Indices Of Cardiac Performance Research Articles

Epidemiologic patterns, clinical evaluation, and long-term prognosis in chronic congestive heart failure

Congestive heart failure affects more than 2,000,000 Americans and is likely to increase in prevalence as our population ages. Clinical congestive heart failure should not be equated with cardiac dysfunction, as indexes of cardiac performance do not correlate with clinical manifestations. The clinical signs and symptoms of heart failure often lack sufficient sensitivity and specificity to permit accurate diagnosis. Objective tests, such as echocardiography and radionuclide angiography, are usually needed to establish the presence of left ventricular dysfunction, and exercise testing may be needed to quantitate symptomatic severity. Indexes of cardiac function do not correlate well with symptomatic status, and clinical assessment of severity of symptoms is often inaccurate. Therefore, exercise testing may be very useful in assessing symptomatic severity and in following patient progress. Prognosis in heart failure is very poor, with fewer than 50 percent of patients surviving five years from the time of initial diagnosis. Survival appears to relate more to the degree of cardiac dysfunction and less to the degree of symptomatic severity. Early recognition of heart failure in a latent stage and development of strategies aimed at preventing or delaying the onset of overt heart failure appear to offer the best chance of reducing mortality from heart failure.

ADRENERGIC MECHANISMS IN CONGESTIVE HEART FAILURE

The normal control of cardiovascular function exerted by the sympathetic nervous system is disturbed in congestive heart failure. The failing pump function of the heart evokes an increase in sympathetic activity which may be reflected in increased levels of plasma noradrenaline. However, these levels are generally below the concentrations needed to activate the adrenergic effector systems, indicating that the cardiovascular consequences of the increased sympathetic activity is not mediated by circulating noradrenaline. In the failing human heart there is a decrease in beta-adrenoceptor density which is related to decreasing ventricular function. This finding suggests that the myocardium is exposed to high concentrations of noradrenaline, inducing downregulation of the receptor number, despite the fact that in the failing heart the noradrenaline stores are reduced. In heart failure the plasma noradrenaline concentration was found to be directly related to mortality and was suggested to provide a better guide to prognosis than other commonly measured indexes of cardiac performance.

Evaluation of beta-adrenergic influences on cardiovascular and metabolic adjustments to physical and psychological stress.

ABSTRACTThis study was designed to examine the hypothesis that certain behavioral demands may tend to trigger sympathetic mechanisms which result in metabolically excessive cardiac output elevations. Oxygen consumption and cardiac output adjustments during a contrived reaction‐time shock‐avoidance task were compared to a cold pressor test in healthy young male adults. The linear cardiac output/oxygen consumption relationship generated by performance on a graded exercise task was used to assess the metabolic appropriateness of cardiac output adjustments to the reaction‐time task and cold pressor. The reaction‐time task was generally found to evoke metabolically excessive increases in cardiac output, while cardiac output adjustments to cold pressor were more consistent with changes in metabolic demands. However, the tasks were associated with similar heart rate responses, with a significant attenuation in stroke volume during cold pressor accounting for the differential alterations in cardiac output. This finding suggests a limited reliability for heart rate as an index of cardiac performance. The effects of propranolol, which was employed to evaluate the role of sympathetic influences, indicated that beta‐adrenergic mechanisms were responsible for mediating the cardiac output response to the reaction‐time task, but only partially contributed to the cold pressor response. Post‐hoc analyses of individual differences in cardiovascular reactivity to the reaction‐time task suggest that, for hyperreactive individuals, the coping responses evoked by this task may lead to tissue overperfusion with oxygen, thereby providing a stimulus for autoregulatory vascular reflexes which may be associated with the etiology of hypertensive disease.

Quantitative analysis of global and regional cardiac performance in normal subjects and patients with coronary artery disease by rest/exercise radionuclide blood-pool study.

This study was undertaken to assess regional and diastolic left ventricular (LV) function in relation to LV asynchronous contraction during exercise (Ex). Rest and serial Ex (25w-75w) gated blood-pool study (Tc-99m-RBC) of 6 normal subjects (N), 12 patients with stable angina pectoris (AP) and 8 with LV aneurysm (LVan) were evaluated in regional LV ejection fraction (EF) and Fourier analysis using higher-order harmonics. In the patients with Ex and regional EF showed various responses to Ex. Global LVEF in the patients with AP indicated almost no change during Ex and regional EF declined apparently in anteroseptal segment, corresponding to stenotic left anterior descending artery. Diastolic indices of regional and global cardiac performance, PFR (peak filling rate), TPF (time to PFR) and standard deviation (SD) of TPF histogram, were obtained by Fourier analysis using two-order harmonics. Patients with coronary artery disease (CAD) showed significantly lower PFR, longer TPF and higher SD of TPF than normal group, suggesting asynchronous relaxation. We conclude that regional EF response and diastolic indices of cardiac performance to exercise provide useful and sensitive information detecting the severity of CAD.

Solid-state extraction of digoxin-like substancesfrom human urine

To determine the relation between urinary digoxin-like immunoreactive substance (DLIS) and cardiac performance.Cohort study.Echocardiography laboratory of a university-affiliated teaching hospital.Thirty-four individuals referred for echocardiographic studies who had never received cardiac glycosides or other substances known to cross-react with a digoxin radioimmunoassay and had no condition that has been associated with increased DLIS.Cardiac dimensions and indices of cardiac performance derived from echocardiograms and cardiac Doppler flow studies and concentrations of urinary DLIS, creatinine, and electrolytes.Urinary DLIS ranged from <0.125 ng (digoxin equivalents) per milliliter (below the sensitivity of the assay) to 0.99 ng/ml, averaging 0.22 ± 0.24 ng/ml. On bivariate analyses, UDLIS was found to correlate significantly with body weight, left ventricular (LV) end-diastolic dimension, LV fractional shortening, mitral transvalvular flow velocity following atrial systole, and urinary calcium. On multivariate analyses, the association between urinary DLIS (alone or adjusted for urinary creatinine) and LV fractional shortening emerged as the paramount independent relation.Urinary DLIS can be related to cardiac performance under steady-state conditions. This suggests that DLIS may be a ligand for a cardiac glycoside receptor.

Plasma norepinephrine as a guide to prognosis in patients with chronic congestive heart failure.

Hemodynamics, plasma norepinephrine, and plasma renin activity were measured at supine rest in 106 patients (83 men and 23 women) with moderate to severe congestive heart failure. During follow-up lasting 1 to 62 months, 60 patients died (57 per cent); 47 per cent of the deaths were sudden, and 45 per cent were related to progressive heart failure. Statistically unrelated to the risk of mortality were cause of disease (60 patients had coronary disease, and 46 had cardiomyopathy), age (mean, 54.8 years), cardiac index (mean, 2.11 liters per minute per square meter of body-surface area), pulmonary wedge pressure (mean, 24.5 mm Hg), and mean arterial pressure (mean, 83.2 mm Hg). A multivariate analysis of the five significant univariate prognosticators--heart rate (mean, 84.4 beats per minute), plasma renin activity (mean, 15.4 ng per milliliter per hour), plasma norepinephrine (mean, 700 pg per milliliter), serum sodium (mean, 135.7 mmol per liter), and stroke-work index (mean, 21.0 g-meters per square meter)--found only plasma norepinephrine to be independently (P = 0.002) related to the subsequent risk of mortality. Norepinephrine was also higher in patients who died from progressive heart failure than in those who died suddenly. These data suggest that a single resting venous blood sample showing the plasma norepinephrine concentration provides a better guide to prognosis than other commonly measured indexes of cardiac performance.

Application of statistical methods for the analysis or interval related cardiac performance variations during cardiac arrhythmia in man.

To study the influence of the sequence of stimulation intervals on cardiac performance indices the relationship between properties of succeeding arrhythmic aortic pressure pulses of patients with atrial fibrillation has been analysed by methods of correlation and regression analysis. There are high correlations between properties of succeeding pulses and it can be shown that the pressure amplitude of one pulse correlates to the properties (diastole, diastolic pressure, pressure amplitude) of up to five preceding pulses. Furthermore, the diastolic pressure is also highly correlated with properties of more than one preceding pulse whereas the duration of the diastole and the RR-interval is independent of preceding pulse properties. We, therefore, conclude that there is no beat to beat regulation of intervals during atrial fibrillation. The relations between properties of succeeding pressure pulses have been summarised in a transfer function model, which allows the description of pulse properties from preceding pulse properties without lack of it. The parameters of the transfer function models are estimated from a sequence of arrhythmic pressure pulses and a parameter selection procedure was developed which identifies the optimal number of input variables (= properties of preceding pulses) required to describe the time course of one pulse property. In order to obtain informations about the presence of possible interval dependent potentiation effects, the transfer function model was used to stimulate the behaviour of the aortic pressure for different stimulation sequences, which have been used in the literature to study potentiation effect experimentally. From typical sequences of potentiation phenomena in the stimulated pulse sequence we conclude that frequency potentiation effects exist in the human myocardium.

Left ventricular function after chronic insulin treatment in diabetic and normal rats.

Previous reports have documented a cardiomyopathy in rats resulting from streptozotocin-induced diabetes. In order to determine the reversibility of streptozotocin-induced cardiomyopathy to insulin therapy, hearts from rats made diabetic by streptozotocin for 6 weeks and then treated with insulin for 3 weeks were compared with untreated diabetic rats and control rats not injected with streptozotocin. When perfused in an isolated working heart apparatus with 5.5 mM glucose as substrate, hearts from untreated diabetic rats when compared to hearts from either streptozotocin-injected rats treated with insulin or control rats showed significant depressions in peak left ventricular pressure, maximal positive and negative dP/dt, oxygen extraction, lactate production and effluent lactate; pyruvate ratio. Ca2+-actomyosin ATPase was also depressed in untreated diabetics. As left atrial pressure was raised in untreated diabetic rats, a decline in cardiac output was observed, whereas in insulin-treated or control groups there was no such negative response. Indices of cardiac performance were significantly greater in insulin-treated rats when compared to control rats suggesting overcorrection with insulin therapy. To explore whether insulin treatment may have a beneficial effect on the myocardium control rats were made hyperinsulinemic for 6 to 7 weeks. Shorter isovolumic relaxation times and elevated values for Ca2+-actomyosin ATPase were observed in hearts from hyperinsulinemic animals when compared to hearts from control animals. These results demonstrate complete reversibility of streptozotocin-induced cardiomyopathy and confirm that this condition is due to insulin deficiency and not to a primary cardiotoxic effect of streptozotocin.

Canine left ventricular performance during LD50 endotoxemia

Previous reports of the effect of endotoxin shock on cardiac performance have not achieved uniform results. These discrepancies have possibly been caused by the use of indices of cardiac performance that may have been sensitive to altered heart rate or preconditions of cardiac contraction as well as altered cardiac performance. We tested the hypothesis that, following a median lethal dose (LD50) of E. coli endotoxin, cardiac performance would be diminished in nonsurviving animals and maintained in surviving animals. We elected to employ the analysis of the end-systolic pressure-diameter relationship (sigma ES) as well as other measurements of cardiac performance to test this hypothesis. We established that the sigma ES measurement was independent of increased and decreased afterload and relatively insensitive to altered heart rate. In the nonsurviving animals, sigma ES exhibited a marked depression following endotoxin a administration. In the surviving animals, sigma ES exhibited a nonsignificant decrease followed by a return toward preendotoxin values. All other cardiodynamic measurements were uninterpretable due to the marked changes in heart rate, peripheral vascular function, aortic pressure, and cardiac output. We conclude that, following endotoxin administration, those animals that exhibited a diminished myocardial contractility failed to survive more than 2.5 h postendotoxin, whereas the surviving animals were able to restore normal cardiac contractility. Thus survival of endotoxin administration is associated with the maintenance of normal cardiac contractility.

Blood pressure related echocardiographic changes in adolescents and young adults

In 1973, standardized blood pressure measurements were obtained in 837 high school students in Bourbon County, Kentucky, a rural county with a high prevalence of individuals with systemic hypertension. In 1978, follow-up measurements of blood pressure were performed in selected individuals who were in the high, intermediate, and low ranges of the initial sex-specific blood pressure distributions. Relative rank order of initial blood pressure measurements over the five-year period was maintained. The results of this population-based study provided an opportunity to evaluate the cardiac status in young adults with relatively high blood pressures maintained over five years. Standard m-mode echocardiographic examinations were, therefore, performed at the time of follow-up. In individuals in the low and intermediate ranges for systolic blood pressure, indices of ventricular hypertrophy were directly correlated with blood pressure level. Among individuals with higher values for systolic blood pressure, after adjusting for the effects of relative body size, indices of ventricular hypertrophy were not significantly different from those noted in the intermediate group. Indices of cardiac performance and estimated left ventricular systolic wall stress were, however, significantly elevated in this “high” blood pressure group. Early in the course of systemic hypertension increased wall stress, rather than hypertrophy, appears to be the primary cardiac manifestation of elevated systolic blood pressure.

The Effect of Dopamine on Postburn Myocardial Depression

Myocardial performance is severely depressed following burns to more than 30% of the body surface area. Cardiac output in the immediate postburn period is dissociated from plasma volume. Many attempts have been made to improve early postburn hemodynamics with little success. Continuous infusion dopamine in low doses has recently been reported to improve at least one index of cardiac performance (LVSWI). We report the use of low-dose (5-10 mcg/kg X min) dopamine in the first 24 hours postburn in 20 seriously burned adults. Hemodynamic data are presented immediately preinfusion and after 1 hour of dopamine. Low-dose dopamine produced no change in cardiac index, arterial pressure, LVSWI, or any other hemodynamic parameter. We conclude that dopamine is of no benefit in treating the depressed myocardial function seen following major burns.

Radionuclide angiographic evaluation of left ventricular function by resting ejection rate during the first third of systole in patients with chronic aortic regurgitation

In previous studies the rate of left ventricular (LV) volume change during the first third of systole was shown to be a more sensitive index of cardiac performance than ejection fraction (EF) in coronary disease. To test the hypothesis that a noninvasive index of the ejection rate in early systole can also identify subtle abnormalities of LV performance in aortic regurgitation (AR), the rate of change of LV counts during the first third of systole was measured by first-pass radionuclide angiography (RNV) in 34 AR patients and in 10 normal controls. By least squares analysis a straight line was fit to the LV counts obtained at 0.025 second intervals during the first third of systole; the slope was divided by the average counts in the first third to give a rate constant (RC) proportional to LV volume change during early systole. The AR patients were divided into two groups based upon the response of EF to exercise (ΔEF). A normal response was defined as a rise equal to or greater than 5%. Group 1 comprised 19 AR patients with a normal EF response to exercise (from 60 ± 9% to 70 ± 9%), and group 2 comprised 15 AR patients with an abnormal EF response to exercise (from 58 ± 9% to 52 ± 10%). The RC obtained at rest was 9.4 ± 2.8 for group 2, significantly lower than for group 1 (15.6 ± 3.9) or controls (14.9 ± 2.6) ( p < 0.01). Using an RC of 12.0 as a cutoff, separation of the two AR groups was excellent ( p < 0.01) with only one group 1 patient with RC < 12.0 and two in group 2 with RC > 12.0. When RC was plotted vs EF for all 44 individuals, there was a significant direct relationship, r = 0.74 ( p < 0.01), but with wide confidence limits. These data indicate that a noninvasive index of the rate of LV volume change during the first third of systole can identify abnormal LV reserve in AR patients with normal EF at rest.

The effects of peripheral impedance and inotropic state on the power output of the left ventricle in dogs.

The power output of the left ventricle as measured by the product of the Fourier components of aortic pressure and aortic flow is linked by definition to the arterial impedance facing the heart as measured by the quotient of these components. Consequently, the use of power measurements to assess ventricular performance can be ambiguous when accompanied by afterload changes. The heart is considered to function normally between two extremes, a constant flow pump, and a constant constant pressure pump, and two power limits are defined from these. The power limits describe the extent to which impedance changes can affect the power delivered by the left ventricle. Measured power changes that are found to lie outside the two limits can be unambiguously ascribed to changes in inotropic state. The results from preliminary dog experiments designed to test this method are reported. Cardiac sympathetic stimulation and isoprenaline infusion were used to provide a pure inotropic stimulus and a mixture of inotropic and afterload changes, respectively. The technique was able to detect inotropic changes in the heart even in the presence of simultaneous changes in afterload. Eight conventional indices of cardiac performance were monitored for comparison. The extent of their afterload dependence may not be as easily quantified.

A framework for three-dimensional time-varying reconstruction of the human left ventricle: Sources of error and estimation of their magnitude

This report summarizes development of a computer/ultrasound system to graphically reconstruct the contracting human left ventricle in three dimensions and calculate indices of cardiac performance. The three-dimensional reconstruction is performed by realignment of five cross-sectional two-dimensional echograms along a single longitudinal section. The spatial position of the cross sections is recorded by a specially developed indexing arm. Cross sections are then realigned perpendicular to the long axis and parallel to each other by the computer. Points at 30° intervals are chosen from the inner and outer muscle boundaries of a cross section and connected by straight lines. Thus areas can be calculated simply by summation of triangular areas with vertices at the origin. Volumes can then be calculated using a modified Simpson's rule. To test these computer programs three hypothetical time-varying computer-generated left ventricular models were developed. Effects of six major anticipated sources of error were determined by systemic introduction of simulated measurement errors into data for these hypothetical models. These results demonstrate that this system is practical for the three-dimensional reconstruction of the left ventricle, that volumes and derived indices of ventricular performance can be calculated, and that anticipated sources of error result in relatively small deviations from true values.

Non-Invasive Measurement of Brachial Artery Peak Velocity as an Index of Cardiac Performance in Normal Subjects and Patients with Acute Myocardial Infection

Non-Invasive Measurement of Brachial Artery Peak Velocity as an Index of Cardiac Performance in Normal Subjects and Patients with Acute Myocardial Infection

Effects of intravenous disopyramide on myocardial function in patients with different degrees of cardiac failure.

The effects of intravenous disopyramide phosphate on myocardial function were evaluated by non-invasive indices of cardiac performance (systolic time intervals, STI) in 15 patients with atherosclerotic heart disease and different degrees of cardiac failure. Disopyramide (1.5 mg/Kg) was given intravenously over a period of 5 min. This drug induced in patients in I-II classes of NYHA a significant decrease of LVETc, while PEP, ICT, and PEP/LVET ratio rose significantly. STI were affected much more markedly in patients in III-IV classes of NYHA. Particularly affected were contractility indices (PEP, ICT, PEP/LVET), which were reduced significantly more in patients in III-IV classes as compares to patient in I-II classes. In contrast, LVETc, which correlates to stroke volume and cardiac output, was similarly worsened by the drug in the 2 groups of patients. Therefore, this study shows that disopyramide has relevant depressant effects on myocardial performance, simultaneously reducing stroke volume and contractility, and that the effect on contractility is more marked in patients with severe left ventricular impairment.

Relationship between systolic time intervals and heart rate during atrial or ventricular pacing in normal subjects.

Systolic time intervals (STI) are regarded as good indices of cardiac performance in many heart diseases. It must be considered, however, that they are temporally related to the cardiac contraction cycle and, therefore, may be modified by heart rate changes. Thus, it is necessary to define the possible relationship between STI and heart rate changes. In this study, changes in heart rate were induced by atrial and ventricular pacing. Tachycardia caused a proportional decrease of left ventricular ejection time (LVET) (y=275.142-1.0025 x, r=0.76, p less than 0.001 for atrial pacing and y=298.28-0.691 x, r=-0.75, p less than 0.001 for ventricular pacing, respectively), but did not modify the pre-ejection period (PEP) and the isometric contraction time (ICT) and the electromechanical interval (QS1). These results demonstrate that while LVET must be corrected for the changes in heart rate, no correction of PEP and ICT is necessary.

A Simulation of the Dynamics of Counterpulsation

An open-loop, lumped parameter, digital computer model of the left heart, coronary artery, and aortic tree is discussed. Introduction of an external flow source (counterpulsation pump system) at any of the eight major nodal points located along the aorta is permitted. The model is run for a variety of conditions to assess the effects of counterpulsation pump timing, stroke volume, infusion/aspiration rate and pump cannula location on selected indices of cardiac performance. Simulation results are compared to appropriate data from two series of animal experiments using a thin-walled cannula and a pneumatically driven, nonhemolytic counterpulsation pump system.

Cardiac dose response relationship for intravenously infused glucagon in normal intact dogs and men

The mechanism of glucagon's cardiac effects is not well understood. As the cardiac dose response to glucagon in intact animals has not been elucidated, this was determined in normal men and dogs. In man, heart rate, blood pressure, systolic time intervals and echocardiographic indices of ventricular wall motion were determined. Plasma glucagon levels (PGL) were measured by radioimmunoassay. Men received 3 glucagon infusions of 10 −10 to 10 −8 moles/minute followed by a bolus of 0.5 mg. or 1.0 mg. Small but significant changes were observed in ejection fraction and left ventricular posterior wall displacement at the 10 −9 moles/minute infusion rate (mean PGL 1.9 ng./ml.), a PGL close to that of some pathophysiologic states such as burns, ketoacidosis, and acute myocardial infarction, while cardiac output, heart rate, and other indices of cardiac performance were significantly changed only at the 10 −8 moles/minute and bolus injections. Some indices, notably stroke volume, were unchanged. In dogs, left ventricular (LV) pressure, LV pressure derivative (LV dP dt ), and aortic flow were measured with implanted LV solid state pressure transducers and electromagnetic flow probes. Dogs received six infusions from 2.7 × 10 −11 to 2.7 × 10 −8 moles/minute followed by a bolus of 2 mg. In dogs, significant changes occurred in LV dP dt at 2.7 × 10 −9 moles/minute (mean PGL 31.5 ng./ml.) and in heart rate at 2.7 × 10 −8 moles/minute only. It appears that substantial hemodynamic effects do not appear in man or dogs until PGL 10 to 100 times those seen in pathophysiologic states are achieved. Thus, it seems unlikely that glucagon contributes substantially to the hyperdynamic circulatory conditions observed in these states. Significant hemodynamic response to glucagon was noted in normal men, however, at a PGL less than that achieved by usual pharmacologic doses of glucagon and this lower PGL was not associated with the gastrointestinal symptoms commonly observed clinically.

Echocardiography as an index of cardiac performance.

Ultrasound imaging of the heart provides a noninvasive technique for assessing cardiac performance and diagnosing a wide range of disorders. Recent improvements in two-dimensional, planar instrumentation promise to make echocardiography even more versatile, permitting more comprehensive views of left ventricular function, valve orifice areas, and the spatial relationships of the great vessels and ventricular chambers.