3-D multidetector computed tomography in reoperative cardiac surgery

doi:10.4236/wjcd.2013.35060

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World Journal of Cardiovascular Diseases, 2013, 3, 389-393 WJCD

http://dx.doi.org/10.4236/wjcd.2013.35060 Published Online August 2013 (http://www.scirp.org/journal/wjcd/)

3-D multidetector computed tomography in

reoperative cardiac surgery

Tsuyoshi Kaneko1, Micheal L. Steigner2, Igor Gosev1, Sary F. Aranki1*

1Department of Cardiac Surgery, Brigham and Women’s Hospital, Boston, USA

2Department of Radiology, Brigham and Women’s Hospital, Boston, USA

Email: *[email protected]

Received 19 May 2013; revised 27 June 2013; accepted 14 July 2013

which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

ABSTRACT

Reoperative cardiac surgery is becoming more com-

mon surgery although it carries significant risk due to

possible injury to vital structures under the sternum.

Three-dimensional multidetector computed tomogra-

phic angiography (3-D MDCTA) allows identifying

the relationship between the sternum and the medias-

tinal structures. Evidence shows that 3-D MDCTA

guides surgical strategy and enables to perform this

challenging surgery safely.

Keywords: 3-D MDCTA; Reoperative Cardiac Surgery

1. INTRODUCTION

Reoperative cardiac surgery carries a significantly higher

risk compared to first time surgery. Several reasons exist;

technical difficulties include reoperative sternotomy, me-

diastinal dissection and higher risk in the reoperative

population. However, the cardiac surgeons are facing

more and more reoperations, given the longer expectancy

in the modern era. The recently published mortality rate

for reoperative cardiac surgery in previous coronary ar-

tery bypass graft surgery (CABG) has ranged from 2.5%

to 8.3% [1-7]. The major concern during sternal reentry

in these patients is the potential injury to the cardiac

structures (right ventricle), previous grafts, innominate

vein and Aorta. Surgical strategies, such as interposition

of the lungs in the left internal mammary artery (LIMA)

[8] or no dissection technique [9] have been described in

the literature, but do not eliminate the chances of injury

to these structures.

Contrast-enhanced multidetector computed tomographic

angiography (MDCTA) has emerged as a useful method

to evaluate heart and mediatinal structures [10-11]. In

addition, three-dimensional (3-D) volume rendering al-

lows detailed identification of the previous grafts as well

as the right ventricle and Aorta.

The aim of this paper is to support the usage of 3-D

MDCTA for preoperative evaluation for reoperative car-

diac surgery.

2. METHODS

2.1. 3-D MDCTA

State-of-the-art MDCTA for redo sternotomy typically is

performed with 64 - 320 detector row CT scanners.

Helical acquisitions are performed from above the clavi-

cular heads to the base of the heart with thin slice colli-

mation (0.5 - 1.0 mm) at either 100 - 120 kV and at least

350 mA. Current scanners employ z-axis tube current

modulation as an option for the mA adjustment. Since

small vessel CT angiography requires high contrast to

noise ratios, the highest available concentration of con-

trast (370 mg/dL) is injected at high flow rates (4.5 - 6

ml/sec). Volume of contrast is determined by the scan

time varying from 80 - 100 ml. B-blockade for heart rate

control and nitroglycerine for vasodilation are typically

not required for the assessment of vessel patency and

course; however, these techniques are favored if stenosis

evaluation of the prior bypass grafts is paramount. Since

bypass grafts don’t move with the same velocity as na-

tive coronary arteries, acquisitions can typically be per-

formed with prospective gating with a single phase of the

cardiac cycle. Dynamic assessment of retrosternal struc-

tures has recently been described as an adjunct to the

proximity assessment <ref Malguria, et al. “Static and

Cine CT Imaging to Identify and Characterize Mediasti-

nal Adhesions as a Potential Complication Undergoing

Redo Sternotomy”. AJR ACCEPTED FOR PUBLICA-

TION NOT YET IN PRESS. This technique requires

retrospective gating at the expense of a higher radiation

exposure; however, additional studies are required to

determine its value.

*Corresponding author.

OPEN ACCESS

T. Kaneko et al. / World Journal of Cardiovascular Diseases 3 (2013) 389-393

390

2.2. Interpretation of the 3-D MDCTA

Preoperative evaluation of 3-D MDCTA allows the fol-

lowing assessment.

1) Proximity of LIMA and Other Grafts in Relation to

the Sternum.

2) Adhesion of the Right Ventricle (RV) to the Sternal

Bed (Especially in Light of Pulmonary Hyper Tension).

3) Location of the Innominate Vein and Aorta.

Distance of <1 cm from the sternum to the Aorta, RV

and CABG graft crossing the midline within 1 cm of

posterior to the sternumwere typically used for high risk

upon sternal reentry [12-14].

A survey of 2046 significant bleeding during sternal

entry showed that the most commonly injured structures

were RV (39%), Saphenous vein graft (SVG: 20%),

Aorta (15%), IMA (12%) and innominate vein (6%) [15].

Radiologist and Surgeon must keep this in mind to find

the relationship between the sternum and these structures

when 3-D MDCTA is assessed preoperatively.

2.3. Operative Strategy Based on 3-D MDCTA

After assessing these structures, surgeons will consider

the following for operative planning.

2.3.1. Cannul ation Str ategy

1) Direct central cannulation.

2) Guidewire placement for emergency.

3) Peripheral cannulation.

a) Femoral artery cannulation.

b) Axillary cannulation.

First step of operative decision making is cannulation

strategy. Cannulation strategy must be decided prior to

incision with a backup plan. If there is good distance

from the sternum, sternotomy can be performed and di-

rect central cannulation can be performed following me-

diastinal dissection. Mediastinal dissection should be

performed around the Aorta and right atrium first so that

cardiopulmonary bypass (CPB) can be established in

case of emergency.

It is our common practice to place guidewire in femo-

ral artery and femoral vein to prepare for emergency.

Guidewire is inserted under transesophageal echocardio-

gram (TEE) guidance. If any structure is injured during

sternal reentry, sternum is approximated and CPB is es-

tablished following Seldinger technique placement of

arterial and venous cannula.

If adhesions present, peripheral cannulation should be

considered. Femoral artery/vein can be used. Axillary

artery can be used when femoral artery use is concern

(peripheral vascular disease, obesity etc). Our practice is

to place 8 - 10 mm dacron graft to preserve distal flow.

2.3.2. Cardio pulmonary By p ass

1) Go on cardiopulmonary bypass prior to sternotomy.

2) Deep Hypothermic circulatory arrest.

3) No cardiopulmonary bypass.

In severe adhesions, consideration of establishing CPB

prior to sternotomy should be made. This will allow de-

compression of RV and decreases the chances of injury

during sternal reentry. Luciani, et al. reported their ex-

perience with 158 patients who underwent cardiopul-

monary bypass prior to creating sternotomy [16]. This

decision was made on the CT evidence of dense retros-

ternal adhesions, depressed ejection fraction or previous

mediastinitis. Use of CPB prior to sternotomy was asso-

ciated with less re-entry injuries, reduced operative time,

less postoperative bleeding and shorter ICU stay.

Deep hypothermic circulatory arrest can be used for

extreme cases with severe adhesion or injury to the aorta

occurred. For low risk cases, no CPB will allow blood

less dissection since no heparin is used prior to dissec-

tion.

2.3.3. Sternotomy vs Non-Sternotomy

1) Reoperative sternotomy-grafts in relation to the sternal

wires.

2) Anterior thoracotomy.

3) Transcatheter treatment.

Access strategy can be altered depending on the op-

eration being performed. If prior CABG patient with

significant graft adhesion is undergoing mitral valve sur-

gery, literature supports use of right thoracotomy for ac-

cess [17]. Left thoracotomy can be used for reoperative

CABG to circumflex artery and avoiding sternal entry

[18].

If the patient has high risk comorbidity and high risk

findings on 3-D MDCTA, consideration of transcatheter

treatment (percutaneous coronary intervention for coro-

nary disease, transcatheter valve replacements for valve

disease) if indicated.

2.3.4. C anc ellation

When the findings show extremely high risk, surgeon

can decide to cancel the case. 3-D-CTMDA will aid this

decision making. Report from Cleveland Clinic de-

scribed 4% cancellation in their 167 adult reoperative

cardiac surgery series [14]. Patent RIMA with additional

jump graft supplying a left dominant system crossing the

sternal midline at an unsafe distance in a severe valvular

disease patient was one of the examples used in this se-

ries. Other series report 6% - 12% cancellation rate in

their series [13,19].

2.4. Patient Images

Figures 1(a) and (b) show the 3-D MDCTA on 65 years

old male who underwent CABG (SVG to posterior de-

scending artery) and came back for aortic valve replace-

ment (AVR). Preoperative MDCTA showed SVG graft

T. Kaneko et al. / World Journal of Cardiovascular Diseases 3 (2013) 389-393 391

(a)

(b)

Figure 1. 65 years old male after CABG. Previous graft is seen

below the sternum. Proximity of the graft and sternum was

considered high risk. This patient underwent femoral artery

cannulation prior to sternotomy. (Arrow shows the location of

the SVG).

lying behind the sternum <1 cm and was crossing mid-

line. This was considered high risk and operative strategy

was discussed preoperatively. Femoral artery cannulation

was performed prior to sternal reentry. Careful dissection

with anticipation of SVG behind the sternum allowed

safe dissection of the SVG. No injury was encountered

and AVR was performed successfully.

Figure 2 shows the 3-D MDCTA on 70-year-old male

who presented for Aortic stenosis and underwent CABG

(SVG to right coronary artery). He was scheduled for

AVR and preoperative 3-D MDCTA was performed to

assess the mediastinum. MDCTA showed previous SVG

traversing the midline and was densely attached to the

sternum. Preoperative strategy was changed to axillary

artery cannulation and femoral vein cannulation. We had

prepared to go on CPB prior to sternal reentry. During

sternal reentry, SVG injury was encountered and CPB

was established immediately. There were no hemody-

namic instability or ST changes. Mediastinal dissection

Figure 2. 70 years old, M status post CABG with prior SVG

graft to RCA. Graft was traversing the midline and was at-

tached to the sternum (white arrow). Knowing this, we per-

formed axillary artery cannulation and femoral vein cannula-

tion. There was a SVG graft injury during entry and cardio-

pulmonary bypass was established immediately. Mediastinal

dissection followed by SVG graft repair was performed primar-

ily. No hemodynamic instability was encountered as well as ST

changes.

was performed and SVG injury was repaired primarily.

Rest of the procedure was conducted without any prob-

lem.

3. DISCUSSION

3.1. Comparison to Chest X-Ray (CXR)

and Angiography

Gasparovic, et al. compared 3-D MDCTA and CXR/ co-

ronary angiography in their series of 33 patients who

underwent reoperative cardiac surgery after previous

CABG [13]. The correlation for distance of the LIMA

graft from midline and posterior sternum obtained by

CTA and CXR was poor (correlation coefficient: R =

0.56 and 0.49. The R for CTA and angiography was 0.54

for LIMA graft. One third of the CXR could not identify

LIMA graft (from the clips) and 85% of patients could

not obtain pertinent CTA finding from standard CXR and

Angiography.

No injury to the LIMA was reported in this case series.

This is significant improvement from 5.3% injury rate

from Cleveland clinic with perioperative infarction rate

of 50% which CXR and angiography was used for pre-

operative imaging [20].

3.2. Outcomes Using 3-D MDCTA

Early report from Cremer, et al. assessed their 99 adult

patient experiences that had reoperative coronary artery

T. Kaneko et al. / World Journal of Cardiovascular Diseases 3 (2013) 389-393

392

surgery with preoperative spiral CT without contrast an-

giography [21]. No MDCTA was used as well as 3-D

reconstructions, but safe sternal reentry was obtained in

98% and only 2% had injury to vital structures. This

opened the door for preoperative assessment using CT.

In their 33 patient series, Gasparovic, et al. reported

21% alteration in surgical strategy [13]. Two injuries to

vital structures were encountered, right ventricle in 1

case, vein graft in 1 case, but no IMA and aortic injury.

Operative mortality was 17%.

Kamder, et al. reported the largest series to date in

their 167 adult patients with reoperative cardiac surgery

who had prior CABG [14]. They used contrast enhanced

MDCTA for preoperative evaluation. The high risk find-

ings were <1 cm distance between chest wall and right

ventricle or aorta (24%) and graft crossing midline <1

cm anteroposteriorly (38%). 49% had 1 or more high risk

findings. 86% had alteration in surgical strategy: 8%

nonmidline incision, 5% deep circulatory hypothermic

arrest, 11% initiation of peripheral CPB, 53% extratho-

racic vascular exposure before incision and 4% cancella-

tion. Frequency of severe bleeding, injury to vital struc-

tures and 1-month mortality were 4.4%, 5% and 2.5%.

There was no difference in frequency of vital structure

injury and severe bleeding between high-risk and low-

risk MDCTA groups, likely from adoption of preventive

surgical strategies.

Maluenda, et al. reported 137 patients who underwent

MDCTA prior to reoperative cardiac surgery and was

compared to 227 patients who did not have MDCTA

prior to reoperative cardiac surgery [12]. MDCTA group

had lower incidence of perioperative myocardial infarc-

tion, shorter perfusion time and cross clamp time, total

time in intensive care unit and lower volume of postop-

erative transfusion.

3.3. Additional Information

Additional information can be found during CTA as-

sessment. In Gasparovic’s report, 42% had atheroscle-

rotic ascending aortic and aortic arch disease and 3% had

ascending aortic aneurysm. Persistent left superior vena

cava, innominate and superior vena cava stenosis was

found in 9.1%. Of these findings, atherosclerosis of the

aorta carries significance. In case of unclampable aorta,

cannulation stratery (peripheral cannulation) will be al-

tered and may require deep hypothermic circulatory ar-

rest to replace and clamp the aorta.

3.4. Cost

Goldstein, et al. reported their data on cost data in pa-

tients who underwent MDCTA prior to reoperative car-

diac surgery and compared to group who did not undergo

MDCTA [22]. $1150 was charged to MDCTA patients

for preoperative testing. MDCTA group had lower me-

dian recovery room and nursing charges, but higher op-

erative room charges. Despite the additional charge for

MDCTA, MDCTA group had lower mean total hospital

charges ($163,000 vs $192,000; p ≤ 0.06).

3.5. Upcoming Technology

Dynamic MDCTA has recently been reported <ref Mal-

guria, et al. “Static and Cine CT Imaging to Identify and

Characterize Mediastinal Adhesions as a Potential Com-

plication Undergoing Redo Sternotomy.” AJR ACCEP-

TED FOR PUBLICATION NOT YET IN PRESS. In

addition to the distance used in most MDCTA studies,

this technique will take structure’s movement into ac-

count, therefore called 4-D-MDCTA. For instance, if the

RV is in close proximity to sternum yet has free move-

ment, this means that it may not be adherent or that the

adhesions are not severe. If the RV does not move at the

attachment to the sternum, this likely indicates severe

adhesion.

4. CONCLUSION

Although no randomized prospective study has been

performed to prove the role of preoperative MDCTA, it

is obvious that new piece of information provided by

MDCTA will give important clues to the surgeons per-

forming reoperative sternotomy. High risk findings will

alter surgeon’s operative strategy and may even lead to

cancellation or seek other procedures such as transcathe-

ter procedure. In conclusion, 3-D MDCTA provides im-

portant information in a high risk reoperative cardiac sur-

gery and lowers the frequency of injury to vital struc-

tures.

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