4th UDMI(Universial definition of MI)
- Landesberg G, Beattie WS, Mosseri M, Jaffe AS, Alpert JS. Perioperative Myocardial Infarction. Circulation 2009;119:2936–44.
- Redifinition of PMI
- most PMIs occur without symptoms in anesthetized or sedated patients, ECG changes are subtle and/or transient, and the creatine kinase-MB isoenzyme has limited sensitivity and specificity because of coexisting skeletal muscle injury. 8
- Yet, 90% of troponin elevations began within _24 hours.
- Pathophysiology
- Universial definition of MI
- Type 1 PMI (Acute Coronary syndrome)
- Physical and emotional streesses, | sympathetic induced hemodynamic, coronary vasoconstrictive, and prothrombotic forces thought to promote plaque disruption.
- Tachycardia and hypertension, common in the perioperative period, may exert shear stress,
- Increased postoperative procoagulants (fibrinogen, factor VIII coagulant, von Willebrand factor, _1-antitrypsin), increased platelet reactivity, 23decreased endogenous anticoagulants (protein C, antithrombin III, _2-macroglobulin), 24and decreased fibrinolysis 25have been reported
- Type 2 PMI (Myocardial Oxygen Supply-Demand Imbalance)
- Postoperative cardiac complications, including sudden death, 33,34occurred after prolonged (_30 minutes, (35,36)_2 hours, (37,38)or _5 hours(39,40)) silent ST-segment depression
- ST elevation occurred in _2% of postoperative ischemic events and was a rare cause of PMI. (12,30,41)Hence, prolonged, ST-depression–type ischemia is the most common cause of PMI.
- Although troponin elevation is common mainly among patients with history of CAD 41–44or moderate to severe ischemia on preoperative stress thallium scanning, 45troponin elevations occur also in the setting of septic shock, renal failure, or pulmonary embolism. (46)These causes, however, are less frequent and occur later after surgery than PMI.
- Tachycardia is the most common cause of postoperative oxygen supply-demand imbalance(12,47)
- Prognosis
- Early mortality after PMI ranges from 3.5% to 25%13,15,31,41,42,55 and is higher among patients with marked troponin elevation compared with patients with minor troponin elevation (0% to 7%). 15,41,42
- Prevention and Treatment
- Prophylatic theraphy
- Beta-blockers - POISE-I trial
- The large Perioperative Ischemic Evaluation (POISE) trial 6(8351 patients) reported increased mortality (by 31%) and stroke (by 100%), mostly in association with hypotension and bleeding, in patients treated with metoprolol despite a reduction in nonfatal PMI by 26%.
- Beta -Blockade may aggravate hypotension (12% of POISE patients) and interfere with the ability to maintain adequate cardiac output during active bleeding, anemia, or infection.
- The consensus is that long-term beta-blockade should not be discontinued. Intravenous beta-blockers are often used to treat tachycardia, hypertension, or ischemia with results comparable to or better than those reported with prophylactic beta-blockade.
- Perioperative management
- The importance of preventing even modest increases in heart rate cannot be overemphasized.
- All causes of tachycardia, hypertension, hypotension, anemia, and pain should be treated aggressively.
- Frequently, vasopressors to maintain blood pressure and _-blockers to slow heart rate while managing blood volume, postoperative pain, and respiratory function are necessary.
- Therefore, hematocrit between 25% and 33% is a gray zone in which transfusion must be individualized.
- Conclusion
- Postoperative tachycardia, hypotension, hypertension, anemia, hypoxemia, and systolic and diastolic myocardial dysfunction are common causes of prolonged ST-depression and type 2 infarction in patients with stable CAD undergoing major noncardiac surgery.
- PMI is often silent and its ECG changes are frequently transient, yet even minor troponin elevations predict early and late morbidity and mortality.
- Thygesen K, Alpert JS, Jaffe AS, Chaitman BR, Bax JJ, Morrow DA, et al. Fourth Universal Definition of Myocardial Infarction (2018). Circulation 2018;138.
4th UDMI
Perioperative MI
1. Perioperative MI is one of the most important complications in major noncardiac surgery and it is associated with a poor prognosis. 77,78
2. Most patients who have a perioperative MI will not experience ischemic symptoms due to anesthesia sedation, or pain relieving medications
3. Nevertheless, asymptomatic perioperative MI is as strongly associated with 30 day mortality as symptomatic MI. 77,78
4. It is recognized that the perioperative period is characterized by increased cardiac metabolic demand that may lead to MI in patients with otherwise stable CAD. 84,85
5. predominant etiology of perioperative MI,84,85 which together with a rise and/or fall of cTn values indicates type 2 MI.
However, other angiographic studies have detected coronary plaque rupture in 50% to 60% of patients with perioperative MI, 86,87which qualifies as type 1 MI.
