Combined etiology of anaphylactic cardiogenic shock: amiodarone, epinephrine, cardioverter defibrillator, left ventricular assist devices and the Kounis syndrome

The allergic myocardial infarction dilemma: is it the anaphylaxis or the epinephrine?

We highlight two distinct cases of myocardial infarction occurring concurrently with anaphylaxis at our centre in Singapore. The first case had cardiac symptoms and electrocardiogram changes concomitant with his anaphylaxis presentation, suggestive of Kounis syndrome, while the second case presented with anaphylaxis and only developed cardiac symptoms and electrocardiogram changes after treatment with intramuscular epinephrine, suggestive of epinephrine-induced myocardial infarction. Both these conditions are uncommon and under-recognised, and we review the current literature to compare the similarities and differences in their clinical manifestations, pathophysiology, and management. Kounis syndrome occurs secondary to mast cell degranulation ultimately resulting in coronary vasospasm, platelet activation and inflammatory response, whereas epinephrine causes platelet aggregation. Therefore, treatment priorities of Kounis syndrome are treatment of allergy, treatment of vasospasm, and treatment with anti-platelet therapy and revascularization if coronary plaques are present. For epinephrine-induced myocardial infarction, after epinephrine treatment is discontinued, considerations in management are re-vascularisation or pharmacotherapy. Further research will help with better understanding of both conditions and formulation of clinical management guidelines.

Anaphylactic cardiovascular collapse and Kounis syndrome: systemic vasodilation or coronary vasoconstriction?

The first reported human anaphylactic death is considered to be the Pharaoh Menes death, caused by a wasp sting. Currently, anaphylactic cardiovascular events represent one of most frequent medical emergencies. Rapid diagnosis, prompt and appropriate treatment can be life saving. The main concept beyond anaphylaxis lies to myocardial damage and ventricular dysfunction, thus resulting in cardiovascular collapse. Cardiac output depression due to coronary hypoperfusion from systemic vasodilation, leakage of plasma and volume loss due to increased vascular permeability, as well as reduced venous return, are regarded as the main causes of cardiovascular collapse. Clinical reports and experiments indicate that the human heart, in general, and the coronary arteries, in particular, could be the primary target of the released anaphylactic mediators. Coronary vasoconstriction and thrombosis induced by the released mediators namely histamine, chymase, tryptase, cathepsin D, leukotrienes, thromboxane and platelet activating factor (PAF) can result to further myocardial damage and anaphylaxis associated acute coronary syndrome, the so-called Kounis syndrome. Kounis syndrome with increase of cardiac troponin and other cardiac biomarkers, can progress to heart failure and cardiovascular collapse. In experimental anaphylaxis, cardiac reactions caused by the intracardiac histamine and release of other anaphylactic mediators are followed by secondary cardiovascular reactions, such as cardiac arrhythmias, atrioventricular block, acute myocardial ischemia, decrease in coronary blood flow and cardiac output, cerebral blood flow, left ventricular developed pressure (LVdp/dtmax) as well as increase in portal venous and coronary vascular resistance denoting vascular spasm. Clinically, some patients with anaphylactic myocardial infarction respond satisfactorily to appropriate interventional and medical therapy, while anti-allergic treatment with antihistamines, corticosteroids and fluid replacement might be ineffective. Therefore, differentiating the decrease of cardiac output due to myocardial tissue hypoperfusion from systemic vasodilation and leakage of plasma, from myocardial tissue due to coronary vasoconstriction and thrombosis might be challenging during anaphylactic cardiac collapse. Combined antiallergic, anti-ischemic and antithrombotic treatment seems currently beneficial. Simultaneous measurements of peripheral arterial resistance and coronary blood flow with newer diagnostic techniques including cardiac magnetic resonance imaging (MRI) and myocardial scintigraphy may help elucidating the pathophysiology of anaphylactic cardiovascular collapse, thus rendering treatment more rapid and effective.