Myogenic or Thrombogenic Theory?


 Quintiliano H. de Mesquita, M.D.


Different pathophysiological aspects offered by the Thrombogenic and Myogenic theories of the acute myocardial infarction (AMI)"

 A) Thrombogenic Theory (Herrick, 1912): Proclaimed the coronary thrombus as originated from ulceration by rupture of coronary artery plaque causing absolute regional myocardial ischemia coronary-dependent which produces the infarction and myocardial necrosis as final resultant.

 B) Myogenic Theory (Mesquita, 1972): Proclaimed a more complex mechanism where the AMI is developed by functional degradation state of the regional myocardium coronary-dependent, which characterizes the coronary myocardiopathy condition.

 According the myogenic theory the AMI represents the perpetuation of the unstable angina (UA) picture reaching the regional myocardial necrosis as natural evolution. The regional myocardial insufficiency is the critical onset of AMI followed by absolute regional ischemia both responsible for the evolution to myocardial necrosis area with an eventual secondary coronary thrombosis. The natural consequences of acute regional myocardial insufficiency are: induction to the myocardial and circulatory stagnation and invasion of white blood cells and derived products and the absolute regional myocardial ischemia responsible for the development of myocardial infarction and necrosis.

Different, specific and antagonistic therapeutical aspects presented by the Thrombogenic and Myogenic theories for the treatment of AMI in the patho-physiological point of view"

 A) Thrombogenic Theory: Nowadays there is only the thrombolytics like specific therapeutic agents for the AMI with the indication to dissolve the coronary thrombus declared as the primary cause of myocardial infarction. The other tentative realized in the past (1944-1969) with the use of anticoagulant drugs for treatment of AMI was abandoned due to its complete inefficacy.

 B) Myogenic Theory: Claim the use of cardiotonic drugs as specific therapeutics, in order to arrest the myocardial infarctioning clinical process. With the use of cardiotonics the enzymatic peaks show three different possibilities or degrees, during the evolutionary process of AMI:

 1- Interruption of the evolutionary picture

 2- Avoidance of the infarction

 3- Attenuation of the declared myocardial infarction

Some clinical observations which led us to the Myogenic Theory"

A) Absolute inefficacy of anticoagulants and thrombolytics in the treatment of unstable angina pectoris considered as an evolutionary process to the myocardial infarction.

B) Registry of myocardial infarction related with stressing or unusual physical activity.

 C) Frequent coronary-arteriographic and from coronary bypass surgery without obstructive processes, in the presence of myocardial infarction.

 D) Ocurrence of myocardial infarction, recorded in the period from 2-21 days, after an abrupt withdrawal of the beta blockers agents use.

Anatomo-pathological findings where some authors preconized the coronary thrombosis as consequence of AMI and not its cause, reinforcing our ideas about the Myogenic Theory"

A) Large variation of coronary thrombosis taking place in necropsy register (7-91%) with the increasing of frequency dependent about the localization of necrosis and the elapsed time since the onset of symptoms of myocardial ischemia and death.

 B) Coronary thrombosis incorporating fibrinogen marked by the radioactive isotopes I (125) and I (131) administered 10-15 hours after the beginning of the clinical myocardial infarction picture, fact which suggest the coronary thrombosis as consequence of primary myocardial necrosis.

 C) The occurrence of coronary thrombus as a consequence of acute myocardial infarction experimentally provoked by surgical ligature of coronary artery without endothelial lesion.