Mitigation of Modifiable Comorbidities

Preoperative assessment of organ dysfunction should be performed. Correction of preoperative anemia may result in fewer blood transfusions during surgery. With moderate- to high-risk patients (EuroSCORE II >4), a hemoglobin level less than 11 g/dL is associated with a 3-fold increase in morbidity risk. Acute kidney injury may warrant a nephrology consult or further investigation of cardiorenal dysfunction. Assess for malnutrition with liver function tests and albumin or pre-albumin levels. It is important to assess if the patient is acutely decompensated from a cardiac perspective. Is there time for and benefit from outpatient GDMT? Is admission for preoperative right-sided pressure monitoring warranted? Consider preoperative inotropes and/or mechanical support.

Preoperative IABP

In patients with poor LV function, preoperative IABP can affect outcomes.^7–10 A 2011 meta-analysis evaluated preoperative IABP vs no IABP in 5 randomized, controlled trials that included patients with LVEF less than 30% to 40%, redo CABG, or unstable angina with tight left main stenosis.⁷ They found a profound decrease in LCOS (HR, 0.14; 95% CI, 0.08–0.25; P < .00001) and mortality (HR, 0.18; 95% CI, 0.08–0.41; P < .0001) in patients with preoperative IABP. In one of these studies, Christenson et al⁸ randomized patients to preoperative IABP vs no intervention and found that prophylactic IABP increased cardiac index from 1.52 L/min before IABP to 3.20 L/min on weaning from cardiopulmonary bypass (CPB). In the control group, cardiac index remained less than 2.0 L/min on weaning from CPB. The difference between the groups persisted up to 96 hours postoperatively, even following IABP removal, which generally occurred on postoperative day 1. There was no difference in the impact of prophylactic IABP whether it was placed intraoperatively before going on CPB or at 12 or 24 hours preoperatively; all were beneficial. Prophylactic IABP can also decrease the incidence of acute kidney injury by 46% and the need for kidney replacement therapy by 82%.¹⁰ Prophylactic IABP is beneficial in high-risk cardiac patients by increasing myocardial perfusion during diastole; decreasing myocardial oxygen consumption, LV afterload, and LV wall tension; increasing cardiac output (generally by 0.5–1.5 L/min); and decreasing systemic vasoconstriction.

Preoperative Inotropic Support

Levosimendan is a calcium-sensitizer with inotropic and vasodilatory effects. Levin and colleagues¹¹ randomized 252 patients undergoing CABG with severely diminished LV function (LVEF less than 25% to 30%). Levosimendan or placebo was started 24 hours preoperatively. There was a 50% increase in cardiac index and 33% decrease in pulmonary artery pressures in the levosimendan group up to 48 hours postoperatively. Postoperative LCOS was more common in the control group (20.8% control vs 7.1% levosimendan; P < .05) as was mortality (12.8% vs 3.9%, respectively; P < .05). Fewer patients required additional inotropes (7.9% vs 58.4%; P < .05), vasopressors (14.2% vs 45.6%; P < .05), or an IABP (6.3% vs 30.4%; P < .05) in the levosimendan group than in the controls.

Mehta et al¹² performed a similar analysis, but with a higher LVEF cutoff of 35% or less. Compared with the study by Levin and colleagues¹¹ in patients with LVEF below 25%, they found no difference in the composite endpoint of death, kidney replacement therapy, perioperative MI, or use of a mechanical cardiac assist device between the levosimendan and control groups. Subgroup analysis, however, demonstrated improved outcomes in patients undergoing isolated CABG compared with those undergoing isolated valve procedures or combined valve/CABG procedures.¹³ In patients undergoing isolated CABG, the incidence of LCOS was lower with levosimendan (HR, 0.48; 95% CI, 0.30–0.76), and 90-day mortality improved (HR, 0.36; 95% CI, 0.11–0.64).

A study from John et al¹⁴ found that both levosimendan and dobutamine improved cardiac index and ejection fraction and decreased serum creatinine in patients with acute decompensated heart failure. In addition, levosimendan reduced intensive care unit length of stay, whereas dobutamine reduced hospital length of stay. Guerrero-Orriach et al¹⁵ similarly found that both levosimendan and dobutamine improved cardiac index and vascular tone in postoperative cardiac patients with LCOS, but levosimendan had a more beneficial effect on kidney function. Ventricular tachyarrhythmia has been the main adverse event with levosimendan. Greco et al¹⁶ performed a bayesian network meta-analysis of 46 trials that randomized 2,647 patients. They found that prophylactic levosimendan was associated with a decrease in mortality compared with placebo (HR, 0.48; 95% CI, 0.28–0.80), and the effect was greater than that with other inotropic agents. Dobutamine and milrinone were also effective, but to a lesser degree than levosimendan in their analysis.^16,17

The Mount Sinai group in New York advocates preoperative hemodynamic optimization for high-risk patients undergoing mitral intervention.¹⁸ Their practice is to admit high-risk patients for right-sided pressure monitoring, preoperative inotropic support, and diuresis. Milrinone is their current inotrope of choice. Optimization for 24 hours preoperatively decreased systolic pulmonary artery pressure by 33%, from 63 mm Hg to 39 mm Hg, with more effective diuresis. Patients lost an average of 3.7 kg preoperatively with short-term optimization.

Perioperative Mechanical Support

It is beyond the scope of this paper to describe in detail the differences between the varying forms of mechanical circulatory support; however, the TandemHeart (LivaNova) and Impella (Abiomed, Inc) systems are the 2 favored devices for temporary left-sided support when an IABP is contraindicated or would not provide enough support.^19,20 If right-sided heart failure is the main problem or adequate oxygenation cannot be achieved, full extracorporeal membrane oxygenation would be required. Left-sided support, however, is generally sufficient for prophylactic nonemergent surgical interventions. The TandemHeart is an extracorporeal centrifugal flow pump with its inflow cannula placed through the femoral vein and into the left atrium via a transseptal approach. The outflow cannula is inserted into the femoral artery, generally with a distal perfusion catheter to minimize ischemia to the leg. The Tandem-Heart improves hemodynamic and metabolic parameters over IABP in patients with intractable shock, although bleeding and limb ischemia are more prevalent with the TandemHeart than with the Impella device.

The Impella device is a nonpulsatile axial-flow pump that resides in the left ventricle and pumps blood from the ventricle into the aorta beyond the aortic valve. Although a low-flow percutaneous device (Impella CP) can be placed via the femoral artery (14F, flow of 2–3 L/min), only short-term (≤4 days) use is appropriate. The Impella 5.5 pump is the authors' preferred approach for prophylactic perioperative use. It is placed either preoperatively via a tunneled axillary chimney graft (surgically placed 10-mm Dacron conduit) or intraoperatively via a graft placed on the innominate artery. Two reports described satisfactory outcomes with the Impella 5.5 device for postcardiotomy syndrome^21,22; however, the authors have started to place an Impella 5.5 device the day before high-risk CABG in patients with extreme lows of LVEF. Benke and associates²³ reported on 14 patients with mean ejection fraction of 21% undergoing cardiac surgery with a prophylactic high-flow Impella pump. Although they did not have a comparator group, they found prophylactic Impella pump use to be a safe approach with acceptable outcomes in these patients at high risk for morbidity.²³