Aldo A. Luisada

The phases of the cardiac cycle

Abstract The events of the cardiac cycle are re-evaluated on the basis of newer ideas of inertial states, compliance, and similar hemodynamic principles by the use of more precise, modern recording equipment. While these events generally agree with classic schemes, certain discrepancies which tend to cause inaccurate measurement are presented. In particular, the intervals existing between A-V valve closure and the onset of the first sound, and between semilunar valve closure and the onset of the second sound are discussed. Causes of prolongation of the intervals between valve closures and sound events are briefly discussed. The possibility of inaccurate measurements by noninvasive techniques is further considered.

New studies on the first heart sound

Abstract Experimental investigators exclude “valve closure” as a cause of the first heart sound and recognize “valve tension” only as a minor contributing factor. They accept the exclusive importance of left ventricular events in causing the first heart sound and attribute the vibrations of this sound to accelerations and decelerations of the left ventricular-aortic system plus the blood it contains. Recent studies demonstrate that the second component of the first heart sound coincides with the opening of the aortic valve and relate it to the dynamic changes resulting from this event. They show that the vibrations of this second component are larger and have a higher frequency in the outflow tract of the left ventricle in comparison with the main chamber. Other studies have compared the amplitude of the first sound recorded within the left ventricle with that recorded either on the skin or over intermediate layers. The conclusion is that an average loss of 30 db is present. However, this loss is greater for low frequency than for high frequency vibrations. Changes of the first sound are discussed. They occur in experimental or clinical conditions as a result of changes in the power or rapidity of contraction of the left ventricle. Usually a change in frequency is noted on auscultation as a change in intensity. Modification of the volume of blood (dilatation) or thickness of the wall (hypertrophy) can also modify the first heart sound.

The second heart sound in normal and abnormal conditions

Abstract Changes of the second heart sound are caused by shifting in position and changes in magnitude of the aortic or pulmonary component, or both. Differences in the magnitude of each component are primarily related to changes in pressure but are also affected by structural changes of the vascular walls. Positional changes are influenced by the time of closure of the respective valve (in turn related to time of ventricular activation, duration of systole and pressure gradient across the valve) and by the interval between valve closure and vascular vibration at the time of rebound. Normal splitting is present during inspiration and decreases or disappears during expiration. Marked differences related to age are present. Three abnormalities may occur: wide splitting during inspiration that persists during expiration; single second sound; and reverse splitting, either occurring only during, or accentuated by, expiration (occasionally also occurring during inspiration).

Mechanism of changes in the second heart sound in aortic stenosis.

Abstract The dynamic correlates of the second heart sound were studied by right and left heart catheterization in 15 subjects with pure aortic valve stenosis and in 6 subjects who had no cardiac lesion. The duration of left ventricular systole is not, as previously thought, prolonged in aortic stenosis. Left ventricular ejection is prolonged because of late closure of the aortic valve related to the higher level of left ventricular pressure compared to that of aortic pressure (pressure gradient). In addition, there is a delay in the time of occurrence of the aortic incisura in relation to valve closure. The sum of both these delays (aortic valve closure in relation to end of systole; incisura in relation to valve closure) explains the delay of the aortic component of the second heart sound, which occurs either at the time of the pulmonary component or after it (reverse splitting). The changes of the second heart sound were found to be grossly proportional to the magnitude of the pressure gradient across the aortic valve and, therefore, significant in evaluating the severity of the lesion.

Mechanisms of Intracisternal Veratrine Pulmonary Edema

Pulmonary edema (PE) caused by central nerve irritation is a known clinical condition. Our study was undertaken in order to investigate the mechanism of this condition. PE was induced in 29 dogs by a standard technique of intradsteraal veratrine. The standard method was studied in ten dogs. Extreme elevation of left ventricular systolic pressure (LVSP) occurred, followed by elevation of the left ventricular diastolic pressure (LVEDP) to a very high level, even reaching 80 mm Hg. Extreme increase of the dp/dt was also noted. PE was severe. In five dogs, the procedure was performed after spinal transection at T-4. In these animals, LYSP rose less, LVEDP rose moderately, and pulmonary edema was minimal. In 13 dogs, the procedure was performed after bilateral stellectomy and/or vagotomy. LYSP rose as in standard experiments, LYEDP rose moderately, and PE was minimal or absent These results are evidence that CNS irritation is followed, not only by vasoconstriction, increased venous return, and cardiac overloading, hut also by decreased compliance of the left ventricular wall. Spinal transection decreases ventricular overload by preventing peripheral constriction and adrenal catecholamine secretion. SteDectomy prevents changes of left ventricular compliance mediated through cardiac nerves without affecting those caused by circulating catecholamines.

Changes of cardiac output caused by aging: an impedance cardiographic study.

The various parameters of cardiac output were studied in 132 healthy subjects from 20 to 89 years of age by impedance cardiography. This noninvasive method supplied data that were similar to those found by others by dye dilution methods. All parameters of cardiac output decrease with age. However, we found a difference between the two sexes in the rate of decrease of the cardiac index: women had a more marked drop at an earlier age and then a steady course, while men had a progressive decrease from the youngest to the oldest group.

Correlates of the Echocardiographic Waves of the Mitral Valve in Normal Subjects of Various Ages

A cardiographic study was performed on 71 subjects including 14 children, 42 young and middle‐aged adults, and 15 old persons without evidence of heart disease. The echocardiogram of the mitral valve was recorded in the A mode by an analog method and was compared with the electrocardiogram, phonocardiogram, apex cardiogram, and carotid and jugular tracings, simultaneously obtained. The intervals between the various waves recorded by these methods were measured and the results were compared with those reported in the literature. A comparison of the duration of the intervals in the various age groups showed statistically significant differences. In particular, the intervals between the second heart sound and the peak of the E‐wave and the E‐F interval in the echogram were longer in adults than in children and also longer in old persons than in younger adults. This important age difference should always be taken into account before attributing any echocardiographic deviations to disease.

Incidence of Murmurs in the Aging Heart

ABSTRACT: One hundred patients aged 60 or older were studied clinically after excluding those with cardiac enlargement, definite valvular lesions or electrocardiographic (ECG) evidence of left ventricular hypertrophy. In 30 of the 100 patients a significant systolic murmur was heard on auscultation. Phonocardiograms (PCGs), mitral echograms and pulse tracings were obtained in 28 of these 30 patients (2 had died meanwhile), and the ECGs and chest roentgenograms were reviewed. In 23 PCG patients there was an early or midsystolic murmur, best recorded at the base of the heart and often transmitted to the apex. Mitral valve echograms and carotid and jugular pulse tracings were normal in all cases. Chest roentgenograms revealed aortic enlargement in 83 percent of the 23 patients. In the elderly with no evidence of organic heart disease, a basal systolic murmur is probably an aortic flow phenomenon caused by either moderate aortic dilatation or minimal fibrotic fusion of one or more commissures of the aortic valve.

The second heart sound in atrial septal defect

Abstract Ventricular and arterial pressure tracings, electrocardiograms and phonocardiograms were studied in 4 normal subjects and 52 patients with atrial septal defect. After excluding cases in which complicating factors were involved, 10 cases of secundum type and 3 cases of primum type were studied in detail. Contrary to previously held beliefs, right ventricular systole is not longer than left ventricular systole in these patients. Therefore, pulmonary valve closure still occurs very close to aortic valve closure, as in normal subjects. However, the incisuras of the large arteries are more widely separated than in normal subjects. The explanation for the wide splitting of the second heart sound is based on recent work that attributes the sound components to vibrations of the blood, valves and walls of the large arteries at the time of the aortic and pulmonary arterial rebounds. Patients with atrial septal defect have a dilated pulmonary artery. This causes a slower reaction of the wall and a later occurrence of both the pulmonary incisura and the pulmonary component of the second heart sound.

Durations and intervals of normal heart sounds in man

Abstract The duration of the heart sounds, the Q-I interval, and the intervals between sounds, as well as between their components, were studied in 23 normal subjects. The study was made with new calibrated equipment which records displacement, velocity, and acceleration tracings, and which contains provisions for the application of different filters. The data obtained will serve for evaluation of those found in clinical cases.