Cardiac issues in the ICU
Heart rhythm
Preexisting cardiac conduction system disease is common in patients undergoing AVR, and in one study it was identified in 23% of patients preoperatively 28. Baseline conduction abnormalities (particularly bundle branch blocks (BBB)) have been identified as a major risk factor for post-procedural permanent pace maker (PPM) 28, 29. Depending on the type of valve (Sapien versus CoreValve), post TAVR PPM is reported in 1.8–8.5%, and 19.1–42.5%, respectively 9. Anatomical compression on the conduction system by the prosthesis is likely a major contributing factor to postoperative conduction defects.
New onset atrial fibrillation (NOAF) after TAVR is also common and was identified in 31.9% of patients in one prospective study, at a median time of 48 hours postoperatively 30. NOAF was more common with a larger left atrial size and with TA-TAVR. While associated with a higher risk of stroke, NOAF did not increase mortality in this study.
Cardiac pacing wires are used intraoperatively to allow rapid cardiac pacing during valve deployment. These wires may be left in place afterwards in patients who experience heart block during the procedure or who have risk factors for arrhythmias postoperatively (preexisting BBB, large left atrial size). While patients who develop heart block during the procedure may be paced in the ICU until PPM can be placed, a backup mode may be useful in patients at risk for arrhythmias. Avoidance of negative chronotropes (beta blockers, digoxin, etc) is prudent in patients with preexisting BBB at risk for worsening arrhythmias.
Other cardiac complications
While cardiac complications are common in patients undergoing TAVR, the vast majority are intraoperative events that are diagnosed and treated before the patient arrives in the ICU. Complications seen intraoperatively include coronary artery occlusion from malposition of the graft, myocardial infarction, tamponade, rupture of aortic root or annulus, mitral valve apparatus injury, excessive bleeding, valve migration, and paravalvular leak. Signs of apical myocardial infarction may be seen on electrocardiograms postoperatively and are often related to apical puncture to facilitate valve placement in TA-TAVR.
Labile hemodynamics are common in the immediate postoperative period following TAVR. Left ventricular hypertrophy and diastolic heart disease often make patients very volume responsive, and hypotension is often responsive to volume resuscitation. Hypertension that is not pain related may be managed with nicardipine, a rapidly titratable calcium channel blocker. While there are no well established guidelines for BP management postoperatively, we believe targeting a mean arterial pressure of 60–80 is reasonable.
Pulmonary considerations in the ICU
Patients undergoing TAVR are considered inoperable by traditional criteria. Coexisting pulmonary disease, most notably chronic obstructive pulmonary disease (COPD), is common in this patient population and was present in 41% of patients randomized to TAVR in the original PARTNER trial 3. Of note, 21% of patients had oxygen dependent COPD. The combination of severe lung disease, postoperative pain from sternotomy, and prolonged time under anesthesia in patients undergoing traditional AVR may contribute to difficulty with ventilator weaning in the ICU. In contrast, we believe many patients undergoing TAVR may be fast tracked and extubated at the end of the procedure, appreciable largely to the absence of sternotomy and less postoperative pain, shorter surgical times and less exposure to anesthesia.
The need for reintubation in the postoperative period may be related to two primary factors-pain, particularly following TA-TAVR, and pulmonary edema. LVH and diastolic heart disease that often accompanies AS may necessitate significant volume resuscitation to maintain stable hemodynamics. As this volume equilibrates in the early postoperative period, pulmonary edema and effusions may develop. This fluid buildup, particularly pleural effusions, may be more clinically significant than following traditional AVR, as chest tubes are not usually placed for TF-TAVR, and only one may be present after the TA-TAVR. Thoracentesis to remove pleural fluid may be necessary as the need for higher cardiac filling pressures to maintain hemodynamics may prevent aggressive diuresis.
Renal failure in the ICU
Given the high acuity of patients undergoing TAVR, it is not surprising that a significant percentage suffer from renal insufficiency. Five percent of patients randomized to TAVR in the PARTNER trial had a baseline creatinine > 2mg/dL 3, and almost 50% of patients in another series had preoperative renal failure 31. The requirement for intra-arterial contrast medium predisposes patients to acute (ARF), or acute on chronic renal failure postoperatively. In a series of 110 TAVR patients, new onset post-procedure acute kidney injury (AKI) was found in 9% of patients, while 35% of patients with preexisting renal insufficiency experienced acute on chronic failure 31. In the majority of cases, ARF was mild and transient, with only one patient requiring hemodialysis. Perioperative red blood cell transfusion has been associated with AKI in TAVR patients 32.
Numerous studies have sought to identify ways to prevent and treat contrast-induced nephropathy (CIN). Techniques include ensuring excellent perfusion pressure, administration ofN-acetylcysteine, hydration with normal saline or sodium bicarbonate, and post-procedure hemofiltration. While the data is plentiful on the topic, the results are inconsistent regarding the optimal preventive strategy for CIN. Aggressive hydration with sodium bicarbonate carries risks of pulmonary edema and hypercarbia, particularly in the TAVR patient population where heart failure and COPD are common. In patients with significant cardiopulmonary comorbidities, avoiding hypotension and minimizing contrast exposure may be the most prudent ways to decrease the risk of CIN.
Vascular access complications
Vascular complications are common after TAVR and occurred in 30% of patients in the PARTNER trial (16% were major complications) 3. In a prospective study of 130 TF-TAVR patients, vascular complications were predicted by center experience, femoral calcification, and the sheath to femoral artery ratio score (SFAR) 33. In a review of 101 patients undergoing TF-TAVR, vascular access complications occurred in 32%, and 10% required surgical repair34. Vascular complications include retroperitoneal hemorrhage, femoral or iliac artery dissection, and development of a femoral pseudoaneurysm.
Some complications may become apparent intraoperatively. However, initial recognition of a vascular access complication is often detected in the ICU postoperatively. Proper techniques must be ensured with removal of any femoral arterial sheath. Pressure at the puncture site must be held for an adequate length of time (usually 3–5 minutes for each French size of the catheter), in order to achieve hemostasis. Inadequate pressure can result in pseudoaneurysm or hematoma formation. At our institutions, we remove femoral access sheaths in the OR before the patient is transported to the ICU.
The presence of a high femoral arterial stick (above the inguinal ligament) may first present in the ICU with the development of a retroperitoneal bleed when the line is removed, despite adequate pressure being held. We believe hypotension presenting in the hours after arterial line removal should trigger a rapid workup for possible retroperitoneal hemorrhage. Non-contrast computed tomography (CT scan) is the study of choice to identify a retroperitoneal bleed, but in the presence of unstable hemodynamics, abdominal tenderness and a newly removed formal arterial catheter, it may be prudent to proceed directly to the OR for surgical exploration.
In a retrospective review of more than 9000 patients undergoing femoral artery catheterizations, presenting signs of retroperitoneal hematoma included suprainguinal tenderness in 100% of patients, severe back pain in 64%, and femoral neuropathy in 36% 35. The diagnosis may be more difficult if the patient is sedated or mechanically ventilated, and a high index of suspicion is needed.
Conclusion
TAVR is an innovative method to treat aortic valve disease in high risk patients. Its minimally invasive nature eliminates the need for sternotomy, CPB, and reduces procedural and anesthesia time. Nevertheless, TAVR is a major surgical procedure with considerable morbidity and mortality, and intensivists caring postoperatively for these patients must be able to treat the immediate postoperative complications. Prompt recognition of postoperative neurologic events, cardiac arrhythmias, renal failure, vascular complications and hemorrhage are critical to improve patient safety and outcomes.