Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0022116 (ischemia)
 91,303 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Possible anti- and proarrhythmic effects of glyburide, an ATP-sensitive K+ channel blocker, were assessed in an isolated tissue model of reperfusion. Transmembrane electrical activity was recorded from endo- and epicardium of isolated segments of guinea pig right ventricular free walls, or two sites on papillary muscles with microelectrodes. An electrocardiogram was recorded by two electrodes placed at opposite ends of the tissue bath. Regular stimulation was delivered to endocardium. Tissues were exposed to simulated ischemia for 15 min and then were reperfused with normal Tyrode's solution. Rapid sustained or nonsustained ventricular tachycardia, bigeminy or trigeminy with characteristics of transmural re-entry occurred early in reperfusion in 50% of free walls. Triggered arrhythmias with characteristics of oscillatory afterpotentials (delayed afterdepolarizations) occurred in 20%. Arrhythmias were accompanied by prolongation of transmural conduction times and abbreviation of endocardial effective refractory periods and action potential durations. Glyburide (3 or 30 microM) significantly attenuated abbreviation of action potential durations and effective refractory periods during ischemic conditions and early reperfusion. Neither endocardial nor transmural conduction times were modified by glyburide; however, glyburide significantly decreased the incidence of transmural conduction block during ischemic conditions. Glyburide abolished reperfusion arrhythmias with characteristics of re-entry, but potentiated oscillatory afterpotentials in papillary muscles and triggered arrhythmias with characteristics of oscillatory afterpotentials in free walls. Identical effects were seen with glyburide present in ischemic solution, or in both ischemic and reperfusion solutions, but no effect was observed with glyburide present only in reperfusion. Our study demonstrates possible cellular mechanisms underlying simultaneous pro- and antiarrhythmic drug effects exerted on late premature beats and rapid arrhythmias and closely coupled premature beats.
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PMID:Differential effects of glyburide on premature beats and ventricular tachycardia in an isolated tissue model of ischemia and reperfusion. 138 28

Electrophysiological effects of allopurinol on arrhythmias were studied in isolated segments of guinea pig right ventricular free walls paced from endocardium. A high-gain electrocardiogram as well as transmembrane electrical activity from endo- and epicardium were recorded. Tissues were exposed to simulated ischemia for 15 min and then were reperfused with normal Tyrode solution. Sustained or nonsustained ventricular tachycardia, bigeminy, and trigeminy with characteristics of transmural reentry occurred in early reperfusion in 75% of 20 control preparations. Arrhythmias were associated with prolongation of transmural conduction time and abbreviation of endocardial effective refractory period (ERP). Allopurinol strongly reduced the incidence of reperfusion arrhythmias (20-33%) between 10 and 100 microM, whereas either lower or higher concentrations (5 or 500 microM) were less effective (43 and 50%). Antiarrhythmic efficacy correlated with significant attenuation of reperfusion-induced transmural conduction delay (P less than 0.05 or 0.01). Allopurinol did not affect endocardial conduction times nor did it significantly alter endocardial action potential duration or ERP. Our results indicate that allopurinol exerts antiarrhythmic efficacy during reperfusion by selectively attenuating defects related to anisotropic tissue properties.
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PMID:Effects of allopurinol on reperfusion arrhythmias in isolated ventricles. 151 Jan 30

The association between ventricular ectopic activity (VEA) and ischemic episodes during everyday activities was investigated in ambulatory patients with stable angina pectoris. Seventy-five consecutive patients with proven coronary artery disease, ischemic episodes on Holter monitoring and positive treadmill tests, but without known ventricular arrhythmias, were prospectively studied. In these 75 patients, a total of 719 ischemic episodes were recorded during 127 twenty-four-hour monitoring periods. Forty-three patients had either no or only very low baseline VEA (less than 14 ventricular premature complexes [VPCs]/24 hours); none of these patients had increased VEA during any ischemic episode. However, among 32 patients who had greater than or equal to 14 VPCs/24 hours (average 243 VPCs/24 hours), increased VEA during ischemic episodes was observed in 11 (31%). These 11 patients had a total of 174 ischemic episodes and the increased VEA appeared in 47 (27%) of the episodes. During 40 of the ischemic episodes the number of single VPCs increased significantly compared to the baseline background VEA: during 4 episodes trigeminy appeared and during another 3 bigeminy was observed. More complex VEA was not observed. Among the 11 patients with increased VEA, only 4 developed VPCs during treadmill testing. No correlation was found between the severity of the ischemic episodes (degree of ST depression and duration of ischemia) and the increased VEA. In 83% of these episodes the increased VEA appeared during the last (possibly reperfusion) phase. No correlation was found between the appearance of ventricular arrhythmias during ischemic episodes and the presence or absence of chest pain at the same time.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Ventricular ectopic activity during myocardial ischemic episodes in ambulatory patients. 224 81

Transmembrane electrical activity was recorded from endo- and epicardium of isolated segments of guinea pig right ventricles with standard microelectrode techniques. An ECG was also recorded by two electrodes placed at opposite ends of the tissue bath. Regular stimulation was delivered to the endocardium. Tissues were exposed to simulated ischemia for 15 min and then were reperfused with "normal" Tyrode's solution. Rapid sustained or nonsustained ventricular tachycardia, bigeminy or trigeminy with characteristics of transmural reentry occurred in early reperfusion in 14 of 20 hearts (70%). Arrhythmias were accompanied by prolongation of transmural conduction time and abbreviation of endocardial effective refractory period. With lidocaine, at 1, 5, 10 and 50 microM, reperfusion arrhythmias occurred in 53.3, 22.2, 20.8 and 14.3% of hearts, respectively. The decreased incidence of arrhythmias was statistically significant for 5 to 50 microM lidocaine (P less than .01). The antiarrhythmic effect did not correlate with changes in transmural conduction time, endocardial effective refractory period, or endocardial excitability. However, antiarrhythmic concentrations of lidocaine selectively depressed epicardial excitability and significantly increased endo- to epicardial conduction block during late ischemic and early reperfusion periods. Epicardial inexcitability extended to late diastole and conduction block was not restricted to premature beats. Thus, in transmural reentry in which the epicardium is an essential component of the circuit, lidocaine may interrupt the circuit by selectively rendering this component inexcitable.
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PMID:Effects of lidocaine on reperfusion arrhythmias and electrophysiological properties in an isolated ventricular muscle model of ischemia and reperfusion. 204 29

Twenty-five normotensive subjects (14 men, 11 women) aged from 25 to 60 years (mean 36) and 30 untreated patients with mild hypertension (stages 1 and 2, JNC V) without target organ damage (16 men, 14 women), aged 26-59 years (mean 35.8) underwent continuous 24-hour ECG Holter monitoring with a Fukuda Denshi SM-40 ambulatory recorder and SCM-400 ECG analyzer. During 24-hour ambulatory ECG recording, mean heart rate was slightly but not significantly higher in hypertensive patients (73.3 +/- 10 beats per minute [bpm]) in comparison with normotensive subjects (71.2 +/- 12 bpm). The prevalence of premature atrial contractions was similar in the two groups. Total ventricular arrhythmias were more prevalent in the group of mild hypertensive patients (P < 0.05), who also had a higher prevalence in complex forms of ectopy (r = 0.81 for bigeminy; r = 0.83 for trigeminy; r = 0.83 for couplets). Holter recordings did not show abnormalities of ST-T wave or episodes of silent ischemia.
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PMID:Ventricular arrhythmias in normotensive subjects and in mild hypertensive patients. 948 9