The Cardiology Consult Service was asked to evaluate a postoperative 65-year-old male who underwent a hemicholectomy for recurrent GI bleeding. During the operation he had an episode of hypotension with a systolic blood pressure that decreased into the 70s that lasted approximately 20 minutes; blood pressure normalized after administration of fluids. The postoperative ECG showed nonspecific ST-T abnormalities with 0.5 mm ST downsloping depression in leads V 5-6, different from his preoperative ECG. Serial cardiac markers were sent immediately after surgery, 6, 12 and 18 hours postoperatively.
Consultation was requested due to an elevated TnT.
Preoperatively, the patient had normal functional status. He did not exercise regularly but was able to do his daily activities without difficulty. No prior cardiac evaluations were performed other than an ECG, which demonstrated LVH with minor ST-T changes.
Past Medical History: No prior cardiac history; hypertension, tobacco use
Lisinopril 20 mg per day
Hydrochlorothiazide 12.5 mg daily
Physical examination at the time of evaluation;
Vital Signs BP 125/85 mmHg, HR 82 bpm, respiratory rate 16, afebrile Neck: no obvious JVD Lungs: clear, A&P Cardiac: displaced PMI laterally, RRR, normal S1 and S2, no murmurs Abdomen: midline incision with sutures, mild tenderness to palpation Extremities: pulses intact, no edema
What would be your next step to evaluate this patient?
The correct answer is: 4. Add aspirin and metoprolol when not contraindicated, start a statin, order an echocardiogram, and an outpatient stress test.
Our choice in this example is #4: Add aspirin and metopropol when not contraindicated, start a statin, order an echocardiogram, and outpatient stress test.
This patient meets the criteria of type 2 AMI as evidenced by TnT elevation and ischemic EKG changes.
There have been a number of studies that have evaluated the role of troponins after non-cardiac surgery. Initial data, derived from patients undergoing vascular surgery, who have an increased risk for having underlying CAD, demonstrated a substantial increase in long term mortality in patients who had troponin elevations after surgery.1 More recent data has corroborated these studies.2,3 A recent large study that included patients undergoing non-cardiac, non-vascular surgery found that even minor elevations in TnT (using the same assay as the patient in this case) demonstrated an increased risk of mortality for even minor elevations.4 In this study, low TnT values just above the 99th percentile were associated with four fold increase in overall mortality.
The appropriate evaluation of an asymptomatic patient with an Tn elevation after non-cardiac surgery is unclear. Elevations after surgery are likely multi-factoral. In a small subset, plaque rupture with subsequent vessel occlusion can occur, resulting in ST elevation (Type 1 MI5). More commonly, Tn elevations likely reflect Type II MI, in which the patient has stable coronary disease, but an episode of hypotension or tachycardia may result in demand ischemia and subsequent Tn elevation and MI.5
In this patient troponin sampling was ordered primarily because of the asymptomatic hypotension, a condition commonly associated with subsequent MI.2 Although it is clear that such troponin elevations are a marker for increased mortality, in an asymptomatic patient, coronary angiography in the absence of ECG changes or marked elevation of cardiac markers would seem inappropriate.
However, standard secondary prevention measures should be considered for most patients, as they may improve outcomes.3 This would include aspirin (once the risk of bleeding is reduced), statins (have been shown to substantially reduce mortality, although the mechanism is controversial) and adding a beta-blocker for patients who can tolerate it. Assessment of LV function can be useful in assisting in determining what medications can be used and how rapidly they can up titrated. In addition, demonstration of segmental wall motion abnormalities would increase the likelihood and suspicion that the patient did have underlying coronary disease and that indicates further evaluation, such as stress testing, would be warranted.
Landesberg G, Shatz V, Akopnik I, Wolf YG, Mayer M, Berlatzky Y, Weissman C, Mosseri M. Association of cardiac troponin, CK-MB, and postoperative myocardial ischemia with long-term survival after major vascular surgery. J Am Coll Cardiol 2003;42:1547-54.
Levy M, Heels-Ansdell D, Hiralal R, Bhandari M, Guyatt G, Yusuf S, et al. Prognostic value of troponin and creatine kinase muscle and brain isoenzyme measurement after noncardiac surgery: a systematic review and meta-analysis. Anesthesiology 2011;114:796-806.
Devereaux PJ, Xavier D, Pogue J, Guyatt G, Sigamani A, Garutti I, et al. Characteristics and Short-Term Prognosis of Perioperative Myocardial Infarction in Patients Undergoing Noncardiac Surgery: A Cohort Study. Ann Intern Med 2011;154:523-8.
Devereaux PJ, Chan MT, Alonso-Coello P, Walsh M, Berwanger O, Villar JC, et al. Association between postoperative troponin levels and 30-day mortality among patients undergoing noncardiac surgery. JAMA 2012;307:2295-304.
Thygesen K, Alpert JS, Jaffe AS, Simoons ML, Chaitman BR, White HD; Writing Group on behalf of the Joint ESC/ACCF/AHA/WHF Task Force for the Universal Definition of Myocardial Infarction. Third universal definition of myocardial infarction. J Am Coll Cardiol 2012;60:1581-98