1. health and fitness
2. disease

Preclinical research
European Heart Journal (2007) 28, 2156–2162
doi:10.1093/eurheartj/ehm263
In vivo model of drug-induced valvular heart disease in
rats: pergolide-induced valvular heart disease
demonstrated with echocardiography and correlation
with pathology
Steven Droogmans1,4,*, Philippe R. Franken2,4, Christian Garbar3,5, Caroline Weytjens1,4,
Bernard Cosyns1,4, Tony Lahoutte2,4, Vicky Caveliers2,4, Miriam Pipeleers-Marichal3,5,
Axel Bossuyt2,4, Danny Schoors1, and Guy Van Camp1,4
1
Department of Cardiology, UZ Brussel, Brussels, Belgium; 2Department of Nuclear Medicine, UZ Brussel, Brussels, Belgium;
Department of Pathology, UZ Brussel, Brussels, Belgium; 4In Vivo Cellular and Molecular Imaging Center (ICMIC), Vrije
Universiteit Brussel (VUB), Brussels, Belgium; and 5Experimental Pathology (EXPA), Faculty of Medicine and Pharmacy, Vrije
Universiteit Brussel (VUB), Brussels, Belgium
3
Received 10 January 2007; revised 18 April 2007; accepted 31 May 2007; online publish-ahead-of-print 18 July 2007
KEYWORDS
Aims Valvular heart disease (VHD), inducing valvular regurgitation, has been described in carcinoid
heart disease and recently in Parkinson’s patients treated with pergolide. The aim of this study was
to develop an in vivo model of drug-induced valvulopathy with pergolide in rats.
Methods and results Thirty male Wistar rats were given daily injections of either pergolide (0.5 mg/kg
intraperitoneally) (n ¼ 8), serotonin (20 mg/kg subcutaneously) (n ¼ 8), or the vehicle only (n ¼ 14) for
5 months. At 20 weeks, echocardiography demonstrated the presence of aortic regurgitation (AR) and/or
mitral regurgitation (MR) in serotonin (86% AR, P ¼ 0.0001; 57% MR, P ¼ 0.006) and in pergolide animals
(67% AR, P ¼ 0.003; 67% MR, P ¼ 0.003) compared with none in placebo. Pulmonary regurgitation (PR)
and tricuspid regurgitation (TR) were found in the serotonin (71% PR, P ¼ 0.19; 100% TR, P ¼ 0.06 vs.
placebo), pergolide (100% PR, P ¼ 0.014; 83% TR, P ¼ 0.35 vs. placebo), and placebo groups (36% PR;
57% TR). Tricuspid regurgitant area ratio (jet/atrium), however, was more severe in the serotonin
[median 26.5 (range 17–42)%; P ¼ 0.02] and pergolide animals [32 (17–39) %; P ¼ 0.03] compared with
placebo [12.5 (5–33)%]. We found a good correlation between valvular regurgitation and histologically
assessed valvular thickness. Histological examination revealed the presence of diffusely thickened and
myxoid aortic, mitral, and tricuspid valves in serotonin and pergolide animals as seen in VHD.
Conclusion We demonstrated, for the first time, that long-term pergolide administration led to VHD in
rats. This small animal model will permit further in vivo investigation of drug-induced valvulopathies.
Introduction
During the last decade, several drugs have been identified
to cause cardiac valvulopathy. Ergot derivatives (ergotamine,
methysergide) and appetite-suppressants (fenfluramine)
were the first drugs described to cause valvular heart
disease (VHD).1,2 This entity is characterized by thickening
of the leaflets and thickening and shortening of the subvalvular apparatus, finally leading to valvular insufficiency.
Recently we described the occurrence of VHD in 26 of 78
patients with Parkinson’s disease treated with pergolide.3
The involvement of ergot-derived dopamine agonists (pergolide, cabergoline) in the development of VHD is still an
important topic of investigation.4,5
* Corresponding author.
Tel: þ32 2 477 6010; fax: þ32 2 477 6840.
E-mail address: steven_droogmans@yahoo.com
Drug-induced VHD has a histological resemblance with the
carcinoid syndrome showing myxoid valvular changes, fibrosis and extracellular deposits of proliferative plaque-like
material containing fibroblasts, myofibroblasts, and smooth
muscle cells.2,6 Although many pathophysiological mechanisms remain to be elucidated, it is clear that serotonin
[5-hydroxytryptamine (5-HT)] plays a central role. Cell
culture studies indicated the mitogenic effects of 5-HT on
different cell types such as fibroblasts7 and aortic smooth
muscle cells.8–10 A recent animal study confirmed the development of carcinoid like valvular deposits in rats after
3 months of daily subcutaneous serotonin injections.11
Deficiency of the 5-HT transmembrane transporter in mice
led to valvular fibrosis, providing further support for a
direct link between 5-HT and cardiac valvulopathy.12 Functional recombinant receptor assays suggested that the
effects of these valvulopathic drugs are mainly mediated
& The European Society of Cardiology 2007. All rights reserved. For Permissions, please e-mail: journals.permissions@oxfordjournals.org
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Echocardiography;
Pathology;
Drugs;
Small animals;
Valves
Drug-induced valvular heart disease in rats
2157
by the 5-HT2b receptor.13–15 These data also demonstrated
that pergolide potently activates the 5-HT2b receptor.14,16,17
Until now, most of the studies were performed in vitro to
evaluate the response of valvular and cardiac cells to 5-HT,
ergot-related drugs, and fenfluramine derivates. Therefore,
important questions such as dose dependency, reversibility,
and possible protective effects of antagonists remain unanswered. Hence, an in vivo model of drug-induced VHD is
needed for future studies.
The aim of this study was to develop and characterize an
in vivo model of drug-induced valvulopathy. For that
purpose we studied the effect of daily injections of pergolide compared with serotonin and placebo on the cardiac
valves of male Wistar rats using echocardiography. At the
end of the study, the animals were sacrificed and the clinical
data were compared with the histological findings.
with 2D colour Doppler or continuous-wave Doppler, regurgitation
was considered absent. The severity of the regurgitant aortic flow
was assessed as the colour-Doppler ratio of regurgitant jet width
to the left ventricular outflow tract diameter. For the mitral and tricuspid valve, the regurgitant area ratio (jet/atrium) was calculated
in the view with the largest colour Doppler signal (long axis or four
chamber view). The pulmonary regurgitant flows were coded as
present or absent in the short-axis view.
Left ventricular chamber diameter in end-systole (LVESD) and
end-diastole (LVEDD), left ventricular anterior wall thickness in endsystole and end-diastole, and left ventricular posterior wall
thickness in end-systole and end-diastole, as well as left ventricular
fractional shortening (FS% ¼ [(LVEDD2LVESD)/LVEDD] 100) were
determined from the M-mode tracings in a short-axis view
(average of three consecutive cycles) at the level of the papillary
muscles.
Methods
The animals were sacrificed 2 weeks after the last injections. The
hearts were weighted and fixed in formalin for 2 h. Then they
were embedded in paraffin, cut in an axial plane (from basis to
apex) and stained with hematoxylin and eosin and alcian blue for
glycosaminoglycans. Additional step sections, ranging from 1 to 3
(approximately 100 mm between sections) were carried out for
those heart sections without valves. Extreme care was taken in sectioning the heart so that the valves were mainly cut transversely
(with the attachment sides of the leaflets visible on both ends of
the valve). Morphometry was performed by digital image analysis
using a PC digital image camera (Digital Sight DS-5M, Nikon Corp,
Japan) mounted on an Axiolab Zeiss light microscope (Carl Zeiss
Corp, Germany) with a 10 objective (Acroplan, Zeiss). We used
the NIH Image program (Image-J 1.35 d, Nation Institutes of
Health, Bethesda, USA). The program was calibrated with a graduated slide. Microscopic images were used to evaluate blindly the
cardiac valves and cardiomyocytes. The maximum thickness of
every valve present was measured. The width of at least ten cardiomyocytes was measured on the left ventricle of each section.
Study design
Animals handling
During the whole study, the animals were housed in stainless steel
cages with sawdust bedding. They were kept at an average room
temperature of 248C, a relative humidity of 50%, and a 12 h day/
night cycle. Food (rat maintenance diet, SAFE, France) and water
were provided at libidum.
Drugs preparation and administration
Serotonin (5-HT Creatinin Sulphate Complex, Sigma-Aldrich) was dissolved in physiological saline at a concentration of 20 mg/mL. In
order to avoid skin lesions like subcutaneous bleedings and traumatic
wounds, the injection side was changed daily. An equal volume of
physiological saline (1 mL/kg) was given to the placebo rats.
Pergolide mesylate (Sigma-Aldrich) was prepared in a 10% alcoholic solution at a concentration of 0.5 mg/mL. An equal volume
of a 10% ethanol solution (1 mL/kg) was given to the placebo rats.
The treatment identity of the rats was hidden during echocardiography and pathological evaluation.
Echocardiography
Ten minutes before imaging, the rat was anesthetized with 50 mg/kg
sodium pentobarbital intraperitoneally. Subsequently the anterior
chest wall was shaved and the rat was placed in left lateral decubitus on a wooden bench in order to obtain optimal image quality
and views. ECG electrodes were fixed on the paws.
A Vivid 7 Pro system (GE Medical Systems, Milwaukee, WI, USA)
with a 10 MHz neonatal probe (10S) was used. Images and loops
were stored digitally for post-test analysis. The image sector was
kept narrow in order to get a maximal frame rate. When necessary,
cineloop speed was reduced for optimal jet evaluation. Regurgitant
jets were assessed visually with 2D colour Doppler and continuouswave Doppler in the parasternal short and long axis, apical three
and four chamber views. If no retrograde flow was detectable
Statistical analysis
Data are expressed as median with range or interquartile range.
Comparison between groups were performed by using the Mann–
Whitney U-test and Fisher’s exact test. A cut-off value for valvular
thickness and correlation between valvular thickness and regurgitation was calculated using receiver operating characteristic (ROC)
analysis. Data were not corrected for multiple comparisons. All
P-values were calculated two-tailed. A value of P , 0.05 was considered significant. Statistical analysis was done with GraphPad
Prism (version 4.03, San Diego, CA, USA).
Results
There were no differences between the two placebo groups
for all measurements. In the following part, the placebo
data were pooled for further analysis.
Clinical signs
The serotonin injections induced flushing, loose stools, drowsiness, and tachypnea persisting for several hours after the
injections. The clinical signs of the pergolide injections
were most pronounced in the first 2 weeks of the study and
included hyperactivity, poor grooming, aggressive behaviour,
and increased gnawing activity. Three treated animals died
during follow-up (one serotonin at 10 weeks immediately
after anaesthesia and two pergolide rats were found dead
at 14 and 19 weeks without identifiable cause at necropsy).
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Thirty male Wistar Unilever rats (Harlan, the Netherlands) (350+3 g;
11 weeks) were randomized into two placebo-controlled arms. In
the first arm, eight rats received daily one injection of serotonin
(20 mg/kg) subcutaneously and seven rats received the vehicle
only. In the second arm, eight rats received daily one injection of
pergolide (0.5 mg/kg) intraperitoneally and seven rats the
vehicle only. An echocardiographic evaluation was performed at
baseline and at 10 and 20 weeks, followed by necropsy and histological examination of the heart. This study protocol was approved
by the Ethics Committee of the Vrije Universiteit, Brussel.
Histopathology
2158
S. Droogmans et al.
Table 1 Evolution of the valvular regurgitations of the placebo, serotonin- and pergolide-treated animals at 10 and 20 weeks
10 weeks
N
Tricuspid regurgitation (%)
Pulmonary regurgitation (%)
Mitral regurgitation (%)
Aortic regurgitation (%)
20 weeks
Placebo
Serotonin
Pergolide
Placebo
Serotonin
Pergolide
14
36
7
0
0
7
71
57*
29
0
8
63
13
25
0
14
57
36
0
0
7
100
71
57**
86***
6
83
100*
67**
67**
Percentage of rats with valvular regurgitation. *P , 0.05, **P , 0.01, and ***P , 0.001, compared with placebo of the same age.
Echocardiography
M-mode measurements
A significant increase in LVEDD and a decrease in FS were
observed at 20 weeks in the pergolide but not the serotonin
treated animals (Table 2). Both groups had a diminished left
ventricular wall thickness compared with placebo.
Pathology
Post-mortem measurements
At sacrifice, serotonin- and pergolide-treated animals had a
lower body weight [400 (362–468) g; P ¼ 0.0003] and [467
(435–517) g; P ¼ 0.001], respectively, compared with the
placebo group [571 (483–626) g]. The heart to body weight
ratio was higher in the serotonin group [3.63 (3.12–3.89)
mg/g; P ¼ 0.0007] and in the pergolide group [3.17 (2.78–
3.50) mg/g; P ¼ 0.07] compared with the placebo group
[2.79 (2.57–3.56) mg/g].
Figure 1 (A) Apical three chamber view in a pergolide rat at 20 weeks with
aortic regurgitation (green arrow). (B) Parasternal long-axis view in a pergolide rat at 20 weeks with mitral regurgitation (green arrow). LA, left atrium;
LV, left ventricle; AR, aortic root.
Valvular pathology
Histological examination revealed the presence of thickened
aortic, mitral, and tricuspid cusps in the serotonin- and
pergolide-treated animals (Figure 2). Moreover, regurgitant
valves were thicker on histology [192 (69–405) mm; P ¼
0.0003] compared with non-regurgitant valves [106 (61–
278) mm]. Using ROC analysis, a good correlation was
found between echocardiography and pathology (AUC 0.76;
P ¼ 0.0003) with 161 mm as cut-off for a thickened pathological valve.
Valvular thickening was because of myxoid change in
the sponge layer of the leaflet (Figure 3). These
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Valvular analysis
Every valve was visualized in all animals during the study. A
baseline echocardiography was performed before the start
of the injections. There were no valvular abnormalities.
The occurrence of valvular regurgitation in the different
groups during follow-up is shown in Table 1. At 20 weeks,
aortic regurgitation (AR) was present in six (86%; P ¼
0.0001) animals of the serotonin group and in four (67%;
P ¼ 0.003) of the pergolide group (Figure 1). The median
colour-Doppler ratio of regurgitant jet width to the left
ventricular outflow tract diameter was 35.5 (24–43) and
25 (21–50), respectively. AR was not found in the placebo
group.
Mitral regurgitation (MR) was also not found in the placebo
group. At 20 weeks, MR was present in four (57%; P ¼ 0.006)
serotonin and four (67%; P ¼ 0.003) pergolide-treated
animals (Figure 1B). The median regurgitant area ratio
were 16.5 (8–36) and 25 (14–31)%, respectively.
Tricuspid regurgitation (TR) and pulmonary regurgitation
(PR) were found in both the placebo and treated animals.
However, TR was found in 57% of placebos, in all serotonins
(P ¼ 0.06), and in 83% pergolide rats (P ¼ 0.35). PR was
present in 36% of placebos, in 71% of serotonins (P ¼
0.19), and in all pergolide rats (P ¼ 0.014). In addition,
the TR was more severe in the serotonin group [regurgitant
area ratio 26.5 (17–42)%; P ¼ 0.02] and in the pergolide
group [regurgitant area ratio 32 (17–39)%; P ¼ 0.03] compared with the placebo group [regurgitant area ratio 12.5
(5–33)%].
Drug-induced valvular heart disease in rats
2159
Table 2 M-mode parameters of the left ventricle (LV) (parasternal short-axis view) of the placebo animals and the treated animals at 10
and 20 weeks
10 Weeks
N
Anterior wall diastole (cm)
Inferior wall diastole (cm)
LV enddiastolic diameter (cm)
LV endsystolic diameter (cm)
Fractional shortening (%)
20 Weeks
N
Anterior wall diastole (cm)
Inferior wall diastole (cm)
LV enddiastolic diameter (cm)
LV endsystolic diameter (cm)
Fractional shortening (%)
Placebo
IQR
Serotonin
IQR
P-value
Pergolide
IQR
P-value
14
0.20
0.18
0.71
0.45
40
0.17–0.23
0.17–0.22
0.68–0.76
0.39–0.47
38–45
7
0.21
0.17
0.73
0.42
42
0.17–0.24
0.16–0.19
0.65–0.76
0.38–0.45
36–44
0.79
0.26
0.91
0.68
0.48
8
0.19
0.17
0.73
0.45
38
0.17–0.20
0.16–0.18
0.69–0.75
0.41–0.48
34–40
0.39
0.09
0.89
0.56
0.19
14
0.20
0.20
0.72
0.43
41
0.18–0.22
0.19–0.23
0.69–0.79
0.39–0.47
37–44
7
0.17
0.16
0.75
0.44
40
0.16–0.18
0.15–0.18
0.72–0.80
0.40–0.48
36–52
0.01
0.004
0.26
0.65
0.91
6
0.17
0.16
0.80
0.52
35
0.15–0.19
0.15–0.17
0.73–0.85
0.48–0.55
32–39
0.01
0.008
0.03
0.009
0.02
Values are expressed as median and interquartile range (IQR). P-values are compared with placebo of the same age.
Left ventricular pathology
The left ventricular cardiomyocytes were hypertrophic in
both serotonin- [width 15.4 (12.4–17.4) mm; P ¼ 0.01]
and pergolide-treated animals [16.1 (13.7–18.1) mm; P ¼
0.003] compared with placebo-treated animals [12.4
(10.5–14.5) mm]. Macroscopically, left ventricular cavities
were more dilated in both the serotonin and pergolide
groups.
Discussion
In this study, we presented and characterized for the first
time an in vivo animal model of pergolide-induced valvulopathy. We showed that long-term pergolide administration
led to VHD in these rats. This was demonstrated by serial
in vivo echocardiographic assessment of valvular changes
during the course of the experiment. Moreover, there was
an excellent correlation between these echocardiographic
findings and histological analysis. We finally describe the
pathological lesions in this model of drug-induced
valvulopathy.
Drug-induced valvulopathy was demonstrated by means of
echocardiographic illustration of valvular regurgitations. AR
and MR were found only in the pergolide- and serotonininjected animals, whereas PR and TR were also present in
the placebo group. This illustrates that regurgitations are
also present in normal rats and one should take this fact
into account when studying VHD in rodents. Right-sided
valvular regurgitations could be a physiological manifestation of the natural aging process of rats and might be
Figure 2 Scale bar represents the median of the maximum thickness of each valve (measured on the digital microscopic images) of the placebo, serotonin, and
pergolide groups at 20 weeks. Thickness of the values is in micrometre, with interquartile range. N, number of valves analysed, *P , 0.05.
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glycosaminoglycans deposits were also observed in the
placebo group, but were smaller and localized at the distal
free edge of the valve leaflet. In contrast, the serotoninand pergolide-treated animals showed diffuse thick myxoid
changes throughout the valves reaching the base of the
cusps. Several areas of chondroid metaplasia were noted
at the basal septum between the attachment sites of the
aortic and mitral leaflets in the serotonin- (50%; P ¼ 0.28),
pergolide- (60%; P ¼ 0.24), and placebo-treated animals
(18%). True valvular fibrosis with dense collagen was not
observed.
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S. Droogmans et al.
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Figure 3 Photomicrographs of the aortic valve. Placebo rat (A) with limited myxoid change of the distal free end of both leaflets (black arrow). Diffuse myxoid
thickening of the spongy layer reaching the base of the cusps (black arrows) of a (B) serotonin-treated animal and (C and D) pergolide-treated animal. Chondroid
metaplasia is present at the attachment sides of the aortic valve (white arrows, insert) in both treated animals. Scale bar is 250 mm, original magnification 40,
insert 200, HES (A–C) and Alcian blue (D).
more pronounced under anaesthesia. More research is
needed to clarify this observation. On the other hand, this
can explain the absence of significant difference regarding
TR in the pergolide-treated animals compared with controls
by echocardiography. However, the severity of TR was more
pronounced in both pergolide- and serotonin-treated
animals compared with placebo. This might be because of
the higher pulmonary resistance in these rodents.18 Moreover, histological analysis confirmed the tricuspid involvement in both pergolide- and serotonin-treated animals.
This was not the case for the pulmonary valves. Although
speculative, this can be explained by the more difficult
imaging of the pulmonary valves by echocardiography and
pathology in clinical and preclinical research in
rodents.11,19 On the other hand, the pulmonary valve
might present a different density of the 5-HT2b receptor.
This needs to be addressed in future research. As in our
clinical study with pergolide, left- and right-sided heart
valves were affected.3 Carcinoid heart disease is
mainly limited to the right side since serotonin is broken
down by monoaminooxidase in the lungs, but the left
side can also be affected.20 In our study, left-side
involvement was also found in the serotonin-treated
animals and is probably because of the relatively high
dosage injected. Similar findings were observed in the
study of Gustaffson.11
Our study also demonstrated an excellent correlation
between echocardiographic valvular regurgitation and valvular thickness as measured by histological examination.
With exception of the pulmonary valve, all valves were significantly thicker in the pergolide and serotonin groups.
Since no data exist about normal values of valvular thickness
in rats, we calculated 161 mm as a best cut-off for a pathologically thickened valve in this study.
The histological lesions consisted of myxoid thickening of
the valvular sponge layer in this animal model as observed
by others.11,21,22 These endocardial myxoid changes have
been described in normal aging rats, but the deposits are
smaller and mainly situated at the distal free edges of the
valvular leaflets.19 On the other hand, 5 HT2B receptor
agonists such as pergolide14 could lead to an increased
biosynthesis of collagen and glycoaminoglycans which
accumulate in the valvular sponge layer in a diffuse
pattern.10
Drug-induced valvular heart disease in rats
Conclusions
We described the first pergolide-induced valvulopathy
animal model and proved also that in vivo ultrasound
imaging of VHD is feasible and correlates well with pathology. This opens the door towards research in the field of
drug-induced VHD for answering important remaining questions such as dose-dependency, reversibility and influence
of inhibitory drugs.
Acknowledgements
The authors wish to thank Nicole Buelens and Ce
´line Degaillier for
their technical support and assistance in preparing the histological
sections. Steven Droogmans has received a scholarship from the
‘Fonds voor Wetenschappelijk Onderzoek Vlaanderen (FWO)’ for
this work.
Conflict of interest: none declared.
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Besides these typical histological findings, we also
describe the presence of chondroı¨d metaplasia at the
attachment sides of the aortic and mitral valves. This
could be an age-related manifestation aggravated by overstimulation of the 5-HT receptor as reported in studies of
human calcified valves.23,24 This phenomenon was also
described in 5-HT transmembrane transporter knockout
mice.12 In these mice, fibrotic lesions were found in the
valves and in the heart with left ventricular dilatation and
decreased fractional shortening. Although we did not
observe valvular and myocardial fibrosis, the pergolide
group also developed a pronounced, dilated cardiomyopathy
with thinning of the left ventricular wall and decreased fractional shortening. Chronic AR and MR might lead to volume
overload and eventually to the development of a dilated
cardiomyopathy, but this might also be because of a direct
toxic effect on the cardiomyocytes although we did not
find necrosis of the cardiomyocytes. In the serotonin
group, the left chamber dilatation was not so marked. In
addition, histological examination showed hypertrophy of
the cardiomyocytes in both groups, possibly reflecting the
5-HT receptor overstimulation, as described by others.25,26
Medications interacting with the serotonergic system are
becoming increasingly common in clinical practice, i.e. in
the treatment of migraine (5-HT1A receptor agonists),
chemotherapy-induced emesis (5-HT3 receptor antagonists),
irritable bowel syndrome (serotonin agonists and antagonists), depression (selective serotonin reuptake inhibitors),
and Parkinson’s disease (pergolide and cabergoline).4,5
With the development of this model of pergolide-induced
valvulopathy, it may also be possible to study other specific
drug-induced diseases for preclinical research, including
drugs with a low affinity for the 5-HT receptor. This in vivo
animal model permits to answer urgent questions in the
field of drug-induced valvulopathies. Exposure to higher
cumulative doses of serotonergic drugs could lead to more
pronounced valvular lesions, whereas recovery of valvular
function might occur after cessation of these drugs. Furthermore, the addition of 5-HT receptor antagonists could
reduce or inhibit the development of valvular lesions.
These issues will require further investigation. Because
echocardiography showed to be a very useful tool to study
in vivo drug-induced valvulopathy in this study, it will be
the method of choice for the serial assessment of cardiac
valves during these interventions.
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20. Simula DV, Edwards WD, Tazelaar HD, Connolly HM, Schaff HV. Surgical
pathology of carcinoid heart disease: a study of 139 valves from 75
patients spanning 20 years. Mayo Clin Proc 2002;77:139–147.
21. Van Camp G, Flamez A, Cosyns B, Goldstein J, Perdaens C, Schoors D.
Heart valvular disease in patients with Parkinson’s disease treated with
high-dose pergolide. Neurology 2003;61:859–861.
22. Horvath J, Fross RD, Kleiner-Fisman G, Lerch R, Stalder H, Liaudat S,
Raskoff WJ, Flachsbart KD, Rakowski H, Pache JC, Burkhard PR,
Lang AE. Severe multivalvular heart disease: a new complication of the
ergot derivative dopamine agonists. Mov Disord 2004;19:656–662.
23. Mohler ER III, Gannon F, Reynolds C, Zimmerman R, Keane MG, Kaplan FS.
Bone formation and inflammation in cardiac valves. Circulation 2001;
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24. Levy RJ. Serotonin transporter mechanisms and cardiac disease. Circulation 2006;113:2–4.
25. Jaffre F, Callebert J, Sarre A, Etienne N, Nebigil CG, Launay JM,
Maroteaux L, Monassier L. Involvement of the serotonin 5-HT2B receptor
in cardiac hypertrophy linked to sympathetic stimulation: control of
interleukin-6, interleukin-1beta, and tumor necrosis factor-alpha cytokine production by ventricular fibroblasts. Circulation 2004;110:
969–974.
26. Nebigil CG, Jaffre F, Messaddeq N, Hickel P, Monassier L, Launay JM,
Maroteaux L. Overexpression of the serotonin 5-HT2B receptor in heart
leads to abnormal mitochondrial function and cardiac hypertrophy. Circulation 2003;107:3223–3229.
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