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Results for “Ejection fraction”

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At least 19 recordsLinked to original sources

PubMed1985

Are right and left ventricular ejection fractions equal? Ejection fractions in normal subjects and in patients with first acute myocardial infarction.

Right and left ventricular ejection fractions (RVEF and LVEF) were determined by radionuclide imaging in 37 normal subjects and 37 patients by means of (1) the traditional way of calculating ejection fraction from first-pass time-activity curves of each ventricle generated from a single fixed ventricular region of interest, (2) dual first-pass time-activity curves generated from the end-diastolic and end-systolic regions, respectively, and (3) the multigated equilibrium method, also applying separate regions in end-diastole and end-systole for each ventricle. Values for RVEF measured by method 2 were significantly higher than values obtained by methods 1 and 3. In normal subjects, the values for RVEF measured by method 2 were equal to the values for LVEF determined by either this method or the equilibrium technique. Methods 1 and 3 had a tendency for underestimation of RVEF, probably because of inclusion of right atrial activity into the right ventricular region of interest. Methods 2 and 3 were applied to measure RVEF and LVEF, respectively, in 153 patients in the second week after first acute myocardial infarction. Among these, 25% had normal ejection fractions, 47% had a decrease in only LVEF, 8% a decrease in only RVEF, and 20% a decrease in both RVEF and LVEF.

Acute Disease↗

PubMedDate not supplied

Automatic ventricular edge detection for determination of left ventricular volumes, ejection fraction and regional ejection fractions from first pass radioisotope angiography.

An automated method for detection of left ventricular (LV) outline (including the aortic and mitral valve planes) was developed for measurements of end-diastolic volume (EDV), end-systolic volume (ESV), global ejection fraction (EF), and regional EFs from first pass radioisotope ventriculography. The procedure includes: (1) interpolative background subtraction, (2) construction of gradient images, (3) automatic detection of valve planes, and (4) automatic radial search of LV outlines. The correlation between contrast angiography and Tc-99m first pass study was r = 0.84 (SEE = 23.4) for EDV, r = 0.93 (SEE = 12.8) for ESV, r = 0.84 (SEE = 6.91) for EF (via counts) and r = 0.80 (SEE = 8.56) for EF (via area-length method). Tests of intra-observer, inter-observer and inter-study variability revealed low level of variability. The results showed the potential of the automation of data processing for first pass radioisotope ventriculography.

Cardiac Volume↗

PubMed1992

Heart rate index: an indicator of left ventricular ejection fraction. Comparison of left ventricular ejection fraction and variables assessed by exercise test in patients studied early after acute myocardial infarction.

The present study compares the variables assessed by standard exercise test with the left ventricular ejection fraction (LVEF) measured by multigated radionuclide angiocardiography (MUGA) in 77 patients early after myocardial infarction. The exercise test and MUGA were performed within two weeks after the myocardial infarction. A significant correlation (Spearman's correlation coefficient rs, p less than 0.05) was found between LVEF at rest and the following variables assessed at exercise test: 1) the heart rate at rest, 2) rise in heart rate, 3) ratio between maximal heart rate and heart rate at rest, 4) rise in systolic blood pressure, 5) rate pressure product at rest, 6) rise in rate pressure product, 7) ratio (rHR) between maximal rate pressure product and rate pressure product at rest, 8) total exercise time. The heart rate was corrected for effects caused by age (heart index (HR%)) and a significant correlation was found between 1) the HR% at rest, 2) the rise in HR% and the LVEF. A simple method to identify patients with an abnormal LVEF is described.

Adult↗

PubMed1987

Comparison of single plane videodensitometry-based right ventricular ejection fraction in right and left anterior oblique views to biplane geometry-based right ventricular ejection fraction.

To evaluate the reliability of the videodensitometric assessment of right ventricular ejection fraction, 38 patients were studied during diagnostic cardiac catheterization. Digital subtraction images of the right ventricle were obtained in both the right anterior oblique and the left anterior oblique views, using direct intraventricular injection of dilute contrast medium. From the end-diastolic and end-systolic images obtained in each view, analysis of the relative brightness values generated a videodensitometry-based right ventricular ejection fraction for both the right and the left anterior oblique views. These values were compared with those generated by applying the geometry-based Simpson's rule to the orthogonal images. Right ventricular ejection fraction ranged from 22 to 88%. Videodensitometric ejection fraction in the right anterior oblique view correlated well with that in the left anterior oblique view (r = 0.88) and each correlated well with geometry-based ejection fraction (r = 0.91 and 0.82, respectively). In a subset of 18 patients without significant cardiac disease, mean videodensitometric right ventricular ejection fraction was 68% (versus 61% in the abnormal subset), and it correlated closely with left ventricular ejection fraction (r = 0.82). Videodensitometric analysis of digital subtraction images provides a reliable method for calculating right ventricular ejection fraction that is independent of geometry and reliably separates normal from abnormal values. Application of videodensitometric techniques should simplify analysis of the response of the right ventricle to different interventions in patients with cardiac disease.

Adult↗

PubMed1985

Effect of end-diastolic volume on the canine left ventricular ejection fraction.

Left ventricular ejection fraction is commonly used in the clinical assessment of ventricular function. However, the effect of changes in end-diastolic volume on ejection fraction is controversial. The present study examines the effect of changes in end-diastolic volume on ejection fraction in 26 anesthetized dogs on right heart bypass with controlled hemodynamics. At the end of each experiment, pressure-volume relationships were obtained in the potassium arrested heart following suturing of the mitral valve leaflets and clamping of the aortic root. This technique allowed determination of the end-diastolic volume from the end-diastolic pressure. Ejection fraction is highly dependent on end-diastolic volume and end-diastolic pressure at lower levels of end-diastolic volume and end-diastolic pressure. Ejection fraction increased from 30 +/- 1% (SEM) to 64 +/- 2% (p less than 0.001) when end-diastolic pressure was increased from 4 +/- 0.5 to 11 +/- 0.5 cm H2O. The corresponding end-diastolic volumes were 22 +/- 0.5 and 38 +/- 1 ml, respectively (p less than 0.01). Ejection fraction only increased from 64 +/- 2% to 71 +/- 1% (p less than 0.01) when end-diastolic pressure was increased from 11 +/- 0.5 to 18 +/- 1 cm H2O. The corresponding end-diastolic volumes were 38 +/- 1 and 50 +/- 1 ml (p less than 0.01), respectively. This dependence of ejection fraction on preload is present over a wide range of levels of aortic pressure. Similar directional changes in ejection fraction with preload were present after an adequate autonomic blockade, in the presence of either increased or decreased inotropic state and in the presence of an open or closed pericardium. Thus, the present study demonstrates that ejection fraction can be substantially altered by acute changes in end-diastolic volume. This factor should be taken into account when using ejection fraction for the clinical assessment of ventricular function.

Animals↗

PubMed1985

Videodensitometric ejection fraction from intravenous digital subtraction right ventriculograms: correlation with first pass radionuclide ejection fraction.

Thirty-one consecutive patients undergoing intravenous blurred mask digital subtraction right ventriculography were submitted to first pass radionuclide angiography. Second order mask resubtraction of end-diastolic and end-systolic right ventricular digital image frames was executed using preinjection end-diastolic and end-systolic frames to rid the digital subtraction images of mis-registration artifact. End-diastolic and end-systolic perimeters were drawn manually by two independent observers with a light pen. Ejection fractions calculated from the integrated videodensitometric counts within these perimeters correlated well with those derived from the first pass radionuclide right ventriculogram (r = 0.84) and the interobserver correlation was acceptable (r = 0.91). Interobserver differences occurred more frequently in patients with atrial fibrillation and in those whose tricuspid valve planes were difficult to discern on the digital subtraction right ventriculograms. These results suggest that videodensitometric analysis of digital subtraction right ventriculograms is an accurate method of determining right ventricular ejection fraction and may find wide clinical applicability.

Absorptiometry, Photon↗

PubMed1991

Factors determining improvement in left ventricular function after reperfusion therapy for acute myocardial infarction: primacy of baseline ejection fraction.

Improvement in left ventricular ejection fraction is a measure of salvage of ischemic myocardium after reperfusion therapy for acute myocardial infarction. The degree of improvement in left ventricular ejection fraction may be influenced by many factors. Therefore, 137 patients in whom paired radionuclide angiograms were obtained within 24 h of acute infarction and before hospital discharge were retrospectively evaluated to determine which factors most affect improvement in ejection fraction. Only baseline ejection fraction correlated significantly with improvement in ejection fraction by both univariate analysis (ejection fraction as a continuous variable; p less than 0.001; ejection fraction as a categorical variable, less than or equal to 45% versus greater than 45%, p less than 0.0001) and multivariate analysis (p less than 0.0001). Reperfusion status (patent versus occluded infarct artery) and extent of coronary artery disease (one, two or three vessel) were significant factors by multivariate but not by univariate analysis. Location of infarction, treatment modality and time to treatment did not correlate with change in ejection fraction by either statistical technique. Thus, of those factors tested, baseline left ventricular ejection fraction is the most potent predictor of improvement in ventricular function after acute infarction. Knowledge of baseline ejection fraction may be helpful in deciding whether to treat some patients with equivocal indications or contraindications for reperfusion therapy. Clinical trials of reperfusion strategies should stratify patients on the basis of baseline ejection fraction if ejection fraction is to be used as an end point for myocardial salvage.

Adult↗

PubMed1977

Sudden death in the year following myocardial infarction. Relation to ventricular premature contractions in the late hospitals phase and left ventricular ejection fraction.

Both depressed left ventricular ejection fraction and ventricular arrhythmias have been associated with a poor prognosis following acute myocardial infarction. To assess the relative role of each of these parameters in predicting mortality in the early period after hospitalization for myocardial infarction, 24 hour ambulatory electrocardiographic tape recordings and gated cardiac blood pool scans were obtained in 81 patients approximately two weeks after their admission to the hospital for myocardial infarction. Lown class 0 to II ventricular premature contractions during this period were classified as uncomplicated ventricular arrhythmias and Lown class III to V ventricular premature contractions were classified as complicated ventricular arrhythmias. Ejection fraction was calculated from biplane images of gated cardiac blood pool scans. In 35 patients the ejection fraction was greater than or equal to 0.40; only three of these had complicated ventricular arrhythmias. In 45 patients the ejection fraction was less than 0.40; 26 of these had complicated ventricular arrhythmias. Eight patients had documented ventricular fibrillation or instantaneous death during a mean 7.0 moonth (range 2 to 16 months) follow-up period outside the hospital. Although the number of patients studied was small, and there were only eight sudden deaths, life table analysis projected a one year mortality of 66 per cent in patients with complicated ventricular arrhythmias and 31 per cent in patients with an ejection fraction less than 0.40. All eight patients who died suddenly were in the subgroup of 26 patients with an ejection fraction less than 0.40 and complicated ventricular arrhymias; none was in the subgroup of 19 patients with an ejection fraction less than 0.40 and uncomplicated ventricular arrhythmias (P less than 0.02). Although a low ejection fraction may suggest a poor prognosis following myocardial infarction, the presence of complicated ventricular arrhythmias significantly increases the risk of sudden cardiac death in the early period after hospitalization in patients with low ejection fraction.

Arrhythmias, Cardiac↗

PubMed1989

Factor analysis of multigated cardiac blood pool scintigram for the measurement of left ventricular ejection fraction.

Left ventricular ejection fraction (EF) was measured by factor analysis (FA) of multigated cardiac blood pool scintigram in 38 consecutive patients, and compared with that measured by the variable ROI method (EFVROI) with automated left ventricular contour detection. FA was automatically performed without operator intervention with a success rate of 100%. The correlation of EF with EFVROI was significant in the group of 22 patients with normal wall motion (r = 0.65, p less than 0.001), and the entire group of patients (r = 0.70, p less than 0.001), but not significant (p = 0.19) in the group of 16 patients with abnormal wall motion. In conclusion, left ventricular ejection fraction can be estimated by factor analysis of MUGA in patients with normal wall motion.

Adult↗

PubMedDate not supplied

Factors that predict improvement in left ventricular ejection fraction after coronary angioplasty for acute myocardial infarction.

Acute and follow-up angiograms were analyzed in 75 patients with acute myocardial infarction treated with emergency coronary angioplasty to determine factors that might predict improvement in left ventricular ejection fraction. Ejection fraction improved 8.4 +/- 8.2% in 60 patients who maintained patent infarct vessels at follow-up angiography, compared with -4.1 +/- 6.0% in 15 patients who developed reocclusion (p less than .001). In patients with patent infarct vessels, univariate analysis revealed the following significant predictors of improvement in ejection fraction: initial ejection fraction (r = -.38, p less than .003) subtotal vs total stenosis (12.9 +/- 9.3% vs 6.9 +/- 7.3%, p less than .02), infarct vessel (left anterior descending 11.0 +/- 8.4%, right 6.8 +/- 6.4%, circumflex 2.6 +/- 7.5%, p less than .02), and time to follow-up study (less than or equal to 15 days vs greater than 15 days) (4.8 +/- 5.8% vs 9.8 +/- 8.6%, p less than .03). Reperfusion time (less than or equal to 2 hr vs greater than 2 hr) predicted improvement when subtotal stenoses and stuttering infarctions were excluded (10.6 +/- 7.0% vs 4.9 +/- 6.9, p less than .03). Multivariate analysis showed initial ejection fraction and subtotal vs total stenosis to be independent predictors. Patients with anterior infarctions, low initial ejection fractions, and subtotal stenoses or reperfusion times less than or equal to 2 hr are likely to benefit most from coronary angioplasty for acute myocardial infarction.

Angioplasty, Balloon↗

PubMed1990

The nature of the background in radionuclide ventriculography: deductions from the mathematical behaviour of the ejection fraction.

The relationship between the ejection fractions calculated from 'uncorrected' radionuclide time activity curves (UEF) and angiographic ejection fractions (AEF) in 200 catheterized patients yielded the regression equation AEF = 1.74 UEF + 0.21. It follows from this linear relationship that the left ventricular ejection fraction can be estimated by linear regression without explicit background correction: RREF = 1.74 UEF + 0.21, where RREF is the radionuclide regression ejection fraction. We first investigated the possibility that changes in photon self-attenuation within the cardiac chambers cause the observed mathematical characteristics of the cardiac background, B. Self-attenuation was calculated for cylindrical and spherical ventricular models. The results were insensitive to the particular geometry and would have only a small effect on the observed EF. Alternatively, the 'background' may result from extra-ventricular radiation scattering from the heart into the detector. If we assume that B should be proportional to the ventricular scattering volume, Bd = Kd EDC for diastole and Bs = Ks ESC for systole, the background corrected ejection fraction will be BCEF = K UEF + (1-K) where K = (1-Ks)/(1-Kd). This agrees with the form of the empirical regression equation.

Biophysical Phenomena↗

PubMed1990

Thermodilution right ventricular ejection fraction. Catheter positioning effects.

Right ventricular (RV) ejection fractions have been difficult to estimate clinically. It has been demonstrated recently that RV ejection fractions can be calculated by thermodilution techniques using a rapid response thermistor and computer. This method critically depends on adequate mixing of the thermal bolus and sensing of the rapid response thermistor. This study examined the effects of the thermistor position within the pulmonary artery and injectate site within the right atrium on RV thermodilution ejection fraction measurements. Ten pigs were instrumented with a RV thermodilution catheter in the pulmonary artery, an injectate catheter in the right atrium, an atrial-pacing electrode, and a systemic arterial catheter. The RV ejection fractions were determined using thermodilution in two ways: (1) with incremental increases in pulmonic valve to thermistor distance, and (2) with incremental increases in injectate port to tricuspid valve. These measurements were obtained at a paced rate of 107 +/- 1 beats per minute (bpm) and then repeated with pacing-induced tachycardia (140 bpm). The highest RV ejection fraction with the lowest coefficient of variation was with the thermistor 2 cm from the pulmonic valve (50 +/- 2 percent), with a significant decline from this value at 10 cm (42 +/- 4 percent, p less than 0.05). This reduction in RV ejection fraction values with increased pulmonic valve to thermistor distance became more pronounced with tachycardia where a significant decline in RV ejection fraction occurred at 4 cm from the valve when compared with 0 cm (38 +/- 6 percent vs 47 +/- 3 percent, respectively, p less than 0.05). There was no significant change in RV ejection fraction at any injectate port to tricuspid valve distance at the lower heart rate. With tachycardia, however, a significant decline in RV ejection fraction occurred with the injectate port located 7 cm from the tricuspid valve (p less than 0.05). These results demonstrate that RV ejection fractions can be reliably obtained using thermodilution. Positioning of the thermodilution catheter is an important consideration for obtaining optimal RV ejection fraction measurements. Care should be taken to position the catheter with the thermistor a minimal distance from the pulmonic valve and the injectate port within the central body of the right atrium.

Animals↗

PubMed1977

A simple and rapid non-invasive radioisotope method to determine ventricular ejection fractions and cardiopulmonary transit times.

Ejection fractions and cardiopulmonary transit times were measured in 20 hospital patients by means of intravenously injected 99mTc-radiocardiography. Time activity curves from the regions of the whole heart, superior vena cava, right atrium, right ventricle, right lung, left atrium and left ventricle were drawn and analyzed by using the modified gamma function fitting method. The comparison between the ejection fractions determined from the whole heart curves and those from the ventricular curves shows a correlation coefficient of 0.93 for the right ventricle and of 0.90 for the left, although there was a systematic difference between the determinations. The analysis of the single ventricular curves gave about 10% higher values than those obtained from the whole heart curves. The cardiopulmonary parameters measured from the whole heart curves for 16 normal subjects the following results gave: right ventricular ejection fraction=0.57+/-0.08 left ventricular ejection fraction=0.62+/-0.08 pulmonary mean transit time=6.1+/-1.1 heart-beats intracardiac mean transit time=10.5+/-1.8 heart-beats right/left ventricular volume=1.10+/-0.09 These values agree closely with the data accumulated using more elaborate methods. The method presented here is simple to perform, it is non-invasive, time-saving, inexpensive, easy to analyze and suitable for exercising subjects and for bed-side measurements. Data assembly and analysis are easily automated so that results are obtainable immediately after measurements.

Adult↗

PubMed1978

Value of the QRS complex in assessing left ventricular ejection fraction.

The relation between electrocardiographic findings and the angiographic left ventricular ejection fraction and the augmented ejection fraction after a premature ventricular contraction was investigated in 73 patients with documented chronic coronary artery disease. The patients were separated into four groups according to the presence or absence of abnormal Q waves. Twenty-four patients had diaphragmatic myocardial infarction, 21 had anterior myocardial infarction, 15 had both and 13 had no myocardial infarction. There was no statistically significant differences in cardiac index, left ventricular end-diastolic pressure or number of coronary vessels showing critical narrowing in the four groups. The sum of R waves (in mv) in leads aVL, aVF and V1 to V6 (sigmaR) was correlated with the ejection fraction (EF) and the augmented ejection fraction (EFa). EF in percent = 6.6 sigmaR mv + 9.4 (no. =73, r = 0.61); and EFa in percent = 8.6 sigmaR mv + 11.0 (no. = 73, r = 0.77). Among patients with sigmaR of less than 4.0 mv, augmented ejection fraction was less than 0.45 in 73 percent; among patients with sigmaR of 4.0 mv or more the augmented ejection fraction was greater than 0.45 in 93 percent (P less than 0.001). Thus, the sigmaR, calculated from six precordial and two augmented leads in patients with chronic coronary artery disease, correlated with both ejection fraction and augmented ejection fraction. The electrocardiogram in patients with coronary artery disease may prove useful as a simple, readily available and noninvasive guide in the assessment of left ventricular function in patients with coronary artery disease.

Blood Pressure↗

PubMed1991

In vitro validation of a right ventricular thermodilution ejection fraction system.

Right ventricular ejection fraction (RVEF) is used clinically as an index of right ventricular (RV) pump function. Clinical measurements of RVEF are complicated by the need for complex imaging equipment to compute RV volumes. Recently, the use of thermodilution (TD) methods have been suggested as a simplified means to measure RVEF (RVEFTD) in patients using rapid response thermistors. Validation, however, by comparison of RVEFTD and other methods in vivo, is difficult. Accordingly, thermodilution derived EF measurements (EFTD) were compared to known values using an in vitro system, with known ejection fractions (EF) set from 17-78% and stroke rates varying independently from 50-100 strokes/min. EFTD was computed by fitting the downslope of the TD curve to a monoexponential function and computing the time constant of thermal decay. A significant correlation existed between EFTD and actual EF over the entire study (r = 0.96, p less than 0.001). Bias analysis showed that the points were within a 95% confidence interval of +/- 12%. Multivariate analysis showed that stroke rate did not significantly affect TD measurements (r = 0.03, p greater than 0.7). This study demonstrates that TD accurately predicts EF using an in vitro system and appears to be independent of stroke rate. Thus, TD methods may provide an accurate, simple and reliable means to serially measure RVEF in the clinical setting.

Algorithms↗

PubMed1988

Evaluation of magnetic resonance imaging for determination of left ventricular ejection fraction and comparison with angiography.

Left ventricular ejection fraction was measured by magnetic resonance imaging (MRI) and compared with standard monoplane left ventriculography in 46 patients with various cardiac diseases. Two different MRI strategies were used. In 28 patients (group 1), ejection fraction was determined using a single slice comparable with the right anterior oblique projection of the ventriculogram. Comparison of left ventricular ejection fraction yielded a poor correlation between single slice MRI (y) and ventriculography (x) (y = 28.7 + 0.47 x, r = 0.65). In 18 patients (group 2), a multiple contiguous slice MRI technique was used to allow ejection fraction and stroke volume determination by summing up the volumes of ventricular cavity intersections. Regression analysis showed a high correlation between multiple slice MRI (y) and ventriculography (x) (y = 7.2 + 0.88 x, r = 0.98). Also, correlation between MRI right (y) and left (x) ventricular stroke volumes was satisfactory, (y = -12.8 + 1.09 x, r = 0.83). It is concluded that the multiple slice imaging technique in MRI provides an accurate noninvasive means for quantification of left ventricular ejection fraction that can be extended to the determination of left ventricular volume.

Angiocardiography↗

PubMed1976

Serial measurements of left ventricular ejection fraction by radionuclide angiography early and late after myocardial infarction.

The left ventricular ejection fraction was determined serially with radioisotope angiography in 63 patients with acute myocardial infarction. After the peripheral injection of a bolus of technetium-99m, precordial radioactivity was recorded with a gamma scintillation camera and the ejection fraction calculated from the high frequency left ventricular time-activity curve. Since this technique requires no assumptions with respect to left ventricular geometry, it is particularly useful in patients with segmental left ventricular dysfunction. Serial measurements during the first 5 days after hospital admission were made in 50 patients, 30 of whom were studied during the subsequent 2 to 39 months (mean 19.9 months). Late follow-up serial studies were also performed in an additional 13 patients who had only one measurement of the left ventricular ejection fraction during the early postinfarction period. Early after infarction, the left ventricular ejection fraction was normal (more than 0.52) in only 15 of the 63 patients, and averaged 0.52 +/- 0.05 (standard deviation) in the 27 patients with an uncomplicated infarct. The ejection fraction was reduced in 24 patients with mild to moderate left ventricular failure (0.40 +/- 0.05, P less than 0.0001) and in the 12 patients with overt pulmonary edema (0.33 +/- 0.07, P less than 0.0001). In 35 patients the ejection fraction correlated with the mean pulmonary arterial wedge pressure (r = 0.72). In 15 patients with normal left ventricular wall motion by heart motion videotracking, the ejection fraction was significantly higher (0.53 +/- 0.08) than in the 26 patients with regional left ventricular dysfunction (0.41 +/- 0.10, P less than 0.0001). During the early postinfarction period, the left ventricular ejection fraction improved in 55 percent of patients and remained unchanged or decreased in 45 percent. A further increase in the ejection fraction was noted in 61 percent of patients during the late follow-up period. Patients with an initially low or decreasing ejection fraction had a significantly greater incidence of early mortality and left ventricular dysfunction (P less than 0.02) than those whose ejection fraction was normal or improved to normal early after infarction. These data indicate that the ejection fraction is a sensitive indicator of left ventricular function after acute myocardial infarction and that serial measurements are helpful in predicting early mortality and morbidity.

Acute Disease↗

PubMed1986

Influence of atrioventricular synchrony on hemodynamics in patients with normal and low ejection fractions following open heart surgery.

The authors wished to test the hypothesis that atrioventricular synchrony has a relatively greater effect on hemodynamic parameters in postoperative patients with low ejection fractions compared to those with normal ejection fractions. Temporary pacing wires were placed on the right atrium and right ventricle of patients undergoing open heart surgery. Duplicate thermodilution cardiac outputs were determined during atrial pacing and ventricular pacing at 100 beats/min. Mean left atrial and systemic blood pressures were monitored. Thirteen patients with ejection fractions of 45 per cent or less (range 24 to 45%, mean 37.3%) were included in the low ejection fraction group, and 27 patients with ejection fractions of 59 per cent or greater (range 59 to 80%, mean 66.8%) were considered in the normal ejection fraction group. All hemodynamic parameters improved significantly when changing from ventricular pacing to atrial pacing in both the normal ejection fraction group and low ejection fraction group (P less than 0.05). The magnitude of change between the groups showed no significant difference for all parameters except left atrial pressure, which decreased by a greater percentage in the low ejection fraction group with atrial pacing (P less than 0.001). The atrial contribution to hemodynamic enhancement is important in patients with normal and low ejection fraction following open heart surgery. Patients with low ejection fractions do not sustain a relatively greater reduction in cardiac output, stroke volume index, or systemic blood pressure with loss of atrioventricular synchrony when compared to patients with normal ejection fractions.

Cardiac Output↗