and Left Main Procedures
Patients with unstable angina and ischaemic cardiomyopathy with poor left ven- tricular function represent a subgroup at high risk for either percutaneous or surgical revascularisation. In this context, a transient coronary occlusion during angioplasty can precipitate profound instability, irreversible arrhythmia, or fatal loss of cardiac output.
ECMO-assisted PCI was initially introduced more than 20 years ago to provide haemodynamic backup in the event of acute coronary occlusion post angioplasty. In 1988, Vogel reported the fi rst experience from the University of Maryland with sup- ported PCI and valvuloplasty in high-risk patients (nine and six, respectively) [ 7 ];
patients were defi ned as high risk if they presented with severe left ventricular impairment or large amounts of myocardium perfused by the index vessel. In this early experience, all patients were weaned off bypass within 90 min (pump fl ow between 3 and 5 L/min) and the initial outcome was encouraging, with only one reported death in each group (acute mesenteric ischaemia 8 h after PCI and sudden ventricular fi brillation 12 h after valvuloplasty).
The following year, Taub et al. reported their experience with patients for whom ECMO-supported PCI was necessary because of low left ventricular ejection frac- tion (mean LVEF 31.5 %, n = 7) [ 8 ]. The mechanical support permitted safe, longer balloon infl ation time, yielding satisfactory angiographic results. However, this was at the expense of high complication rates in other areas, such as groin haematoma (requiring transfusion), deep vein thrombosis, and iliac artery occlusion, as well as a death from retroperitoneal haemorrhage. Similar results were described by the
University of California on patients with unstable angina and ischaemic cardiomy- opathy (mean LVEF 24 %, n = 5) who successfully underwent ECMO-assisted PCI [ 9 ]; the main drawback was again the high rate of access site complications. This is also probably a refl ection of old cannulation technology.
More recently, Magovern reported the Allegheny experience with 27 high-risk patients who were revascularised with PCI under ECMO support [ 10 ]; technical success was achieved in 26 patients (96 %), including 12 requiring left main angio- plasty. Most patients (85 %) survived to discharge, with sudden cardiac arrest and heart failure as the main causes of the death in the remainder.
Left main coronary artery (LMCA) disease is usually an indication for surgical revascularisation. However, patients at prohibitive risk for coronary artery bypass grafts (CABG) can be directed to the angiography suite, accepting that unprotected LMCA stenting in the high-risk population carries a mortality of 9 % at 30 days and 11 % at 1 year [ 11 ]. Signifi cant risks associated with worse outcomes in the treat- ment of unprotected LMCA include a severely reduced LVEF (<35 %), a synchro- nous right coronary artery (RCA) occlusion, the use of angioplasty without stents, and the presence of signifi cant co-morbid conditions (older age and renal and respi- ratory failure). ECMO-supported LMCA stenting has been successfully reported for the fi rst time in 1996 by Irons et al. [ 12 ]; they described the case of a 70-year-old woman with intractable unstable angina despite heparin, nitrates, and an intra-aortic balloon pump (IABP). She was deemed to have unacceptable surgical risk due to end-stage COPD (FEV1 <0.46). She tolerated ECMO-supported LMCA stenting with multiple high-pressure balloon infl ations and only a transient sinus bradycar- dia, but no ST changes or haemodynamic instability.
Likewise, other successful cases have been reported [ 13 ]: our fi rst patient was an 81-year-old gentleman, who presented post STEMI with a 90 % LMCA stenosis and an estimated mortality risk by logistic EuroSCORE of 47 % [ 2 ]. The procedure was performed under general anaesthesia, and ECMO cannulation was established after femoral cut-down and a single bolus of 10,000 units of intravenous heparin.
ECMO fl ow was maintained at 2.5 L/min for the duration of the case, and weaned off after LMCA and RCA stenting. Note, we have since moved on to percutaneous cannulation with pre-close technique [ 4 ].
13.2.2 Emergent PCI Post Myocardial Infarction and Cardiogenic Shock
Patients with myocardial infarction (MI) who have out-of-hospital cardiac arrest and cardiogenic shock have a high mortality rate (5–10 % of all STEMIs) [ 14 , 15 ].
The SHOCK trial has since reported improved survival of up to 6 years with early revascularisation compared to initial medical stabilisation and delayed revasculari- sation in this subset of patients [ 16 ]. The use of peri-procedural circulatory support has become increasingly common with the availability of percutaneous left ven- tricular support devices such as the Impella recover LP2.5 (Abiomed Europe GmbH, Aachen, Germany), TandemHeart (Cardiac Assist inc., Pittsburgh, PA) [ 17 ], or the
use of IABPs. However, such devices support only the left ventricle, cannot take over the patient’s gas exchange function, have high disposable costs, and lately the use of IABP in this setting has been strongly questioned [ 18 ]. If systemic hypoxia cannot be treated rapidly and effectively, the oxygen supply to the heart, brain, and tissues will remain poor; restoration of spontaneous circulation will then be very unlikely.
VA ECMO provides a less expensive full cardiopulmonary support in patients who suffer an acute and profound but potentially treatable cardiac insult, complicated by cardiogenic shock and recurrent cardiac arrest despite inotropes and IABP [ 19 , 20 ].
Patients with profound cardiogenic shock will often present with a cardiac index below 1.5 L/min/m 2 and consequent acidosis secondary to hypoperfusion leading to multi-organ failure. Prompt initiation of ECMO support with a fl ow rate of 2.5–5 L/
min, depending on the patient’s afterload and intravascular volume, will quickly sta- bilise the haemodynamic status, providing adequate cardiac output and peripheral perfusion [ 21 ]; once rescued from the acute insult, the patient can “rest on ECMO”
until complete revascularisation with PCI or coronary bypass is achieved [ 22 ].
In the case of intra-procedural cardiac arrest, rapid mechanical chest compres- sion is initially necessary to prevent no or low blood fl ow episodes [ 23 ]. However, external cardiac compression is often not compatible with successful PCI, leading to loss of wire access in the target vessel, unsuccessful revascularisation and pro- longed procedures, or complete breakdown. Mechanical chest compression devices can be supportive but are often responsible of severe thoracic and intra-abdominal damage [ 24 ].
Lee et al. reported two cases of VA ECMO-assisted PCI in patients suffering cardiac arrest and cardiogenic shock post STEMI [ 25 ]: one patient was successfully bridged to transplant after ECMO-supported PCI, while the other one survived the initial procedure but succumbed later to a severe anoxic brain injury. In this sce- nario, timing is essential: “door-to-balloon” time should be within maximum 45–60 min. If circulatory support is necessary, ECMO should be ideally established within 10–15 min. This requires all of (1) impeccable coordination between cardiac surgeons, cardiologists, perfusionists, and anaesthetists; (2) familiarity with percu- taneous cannulation; and (3) prompt availability of cannulae in different sizes and lengths.
Despite ECMO support, the outcome in this setting remains dismal. In a retro- spective review of 36 patients with post-MI cardiogenic shock necessitating extra- corporeal mechanical support, PCI was attempted in 11 patients and was successful in only seven cases. Four patients were weaned from ECMO within 48 h, but none survived to hospital discharge [ 13 ]. Arlt et al. reported 50 % in-hospital mortality in a group of 14 patients who developed circulatory arrest in the cath lab during PCI or TAVI and required emergent extracorporeal life support [ 21 ]. In the PCI group (nine post-acute MI and one pre-transplant diagnostic cath), only four patients survived to hospital discharge. Finally, the Cleveland Clinic retrospec- tively analysed 138 patients who suffered post -acute MI cardiogenic shock [ 26 ];
patients who underwent revascularisation and circulatory support including ECMO as a bridge to cardiac transplantation experienced a signifi cant 5-year survival benefi t.