Ventricular tachycardia verapamil

Verapamil IV- Do not administer concomitantly with IV -adrenergic blocking agents (within a few hours), because both may depress myocardial contractility and AV conduction ventricular tachycardia (VT), because use in patients with wide-complex VT (QRS 0.12 seconds or more) can result in marked hemodynamic deterioration and ventricular fibrillation atrial fibrillation or atrial flutter associated with an accessory bypass tract. 

Verapamil is useful for slowing the ventricular response to atrial tachyarrhythmias, such as atrial flutter and fibrillation. Verapamil is also effective in arrhythmias supported by enhanced automaticity, such as ectopic atrial tachycardia and idiopathic left ventricular tachycardia. 

Verapamil s cardiotoxic effects are dose-related and usually avoidable. A common error has been to administer intravenous verapamil to a patient with ventricular tachycardia misdiagnosed as supraventricular tachycardia. In this setting, hypotension and ventricular fibrillation can occur. Verapamil s negative inotropic effects may limit its clinical usefulness in diseased hearts (see Chapter 12). 

Supraventricular tachycardia is the major arrhythmia indication for verapamil. Adenosine or verapamil are preferred over older treatments (propranolol, digoxin, edrophonium, vasoconstrictor agents, and cardioversion) for termination. Verapamil can also reduce the ventricular rate in atrial fibrillation and flutter. It only rarely converts atrial flutter and fibrillation to sinus rhythm. Verapamil is occasionally useful in ventricular arrhythmias. However, intravenous verapamil in a patient with sustained ventricular tachycardia can cause hemodynamic collapse. 

Make a firm diagnosis. A firm arrhythmia diagnosis should be established. For example, the misuse of verapamil in patients with ventricular tachycardia mistakenly diagnosed as supraventricular tachycardia can lead to catastrophic hypotension and cardiac arrest. As increasingly sophisticated methods to characterize underlying arrhythmia mechanisms become available and are validated, it may be possible to direct certain drugs toward specific arrhythmia mechanisms. 

As noted above, the antiarrhythmic drugs can modify impulse generation and conduction. More than a dozen such drugs that are potentially useful in treating arrhythmias are currently available. However, only a limited number of these agents are clinically beneficial in the treatment of selected arrhythmias. For example, the acute termination of ventricular tachycardia by lidocaine or supraventricular tachycardia by adenosine or verapamil are examples in which antiarrhythmic therapy results in decreased morbidity. In contrast, many of the antiarrhythmic agents are now known to have lethal proarrhythmic actions, that is, to cause arrhythmias. 

A 34-year-old man developed palpitation, shortness of breath, and chest pain. He had smoked a quarter to a half an ounce of marijuana per week and had taken it 3 hours before the incident. He had ventricular tachycardia at a rate of 200/minute with a right bundle branch block pattern. Electrical cardioversion restored sinus rhythm. Angiography showed a significant reduction in left anterior descending coronary artery flow rate, which was normalized by intra-arterial verapamil 200 micrograms. 

DISOPYRAMIDE CALCIUM CHANNEL BLOCKERS Risk of myocardial depression and asystole when disopyramide is co administered with verapamil, particularly in the presence of heart failure Disopyramide is a myocardial depressant like verapamil and can cause ventricular tachycardia, ventricular fibrillation or torsades de pointes Avoid co administering verapamil with disopyramide if possible. If single-agent therapy is ineffective, monitor PR, BP and ECG closely watch for heart failure... 

A 54-year-old man with hjrpertrophic cardiomyopathy, for which he took verapamil, felt unwell after a single tablet of sildenafil (10). Holter monitoring after repeat sildenafil showed an increase in ventricular extra beats and episodes of non-sustained ventricular tachycardia. On echocardiography, left ventricular dimensions were reduced and the subaortic gradient was markedly increased. 

In a recent study intravenous verapamil (4), an agent which inhibits transmembrane influx of calcium, effectively suppressed supraventricular tachycardias but proved much less beneficial in ventricular tachycardias.15... 

Verapamil (80 mg p.o. q. 6 to 8 hours) is indicated in the management of Prinzmetal s or variant angina or unstable or chronic, stable angina pectoris verapamil (0.075 to 0.15 mg/kg rv pnsh over a 2-minnte period) is indicated in the treatment of supraventricnlar tachyarrhythmias verapamil (240 to 480 mg p.o. daily) is indicated in the prevention of recurrent paroxysmal supraventricular tachycardia verapamil (240 to 320 mg p.o. daily) is indicated in the control of the ventricular rate in digitalized patients with chronic atrial flatter and/or fibrillation and verapamil (80 mg p.o. t.i.d.) is indicated in the management of hypertension. 

Another important indication for antiarrhythmic therapy is to reduce ventricular rate in atrial flutter or fibrillation. Rare forms of ventricular tachycardia appear to be DAD-mediated and respond to verapamil. Parenteral verapamil and diltiazem are approved for rapid conversion of PSVTs to sinus rhythm and for temporary control of rapid ventricular rate in atrial flutter or fibrillation. Oral verapamil may be used in conjunction with digoxin to control ventricular rate in chronic atrial flutter or fibrillation and for prophylaxis of repetitive PSVT Unlike adrenergic receptor antagonists, Ca + channel blockers have not been shown to reduce mortality after myocardial infarction. 

Toxicity of Ca Channel Blockers The major adverse effect of intravenous verapamil or diltiazem is hypotension, particularly with bolus administration. This is a particular problem if the drugs are used mistakenly in patients with ventricular tachycardia misdiagnosed as AV nodal reentrant tachycardia. Hypotension also is frequent in patients receiving other vasodilators, including quinidine, and in patients with underlying left ventricular dysfunction, which the drugs can exacerbate. Severe sinus bradycardia or AV block also occurs, especially in patients also receiving P blockers. With oral therapy, these adverse effects tend to be less severe. 

The answer is e. (Hardman, pp 858-874.) Because verapamil, a Ca channel blocker, has a selective depressing action on AV nodal tissue, it is an ideal drug for both immediate and prophylactic therapy of supraventricular tachycardia (SVT). Nifedipine, another Ca channel blocker, has little effect on SAT Lidocaine and adenosine are parenteral drugs with short ha If-lives and, thus, are not suitable for prophylactic therapy. Procainamide is more suitable for ventricular arrhythmias and has the potential for serious adverse reactions with long-term use. 

Indications. Verapamil is used as an antiarrhythmic drug in supraventricular tachyarrhythmias. In atrial flutter or fibrillation, it is effective in reducing ventricular rate by virtue of inhibiting AV-conduction. Verapamil is also employed in the prophylaxis of angina pectoris attacks (p. 308) and the treatment of hypertension (p. 312). Adverse effects Because of verapamil s effects on the sinus node, a drop in blood pressure fails to evoke a reflex tachycardia Heart rate hardly changes bradycardia may even develop. AV-block and myocardial insufficiency can occur. Patients frequently complain of constipation. 

Verapamil Severe left ventricular dysfunction cardiogenic shock and severe CHF, unless secondary to a supraventricular tachycardia amenable to verapamil therapy and in patients with atrial flutter or atrial fibrillation and an accessory bypass tract. 

Therapeutic uses Verapamil and diltiazem are more effective against atrial than ventricular dysrhythmias. They are useful in treating reentrant supraventricular tachycardia and reducing ventricular rate in atrial flutter and fibrillation. In addition, these drugs are used to treat hypertension (see p. 187) and angina (see p. 177). 

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