aortic clamping (SAC) technique is the preferred practiced method for many
cardiac surgeons due to the assumption that minimal aortic manipulation is
secured by this method; however, superiority in the clinical prevention of
stroke using this technique has not been widely demonstrated (4). Several
studies have reported conflicting conclusions about the rates of post-operative
stroke in both the SAC and multiple aortic clamping (MAC) techniques. In a
previous meta-analysis published in 2008 by Raja and colleagues, it was clear
that either method of aortic clamping is comparable in terms of stroke outcome
(5). However, in 2014, Moss and colleagues demonstrated a clear beneficial
reduction in the rates of postoperative stroke with fewer aortic manipulations
regardless of the severity of ascending aortic disease (2).
retrospective study, we hypothesised that aortic manipulation during CABG would
adversely affect patients due to the presence of aortic arteriosclerosis.
Therefore, our aim is to investigate the potential effect of aortic clamping
techniques on the development of stroke in patients undergoing isolated CABG.
We conducted this retrospective study to include relatively large cohorts of
patients, comparing early adverse clinical events in patients undergoing
isolated CABG utilising either SAC or MAC techniques and to determine whether
SAC has beneficial effects in preventing the risk of early stroke in clinical
Patients and Methods
We reviewed the electronic medical
records of 219 patients who underwent CABG surgery with two equivalent surgeons
in terms of expertise and number of patients, during the period from January
2020 to December 2020 at Queen Alia Heart Institute (QAHI). In total, 110 (50%)
patients were operated on utilising the SAC technique, while 109(50%) underwent
the MAC technique. As a practice protocol in our centre, carotid Doppler
ultrasound screening assessment used for elderly age patients, prior stroke or
transient ischemic attack and peripheral artery disease. Patients who had
significant carotid stenosis are offered carotid intervention in addition to
coronary bypass surgery. We outlined several factors (Table I) relevant
to the included patients which we think may be factors in determining outcomes
after CABG. Factors included age, sex, diabetes mellitus (DM), hypertension,
New York Heart Association (NYHA) classification of functional limitation
related to heart disease, number of coronary arteries involved and left
outcome: Early stroke that occurred early in the postoperative period or
during the same admission period.
outcomes: 1.Early mortality, which is
any death that occurred early in the postoperative period or
during the same admission period
2. Occurrence of
postoperative atrial fibrillation (AF)
bleeding necessitates surgical intervention
4. Length of hospital
Table I: Relevant
demographics and risk factors for the patients included in the study
Male Sex (%)
Abbreviations: MAC: Multiple
Aortic Clamping, SAC: Single Aortic Clamping
All of the included patients were operated
upon through a standard median sternotomy incision. Conduits that were utilised
are: the left internal mammary artery (LIMA) and the great saphenous vein. The
LIMA harvest was performed in the classical fashion while the saphenous vein
harvest was performed using the open technique.
bypass in all patients was established by standard ascending aortic cannulation
and double stage venous cannulation of the right atrial appendage. Heparin for
anticoagulation was given to achieve a therapeutic activated clotting time
(ACT). Normothermic perfusion with antegrade intermittent cold crystalloid
cardioplegia and retrograde blood cardioplegia was used according to the
SAC Technique: After completion of the distal anastomosis at the coronary
targets, the proximal anastomosis on the ascending aorta was completed without
manipulation of the aortic clamp.
MAC Technique: Once the distal anastomosis at the coronary targets is completed,
the aortic clamp is released and then a side biting clamp is applied to allow
for proximal anastomosis on the ascending aorta while the heart is beating.
surgical conduct is carried in a similar fashion between the two surgical
The categorical data are expressed as
the frequency and percentage. The scale data are expressed as the mean and
standard deviation. Chi square of independence was used to determine
associations between categorical data, while the independent T-test was used to
test mean differences between categorical independent variables. The alpha
level, set at ≤0.05, indicated statistically
significance and SPSS software version 28 was used to analyse data.
Over a one-year period, 219 patients underwent
coronary artery bypass grafting by two equivalent surgeons. Two techniques were
used: CABG with the SAC method (110 patients), and CABG with the MAC method
(109 patients). Demographics and risk factors of the patients included are
summarised in Table I. The two patient populations, SAC and MAC, were
comparable with regard to mean age, sex, DM, smoking history, hypertension and
previous history of stroke.
The number of
grafts performed was comparable between the 2 cohorts (2.38±0.72 vs 2.41±0.64
for SAC vs MAC, respectively; p=0.736).Cardiopulmonary bypass duration was
longer in the MAC compared to the SAC technique (69.93±13.08 min vs
104.95±15.92 min p<0.001, respectively). Surprisingly, the ischemia time was
even longer in the MAC compared to the SAC (54.03±8.11 min vs 51.31±11.1 min,
p=0.041) (Table II).
Table II: Intraoperative
Cardiopulmonary Bypass Time (minutes)*
Cross Clamp Time (Minutes)
Number of Proximal Grafts (mean)
Abbreviations: MAC: Multiple
Aortic Clamping, SAC: Single Aortic Clamping
* Note: It was surprising to us to find that the
duration of aortic cross clamp was shorter in the single clamp cohort, but we
shall admit that the technique of anastomosis entails some factors that are
dependent on the quality of the target vessels and the surgical skills
Table III summarises the early outcomes of all patients.
Postoperative stroke was substantially higher in the MAC cohort compared to the
SAC cohort (3/110 (2.7%) vs 12/109 (11%), p=0.015,OR=4.41). The outcome with
the highest incidence rate was AF but was not statistically significantly
different between the two cohorts (5.5% vs. 10.1%; p=0.200). Reopening for
bleeding, was equivalent in both cohorts (3.6% vs 3.7% for SAC vs MAC,
In-hospital mortality was more frequent in
MAC-CABG compared to SAC-CABG although not significantly (0.9% SAC-CABG vs.
5.5% MAC-CABG; p=0.065).
The mean hospital stay period was higher in
MAC-CABG than in SAC-CABG patients (9.055 vs. 7.109 days, respectively;
p<0.001), and the explanation of long hospitality in both groups is due to
our policy in our centre is to keep patients pot-operatively as long as
possible due to social reasons especially in the time of COVID pandemic in most
of the cases.
Table III: Early outcomes
obtained from our study results
Abbreviations: MAC: Multiple
Aortic Clamping, SAC: Single Aortic Clamping, OR odds ratio
**Note: we agree that the rate of stroke was
higher than reported, but the cohort of patients that were operated upon were
little bit sick and had multiple comorbidities
Our retrospective study included 219
studies and demonstrated that there is an obvious and significant reduction in
the incidence of stroke when the single clamp technique is utilised during
isolated coronary artery bypass grafting. However, the single aortic clamping
strategy did not demonstrate a significant advantage in improving survival or
decreasing the incidence of atrial fibrillation or postoperative bleeding
Achilles heel of cardiac surgery, is known to be one of the most devastating
complications after coronary artery bypass surgery, with an approximate
incidence of 2% (reaching 9% in octogenarians); once this happens, it indicates
a very poor prognosis (6).There have been multiple aetiologies which are
implicated to increase the risk of stroke in cardiac surgery such as:
manipulations of the ascending aorta, adoption of an on-pump coronary artery
bypass method, history of previous stroke, carotid artery stenosis and
peri-operative rhythm disturbances(7, 8). Different strategies have been
adopted by cardiac surgeons to minimise the impact of aortic clamping and
aortic manipulations. Hammon and colleagues (9) demonstrated that even on-pump
coronary artery bypass surgery using single clamp technique with less
manipulations of the ascending aorta may be more protective against the
development of postoperative stroke compared to off-pump surgery with side
clamp application. Data using transcranial Doppler signals during coronary
artery bypass surgery demonstrated that significant cerebral embolic burden
occurs both during on-pump coronary artery bypass as well as after the removal
of the side clamp in off-pump surgery (2). Raja and colleagues (5) demonstrated
in their meta-analysis that there is no superiority of single clamp in terms of
stroke incidence when compared to the multiple clamp technique. It must be kept
in mind that the majority of published studies investigating the correlation
between the aortic clamping technique and postoperative stroke may be
underpowered for major clinical events.
demonstrates the clear benefits of SAC compared to MAC in decreasing the risk
of stroke after CABG surgery. Previous studies(9-12) did not demonstrate any
stroke amelioration benefit for SAC compared to MAC techniques; however,
concerns about the patient cohorts included may be a potential factor for this
conclusion, since we believe that patients who are at a higher risk of
developing stroke are thosewho will benefit the most from less manipulation of
the aorta during CABG. Hammon et al.(9) excluded patients from their cohorts
who had high grade atheromatous aorta, renal dysfunction and major
neurodegenerative disease. Dar and Musumeci(10, 11) excluded patients who are
older than 75 years of age, and those with carotid bruits, aortic
calcifications and a history of previous cerebrovascular accident and atrial
fibrillation. Uyar et al.(12)excluded patients who had aortic plaques. Other
published reports are in accordance with our study and demonstrated the
superiority of SAC over MAC in ameliorating the risk of stroke after CABG
surgery (13-15). In clinical practice, cardiac surgeons are always trying to
avoid manipulations of the hostile aorta and often perform SAC or operate on a
beating heart instead. The variability in postoperative stroke incidence among
the published studies could be due to other factors that play a role in the
aetiology of stroke other than just the application or removal of aortic
clamps, such as: cannulation and decannulation, the adequacy of de-airing,
hypoperfusion, induced inflammatory cascades and punching of the proximal aorta
demonstrated that short-term survival was not significantly different in the
two cohorts; however,it is well known that survival after surgical
revascularisation is primarily dependent on the patency of grafts and other
comorbid conditions in patients. We think that this outcome did not differ
between the two cohorts because the mortality is determined by many variables and
not only stroke.
the MAC technique is a concern amongst cardiac surgeons performing CABG
utilising SAC because of the inherently prolonged ischemia time in the SAC
technique; however, no evidence is found to suggest an increased cardiac morbidity
when utilising the SAC technique, especially when proper myocardial
preservation strategies are used. CABG is also a demanding surgical procedure
which requires meticulous steps to be accomplished within the shortest period
of ischemia time to avoid the risk of myocardial injury; in addition, surgeons
have adopted different methods for myocardial preservation to accomplish
myocardial protection.Surprisingly, our data indicate that improved skills when
performing CABG using the SAC method enabled our surgeons to accomplish
surgical anastomosis even with a shorter ischemia time.
fibrillation after CABG is a common arrhythmia which is reported to occur in
10–50%of patients (17).The mechanism of postoperative AF is multifactorial and
we did not find an actual relationship between the duration of cardiopulmonary
bypass and the incidence of AF, which was consistent with previous reports
(18). The in-hospital stay period was longer in the MAC cohort, which can be
explained by the prolonged period of stay for patients who suffered from
Strengths and Limitations
We would like to acknowledge some
limitations related to our study. Firstly, this was a retrospective designed
study, second, we could not identify the exact aetiology of stroke and whether
this was due to embolism, hypoperfusion or thrombosis in each patient, third,
patients at the highest risk of developing stroke were excluded from our study,
and fourth, aortic Ultrasound and pre-operative CT scan for the assessment of
aortic calcifications were not performed.
would like to point out that our study had substantial advantages. Our included
cohorts are the largest to date from our centre that could be achieved; with
this robust number of patients, we believe that we were able to detect
differences in the outcomes between the two cohorts included.
The single aortic clamp technique has been
proven to be an effective strategy with which to protect against the occurrence
of stroke after coronary artery bypass grafting surgery. Meticulous steps could
help with performing this technique using comparable time durations. Aortic
manipulations did not result in an added risk of early mortality, postoperative
atrial fibrillation and the incidence of major bleeding episodes.
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