Left ventricular diastolic filling pattern at Doppler echocardiography and apoptotic rate in fatal acute myocardial infarction

Sympathetic overstimulation during critical illness: adverse effects of adrenergic stress

The term ''adrenergic'' originates from ''adrenaline'' and describes hormones or drugs whose effects are similar to those of epinephrine. Adrenergic stress is mediated by stimulation of adrenergic receptors and activation of post-receptor pathways. Critical illness is a potent stimulus of the sympathetic nervous system. It is undisputable that the adrenergic-driven ''fight-flight response'' is a physiologically meaningful reaction allowing humans to survive during evolution. However, in critical illness an overshooting stimulation of the sympathetic nervous system may well exceed in time and scope its beneficial effects. Comparable to the overwhelming immune response during sepsis, adrenergic stress in critical illness may get out of control and cause adverse effects. Several organ systems may be affected. The heart seems to be most susceptible to sympathetic overstimulation. Detrimental effects include impaired diastolic function, tachycardia and tachyarrhythmia, myocardial ischemia, stunning, apoptosis and necrosis. Adverse catecholamine effects have been observed in other organs such as the lungs (pulmonary edema, elevated pulmonary arterial pressures), the coagulation (hypercoagulability, thrombus formation), gastrointestinal (hypoperfusion, inhibition of peristalsis), endocrinologic (decreased prolactin, thyroid and growth hormone secretion) and immune systems (immunomodulation, stimulation of bacterial growth), and metabolism (increase in cell energy expenditure, hyperglycemia, catabolism, lipolysis, hyperlactatemia, electrolyte changes), bone marrow (anemia), and skeletal muscles (apoptosis). Potential therapeutic options to reduce excessive adrenergic stress comprise temperature and heart rate control, adequate use of sedative/analgesic drugs, and aiming for reasonable cardiovascular targets, adequate fluid therapy, use of levosimendan, hydrocortisone or supplementary arginine vasopressin.

Right ventricular cardiomyocyte apoptosis in patients with acute myocardial infarction of the left ventricular wall

Cardiac remodeling after acute myocardial infarction (AMI) is characterized by molecular and cellular mechanisms involving both the left (LV) and right ventricular (RV) walls. Cardiomyoycte apoptosis in the peri-infarct and remote LV myocardium has a central role in cardiac remodeling. Whether apoptosis also occurs in the right ventricle of patients with ischemic heart disease has not been investigated. The aim of the present study was to investigate the presence of cardiomyocyte apoptosis in the right ventricle in patients with AMI. We assessed the number of apoptotic cardiomyocytes using multiple samplings in the LV and RV walls of 12 patients selected at autopsy who died 4 to 42 days after AMI. Five patients without cardiac disease were also selected at autopsy as controls. Apoptotic rates were calculated from the number of cardiomyocytes showing double positive staining for in situ end-labeling of DNA fragmentation (TUNEL) and for activated caspase-3. Potentially false-positive results (DNA synthesis and RNA splicing) were excluded from cell counts. The apoptotic rate in the right ventricle in patients with AMI was significantly higher than in control hearts (median 0.8%, interquartile range 0.3 to 1.0 vs median 0.01%, interquartile range 0.01 to 0.03, p <0.001). RV apoptosis significantly correlated with such parameters of global adverse remodeling as cardiac diameter to LV free wall thickness (R = +0.57, p = 0.050). RV apoptosis was significantly higher in five cases (42%) with infarct involving the ventricular septum and an adjacent small area of the RV walls (median 1.0%, interquartile range 0.8 to 2.2 vs median 0.5%, interquartile range 0.2 to 1.0, p = 0.048, p <0.001 vs controls). The association between apoptotic rate in the right ventricle and cardiac remodeling was apparent even after exclusion of cases with RV AMI involvement (R = +0.82, p = 0.023 for diameter to LV wall thickness ratio and R = -0.91, p = 0.002 for RV free wall thickness). In conclusion, patients with cardiac remodeling after AMI had a significant increase in RV apoptosis even when ischemic involvement of the RV wall was not apparent.