World Journal of Cardiovascular Surgery, 2011, 1, 24-28
doi:10.4236/wjcs.2011.12005 Published Online December 2011 (http://www.SciRP.org/journal/wjcs)
Antegrade Brain Perfusion for Pulmonary
Thromboendarterectomy
Jean Francois Morin, Andrew Hirsch, Senthuran Tharmalingam
Jewish General Hospital Division of Respiratory Medicine, McGill University, Montreal, C anada
Received September 28, 2011; revised October 30, 2011; accepted Novem b er 11, 2011
Abstract
Objective: The gold standard procedure for pulmonary thromboendarterectomy is median sternotomy, car-
diopulmonary bypass, profound hypothermia (18˚C) and circulatory arrest. We propose a modified technique
to improve the quality of care in this patient population, based on an intervention previously used in aortic
surgery. Method: In our modified technique, we cannulated the right axillary artery to allow antegrade brain
perfusion while on circulatory arrest. In this retrospective study, we have reviewed the data relating to the
first 7 patients on whom we performed the modified technique and have made comparison with a group of 7
case-matched individuals who underwent the standard technique (control group). Results: The modified
technique allowed for use of moderate hypothermia (25˚C - 28˚C). Patients in both groups woke up without
neurologic complications. A trend towards, but non-significant reduction in duration of surgery from 303
(±42) to 279 (±44), duration of postoperative inotropic support from 2.7 ± 3.4 days to 1.7 ± 2.0 days, as well
as postoperative mechanical ventilation time from 4.87 (±3.7) to 2 (±2.7) days were seen in the control and
modified groups respectively. All patients in the modified group woke up on post-operative day 0, whereas
most patients in the control group awoke on postoperative day 1. No significant differences were noted in the
reduction in preoperative to postoperative systolic pulmonary artery pressure, post-operative length of stay in
the intensive care unit and length of stay in the hospital among the two groups. Conclusions: The antegrade
brain perfusion via the right axillary artery allows for good brain protection, while maintaining a bloodless
field in the arterial pulmonary tree. All our patients awoke without any neurologic deficits. In the future, by
using an even milder level of cooling, we may be able to significantly reduce the duration of surgery and im-
prove the recovery of our patients.
Keywords: Cerebral Perfusion, Pulmonary Thromboendarterectomy
1. Introduction
Pulmonary thromboendarterectomy (PTE) offers a sur-
gical cure for pulmonary hypertension due to thrombo-
embolic disease [1]. The standard technique for throm-
boendarterectomy, as developed at the University of San
Diego (UCSD), involves median sternotomy, cardiopul-
monary bypass and intermittent periods of deep hypo-
thermic circulatory arrest (DHCA) to 18˚C [1]. Using
this method, the UCSD group reported 17% operative
mortality in their first 200 cases but have decreased it to
below 5% in the last 500, suggesting a learning curve
associated with the procedure [2]. Another group, Thomson
et al., reported a 15% mortality in their total cohort of
150 patients, but only 4% in the last 25 patients (Thom-
son).
It has also been reported that the use of DHCA is as-
sociated with longer duration of surgery, adverse post-
operative neurologic outcomes due to derangements in
cellular metabolism [3] and coagulation disorders pro-
moting haemorrhage [4]. We also hypothesize that
DHCA is associated with increased postoperative wake
up time, mechanical ventilation time and longer use of
postoperative inotropic support.
To enable an increase in circulatory arrest time and
alleviate the need for deep hypothermia, there have been
attempts by several groups to use antegrade cerebral
brain perfusion to improve operative morbidity in PTE
[2,5,6]. The concept of antegrade cerebral brain perfu-
sion had previously been successfully implemented in

J. F. MORIN ET AL.25
aortic arch surgery [7].
In a retrospective study, we present our results in 7 pa-
tients who underwent selective antegrade brain perfusion
at moderate hypothermia.
2. Patients and Methods
Prior to 2008, all patients at our center underwent the
standard technique. Since 2008, antegrade cerebral per-
fusion has been used in PTE. In this retrospective study,
we have reviewed the data from the first seven patients
who underwent the modified procedure. We then made
comparison with the last seven case-matched patients
who underwent the standard technique, as developed at
the UCSD (control group) [1].
The preoperative characteristics of the patients are de-
scribed in Table 1.
The indication for operation was established after
clinical assessment and hemodynamic parameters (on the
basis of pulmonary function tests, echocardiogram, and
right heart catheterization). An inferior vena cava (IVC)
catheter was placed in all patients preoperatively.
2.1. Surgical Technique
General anaesthesia was induced. Following this, a
transverse incision is made below the right clavicle, until
the right axillary artery is identified. An 8 mm Hema-
shield sidegraft is sewed to the right axillary artery [8].
One end of a cannula is inserted into the sidegraft, while
the other is connected to the cardiopulmonary bypass
machine.
Following this, a median sternotomy is performed and
the pericardium is opened. Systemic heparinization is
administered to achieve an activated clotting time of
greater than 500 s. The innominate artery and left com-
mon carotid arteries are exposed. The superior vena cava
(SVC) and inferior vena cava (IVC) are cannulated for
cardiopulmonary bypass. After the institution of bypass,
the body is cooled to moderate hypothermic temperatures
of 25˚C - 28˚C. Once the heart fibrillates, the aorta is
cross clamped and cardioplegia is delivered through a
cannula inserted into the ascending aorta. The cardio-
pulmonary bypass pump is stopped. The origin of the
innominate artery and left carotid arteries are clamped,
so as to prevent backflow. Then, antegrade perfusion of
the brain via the right axillary artery is begun, maintain-
ing a perfusion pressure of 50 mmHg.
Endarterectomy is begun with a longitudinal incision
of the right pulmonary artery. The endarterectomy plane
is extended distally as far as needed into the affected
segmental or subsegmental vessles. After completion, the
right arteriotomy is then closed, and the innominate and
left carotid arteries are unclamped and the CPB pump is
restarted for 10 - 15 minutes. After which, the pump is
once again stopped, the innominate and left carotid ar-
teries are clamped, antegrade cerebral perfusion is re-
started and endarterectomy of the left side is begun in a
similar fashion.
Following bilateral endarterectomy, the CPB machine
is restarted and the patient is re-warmed to a temperature
of 36.5˚C.
2.2. Statistical Analysis
The software, StatView, was used for statistical analysis.
Continuous data are expressed as mean with standard
deviation or median with range, while categorical data
are expressed as total number of occurrences. Where
applicable, parameters were analyzed using the Student
t-test.
Table 1. Preoperative characteristics.
Preoperative parameters Control Modified p Value
Age (y, mean ± SD) 47 ± 11 56 ± 7 0.09
Female:Male 5:2 4:3
BMI (kg/m^2, mean ± SD) 28 ± 9 28 ± 7 0.97
NYHA class
I
II
III
IV
0
0
7
0
0
1
5
1
Previous DVT or PE 6 7
Mean pre-operative sPAP 89 ± 26 77 ± 8 0.25
Coagulation problem (APA, LPA) 2 0

J. F. MORIN ET AL. 26
3. Results
As expected, all patients, in both groups, showed a sig-
nificant reduction in systolic pulmonary artery pressure
(sPAP). The average difference in preoperative to post-
operative sPAP were 28.6 ± 12.9 to 37 ± 12.2 mmHg in
the modified and control groups, respectively (p = 0.23).
The mean duration of total circulatory arrest times
were 56.1 ± 12.5 vs. 48.6 ± 15.0 minutes in the modified
and control groups, respectively (p = 0.33). The right
sided circulatory arrest times were 32 ± 10.9 vs. 25.6 ±
12.8 minutes in the modified and control groups, respec-
tively (p = 0.33). The left sided circulatory arrest times
were 24.1 ± 3.6 vs. 23 ± 6.4 minutes in the modified and
control groups, respectively (p = 0.69).
The total duration of surgery was 279 ± 44 vs. 303 ±
42 minutes in the modified and control groups, respec-
tively (p = 0.33).
Postoperative 8 h blood loss was measured in all pa-
tients using the mediastinal chest sump tube. The meas-
ured blood loss was 824 ± 698 vs. 576 ± 448 ml in the
modified and control groups, respectively (p = 0.44).
All patients in the modified group awoke postopera-
tively on the day of surgery, however only one patient in
the control group awoke on the day of surgery, while the
others awoke on postoperative day 1. The mean mechani-
cal ventilation time was 2 ± 2.7 vs. 4.9 ± 3.7 days for the
modified and control groups, respectively (p = 0.13). The
modified group required a mean of 1.7 ± 2.0 days of post-
operative inotropic support, as opposed to 2.7 ± 3.4 days
required for the control group (p = 0.50). The median
length of ICU stay was 6 days (range of 2 - 18) for the
modified group and 8 days (range of 2 - 31) for the control
group. The median length of hospital stay was 23 days
(range of 10 - 39) for the modified group as opposed to 16
days (range of 7 - 46) for the control group.
All patients survived the operation. There were no perma-
nent neurologic complications seen in the control nor modi-
fied groups. One patient developed transient postoperative
confusion in the control group. Other postoperative complica-
tions between the two groups are recorded in Table 2.
4. Discussion
Although the series is small, our results confirm that PTE
with moderate hypothermia and antegrade cerebral per-
fusion is a safe alternative to the standard technique. The
use of right axillary perfusion allows for cerebral circula-
tion while performing the endarterectomy. There were no
permanent or transient neurologic deficits reported in our
modified group.
To our knowledge, this is the first report of PTE with
right axillary antegrade cerebral perfusion with moderate
Table 2. Postoperative complications.
Control Modified
Postoperative complications No. % No. %
Death 0 0 0 0
Neurological
Focal deficits
Delirium/Confusion
0
1
0
14
0
0
0
0
Atrial fib 1 14 2 29
Tamponade/re-exploration 0 0 2 29
Reperfusion injury/ARDS 3 43 4 4
Pneumonia 2 29 2 29
Pneumothorax 1 14 0 0
Respiratory failure 0 0 0 0
Pleural effusion 5 71 4 57
Heparin induced thrombocytopenia 1 14 0 0
Hemoptysis 0 0 1 14
Sepsis 0 0 1 14
Pulmonary thrombosis 0 0 0 0
Sternal wound infection 0 0 1 0
hypothermia using the technique of clamping the right
innominate and left common carotid arteries. Three
groups had previously reported using different versions
of antegrade cerebral perfusion for PTE. The Hagl et al.,
group had performed antegrade brain perfusion at mod-
erate hypothermia (28˚C - 32˚C), via an aortic inflow
cannula. Proximally, an aortic clamp was placed below
the inflow cannula and distally they performed balloon
occlusion of the descending aorta, near the origin of the
bronchial artery [5]. The Thomson et al. group used con-
tinuous antegrade cerebral perfusion also via an ascend-
ing aortic cannula at 20˚C, with occasional clamping of
the ascending aorta, proximally, and the region between
the left common carotid and left subclavian artery dis-
tally [2]. Masuda et al., used bilateral perfusion of the
right axillary and left common carotid artery, with
clamping of the ascending aorta, at deep hypothermia
(18˚C) [6]. The first two groups reported having to resort
to DHCA in certain cases to complete the procedure due
to significant bronchial artery backflow [2,5]. The third
group reported having performed suboptimal dissections
in 2 of their 4 cases [6]. We believe that clamping the
origins of the left carotid artery and the right innominate
artery is the best way to minimize retrograde backflow.
Excellent visualization of the endarterectomy plane was
obtained in all our cases to perform the meticulous ex-
traction of thro- mbo-embolic material.

J. F. MORIN ET AL.27
Our study is the first to compare the postoperative
hemodynamic parameters between the standard tech-
nique to that of selective antegrade brain perfusion with
moderate hypothermia. The results obtained suggest that
the modified procedure did not negatively affect the
postoperative hemodynamic parameters. In fact, there
was a significant reduction in postoperative wake up
time, and non-significant reduction in duration of surgery,
postoperative mechanical ventilation time and need for
postoperative inotropic support in the modified group in
comparison with the control group.
With a larger sample size and even milder tempera-
tures, we believe that significant differences in duration
of surgery can be achieved with the modified technique.
Longer duration of surgery implies additional CPB time
to cool and re-warm the patient. The prolongation of
CPB can in turn cause increased micro-emboli produc-
tion and blood component trauma [9].
In our results, we did not find a significant difference,
between groups, in postoperative 8 h blood loss, as col-
lected in the mediastinal sump. Perhaps, a measurement
of difference in preoperative to postoperative serum co-
agulation factors and amount of postoperative blood
transfusion requirements, may be a better reflection of
hypothermia induced coagulopathy. Inclusion of this data
could be relevant for future studies.
A major limitation of our study is the retrospective
nature and the small sample size. There may also be a
procedural learning bias in comparing the control popu-
lation, whose surgeries were all performed prior to that
of the modified population. However, we attempted to
reduce this bias by reporting only the last 7 patients in
whom we performed the standard technique; prior to
2008, a total of 21 PTE surgeries had been performed
using the standard technique.
A second limitation of our study is the assumption that
by performing unilateral perfusion of the right axillary
artery, there should be adequate collateral flow between
the right and left hemispheres through the circle of Willis
(CW). There is sufficient evidence of good cross perfu-
sion of both hemispheres via the CW in the majority of
the population to avoid preoperative CT brain angiogra-
phy. Firstly, in his study of the anatomy of the CW, Al-
pers described a normal configuration of the CW in only
52.3% of brain speciemens. However, it was noted that a
truly incomplete CW, occurred in only 0.005% of cases
[10]. The major anomaly seen was hypoplasia of one or
more arteries. Although these hypoplastic vessels may
offer increased resistance to collateral flow, histologic
studies show that even in their most anomalous form,
collateral flow is adequate for nutritional requirement
[11]. Secondly, it has been found that anatomic incom-
pleteness of the CW as determined by CT angiography
does not correlate with actual functional cerebral cross-
perfusion [12].
5. Conclusions
Our results demonstrate that PTE via right axillary ante-
grade cerebral perfusion at moderate hypothermic tem-
peratures is safe and technically feasible. The technique
allows for a bloodless operative field. No permanent or
transient neurological complications were seen in the
modified group. With a larger population size and even
milder cooling, more benefits maybe seen with the modi-
fied technique.
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