Chua, Tuan Peng

Coats, Andrew J.

Iserin, Laurence

Somerville, Jane

Elsevier - Publisher Connector 

JACC February 1996 ABSTRACTS- Poster 37 i A 
• Thmmboembolism In High Risk Patients 
Undergoing Bidirectional Cavopulmonary 
Anntomos ls  
Thomas Forbes, Geoffrey Rosenthal, George Reut, David Oft, 
Timothy Feltes. Texas Childrens' Hospital, Houston, TX 
We have nbserved perioperative pulmonary thrombotic events (PTE) in pts 
~o==owtng ~;'dtrectional cavopulmenery anastomosis (BCA). The risk factors 
for devo'.opment of PTE in this group are unknown. The purpose of this 
study ~ ~ ) Identify possible preoperative and immediatiate postoperative 
risk fastors for development of PTE in pts undergoing BOA. Methods: We 
compared 4 pt~ (mean age 4.2 ± 5.2 yrs) with PTE following BOA to 20 BCA 
pts (mean age 5 :E 5.3 yre) who did not develop orioporative PTE. Of the 4 pts 
who had a PTE, 3 expired within 12 days of their surgery and the 4th required 
emergent stenting of the thrercbus on postoperative day 5. The preoperative 
risk factors evaluated were: age at surgery, f, lakata and McGoon indices, 
pulmonary arterial reslstence, systemic and rclxed venous saturations, and 
the presence of bilateral SVCs. Tha postoporatJve risk factors evaluated 
were: CVP (rcrcHo), 02 saturations, pAO2, and pH (all at 0.12, 24, 36, and 48 
hours post-up). Contingency tables and multiple logistic regression analyses 
were preformed. Results: Relative to a McGoon ratio 2.0, as our patient's 
indices decreased by 0.5, the odds of PTE increased 14 fold (p = 0.08). The 
odds of PTE among those with bilateral SVCs was 17 times greater than the 
odds of PTE among those with a single SVC (p < 0.05). Relative to a CVP 
of 10 at 12 hours post-op (CVP12), as our patient's CVP increased above 
20 rcrcHg, the odds of PTE increased 10 fold (p < 0.05). The associations 
between PTE and the predictors CVP12 and bilateral SVCs were not effected 
by adjustment for other vadablas. Conclusion: We consider pts undergoing 
BCA who have bilateral SVCs, low McGoon indices, and increased CVPs at 
12 hours post-up, at greatly increased risk for pefioporative PTE. We have 
adopted a strategy for early anticoaguiation and early removal of superior 
vena caval lines in these lots. 
~ Chemoreflex and Exercise Ventlbtion in 
Univentricular Patients 
Tuan Peng Chua, Laurence Iserin, Jane Somerville, Andraw J. Coats. Royal 
Brompton National Heart & Lung Institute, London, UK 
Patients with univentricular hearts have excessive exemise ventilation. We 
examined the chemoreflex in relation to cardiopulmonary exercise testing in 
two groups of univentricular patients, 10 cyanotic patients (Group A; age 30.5 
:1:2.3 (SEM) years; 5 men) with palliative surgery only and 7 patients (Group 
B; age 29.6:1: 1.8; 3 men) with Fontanotype circulation wltcse hypoxemia is
relieved, Ten healthy controls ware also studied (Group C; age 34.7 4- 1.9; 
5 men). Hypoxio and hypercapnic hercosensitivity were assessed using 
transient inhalations of pure N2 and the rebreathing of 7% CO2 in 93% 02 
respectively. Peak 02 consumption was comparable in group A and B (21.7 
2.5 v 21.3.4* 2.2 mlJkg/min) but higher in C (34.7 :l: 1.9, P < 0.001). The 
ventilafoty response to exercise, characterized by the VE-VCO2 slope, was 
more in group A than B (43.4 v 32.1, P = 0.04), or C (23.4, P < 0,001). 
Resting artedal 02 saturation was 90.6%, 95.0% (P = 0,06) and 99.9% (P 
< 0,001) respectively whilst that at peak exercise was 63.2%, 90.1% (P < 
0.001) and 99.6% (P < 0.001). Hypoxlo chemoreflex was blunted in group A 
corcpared with B (0,148 v 0,482 L/min/%Sa02, P = 0.04) and C (0,311, P < 
0.01) and correlated with the drop in 02 saturation with exercise (r= -0.63, 
P = 0.05). It also correlated with the Ve-VC02 slope in 0mup B (r= 0.95, P 
< 0.01) but not in A, Hypercapnic hemosensitivityo as judged by the slope 
of the ventilatoty response curve to hypercapnia, was similar in all groups 
(1.71 v 1.85 v 1.42 L/min/mmHg CO2, P = 0.4) but the X-intercept of the 
curve was shifted to the left in A (3t.9 v 40.7 v 42.9 rcrcHg COe, P < 0.0t ), 
suggesting that they ventilate more for a given level of CO2 and may explain 
the increased exercise ventilation. Hypercapnic hemosensitivity correlated 
with Ve-VCO2 slope in group A (r= 0,82, P= 0.003) but not in B. 
In conclusion, CO2 elimination ismore ircportant in the control of ventilation 
in cyanotic univentricular patients whilst hypoxic chemoreflex is mare so in 
univentricular Fontan patients. 
~ Abnormal Recovery From Brief Exercise in 
Pediatric Fontan Patients 
W. Brad Troutman, Thomas J. Barstow, Dan. M. Cooper. University of 
California and Harbor-UCLA Medical Center, Los Angeles, CA 
The maximal oxygen uptake (V02 max) test, traditionally used to test exercise 
capability in children with congenital heart defects, requires prolonged work 
at high intensity. Short bursts of exercise better reflect he patterns of normal 
activity found in children. We hypothesized that less strenuous tests would 
detect important abnormalities in the response to exercise in children. To 
examine this, 9 children (mean 12 y. o,, range 8-17 y.o., 4 females) who had 
undergone Fontan procedures performed a voluntary maximal progressive 
cycle ergometar test. The patients then returned for a constant work rate 
test consisting of one minute of high-intensity exercise. Gas exchange was 
measured breath by breath. Iterative co~e-fdting techniques (assuming a 
single exponential) were used to determine the recovery time constant (3) 
for HR and VO2 following the one minute test. The time constant represents 
the time required to retum to 63% of pre-exercise values. Consistent with 
previous observations, VO2 max was reduced (24 ± 6 ml/kg, 57% predicted). 
Recovery times for both HR (r, 96:1:26 sec) and VO2 (r, 53 4- 13 sec) were 
significantly prolonged by 355% and 151%, respectively (p < 05), compared 
with published values for normal children. The prolonged recovery times 
suggest substantial abnorc'~lities of oxygen banspoff~ and may alter the 
pattern of exercise in the daily lives of these children. 
_Architecture of the Myocardlem in Hearts With 
Tricuspid Atresle 
Slaw Yen Ho. Mark Jackson, Damian Sanchez-Qiuntana, 
Lucienne Kitpathck, Audrey Smith. National Heart & Lung Institute, London; 
Institute Of Child Health, I~1 ,  UK 
The fibrous tissue and myocardial fibres of the ventricles in hearts with tri- 
cuspid atmsia weie compared with normals. Interstitial fibrous tissue in four 
ventdcular sites from each of 53 malformed hearts was quantitated using 
an image analysor. Comparing with a normal series of similar age range 
(neonate to 17 years), there was consistently morn fibrous tissue in the 
malformed heart across the age range, even in the youngest hearts. The 
arrangement of the fibrous weave was examined by scanning electron mi- 
croscopy in 10 hearts. It was more dense and sheath-like in the abnormal 
hearts compared to the filigreed appearance in normal hearts. The arrange- 
ment of the myocardial fibres was studied by gross dissection in three hearts 
with tricuspid alresia. The superficial layer of the left ventricle was more lon- 
gitudinally arranged than normal. The quantity and quality of the intersti~:al 
fibrous tissue in the abnormal hearts am probably inherent in the malforma- 
tion and could contribute to myocardial s~neas. Together with the abnormal 
arrangement of the myocardial fibres, the alterations in architecture of the 
myocardiurc ould account for the impairment of left ventricular function 
which is obsen~ed from an eady age in some patients with tricuspid atrasla. 
~ A  Rationale for Rapid Staging of Patlenta With 
Aortapulmonary Shunts: increased Oscillatory 
Work 
Theresa A. Tacy, Kevin K. Whitehead, Eric 1". Lee, Edward G. Cape. 
Cardiac Dynamics Laboratory. Children's Hospital Of Pittsburgh, PA 
When patients with a single ventricle and an aortopulmenary shunt develop 
a dilated and dysfunctional ventricle, it is widely assumed that this is due to 
the volume load imposed upon the venfficle. However, the work imposed by 
an increased volume load is only a portion of the total work of the ventricle. 
The total work of the ventricle is comprised of both static work (energy 
utilized to maintain volume flow) and oscillatory work (energy lost due to 
pulsations). We hypothesize that oscillatory work contributes ignificantly to 
total work, and is independent of volume loading. Methods: Both the static and 
oscillatory components of the vascular workload were measured in an in vitro 
pulsatile flow model using blood analog fluid. Compansons of models with and 
without an aortopulmenary shunt wore performed for cardiac outputs of 2-4 
Vmin. The cardiac output and the peripheral resistance were held constant 
for each comparison. Simultaneous pressure (P) and flow (Q) waveforms 
from the ascending aorta of the model were recorded and resolved into 
ten harmonics using Fouder sades analysis. Static work was calculated as 
Pme~'Qmean- Pulsatile work was calculated as ~ S PIQI cos~, where Pt and 
(~ are the magnitudes of the P pressure and flow harmonics, respectively. 
E) represents the phase between P and Q. Results: For the aortoputmeeary 
shunt models, the pulsatile losses wore significantly higher than the models 
without shunts for the same flow conditions (mean difference 12 4- 6.2%, 
p = 0.03). Furthen'nere, the putsatile losses in this stud), did not correlate 
with the flow rate (r = 0.37). Conc/us/oos: This study suggests that putsatile 
energy losses am important in patients with eortopulmermry shunts and am 
independent of volume load. The single ventricle xpedenoes increased work 
demands from both volume loading and increased oscillatory losses, and 
this burden may contribute to the development of a dysfunctional ventflcle in 
these patients. These findings provide a mtioeale for rapid surgical staging 
of these patients to their next surgical procedure. 
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Chemoreflex and exercise ventilation in univentricular patients 

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Chemoreflex and exercise ventilation in univentricular patients

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