Arterial cannulation during minimally invasive cardiac surgery (MICS) may be obtained either through the femoral artery or the ascending aorta. Small diameters of the femoral arteries are usually a contraindication for peripheral cannulation; thus, a careful preoperative evaluation is recommended, avoiding an unnecessary exposure of the peripheral vessels that may result in incisional complications such as groin lymphocele1 or infections. We report our experience of preoperative evaluation by color Doppler echocardiography for patients scheduled for MICS.
MATERIAL AND METHODS
Between January 2009 and December 2011, a total of 155 patients were operated on for mitral valve (MV) disease or patent foramen ovale (PFO). The mean (SD) age was 62.24 (10.29) years for the MV group and 46.77 (13.27) years for the PFO group. There were 20 (30.8%) women in the MV group and 35 (72.9%) women in the PFO group. One hundred thirteen patients were approached by MICS through the fourth intercostal space, and arterial cannulation was peripheral (femoral artery). Forty-two patients were operated on via full sternotomy for different reasons: 6 patients for contraindications to femoral cannulation detected by ultrasound (see below) and 36 patients for surgeon’s skill (these patients did not undergo ultrasound evaluation of the femoral artery). No cases of conversion to full sternotomy are reported. Preoperative details are summarized in Table 1.
One hundred nineteen patients scheduled for MICS were screened by ultrasound evaluation before the induction of anesthesia, by means of a vascular linear probe. Usually, the evaluation was carried out by the surgeon who decided about the surgical strategy. The common femoral artery was scanned in the anteroposterior and antero-oblique projections (Fig. 1). Direction of the ultrasound beam was made as perpendicular to the arterial wall as possible, with the focus zone indicator in the middle of the arterial lumen. The aim of the ultrasound evaluation was to measure the diameters and to inspect the wall: bright areas with shadows were considered as suggestive of calcifications.
Three parameters were considered to discriminate the suitability of the femoral artery for cannulation:
* longitudinal axis (LA): greater than 7 mm, femoral cannulation allowed; 6.5 to 7 mm, peripheral cannulation possible; less than 6.5 mm, peripheral cannulation avoided
* transverse axis (TA): greater than 7 mm, femoral cannulation allowed; 6.5 to 7 mm, peripheral cannulation possible; less than 6.5 mm, peripheral cannulation avoided
* atherosclerotic disease (AD): bright areas with shadows almost circumferential (porcelain wall) were considered as widespread AD. Two or more bright areas with shadows not circumferential were considered as AD. Moreover, an isolated calcification associated with thickening of the wall2 (intima + media + adventitia of >1.5 mm) was also considered as AD. In case of widespread disease, peripheral cannulation was avoided. In case of femoral artery with LA or TA of 6.5 to 7 mm associated with AD not widespread, peripheral cannulation was performed.
The patients were allocated to three different groups according to the diameters of the femoral artery:
* group A: 69 patients with LA and TA greater than 7 mm
* group B: 34 patients with LA and/or TA of 6.5 to 7 mm
group B1: 6 patients with widespread AD
group B2: 25 patients without AD
group B3: 3 patients with AD (not widespread)
* group C: 16 patients with LA and TA less than 6.5 mm
In the patients with risk factors of AD (age, smoking, diabetes, and hypertension), the abdominal aorta and iliac arteries were evaluated during coronary angiography. In the patients who did not undergo preoperative angiography (usually young people scheduled for PFO closure), the abdominal aorta and iliac arteries were scanned by preoperative ultrasound. No patient was excluded for aortic disease.
In case of peripheral arterial cannulation for MICS, we used the FemFlex Femoral Artery Cannula 20F/22F (Edwards Lifesciences, Irvine, CA USA), inserted into a 5-0 polypropylene purse string. After cardiopulmonary bypass institution, the aortic cross clamp was obtained by a transcutaneous Chitwood clamp inserted through the second intercostal space, and the heart was protected by blood cardioplegia.
The results are summarized in Table 2.
Group A (Diameters of >7 mm)
Sixty-nine patients were operated on via right thoracotomy because both the LA and the TA were greater than 7 mm: the peripheral cannulation was easily performed using a 22F arterial cannula, regardless of the AD. No complications such as femoral artery dissection or conversions to full sternotomy are reported.
Group B (Diameters of 6.5–7 mm)
Thirty-four patients had LA and/or TA of 6.5 mm to 7 mm. Six patients were operated on via full sternotomy, whereas 28 patients were operated on via right thoracotomy. In six patients (group B1) with widespread AD (multiple bright areas with shadows almost circumferential), peripheral cannulation was avoided and the operation was performed through a full sternotomy. In 28 cases, the femoral artery was cannulated: 25 patients (group B2) had no AD and 3 patients (group B3) had AD (two or more bright areas with shadows not circumferential or isolated plaque with total wall thickness of >1.5 mm). In group B2, no complications are reported. In group B3, all patients had a peripheral dissection of the femoral artery, requiring patch enlargement.
Group C (Diameters of <6.5 mm)
Sixteen patients had LA and TA less than 6.5 mm, and peripheral cannulation was avoided because of the high risk for peripheral injuries. This is a limitation of this study.
Femoral artery cannulation is widely used in cardiac surgery in case of minimally invasive approaches. The discussion about the preoperative evaluation of patients scheduled for femoral artery cannulation is ongoing: in fact, direct inspection of the femoral artery cannot discriminate the suitability for cannulation because it does not mean that if the femoral artery looks normal, then the iliacs or the aorta is normal. The structure of the aorta is usually evaluated by multislice computed tomography scan or magnetic resonance imaging to detect iliacs and/or aorta stenoses, dissections, or atherosclerotic debris.
Peripheral cannulation is contraindicated and central cannulation is recommended in case of aorto-iliac arterial disease, femoral artery size of less than 21F (7 mm), obesity.
We present the experience of preoperative evaluation by ultrasound to discriminate the suitability of the femoral artery for cannulation in patients with no other contraindications for peripheral cardiopulmonary bypass.
Our population had a low risk for AD because it was composed mainly of young patients scheduled for PFO closure. Preoperative evaluation was as follows: The patients without the risk factors of AD (older than 55 years, diabetes, hypertension, and dyslipidemia) were evaluated by preoperative ultrasound of the femoral artery, of the abdominal aorta, and of the iliac artery. The patients with the risk factors of AD were evaluated simultaneously by coronary and abdominal angiography; thus, preoperative ultrasound was focused on the femoral artery. This management allows discriminating the presence of aorto-iliac disease, which contraindicates peripheral cannulation.
The role of the color Doppler echocardiography for preoperative evaluation of patients scheduled for femoral artery cannulation has not yet been discussed. The aim of this article was to discuss the applications of the Doppler echocardiography in evaluating the suitability of the femoral artery for cannulation in patients undergoing MICS and with no other contraindications for peripheral cannulation (aorto-iliac disease).
Many complications are described during cardiopulmonary bypass through the femoral artery, such as embolism or systemic hypoperfusion, that are not reported in our series. Peripheral complications such as vascular injuries (2.6%), incisional complications (2.6%), or infection (0%) are quite rare in our series. The most common incisional complication is lymphocele, a well-known and feared drawback after procedures involving the femoral vessels, and its treatment lacks standardization.1 Thus, surgical exposure of the femoral vessels may be burdened by challenging complications, and unnecessary incisions should be avoided as much as possible. Six patients in our series were switched to full sternotomy for widespread AD of the femoral artery, detected by preoperative ultrasound, and they did not have an unnecessary incision.
Another issue to debate is the use of shunts for distal perfusion of the leg, which may prevent complications such as compartment syndrome, a constellation of symptoms and signs associated with abnormally elevated pressure of the extremities where muscles are enveloped in fasciae.4 No cases of compartment syndrome requiring fasciotomy are reported, even though we did not use shunts for the short time of cardiopulmonary bypass and mild hypothermia (about 32°C).
Our experience confirms that peripheral cannulation was safe in patients with femoral artery greater than 7 mm. In case of diameters 6.5 to 7 mm, peripheral cannulation had no complications when the arterial wall was normal (25 patients), whereas AD (3 patients) was a predictor of vascular complications.
Femoral arteries less than 6.5 mm were excluded from peripheral cannulation for the high incidence of vascular injuries4 and the risk for a challenging surgical repair. This is a limitation of this study.
The advantages of preoperative Doppler echocardiography are that there is complete assessment of the characteristics of the femoral artery, including diameters (TA and LA) and AD. Atherosclerotic disease is a predictor of the risk for vascular injury in case of small femoral arteries (<7 mm) due to worsening elasticity of the wall. Also, measurement by ultrasound is more reliable than direct inspection in predicting size because surgical exposure of the femoral artery may induce vasospasm. However, suitability for cannulation depends upon AD.
The decision as to which approach has to be used (ie, MICS or sternotomy) depends on several factors, such as absence of aortic or iliac disease, chest conformation, and absence of pleural adhesions.
Diameters of the femoral artery and presence of AD may discriminate suitability for peripheral cardiopulmonary bypass exclusively for patients with no other contraindications.
Peripheral arterial cannulation of vessels greater than 7 mm is safe because we experienced no complications in 69 patients. In case of diameters 6.5 to 7 mm, peripheral cannulation should be avoided in case of presence of calcifications; in fact, 3 patients in our series with AD had vascular injuries; 25 patients without femoral artery AD had no complications. Cannulation was avoided in six patients with widespread AD. In case of diameters less than 6.5 mm, peripheral cannulation was avoided. However, it is hard to know whether any of these patients were suitable candidates for peripheral cannulation because there was no attempt to peripherally cannulate, so we are not certain whether they could have been cannulated. In fact, because none of the 16 patients with vessels less than 6.5 mm had arterial complications, we do not know the rate of peripheral arterial complications in those patients. However, on the basis of previous experience that reported a safe cannulation for diameters4 greater than 7 mm, we decided to avoid cannulation for diameters less than 6.5 mm. Alternate approaches such as axillary artery cannulation should be considered, and in case of femoral artery diameters 6.5 to 7 mm with AD, the use of a side graft should be useful.
The main limitations of this study include its retrospective nature, the relatively small number of patients, the lack of any comparison population, and the fact that it is a limited single-center experience.
Thus, further experiences are required to validate the results presented in this article.
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This timely report examines the experience of the group from the Papardo Piemonte Hospital in Messina, Italy, on using ultrasound to evaluate the femoral artery before cannulation in patients undergoing a right minithoracotomy primarily for mitral valve repair or replacement. One hundred nineteen patients were screened before induction of anesthesia by means of a vascular linear probe. They found that peripheral arterial cannulation was safe in patients with vessels greater than 7 mm. In femoral arteries with diameters between 6.5 mm and 7 mm, they reported that cannulation should be avoided in the presence of calcification. Peripheral cannulation was avoided in all patients with a femoral artery less than 6.5 mm.
This is an interesting report. The reader should be careful in drawing any sweeping conclusions. It is a small series. Moreover, they cannot comment on the safety of cannulating femoral arteries less than 6.5 mm because this was avoided in this single-center experience. With the growing experience with transcatheter valve replacement, cardiac surgeons are commonly called on to evaluate the adequacy of the iliac and the femoral circulation. In general, multislice CT scanning is the recommended test and provides excellent information regarding iliac and femoral artery size, tortuosity, and calcification. It can also uncover other problems that can impact the safety of femoral cannulation such as descending thoracic and abdominal atherosclerotic aortic disease and the presence of abdominal aortic, iliac, or femoral dissections. Femoral artery ultrasound maybe a useful adjunct in some patients, as this study suggests, and it may be particularly useful in patients with a contraindication to CT angiography or who are younger and at relatively low risk for peripheral vascular disease, since it is a less-invasive approach.
Color Doppler echocardiography; Femoral arteries; Peripheral cannulation; Minimally invasive surgery; Cardiac surgery
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