Early and midterm hemodynamics after aortic valve bypass (apicoaortic conduit) surgery

Apico-aortic conduit: a readily available technical modification

When neither surgical valve replacement nor transcatheter aortic valve implantation is possible, performing an apico-aortic conduit remains a therapeutic option. This procedure has become rare and the rigid angled apical connectors usually used to facilitate ventricular anastomosis are no longer commercially available. We described the technique that we performed on a 60-year-old patient with readily available material.

An Early Canadian Experience With the Correx Automated Coring and Apical Connector Device for Aortic Valve Bypass

OBJECTIVE

Aortic valve replacement is the standard of care for severe, symptomatic aortic valve stenosis (AS); however, anatomy or pre-existing comorbidities may preclude conventional or alternative transcatheter approaches. Aortic valve bypass (AVB) may be performed as a salvage procedure for the relief of symptomatic aortic stenosis in patients who are not suitable candidates for aortic valve replacement.

METHODS

At our institution, seven patients underwent AVB using the Correx automated coring and apical connector system. All patients had severe AS with New York Heart Association functional class 3 symptoms and were not candidates for conventional or transcatheter approaches. Via a left anterolateral thoracotomy to access the descending aorta and left ventricular apex, we used the Correx system (Correx, Waltham, MA USA) to anastomose a valve conduit to the left ventricular apex proximally and the descending aorta distally. Three patients required cardiopulmonary bypass.

RESULTS

In all seven patients, the automated coring and apical connector was successfully deployed. There were two in-hospital deaths in this series. Immediately postoperatively and at 3 months, there was a significant reduction in mean and peak valve gradients, and all surviving patients performed at New York Heart Association functional class 1.

CONCLUSIONS

Aortic valve bypass seems to be an acceptable alternative for the treatment of severe AS in high-risk patients who are not candidates for aortic valve replacement. The Correx automated system may improve the clinical applicability and surgical reproducibility of AVB in appropriately selected patients in which conventional or transcatheter aortic valve replacement is not a feasible options.

Transcatheter Treatment of Apicoaortic Conduit Dysfunction

We report a 77-year-old male patient with a history of aortic valve bypass with an apicoaortic conduit 11 years ago for severe aortic stenosis, presenting with acute decompensated congestive heart failure. Severe conduit valve regurgitation and was successfully treated with transcatheter aortic valve replacement (TAVR) of the native aortic valve using a self-expanding bioprosthesis followed by transcatheter closure of the apicoaortic conduit.

Hemodynamic changes following aortic valve bypass: a mathematical approach

Aortic valve bypass (AVB) has been shown to be a viable solution for patients with severe aortic stenosis (AS). Under this circumstance, the left ventricle (LV) has a double outlet. The objective was to develop a mathematical model capable of evaluating the hemodynamic performance following the AVB surgery. A mathematical model that captures the interaction between LV, AS, arterial system, and AVB was developed. This model uses a limited number of parameters that all can be non-invasively measured using patient data. The model was validated using in vivo data from the literature. The model was used to determine the effect of different AVB and AS configurations on flow proportion and pressure of the aortic valve and the AVB. Results showed that the AVB leads to a significant reduction in transvalvular pressure gradient. The percentage of flow through the AVB can range from 55.47% to 69.43% following AVB with a severe AS. LV stroke work was also significantly reduced following the AVB surgery and reached a value of around 1.2 J for several AS severities. Findings of this study suggest: 1) the AVB leads to a significant reduction in transvalvular pressure gradients; 2) flow distribution between the AS and the AVB is significantly affected by the conduit valve size; 3) the AVB leads to a significant reduction in LV stroke work; and 4) hemodynamic performance variations can be estimated using the model.

Postsurgical hemodynamics of the aortic valve bypass operation evaluated with phase contrast magnetic resonance

PURPOSE

To characterize the postsurgical hemodynamics in aortic valve bypass (AVB) patients, and to determine the relationship between presurgical native aortic valve pressure gradient and postsurgical hemodynamics.

MATERIALS AND METHODS

Twenty patients scheduled for AVB surgery underwent presurgical transthoracic Doppler echocardiography to assess the degree of aortic stenosis and postsurgical cardiac magnetic resonance imaging (MRI) to acquire phase contrast magnetic resonance (PCMR) flow values along the ascending and descending aorta, and in the conduit. Net flow values were calculated from the PCMR images and compared to presurgical aortic valve pressure gradient measurements.

RESULTS

PCMR showed that: 1) The blood flow split between the aorta and the conduit was 35%:65% of cardiac output and 2) 60% of patients had net retrograde blood flow in the superior thoracic aorta over the cardiac cycle. Patients with presurgical pressure gradient (ΔP) > 45 mmHg had significantly less blood flow out of the native aorta than patients with ΔP < 45 mmHg, and had significantly more retrograde flow in the superior thoracic aorta postsurgery.

CONCLUSION

In patients undergoing AVB, presurgical aortic valve pressure gradient is associated with the volume of blood flow out the aorta and the direction of blood flow in the superior thoracic aorta after conduit addition as measured by PCMR.

Apicoaortic conduit and cerebral perfusion in mixed aortic valve disease: a computational analysis

OBJECTIVES

The revival of the apicoaortic conduit has attracted new interest in this alternative treatment for severe aortic stenosis unsuitable for conventional valve replacement. However, doubts still exist about the perfusion of the epiaortic vessels after apicoaortic conduit implantation, especially when severe aortic stenosis is associated with aortic valve insufficiency. The aim of the study was to evaluate the perfusion of the epiaortic vessels (innominate artery, left carotid artery and left subclavian artery) in cases of mixed aortic valve disease before and after apicoaortic conduit implantation.

METHODS

Starting from the data of a real patient with severe aortic stenosis and mild aortic insufficiency who underwent apicoaortic conduit implantation, we created a computational model where severe aortic valve stenosis was associated with different grades of aortic insufficiency (mild, medium and moderate).

RESULTS

A total of six combinations were analysed. In all simulations, the more severe the concomitant aortic insufficiency, the more the flow through the epiaortic vessels was diminished. After apicoaortic conduit implantation, there was an absolute augmentation of the median output in each epiaortic vessel compared with the same combination of mixed aortic valve disease before implantation. Interestingly, retrograde flow from the conduit in the descending aorta was minimal and did not contribute to the improved output of the epiaortic vessels.

CONCLUSIONS

The computational analysis suggested a protective effect, rather than steal phenomenon, of the apicoaortic conduit towards the cerebral perfusion, even in cases of mixed aortic valve disease.

Aortic valve bypass: experience from Denmark

OBJECTIVES

In aortic valve bypass (AVB) a valve-containing conduit is connecting the apex of the left ventricle to the descending aorta. Candidates are patients with symptomatic aortic valve stenosis rejected for conventional aortic valve replacement (AVR) or transcatheter aortic valve implantation (TAVI). During the last one and a half year, 10 patients otherwise left for medical therapy have been offered this procedure. We present the Danish experiences with the AVB procedure with a focus on patient selection, operative procedure and short-term results.

METHODS

AVB is performed through a left thoracotomy. A 19-mm Freestyle(®) valve (Medtronic) is anastomosed to a vascular graft and an apex conduit. The anastomosis to the descending aorta is made prior to connecting the conduit to the apex. In 1 patient, we used an automated coring and apical connector insertion device (Correx(®)). The device results in a simultaneous coring and insertion of an 18-mm left ventricle connector in the apical myocardium. AVB is routinely performed without circulatory assistance.

RESULTS

Ten patients have been operated on since April 2011: eight females and 2 males with a median age of 76 (65-91) years. Seven patients had a severely calcified ascending aorta. Three of these had previously had a sternotomy, but did not have an AVR because of porcelain aorta. Six patients had a very small left ventricle outflow tract (<18 mm). The median additive EuroSCORE was 12 (10-15). Seven patients were operated on without circulatory assistance. Two patients had a re-exploration for bleeding and 1 developed a ventricle septum defect 1 month postoperatively and was treated with surgical closure. The median follow-up was 7 (2-15) months and was without mortality. New York Heart Association class was reduced from 2.5 to 2 at the follow-up, but some patients were still in the recovery period. The total valve area (native plus conduit) was 2.2 (1.9-2.5) cm(2) and 1.34 (1.03-1.46) cm(2)/m(2), indexed to the body surface area. There was no AV block or stroke.

CONCLUSIONS

AVB can be performed with low mortality and acceptable results in selected patients. The procedure can be offered to patients rejected for conventional aortic valve replacement and TAVI and results in a larger total valve area than by insertion of standard bioprosthesis.

The off-pump implantation of an apicoaortic valved graft is safe and has no negative impact on coronary flow and hemodynamics

OBJECTIVE

: To determine the hemodynamic effect of an off-pump apicoaortic valved graft (AAVG) implantation, we performed a quantitative coronary flow analysis in a swine model of severe aortic stenosis.

METHODS

: In 10 swine, cardiac output, coronary flow, right common carotid artery flow, and internal mammary artery flow were measured along with left and right ventricular pressures and aortic and pulmonary artery pressures. A novel AAVG was implanted off-pump on the left ventricular (LV) apex using a specially designed implantation tool and anastomosed to the descending thoracic aorta. Aortic flow was measured proximally and distally of the AAVG-to-descending thoracic aorta anastomosis. After AAVG implantation, epicardial echo confirmed occlusion of the LV outflow tract by a valvuloplasty balloon. Baseline simultaneous measurements of all parameters were repeated after AAVG implantation and intravenous Dobutamine administration.

RESULTS

: The AAVG was implanted without any blood loss. After AAVG implantation and LV outflow tract occlusion, the aortic flow proximal to the AAVG-to-descending thoracic aorta anastomosis changed from antegrade (1508 ± 435 mL/min) to retrograde (-529 ± 241 mL/min, P < 0.001). All other measured parameters remained unchanged compared with baseline. After intravenous Dobutamine administration, LV pressure increased from 88 ± 20 to 184 ± 36 mm Hg (+209%, P < 0.0001) and coronary flow increased from 75 ± 34 to 193 ± 90 mL/min (+257%, P = 0.001).

CONCLUSIONS

: The off-pump implantation of an AAVG is bloodless, safe, reproducible and has no negative impact on coronary flow and hemodynamics. In addition, to the best of our knowledge, this is the first study where blood flow in all coronary arteries was measured simultaneously during an AAVG implantation.

Management of aortic valve bypass surgery

The 3 leading causes of aortic stenosis (AS) in adults are calcific degeneration of a normal trileaflet aortic valve (AV), calcific degeneration of a congenital bicuspid AV, and rheumatic AS. Therapeutic options in patients with severe AS include aortic valve replacement (AVR), transcatheter aortic valve implantation (TAVI), or aortic valve bypass (AVB). An AVB involves the placement of a valved conduit between the apex of the left ventricle and the descending thoracic aorta. AVB serves as a useful alternative to treat severe AS in patients deemed high risk for conventional AVR (ie, porcelain aorta, previous cardiac surgery) or TAVI (ie, severe aorto-iliac disease, limited experience, lack of hybrid operating room). Advantages of on-pump AVB include the avoidance of aortic cannulation, cross-clamping, and cardioplegic cardiac arrest. The procedure can also be performed without cardiopulmonary bypass. In this article, the authors review the circulatory physiology, perioperative anesthetic management, the role of intraoperative transesophageal echocardiography, and surgical considerations of AVB surgery through 3 cases.

Automated coring and apical connector insertion device for aortic valve bypass surgery

PURPOSE

The technical difficulty of performing the left ventricular apical anastomosis has limited the adoption of aortic valve bypass surgery for the treatment of aortic stenosis. We report the successful use of an automated coring and apical connector device to perform aortic valve bypass surgery.

DESCRIPTION

A 74-year-old man, with a history of prior coronary bypass surgery with patent grafts and a porcelain ascending aorta, presented with symptomatic critical aortic stenosis. Through a left anterolateral thoracotomy, a valved conduit was anastomosed to the descending thoracic aorta. The automated coring and apical connector insertion device was used to core a plug of apical myocardium and simultaneously insert an 18-mm apical connector into the left ventricular apex.

EVALUATION

There were no procedural complications, cardiopulmonary bypass was not used, and estimated blood loss was minimal. The patient was discharged on postoperative day 5, and at 3-month follow-up demonstrated significant clinical and hemodynamic improvement.

CONCLUSIONS

The automated coring and apical connector insertion device facilitated the safe and effective performance of aortic valve bypass surgery.

Magnetic resonance investigation of blood flow after aortic valve bypass (apicoaortic conduit)

BACKGROUND

Aortic valve bypass (AVB, apicoaortic conduit) is an alternative to aortic valve replacement (AVR) for high-risk patients with aortic stenosis (AS). The redistribution of blood flow after AVB has been poorly characterized. In order to understand cardiovascular physiology after AVB, we performed cardiac magnetic resonance (CMR) imaging of AVB recipients.

METHODS

Fifteen patients with symptomatic AS underwent beating-heart AVB. Electrocardiography-gated two-dimensional phase-contrast velocity mapping CMR imaging was conducted on each patient. Instantaneous flow was acquired at discrete intervals within the cardiac cycle and ventricular function and volumes were evaluated. Five age-matched patients without aortic valve disease served as controls.

RESULTS

Conduit flow (as a percent of total cardiac output) was 65% ± 5%. Ejection fraction was unchanged compared with before AVB (50% ± 17% versus 57% ± 13%; p = 0.91). Ventricular volumes and cardiac indices were within normal limits and similar to those values in controls (cardiac index 2.9 ± 1.0 versus 2.3 L/min/m(2); p = 0.26; end-diastolic volume index 59 ± 17 mL versus 55 ± 20 mL; p = 0.66; end-systolic volume index, 25 ± 12 versus 25 ± 18 mL; p = 0.91; stroke volume index, 33 ± 11 versus 30 ± 6 mL; p = 0.57 for AVB and control patients, respectively). There was a small degree of retrograde blood flow in the descending aorta above the level of the conduit insertion (10% ± 8% of cardiac output).

CONCLUSIONS

Aortic valve bypass results in a predictable blood flow distribution between the native aorta and conduit and is associated with normal ventricular volumes and function.