Aortic Dissection Treatment: Type A Surgery and Type B TEVAR

Aortic dissection treatment depends on its type. Type A dissection, which involves the ascending aorta, needs emergency open surgery to replace the torn aorta. Uncomplicated type B dissection, which spares the ascending aorta, is treated medically by lowering heart rate and blood pressure. Complicated type B dissection needs intervention, usually thoracic endovascular aortic repair (TEVAR): a stent graft placed inside the aorta to cover the entry tear.

Dr. Dinesh Kumar Mittal, Senior Director & HOD Cardiothoracic and Vascular Surgery, Fortis Hospital, Shalimar Bagh, New Delhi, India, walked through each of these paths in detail, from how he gains arterial access when the aorta is torn to the indications that move a type B patient from tablets to a stent graft. This article follows his approach. For classification and outcomes, see the complete guide to acute aortic dissection; for the warning signs and CT checklist that come first, see aortic dissection symptoms and diagnosis.

Aortic dissection treatment by type

Surgery is the only treatment for type A dissection. Endovascular stent grafting is used for complicated type B dissection; it has no established role in type A dissection.

Surgery for type A aortic dissection

Type A aortic dissection is treated by emergency open surgery. The aim of surgery for type A dissection is to remove the entry tear, replace the diseased ascending aorta (and, where needed, the arch) with a synthetic graft, and redirect blood into the true lumen so that the false lumen downstream can thrombose.

Before the chest is opened

Dr. Mittal's routine is to expose the femoral artery and vein first, so that the team can go onto cardiopulmonary bypass (the heart-lung machine) through the groin if needed. He then opens the pericardium and assesses what he finds. Sometimes the aorta has already ruptured.

Arterial access when the aorta is torn

In routine heart surgery, the bypass cannula (the tube that returns oxygenated blood from the heart-lung machine) goes into the ascending aorta. In dissection, that aorta is torn and cannot be cannulated. Dr. Mittal instead cannulates one of three arteries:

• the axillary artery;
• the innominate artery;
• the left carotid artery.

Venous drainage is through a cannula in the right atrium.

Cooling and protecting the brain

Once on bypass, the team empties the heart and cools the patient to 18°C. Deep hypothermia protects the brain, because to repair the ascending aorta and the arch, the surgeon has to open both, and the cerebral circulation may have to be stopped for 40 to 45 minutes. That interval is the source of the risk of neurological injury that accompanies this operation.

During this period the brain is perfused directly. Dr. Mittal described his method in the Live Discussion: he places the arterial cannula in the innominate artery if it is healthy, and otherwise in the axillary artery. That cannula first carries the bypass circulation. When the circulation is stopped, the same cannula delivers antegrade cerebral perfusion (blood pumped directly into the arteries to the brain), with near-infrared spectroscopy (NIRS, a sensor that tracks oxygen levels in the brain) and neuromonitoring running throughout. If he expects to need more than an hour of circulatory arrest, he adds a femoral arterial cannula to perfuse the lower body, including the kidneys and the gut. His operating theatre is equipped for neuromonitoring and full invasive monitoring, with an intra-aortic balloon pump and extracorporeal membrane oxygenation (ECMO) available for support.

Replacing the aorta: the Bentall operation

The core of the repair is a composite graft: a Dacron (woven polyester) tube with an aortic valve built into it. In the Bentall operation, the surgeon removes the diseased aortic root and ascending aorta, sews in the composite graft, and reimplants the two coronary arteries into it as buttons of aortic wall. Where the arch is involved, it is replaced too. Dr. Mittal showed operative photographs of a typical case: an aorta that looked bruised and battered from outside, and inside, the separated inner and outer layers with the tear between them.

Not every patient needs the valve replaced. Where the aortic valve itself is normal, even with moderate regurgitation caused by the dissection, it can sometimes be preserved, as it was in his two most recent cases.

When the dissection reaches the coronary arteries

A particularly dangerous subset of type A dissection extends into a coronary ostium, the opening of a coronary artery from the aorta. Dr. Mittal showed a case in which the flap had progressed into the left main coronary artery. These patients arrive in the emergency department with the signs of a myocardial infarction. The surgeon repairs the dissected coronary ostium, fashions the coronary buttons and attaches them to the composite graft. Sometimes the coronary button cannot be saved, and if the ECG still shows ischaemic changes after coming off bypass, a saphenous vein bypass graft is added to restore flow, as in the case he presented, which needed both a Bentall operation and a vein graft.

When the aorta has already ruptured

If the aorta has ruptured into the pericardium, the patient goes onto femoro-femoral bypass, is cooled to 18°C, and the blood is evacuated before the repair can begin. Dr. Mittal described these cases as scary and challenging, but very rewarding.

How much aorta to replace

In most patients, the surgeon replaces the ascending aorta, with or without the arch. For a young man whose type A dissection extended far down the aorta, Dr. Mittal's team replaced the whole of the diseased aorta: the ascending aorta with a valved graft and reimplanted coronary arteries, the arch with all its branch vessels, and the descending aorta through an elephant trunk extension (a length of graft left extending into the descending aorta from the arch repair). That is not possible for every patient.

He also showed the case of a patient who had undergone aortic valve replacement years earlier and returned with a dissection originating at the old aortic cannulation site, a reminder that dissection can follow previous cardiac surgery.

The principles of aortic surgery

Dr. Mittal summarised the surgical principles that apply to both type A and complicated type B repair:

1. Exclude, treat and remove the intimal tear.
2. Excise as much of the diseased aorta as possible. Diseased aorta left behind tends to come back as a later problem.
3. Replace the diseased segment with a prosthetic graft.
4. Ensure blood flows distally in the true lumen, with less flow into the false lumen.
5. Resect the proximal extent of a descending aortic dissection.
6. Where both the proximal and the distal aorta are aneurysmal, above 6 cm, both need treatment, and the more dilated, more life-threatening segment is treated first.

Medical treatment of type B aortic dissection

Uncomplicated type B dissection is treated medically. The aims are to relieve pain and to prevent extension, rupture and progression of the dissection by controlling the blood pressure.

Dr. Mittal's sequence is an intravenous beta blocker in the emergency department, converted to an oral beta blocker for follow-up. If the blood pressure is still not controlled, sodium nitroprusside, an intravenous vasodilator, is added. Current guidelines set the targets for acute dissection at a systolic blood pressure below 120 mmHg and a heart rate of 60 to 80 beats per minute (2022 ACC/AHA aortic disease guideline; the 2024 ESC guideline sets 60 or below), reached with the beta blocker first, before any vasodilator, so that the vasodilator does not provoke a reflex rise in heart rate.

The survival comparison he presented favoured medical treatment alone by a wide margin over open surgery for this group. The early International Registry of Acute Aortic Dissection data make the same point: in type B dissection, mortality was 10% with medical treatment against 31% with surgery.

When type B aortic dissection needs TEVAR: the indications

Type B dissection becomes complicated, and needs endovascular or surgical intervention, when any of the following is present:

• Malperfusion, with vessels arising from the false lumen and causing limb ischaemia, renal failure or mesenteric ischaemia.
• Ongoing pain despite medical treatment.
• Refractory hypertension.
• Rupture or impending rupture, sometimes signalled by a left-sided pleural effusion.
• Aneurysmal enlargement: Dr. Mittal intervenes on a localised false aneurysm above 6 cm. The 2022 ACC/AHA aortic disease guideline recommends repair of a chronically dissected descending aorta once its diameter reaches 5.5 cm.
• Progressive enlargement of the false lumen on serial imaging.
• Retrograde extension into the ascending aorta, which carries the same prognosis as type A and is managed as such.

The aim of TEVAR is to cover the entry tear with a stent graft so that blood is redirected into the true lumen and the false lumen thromboses. That relieves the pain and the organ ischaemia caused by the compressed true lumen. Dr. Mittal showed a stent graft in the descending aorta and the CT afterwards; the procedure looks simple on imaging, he noted, but it is not.

For ruptured type B dissection, he regards hybrid repair, combining open surgery with endovascular stenting, as one of the best options, and a technique teams in developing programmes can learn.

The false-lumen thrombus: a goal, not a danger

A doctor in the session asked whether a thrombus deliberately created in the false lumen could break off and cause a pulmonary embolism. Dr. Mittal's answer: no. For the aortic surgeon, false-lumen thrombosis is the goal; after a Bentall operation, the hope is that the remaining false lumen thromboses, because that stops the disease from progressing. And because the thrombus sits on the left, arterial side of the circulation, it cannot reach the lungs. Only a clot in the venous system or the right heart can cause a pulmonary embolism. The full exchange is in the Live Discussion.

Follow-up CT after aortic dissection treatment

Dissection is a disease of the whole aorta, and the segments left behind need surveillance. After operating, Dr. Mittal repeats a CT scan every year to follow the false lumen. CT angiography suits this role because it is rapid and shows the false lumen and branch vessels clearly.

Related surgical reading

A type A repair takes several times longer than a routine coronary artery bypass graft; the complete guide to acute aortic dissection explains why the operation is so demanding. Related surgical techniques are covered in the guides to advances in heart valve surgery and peripheral arterial disease and aneurysm repair, and in the cardiac surgery specialty hub.