Arterial inflow via an axillary artery graft for the severely atheromatous aorta

Contemporary utilization of the axillary artery in cardiac surgery

INTRODUCTION

The axillary artery is a reliable inflow vessel when addressing pathology of the aortic root and aortic arch that may preclude standard central cannulation strategies. This narrative review examines the use of the axillary artery in cardiac surgery. Anatomy, indications for use, cannulation strategies, and potential complications will be discussed.

METHODS

A comprehensive review of the current literature was performed using PubMed, Cochrane Review, and authoritative committee guidelines. A narrative review incorporating current available evidence was undertaken.

COMMENT

Use of the axillary artery in select cardiac surgical cases is reliable, reproducible, and may be preferable in certain cases involving ascending aortic pathology, reoperative surgery, porcelain aorta, access for transcatheter valve therapies, and peripheral mechanical circulatory support.

Cannulation strategies in aortic surgery: techniques and decision making

Arterial cannulation for cardiopulmonary bypass (CPB) is an important determinant of outcome in aortic surgery. Unlike traditional cardiac operations, aortic pathology may preclude the cannulation of the distal ascending aorta. In other cases, special need of the pathology/operation may demand an alternative cannulation site. Choosing the right cannulation site, especially in type A aortic dissection, is the most crucial initial step. The decision about cannulation sites should be individualized and patient-specific. Various cannulation techniques include femoral, right axillary, innominate, carotid, central aortic, direct true lumen, transapical, and trans-atrial left ventricle cannulation. The ideal cannulation should be easy, quick, and suitable for all clinical scenarios. It should allow smooth conduct of CPB without malperfusion or cerebral embolization. The cannulation strategy should also provide an option for selective antegrade cerebral perfusion and it should be free from neurovascular and local site complications. There is no ideal cannulation technique. Each technique has its pros and cons. Excellent results and drawbacks have been reported with each technique. Final selection of the cannulation site is dependent upon several factors. However, a surgeon's familiarity with a particular technique plays a major role in selection. Despite this, there is a definite shift in surgeons' preference from femoral to central cannulation (axillary, carotid, innominate, aortic) over the last few decades. The aim of this review is to give a brief overview of the cannulation techniques in aortic surgery and discuss the decision-making process.

Surgical strategies for severely atherosclerotic (porcelain) aorta during coronary artery bypass grafting

Porcelain aorta (PA) is an asymptomatic atherosclerotic disease, characterized by circumferential calcification throughout the whole perimeter of the aorta. It is seen in 2% to 9.3% of patients undergoing elective coronary artery bypass grafting (CABG) and makes manipulation of the ascending aorta impossible. It has been clearly shown that most emboli seen and detected during the CABG procedure occur during aortic cross-clamping and aortic side-clamping. Manipulation of porcelain or a severely atherosclerotic aorta increases the risk of perioperative stroke. The incidence of stroke after CABG is between 0.48% and 2.9%, and the risk is correlated with the extent and severity of the atherosclerotic disease. A conventional CABG procedure involves successive steps that include cannulation of the ascending aorta, application of a cross-clamp to the aorta, and partial clamping of the aorta to create the proximal anastomosis. Therefore in procedures that involve cannulation, clamping, or proximal anastomosis, and where aortic manipulation is inevitable, preassessment of the atherosclerotic aortic plaques is crucial. Although many surgeons still rely on intraoperative manual aortic palpation, this approach has very low sensitivity and underestimates the severity of the atherosclerotic illness. Imaging methods including preoperative computed tomography or intraoperative epiaortic ultrasonography enable modification of the surgical technique according to the severity of atherosclerosis. Various surgical techniques have been described to reduce the risk of atheroembolism that may lead to cerebrovascular events in patients with severely atherosclerotic ascending aorta. Anaortic or “no-touch” techniques that do not utilize aortic manipulation may significantly decrease the development of neurological complications by avoiding aortic maneuvers known to cause emboli. In cases where severe atherosclerotic disease or other factors preclude safe use of the ascending aorta, modifications in the surgical techniques, such as switching to different cannulation sites including the axillary/subclavian, femoral and innominate arteries, or using hypothermic ventricular fibrillation and in-situ pedicled arterial grafts, or performing proximal anastomoses at alternative anatomical locations will enable CABG operations to be performed safely with low morbidity and mortality rates in patients with porcelain aortas.

Evolution of surgical therapy for Stanford acute type A aortic dissection

Acute type A aortic dissection (AcA-AoD) is a surgical emergency associated with very high morbidity and mortality. Unfortunately, the early outcome of emergency surgical repair has not improved substantially over the last 20 years. Many of the same debates occur repeatedly regarding operative extent and optimal conduct of the operation. The question remains: are patients suffering from too large an operation or too small? The pendulum favoring routine aortic valve resuspension, when feasible, has swung towards frequent aortic root replacement. This already aggressive approach is now being challenged with the even more extensive valve-sparing aortic root replacement (V-SARR) in selected patients. Distally, open replacement of most of the transverse arch is best in most patients. The need for late aortic re-intervention has not been shown to be affected by more extensive distal operative procedures, but the contemporary enthusiasm for a distal frozen elephant trunk (FET) only seems to build. It must be remembered that the first and foremost goal of the operation is to have an operative survivor; additional measures to reduce late morbidity are secondary aspirations. With increasing experience, true contraindications to emergency surgical operation have dwindled, but patients with advanced age, multiple comorbidities, and major neurological deficits do not fare well. The endovascular revolution, moreover, has spawned innovative options for modern practice, including ascending stent graft and adaptations of the old flap fenestration technique. Despite the increasingly complex operations and ever expanding therapies, this life-threatening disease remains a stubborn challenge for all cardiovascular surgeons. Development of specialized thoracic aortic teams and regionalization of care for patients with AcA-AoD offers the most promise to improve overall results.

Intraoperative 16-Channel Electroencephalography and Bilateral Near Infrared Spectroscopy Monitorization in Aortic Surgery

Transient neurologic dysfunction is common after aortic surgery. Major causes of postoperative complications followed by cardiac surgery are due to hypoperfusion states such as selective cerebral perfusion, embolic debris during cardiopulmonary bypass and ulcerated plaque emboli originated from carotid arteries. Neurologic complications prolong periods of intensive care unit and hospital stay, worsens quality of life and unfortunately they are an important cause of morbidity. Anaesthesia during a carotid and aortic surgery constitutes of providing adequate brain perfusion pressure, attenuating cerebral metabolism by anaesthetic agents and monitoring the cerebral metabolic supply and demand relationship during the intraoperative period. We present a monitoring approach with an intraoperative 16-channel electroencephalography and bilateral near infrared spectroscopy during redo aneurysm of the sinus of Valsalva surgery.

The application of a modified technique of SCP under DHCA during total aortic arch replacement combined with stented elephant trunk implantation

We reviewed the perfusion experiences of 60 cases with a modified technique of selected cerebral perfusion (SCP) under deep hypothermic circulatory arrest (DHCA) during ascending aorta and total aortic arch replacement combined with transaortic stented graft implantation into the descending aorta for acute and chronic type A aortic dissection. Right auxiliary artery cannulation was routinely used for cardiopulmonary bypass (CPB) and SCP in this procedure. Generally, this technique requires two main pumps for two arterial lines before we applied the modified technique; one for CPB and the other for SCP. In order to simplify the circuit of the extracorporeal circuit (ECC) to operate easily, the arterial line was separated into two branches with a Y–connector on the operating table, one for axillary artery perfusion and the other for graft perfusion connected to the ECC set–up. This method is easy for the perfusionist to install and convenient for the surgeon. This is a safe and simple to use modified technique for SCP under DHCA during ascending aorta and total aortic arch replacement combined with transaortic stented graft implantation into the descending aorta.

Bilateral Axillary Arterial Perfusion in Surgery on Thoracic Aorta

Bilateral axillary arterial cannulation for selective cerebral perfusion might minimize cerebral embolic complications during surgery on the ascending aorta and aortic arch. From March 2002 through February 2004, bilateral axillary arterial perfusion was applied in 12 consecutive patients (mean age, 61.3 years). Operative procedures were total arch replacement in 8 patients, hemiarch replacement in 1, and ascending aorta replacement in 3. Antegrade selective cerebral perfusion was established through vascular grafts anastomosed to the bilateral axillary arteries and a perfusion catheter placed directly into the left carotid artery. Bilateral axillary arterial perfusion through the grafts was successful in all patients. There were no early or late deaths and no incidence of neurologic deficit. There were no complications related to cannulation of the axillary arteries. Bleeding, temporary renal failure, acute respiratory distress syndrome, and graft infection occurred in one patient each; all recovered from these complications. Bilateral axillary arterial perfusion is feasible and effective for brain protection during surgery on the ascending aorta and aortic arch.

Numerical simulation of blood flow in femoral perfusion: comparison between side-armed femoral artery perfusion and direct femoral artery perfusion

Computational numerical analysis was performed to elucidate the flow dynamics of femoral artery perfusion. Numerical simulation of blood flow was performed from the right femoral artery in an aortic model. An incompressible Navier-Stokes equation and continuity equation were solved using computed flow dynamics software. Three different perfusion models were analyzed: a 4.0-mm cannula (outer diameter 15 French size), a 5.2-mm cannula (18 French size) and an 8-mm prosthetic graft. The cannula was inserted parallel to the femoral artery, while the graft was anastomosed perpendicular to the femoral artery. Shear stress was highest with the 4-mm cannula (172 Pa) followed by the graft (127 Pa) and the 5.2-mm cannula (99 Pa). The cannula exit velocity was high, even when the 5.2-mm cannula was used. Although side-armed perfusion with an 8-mm graft generated a high shear stress area near the point of anastomosis, flow velocity at the external iliac artery was decreased. The jet speed decreased due to the Coanda effect caused by the recirculation behind sudden expansion of diameter, and the flow velocity maintains a constant speed after the reattachment length of the flow. This study showed that iliac artery shear stress was lower with the 5.2-mm cannula than with the 4-mm cannula when used for femoral perfusion. Side-armed graft perfusion generates a high shear stress area around the anastomotic site, but flow velocity in the iliac artery is slower in the graft model than in the 5.2-mm cannula model.

Open Seldinger-Guided Femoral Artery Cannulation Technique for Thoracic Aortic Surgery

BACKGROUND

Debate regarding the optimal cannulation site for aortic surgery continues. We report our recent experience with a simple and rapid open Seldinger-guided technique for femoral cannulation. Aside from speed and simplicity (no need for arterial incision or suture closure), this technique has the added benefit that the distal limb continues to be perfused, as no arterial snare is required.

METHODS

We recently began routinely utilizing an open Seldinger-guided technique for femoral artery cannulation. The artery is exposed surgically but cannulated by guidewire inside a pursestring without arterial incision. The pursestring is simply tied when decannulation is performed. We report our experience with the routine application of this technique from August 2011 to April 2015.

RESULTS

We reviewed the outcome of 337 consecutive peripheral arterial cannulations performed for thoracic aortic surgery (303 femoral, 34 axillary) using the open Seldinger technique. Within the femoral cannulation group, the hospital survival rate was 97% (295 of 303). The survival rate for elective operations was 98% (277 of 283), and 90% (18 of 20) for emergent/urgent. Seldinger-guided femoral cannulation was performed for replacement of the ascending/aortic arch in 88% (266 of 303), the descending thoracic aorta in 7% (22 of 303), and the thoracoabdominal aorta in 5% (15 of 303). There were no instances of intraoperative malperfusion phenomena, arterial dissection, or vascular injury or rupture. No patients had postoperative acute limb ischemia. Local wound complications were observed in 1% of patients (3 of 303). The stroke rate was 1.6% (5 of 303). The same open Seldinger technique was also used without complication in the axillary cannulation group.

CONCLUSIONS

An open Seldinger-guided femoral (or axillary) cannulation technique is quick and easy to perform, with minimal vascular or other complications and extremely low risk of stroke. This technique is recommended for its speed, simplicity, and effectiveness, and for its preservation of distal arterial flow (which is occluded with the traditional arterial incision/arterial snare technique).

Blood flow analysis of the aortic arch using computational fluid dynamics

OBJECTIVES

To obtain predictive information regarding aortic disease, we evaluated how blood flow inside the aortic arch was influenced by thoracic aortic aneurysms. In addition, to reveal the optimal intraoperative management in these cases, we examined blood flow during right subclavian arterial (rSCA) perfusion using computational fluid dynamics (CFD).

METHODS

Patient-specific models of the aortic arch were made with six different patterns based on the computed tomographic images. CFD models with finite volume methods were created to simulate the physiological pulsatile flow including the peripheral reflection wave, characteristic impedance and autonomous regulation system. Flow stream patterns, wall shear stress (WSS) and the oscillatory shear index (OSI) were calculated during one cardiac cycle. Furthermore, flow streamlines during rSCA perfusion were simulated under different perfusion flows.

RESULTS

Aortic dilatation caused vortical disturbed flow in a dilated space, resulting in turbulent flow not only inside the aneurysm but also in the proximal and/or distal normal aortic portion. In patients with a dilated thoracic aorta, there was a helical spiral flow with a circumferential vortex in systole. In patients with an arch aneurysm, turbulent flow inside the aneurysm caused a high OSI at the tip of the aneurysm. A high OSI was detected at the orifice of the supra-aortic branches, sinotubular junction, posterior lateral side of the ascending aorta and lesser curvature of the proximal descending aorta. rSCA perfusion revealed that the right common carotid artery was perfused by blood flow from rSCA throughout the cardiac cycle. With 75% of the flow from the rSCA, blood flow from the heart reached the left common carotid and subclavian artery only during a short period during the peak of systole.

CONCLUSIONS

A dilated aorta causes a turbulent flow pattern in the aortic arch. The high OSI site was similar to the favourite entry site for acute aortic dissection, indicating the causal relationship between mechanical stress and acute aortic dissection. rSCA cannulation might be cerebroprotective from ascending aortic plaque.

Cannulation in aortic surgery: subclavian and axillary cannulation

Cannulation of peripheral vessels is being frequently used as a standard access for establishing cardiopulmonary bypass (CPB) in recent times. Apart from an increased use in patients requiring left ventricular circulatory support, i.e. either extracorporeal membrane oxygenation or long-term ventricular assist device systems, peripheral vessel cannulation is also beneficial in aortic surgery. The subclavian and axillary arteries are commonly used as sites for arterial cannulation to establish CPB during aortic surgery in many centres. Both cannulation sites enable safe implementation of CPB in patients requiring complex and difficult reoperations and those undergoing aortic surgery for acute type A aortic dissections or artherosclerotic aortic disease, in which cerebral perfusion is required. Here, we describe our techniques of direct cannulation of the subclavian and axillary artery for aortic arch surgery.

Axillary artery cannulation

Axillary artery cannulation is indicated mainly during surgery involving the aortic root and the aortic arch when the pathology precludes a standard cannulation of the ascending aorta. Axillary cannulation provides an antegrade systemic flow, allows easy initiation of antegrade cerebral perfusion during circulatory arrest and reduces the rate of retrograde cerebral embolization compared with a femoral cannulation. Experimentally, axillary cannulation has been shown to reduce cerebral emboli compared with a standard ascending aortic cannulation. Axillary artery cannulation can be used as the procedure of choice in cases of ascending aortic aneurysm extending in the arch, isolated arch aneurysms, type A aortic dissection, porcelain aorta, re-operations of the thoracic aorta and other miscellaneous indications.

Right axillary arterial perfusion for descending thoracic or thoracoabdominal aortic aneurysm repair with open proximal anastomosis through left thoracotomy

BACKGROUND

We examined the effectiveness of right axillary arterial perfusion through an interposed Dacron graft in the prevention of cerebral embolism or complications related to ascending aortic cannulation in open proximal anastomosis technique of descending thoracic aortic aneurysm (TAA) or thoracoabdominal aortic aneurysm (TAAA) repair under deep hypothermic circulatory arrest through left thoracotomy.

METHODS

Between May 2000 and August 2012, 44 patients underwent TAA or TAAA repair using open proximal technique under DHCA. These patients were divided into two groups for evaluation of the effectiveness of right axillary arterial perfusion. Group A included patients who underwent TAA or TAAA repair with ascending aortic cannulation (n=15). Group B was composed of patients who had TAA or TAAA repair with right axillary arterial perfusion through the interposed Dacron graft (n=29).

RESULTS

Mortality in this series was 4.5% (2 of 44 patients; 1 in each group); wherein, the causes were sepsis due to graft infection and aortic dissection (Stanford type A). The incidence rates of cerebral embolism were 27 % (4 of 15 patients in group A) and 3.4% (1 of 29 patients in group B) (p=0.0392, Fisher's exact test). The rates of complications in relation to the aortic cannulation site (dissection or bleeding) were 13% (2 of 15 patients in group A) and 0% (0 of 25 patients in group B).

CONCLUSIONS

Right axillary perfusion facilitates easy evacuation of air and allows prompt recommencement of upper body circulation. Consequently, it minimizes the risk of cerebral embolism or complications in relation to aortic cannulation through left thoracotomy.

Extraanatomical coronary artery bypass grafting in patients with severely atherosclerotic (Porcelain) aorta

Background

Cannulation, cross clamping, or partial clamping of the aorta during a proximal anastomosis may cause embolic complications in patients with severely atherosclerotic (porcelain) aortas. These patients carry high morbidity and mortality risks due to intraoperative atheroembolism.

Methods

Between June 2008 and May 2010, 972 open heart surgery operations were performed in our department. In this group there were 41 patients who had severe atherosclerotic plaques in the aorta (porcelain aorta), and 9 of these underwent an extraanatomical coronary artery bypass grafting (CABG). These 9 patients were retrospectively analyzed and their demographic data, patient risk factors, and preferred surgical methods were reviewed.

Results

Seven patients underwent two-vessel CABG, while 2 underwent three-vessel CABG. Off-pump surgery was performed for 7 patients. CABG was performed with beating heart technique under cardiopulmonary bypass via femoral artery and right atrial cannulation without cross clamping in 2 of the patients. Postoperative course was uneventful in all patients. Mean length of stay in the intensive care unit was 2.11 ± 0.78 days. Mean hospitalization was 7.22 ± 0.97 days. Mean follow-up was 11.33 ± 3.67 months, and no cerebrovascular events were observed during this period. Postoperative evaluation of the grafts by multislice computed tomography revealed sufficient patency in all patients.

Conclusions

Innominate artery is an alternative inflow source for the untouchable ascending aorta caused by severe atherosclerotic disease (porcelain aorta). In this group of patients, the risk of systemic embolisation and perioperative neurologic complications can be minimized by avoiding manipulation of the ascending aorta and using the innominate artery.

Comparison of the Outcomes between Axillary and Femoral Artery Cannulation for Acute Type A Aortic Dissection

Background

At present, many surgeons prefer axillary artery cannulation because it facilitates antegrade cerebral perfusion and may diminish the risk of cerebral embolization. However, axillary artery cannulation has not been established as a routine procedure because there is controversy about its clinical advantage.

Materials and Methods

We examined 111 patients diagnosed with acute type A aortic dissection between January 2000 and December 2009. The right axillary artery was cannulated in 58 patients (group A) and the femoral artery was cannulated in 53 (group F). The postoperative outcomes were retrospectively reviewed and compared between the two groups.

Results

There were 46 male and 65 female patients with a mean age of 58.9±13.1 years (range, 26 to 84 years). The extent of aortic replacement in both groups did not differ. There were 8 early deaths (7.2%) and 2 late deaths (1.8%). The mean follow-up duration was 46.0±32.6 months (range, 1 month to 10 years). Transient neurologic dysfunction was observed in 11 patients (19.0%) in group A and 14 patients (26.4%) in group F. A total of 11 patients (9.9%) suffered from a permanent neurologic dysfunction. Early and delayed stroke were observed in 6 patients (10.3%) and 2 patients (3.4%), respectively, in group A as well as 2 patients (3.8%) and 1 patient (1.9%), respectively, in group F. There were no statistical differences in the cannulation-related complications between both groups (3 in group A vs. 0 in group F).

Conclusion

There were no differences in postoperative neurologic outcomes and cannulation-related complications according to the cannulation sites. The cannulation site in an aortic dissection should be carefully chosen on a case-by-case basis. It is important to also pay attention to the possibility of intraoperative malperfusion syndrome occurring and the subsequent need to change the cannulation site.

Evidence, lack of evidence, controversy, and debate in the provision and performance of the surgery of acute type A aortic dissection

Acute type A aortic dissection is a lethal condition requiring emergency surgery. It has diverse presentations, and the diagnosis can be missed or delayed. Once diagnosed, decisions with regard to initial management, transfer, appropriateness of surgery, timing of operation, and intervention for malperfusion complications are necessary. The goals of surgery are to save life by prevention of pericardial tamponade or intra-pericardial aortic rupture, to resect the primary entry tear, to correct or prevent any malperfusion and aortic valve regurgitation, and if possible to prevent late dissection-related complications in the proximal and downstream aorta. No randomized trials of treatment or techniques have ever been performed, and novel therapies-particularly with regard to extent of surgery-are being devised and implemented, but their role needs to be defined. Overall, except in highly specialized centers, surgical outcomes might be static, and there is abundant room for improvement. By highlighting difficulties and controversies in diagnosis, patient selection, and surgical therapy, our over-arching goal should be to enfranchise more patients for treatment and improve surgical outcomes.

Avoiding stroke during cardiac surgery

The life saving benefits of cardiac surgery are frequently accompanied by negative side effects such as stroke, that occurs with an incidence of 2%-13% dependent to type of surgery. The etiology is most likely multifactorial with embolic events considered as main contributor. Although stroke presents a common complication, no guidelines for any routine use of pharmacological substances or non-pharmacological strategies exist to date. Non-pharmacological strategies include monitoring of brain oxygenation and perfusion with devices such as near infrared spectroscopy and Transcranial Doppler help. Epiaortic and transesophageal echocardiography visualize aorta pathology, enabling the surgeon to sidestep atheromatous segments. Additionally can the use of specially designed aortic cannulae and filters help to reduce embolization. Brain perfusion can be improved by using antero- or retrograde cerebral perfusion during deep hypothermic circulatory arrest, by tightly monitoring mean arterial blood pressure and hemodilution. Controlling perioperative temperature and glucose levels may additionally help to ameliorate secondary damage. Many pharmacological compounds have been shown to be neuroprotective in preclinical models, but clinical studies failed to confirm these results so far. Remacemide, an NMDA-receptor-antagonist showed a significant drug-based neuroprotection during cardiac surgery. Other substances currently assessed in clinical trials whose results are still pending are acadesine, an adenosine-regulating substance, the free radical scavenger edaravone and the local anesthetic lidocaine. Stroke remains as significant complication after cardiac surgery. Non-pharmacological strategies allow perioperative caregivers to detect injurious events and to ameliorate stroke and its sequelae. Considering the multi-factorial etiology though, stroke prevention will likely have to be addressed with an individualistic combination of different strategies and substances.

Common hepatic artery as an inflow site for off-pump coronary artery bypass grafting

We used the common hepatic artery (CHA) as an inflow site for a saphenous vein graft bypass to the right coronary system during off-pump coronary artery bypass grafting. The CHA is a suitable inflow vessel to provide sufficient blood flow and a short-distance bypass in case both the ascending aorta and the gastroepiploic artery are considered inadequate.

Axillary Versus Femoral Cannulation for Aortic Surgery: Enough Evidence for a General Recommendation?

There is a trend towards cannulation of the axillary artery for extracorporeal circulation in patients requiring aortic arch surgery. We analyzed the published data comparing axillary and femoral cannulation for safety and outcome. End points were death; stroke, neurologic, and vascular complications; and malperfusion. Femoral cannulation is safe for extracorporeal circulation in patients without aortic arch surgery. In patients with type A dissections, malperfusion may occur owing to retrograde perfusion of the false lumen and subsequent occlusion of the origin of the supra aortic vessels. Cannulation of the axillary/subclavian artery results in antegrade flow, at least in the right carotid artery, with the possibility of antegrade cerebral perfusion during aortic arch repair. There was a trend towards improved neurologic outcome when the axillary artery was used for extracorporeal circulation in such patients. When different techniques were compared, the use of a side graft for axillary cannulation reduced the complication rate. The lack of randomized trials and the high variety of inclusion criteria in the different studies do not allow a general recommendation for the use of the axillary artery as cannulation site.

Experimental safety and efficacy evaluation of an extracorporeal pumpless artificial lung in providing respiratory support through the axillary vessels

OBJECTIVE

We sought to investigate the safety and feasibility of implanting the pumpless interventional lung assist device (Novalung; Novalung GmbH, Hechingen, Germany) to the axillary vessels either by means of direct cannulation or end-to-side graft interposition and the capability of either type of vascular access to provide respiratory support during apneic ventilation in adult pigs.

METHODS

Ten pigs were ventilated for 4 hours (respiratory rate, 20-25 breaths/min; tidal volume, 10-12 mL/kg; fraction of inspired oxygen, 1.0; positive end-expiratory pressure, 5 cm H2O). Thereafter, the interventional lung assist device was surgically connected to the right axillary artery and vein by using direct cannulation (n = 5) or end-to-side ringed polytetrafluoroethylene graft interposition (n = 5), and ventilatory settings were reduced to achieve near apneic ventilation (respiratory rate, 4 breaths/min; tidal volume, 1-2 mL/kg; fraction of inspired oxygen, 1.0; positive end-expiratory pressure, 20 cm H2O). Hemodynamic and intrathoracic volumes and lung cytokine levels were measured.

RESULTS

Blood flow through the interventional lung assist device was 1.7 +/- 0.4 L/min or 30% +/- 14% of the cardiac output, and the mean pressure gradient across the interventional lung assist device was 10 +/- 2 mm Hg. The interventional lung assist device allowed an O2 transfer of 225.7 +/- 70 mL/min and a CO2 removal of 261.7 +/- 28.5 mL/min. Although the amount of blood flow perfusing the interventional lung assist device was significantly higher (P < .01) with direct cannulation (2.1 +/- 0.3 L/min) compared with that seen in graft interposition (1.3 +/- 0.3 L/min), the latter allowed similar respiratory support with reduced hemodynamic instability.

CONCLUSIONS

The axillary vessels are a safe and attractive cannulation site for pumpless partial respiratory support. Compared with direct cannulation, graft interposition was equally able to support the interventional lung assist device-driven gas exchange requirements during apneic ventilation with better hemodynamic stability.

Incomplete Circle of Willis and Right Axillary Artery Perfusion

BACKGROUND

The aim of our anatomic study was to assess whether the commonly used method of perfusion through the right axillary artery is sufficient in providing uniform distribution of blood to both hemispheres of the brain in patients undergoing surgery of the aortic arch. We considered that critical arteries to examine are anterior and left posterior communicating arteries of the circle of Willis because the absence or insufficiency of either one would drastically endanger perfusion to the left hemisphere of the brain. The existence and the diameters of these arteries were studied.

METHODS

The material was collected as a part of normal forensic medicine autopsies. The anatomy of the cerebral arteries of 87 deceased individuals was assessed by angiography and permanent silicone casts. A new classification was created for this study. According to a recent observation in the literature we defined the minimum threshold of arterial diameter that allows cross flow to be 0.5 mm. We also repeated analyses using 1 mm as a threshold, which has also been recommended.

RESULTS

In our material 22% of the anterior communicating arteries and 46% of the left posterior communicating arteries were missing. In this anatomic population the perfusion to the left hemisphere might have been insufficient in 14% of the patients at a threshold of 0.5 mm and in 17% at a threshold of 1 mm.

CONCLUSIONS

When the right axillary artery is used for perfusion, the circulation to the contralateral hemisphere seems to be good for most patients undergoing operations of the aortic arch, but additional means of brain protection are still needed.

Aortic Arch Reconstruction: Safety of Moderate Hypothermia and Antegrade Cerebral Perfusion During Systemic Circulatory Arrest

BACKGROUND AND AIM

The ideal strategy for cerebral protection during aortic arch (AA) reconstructive surgery remains undefined. Antegrade cerebral perfusion (ACP) during systemic circulatory arrest (SCA) may provide superior results; however, optimal systemic temperature is undetermined. Our objective was to determine whether "deep" hypothermia is necessary during ACP with SCA, and whether the degree of hypothermia is associated with neurologic outcomes postoperatively.

METHODS

Retrospective series of 72 consecutive patients (aged 65.9 +/- 3.2 years) who underwent AA reconstructive surgery at Vancouver General Hospital using a cerebral protection strategy of ACP with SCA between December 1995 and December 2002. Patients were divided into two groups according to lowest systemic temperature: <22 degrees C (n = 52) and > or =22 degrees C (n = 20).

RESULTS

ACP was via right axillary or innominate artery, +/- left common carotid cannulation. Median SCA time with ACP was not different between groups. There were four hospital deaths (5.6%) (three from the <22 degrees C group). Eight patients (11.2%) had major neurologic injuries (seven from the <22 degrees C group): 4 (5.6%) permanent (1 fatal) and 4 (5.6%) temporary. There was a trend toward a significantly higher incidence of delirium in the <22 degrees C group than the > or =22 degrees C group (30.8 vs 10.0%, respectively, p = 0.07).

CONCLUSIONS

In our experience, SCA with ACP was a safe technique for AA reconstructive surgery. The observation of a larger number of major neurologic injuries, and a trend toward a higher incidence of delirium in the <22 degrees C group, suggests that systemic temperatures below 22 degrees C may not be necessary and may be associated with a higher incidence of neurologic injury when using ACP during SCA.

No-Clamp Technique for Valve Repair or Replacement in Patients With a Porcelain Aorta

BACKGROUND

Patients requiring valvular heart surgery may have circumferential calcification of the ascending aorta. A variety of creative procedures have been described for managing this "porcelain aorta." We describe a technique based on replacement of the ascending aorta and proximal arch under profound hypothermic circulatory arrest, followed by the valve procedure.

METHODS

Twenty-five consecutive patients with a porcelain aorta were referred for heart valve surgery. In every case the aorta was replaced under circulatory arrest before the valve procedure. Postoperative morbidity, mortality, and univariate risk factors for death were calculated. Fisher's exact test defined significant perioperative variables with a p value less than 0.05.

RESULTS

Of 25 patients, 23 (92%) survived the surgery to hospital discharge. One patient had a stroke (4%) and 2 patients (8%) required reexploration for bleeding. Risk factors for perioperative death by univariate analysis included age more than 78 years (p < 0.009), cardiopulmonary bypass time longer than 200 minutes (p < 0.0001), reexploration for bleeding (p < 0.02), need for intra-aortic balloon pump support (p < 0.001), and postoperative gastrointestinal complications (p < 0.001).

CONCLUSIONS

Valve replacement or repair in the patient with a porcelain aorta can be safely accomplished with a technique based on aortic replacement under circulatory arrest. Elderly patients requiring extensive procedures and prolonged periods on bypass have a substantially increased risk for postoperative complications and death.

Axillary Artery Cannulation Improves Operative Results for Acute Type A Aortic Dissection

BACKGROUND

This study was undertaken to identify preoperative and postoperative predictors of hospital death of patients with acute type A aortic dissection.

METHODS

Between May 1,1992, and July 31, 2004, 106 consecutive patients (59 male and 47 female, mean age 62.2 +/- 12.1 years) with acute type A aortic dissection underwent surgery with open technique and cerebral protection by antegrade selective cerebral perfusion. The external iliac artery or femoral artery alone was used for arterial cannulation in 37 patients; however, the right axillary artery was cannulated in 69 patients. Univariate analysis of potential risk factors was performed to identify risk factors for hospital death and was followed by multivariate analysis by a stepwise logistic regression model to identify independent risk factors.

RESULTS

Sixteen patients died postoperatively, and the overall hospital mortality rate was 15.1%. Univariate analysis revealed shock (p = 0.020), visceral ischemia (p = 0.007), root replacement (p = 0.041), and absence of axillary artery perfusion (p = 0.003) as significant risk factors for hospital death. Multivariate analysis revealed visceral ischemia (p = 0.0028, odds ratio 18.4) and absence of axillary artery perfusion (p = 0.0014, odds ratio 8.2) as independent preoperative and intraoperative predictors of hospital death.

CONCLUSIONS

Achievement of greater success in the surgical treatment of acute type A dissection will require axillary artery cannulation and measures to prevent visceral malperfusion.

Does the arterial cannulation site for circulatory arrest influence stroke risk?

BACKGROUND

We investigated whether axillary/subclavian artery inflow with a side graft decreases the risk of stroke versus cannulation at other sites during hypothermic circulatory arrest.

METHODS

Between January 1993 and May 2003, 1,352 operations with circulatory arrest were performed for complex adult cardiac problems. A single arterial inflow cannulation site was used in 1,336 operations, and these formed the basis for comparative analyses. Cannulation sites were axillary plus graft in 299 operations, direct cannulation of the aorta in 471, femoral in 375, innominate in 24, and axillary or subclavian without a side graft in 167. Retrograde brain perfusion was used in 933 (69%). A total of 272 (20%) were for emergencies, 432 (32%) were reoperations, and 439 (32%) were for dissections. A total of 617 (46%) had aortic valve replacement and 1,160 (87%) ascending, 415 arch (31%), and 248 descending (18%) aortic replacements. Indications also included arteriosclerosis (n = 301) and calcified aorta (n = 278). Primary comparisons were made by using propensity matching, and, secondarily, risk factors for stroke or hospital mortality were identified by multivariable logistic regression.

RESULTS

Stroke occurred in 6.1% of patients (81/1,336): 4.0% (12/299) of those had axillary plus graft and 6.7% who had direct cannulation (69/1,037; p = 0.09; p = 0.05 among propensity-matched pairs). Operative variables associated with stroke included direct aortic cannulation, aortic arteriosclerosis, descending aorta repair, and mitral valve replacement. The risk of hospital mortality was higher (11%; 42/375) for patients who had femoral cannulation than axillary plus graft (7.0%; 21/299; p = 0.06; p = 0.02 among propensity-matched pairs).

CONCLUSIONS

Axillary inflow plus graft reduces stroke and is our method of choice for complex cardiac and cardioaortic operations that necessitate circulatory arrest. Retrograde or antegrade perfusion is used selectively.

Transcutaneous Axillary Artery Cannulation

The axillary artery may be an alternative cannulation site for patients with diffused atherosclerosis, aortic dissection, and aneurysm. There are different techniques for axillary artery cannulation that can be performed easily with a transcutaneous approach. Small incision necessity, less dissection, and good wound healing are other advantages of this technique.

Use of Saphenous Vein Graft in Axillary Artery Cannulation

Axillary artery cannulation for cardiopulmonary bypass is becoming increasingly used for surgery of aortic dissections for reoperations and extensively diseased ascending aortas. This can be achieved either directly or with a graft. We describe a case with a repair of chronic type A dissection in which axillary cannulation was achieved by placing the arterial cannula into a saphenous vein graft that had been anastomosed end-to-side to the axillary artery. This provides a natural, inexpensive, readily available, and more hemostatic alternative to the use of prosthetic grafts.

Axillary artery cannulation for cardiopulmonary bypass reduces cerebral microemboli

BACKGROUND

Aortic cannulation for cardiopulmonary bypass (CPB) is linked to cerebral microemboli emanating from the ascending aorta. Aortic calcification or disease requiring replacement precludes aortic cannulation. Clinical experience with axillary artery cannulation led to the hypothesis that axillary cannulation may be cerebroprotective.

METHODS

Five mongrel dogs underwent a median sternotomy and isolation of the right axillary artery. The canine bicarotid brachiocephalic trunk was reconfigured by grafting the origin of the left carotid to the proximal left subclavian artery. Microspheres were injected into the ascending aorta during 4 conditions: before and after reconfiguration, CPB with aortic cannulation, and CPB with axillary cannulation. Brain, kidneys, and skeletal muscle were analyzed for microsphere distribution.

RESULTS

Each animal served as its own control for comparison of aortic and axillary cannulation. No significant differences were documented in microsphere deposition for prereconfiguration and postreconfiguration. In the right middle cerebral artery distribution, 2300 +/- 710 microspheres per gram were deposited during aortic cannulation, compared with 540 +/- 110 during axillary cannulation (P <.05). In the left middle cerebral artery region, 2030 +/- 330 microspheres per gram with aortic cannulation were reduced to 1320 +/- 240 with axillary cannulation (P <.05). Axillary cannulation resulted in 73% fewer microspheres in the right brain and 40% fewer microspheres in the left compared with aortic cannulation (P <.05).

CONCLUSIONS

Axillary artery cannulation for CPB is cerebroprotective. Altered blood-flow patterns during axillary cannulation may produce retrograde brachiocephalic artery blood flow and competing intracerebral right-to-left collateral blood flow, deflecting emboli from the ascending aorta and arch toward the descending aorta. Expanded use of axillary artery cannulation during cardiac operations could decrease the incidence of stroke.

Cannulation of the axillary artery with a side graft reduces morbidity

BACKGROUND

The axillary artery is our preferred arterial cannulation site when the ascending aorta cannot be cannulated. Previously, we cannulated the artery directly; now we use a side graft. The purposes of this study were to (1) investigate cannulation-related morbidity and (2) determine whether use of a side graft reduces it.

METHODS

From January 1993 to January 2001, 392 patients underwent 399 axillary artery cannulations. Indications included calcified ascending aorta (129, 32%), ascending aortic aneurysm (115, 29%), type I aortic dissection (85, 21%), cardiac reoperation (70, 18%), and calcified femoral artery (26, 6%). The axillary artery was cannulated directly in 212 (53%) and with a side graft in 187 (47%). Comparisons of cannulation-related morbidity between the direct cannulation and side graft groups were made overall and after both adjusting and matching for propensity score.

RESULTS

Cannulation-related morbidity was infrequent, with brachial plexus injury in 7 (1.8%), axillary artery damage in 7 (1.8%), aortic dissection in 3 (0.8%), and arm ischemia in 3 (0.8%). Only 4 of 187 (2.1%) occurred in the side graft group, versus 16 of 212 (7.0%) with direct cannulation (p = 0.03). After propensity adjustment, the odds ratio for reduction of risk of cannulation-related morbidity with use of a side graft was 0.15 (p = 0.002).

CONCLUSIONS

Use of the axillary artery as inflow for cardiopulmonary bypass is associated with low morbidity. However, cannulation with a side graft was associated with less cannulation-related morbidity than direct cannulation. Routine use of a side graft is recommended whenever axillary artery cannulation is indicated.

Cerebral physiology and outcome after hypothermic circulatory arrest followed by selective cerebral perfusion

BACKGROUND

This study explored the impact of an interval of hypothermic circulatory arrest (HCA) preceding selective cerebral perfusion (SCP) on cerebral physiology and outcome. This protocol allows use of SCP during aortic surgery without the threat of embolization inherent in balloon catheterization of often severely atherosclerotic cerebral vessels.

METHODS

In this blinded study, 30 pigs (20 to 22 kg) were randomized after cooling to 20 degrees C. Pigs in the HCA-CPB group (n = 10) underwent 30 minutes of HCA followed by 60 minutes of total body perfusion (CPB); HCA-SCP pigs (n = 10) underwent 30 minutes of HCA followed by 60 minutes of SCP, and SCP pigs (n = 10) had 90 minutes of SCP without prior HCA. Fluorescent microspheres enabled calculation of cerebral blood flow during perfusion and recovery. Hemodynamics, intracranial pressure, cerebrovascular resistance, and cerebral oxygen consumption were also monitored. Daily behavioral scores were obtained for 7 days postoperatively.

RESULTS

In all groups, cerebral oxygen consumption fell significantly with cooling (p < 0.0001), remained low during perfusion, and rebounded promptly with rewarming; cerebral oxygen consumption was significantly (p = 0.027) greater during SCP than during HCA-CPB. Cerebral blood flow was significantly higher throughout SCP in the HCA-SCP group (p < 0.0001) than with CPB. Cerebrovascular resistance during SCP and HCA-SCP was significantly lower (p = 0.036) than during CPB. Behavioral scores were significantly better with SCP than with HCA-CPB throughout recovery, but did not differ between SCP and HCA-SCP.

CONCLUSIONS

This study suggests that a short period of HCA preceding SCP provides global cerebral protection comparable to continuous SCP, implying that in clinical practice, a short period of HCA to reduce risk of embolization will not compromise the superior cerebral protection provided by SCP.

Current State of Intraoperative Echocardiography

Intraoperative use of echocardiography is becoming more prevalent and is now considered an essential part of modern cardiac surgery. Echocardiography can be performed intraoperatively using transesophageal, epicardial or epiaortic, and substernal approaches. These techniques have a variety of applications in evaluating myocardial and valvular function, assessing aortic atheroma, and determining adequacy of various kinds of repair and reconstruction. Future applications will most likely involve more compact equipment, the implementation of epicardial and transesophageal real-time three-dimensional echocardiography, and better use of provocative methods of intraoperative testing.

Aortic Source of Brain Embolism

Aortic arch atheroma has more recently been identified as an independent risk factor for ischemic stroke. Initially, this was a result of careful autopsy observations, then followed by a series of in vivo studies in which aortic arch atheroma was identified by transesophageal echocardiography. The association of aortic arch atheroma with ischemic stroke is most likely causal, given that the stroke risk increases with increasing thickness of arch atheroma. There is quite a sharp increase in stroke risk for atheroma of 4 mm or greater compared with lesser thicknesses. The clinical diagnosis is suggested when transient ischemic attack or ischemic stroke has occurred in which no obvious cardiac or arterial source of embolism is found. The presence of aortic arch atheroma is usually detected by transesophageal echocardiography and sometimes by magnetic resonance imaging or computed tomography. There is uncertainty about clinical management, particularly for secondary prevention. Options include the use of antiplatelet agents, anticoagulants, thrombolysis, or surgery. The latter two options have only been described rarely in case reports. Of the less invasive approaches, combination antiplatelet therapy with aspirin and clopidogrel is favored, or the use of warfarin. The Aortic arch Related Cerebral Hazard (ARCH) trial is being conducted to determine which of these is more effective in minimizing a composite outcome cluster of ischemic stroke, intracranial hemorrhage, myocardial infarction, peripheral embolism, or vascular death. Other more general management strategies should include reasonably aggressive risk factor control with blood pressure and lipid-lowering therapies and, if indicated, careful diabetic control.

Cannulation of the axillary artery for cardiopulmonary bypass: safeguards and pitfalls

BACKGROUND

The ascending aorta is the customary site for arterial cannulation for cardiopulmonary bypass. Favorable experience at our institution and elsewhere using axillary artery cannulation in treating type A aortic dissections has caused us to broaden our indications for using this site for arterial cannulation for cardiopulmonary bypass.

METHODS

Medical records, operative notes, and perfusion records were reviewed in all patients in whom the axillary artery was cannulated directly or by a graft for cardiopulmonary bypass from January 1, 2000 through August 30, 2002.

RESULTS

Seventy-five patients underwent axillary artery cannulation during the 32-month interval. Eleven patients had ascending aortic dissections, 20 had extensively diseased ascending aortas, and 44 were individuals undergoing repeat cardiac procedures. The right axillary artery was used in 72 patients and the left in 3. In 16 patients the artery was cannulated directly, and in 59 the arterial cannula was inserted into a prosthetic graft that had been anastomosed to the axillary artery. Axillary artery cannulation was satisfactory in 95% (71 of 75) of the cases in which it was used.

CONCLUSIONS

Cannulation of the axillary artery for cardiopulmonary bypass is a dependable approach for procedures including reoperations, aortic dissections, and extensively diseased ascending aortas.

Axillary artery cannulation for arterial inflow in patients with acute dissection of the ascending aorta

The axillary artery is an alternative site for arterial cannulation that avoids manipulation of the ascending aorta or aortic arch and provides antegrade blood flow during surgery for acute type A aortic dissection. Right axillary artery cannulation has been used in 27 patients for arterial perfusion. There were no complications related to the technique of axillary cannulation. All patients but one awoke neurologically intact from operation and suffered no complications. Hospital mortality occurred in two (7.4%) patients. Axillary cannulation is easy to establish and may safely be used for arterial inflow during surgery for acute type A dissection of the ascending aorta.

Cerebral protection: the surgeon's view

The cardiothoracic team has to be ready with a strategy that corners the preoperative to postoperative period, but the cardiothoracic surgeon has to be prepared to perform the optimal procedure by concentrating on the procedure and avoiding circulatory arrest. If it is not possible to avoid circulatory arrest the surgeon should choose the ideal cerebroprotective technique for each patient, which is not always the same technique, change the method during the procedure if necessary, and remember that cerebral protection is not the same as cerebral metabolic preservation.

In vitro hydrodynamics of the Embol-X cannula

BACKGROUND

Prevention of intraoperative plaque dislodgement in patients with atherosclerotic ascending aorta by development of innovative aortic cannula designs gains growing interest in cardiac surgery. To increase knowledge about the hydrodynamics of the innovative Embol-X cannula, which includes an intra-aortic filter device targeting at atheromatous emboli capture, was the aim of the present study.

METHODS

Pressure gradients and back pressures of the Embol-X cannula were measured at varying flow rates in a mock circulation and compared with two commonly used single-stream cannulae.

RESULTS

At a flow rate of 5.5 l/min, pressure gradients across the Argyle and the RMI cannulae were 48% and 62% and back pressures 25% and 47% lower than the corresponding values across the Embol-X cannula.

CONCLUSIONS

The novel concept of integrating a filter device may provide clinical advantages concerning neurologic outcome. Further in vivo studies seem to be desirable to obtain more information concerning the clinical effects of the Embol-X cannula hydrodynamics.