This patient exhibits transient myocardial dysfunction following an episode of acute ischemia. Such reversible dysfunction is known as myocardial stunning.
Myocardial stunning occurs in the setting of short-term total reduction of coronary blood flow with subsequent reestablishment of coronary blood flow. Stunned myocardium exhibits LV dysfunction for a limited duration that subsequently resolves.
Campbell-Scherer and Green discuss guidelines for the management of ST-segment elevation myocardial infarction. They emphasize the importance of immediately chewing an aspirin once symptoms begin, the importance of percutaneous coronary intervention (PCI) within 90 minutes or fibrinolysis within 12 hours, and the proper post-STEMI management for immediate care as well as long-term secondary prevention.
Solomon et al. discuss the post-operative course of 352 patients diagnosed with q-wave anterior myocardial infarction who underwent echocardiography on day 1 after their MI, 14 days after, and 90 days after. They note that by day 90, 22% of patients with abnormal ejection fraction and wall motion abnormalities had complete recovery of function by day 90, attributable to myocardial stunning.
Answer 1: Reperfusion injury refers to myocardial damage caused by the formation of oxygen free radicals in the cardiac myocytes following return of perfusion. The lack of a permanent deficit in this patient's case makes reperfusion injury unlikely.
Answer 2: Ventricular remodeling refers to the chronic changes in cardiac shape, size, and myocyte composition that occur to compensate for a chronically increased hemodynamic load.
Answer 3: Like myocardial stunning, myocardial hibernation refers to ischemic dysfunction that is potentially reversible. However, myocardial hibernation typically results from chronic low-level ischemia such as that seen in patients with chronic angina, LV dysfunction, or heart failure. This differs from the acute process described above.
Answer 5: While the existence of coronary artery collaterals can decrease infarct size, aneurysmal dilatation, heart failure, and rupture risk following an acute MI, the disappearance of echocardiographic defects in this case can be better attributed to myocardial stunning as described above.
Campbell-Scherer DL, Green LA. ACC/AHA guideline update for the management of ST-segment elevation myocardial infarction. Am Fam Physician. 2009 Jun 15;79(12):1080-6.
PMID:19530638 (Link to Abstract)
Solomon SD, Glynn RJ, Greaves S, Ajani U, Rouleau JL, Menapace F, Arnold JM, Hennekens C, Pfeffer MA. Recovery of ventricular function after myocardial infarction in the reperfusion era: the healing and early afterload reducing therapy study. Ann Intern Med. 2001 Mar 20;134(6):451-8.
PMID:11255520 (Link to Abstract)
USMLE World Step 1 QBank Question #43. Copyright © USMLEWorld, LLC 2012