalterol (delta HRP) showed a significant inverse linear relationship with the CD50 (delta HRP = 44.8-0.11 x CD50, r = -0.53, rs = -0.69, p less than 0.001). A mental stress programme and isometric exercise gave significant increases in heart rate and blood pressure for all groups, but there was no significant relationship between the CD50 and the heart-rate response. By applying a theoretical model, developed by Kenakin and Beek [13], to the isoprenaline-prenalterol data, it is suggested that the observed age and sex differences in beta-adrenergic responsiveness are caused by a tissue-related difference in the stimulus-response mechanism.

Age related decline in aluminum-activated human platelet adenylate cyclase: post-receptor changes in cyclic AMP second messenger signal amplification in normal aging and dementia of the Alzheimer type

Low, micromolar concentrations of aluminum (in the presence of NaF) were shown to strongly activate human platelet adenylate cyclase and provided a useful probe for evaluating cyclic AMP second messenger function distal to the receptor: The effect of normal aging and disease state on second messenger activity in man was studied by measurements of the aluminum-activated enzyme. A significant decline in aluminum-stimulated platelet adenylate cyclase activity in older, healthy subjects was observed. An age-associated decline in NaF-stimulated cyclic AMP synthesis was also demonstrated for normal, non-demented subjects. These findings suggest an age-associated lesion at the level of the guanine nucleotide regulatory protein/catalytic subunit of the adenylate cyclase complex. However, for patients with Alzheimer's disease no such decline in platelet adenylate cyclase activity was detected, and increased sensitivity to both aluminum and NaF was demonstrated.

Noninvasive study of the presystolic component of the first heart sound in mitral stenosis

Echophonocardiography and pulsed Doppler echocardiography were performed in 30 patients with mitral stenosis (19 with atrial fibrillation and 11 with sinus rhythm) to investigate the genesis of the presystolic component or small apical vibrations preceding the first heart sound in mitral stenosis. In 27 patients, mitral valve closure preceded or coincided with tricuspid valve closure regardless of the preceding RR interval. Of three patients whose tricuspid valve closed prematurely, two had a prolonged PR interval. The soft apical vibrations, which were recorded during the final rapid closing motion of the mitral valve echogram (B-C slope), began with the upstroke of the apexcardiogram. During this event the pulsed Doppler echocardiogram revealed a deceleration in the velocity of mitral inflow. In two exceptional patients with a prolonged PR interval, this apical sound was separated from a presystolic rumble that occurred during an accelerated phase of mitral inflow or at the A wave of mitral valve echograms. In conclusion, the tricuspid valve is not a factor contributing to the genesis of the small apical vibrations preceding the first heart sound in mitral stenosis. These vibrations are caused by acceleration of left ventricular contraction and deceleration of mitral inflow in the presence of a stenotic valve.

Echophonocardiographic study of the initial low frequency component of the first heart sound

To investigate the genesis of the initial low frequency component of the first heart sound that precedes the high frequency vibrations associated with closure of the atrioventricular valves, echophonocardiograms of 36 persons were recorded. These included 10 normal subjects and 26 patients with various types of heart disease including mitral valve replacement. Electrocardiograms demonstrated normal sinus rhythm in 23 subjects, atrial fibrillation in 9, complete atrioventricular block in 2 and atrial flutter in 2. In the phonocardiogram, the low frequency component of the first heart sound followed the onset of the QRS complex and preceded the first high frequency component of this sound. The low frequency component occurred simultaneously with the beginning of the final fast closing movement of the mitral valve on the echocardiogram and was found both in normal rhythm and in arrhythmias. However, in arrhythmias its intensity varied on a beat to beat basis, being loudest after a short RR interval or when atrial systole occurred very close to the expected time of ventricular systole. In patients in whom apexcardiograms were recorded, the low frequency component was coincident with or very close to the onset of ventricular systole. It is concluded that the low frequency component of the first heart sound represents vibrations caused by contraction of the left ventricle and deceleration of antegrade blood flow across the mitral valve. Neither atrial contraction nor mitral valve tension is necessary for the production of this soft initial component.

Double diastolic murmur in mitral stenosis with atrial fibrillation and complete heart block

A double diastolic murmur was heard in a patient with mitral stenosis, atrial fibrillation, and complete heart block. Echo-phonocardiographic examination showed two separate opening and closing movements of the mitral valve in the same long diastole. A clear time relation was observed between the valve closing movements and the separate diastolic murmurs, giving support to the theory that the backward motion of the mitral valve against the forward blood flow through the valve is responsible for the production of these murmurs.

Non-invasive observations on initial low frequency vibrations of the first heart sound--correlation with the 'presystolic' murmur in mitral stenosis

The initial low frequency component of the first heart sound, 'M', has been studied in normal subjects, and in patients with vario-s prosthetic mitral valves and with mitral stenosis, using simultaneous low frequency phonocardiography, echocardiography, and apex cardiography. The techniques showed 'M' to have a constant morphology in preisovolumic systole. In mitral stenosis, 'M' and the preisovolumic 'presystolic' murmur appear to be the same phonocardiographic phenomenon. While 'M' was present in sinus rhythm, augmentation of this normal vibration occurred particularly during the short cycles of atrial fibrillation. Leaflet coaption and movement of the ventricular wall as detected echocardiographically do not appear to play a role in its pathogenesis but the sound could emanate from the ventricular wall as it tautens and decreases its compliance at the onset of systole.