Arrhythmias bepridil causing

Induction of new serious arrhythmias (bepridil) Bepridil has Class I antiarrhythmic properties and, like other such drugs, can induce new arrhythmias, including VTA/F. In addition, because of its ability to prolong the QT interval, bepridil can cause torsades de pointes-type VT. Because of these properties, reserve for patients in whom other antianginal agents do not offer a satisfactory effect. 

These agents appear to be similar in efficacy to verapamil in the management of supraventricular arrhythmias, including rate control in atrial fibrillation. An intravenous form of diltiazem is available for the latter indication and causes hypotension or bradyarrhythmias relatively infrequently. Bepridil also has action potential- and QT-prolonging actions that theoretically may make it more useful in some ventricular arrhythmias but also create the risk of torsade de pointes. Bepridil is only rarely used, primarily to control refractory angina. 

Ca + CHANNEL BLOCK The major electrophysiological effects resulting from block of cardiac Ca + channels are in slow-response tissues, the sinus and AV nodes. Dihydropyridines such as nifedipine, which are used commonly in angina and hypertension, preferentially block Ca + channels in vascular smooth muscle their cardiac effects, such as heart rate acceleration, result principally from reflex sympathetic activation secondary to peripheral vasodilation. Only verapamil, diltiazem, and bepridil block Ca + channels in cardiac cells at clinically used doses. These drugs generally slow heart rate, although hypotension can cause reflex sympathetic activation and tachycardia. The velocity of AV nodal conduction decreases, so the PR interval increases. AV nodal block occurs as a result of decremental conduction and increased AV nodal refractoriness, which form the basis for the use of channel blockers in reentrant arrhythmias whose circuit involves the AV node, such as AV reentrant tachycardia. 

E. Toxicity The calcium channel blockers cause constipation, edema, nausea, flushing, and dizziness. More serious adverse effects include congestive heart failure, atrioventricular blockade, and sinus node depression these are more common with verapamil than with the dihydropyridines. Bepridil may induce torsade de pointes and other arrhythmias. 

Most calcium antagonists do not affect intraventricular conduction, so the QRS duration is usually unaffected. The PR interval may be prolonged even with therapeutic doses of verapamil. Bepridil prolongs the QT interval and may cause ventricular arrhythmias, including torsade de pointes (see p 14). Mibefradil also causes QT prolongation, and has been associated with ventricular arrhythmias. It has been removed from the US market. 

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