sodium-nitrite and Arrhythmias--Cardiac

It has previously been proved that sodium nitrite, infused prior to coronary artery occlusion or before reperfusion, results in marked antiarrhythmic effect in anaesthetized dogs. We have now examined whether this protection involves the modulation of gap junction (GJ) function by nitric oxide (NO), derived from nitrite administration under ischaemic conditions. Two groups of chloralose and urethane anaesthetized dogs, each containing 13 animals, were subjected to a 25 min period occlusion of the left anterior descending (LAD) coronary artery, followed by reperfusion. One group was infused with sodium nitrite (0.2 μmol/kg/min, i.v.), the other group with saline 10 min prior to reperfusion. The severities of arrhythmias and of ischaemia (epicardial ST-segment, total activation time), parallel with changes in myocardial tissue impedance, a measure of electrical coupling of gap junctions, were assessed during the experiments. Compared to the controls, nitrite infusion administered prior to reperfusion significantly attenuated the severity of ischaemia, the ischaemia-induced impedance changes and, consequently, the severity of arrhythmias, occurring during the 1B phase of the occlusion, and increase survival following reperfusion (0% vs. 85%). It is concluded that the marked antiarrhythmic effect of sodium nitrite is partly due, to the preservation of the electrical coupling of GJs by NO.

Topics: Analysis of Variance; Anesthesia; Animals; Arrhythmias, Cardiac; Dogs; Electric Impedance; Female; Gap Junctions; Hemodynamics; Infusions, Intravenous; Male; Myocardial Reperfusion Injury; Pericardium; Severity of Illness Index; Sodium Nitrite; Time Factors

This study aimed to examine whether inducible nitric oxide synthase (iNOS) plays a role in the delayed antiarrhythmic effect of sodium nitrite. Twenty-one dogs were infused intravenously with sodium nitrite (0.2 μmol·kg

Topics: Animals; Anti-Arrhythmia Agents; Arrhythmias, Cardiac; beta-Aminoethyl Isothiourea; Dogs; Hemodynamics; Ischemic Preconditioning, Myocardial; Myocardial Reperfusion Injury; Nitric Oxide; Nitric Oxide Synthase Type II; Sodium Nitrite; Tachycardia, Ventricular

Ventricular arrhythmias induced by ischemic heart disease are the main cause of sudden cardiac death. Ischemia can cause life-threatening arrhythmias by modulating connexin 43 (Cx43), a principal cardiac gap junction channel protein. The present study investigates whether nitrite can attenuate ischemia-induced ventricular arrhythmias and dephosphorylation of Cx43 in a rat model.. Rats were medicated with normal saline (control, n = 10), nitrite (0.015, 0.15, and 1.5 mg/kg, n = 9 or 10 each), and 0.15 mg/kg nitrite with either the nitric oxide scavenger 2-(4-carboxyphenyl)-4, 4, 5, 5-tetramethylimidazoline-1-oxyl-3-oxide, sodium salt (cPTIO; n = 9) or allopurinol (xanthine oxidoreductase inhibitor, n = 9). We determined the severity of ventricular arrhythmias based on arrhythmia scores and levels of phosphorylated Cx43.. The median arrhythmia score may have been lower in the group given 0.15 mg/kg nitrite (4 [interquartile range {IQR}, 4-5]) than that in the control group (7.5 [IQR, 5.25-8]; P = 0.013). There was no difference among the control, the given 0.015 mg/kg nitrite (7 [IQR, 5-8]), and 1.5 mg/kg nitrite (7 [IQR, 5.5-7.75]; P = 0.95). The arrhythmia scores in the cPTIO (6 [IQR, 5-8]; P = 0.030) and allopurinol (7 [IQR, 5-8]; P = 0.005) groups may have been higher than that in 0.15 mg/kg nitrite group. Immunoblotting revealed that the level of phosphorylated Cx43 in the group given 0.15 mg/kg nitrite, but not in the other treated groups, was significantly higher compared with the control group (P = 0.007).. Nitrite may have attenuated acute ischemia-induced ventricular arrhythmias and Cx43 dephosphorylation in rats. Nitric oxide, which might be generated by xanthine oxidoreductase via nitrite reduction, appears to play a crucial role in this antiarrhythmic effect.

Topics: Allopurinol; Animals; Arrhythmias, Cardiac; Blood Gas Analysis; Connexin 43; Cyclic N-Oxides; Dose-Response Relationship, Drug; Enzyme Inhibitors; Free Radical Scavengers; Hemodynamics; Imidazoles; Male; Myocardial Ischemia; Nitric Oxide; Phosphorylation; Rats; Rats, Wistar; Sodium Nitrite; Ventricular Dysfunction

To provide evidence for the protective role of inorganic nitrite against acute ischaemia and reperfusion-induced ventricular arrhythmias in a large animal model.. Dogs, anaesthetized with chloralose and urethane, were administered intravenously with sodium nitrite (0.2 µmol kg(-1) min(-1)) in two protocols. In protocol 1 nitrite was infused 10 min prior to and during a 25 min occlusion of the left anterior descending (LAD) coronary artery (NaNO2-PO; n = 14), whereas in protocol 2 the infusion was started 10 min prior to reperfusion of the occluded vessel (NaNO2-PR; n = 12). Control dogs (n = 15) were infused with saline and subjected to the same period of ischaemia and reperfusion. Severities of ischaemia and ventricular arrhythmias, as well as changes in plasma nitrate/nitrite (NOx) levels in the coronary sinus blood, were assessed throughout the experiment. Myocardial superoxide and nitrotyrosine (NT) levels were determined during reperfusion. Changes in protein S-nitrosylation (SNO) and S-glutathionylation were also examined.. Compared with controls, sodium nitrite administered either pre-occlusion or pre-reperfusion markedly suppressed the number and severity of ventricular arrhythmias during occlusion and increased survival (0% vs. 50 and 92%) upon reperfusion. There were also significant decreases in superoxide and NT levels in the nitrite treated dogs. Compared with controls, increased SNO was found only in NaNO2-PR dogs, whereas S-glutathionylation occurred primarily in NaNO2-PO dogs.. Intravenous infusion of nitrite profoundly reduced the severity of ventricular arrhythmias resulting from acute ischaemia and reperfusion in anaesthetized dogs. This effect, among several others, may result from an NO-mediated reduction in oxidative stress, perhaps through protein SNO and/or S-glutathionylation.

Topics: Administration, Intravenous; Animals; Anti-Arrhythmia Agents; Arrhythmias, Cardiac; Disease Models, Animal; Dogs; Hemodynamics; Myocardial Ischemia; Myocardial Reperfusion Injury; Myocardium; Nitrates; Nitric Oxide; Nitrites; Protein Processing, Post-Translational; Sodium Nitrite; Superoxides; Tyrosine

Sodium azide poisonings occur very rarely. The mechanism of sodium azide toxic effect has not yet been fully explained. Despite the lack of an explicit procedure for the cases of sodium azide poisonings, in vitro tests and rare case reports suggest that treatment with antidotes for cyanide poisoning victims can be effective. This study describes two cases of suicidal sodium azide ingestion. Case 1. 30-year-old male ingested ca. 180 mg of sodium azide. On admission to hospital, within 4 hours from poisoning, the man complained of dizziness and anxiety. Physical examination revealed horizontal nystagmus, flapping tremor, HR 135/min. In laboratory tests, higher blood concentration of lactates (3 mmol/l) was detected, as well as lower potassium concentration (3.4 mmol/L) and increased transaminase activity (ALT 74 U/l, AST 90 U/l). Electrocardiographic tests showed a negative T wave in limb lead III. Other results were within normal. As the patient ingested a toxic dose of sodium azide, he was treated according to the therapy prescription for cyanide poisoning (amyl nitrite inhalation followed by intravenous administration of sodium nitrite and sodium thiosulphate). ECG record of the last day of hospitalization (7th day of treatment) showed negative T waves in lead III, V4-V6. He was discharged from hospital in good condition. Case 2.23-year-old male ingested 10 g of sodium azide 1.5 hours prior to admission to hospital. At the beginning, the patient's condition was good, but it changed to critical state within the first hours of hospitalization. He developed a deep coma, respiratory and circulatory insufficiency, metabolic acidosis, cardiac dysrrhythmias and anuria. Cardiac activity monitoring showed alternating tachycardia (140 beats per minute) and bradycardia (48 beats per minute), numerous additional supraventricular and ventricular extrasystoles and sinus dysrrhythmia. Cardiac arrest (asystolia) occurred twice, the second incident with fatal outcome. The patient received supportive therapy, he was also treated according to the therapy prescription for cyanide poisoning. Circulatory disturbances observed in both cases have been described in literature as symptoms of sodium azide poisoning. However, available literature data are scarce and lack systematization, most of them coming from several decades ago. The lack of patient's consent for detailed examination of circulatory system and liver made it impossible to gather further knowledge on the subject. T

Topics: Adult; Antidotes; Arrhythmias, Cardiac; Bradycardia; Clinical Protocols; Dose-Response Relationship, Drug; Electrocardiography; Fatal Outcome; Heart Arrest; Humans; Hydroxocobalamin; Hypokalemia; Lactates; Male; Monitoring, Physiologic; Nitrates; Pentanols; Poisoning; Sodium Azide; Sodium Nitrite; Suicide, Attempted; Thiosulfates; Transaminases; Treatment Outcome