A bolt out of the blue: acute aortic dissection

This is one of the biggest emergencies in heart surgery, or, dare I say, of medicine in general. From a subjective wellbeing, a sudden sharp and excruciating pain in the chest makes the person reach out for medical help. As soon as the patient arrives to the ER, a diagnostic protocol for acute chest pain is carried out. Once acute myocardial infarction is ruled out, the patient must undergo a CT scan to either exclude or confirm acute aortic dissection.

As soon as the diagnosis of acute aortic dissection is confirmed, the heart surgeons are called upon and if the dissection involves the ascending aorta (the segment of the aorta close to the heart), the patient is immediately transferred to the operating theatre to undergo lifesaving heart surgery.

In short: from feeling well, with no warning whatsoever, the patient and his relatives are completely taken aback and are not prepared to handle the “weird” diagnosis and most of all this complex heart surgery in absolute emergency that could well cost the patient’s life.

The impact is that of a terrible car accident or a natural disaster and it is very difficult to handle, both by the patient and his family.

Aortic dissection is an incomplete rupture. Meaning that the blood (through blood pressure) flows within the internal wall of the aorta,  but cannot push through each one of the aortic layers, hence the incomplete rupture. The blood digs an unusual way along and within the aortic wall, tearing it violently. The combination of rupture and violent tearing of the walls cause the characteristic sharp pain. The immediate life danger is given by the risk of a complete rupture of the aortic wall and the consequent bleeding that can be fatal if located in the initial part of the aorta, which is included in the sac that encloses the heart. In this case, the heart gets compressed and the blood blocked.The blood piles up in the pericardial bag and the heart stops beating. Furthermore, important blood vessels emerging from the aorta can also be blocked by the blood flown into the false canal. This can cause a wide array of problems linked to the lack of perfusion (oxygen and blood) of vital organs such as brain, liver, intestine, kidney, limbs.

The aim of this surgery is to save the life of the patient. He/she gets connected to the heart-lung machine and cooled to a central temperature below 25°C (let’s not forget that the usual central temperature is 36°C). This is done to decrease the body’s metabolism, especially that of the brain, in order to protect it.

The part of the damaged aorta is replaced by a synthetic tube. The extension of the replacement is estimated during surgery but to be able to check the inside of the aorta at its arch and to suture the synthetic tube to the remaining part of the aorta, it is necessary to stop the blood circulation altogether. This can last between 15 and 90 minutes (depending on what needs to be done) and during this time the brain is supplied with cold blood through catheters inserted in the carotid arteries. Obviously, a longer-lasting cardiocirculatory arrest despite the protective hypothermia could compromise the functionality of various organs and systems and also the non-physiological blood supply of the brain during surgery could not be sufficient for it to come out undamaged. The main problem of the surgery is given by the aortic wall’s extreme fragility, which makes it very difficult for the sutures to hold properly.

I believe it is now  more clear, that this is a high risk surgery, both because of complications that can incur and mortality.

Not every patient suffering an acute aortic dissection needs immediate surgery. Acute dissection of the segments of the aorta more far away from the heart (i.e. the descending thoracic aorta) can be treated with blood pressure lowering drugs and sometimes by inserting special prostheses into the vessel (called “endopirostheses”) to stabilise its wall. Also this type of dissection can cause lack of perfusion of organs and / or extremities, in this case surgery or the insertion of an endoprosthesis is mandatory and highly urgent.

Why does this terrible illness occur?

We do not really know. What we do know is that the tissue of the aortic wall is weakened and at some point it gives way under the force of blood pressure. The weakening of the aortic wall could be caused by a pre-existing aortic dilatation  (sometimes not known), or, more seldomly, because of a genetic illness, such as Marfan syndrome. Many times, however, there is nothing of the above, “just” high blood pressure and a sudden giving in of the tissue, similar to a tyre burst due to wear and tear.

The aim of medical research is to get a better understanding of this illness and the factors that trigger the onset. A full-scale research is currently undergoing by analysing the tissue taken in the OR, individual factors and the population of reference, analysis of the aorta’s morphologic characteristics and genetic analysis.

The 19th of September has been set as the Aortic Dissection Awareness Day to raise awareness among doctors and patients: congresses have been organised all over the world and Lugano is not an exception (please click here to see the programme).

It is important to prevent. It is important to single out high-risk individuals and offer them aortic replacement before it ruptures. We are intensively working towards this goal and will talk about this again in this blog.