alternan and Myocardial-Ischemia

This study investigates the development of the spatiotemporal pattern of action potential alternans during acute regional ischemia. Experiments were carried out in isolated Langendorff-perfused rabbit heart using a combination of optical mapping and microelectrode recordings. The alternans pattern significantly changed over time and had a biphasic character reaching maximum at 6-9 min after occlusion. Phase I (3-11 minutes of ischemia) is characterized by rapid increase in the alternans magnitude and expansion of the alternans territory. Phase I is followed by gradual decline of alternans (Phase II) in both magnitude and territory. During both phases we observed significant beat-to-beat variations of the optical action potential amplitude (OAPA) alternans. Simultaneous microelectrode recordings from subepicardial and subendocardial layers showed that OAPA alternans coincided with intramural 2 : 1 conduction blocks. Our findings are consistent with the modeling studies predicting that during acute regional ischemia alternans can be driven by 2 : 1 conduction blocks in the ischemic region.

Topics: Action Potentials; Animals; Glucans; Isolated Heart Preparation; Myocardial Ischemia; Rabbits; Voltage-Sensitive Dye Imaging

Several studies have demonstrated that oral intake of n-3 polyunsaturated fatty acids, specifically eicosapentaenoic acid (EPA), prevents ventricular tachyarrhythmias (VT) with ischemic heart disease, but the underlying mechanisms still remain unclear. Thus, we examined the relation between the serum EPA/arachidonic acid (AA) ratio and electrophysiological properties in patients with ischemic heart disease. The study subjects consisted of 57 patients (46 males, mean age, 66 ± 13 years) with ischemic heart disease. T-wave alternans (TWA) and heart rate variability were assessed by 24hour Holter ECG, and left ventricular ejection fraction (LVEF) was determined by echocardiography. Fasting blood samples were collected, and the serum EPA/AA ratio was determined. Based on a median value of the serum EPA/AA ratio, all subjects were divided into two groups: serum EPA/AA ratio below 0.33 (Group-L, n = 28) or not (Group-H, n = 29). We compared these parameters between the two groups. LVEF was not different between the two groups. The maximum value of TWA was significantly higher in Group-L than in Group-H (69.5 ± 22.8 μV versus 48.7 ± 12.0 μV, P = 0.007). In addition, VT defined as above 3 beats was observed in 7 cases (25%) in Group-L, but there were no cases of VT in Group-H (P = 0.004). However, low-frequency (LF) component, high-frequency (HF) component, LF to HF ratio, and standard deviation of all R-R intervals were not different between the two groups. These results suggest that a low EPA/AA ratio may induce cardiac electrical instability, but not autonomic nervous imbalance, associated with VT in patients with ischemic heart disease.

Topics: Aged; Arachidonic Acid; Eicosapentaenoic Acid; Electrocardiography, Ambulatory; Electrophysiologic Techniques, Cardiac; Electrophysiological Phenomena; Female; Glucans; Humans; Japan; Male; Middle Aged; Myocardial Ischemia; Predictive Value of Tests; Risk Assessment; Risk Factors; Statistics as Topic; Tachycardia, Ventricular