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Original Contribution
Correlation Between Estimated Ejection Fraction Measured by Echocardiography with Ejection Fraction Estimated by Cardiac Catheterization in Patients Awaiting Cardiac Transplantation
December 2010
ABSTRACT: Background. Ejection fraction measurement is an integral part of pre-heart transplant evaluation. In the clinical arena, the correlation and agreement between ejection fraction (EF) measured by echocardiography versus catheterization in pre-heart transplant patients has not been studied. Methods. Data on all patients evaluated for heart transplantation at our program between 2003 and 2005 (n=64) were retrospectively reviewed. Patients with both transthoracic echocardiography (with interpretable images) and left heart catheterization with ventriculography were included (n=63, mean time difference 2.2 days, median 2 days). We correlated reported echocardiographically estimated EF with that estimated EF by left heart catheterization. Results. Mean estimated EF by ventriculography was 21.2 ± 10.0 in comparison to 22.8 ± 10.5 by echocardiography. The correlation between echocardiographic and measured EF was poor in the total population (r2 = 0.36, p Conclusions. Among patients referred for heart transplant evaluation, there is a poor agreement and correlation between echocardiographically estimated EF and estimated EF by ventriculography. However, this correlation is strong in patients with ischemic cardiomyopathy. The cause of this discrepancy is not known and warrants further investigation.
J INVASIVE CARDIOL 2010;22:571–573
Key words: transplantation; cardiac dysfunction; cardiac transplant; left ventriculography;
transplant evaluation
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Cardiac transplantation is the treatment of choice for many patients with end-stage heart failure who remain symptomatic despite optimal medical therapy. Better understanding of immune mechanisms in allograft rejection, development of new immunosuppressive regimens, improved postoperative follow-up care and new donor organ preservation and transport systems, has improved survival rates for heart transplant recipients. Data from the International Society for Heart and Lung Transplantation (ISHLT) registry have shown that the overall graft half-time (time at which 50% of those transplanted remain alive, or median survival) has been increasing steadily, currently at 10 years, with a half-life of 13 years for those surviving the first year.1
The primary objective of heart transplantation is to improve survival and functional capacity. Consequently, patients are listed for transplant only when the recipient is expected to live longer with a better quality of life when compared with continuing medical (or other non-transplant) therapy. Evaluation of candidates for heart transplant is a rigorous process that involves a battery of non-invasive and invasive tests. Although peak VO2 has often been the major factor used to guide the selection of patients, a single variable does not provide an optimal risk profile. As a result, several risk models have been developed that use factors identified in multivariable survival analysis to establish a risk score for prognosis in these patients,2–6 prominent ones being the Heart Failure Survival Score (HFSS) and more recently, the Seattle Heart Failure Model.
Ejection fraction (EF) is an important variable of these risk models and an integral part of the pre-transplant evaluation. The correlation of EF as estimated by transthoracic echocardiography (TTE) versus left-heart catheterization (LHC) has been performed in several patient populations.7–14 The studies have mostly focused on patients being evaluated for coronary artery disease or those who had suffered acute myocardial infarction. The correlation and agreement between EF measured by echocardiography versus catheterization in pre-heart transplant patients has not been studied. We sought to investigate the correlation between these two modalities among heart transplant candidates, in the clinical setting.
The correlation of EF between the two studies was poor in the total population (r2 = 0.36, p 
correlation (r = 0.70) between echocardiographic and angiographic values in a large community-based clinic. Similarly Godkar et al12 also reported a strong correlation of EF between these two modalities (r = 0.96). In one of the recently published studies, Joffe et al7 reported a correlation of r = 0.73 between these two modalities. In their study, the median time between the tests was 2.4 days. The study was done in patients with acute myocardial infarction. In our study, patients with ischemic cardiomyopathy showed good agreement between LHC and TTE estimated EF (r = 0.75). This finding in agreement with Joffe et al9 study involving mostly patients with ischemic cardiomyopathy.
One distinct characteristic in patients undergoing heart transplant is that the mean ejection fraction among the study group is expected to be lower than the study group with acute myocardial infarction. This is well demonstrated by a lower mean ejection fraction in our study as compared to the other studies. This provides a unique opportunity to compare EF between two modalities in patients with very low EF.
The other interesting finding in our study was the poor correlation in non-ischemic cardiomyopathy patients using these two modalities for EF measurement. The cause of the discrepancy between ischemic and non-ischemic cardiomyopathy needs to be validated in future studies.
The mean time difference between the two modalities in our patients was 2.2 days. This short interval suggests that EF recovery or deterioration is not responsible for our finding of poor correlation. This was also reported by Joffe et al where they performed a subset analysis of patients undergoing the two studies on the same day and did not find any significant difference in their results.
Based on our results, we recommend that ejection fraction estimation or measurement has limitations using only one method such as echocardiography or ventriculography alone. Physicians should carefully review data in regards to ejection fraction themselves in order to have a final estimation of EF particularly when discrepancies exist between reported ejection fractions using different modalities.
Study limitations. An important limitation of this study is the retrospective design and the small number of patients. Angiographic reported EF was done per visual estimation and not using objective methods. However, this is a real world in the majority of centers. Objective measurement of EF in the catheterization laboratory is time consuming and has its own limitations.
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From the *Banner Estrella Medical Centre, Phoenix, Arizona; §University of Arizona Sarver Heart Center, Tucson, Arizona; and £Southern Arizona VA Health Care System, Tucson, Arizona.
The authors report no conflicts of interest regarding the content herein.
Manuscript submitted June 2, 2010, provisional acceptance given July 27, 2010, final version accepted August 3, 2010.
Address for correspondence: Mohammad Reza Movahed, MD, Professor of Medicine, Southern Arizona VA Health Care System, Director of Heart Transplantation, University of Arizona Sarver Heart Center, Department of Medicine, Division of Cardiology, 1501 N. Campell Avenue, Tucson, AZ 85724–5037. E-mail: rmova@aol.com
Methods
Following institutional review board approval, we retrospectively reviewed data on all patients for heart transplant at our program between 2003 and 2005. Patients with both transthoracic echocardiography (with interpretable images) and left heart catheterization (LHC) performed were included in the analysis. The patients’ medical records, echocardiography and cardiac catheterization reports were analyzed. Standard M-mode, 2-dimensional and Doppler echocardiographic evaluations were performed using the commercially available General Electric Vivid (Milwaukee, Wisconsin) and Phillips M2424A (Andover, Massachusetts) systems. In the cardiac catheterization laboratory, patients underwent right and left heart catheterization. Left ventriculogram was performed as a part of the LHC. Statistical analysis. Data have been expressed as mean ± standard deviation or standard error of the mean. The correlation of EF as measured by TTC versus LHC was carried out using Pearson’s correlation coefficient. A p-value Results Sixty-three patients had both interpretable TTE images and LHC data. The mean time difference between the two studies was 2.2 days and the median 2 days. Mean estimated EF (± standard deviation) by left ventriculogram was 21.2 ± 10.0 in comparison to 22.8 ± 10.5 by echocardiography (Table 1).
The correlation of EF between the two studies was poor in the total population (r2 = 0.36, p Discussion
In this study of patients referred for heart transplant, we found an overall poor correlation of EF between LHC and TTE. Studies comparing these two modalities to estimate the ejection fraction have been reported, however such a comparison in transplant patients has not been reported so far. Most of these studies have focused on study population in the setting of acute myocardial infarction. Habash-Bseiso et al7 reported significant
correlation (r = 0.70) between echocardiographic and angiographic values in a large community-based clinic. Similarly Godkar et al12 also reported a strong correlation of EF between these two modalities (r = 0.96). In one of the recently published studies, Joffe et al7 reported a correlation of r = 0.73 between these two modalities. In their study, the median time between the tests was 2.4 days. The study was done in patients with acute myocardial infarction. In our study, patients with ischemic cardiomyopathy showed good agreement between LHC and TTE estimated EF (r = 0.75). This finding in agreement with Joffe et al9 study involving mostly patients with ischemic cardiomyopathy.
One distinct characteristic in patients undergoing heart transplant is that the mean ejection fraction among the study group is expected to be lower than the study group with acute myocardial infarction. This is well demonstrated by a lower mean ejection fraction in our study as compared to the other studies. This provides a unique opportunity to compare EF between two modalities in patients with very low EF.
The other interesting finding in our study was the poor correlation in non-ischemic cardiomyopathy patients using these two modalities for EF measurement. The cause of the discrepancy between ischemic and non-ischemic cardiomyopathy needs to be validated in future studies.
The mean time difference between the two modalities in our patients was 2.2 days. This short interval suggests that EF recovery or deterioration is not responsible for our finding of poor correlation. This was also reported by Joffe et al where they performed a subset analysis of patients undergoing the two studies on the same day and did not find any significant difference in their results.
Based on our results, we recommend that ejection fraction estimation or measurement has limitations using only one method such as echocardiography or ventriculography alone. Physicians should carefully review data in regards to ejection fraction themselves in order to have a final estimation of EF particularly when discrepancies exist between reported ejection fractions using different modalities.
Study limitations. An important limitation of this study is the retrospective design and the small number of patients. Angiographic reported EF was done per visual estimation and not using objective methods. However, this is a real world in the majority of centers. Objective measurement of EF in the catheterization laboratory is time consuming and has its own limitations.
Conclusion
In our retrospective analysis of patients referred for heart transplant, there was a poor correlation of EF estimated by TTE vs. LHC. However, patients with ischemic cardiomyopathy showed a good correlation between the two modalities whereas those with non-ischemic cardiomyopathy showed a poor correlation. The cause of this discrepancy is not clear and warrants further investigation. Based on our results, in the clinical setting, EF estimation in pre-transplant patients should not rely on one method exclusively, particularly in patients with non-ischemic cardiomyopathy.References
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