Ventricular Ejection Rate Research Articles

The rate of change of left ventricular volume in man. I. Validation and peak systolic ejection rate in health and disease.

The rate of left ventricular volume change (dV/dt) is by definition left ventricular ejection rate during systole and filling rate during diastole, and in the absence of valvular regurgitation or intracardiac shunts, is equal to systolic aortic valve flow and diastolic mitral valve flow respectively. A computerized technique for the calculation of instantaneous left ventricular dV/dt from cineangiographically measured left ventricular volume is presented. Curve smoothing was accomplished by passing a second degree polynomial through nine consecutive volume points using the least squares technique. Validity of this technique was demonstrated by the high degree of correlation of systolic dV/dt with instantaneous ascending aortic blood velocity (flow) measured simultaneously with an electromagnetic catheter-tip velocity transducer in ten patients. Peak left ventricular systolic ejection rate (S dV/dt) was calculated from single plane cineangiographically measured left ventricular volumes in 113 adult patients and related to other measures of cardiovascular function. Mean S dV/dt for the group of 29 normal patients was 427 ± 129 cc per second and was not significantly different in patients with coronary artery disease (21), aortic stenosis (13), mitral stenosis (11), or cardiomyopathy (9), but was increased significantly in patients with valvular regurgitation (19). S dV/dt correlates poorly with the ejection fraction and with left ventricular end-diastolic pressure (LVEDP) and is not a reliable measure of left ventricular function. The primary determinant of S dV/dt appears to be total left ventricular stroke volume. When S dV/dt is divided by end-diastolic volume (EDV), the resultant S dV/dt/EDV correlates well with peak normalized circumferential fiber shortening rate ( r = 0.89, P < 0.01) and with ejection fraction ( r = 0.69, P < 0.01). The correlation coefficient of S dV/dt/DV with LVEDP was r = 0.36 ( P < 0.01) and with arterio-venous oxygen difference, r = 0.38 ( P < 0.01). Thus, S dV/dt/EDV appears to be a measure of ventricular function. S dV/dt occurs in midsystole in normal subjects and in patients with mitral regurgitation and is not delayed in patients with aortic stenosis. The three patients with idiopathic hypertrophic subaortic stenosis appeared to have characteristic changes in the left ventricular ejection rate curve with an increase in S dV/dt (and especially S dV/dt/EDV), with S dV/dt occurring earlier in systole than normal.

Left ventricular hypertrophy in coronary artery disease: A cardiomyopathy syndrome following myocardial infarction

Eighty-five patients with ventricular dysfunction due to coronary disease and to nonobstructive cardiomyopathy were studied by biplane angiocardiography (12/sec) to determine the extent of hypertrophy and the distinguishing features between primary myocardial and coronary disease. Patients with cardiomyopathy and equally severe dysfunction due to coronary disease had identical end-diastolic, end-systolic and stroke volume and work per square meter, stroke work per gram of ventricular mass, end-diastolic pressure, peak equatorial wall stress, ejection fraction, peak circumferential shortening velocity, peak ventricular ejection rate, peak external pump power, left ventricular mass and mass to diastolic volume ratio. Hypertrophy develops after myocardial infarction in proportion to ventricular dilatation and may result in a syndrome of massive hypertrophy, hypokinesis and congestive failure quantitatively identical to that found in primary cardiomyopathy except for etiology. Hypertrophy is associated with normalization of wall stress in both coronary and primary myocardial disease and is thus not dependent on the type of insult to the contractile mechanism.

Left ventricular function in systole and diastole in constrictive pericarditis

Left ventricular function was studied in systole and diastole in 30 patients with constrictive pericarditis. Left ventricular end-diastolic volume was used to divide the patients into three arbitrary groups: severe constriction (EDV < 25 ml./M. 2), moderate constriction (EDV 25 to 50 ml./M. 2), and mild constriction (EDV > 50 ml./M. 2). The patients had high ventricular diastolic and venous filling pressures (mean LVEDP = 23 ± 7 mm. Hg, mean RVEDP = 20 ± 7 mm. Hg). Measurements related to absolute fiber shortening (stroke index, stroke work index, and left ventricular ejection rate) were reduced and linearly related to the degree of constriction as assessed by the end-diastolic volume. Measurements of relative fiber shortening or lengthening (ejection and filling fraction and circumferential fiber shortening) were normal despite great reduction in ventricular volumes. Velocity measurements, peak LV dp dt and mean velocity of circumferential fiber shortening were normal or slightly reduced. These changes were reflected in the systolic time interval measurements pre-ejection phase, left ventricular ejection time, and the ratio PEP LVET . Diastolic function of the ventricle was abnormal; the distensibility index of the ventriculo-pericardial system ( ΔV ΔP ) was low and the passive elastic modulus in-increased. The change in compliance correlated with the degree of constriction and there was a linear relationship between compliance and EDV. The ventricle was underloaded despite the high filling pressure and stroke work index was reduced; extrinsic compression raised the diastolic pressure and reduced left ventricular volumes.

Hemodynamic comparison of agents useful in hypertensive emergencies

Hemodynamic effects of trimethaphan camphorate (1 mg. per milliliter), a short-acting ganglion blocking agent, sodium nitroprusside (60 μg per milliliter), a vasodilator, and diazoxide (300 mg.), a thiazide congener and vasodilator, were administered intravenously to hypertensive patients. Each drug significantly reduced arterial pressure, but the immediate reduction by diazoxide returned toward pretreatment levels after 20 minutes. The hypotension observed with each agent was associated with reflexive increase in heart rate, but only diazoxide increased cardiac output and left ventricular ejection rate. These results indicate that nitroprusside and trimethaphan can achieve similar hypotensive effects to diazoxide but without additional myocardial stimulation.

Hemodynamic studies in children with congenital atrioventricular block

Eleven children with isolated congenital complete atrioventricular (A-V) block, 3 weeks to 21 years of age, underwent cardiac catheterization, including electrical pacing and isoproterenol infusion studies. The resting ventricular rates of the infants ranged from 60 to 90/min; those of the rest 40 to 55/min. The resting intracardiac pressures were normal or minimally increased. Mean cardiac index was low normal (3.3 liters/min per m 2 ± 0.8 SD), but stroke index was abnormally high (65.6 ml/m 2 ± 12.1 SD). Electrical pacing of the right ventricle to rates of 60 to 120 beats/min resulted in increased cardiac index (+26 percent), left ventricular minute work (+31 percent) and left ventricular stroke output impedance (+63 percent), but reduced stroke index (−32 percent), left ventricular stroke work (−37 percent), and tension-time index per beat (−36 percent). No significant changes in systemic vascular resistance, left ventricular ejection rate or output/tension-time ratio were observed. Isoproterenol infusion resulted in greater rise in cardiac index (+65 percent), left ventricular ejection rate (+57 percent) and output/tension-time ratio (+45 percent), no change in stroke index, and reduced systemic vascular resistance (−39 percent). The hemodynamic improvement due to isoproterenol infusion reflects the agent's combined inotropic, chronotropic and peripheral vasodilatory effects. The overall hemodynamic findings in children with congenital A-V block are better than in adults with acquired block. It is suggested that intrinsic myocardial disease may be a significant feature in symptomatic subjects with this disease.

Clinical-physiological correlations in the development of hypertensive heart disease.

In order to understand more precisely the progression of ventricular dysfunction in hypertension prior to development of ventricular failure, 25 normal volunteer subjects and 97 untreated essential hypertensive patients (21 of whom had coronary arteriography and failed to show significant atherosclerosis) were classified into three groups: (I) normal-sized hearts, 54 patients; (II) left atrial enlargement (ECG criteria), 20 patients; and (III) left ventricular enlargement (ECG and chest X-ray criteria), 23 patients. Heart rate was elevated ( P &lt; 0.001) in all three groups; total peripheral resistance and arterial pressure increased progressively from group I to II to III ( P &lt; 0.001); cardiac index was reduced only in group III ( P &lt; 0.001). However, despite normal cardiac index in group II, left ventricular ejection rate was impaired ( P &lt; 0.01), and tension-time index and pressure-time per beat were greater than in patients with normal-sized hearts ( P &lt; 0.001). Thus, left atrial enlargement provided the initial evidence of left ventricular dysfunction. Later, when left ventricular hypertrophy became clinically apparent (always associated with left atrial abnormality) further impairment of left ventricular function was evident. Since these hemodynamic changes were observed in patients with normal coronary arteries, presence of left atrial and ventricular enlargement should provide useful criteria for classifying functional impairment in hypertensive heart disease.

New functional concept of valvular mechanics in normal and diseased aortic valves.

The orifice area of the functioning aortic valve was measured roentgenographically and related to flow across the valve in 27 patients (12 with normal valves). The orifice area of normal valves was linearly related to stroke index and to left ventricular ejection rate. Less than half of the cross-sectional area of the valve was utilized in most patients during the resting state. A larger percentage of the anatomical cross-sectional area was utilized during states of higher flow. Cinematographic studies of porcine valves in vitro showed a comparable flow-dependent orifice size. These results suggest the concept of a functional or physiologic cross-sectional area of the aortic valvular orifice. The anatomic cross-sectional area may be restricted without impingement upon the functional cross-sectional area in states in which flow across the valve is low.

Functional correlates of plasma renin activity in hypertensive patients.

Correlates of peripheral plasma renin activity were studied in 31 normotensive subjects and 93 untreated hypertensive patients. The latter were grouped according to apparent type of hypertension: essential (58), renovascular (21), renal parenchymal disease (11), and primary aldosteronism (3). Plasma renin activity was inversely correlated with total blood and plasma volumes in normal men, men with essential hypertension, and patients with renal arterial stenosis; no correlations were found in normal and essential hypertensive women and patients with renal parenchymal disease. Serum sodium and potassium concentrations were significantly and inversely related to renin activity only in renovascular hypertension and not in the other hypertensive or normal groups. Relationships of plasma renin activity to arterial pressure and other hemodynamic functions were studied in hypertensive patients. Only in the renovascular group did diastolic pressure correlate positively and significantly, indicating participaton of the renal pressor system in this form of hypertension throughout a wide range of pressures. Cardiac index and left ventricular ejection rate were directly related to renin activity in essential hypertensive men and patients with renal arterial and parenchymal diseases. The data show that plasma renin activity in hypertensive patients should not be judged alone but along with factors modifying it.

Effects of propranolol on the resting and exercise hemodynamics of pulmonary stenosis.

Propranolol 0.016 mg/kg was given to 15 patients with pulmonary stenosis to study the effects of beta adrenergic inhibition on right ventricular (RV) dynamics at rest and during exercise. After propranolol, mean heart rate declined 8 beats/min at rest and 21 beats/min during exercise; mean cardiac index decreased 0.6 l/min at rest, 1.0 l/min during exercise; stroke index decreased 4.0 ml at rest, was unchanged during exercise; mean peak systolic RV pressure fell 8 mm at rest, 24 mm during exercise; RV end-diastolic pressure increased 3 mm during exercise; brachial artery systolic pressure decreased 24 mm during exercise; the duration of RV systole during exercise was increased by 0.03 s; mean RV pressures decreased 5 mm at rest, 11 mm during exercise; RV tension time index decreased 20% at rest, 26% during exercise; and mean mixed venous oxygen saturation during exercise fell from 42 to 35%. This study serves to emphasize that peak RV pressures in pulmonary stenosis are not only dependent on valvular anatomy and stroke volume, but also on the rate and pattern of ventricular ejection.

Left ventricular ejection rate in man with heart disease

Left ventricular ejection rate in man with heart disease

Long-Term Physical Training and Cardiovascular Dynamics in Middle-Aged Men

The effects of a 7-month physical training program on the physiological responses to exercise and work capabilities of seven middle-aged, sedentary men have been evaluated. Testing involved bicycle ergometry and interval treadmill walking, as well as pre- and postconditioning hemodynamic investigations during five levels of treadmill walking up to a 25% grade. Significant alterations of several parameters were observed in the trained state. Resting and exercise bradycardia were marked, the lowest heart rate registered being 49/min. Maximal physical working capacities and maximal oxygen uptakes were uniformly increased with group means of + 22 and + 18%, respectively. Work load capacities at heart rates 130, 150, and 170 were also augmented. Resting and exercise cardiac output for a given oxygen uptake declined and produced relative hypokinesis. Stroke volume was greater at moderate and heaviest work loads. Cardiac minute work was reduced despite stroke volume increments. Pulse wave and arterial pressure analyses indicated that tension-time index and ejection-time index were markedly reduced, while maximal pressure derivative and ventricular ejection rate were increased. It is concluded that aside from subjective enhancement of well-being, a well-planned physical training program for middle-aged men can develop beneficial economy and efficiency of myocardial function and the oxygen transport system.

Effect of the thyroid state on myocardial contractility and ventricular ejection rate in man.

Although the circulatory changes in various thyroid states are well known, the alterations of myocardial contractility of hypothyroidism and hyperthyroidism have remained controversial. The changes in the length of the ejection time (ET) and isovolumic contraction time (ICT) are used as indicative of alterations in inotropic state of the myocardium. Isovolumic contraction time, ejection time, and pre-ejection period were measured externally in 10 normal, 13 hyperthyroid, and five hypothyroid subjects. Cardiac outputs, mean rate of left ventricular ejection index, and predicted ejection times were calculated. More shortening of ICT and ET in hyperthyroid and more prolongation of these intervals in hypothyroid subjects than could be attributed to other factors were interpreted as indicative of increased and decreased myocardial contractility, respectively. Catecholamine depletion in hyperthyroid subjects with adequate administration of intramuscular reserpine induced no changes in cardiac output and oxygen consumption and caused no alteration in different phases of ventricular systole; consequently it had no effect on enhancement of hyperthyroid myocardial contractility.

Factors contributing to the ballistocardiographic waveform in healthy middle-aged men

The availability of a large number of variables made it possible to delineate those human factors which may contribute to ballistocardiographic acceleration wave formation. Attempts were made to explain some of these relations on a physiologic basis, not to prove cause and effect, but only to emphasize areas where this information seemed to suggest the necessity of more extensive evaluation. It appeared that association of ballistocardiographic waveforms with ventricular pressures, stroke volume, cardiac output, rate of ventricular ejection, aortic flow and other similar measures should be evaluated as well as the relation of these items to physical, clinical and laboratory determinations so that interrelations may be determined. This would be expected to increase the value of the ballistocardiogram in the clinical and experimental situation. Until such studies are completed, it seems that the knowledge that multiple factors appear to alter the ballistocardiographic acceleration waveform in varying degrees suggests caution in the quantitative use of the ballistocardiographic standards derived from groups in predicting stroke volume and other physiologic measures. The results of this study indicate that use of serial ballistocardiograms will be necessary for determining cardiovascular status. It is hoped that consideration of these numerous relations will lead to a more meaningful ballistocardiographic interpretation and consequently to its greater use.

INFLUENCE OF ACIDEMIA ON LEFT VENTRICULAR FUNCTION IN THE NEWBORN LAMB

The performance of the left ventricle in 20 newborn lambs was examined in a preparation which allowed precise control of aortic pressure, cardiac output, heart rate, and temperature. Reduction of arterial pH from a normal range (7.35 to 7.5) to severe acidemia (6.8 to 7.0) by hydrochloric or lactic acid infusion resulted in no significant impairment of left ventricular function. Prolonged acidemia (over 2 hours) failed to produce a reduction in left ventricular stroke volume or mean ejection rate for a given left ventricular end-diastolic pressure. Responsiveness of the left ventricle of the lamb to catecholamine stimulation was not diminished over the pH range 7.5 to 6.8. Under conditions of these investigations the apparent resistance of the myocardium of the newborn lamb, as well as the adult cat, to wide variations in pH may reflect a buffering capacity of cardiac muscle which would allow minimal change in intracellular pH, even though extracellular pH may indicate the presence of severe metabolic acidosis.

Effects of amyl nitrite in aortic valvular and muscular subaortic stenosis.

The effects of amyl nitrite inhalation were observed in 12 patients with aortic valve stenosis and five patients with muscular subaortic stenosis during left heart catheterization. In aortic valve stenosis the left ventricular systolic pressure always fell, although less than the brachial arterial pressure, and the transaortic systolic pressure gradient rose by an average of 25% due to the increase in left ventricular ejection rate. In muscular subaortic stenosis, the left ventricular pressure always remained the same or rose despite a marked fall in brachial arterial pressure, and the average increase in transaortic systolic pressure gradient was more than fourfold. This effect was associated with a significant increase in the degree of outflow tract obstruction. The increase in outflow tract obstruction is thought to be due to a decrease in left ventricular volume, causing the hypertrophied walls of the left ventricle to become more closely apposed. We believe that inhalation of amyl nitrite is superior to infusion of isoproterenol as a provocative test for muscular subaortic stenosis during cardiac catheterization and is probably the most potent stimulus available for this purpose.

Stroke volume changes in baboons during spontaneous activity and exercise

M OST of the fundamental concepts of the function and control of circulation have evolved from experiments performed on dogs. Use of dogs for experiments has the advantage of convenience, but in certain cardiovascular studies, e.g., effects of exercise, there are cogent reasons for selecting an animal more closely related to man. Dogs are phylogenetically remote from man and are anatomically specialized for a different way of life. For example, their peripheral muscle mass is less well developed. Although dogs are susceptible to training, their capacity for learning is probably inferior to that of primates. This fact is particularly significant in view of recent evidence implicating higher nervous centers in the control of the cardiovascular system. In this study we have evaluated the spontaneous variations in stroke volume of a simian primate, the baboon, during spontaneous activity, postural changes and exercise. Flow in the ascending aorta was continuously recorded via chronically implanted ultrasonic flowmeters. The heart rate, stroke volume, cardiac output and duration of ventricular ejection were then computed from these recordings.

LEFT VENTRICULAR EJECTION TIME INDEX IN MAN.

The present studies were undertaken in an attempt to formulate an accurate expression of the relationship between the duration of left ventricular ejection and heart rate in man. On the basis of regression equations relating the duration of left ventricular ejection and heart rate in normal individuals, the index LVET + .0016 HR was derived and tested in normal adults and prepubertal children. The left ventricular ejection time index (ETI) remained constant and reproducible over the range of heart rate from 50 to 150 and yielded more consistent values in this range of heart rate than did previously derived equations. A slight but significantly higher value of the ETI was present in the adult females when compared to the adult males, while no significant difference according to sex was apparent in the children. A decrease in ETI was found when cardiac output was diminished in normal individuals during 60° head-up tilt and in patients with congestive heart failure. Of note was the finding of a significant correlation between the level of the ETI and the cardiac output in these situations. Submitted on December 13, 1962

Determinants of duration and mean rate of ventricular ejection.

The independent influences of stroke volume, heart rate, aortic pressure, hypothermia, sympathomimetic amines, metered mitral and aortic valvular regurgitation, and alterations in myocardial contractility on the duration and mean rate of ventricular ejection and filling were studied. These observations were made in a metabolically supported, isolated heart preparation with performance characteristics comparable to the non-isolated heart.