Title : Viable myocardium: Clinical sufficiency and prognostic implication
Abstract:
The estimation of prognosis of the different cardiovascular diseases is still very challenging because of the multifactorial impact in the condition of therapeutic or surgical treatment, their subsequent or simultaneous affect. Ischemic heart disease, as a chronic progressive disease, is complicated by transient nonfatal or fatal damage of myocardium in the majority of cases. Loss of the number of myofibrils leads to loss of heart contractility with the depression of local systolic and diastolic deformation and in patients with transmural or large scar area – loss of local systolic function. Described histologic changes in the area of post ischemic myocardial scar can be visualized by diagnostic ultrasound, cardiac single-photon emission computer tomography (SPECT), magnetic resonance (CMR), cardiac computer tomography (CardiacCT), positron-emission tomography (PET). In this case prognosis is based on the function of damaged myocardium in the rest conditions, not mentioning any provoking factors, which are common in the real life and resulted hemodynamic storm, increasing myocardial wall stress, decreasing of pump function dramatically, worsening follow up and survival.
A study of contractility reserve is advised to be more appropriate diagnostic method in patients with ischemic depressed myocardium to judge a global response to physical or psychoemotional load, and build short and long term prognosis, following the steps of a treatment algorithm. Diagnostic approach to measure myocardial viability using cardiac ultrasound is acceptable in the majority of patients with favorable acoustic window. A diagnosed myocardial viability at low dose dobutamine or low dose dipyridamole echo gives opportunity to perform a left ventricle reconstruction with an optimization of left ventricle end-diastolic volume, following Frank-Starling law. Poor acoustic window doesn’t give to estimate myocardial contractility. In these patients other noninvasive techniques (stress-SPECT, stress-CMR, stress-CardiacCT, stressPET) are used with a modelling of the stress condition by dipyridamole.
A prognostic significance of viable myocardium in patients with ischemic heart disease was assessed in multicenter studies. Nevertheless, an existed criticism of the results of STICH and ISCHEMIA triggered subanalysis in frame of these studies and shows we still need more proves to perform an estimation of myocardial viability routinely using high quality equipment and clinical experience of high grade cardiologists and radiologists.
