Case Presentation: 72-year-old male with h/o HTN, DM, obesity, polymyalgia rheumatica (on steroids), CKD stage IV, ankylosing spondylitis, and HFrEF (LVEF 45-50%) underwent total knee arthroplasty with removal of prior implant and distal femur replacement for osteosarcoma. Cut to close time was 9 hours. Intraoperatively, the SBP dipped to 90s for about 10-15 minutes after induction of anesthesia, following which the case ran on pressors. The estimated blood loss was 2 liters and 8 units of pRBCs were transfused. On postoperative day (POD) 0, the patient was hypotensive with SBP 80-90s and heart rate of 110s. The patient appeared well overall with no reported CP/SOB. The patient was fluid resuscitated and given stress dose steroids, with improvement in SBP to 90-110s and heart rate to low 100s. Hematocrit stayed stable at around 28% on POD 0-1 (preoperative hematocrit was 37%). On POD 1, mid-afternoon, the patient was noted to have diaphoresis and abdominal bloating. No anginal symptoms preoperatively but limited functional capacity due to orthopedic issues. Because of significant cardiac risk factors (male, age, HTN, DM, obesity, CKD, ankylosing spondylitis), troponin and ECG were ordered. Troponin was elevated at 20.6 ng/mL (normal < 0.055 ng/mL). Troponin added on to the morning labs on that day was 14.5 ng/mL. NT-proBNP was 5,559 pg/mL. ECG showed new incomplete left bundle branch block pattern, with ST elevation in aVR, and diffuse ST depression. TTE showed reduction in LVEF to 35-45% with apical, septal, and anterior wall hypokinesis, new compared to the TTE five months ago. The patient treated as Type I MI. Aspirin and heparin drip were started POD 1. Patient underwent complex PCI with 3 overlapping stents from left main into LAD. Subsequent hospital course was complicated by VF arrest, cardiogenic and septic shock with multiorgan failure, ECMO, ATN/CRRT, and GI bleed. The patient passed away on POD 61. Autopsy revealed gangrenous fungal cholecystitis, ischemic bowel, large periprosthetic hematoma, and acute subarachnoid hemorrhage.

Discussion: Postoperative MI occurs in 1% of the patients after major surgery. MINS or Myocardial Injury after Noncardiac Surgery encompasses troponin elevation (related to an ischemic mechanism) with or without MI, typically between POD 0-3. MINS has been associated with increased risk of 30-day mortality and nonfatal cardiac arrest. Consequently, there have been recommendations to consider postoperative surveillance for MINS, at least in high-risk patients. However, screening for MINS is not widely accepted as there are no clearly proven effective interventions to prevent or manage MINS (except in the setting of an MI). Over 20% of the postoperative patients can have MINS but less than 10% of these patients may have ischemic symptoms (masked by perioperative sedation and analgesia), and only one in four may have an ischemic ECG finding. One in five patients with MINS meet the criteria for MI and over 70% of these patients have obstructive CAD. With the paucity of ischemic symptoms in these patients, several patients with postoperative MI may remain undiagnosed in the absence of troponin surveillance.

Conclusions: Diagnosis of postoperative MI is challenging as symptoms are often masked or atypical and a high index of suspicion is needed. Distinguishing between Type 1 and Type 2 MI presents another challenge; additional imaging is needed and often consultation with a cardiovascular disease specialist is obtained.

IMAGE 1: Preoperative ECG

IMAGE 2: ECG on postoperative day 1