ECMO in Cath-Lab for Coronary, Structural or Combined Percutaneous Cardiac Interventional High-Risk Procedure

Abstract

This chapter describes the use of ECMO for interventional cardiology procedures. In recent years, the rapid development of these techniques has allowed treatment of extremely complex patients, not subject to traditional cardiac surgery due to the very high operational risk which was, therefore, intended only for palliative medical therapy. These procedures are carried out by a multidisciplinary team composed of an interventional cardiologist, heart surgeon, anaesthetist, and perfusionist who collaborate closely during all phases of the patient’s hospitalisation.

1. Introduction

Veno-arterial extracorporeal membrane oxygenation (V-A ECMO) is a temporary, mechanical, circulatory, and respiratory support system. Its main use is in patients with heart and/or respiratory failure, allowing complete support by ensuring continuous systemic perfusion and oxygenation.

This support system has traditionally been used as “rescue” therapy in patients with cardiogenic shock. However, ECMO implantation in emergency conditions is burdened by relevant mortality and morbidity, due to high vascular complications and reduced coronary reserve of patients with severe aortic stenosis or complex coronary artery disease, especially in the presence of a reduction of the global systolic function. In these cases, prolonged hypotension can lead to a rapid deterioration of hemodynamic conditions with the development of cardio-metabolic shock.

Recently, the use of ECMO as support during percutaneous complex cardiac interventions has been proposed, especially in high-risk patients. Besides the clinical aspects, also some technical issues have to be taken into account, such as complex anatomies with an extensive ischemic area at risk and severe impaired ventricular systolic function.

2. Indications

Interventional cardiology procedures, both for valvular and coronary diseases, have become increasingly complex in recent years. Patients to be treated often have multiple comorbidities that make cardiac surgery impractical because it is of very high risk. The development of new technologies has made it possible to treat patients who, until a few years ago, were destined only for palliative medical therapy. The need to treat these patients considered inoperable, he pushed the haemodynamist to use an “extracorporeal circulation” also in the haemodynamic room, in order to carry out very complex procedures both from a clinical and technical point of view in “safety.” The literature shows how ECMO or in any case an extracorporeal circulation installed in an emergency regime is burdened by very high mortality and morbidity, especially in patients who have a reduced cardiac and respiratory reserve, where prolonged hypotension can rapidly evolve towards cardio-metabolic shock [1, 2, 3, 4]. Veno-arterial extracorporeal membrane oxygenation (ECMO), therefore, initially conceived as a rescue therapy in emergencies and cardiogenic shock has become a “protection” tool for patients and operators [5, 6, 7, 8, 9]. The procedures that can be performed with the aid of extracorporeal assistance are many and can be performed individually or combined with each other, including TAVI [10, 11, 12, 13, 14], mitral valve [15, 16, 17] or percutaneous tricuspid repair, percutaneous coronary intervention [18, 19, 20, 21, 22, 23], and electrophysiology procedures, such as ablations of ventricular tachycardias [24, 25, 26].

2.1 Main indications for the prophylactic use of ECMO

• Reduced left ventricular ejection fraction. It represents the most common indication. Patients with depressed ventricular function and aortic stenosis, whether or not it is associated with coronary heart disease to be submitted to TAVI, they may, during the stages of the procedure, not tolerate the hypotensive phase resulting, for example, from rapid ventricular stimulation during the release of the prosthesis. And as shown by the literature, the installation of ECMO in an emergency is burdened with a high mortality and high complication rate [10, 11, 12, 13].

• Severe aortic valve stenosis associated with coronary artery disease involving the left main, treatable with concomitant TAVI and angioplasty. Angioplasty performed on the left main (performed before valvular treatment) could lead, even in this case, to severe hypotension or potentially fatal arrhythmias in a patient with concomitant severe aortic stenosis, even more so if with depressed systolic function.

• Severe coronary artery disease (usually involving the left main or equivalent) in patients with severe chronic respiratory failure, even with normal left ventricular function. Based on our experience, it was necessary to treat a patient in work-up for inclusion in the lung transplant list for severe and extensive pulmonary fibro¬sis after COVID-19 pneumonia, suffering from a 90% stenosis of the distal left main coronary artery, involving the ostia of the anterior descending artery and circumflex and had an intermediate branch of large calibre and distribution occluded, in a left-dominated coronary circle. Patients like this (not subject to coronary artery bypass surgery both due to the need for mechanical ventilation for cardiac surgery with probable weaning difficulties and increased infectious risk, and due to the risk of damage to grafts in subsequent bipulmonary transplant surgery) are exposed to a very high risk of acute respiratory failure with minimal cardiac defiance during the revascularization procedure. Other left ventricular assistance systems, such as the Impella (axial pump, without the possibility of adding an oxygenator), are, therefore, not sufficient to guarantee that the procedure will be safely carried out, unlike ECMO, which allows the patient to be kept alert, spontaneously breathing with stable hemodynamic.

• Combined valve disorders in patients with severe left ventricular impairment, for example, severe aortic valve stenosis or insufficiency to undergo TAVI and severe mitral insufficiency to undergo Mitraclip (Abbott) in the same session. The use of the ECMO in these cases allows the interventional procedure to be assimilated into real heart surgery.

• Severe coronary artery disease (“high-risk PCI”) in patients who cannot receive other assistance systems, such as Impella (Abiomed, Danvers, MA, USA), due to the presence of a mechanical aortic valve prosthesis.

• In some cases, in addition to the prophylactic action aimed at hemodynamic stability during the procedure, the assistance can also be used to facilitate the technical development of the procedure. In patients, for example, with severe or massive tricuspid regurgitation and severe depression of the right ventricular function, subjected to percutaneous repair of the tricuspid valve with the “edge-to-edge” technique (i.e., Triclip, Abbott), the venous drainage guaranteed by the ECMO allows the reduction of diameters of the right ventricle and the consequent reduction of the coaptation gap between the tricuspid flaps, thus favouring the implantation of the clips. The conduction of assistance in these cases must be very accurate to avoid the return to an initial right ventricular volume, causing a laceration of the tricuspid flaps or the detachment of the positioned clips, therefore continuous transoesophageal control is essential.

3. Pre-procedural phase

A “Heart Team” made up of interventional cardiologists, cardiac surgeons, clinical cardiologists, cardio anesthesiologists and perfusionists discusses the clinical characteristics of all patients. The traditional cardiac surgery option is excluded due to the high operative risk (Euroscore II, STS score, and Syntax score), and the percutaneous option is chosen for the treatment of the diseases in question. But even these procedures are not free from risks, and in certain situations (clinical or technical), it is necessary to carry them out using mechanical assistance to the circulation. Several factors push the Heart Team to perform coronary or percutaneous valve procedures in ECMO assistance, [27] including acute heart failure, hemodynamic instability, reduced ejection fraction, need for support with inotropic drugs, extremely high surgical risk, technical aspects, particularly, for complex myocardial revascularizations with large areas of myocardial risk and risk of haemodynamic destabilisation during the procedure. Hemodynamic instability is defined as the need for inotropic drugs to maintain an average arterial pressure > 65 mmHg, while electrical instability refers to the presence of relapses of ventricular arrhythmias sustained in the last 24 hours.

In addition to routine instrumental and laboratory tests (ECG, chest x-ray, blood chemistry with control of blood counts, renal and hepatic function, and a particular focus on coagulation screening), a transthoracic or transoesophageal echocardiogram is performed if required by the underlying pathology. All patients are then subjected to an aortic CT angiography, which allows to evaluate the course, calibres, presence, and extent of atheromasia/calcifications or other alterations (e.g., aneurysms and thrombotic apposition) along the entire arterial tree and, therefore, allows to choose which is the best site for the assistance installation.

In some patients, especially those who are suffering from valvular pathologies with reduced ejection fraction and/or pulmonary hypertension, the infusion of Levosimendan in the 24–48 hours preceding the procedure may be useful in order to make them arrive at the best possible compensation conditions for the procedure. This may favour the weaning of the patient from extracorporeal circulation and limit or in any case reduce the need for the use of inotropic drugs in the intra- or post-procedural period.

4. Circuit and cannulation techniques

The standard configuration for interventional cardiology procedures is a peripheral veno-arterial extracorporeal membrane oxygenation (V-A ECMO), with cannulation of the femoral artery and vein. They are usually using high-flow arterial cannulas (18-20Fr) and multistage venous cannulas with the distal end positioned in the superior vena cava under fluoroscopic guidance (Figures 1–3).

Figure 1.

Placement of the venous cannula in the superior vena cava.

Figure 2.

Control of venous cannula positioning.

Figure 3.

Venous cannula in superior vena cava.

Cannulation can be performed under echography guidance, with percutaneous technique (with the use of percutaneous devices of haemostasis, such as Proglide (Abbott Park, IL, USA) or Manta (Teleflex, USA)) or with surgical isolation of the femoral vessels, depending on the anatomical characteristics of the patient. Based on the pre-procedural CT analysis, arterial cannulation sites other than the femoral arteries can be chosen, when these are not suitable for use due to insufficient calibres or extreme atheroma (Figures 4–6).

Figure 4.

Angiographic control prior to arterial puncture at the site chosen for cannulation, performed from the contralateral arterial access.

Figure 5.

Surgical femoral accesses for TAVI (A) and ECMO (B).

Figure 6.

Percutaneous femoral accesses for ECMO (A) and coronary angioplasty (B).

The most frequently used alternative site is the axillary artery, which, in most cases, has an adequate calibre to ensure systemic perfusion with the advantage of offering an antegrade flow and is rarely affected by atheromatous or calcific processes.

The standard circuit, consisting of venous and arterial lines connected to a centrifugal pump, oxygenator, and heat exchanger, can be processed according to the needs deriving from the patient’s pathology or technical characteristics of the procedure. For example, it may be necessary to unload the left ventricle (i.e., TAVI procedures in cases of severe aortic regurgitation), which is carried out with the introduction of catheters of adequate calibre in the left ventricle (not less than 6 Fr) inserted with transseptal or transaortic approach or in the pulmonary artery through the femoral or jugular vein and connected on the venous line (Figures 7 and 8).

Figure 7.

The arrow indicates transseptal pigtails for unloading the left ventricle during the TAVI procedure for severe aortic regurgitation.

Figure 8.

The arrow indicates 8Fr catheter for unloading the left ventricle inserted transseptally during a combined procedure of TAVI and Mitraclip in a patient with severe aortic and mitral regurgitation.

The use of a percutaneous left ventricular drainage that limits ventricular distension, in cases of severe aortic regurgitation [28], guarantees greater procedural hemodynamic stability and facilitates the release of the aortic valve prosthesis for the correction of the regurgitation itself (in fact, it allows to obtain the almost total absence of systolicization of the left ventricle, a function similar to rapid ventricular stimulation, limiting the risk of “pop up” of the valve prosthesis). Limiting ventricular distension and the consequent increase in oxygen consumption is a crucial factor in limiting the hemodynamic and arrhythmic instability of a heart in critical conditions and can, therefore, represent strength in the treatment of situations, such as cardiogenic shock or the complications of percutaneous interventions. In fact, the ECMO protects the entire organism from the low cardiac output deriving from a condition of cardiogenic shock, but paradoxically the least protected organ is the heart itself because it undergoes distension of its cavities with an increase in oxygen requirements (Law of Laplace) and, therefore, the risk of ischemia. The possibility of draining the left cavities reduces this problem and makes the manoeuvres to remedy any complications more effectively (i.e., defibrillation in case of serious arrhythmias or repositioning of an aortic prosthesis for massive regurgitation).

In other cases, double venous cannulation, both femoral and jugular, may be necessary, for example for the treatment of tricuspid regurgitation, where the encumbrance of the single multistage cannula in the right atrium (diameter 22–23 Fr) would not allow the passage of catheters (with a diameter of 24Fr in the case of the Triclip) and the manoeuvres of percutaneous tricuspid repair. In these cases, a cannula is placed in the inferior vena cava with the upper end at the level of the hepatic veins and a second cannula in the right internal jugular vein (14–17Fr) is added, with the end at the level of the superior atrio-caval junction for ensuring adequate venous drainage (Figures 9–11).

Figure 9.

Cannula positioned in the right internal jugular vein and connected to the venous line.

Figure 10.

Cannula in superior vena cava (A) and inferior vena cava with the tip at the level of the hepatic veins (B).

Figure 11.

Percutaneous repair procedure of the tricuspid valve with the Triclip system—the arrow indicates the final position of the venous cannula at the level of the hepatic veins to allow manoeuvres for the delivery of the Triclip in the right atrium.

In addition, leads can be created on the arterial line to allow procedures to be performed with a single arterial access (especially PCI or in TAVI procedures for the passage of the reference pigtail for valve implantation), obviously, in these cases, it must be carried out a careful evaluation of the resistance to flow deriving from the encumbrance provided by the catheter inside the arterial line, so that sufficient systemic perfusion is guaranteed without increasing the risk of haemolysis, which would nullify the advantage of “saving” arterial access to the patient.

5. Procedural phase—conduct of assistance

Most patients do not require intubation and mechanical ventilation, so the procedures can be performed with the patient in spontaneous breathing, mildly sedated, especially for analgesic purposes, by practising local anaesthesia at the site of the vascular accesses. In some cases, the interventional procedure to be performed requires continuous transoesophageal monitoring (i.e., Mitraclip), in these cases, it is preferable to practice general anaesthesia and mechanically ventilate the patient. In the case of intubation, lung-protective ventilation is performed during extracorporeal assistance and the gas supplied to the oxygenator is adjusted to achieve an arterial oxygen partial pressure of approximately 150 mmHg and normocapnia.

In all cases, the blood pressure is monitored and a central venous catheter is positioned for the measurement of the central venous pressure and the possible rapid administration of liquids or drugs. In addition, a bladder catheter is placed for monitoring diuresis.

Vascular access is performed under ultrasound guidance for the positioning of the small calibre introducers (usually 7-8Fr) necessary for both the positioning of the cannula for ECMO and for the execution of the interventional procedure. Once inserted, systemic heparinization is carried out, administering a quantity of heparin necessary to achieve an ACT (activating clotting time) of 250 sec (about 200 IU/kg). Once this value has been reached, the arterial and venous cannulas are positioned and extracorporeal circulation is started, usually in normothermia.

In most cases, total replacement of the pump and respiratory function is not required, but assistance is provided to the circulation, maintaining a flow equal to approximately 70% of the total theoretical flow, and calculated on the basis of the patient’s body surface. During the various phases of the procedure, the flow will be modified according to the specific needs of the procedure itself, for example, it is reduced to a minimum during the release of the aortic prostheses in order to avoid a “pop down” of the prosthesis itself inside the left ventricle conversely, during manoeuvres, such as coronary rotational atherectomy, the flow is increased in order to support the circulation and facilitate the washing of intracoronary debris. As happens in cardiac surgery operating rooms, close and continuous collaboration between the operators and the perfusionist is, therefore, essential.

Every 30 minutes of extracorporeal assistance, a blood gas examination and ACT check are performed to monitor the patient’s respiratory exchanges and metabolic balance.

At the end of the procedure, the pump flow is gradually weaned. If necessary, inotropic drugs can be used to promote hemodynamic stability. This operation can take from a few tens of minutes to a few hours, depending on the patient’s needs. In case of impossibility of weaning (which has never happened in our experience), the ECMO can be kept at adequate flow, transferring the patient to the intensive care unit where slow weaning will be attempted in the following days.

Upon obtaining stable and valid hemodynamic at the complete weaning of care, the cannula can be removed and the protamine sulphate is administered.

In cases of surgical isolation, decannulation will be directed with surgical repair of the vessels (usually with the closure of previously packaged purse-string suture). In cases of percutaneous implantation, arterial decannulation is performed, when possible, by placing and inflating at low atmospheres, a haemostasis balloon of adequate calibre (usually at least 2 mm greater than the diameter of the external iliac artery) upstream from the cannulation site, by crossover of the femoral arteries or through a guide inserted in the radial artery and pushed up to the affected femoral, which allows the removal of the cannula itself and the closure of the femoral breach with the means of percutaneous haemostasis (Proglide or Manta) by limiting blood losses as much as possible (Figures 12–15). As for percutaneous venous decannulation, an external suture can be applied or a Proglide can be used.

Figure 12.

Femoral artery crossover.

Figure 13.

Haemostasis balloon placed in the right iliac artery for removal of the arterial introducer at the end of a TAVI procedure.

Figure 14.

Outcome of ECMO percutaneous femoral access (A) and coronary angioplasty (B).

Figure 15.

TAVI (A) and ECMO (B) percutaneous femoral access outcome.

Once haemostasis is achieved, compression dressings are applied to the access sites and the patient is transferred to the intensive care unit for monitoring for the first 24 hours.

6. Conclusion

Our experience in the prophylactic use of ECMO in Cath-lab for the treatment of extremely complex patients has shown good results in both the short- and medium-term. The success of this therapeutic strategy was confirmed by the medium-term results, considering that most of these patients, due to their age and basic clinical conditions, would have been destined for palliative medical therapy and a certain poor short-term prognosis [21, 22, 23, 24, 25, 26, 27, 28, 29].

V-A ECMO was mainly used in the “bail-out” to address conditions of severe respiratory distress or refractory cardiogenic shock. Recently, however, its prophylactic use in the interventional cardiology laboratory has been considered, especially in complex and high-risk coronary procedures, showing good results and to a lesser extent for structural interventional procedures (TAVI) with good results in terms of procedural “security.”

Although there are no standardised criteria for defining a “high-risk” procedure, there is general consensus due to a variable combination of clinical and anatomical factors. Among the first are the presence of a compromised functional class (NYHA III/IV), ventricular dysfunction, pulmonary hypertension, haemodynamic or electrical instability, heart failure despite optimised therapy, and the presence of comorbidities. Among the latter include the extent and anatomy of coronary lesions, the extent of the ischemic area at risk during the procedure, the need to use “aggressive” devices (i.e. rotational atherectomy) and anatomical features of the valves. Furthermore, the clinical criticality of the patient may be due to the coexistence of coronary and valvular or plurivalvular disease requiring combined treatment causing an inexorable increase in procedural risk.

The presence of a multidisciplinary team expert in the treatment of complex diseases, which collaborates in the management of the entire length of hospitalisation of these patients is, therefore, fundamental. Starting from the correct choice of the procedure for each individual patient, to the planning of each step of the procedure itself and the intra- and post-procedural management with the active and productive comparison of each specialist.

Further studies are obviously needed to confirm the good results of the currently limited experiences, but we are confident that the use of ECMO to carry out this type of procedure represents an important therapeutic option in the near future.

Acknowledgments

Thanks to the entire medical and nursing team of Maria Pia Hospital in Turin, which allowed us to perform these complex and innovative procedures. A special thanks to Dr. Elvis Brscic and Dr. Katiuscia Testa who with so much passion, courage, a pinch of madness, and above all a lot of hard work have allowed the realisation of the “ECMO in Cath-lab” project.

Conflict of interest

The author declares no conflict of interest.