Atrioventricular conduction disturbances

Overdose may produce hypotension, somnolence, bradycardia, and atrioventricular conduction disturbances,... 

Rarely, CBZ can cause depression of atrioventricular conduction and ventricular automaticity. This is secondary to the drugs membrane—depressant effects, similar to those of quinidine and procainamide ( 372). Thus, patients with significant, preexisting atrioventricular conduction disturbances should not receive CBZ ( 77). 

Muchir, A., Bonne, G., van der Kooi, A.J., van Meegen, M., Baas, F., Bolhuis, P.A., de Visser, M. and Schwartz, K. (2000) Identification of mutations in the gene encoding lamins A/C in autosomal dominant limb girdle muscular dystrophy with atrioventricular conduction disturbances (LGMDIB). Hum. Mol. Genet. 9, 1453-1459. 

Some patients develop mild transient hypotension after the administration of bolus doses of intravenous magnesium sulfate (2,3). In patients with suspected myocardial infarction who received magnesium sulphate infusions there was an increased incidence of atrioventricular conduction disturbances (9). 

Quinine can cause atrioventricular conduction disturbances. In sensitive patients, such changes can occur with normal dosages given over a prolonged period however, in most cases cardiac effects are due to overdosage. 

Zumoff, B. 1954. Temporary atrioventricular conduction disturbance associated with ingestion of Veratrum viride. Am. Heart. 47(4) 630-633. 

Galanthamine (18) has been of interest, as it has powerful cholinergic activity and is reputed to have analgesic activity comparable to morphine. This alkaloid was used in the former Soviet Union for the treatment of myasthenia gravis, myopathy, and diseases of the nervous system (Cordell, 1981). Galanthamine inhibits cholinesterase, causes bradycardia and atrioventricular conduction disturbances, and has an LD50 i.v. in mouse of 8 mg/kg (Wink, 1993). 

When large amounts are taken, e.g. (unreliably) to induce abortion or in attempted suicide, ocular disturbances, notably constriction of the visual fields, may occur and even complete blindness, the onset of which may be very sudden. Vomiting, abdominal pain and diarrhoea result from local irritation of the gastrointestinal tract. Quinidine-like effects include hypotension, disturbance of atrioventricular conduction and cardiac arrest. Activated charcoal should be given. Supportive measures are employed thereafter as no specific therapy has proven benefit. 

Patients with impaired function of the sinus node or impaired atrioventricular conduction can develop sinus bradycardia, sinus arrest, heart block, hypotension and shock, and even asystole, with verapamil (139) or diltiazem. These drugs should not be given to patients with aberrant conduction pathways associated with broad-complex tachydysrhythmias, and they can cause severe conduction disturbances in hypertrophic cardiomyopathy. 

Conduction disturbances are common with propafenone and can result in sinus bradycardia, sinoatrial block, sinus arrest, any degree of atrioventricular block, and right or left bundle-branch block (SEDA-10,151) (SEDA-15,179). 

An 18-year-old woman took 35 tablets of propafenone, 300 mg each. She had dilated, non-reactive pupils and greatly increased activity of neuron-specific enolase. She had atrioventricular and intraventricular conduction disorders, and repeated resuscitation was necessary. Propafenone was eliminated by plasma exchange, and the conduction disturbances disappeared rapidly during treatment. 

Symptoms of overdose include nausea, vomiting, transient visual or auditory deficits, drowsiness, and seizures followed by severe cardiac arrhythmias, shock, or cardiorespiratory arrest. Hypotension may be severe and intractable, producing metabolic acidosis and end-organ failure. Cardiac conduction disturbances include complete atrioventricular dissociation, QRS and QT prolongation, severe bradycardia, and ventricular fibrillation. Acute ingestions of 30-50 mg kg of chloroquine in adults and as little as 300 mg in children are potentially fatal. 

A. Cardiac disturbances, including hypotension and bradycardia, are the most common manifestations of poisoning. Atrioventricular block, intraventricular conduction disturbances, cardiogenic shock, and asystole may occur with severe overdose, especially with membrane-depressant drugs such as propranolol. The ECG usually shows a normal QRS duration with increased PR intervals QRS widening occurs with massive intoxication. 

Caution if hypersensitivity to other anticonvulsants risk of cross-sensitivity Caution if absence, atonic, or myoclonic seizures may increase generahzed convulsion frequency Caution if increased intraocular pressure may cause exacerbation due to cholinergic antagonism Caution if hepatic or renal impairment Caution if cardiac disease, or cardiac conduction disturbances increased risk of atrioventricular heart block Caution in SLE... 

Ik Conduction of impulses from the atria to the ventricles takes place at the atrioventricular node, which is the most common site for conduction disturbances. 

Cardiovascular system A review discusses chloroquine cardiomyopathy [13 ]. Although a rare occurrence, cardiac toxicity includes conduction disturbances (bxmdle-branch block, atrioventricular block) and cardiomyopathy with hypertrophy, restrictive physiology and congestive heart failure. The review recommends diagnostic procedures. 

Braat SH, de Zwaan C, Bmgada P, et al. Right ventricular involvement with acute inferior wall myocardial inlarction identifies high risk of developing atrioventricular nodal conduction disturbances. Am Heart J 1984 107 1183—1187... 

Normal rhythmic activity is the result of the activity of the sinus node generating action potentials that are conducted via the atria to the atrioventricular node, which delays further conduction to the His-Tawara-Purkinje system. From the Purkinje fibres, action potentials propagate to the ventricular myocardium. Arrhythmia means a disturbance of the normal rhythm either resulting in a faster rhythm (tachycardia, still rhythmic) or faster arrhythmia (tachyarrhythmia) or slowed rhythm (bradycardia, bradyarrhythmia). 

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