13.2 ECMO & LVAD Overview for the Cath Lab

Advanced Mechanical Support Beyond the Balloon Pump

When counterpulsation and Impella support are insufficient, the cath lab team may encounter extracorporeal membrane oxygenation (ECMO) and patients with implanted left ventricular assist devices (LVADs). Domain C Task 7 expects the RCIS technologist to understand how these systems function, what role the cath lab plays during insertion or management, and the safety rules that differ from standard catheterization. You are not expected to manage an LVAD program independently, but you must recognize device types, interpret console parameters, and avoid actions that harm supported patients.

Extracorporeal Membrane Oxygenation (ECMO)

ECMO is a temporary extracorporeal circuit that provides gas exchange and/or circulatory support outside the body. Blood drains through a large cannula, passes through a centrifugal pump and membrane oxygenator (artificial lung), and returns to the patient through an outflow cannula. The cath lab most commonly sees veno-arterial (VA) ECMO in refractory cardiogenic shock, post-cardiac arrest, or as a bridge during high-risk interventions.

VA ECMO Versus VV ECMO

VA ECMO bypasses both the lungs and a failing heart: deoxygenated blood is drained from the venous system, oxygenated through the membrane lung, and returned under pressure into the arterial system. This provides forward flow and oxygen delivery when the native heart cannot maintain adequate perfusion. Flow rates typically range from 3–6 L/min depending on patient size and cannula diameter.

VV ECMO supports gas exchange in severe ARDS while the heart continues to pump; it is less common in the cardiac cath lab but may appear in hybrid cardiovascular-critical care settings.

VA ECMO Cannulation and Cath Lab Role

Percutaneous femoral veno-arterial cannulation is the most frequent emergent configuration the RCIS team supports. A large-bore venous cannula (commonly 21–25 Fr) is advanced into the inferior vena cava or right atrium for drainage. An arterial outflow cannula (15–19 Fr or larger) is placed in the common femoral artery (or axillary artery when limb perfusion is a concern).

The RCIS assists with:

• Ultrasound-guided vascular access for large-bore cannulae
• Fluoroscopic confirmation of wire and cannula position
• Anticoagulation management — ECMO requires systemic heparinization; activated clotting time (ACT) targets are typically 180–220 seconds per institutional protocol
• Hemodynamic monitoring — arterial line, central venous pressure, and pulse oximetry on both the supported limb and a contralateral limb
• Distal perfusion catheter placement when femoral arterial cannulation risks limb ischemia

Hemodynamics and the "Harlequin" Phenomenon

During VA ECMO, the native heart may eject minimally or not at all. The arterial line may show a flat or dampened waveform because forward flow comes primarily from the ECMO pump, not ventricular contraction. Upper-body hypoxia can occur with femoral VA ECMO when the native heart recovers enough to eject deoxygenated blood from the lungs while ECMO-supplied oxygenated blood enters the lower body — the Harlequin (North-South) syndrome. Recognizing this pattern requires communication with the ECMO specialist and may prompt conversion to central cannulation or addition of an upper-body outflow cannula.

ECMO Complications Relevant to the Cath Lab

The RCIS does not independently titrate ECMO flow or sweep gas — those are perfusionist or ECMO specialist responsibilities. Your role is access support, monitoring, anticoagulation sample coordination, and rapid escalation when complications arise.

Left Ventricular Assist Devices (LVAD): Cath Lab Essentials

An LVAD is a durable or destination-therapy pump surgically implanted to support the failing left ventricle. Common platforms include HeartMate 3 (Abbott) and historically HeartWare HVAD (Medtronic). These are continuous-flow centrifugal pumps that draw blood from the LV apex through an inflow cannula and eject it into the ascending aorta through an outflow graft, bypassing the native ventricular outflow tract.

Unlike IABP or Impella, LVADs are long-term implants — patients may present to the cath lab months or years after implantation for coronary angiography, PCI, right heart catheterization, or device malfunction evaluation.

LVAD Physiology: What Looks Different

Continuous-flow LVADs produce non-pulsatile or minimally pulsatile arterial waveforms. Key implications for the cath lab:

• Blood pressure may be measured with a Doppler probe over the brachial or radial artery (reported as MAP in mmHg) because a standard cuff may not detect a pulse.
• Pulse oximetry may be unreliable on the same extremity used for Doppler BP; use alternative sites.
• Cardiac output is not calculated from traditional pulse pressure methods — rely on LVAD console parameters: speed (RPM), estimated flow (L/min), power (watts), and pulsatility index (PI).

LVAD-Specific Cath Lab Safety Rules

Chest compressions during cardiac arrest in patients with an implanted continuous-flow LVAD are controversial and institution-specific — some protocols permit modified compressions while others prioritize maintaining pump power and treating arrhythmias. Know your hospital's policy. Never disconnect the driveline or power source without the VAD coordinator present.

Right heart catheterization in LVAD patients requires careful wire and catheter manipulation to avoid entanglement with the inflow cannula at the LV apex. Coronary angiography is performed with attention to hemodynamic tolerance — reduce contrast load when possible and maintain MAP per VAD team orders.

Anticoagulation is mandatory: most LVAD patients are on warfarin (INR target typically 2.0–3.0 for HeartMate 3) plus antiplatelet therapy. Coordinate heparin during PCI with the VAD team to avoid supratherapeutic bleeding.

LVAD Alarms the RCIS Should Recognize

• Low flow alarm: Assess volume status, check for tamponade (bedside echo if available), verify speed settings, rule out kinked outflow graft.
• High power alarm: Suggests pump thrombus or outflow obstruction — notify the VAD coordinator and operator immediately; may require urgent device exchange or thrombolysis per protocol.
• Controller fault / battery depletion: Switch to backup batteries or hand pump immediately; never leave the patient without a power source.

Document all console parameters at baseline, after any hemodynamic change, and at case conclusion. The VAD coordinator or heart failure service should be present or immediately available for any invasive procedure on an LVAD patient.

Putting It Together: Escalation Pathway

The cath lab mechanical support ladder typically progresses as follows:

1. Pharmacologic support — inotropes, vasopressors
2. IABP — counterpulsation for moderate hemodynamic compromise
3. Impella — active LV unloading when greater flow is needed
4. VA ECMO — biventricular and respiratory failure
5. Durable LVAD or transplant — long-term or destination therapy

The RCIS technologist supports each transition with appropriate access, monitoring, anticoagulation coordination, and device-specific safety knowledge. On the RCIS exam, expect overview-level questions on VA ECMO cannulation configuration, limb ischemia prevention, continuous-flow LVAD physiology, and which parameters indicate pump thrombosis — not independent ECMO or VAD programming.