Right Ventricular Dysfunction or Failure
during EMO Therapy
Acute right heart failure is defined as acute right heart dysfunction plus low cardiac output and hypo-perfusion with the consequent multi organ dysfunction/failure. Right ventricle (RV) failure occurs when the RV fails to provide enough blood flow to the pulmonary circulation to accomplish adequate left ventricle filling.
Our goal is to discuss RV dysfunction and failure in basic easy to understand terms, as well as how it can impact ECLS therapy and be managed appropriately to offer the best patient support. What are we assessing, how can we diagnose, and what kind of impact does it have on ECLS therapy? This information is presented in perspective primarily with the adult VV ECLS population in mind.
Paramount to understanding the right ventricular and its impact are key concepts of the differences in dysfunction versus failure. In the event that a right ventricle is found to be under stress from various effects does not necessarily mean that it is failing or strained enough to cause decreased cardiac index, left ventricular filling, or organ dysfunction.
Acute right ventricular dysfunction is potentially lethal in critically ill patients.
“The right and left ventricle contract in very different patterns that can be further explored. This finding implies that RV emptying is very sensitive to changes in afterload and shows that the RV may have late phase ejection while the LV is in diastole.” (Grignola)
What is RV Failure
The right ventricle of the heart is impacted when there is pressure or volume overload that inhibits blood flow out of the ventricle. The most common cause of this phenomenon is pulmonary hypertension. Pulmonary hypertension is simply high pressure in the pulmonary vasculature most commonly from disease, volume overload or left ventricular failure.
The most frequent cause of pulmonary hypertension is left ventricular failure but can also be a result of ARDS, cystic fibrosis, pulmonary fibrosis, pulmonary emboli, emphysema and the like. ARDS is frequently complicated by pulmonary hypertension causing right ventricular failure. “In the presence of ARDS, 30-56% of people have shown to develop RV dysfunction. Why does RVD occur in ARDS? Hypoxic vasoconstriction, an increased alveolar dead space, pulmonary microthrombi, and inflammatory cytokine activation.” (Grignola)
In the presence of a myocardial infarction that impacts vessels that innervate the right ventricle (which make up 40% of inferior STEMI’s), tissue distal to the occlusion does not receive adequate oxygenated blood flow and can decline in function, or fail. This will cause the segment of the heart that was once perfused and contracting appropriately to eject blood from the right ventricle, to lose its capability and become hypo-kinetic or akinetic (decreased or absent motion).
When blood in the right ventricle cannot follow the normal pathway and move forward into the lungs, it backs up causing congestion, dilation, and increased pressure. The right ventricle can potentially improve if appropriate intervention is taken prior to multi-organ dysfunction and failure.
Grignola: reference link here
Assessment
Patient assessment can reveal:
Increasing edema
Jugular venous distention
Trend down in urine output
Positive fluid balance with increasing vasopressor support
Important clinical assessment pieces to evaluate RV function include:
Central venous pressure
Pulmonary artery pressure
AST
ALT
Lactate
Troponin
pro-BNP
Urine output
Hypotension
Trending these values is critical to identifying acute changes.
Diagnosis
An official trans-thoracic or trans-esophageal echocardiogram is the best way to diagnose right ventricular dysfunction or failure. Identify and evaluate tricuspid regurgitation, long axis cavity size, short axis septal kinesis, septal flattening, RV compared to LV size, loss of inspiratory collapse, and dilation of the pulmonary artery. You will note that the apex will lose its triangular shape.
Tricuspid annular plane systolic excursion (TAPSE) can be used to identify dysfunction where <15 is classified as moderate to severe dysfunction; <20 is classified as dysfunction. Right ventricular myocardial performance index is used for the assessment of global right ventricular function.
Electrocardiogram can indicate RV dysfunction in the presence of myocardial infarction - ST elevation in right sided chest leads - V4R, and RV strain as demonstrated with corresponding ST depression and T wave inversion in leads corresponding to the right ventricle - leads II, lead III (most pronounced because it is the most rightward facing lead) and aVF. A lateral chest x-ray can also show dilation of the RV.
Impact
The right ventricle is extremely sensitive to increased pressure and volume overload. Understanding right ventricular preload, afterload and ventricular interdependence is imperative (for additional information about this dynamic, read here).
In an acute setting, the RV is unable to generate a mean pressure greater than 40mmHg. Stroke volume decreases significantly as right ventricular afterload increases, demonstrating that the right ventricle is much more sensitive than its neighbor. Elevations in RV preload most commonly occur secondary to an increase in intravascular volume or tricuspid regurgitation.
Successful outcomes of acute RV failure is predicated on rapid identification, intervention, and management of its underlying cause.
Interventions
Pharmacological Support
Nitric Oxide
Flolan
Anticoagulation
Thrombolysis or embolectomy
Milrinone
Epinephrine
Fluid overload in patients with ARDS can exacerbate RV failure - with or without ECMO. Fluid balance should be as neutral as possible. (Read more here)
Mechanical Support
Impella RP
The Impella RP is a device which offloads the right ventricle by moving blood from the inferior vena-cava into the pulmonary artery with the use of a very small blood pump. It is the only percutaneous, single vascular access pump approved for right heart support. It delivers flows greater than 4 LPM.
In the event that a patient needs right ventricular support, this device can be placed to assist with heart recovery. Concomitant use of this device with ECLS therapy brings an interesting dynamic into play. In addition to ECLS cannulae access points, the Impella RP would need to placed and positioned appropriately for whichever modality of ECLS therapy in use.
In the event that the RV is failing due to left ventricular (LV) pressure, consider supporting the LV by first identifying the problem and identifying the need for support - offload the LV with Impella CP, 5.0 or 5.5 support, surgical intervention, or additional mechanical or pharmacological support.
Cannulation Strategy
Protek Duo Cannulae
A cannulation strategy used to offload, support, and protect the right ventricle is to utilize the Protek Duo Cannulae. This dynamic dual lumen catheter is versatile and allows for increased progressive patient mobility with a single access site in the right internal jugular vein.
The inflow multi-stage omni-directional 360-degree drainage ports unload the right heart by removing blood from the right atria. The return multi-stage omni-directional 360-degree drainage ports terminate past the tricuspid and pulmonic valves, directly placing oxygenated gas exchanged blood into the pulmonary artery.
Recirculation potential with this cannulation strategy is minimal. Radiopaque markers at the tip of the cannulae allow for enhanced position evaluation via x-ray.
Cannulae sizes range start at 29Fr and increase up to 31Fr. Reported rated flow is as high as 5.5 LPM.
Atrial Septostomy
Percutaneous Balloon Atrial Septostomy
On occasion, a right to left atrial shunt of oxygenated blood can be created, unloading the right ventricle.
Spontaneous Atrial Septal Defect
It is reported that a patient encountering such elevated right ventricular pressure can create an ASD naturally. Whether or not the ASD is opened from a chronic unresolved PFO is yet to be researched to extent. This opening of blood flow from the right atria to the left atria while supported with VV ECLS creates a pseudo-VA ECMO therapy
ECLS Modality Change
When a patient is supported with VV ECLS, in the setting of acute RV failure, a change in cannulation strategy may be needed. Those with cannulation strategies that do not offload the right ventricle can be considered for a Protek Duo cannula. Cannulation with a Protek Duo is still considered VV ECLS since the cannula does not access the arterial system.
In the setting of severe RV failure there may be a need to convert to Veno-Arterial (VA) ECLS, with the return arterial cannula positioned in the subclavian artery to avoid Harlequin syndrome. This conversion to VA ECLS is done to achieve appropriate cardio-pulmonary support and provide adequate end organ perfusion. Additional cannulation strategies can be utilized such as VAV with alterations in blood flow appropriate for perfusion through the diverted cannula into the arterial system.
Common Questions
Can the right heart recover from dysfunction? Yes, with appropriate interventions and supportive measures.
Is it possible for the patient to develop an ASD or a chronic PFO open in the setting of high RV pressure? Yes.
How can a PFO or ASD be assessed without a bubble study with TTE? You will tend to see a wide variation in ABG PO2 values without any other changes to ventilator or gas flow strategies.
Should the right ventricle be supported even if the left ventricle is functioning properly? Yes. If the right ventricle is not able to pump blood in a forward, pressure will continue to rise inhibiting the RV function more.
Should patients in ARDS be given volume to increase their blood pressure? Careful evaluation of necessity should be taken. Use TTE or TEE as the determinate whether the patient would actually benefit from fluid resuscitation or not. Generally, patients who are in ARDS should be kept at a neutral fluid balance to avoid unnecessary strain on the RV.
How can I accurately assess volume status in my patient? CVP, trend in volume status over the last several days. Do you see chatter or suction events in your cannula? If not, the likelihood of your patient being hypovolemic is low.
How is the Protek Cannulae placed? Under guidance with fluoroscopy.
Has the Protek Cannulae ever been used off-label as a dual lumen drainage cannulae? Yes, there are reports that this has been done purely off-label in an effort to offload the right heart in the presence of cariogenic shock.
Sources of Information and Additional Reading:
https://jtd.amegroups.com/article/view/17361/html
litfl.com
American Lung Association - lung.org
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5715568/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4579681/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2774585/