ATS
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Add to Personal Folders
Right arrow Download to citation manager
Right arrow Author home page(s):
Edward P. Chen
Hartmuth B. Bittner
Right arrow Permission Requests
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Chen, E. P.
Right arrow Articles by Davis, R. D.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Chen, E. P.
Right arrow Articles by Davis, R. D.
Related Collections
Right arrow Molecular biology
Right arrow Transplantation - heart

Ann Thorac Surg 2001;71:1320-1324
© 2001 The Society of Thoracic Surgeons

Original article: cardiovascular

Myocardial function in hearts with transgenic overexpression of the G protein-coupled receptor kinase 5

Edward P. Chen, MDa, Hartmuth B. Bittner, MD, PhDa, Shahab A. Akhter, MDa, Walter J. Koch, PhDa, R. Duane Davis, MDa

a Division of Cardiothoracic Surgery, Duke University Medical Center, Durham, North Carolina, USA

Accepted for publication April 26, 2000.

Address reprint requests to Dr Chen, Division of Cardiothoracic Surgery, Emory University, 1365 Clifton Rd, Atlanta, GA 30322
e-mail: epchen{at}stanfordalumni.org


   Abstract
Top
 Abstract
Introduction
 Material and methods
 Results
 Comment
 Acknowledgments
 References
 
Background. Chronic heart failure is associated with impairment of the myocardial ß-adrenergic receptor (ß-AR) system. In this study, the effects of G protein–coupled receptor kinase 5 (GRK5) overexpression on myocardial performance were directly assessed in the hearts of transgenic mice using an isolated work-performing murine heart preparation and computerized analysis of functional data.

Methods. A controlled experimental study was performed to evaluate cardiac function in both transgenic mice with a 30-fold overexpression of GRK5 (n = 9, 23 to 29 g) and littermate controls (n = 10, 22 to 29 g). Preload-dependent cardiac output, contractility, stroke work, stroke volume, and heart rate were compared between the two groups.

Results. Significant decreases in preload-dependent cardiac output and contractility were observed in the mice with GRK5 overexpression when compared with control group mice and occurred in association with significant decreases in stroke work and stroke volume. There was no significant difference in the average heart rate between the two groups.

Conclusions. These data suggest that GRK5 upregulation may be partially responsible for alterations in myocardial function in chronic heart failure.


   Introduction
Top
 Abstract
 Introduction
Material and methods
 Results
 Comment
 Acknowledgments
 References
 
Chronic heart failure is characterized by impairment of the myocardial ß-adrenergic receptor system. Previous studies have demonstrated that failing human myocardium contains 50% fewer ß-adrenergic receptors when compared with tissue samples taken from normal hearts [1]. In addition, this finding is known to occur in association with significant alterations in the ß-adrenergic receptor signaling pathways [1, 2].

The G protein–coupled receptor kinases are a family of serine-threonine enzymes containing members that regulate the ß-adrenergic receptor signaling pathway by way of receptor phosphorylation [3]. This leads to diminished ß-adrenergic receptor responsiveness as well as functional uncoupling and is referred to as desensitization [3, 4]. G protein–coupled receptor kinase-5 (GRK5) represents one of six GRK enzymes and is more abundantly expressed in the heart than in tissues of other organs [5]. Transgene overexpression of GRK5 was previously shown to result in ß-adrenergic receptor desensitization in murine hearts [6]; however, the physiologic importance of GRK5 has not been clearly established. Development of transgenic technology represents a powerful tool for elucidating any role GRK5 may play in regulating overall cardiac function. This study was therefore designed to directly assess the effects of GRK5 overexpression on myocardial performance in the hearts of transgenic mice, using an isolated work-performing murine heart preparation and computerized acquisition and analysis of functional data.


   Material and methods
Top
 Abstract
 Introduction
 Material and methods
Results
 Comment
 Acknowledgments
 References
 
Study design and experimental groups
In a controlled, experimental study, nine transgenic mice with myocardial overexpression of the G protein–coupled receptor 5 (GRK5, 4 to 5 months, 23 to 29 g) were evaluated and compared to ten age-matched littermate control mice (CTL, 4 to 5 months, 22 to 29 g) in terms of preload-dependent cardiac function.

The transgenic mice used in this investigation were previously created by Rockman and associates using an expression vector comprised of the murine {alpha}-myosin heavy chain promoter coupled to the entire coding region for bovine GRK5 and have been previously well described [6].

Anesthesia and surgery
The anesthetic regimen and surgical procedure have been previously well described [7]. A clamshell incision was made to expose the mediastinum and pleural cavities, and the thymus was bluntly dissected off the pericardium. The pericardium was opened, and the heart was cold arrested with 4°C Krebs-Henseleit solution and excised from the chest. The aortic root was subsequently cannulated with a 2-mm 20-gauge angiocatheter at the level of the innominate artery.

Experimental protocol
The isolated work-performing (Langendorff) murine heart preparation used for functional data acquisition in this study has been previously well described [7]. Retrograde perfusion was immediately begun with warm Krebs-Henseleit solution and maintained at a pressure of 60 mm Hg to ensure adequate coronary artery perfusion. Following 5 minutes of retrograde perfusion, to allow for temperature equilibration, the left atrium was cannulated in a posterior fashion, and the heart was subsequently perfused in an antegrade (or work performing) manner against an afterload of 55 mm Hg. The minimum afterload required for sufficient coronary flow to ensure normal basal function during antegrade perfusion was previously found to be approximately 50 mm Hg [8, 9].

A preload-dependent work-performing experiment was performed in both GRK5 and CTL hearts according to the following protocol: Preload was gradually increased by raising the height of the antegrade perfusate reservoir, with respect to the left atrium, in 5 mm Hg pressure increments from 5 mm Hg to 25 mm Hg. At each preload level, left atrial pressure, aortic pressure, and aortic flow data were collected over several cardiac cycles by computer acquisition. After data collection at 25 mm Hg, the left atrial pressure was slowly lowered to approximately 10 to 12 mm Hg. Antegrade perfusion was continued for an additional 5 minutes to allow the hearts to recover from any temporary dysfunction that may have potentially been caused by the extreme loading conditions at 20 to 25 mm Hg.

Data acquisition and analysis
All functional and hemodynamic data were digitized on-line at 500 Hz and filtered by a 50 Hz low-pass filter, collected, and stored on a microprocessor (PDP 11/23, Digital Equipment Corp, Maynard, MA). Raw data were analyzed on a VAXstation 3100 computer (Digital Equipment Corp) with software developed in our laboratory which has been previously well described [8]. Measured on-line values included aortic pressure, cardiac output (left ventricular output minus coronary flow), left atrial pressure, and heart rate. Other data used to assess myocardial performance were derived from these measured values and included the contractility (first derivative of pressure with respect to time [dP/dt]), stroke volume, and stroke work.

In both CTL and GRK5 hearts, the average values for each measurement of myocardial performance were calculated from the individual values at preload levels of 5, 10, 15, 20, and 25 mm Hg.

Experimental approval and animal rights
The experimental setup and procedures conformed to the guidelines established by the American Physiologic Society and the National Institutes of Health ("Guide for the Care and Use of Laboratory Animals," National Institutes of Health publication 86 to 23, revised 1985). The experiments were approved by the Duke University Institutional Animal Care and Use Committee.

Statistical analysis
Statistical analysis was performed using commercially available software (SigmaStat Version 2.0, Jandel Scientific Software, San Rafael, CA). To test for a trend in the various indices of myocardial performance over the entire range of increasing preloads, a linear multivariate analysis of repetitive measurements was used. Bonferroni’s method was used to compensate for the increased risk of a type I error with multiple comparisons. Because the analysis of repetitive measurements does not indicate which periods differ, follow-up paired Student’s t tests were also used to compare base line data with increased preload data within each group. Unpaired Student’s t tests were used to compare each measure of myocardial function between the GRK5 and CTL groups. The results are expressed as mean ± standard error of the mean. A difference was considered statistically significant at p less than 0.05.


   Results
Top
 Abstract
 Introduction
 Material and methods
 Results
Comment
 Acknowledgments
 References
 
Gross inspection of animals from both experimental groups revealed no obvious differences in phenotype, breeding, or life span between GRK5 and CTL mice.

After hypothermic arrest and cardiac excision, an average period of 1.6 ± 0.6 minutes was required to cannulate the aorta and connect a heart to the Langendorff apparatus. Mechanical activity was noted almost immediately upon initiation of retrograde reperfusion with warm Krebs-Henseleit solution. External pacing was not used during the experiments.

Preload-dependent myocardial function
Increases in preload levels led to significant increases in cardiac output for both CTL and GRK5 mice (Fig 1). The cardiac output ranged from approximately 3.2 to 5.4 mL/min in GRK5 mice and 4.7 to 7.1 mL/min in CTL mice. The cardiac output of transgenic hearts was significantly lower than the cardiac output of normal hearts at preloads of 5, 10, 15, 20, and 25 mm Hg. In addition, the average cardiac output of GRK5 mice (4.61 ± 0.26 mL/min, p < 0.001) was significantly smaller when compared with the average cardiac output of CTL mice (6.41 ± 0.35 mL/min).



View larger version (16K):
[in this window]
[in a new window]
  		Fig 1. Cardiac output (CO) in both experimental groups is plotted against gradually increasing preload levels at a constant afterload of 55 mm Hg. Increases in preload led to significant increases in CO at all higher preload levels for both control (CTL) and transgenic (GRK5) hearts. The CO of GRK5 mice was significantly decreased in comparison with that of CTL mice. * p < 0.001 versus 5 mm Hg; {dagger} p < 0.05 versus CTL.

 
The contractility also increased significantly as a result of increased preload levels in both groups, although this increase was not as dramatic as the change in cardiac output (Fig 2). Contractility ranged from 1,777 to 2,063 mm Hg/s in GRK5 mice and 2,388 to 2,731 mm Hg/s in CTL mice, and it was significantly lower in transgenic hearts compared with normal hearts across all preload levels. The overall average contractility of GRK5-overexpressed hearts (1,977 ± 99 mm Hg/s, p < 0.001) was significantly lower than the average contractility of control hearts (2,567 ± 71 mm Hg/s).



View larger version (17K):
[in this window]
[in a new window]
  		Fig 2. Contractility (dP/dt) in both experimental groups is plotted against gradually increasing preload levels at a constant afterload of 55 mm Hg. Increases in preload led to significant increases in dP/dt at certain higher preload levels for both control (CTL) and transgenic (GRK5) hearts. The dP/dt of GRK5 mice was significantly decreased in comparison with that of CTL mice. * p < 0.05 versus 5 mm Hg; {dagger} p < 0.05 versus CTL.

 
The stroke work ranged from approximately 403 to 687 dyne * cm in GRK5-overexpressed hearts and 590 to 892 dyne * cm in control hearts. As the preload increased from 5 mm Hg to 25 mm Hg, these values were always significantly decreased in transgenic mice compared with the values in normal mice. Average stroke work of GRK5 mice (584 ± 37 dyne * cm, p < 0.001) was significantly lower than the average stroke work of CTL mice (805 ± 37 dyne * cm). The differences in preload-dependent stroke work between the two groups are displayed in Figure 3.



View larger version (20K):
[in this window]
[in a new window]
  		Fig 3. Stroke work (SW) in both experimental groups is plotted against gradually increasing preload levels at a constant afterload of 55 mm Hg. Increases in preload led to significant increases in SW at all higher preload levels for both control (CTL) and transgenic (GRK5) hearts. The SW of GRK5 mice was significantly decreased in comparison with that of CTL mice. * p < 0.005 versus 5 mm Hg; {dagger} p < 0.05 versus CTL.

 
On average, the heart rates ranged from approximately 420 to 450 beats/min in both experimental groups. There was no significant difference in the heart rates of GRK5 hearts and CTL hearts at all preload levels (Table 1). In addition, the average heart rate of transgenic mice (443 ± 14 beats/min) was not significantly different from the average heart rate of normal mice (427 ± 18 beats/min).


View this table:
[in this window]
[in a new window]
  		Table 1. Preload-Dependent Heart Rate in Isolated Work-Performing Murine Hearts

 
Increases in preload levels also led to significant increases in stroke volume for both control and GRK5 mice (Fig 4). The stroke volume ranged from approximately 7.3 to 12.5 µL in GRK5 mice and 11.2 to 16.9 µL in CTL mice. These values were significantly lower in transgenic hearts compared with those in normal hearts at preloads of 5, 10, 15, 20, and 25 mm Hg. Finally, the average stroke volume of GRK5 mice (10.59 ± 0.71 µL, p < 0.001) was significantly smaller compared with the average stroke volume of CTL mice (15.17 ± 0.73 µL).



View larger version (17K):
[in this window]
[in a new window]
  		Fig 4. Stroke volume (SV) in both experimental groups is plotted against gradually increasing preload levels at a constant afterload of 55 mm Hg. Increases in preload led to significant increases in SV at all higher preload levels for both control (CTL) and transgenic (GRK5) hearts. The SV of GRK5 mice was significantly decreased in comparison with that of CTL mice.* p < 0.001 versus 5 mm Hg; {dagger} p < 0.05 versus CTL.

 

   Comment
Top
 Abstract
 Introduction
 Material and methods
 Results
 Comment
Acknowledgments
 References
 
There are currently six known G protein–coupled receptor kinase (GRK) enzymes, four of which are expressed in the heart: GRK2 (also referred to as ß-adrenergic receptor kinase 1 or ßARK1), GRK3, GRK5, and GRK6 [3, 4]. Previous investigations in both clinical [2, 10] and experimental [11] settings suggest that ßARK1 is a critical in vivo regulator of cardiac function; the importance of other GRK enzymes in myocardial ß-adrenergic receptor signaling and their subsequent effects on physiologic function has not been determined, however. Although increased GRK5 expression has been demonstrated in experimental models of heart failure [12, 13], there are currently no data showing an upregulation of GRK5 in human heart failure. Furthermore, the physiologic effects of this enzyme on myocardial performance have not been fully assessed in an experimental setting.

The isolated work-performing heart (Langendorff) preparation used in this report represents a highly sensitive and well-validated model for evaluating cardiac function in isolated murine hearts [8], and it has previously been applied in experimental investigation [14, 15]. Incorporation of an ultrasonic flow probe, micromanometry, and computerized data acquisition into the apparatus design allows one to not only record heart rates of up to 1500 to 1800 beats/min, but also to analyze extremely sensitive measurements of myocardial performance, such as stroke work [8].

It is acknowledged that a preload-independent estimate for evaluating myocardial performance would have been preferable and clearly superior to the preload-dependent measurements of the current investigation. One such model includes the concept of preload-recruitable stroke work [16], which requires accurate measurement of the volumetric changes occurring in an intact heart throughout the cardiac cycle. Unfortunately, there is no well-described method for assessing ventricular chamber volumes in murine hearts. Currently, such measures are technically limited by the small size of these organs.

In this report, significant differences in cardiac function were observed between the two experimental groups. Cardiac output, contractility, stroke work, and stroke volume were significantly lower in the hearts of mice with myocardial overexpression of G protein–coupled receptor kinase 5 when compared with control mice. No significant differences, however, were observed in the heart rates between transgenic and nontransgenic mice. Thus, transgenic overexpression of GRK5 in isolated murine hearts has a significant impact on myocardial performance, as is evident upon comparison with myocardial performance in normal hearts.

Furthermore, the findings of the present study appear to be consistent with the findings reported in the original description of these same transgenic mice [6]. In their report, Rockman and associates showed that in vitro myocardial signaling in GRK5-overexpressed hearts, both at base line and in response to agonist stimulation, was significantly impaired compared with myocardial signaling in littermate controls [6]. Additional evidence for functional uncoupling of myocardial ß-adrenergic receptors was also demonstrated during in vivo studies, in which the inotropic response to agonist stimulation in GRK5-overexpressed hearts was found to be significantly blunted [6]. Thus, both in vivo cardiac measurements and the measurements in this report with an isolated murine heart preparation demonstrate depressed cardiac function in transgenic mice with myocardial overexpression of GRK5.

It would be interesting to compare myocardial performance in the present GRK5-overexpressed hearts with that in transgenic mice having cardiac overexpression of other GRK enzymes. For instance, the well-established role of ßARK1 as a critical regulator of myocardial function as well as data demonstrating its upregulation in chronic heart failure [2, 10] might warrant such an investigation. Additional insight into the ultimate role of GRK5 in regulating myocardial performance could be gained if the cardiac function of GRK5-overexpressed mice were compared with that in transgenic mice overexpressing ßARK1. Such analysis would, however, require further investigation.

Although no significant difference was found in the heart rates of normal and transgenic mice, the magnitude of these heart rates is quite comparable to in vivo results from several previous reports [6, 8, 11]. In this study, a modification of the original surgical technique, described in the initial report of this model [8], was used to instrument the heart. Previously, the preload cannula had been placed in the left atrium using the appendage. However, this approach necessitated performing a rather lengthy and complicated procedure to ensure that all pulmonary veins were ligated and, in addition, resulted in significant damage to the left atrial appendage and a relatively high proportion of experimental failure [8]. Once in the work-performing mode, the rates of these hearts were significantly lower than those obtained during in vivo catheterization [8].

In the current investigation, the left atrium was cannulated in a posterior fashion, and as a result, the cardiac outputs of wild type hearts in this report ranged from 4.7 mL/min to 7.2 mL/min, which were much higher than the cardiac outputs of 1.0 mL/min to 4.2 mL/min as reported by Bittner and associates [8]. Myocardial performance in murine hearts appears, therefore, to be highly dependent on atrial function, which in turn may require an intact appendage. Posterior cannulation of the left atrium is beneficial not only in terms of preserving heart rate, but also with respect to decreasing atrial trauma and provision of a more stable experimental preparation.

In summary, transgenic overexpression of G protein–coupled receptor kinase 5 has a significant impact on overall myocardial performance in isolated murine hearts. Cardiac output, contractility, stroke work, and stroke volume were significantly decreased in the hearts of mice overexpressing GRK5 when compared with measurements in normal hearts. These data suggest that GRK5 upregulation could potentially play a role in ß-adrenergic receptor uncoupling in the setting of chronic heart failure.


   Acknowledgments
Top
 Abstract
 Introduction
 Material and methods
 Results
 Comment
 Acknowledgments
References
 
Doctors Chen and Akhter are both recipients of a National Research Service Award, fellowship numbers HL09489 (EPC) and HL09436 (SAA).


   References
Top
 Abstract
 Introduction
 Material and methods
 Results
 Comment
 Acknowledgments
 References
 

  1. Bristow M.R., Ginsburg R., Minobe W., et al. Decreased catecholamine sensitivity and ß-adrenergic-receptor density in failing human hearts. N Engl J Med 1982;307:205-211.[Abstract]
  2. Ungerer M., Böhm M., Elce J.S., Erdmann E., Lohse M.J. Altered expression of ß-adrenergic receptor kinase and ß1-adrenergic receptors in the failing human heart. Circulation 1993;87:454-463.[Abstract/Free Full Text]
  3. Lefkowitz R.J. G protein-coupled receptor kinases. Cell 1993;74:409-412.[Medline]
  4. Inglese J., Freedman N.J., Koch W.J., Lefkowitz R.J. Structure and mechanism of the G protein-coupled receptor kinases. J Bio Chem 1993;268:23735-23738.[Free Full Text]
  5. Premont R.T., Koch W.J., Inglese J., Lefkowitz R.J. Identification, purification, and characterization of GRK5, a member of the family of G protein-coupled receptor kinases. J Biol Chem 1994;269:6832-6841.[Abstract/Free Full Text]
  6. Rockman H.A., Choi D.J., Rahman N.U., Akhter S.A., Lefkowitz R.J., Koch W.J. Receptor-specific in vivo desensitization by the G protein-coupled receptor kinase-5 in transgenic mice. Proc Natl Acad Sci USA 1996;93:9954-9959.[Abstract/Free Full Text]
  7. Chen E.P., Bittner H.B., Davis R.D., Folz R.J., Van Trigt P. Extracellular superoxide dismutase transgene overexpression preserves postischemic myocardial function in isolated murine hearts. Circulation 1996;94:II412-II417.
  8. Bittner H.B., Chen E.P., Peterseim D.S., Van Trigt P. A work-performing heart preparation for myocardial performance analysis in murine hearts. Journal of Surgical Research 1996;64:57-62.
  9. Grupp I.L., Subramaniam A., Hewett T.E., Robbins J., Grupp G. Comparison of normal, hypodynamic, and hyperdynamic mouse hearts using isolated work-performing heart preparations. Am J Physiol 1993;265:H1401-H1410.[Abstract/Free Full Text]
  10. Lohse M.J. G-protein-coupled receptor kinases and the heart. Trends Cardiovasc Med 1995;5:63-68.
  11. Koch W.J., Rockman H.A., Samama P., et al. Cardiac function in mice overexpressing the ß-Adrenergic Receptor Kinase or a ßARK inhibitor. Science 1995;268:1350-1353.[Abstract/Free Full Text]
  12. Ping P., Anzai T., Gao M., Hammond H.K. Adenylyl cyclase and G protein receptor kinase expression during development of heart failure. Am J Physiol 1997;273(2 Pt 2):H707-H717.[Abstract/Free Full Text]
  13. Takagi C., Urasawa K., Yoshida I., et al. Enhanced GRK5 expression in the hearts of cardiomyopathic hamsters, J2N-k. Biochem Biophys Res Commun 1999;262(1):206-210.[Medline]
  14. Chen EP, Bittner HB, Davis RD, P. VT, Folz RJ. Physiologic effects of extracellular superoxide dismutase transgene overexpression on myocardial function after ischemia and reperfusion injury. J Thorac Cardiovasc Surg 1998;115:450–9.
  15. Bittner H.B., Chen E.P., Milano C.A., Lefkowitz R.J., Van Trigt P. Functional analysis of myocardial performance in murine hearts overexpressing the human ß2-adrenergic receptor. J Mol Cell Cardiol 1997;29:961-967.[Medline]
  16. Glower D.D., Spratt J.A., Snow N.D., et al. Linearity of the Frank-Starling relationship in the intact heart: the concept of preload recruitable stroke work. Circulation 1985;71:994-1009.[Abstract/Free Full Text]



This article has been cited by other articles:


Home page
 Mol. Pharmacol.Home page
G. W. Dorn II and S. B. Liggett
Mechanisms of Pharmacogenomic Effects of Genetic Variation within the Cardiac Adrenergic Network in Heart Failure
Mol. Pharmacol., September 1, 2009; 76(3): 466 - 480.
[Abstract] [Full Text] [PDF]

Home page
 Circ. Res.Home page
P. W. Raake, L. E. Vinge, E. Gao, M. Boucher, G. Rengo, X. Chen, B. R. DeGeorge Jr, S. Matkovich, S. R. Houser, P. Most, et al.
G Protein-Coupled Receptor Kinase 2 Ablation in Cardiac Myocytes Before or After Myocardial Infarction Prevents Heart Failure
Circ. Res., August 15, 2008; 103(4): 413 - 422.
[Abstract] [Full Text] [PDF]

This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Add to Personal Folders
Right arrow Download to citation manager
Right arrow Author home page(s):
Edward P. Chen
Hartmuth B. Bittner
Right arrow Permission Requests
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Chen, E. P.
Right arrow Articles by Davis, R. D.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Chen, E. P.
Right arrow Articles by Davis, R. D.
Related Collections
Right arrow Molecular biology
Right arrow Transplantation - heart

HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
ANN THORAC SURG ASIAN CARDIOVASC THORAC ANN EUR J CARDIOTHORAC SURG
J THORAC CARDIOVASC SURG ICVTS ALL CTSNet JOURNALS