Aortic endarterectomy: a useful technique to utilize for aortic valve replacements in hostile aorta

Abstract

Calcified aorta poses a significant technical challenge in the performance of surgical aortic valve replacement (AVR). Aortic endarterectomy is a less utilized approach and is suitable in select cases for aortic decalcification during AVR. Here, we report a case of calcified ascending aorta who underwent ascending aortic endarterectomy and AVR with the technical details of the procedure.

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Introduction

Calcified ascending aorta mandates an individualized surgical approach in aortic valve replacement (AVR). Faggiano et al. have reported the incidence of porcelain aorta in patients with aortic stenosis to be 7.5% (18/240) [1]. The definition of porcelain aorta as per the PARTNER trial is that of a calcific aorta with no safe area for clamping or cannulation with or without extension of calcium into arch [2]. Even when not meeting the PARTNER trial definition of porcelain aorta, an extensively calcified ascending aorta would still necessitate significant strategic modifications in the conduct of a relatively straightforward operation like surgical aortic valve replacement (SAVR) warranting individualized cannulation strategies, cross clamping methods, cardioplegia delivery techniques, unconventional aortotomies, and sometimes the surgical procedure per se [2].

Surgical approaches to AVR with calcified aorta include AVR under total circulatory arrest (TCA) without aortic clamping or valved graft replacement of aortic root/ascending aorta/arch with or without coronary re-implantation/coronary artery bypasses. In exceptional cases, placement of a valved conduit graft from the left ventricular apex to descending aorta might be contemplated [3]. With a calcified aorta, the identification of safe clamp space and cannulation site alone does not exempt the surgeon from difficulties such as the management of calcific coronary ostia, feasibility of safely seating a valve onto the calcific annulus, extensive calcification precluding a hemostatic aortotomy closure, or the ever present risk of plaque embolization. These would present formidable technical challenges, even to an experienced operator.

Most surgeons, considering the elderly age group of the afflicted, their comorbidities, and the complexity of the surgery [4], choose to opt for trans-catheter aortic valve replacement (TAVR) in concurrence with the Heart Team decision. TAVR, however, is an expensive alternative to AVR and is inaccessible to a majority of our population. Here, we report a case of calcified proximal ascending aorta and severe aortic stenosis, who underwent ascending aortic endarterectomy and bioprosthetic AVR (Video 1).

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Case report

A 77-year-old lady, a known case of calcific aortic valve disease, was admitted with complaints of two episodes of syncope in the last 30 days. She was diagnosed as having critical aortic stenosis 4 years ago and was advised AVR. She had class II angina at the time of diagnosis but was not willing for any intervention then. There was progression of the disease over the course of 4 years, with the patient developing recent episodes of blackouts and high risk for sudden death which warranted an early intervention.

Echocardiogram (ECHO) revealed severely calcified tricuspid aortic valve with critical stenosis (peak and mean gradients 114 and 79 mm of Hg). Measured aortic annulus size was 1.8 cm with mild aortic incompetence. Her left ventricular ejection fraction was 45% with no regional wall motion abnormality (RWMA) pointing to the criticality of stenosis. Coronary angiogram revealed mild disease in the proximal circumflex artery. Plain computerized tomography (CT) thorax showed calcific aorta with circumferential calcium involving the distal aortic root above the coronary origins (Fig. 1a) and extending beyond sino-tubular junction (STJ) for 4 cm from the annulus (Fig. 1b). A calcium-free zone was noted in the ascending aorta of length 4.5 cm proximal to the origin of arch vessels with island of calcium at the base of the brachiocephalic artery. The option of TAVR was suggested to the patient, as per the Heart Team decision. However, the option was declined by the patient, as it was not economically viable for the family and they opted for SAVR. Informed consent was obtained.

Fig. 1.

a Circumferential calcium in the proximal ascending aorta. b Calcium extension from the annulus (black line) and calcium-free zone (red line) in the ascending aorta

After draping both the groin and right axilla for possible inflow access, a midline sternotomy was performed. The calcium-free zone in the ascending aorta was palpated and confirmed by CT thorax (Fig. 1b), and epi-aortic and trans-esophageal echocardiograms (TEE). Aortic cannulation was accomplished at this area, followed by right atrial (RA) cannulation for venous drainage and pulmonary artery venting. Ante-grade cardioplegia cannula was placed through the calcium-free zone and del Nido solution (1.2 L) was used to arrest the heart after cross clamping.

The calcific area beyond the STJ was opened longitudinally (variation from the transverse/oblique aortotomy) and a heavy Mayo scissors was used to extend the aortotomy proximal to STJ, 1 cm above the valve cusps. Care was taken not to fracture the calcium in the aortic wall. The aortic wall was stiff and non-pliable. The valve was heavily calcified with calcific excrescences onto the aortic wall. Using a periosteal elevator, a plane was developed between the aortic adventitia and the calcium plate at one lip of the incision at the STJ (Fig. 2a). Circumferential separation of the plaque from adventitia was accomplished and the dissection proceeded from STJ just proximal to the coronary ostia. The calcific plaques were not extending into the coronary ostia. The plane was not well formed at the posterior aspect of the aortic wall with extension into the adventitia where minimal fracturing occurred. This area was approached by developing another fresh plane from the STJ. The removal of the calcific plaques rendered a pliable aortic adventitia (Fig. 2b). The aortic valve was excised and thorough annular debridement was done. Valve was sized to 19 Perimount Magna Ease, pledgetted valve stitches were taken, and valve seated and tied. The vertical aortotomy was closed with an autologous pericardial patch augmentation. The rest of the surgery progressed in routine fashion. TEE at the end of the procedure showed good calcium clearance at the ascending aorta with no para-valvar leak and normal flow into coronary ostia.

Fig. 2.

a Technique of aortic endarterectomy showing the development of plane between the plaque and adventitia. b Retrieved calcium plaques

Her post-operative course was uneventful and she was discharged on day 7. A repeat CT at 1-month follow-up revealed satisfactory calcium clearance (Fig. 3a, b).

Fig. 3.

a Calcium clearance in axial cut. b Bioprosthetic valve in position with extent of calcium clearance distally

Discussion

The incidence of cerebrovascular events with TAVR in calcific aorta remains at par with SAVR (stroke rate 5.5% vs. 2.8%, p = 0.08 and combined death/stroke rate (14.4% vs 10.2%, p = 0.12) [5, 6]. The incidence of para-valvar leak appears to be higher in TAVR as demonstrated in the PARTNER trials [7]. Considering the complexity of SAVR in the setting of calcified aorta, TAVR might be the treatment of choice in this subset. In the present case, the patient could not financially afford TAVR, which is very much the case for the majority of patients in India.

Svensson et al. reported a small series of patients with calcific aorta, who had undergone aortic endarterectomy and AVR, based on their experience in using this procedure in thoraco-abdominal aneurysm surgeries. They observed that there are two distinct entities of calcified aorta which may or may not overlap: (a) the calcific aortic media and intima adherent to the adventitia (typically involving the root and proximal ascending aorta); (b) the atherothrombotic disease (involving the distal ascending aorta and arch) [3]. The case presented in this report falls into the first category with the proximal aortic involvement with an adherent media and intima.

The establishment of cardio-pulmonary bypass (CPB) and availability of clamp space are decisive in the surgery on calcific ascending aorta. Calcium-free zone for aortic cannulation, root plegia cannula, and cross clamp in the distal aorta was confirmed by TEE and epi-aortic echocardiograms, CT images, and digital palpation. If the cannulation site was hostile, alternate inflow techniques like right axillary cannulation or right femoral cannulation would have been contemplated with a view to proceed with surgery under TCA without cross clamping. Our routine practice of using a del Nido solution for antegrade cardioplegia provides a prolonged diastolic arrest, thus avoiding the need for multi-dosing through the ostia. Hence, we decided against retrograde plegia delivery.

Kudo et al. described the technique of aortotomy using an oscillating saw to get a clean cut of the edge without calcium fracture [8]. Heavy needle holders are used to separate the calcium plates initially at the edge of the incision without causing plaque disruption. It is recommended to always start the dissection either at the edge of incision or at the level of STJ where the plane of dissection would be easier to develop [3]. It is very important to stay within the plane of dissection (between the adventitia and calcium plate normally) taking great care to avoid button holing of the adventitia. To avoid this complication, it is prudent to stop dissection at areas where the plane becomes less demarcated or more adherent. Such areas can be approached by developing a fresh plane starting at another point. The calcium extension on to the coronary ostia can be dissected in a single plane. But, if there is significant plaque disruption during dissection, it might necessitate coronary artery bypass grafts. In the present case, the calcific plaque stopped short of coronary ostia and the coronaries were not calcified. Finally, the importance of a thorough irrigation at the end of valve excision and endarterectomy can not be emphasized more in preventing stroke and myocardial infarction.

The aortic closure often mandates a patch enlargement to relieve the tension on aortic suture line and ensure hemostasis. Bovine pericardium or autologous pericardium, as described in the present case, may be used, depending on the surgeon’s preference. An important question is of adventitia giving way to future aneurysmal dilatation. The concern is justified as the collagen to elastin ratio in the thoracic aortic wall is quite low when compared with that in carotid artery (0.49 vs 2.55), which puts it at a significantly higher risk for aneurysm formation, unlike carotid endarterectomy. However, after aortic endarterectomy, the residual adventitia undergoes an extensive perivascular fibrosis which in turn stabilizes it from aneurysmal dilatation. This has been reported by Vogt et al. by following up their patients for 44 months after aortic endarterectomy and noted no increase in the endoluminal diameters [9]. No long-term data is available on this to date.

The presence of ulcerated or mobile atheromas (grades IV–V by TEE) in the distal ascending aorta and arch necessitates the extension of endarterectomy under TCA without cross clamping to achieve a satisfactory outcome. After achieving circular endarterectomy until the ductus origin, tacking stiches are placed to fix the intima and media of the arch vessels to ensure luminal patency and avoid dissection [10].

The early neurological events after aortic endarterectomy have been reported to vary between 0 and 15.8% [3, 8–10]. Calcium load was limited mostly to the proximal ascending aorta, the availability of safe clamp space, and the cannulation site in the ascending aorta and relatively well-formed plane between the aortic adventitia and calcium plate—all these factors would have contributed to the excellent neurological outcome with the present case.

To conclude, ascending aortic endarterectomy is a useful technique to learn and practice in select cases of calcific aorta, where there is a distinct calcium plane within a fibrous and thick residual adventitia. It is definitely not to replace TAVR which is the procedure of choice in such patients, but certainly adds to the surgeon’s armamentarium when confronted by hostile aorta and gains particular relevance in the Indian context, where a majority of the patients cannot bear the economic implications of TAVR.

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.

Informed consent

Obtained as per the Institutional ethics committee guidance.

Statement on human and animal rights

No humans or animals were harmed during the conduct of this work.