CARDIOVASCULAR JOURNAL OF AFRICA • Vol 24, No 1, January/February 2013
AFRICA
281
revealed a heterozygous mutation (Asn5311e) in CALM1 gene
encoding for calmodulin, the intracellular calcium sensor and signal-
ling protein. When screening a collection of 61 arrhythmia samples
negative for RYR2 mutations, a second
de novo
missense mutation
(Asn97Ser) in an Iraqi patient with CPVT-like disease was found.
Both mutations demonstrated compromised calcium binding and
the Asn97Ser mutation elicited a defective interaction with RYR2,
exclusively occurring at a low calcium concentration.
Conclusion:
Missense mutations in calmodulin have been demon-
strated. The molecular mechanism of a defective calmodulin-RYR2
interaction may lead to arrhythmias. Calmodulin mutations can
be tolerated but might cause CPVT-like disease with syncope and
sudden cardiac death.
470: CONTRACTILE PROPERTIES OF HUMAN LYMPHAT-
IC VESSELS
IN VITRO
: A NEW PERSPECTIVE ON
PROTEIN-LOSING ENTEROPATHY FOLLOWING FONTAN
OPERATION
Niklas Telinius
1,2
, Donna Briggs Boedtkjer
1,2
, Marc de Leval
3
, Hans
Pilegaard
1
, Christian Aalkjaer
2
, Vibeke Hjortdal
1
1
Department of Cardiothoracic Surgery, Aarhus University Hospital,
Aarhus, Denmark
2
Department of Biomedicine, Aarhus University, Aarhus, Denmark
3
Harley Street Clinic, London, United Kingdom
Background:
Protein-losing enteropathy (PLE) is a devastating late
complication after the Fontan operation for univentricular hearts.
Although the pathophysiology is not fully understood, high venous
pressure is often present and may impair lymph flow, leading to
intestinal oedema and PLE. Lymphatic vessels are divided into
segments by unidirectional valves and the muscular vessel wall
generates phasic contractions pumping lymph centrally. In our study
we investigated the contractile properties of human lymphatic vessels
to provide insight into the complex pathophysiology of PLE, with a
view to future pharmacological treatment.
Methods:
Thoracic ducts were harvested with informed consent
from 26 patients undergoing oesophageal cancer surgery. Isolated
vessel segments were mounted in a wire myograph for isometric
force measurements. The diameter–tension relationship was estab-
lished and the following pharmacological protocols tested: dose–
response curves for norepinephrine, endothelin-1 and thromboxane
analogue U46619, and phasic contractile activity in the presence of
L-NAME and indomethacin.
Results
The diameter–tension relationship revealed the vessels
generating maximal contractions at a transmural pressure of 21
mmHg. The active curve was flat, indicating the vessels can contract
at a wide range of diameters, with peak pressures of approximately
60 mmHg. Phasic contraction frequency was 1.39
±
0.35min
-1
.
Blocking the NO production with L-NAME, and subsequently
prostaglandins with indomethacin, increased the frequency two- and
five-fold, respectively. Norepinephrine, endothelin-1 and U46619
induced contractions in a dose-dependent manner with maximal
contractions of 40–60 mmHg. High doses of all substances turned
the phasic contractions into small oscillations, almost resembling a
ventricular fibrillation.
Conclusion:
We have shown that the thoracic duct from humans
generates phasic contractions and that this activity can be modu-
lated in several ways. Furthermore, the human thoracic duct has the
capacity to overcome high venous pressures. Based on our results,
we propose a novel approach to treating PLE by pharmacologically
increasing lymphatic pumping.
502: AN
IN VIVO
CARDIAC ASSAY TO DETERMINE THE
FUNCTIONAL CONSEQUENCES OF PUTATIVE LONG QT
SYNDROME MUTATIONS
Chuanchau Jou
1,2,3
, Spencer Barnett
1,2
, Jian-Tao Bian
2
, Cindy Weng
3
,
Xiaoming Sheng
3
, Martin Tristani-Firouzi
1,2,3
1
Division of Paediatric Cardiology, University of Utah, USA
2
Nora Eccles Harrison Cardiovascular Research, University of Utah,
USA
3
Department of Paediatrics, University of Utah, USA
Background
: Genetic testing for long QT syndrome (LQTS) is now
a standard and integral component of clinical cardiology. A major
obstacle to the interpretation of genetic findings is the lack of robust
functional assays to determine the pathogenicity of identified gene
variants in a high-throughput manner. Since zebra fish have cardiac
electrophysiology similar to that of humans, the goal of this study
was to design and test an
in vivo
high-throughput cardiac assay to
distinguish between disease-causing and normal
KCNH2
(
hERG1)
variants using the zebra fish as a model organism.
Methods:
We tested the ability of previously characterised LQTS
hERG1
mutations and polymorphisms to restore normal repolarisa-
tion in the
kcnh2
knockdown embryonic zebra fish. Fertilised zebra
fish eggs were injected with
kcnh2
-morpholino with or without
hERG1
mutant cRNAs. The cardiac phenotypes of embryos (48-hour
post-fertilisation) were visually assessed under light microscopy to
determine the degree of repolarisation. Results of the zebra fish assay
were compared with the current benchmark
in vitro
assay.
Results
: The cardiac assay correctly identified a non-disease-causing
variant in nine of 10 cases (negative predictive value 90%) while
correctly identifying a disease-causing variant in 40/40 cases (posi-
tive predictive value 100%).
Conclusions
: The
in vivo
zebra fish cardiac assay is as precise as the
current benchmark
in vitro
assay for the detection of disease-causing
mutations and far superior in terms of throughput rate. Together with
emerging algorithms for interpreting a positive LQTS genetic test,
the zebra fish cardiac assay provides an additional tool for the final
determination of pathogenicity of gene variants identified in LQTS
genetic screening.
522: HYDROGEN SULPHIDE UPREGULATED HAEME
OXYGENASE 1 EXPRESSION IN RATS WITH VOLUME
OVERLOAD-INDUCED HEART FAILURE
Chaoying Zhang, Xiaohui Li
Children’s Hospital affiliated to Capital Institute of Paediatrics, China
Background:
Chronic heart failure (CHF) is a common complica-
tion of left-to-right shunt congenital heart disease. The mechanism
responsible for CHF is not fully understood. Hydrogen sulphide
(H
2
S), a newly found gasotransmitter, has been reported to play an
important pathophysiological role in the cardiovascular system. The
present study was designed to determine the role of H
2
S in CHF
induced by left-to-right shunt, leading to volume overload.
Methods:
Thirty male Sprague-Dawley rats were randomly divided
into four groups: shunt group (
n
=
8), sham group (
n
=
8), shunt
+
sodium hydrosulphide (NaHS) group (
n
=
8), and sham
+
NaHS
group (
n
=
6). Chronic heart failure was induced in the rats by
abdominal aorta–inferior vena cava puncture. Rats in the shunt
+
NaHS and sham
+
NaHS groups were injected intra-peritoneally
with NaHS (H
2
S donor) at 56
μ
molkg
-1
d
-1
, and at the same time, rats
in the shunt and sham groups were injected with the same volume of
physiological saline. Eight weeks after surgery, left ventricular HO-1
mRNA expression was measured by real-time PCR. Protein expres-
sion of HO-1 was evaluated by Western blots.
Results:
Eight weeks after surgery, protein expression of HO-1 was
significantly decreased in the shunt group compared with that in the
sham group (0.54
±
0.11 vs 1.04
±
0.20,
p
<
0.05). Protein expres-
sion of HO-1 was significantly increased in the shunt
+
NaHS group
compared with that in the shunt group (1.06
±
0.10 vs 0.54
±
0.11,
p
<
0.05). HO-1 mRNA expression was significantly increased in the
shunt
+
NaHS group compared with that in the shunt group (5.86
±
0.61 vs 1.86
±
0.29,
p
<
0.01).
Conclusions:
H
2
S may play a protective role in volume overload-
induced heart failure by up-regulating protein and mRNA expression
of HO-1.
