Ventricular extrasystole

QuinidJne. Quinidine, an alkaloid obtained from cinchona bark (Sinchona sp.), is the dextrorotatory stereoisomer of quinine [130-95-0] (see Alkaloids). The first use of quinidine for the treatment of atrial fibrillation was reported in 1918 (12). The sulfate, gluconate, and polygalacturonate salts are used in clinical practice. The dmg is given mainly by the oral (po) route, rarely by the intravenous (iv) route of adniinistration. It is the most frequentiy prescribed po antiarrhythmic agent in the United States. The clinical uses of quinidine include suppression of atrial and ventricular extrasystoles and serious ventricular arrhythmias (1 3). 

Ventricular extrasystoles are treated only if they may degenerate into life-threatening arrhythmia. In milder forms the proarrhythmic risk of the diugs overshadows their benefits. In such cases (3-adrenoceptor antagonists may be attempted. For the treatment of ventricular extrasystoles, such as series or runs of extrasystoles, amiodarone or sotalol are used. In the absence of structural heart disease, class I anti-arrhythmic diugs can be considered an alternative. However, they may not be administered during the post-infarction period. 

Ivabradine is used in the treatment of angina in patients in normal sinus rhythm. It acts on the sinus node resulting in a reduction of the heart rate. It is contraindicated in severe bradycardia (heart rate lower than 60 beats/ minute), cardiogenic shock, acute myocardial infarction, moderate-to-severe heart failure, immediately after a cerebrovascular accident, second and third-degree heart block and patients with unstable angina or a pacemaker. Side-effects include bradycardia, first-degree heart block, ventricular extrasystoles, headache, dizziness and visual disturbances, including blurred vision. 

Signs of intoxication are (1) cardiac arrhythmias, which under certain circumstances are life-threatening, e.g., sinus bradycardia, AV-block, ventricular extrasystoles, ventricular fibrillation (ECG) (2) CNS disturbances — altered color vision (xanthopsia), agitation, confusion, nightmares, hallucinations (3) gastrointestinal — anorexia, nausea, vomiting, diarrhea (4) renal — loss of electrolytes and water, which must be differentiated from mobilization of accumulated edema fluid that occurs with therapeutic dosage. 

Impulses originating at loci outside the sinus node are seen in supraventricular or ventricular extrasystoles, tachycardia, atrial or ventricular flutter, and fibrillation. In these forms of rhythm disorders, antiarrhythmics of the local anesthet-Ltillmann, Color Atlas of Pharmacology... 

Lidocaine is the most widely used local anesthetic. Its excellent therapeutic activity is fast-acting and lasts sufficiently long to make it suitable for practically any clinical use. It stabilizes cell membranes, blocks sodium channels, facilitates the secretion of potassium ions out of the cell, and speeds up the repolarization process in the cell membrane. It is used for terminal infiltration, block, epidural, and spinal anesthesia during operational interventions in dentistry, otolaryngology, obstetrics, and gynecology. It is also used for premature ventricular extrasystole and tachycardia, especially in the acute phase of cardiac infarction. Synonyms for this drug are xylocaine, neflurane, and many others. 

Like procainamide, lidocaine is an amide with local anesthetizing action. Lidocaine is usually administered intravenously for short-term therapy of ventricular extrasystole, tachycardia, especially in the severe phase of myocardial infarction, arrhythmia of natural cause, and for arrhythmia that can originate in the heart during surgical manipulations. Synonyms of this drug are lidopen, xylocaine, xylocard, and others. 

Mexiletine is used for ventricular extrasystole and ventricular tachycardia, and ventricular fibrillation (including during the severe period of myocardial infarction). A synonym of this drug is mexitil. 

Torsades de pointes Procainamide may aggravate this special type of ventricular extrasystole or tachycardia instead of suppressing it. 

Cardiovascular Effects. A woman who swallowed 500-750 ml of a concentrated cresol mixture exhibited tachycardia with polymorphic ventricular extrasystoles shortly after exposure (Labram and Gervais 1968). This was followed within 26 hours by ventricular fibrillation and cardiac arrest. 

Clinically, tachyarrhythmias associated with digitalis excess (including supraventricular and ventricular extrasystoles) and ventricular tachycardia have been suppressed by propranolol. Although propranolol is highly effective in the treatment of digitalis-induced arrhythmias, phenytoin and Udocaine are preferred. 

Ventricular extrasystoles (5.1%), ventricular tachycardia (4.9%), headache (3.6%), hypotension, orthostatic hypotension (2%)... 

Overdose may induce ventricular extrasystoles and short paroxysms of ventricular tachycardia, a sensation of fullness in the head, and tingling of the extremities. Should an excessive elevation of blood pressure occur, it may be immediately relieved by an a-adrenergic blocking agent, e.g., phentolamine. 

Headache (slight) Voiding difficulty Diarrhea Stomach ache Nausea Ventricular extrasystoles Anxiety, agitation, vomiting... 

A variety of cardiac arrhythmias have been described in patients receiving levodopa, including tachycardia, ventricular extrasystoles and, rarely, atrial fibrillation. This effect has been attributed to increased catecholamine formation peripherally. The incidence of such arrhythmias is low, even in the presence of established cardiac disease, and may be reduced still further if the levodopa is taken in combination with a peripheral decarboxylase inhibitor. 

On the other hand, a number of studies have shown that morphine and opioid peptides could have cardioprotective effects toward ischemic processes and may be able to reduce the size of infarct [72,73]. These effects seem to involve the activation of delta opioid receptors, the localization of which remains unknown. In addition, enkephalin-degrading enzyme inhibitors, such as acetorphan and, particularly, RB 101, have also been demonstrated to decrease the susceptibility to the arrhythmogenic action of epinephrine. Thus RB 101 completely prevented the ventricular tachycardia, fibrillation, and repetitive ventricular extrasystoles induced by epinephrine (Maslov et al., unpublished data). These effects were reversed by the selective delta antagonist ICI 174,864. 

Cardiac arrhythmias, which under certain circumstances are life-threatening, e.g., sinus bradycardia, AV-block, ventricular extrasystoles, ventricular fibrillation (ECG) ... 

Halothane has the highest blood/gas partition coefficient of the volatile anaesthetic agents and recovery from halothane anaesthesia is comparatively slow. It is pleasant to breathe and is second choice to sevoflurane for inhalational induction of anaesthesia. Halothane reduces cardiac output more than any of the other volatile anaesthetics. It sensitises the heart to the arrhythmic effects of catecholamines and hypercapnia arrhythmias are common, in particular atrioventricular dissociation, nodal rhythm and ventricular extrasystoles. Halothane can trigger malignant hyperthermia in those who are genetically predisposed (see p. 363). 

Arrhythmia can evolve rapidly within a few seconds, benign supraventricular arrhythmias can turn into other types of rhythm disorders, such as nodal tachycardia, atrial fibrillation and multiple ventricular extrasystoles, in doublets or triplets. It is important to act quickly - which is easy as everything that is needed to deal with these arrhythmias (fortunately very rare) is ready to hand and the patient is on a drip. 

Ajmaline is used clinically in supraventricular and ventricular tachycardia and (mostly the ventricular) extrasystole. 

Bigeminy An arrhythmia consisting of normal sinus beats coupled with ventricular extrasystoles, ie, twinned beats ... 

Procainamide is a class I anti-arrhythmic agent with actions similar to those of quinidine. It depresses myocardial automaticity and excitability and increases the effective refractory period of the atrium. It finds its application towards the suppression of ventricular extrasystoles and paroxysmal ventricular tachycardia. It is also useful in the control and management ofatrialfibrillation and premature atrial contractions. 

B. Tachycardia is a common refiex response to vasodilation and may also be caused by direct stimuiation of beta-1 receptors as beta-2 selectivity is lost in high doses. Supraventricuiar tachycardia or ventricular extrasystoles are occasionally reported. 

Ventricular extrasystole was observed in rabbits after oral administration of 20 mg/kg vincamine (EMEA 1999). 

Effects on human health reflecting neurological, cardiovascular, or gastrointestinal symptoms can be observed either if lupin seeds are eaten unripe or not debittered. Symptoms of intoxication after ingestion of lupin seeds with high alkaloids content appear 1-14 h after consumption and include dry mouth, muscular weakness, disturbed balance, sweating, palpitation, blurred vision, mydriasis (i.e., dilated pupils), urine retention, gastric and intestinal troubles, and abtmdant ventricular extrasystoles [45]. 

Cardiotoxicity and nephrotoxicity have occurred in patients having phenol chemical peels [328,338]. In a study of 181 patients undergoing a phenol chemical peel with no more than 3 mL applied, 12 developed cardiac dysrhythmias [338]. These dysrhythmias consisted of a few ventricular extrasystoles in 9 patients, bigeminy in 1 patient, and polytropic extrasystoles in 2 patients. In 4 of these 12 patients, the dysrhythmia was self-limited (resolved spontaneously) and in the other 8 patients treatment with 100 mg of intravenous lidocaine controlled the dysrhythmias. No patients developed hanodynamic instability [338]. 

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