**9. Conclusion**

slices during radionuclide study. As for prognosis for restoration of myocardial viability and contractility after CABG in such patients, their criterion { EDTM ≤ 5,5 mm } had high

As a rule, for contrast-enhanced MRI visualization of affected myocardium contrasting agents – paramegnetics are used, usually they are complexes of Gd or Mn with derivatives or analogues of diaethylentriaminpentacetic acid (DTPA). Their intravenous bolus injection makes possible qualitative evaluation of myocardial perfusion by the degree of changing brightness of myocardial image during the first few seconds after injection. Later on, in 12-20 minutes after injection one can evaluate the picture of myocardial lesion by accumula‐

There exist an established and commonly accepted opinion that transmural accumulation of paramagnetics in myocardium during contrast-enhanced MRI means irreversible lesion, and lack of accumulation vice versa evidences viability of myocardium and makes for favoura‐ ble prognosis [32]. Nevertheless, relationship of contrast-enhanced MRI picture with the possibility of arrhythmogenesis in this or that myocardial area is still of a great interest.

Electrophysiological mechanism of the observed interrelationship between results of cardiac contrast-enhanced MRI and decrease of electrical potential in a definite LV segment is noth‐ ing but a particular case of a well-studied pathogenesis of arrhythmias appearance in the

It is in the area of thickened and partially replaced by subendocardial scarred tissue of myo‐ cardium where one can notice lowered electrical potential proportionally to the lowering mass of viable myocardium. This fact, in its turn, is favorable for the functioning of local reentry circuits which are electrophysiological basis for ventricular tachycardias [33, 34].

That is why during contrast-enhanced MRI it makes sense to calculate TI index value in all the cases keeping in mind further electrophysiological study and evaluation of risks for ven‐ tricular tachycardias. Epicardial mapping provides information about the presence of excite‐ ment zones in LV and approximate anatomy of their localization for a further surgical treatment [4, 35]. Preoperative endocardial EPhS with electroanatomical LV reconstruction is able to demonstrate vividly disturbances in cardiac conduction system. Examining the re‐ sults of endocardial EPhS we found consistency of myocardial lesion and its elctrophysio‐ logical properties. In patients suffered from extensive myocardial infarction complicated with aneurysm one can identify zones of low-amplitude ventricular potential less than 0,5mV which is a scarred zone more often anatomically involving an apex of LV with a part of anterior wall and ventricular septum. Viable myocardium has potential amplitude higher than 1,5 mV. A subject of a special interest is a transient zone from 0,5 to 1,5 mV situated between the scar and viable myocardium where they register double potential and/or de‐ layed conduction able to cause re-entry and ventricular tachycardia; a surgeon is just to per‐ form dissection of affected endocardium. EPhS and MRI allow to identify borders for

Postoperative EPhS worth electroanatomical LV reconstruction performed in patients with‐ out endocardectomy showed that re-entry and VT sources revealed preoperatively were still

sensitivity up to 92-95%, but low specificity – just about 56-60%.

tion of contrasting agent in affected areas.

334 Principles and Practice of Cardiothoracic Surgery

area of ischemic myocardial lesion [33].

endocardial dissection.

Thus, data of contrast-enhanced MRI not only have diagnostic significance concerning a de‐ gree of a cardiac muscle lesion but also identify arrhythmogenisisty of this or that myocar‐ dial area. In surgical treatment of postinfarction aneurysm endocardectomy of scarred and transient LV zones' endocardium is an inseparable stage to prevent VT spells. MRI and en‐ docardial EPhS with electroanatomical LV reconstruction allow to find potential areas where re-entry may occur.
