During the second annual Houston Shock Symposium, Sriram Nathan, MD, associate professor, director, cardiogenic shock director, Advanced Heart Failure Fellowship Program, Center for Advanced Heart Failure, University of Texas Health Science Center at Houston, shared current data pertaining to postoperative right ventricular (RV) failure after left ventricular assist device (LVAD).
Incidence of RV failure varies significantly, from 20% to 50%, according to Dr. Nathan, because it has not been consistently defined in previous studies. LVAD patients with RV failure have significantly lower one-year survival rates compared to patients without RV failure. Some mechanisms of RV failure after LVAD include:
- RV speed after load improvement after LVAD is unpredictable
- RV preload increases due to increased LVAD flow when RV is already compromised
- Unloaded LV leftward septum shift impairs RV contraction efficiency
- Postoperative and perioperative RV ischemia
- Perioperative volume resuscitation
Based on previous studies, predictors of RV failure include:
- Female gender
- Non-ischemic etiology
- Prior cardiac surgery
- Need for intra-aortic balloon pump (IABP)
- Inotrope dependency
- Vasopressor use
- Need for mechanical ventilation
- End organ hypo-perfusion (altered mental status, liver failure, and renal failure)
- Systolic blood pressure
Hemodynamic predictors are important, and while they are not definitive or replicated in all studies pertaining to RV, they can be helpful, according to Dr. Nathan. Some numbers that may predict RV failure include: increased central venous pressure (CVP) >15; CVP/pulmonary capillary wedge pressure ratio >0.63; low cardiac index <2.2; Right Ventricular Stroke Work Index <0.25 mmHg/L/m2; pulmonary artery pulsatility (PAP) index <2; and mean arterial pressure/central venous pressure (CVP) <7.5.
Despite some indicators, predicting RV failure continues to pose a significant challenge for practitioners. The definition of RV failure remains varied. There is also no reliable way to predict blood transfusions requirements or surgical complications that may occur during LVAD implant, and reliable RV function assessment does not currently exist. None of the developed risk models have consistently been able to predict RV failure.
RV failure management can be stratified into three categories: preoperative, perioperative, and postoperative.
In the preoperative period, diuresis is recommended, or ultra filtration if this is not effective. The goal is to bring the patient’s CVP below 15. Phosphodiesterase-5 inhibitors, IABP, or percutaneous ventricular assist devices may be used to decrease PAP. During surgery, Dr. Nathan said to avoid hypoxemia and acidosis, minimize transfusion usage and cardiopulmonary bypass time, and always use RV inotrope support. Postoperatively, Dr. Nathan said his center utilizes the left atrial pressure line. He also recommended the use of inhaled nitric oxide and prolonged ino-dilators (gradually weaning patients off).
In sum, Dr. Nathan said in the midst of the uncertainty surrounding RV failure, “Patient selection remains the number one predictor for post-LVAD RV failure,” he in his presentation conclusion. “In 2019, we still don’t know much about [the] RV.”