Why is verapamil contraindicated in ventricular arrhythmias

TREATMENT AND PROPHYLAXIS OF SUPRAVENTRICULAR ARRHYTHMIA

The prophylaxis and treatment of cardiac arrhythmias have changed in recent years. In the January issue (a-t 2000; 31: 2-4) the focus was on ventricular arrhythmias, now supraventricular arrhythmias follow:

Atrial fibrillation is the most common rhythm disturbance. Around one in ten people over the age of 75 is affected. Acute atrial fibrillation is distinguished from chronic (more than seven days) and paroxysmal. It remains to be examined whether the arrhythmia influences the survival prognosis regardless of the underlying disease. Acute atrial fibrillation often stops within 48 hours, especially with temporary triggers.1,2

Atrial flutter is an unstable condition that sooner or later turns into chronic atrial fibrillation. There are no significant differences in treatment.

Supraventricular extrasystoles do not require any therapy. Beta blockers should only be considered for fearful subjective complaints. In the case of sinus tachycardia, the underlying disease must be treated. Paroxysmal supraventricular tachycardias are rare, but are therapeutically important and include numerous special forms.1-3

Treatment of atrial fibrillation: A decision is made between attempting rhythmization with or without recurrence prophylaxis or simply checking the ventricular frequency. With atrial fibrillation lasting more than six to twelve months, chronic heart failure, inadequately treated arterial high blood pressure or heart valve disease, the chances of success for permanent rhythmization are low. A sick sinus node (sick sinus syndrome), enlarged atrium (over 55 mm) and frequent previous episodes make a sustained rhythmization unlikely. Correctable causes (e.g. infection, hyperthyroidism) are to be treated with priority.

Before attempting rhythmization, if atrial fibrillation has persisted for more than 48 hours, a three-week anticoagulation is required due to the risk of embolic insults (INR 2-3). After a successful intervention, it should be continued for at least four weeks. If there are no complaints and ventricular frequencies below 80 to 100 / min. If rhythm is not used or if this fails, the permanent intake of acetylsalicylic acid (ASA; ASPIRIN, etc., 300 mg / day) or oral anticoagulants is indicated, depending on the risk of insult (cf. a-t 1996; No. 9: 87-8). At high risk (e.g. age over 75 years, heart failure, diabetes, hypertension) an insult can be prevented in one in 33 patients per year with anticoagulation (INR 2-3), with ASA in one in 59 patients.4

To Rhythmization of atrial fibrillation cardiac glycosides are ineffective.5,6 Calcium channel blockers such as verapamil (ISOPTIN, etc.) and diltiazem (DILZEM, etc.) tend to promote the persistence of the arrhythmia. Like digitalis preparations, they pose a risk in (unknown) pre-excitation syndromes such as WOLFF-PARKINSON-WHITE (WPW) syndrome (favoring antegrade conduction, "pseudo-ventricular fibrillation"). Beta blockers including Sotalol (SOTALEX, etc.) are also unsuccessful for rhythmization.2,7-9

Class Ia and Ic antiarrhythmics are effective. In the absence of structural heart disease, class Ic drugs such as flecainide (TAMBOCOR) are particularly suitable for attempting rhythmization (for grouping antiarrhythmic drugs see a-t 2000; 31: 3). In the elderly or with severe cardiac disease, hospitalization for ECG monitoring is advisable because of the frequent proarrhythmic effects.1,8 Flecainide and propafenone (RYTMONORM et al.) Can be administered parenterally (2 mg / kg i.v. each) or orally (300 mg or 600 mg to 900 mg). The success rates are between 50% and 70%, and even higher after injection. Quinidine per os (CHINIDIN-DURILES, among others; 1.5 g to 3 g / day) produces comparable results. As with other class Ia drugs, pretreatment should be with a cardiac glycoside or verapamil because of atropine-like effects (increase in ventricular frequency).1,2,7,9

Amiodarone (CORDAREX et al., 1 g to 2.4 g / day i.v.) with success rates of 80% to 90% is named as the most effective means of rhythmisation.2,10 Amiodarone is said to still work when other antiarrhythmics fail.7,10 Other authors do not see any superiority to Class I funds.8 If, due to unstable hemodynamics or anginal complaints, rapid and reliable rhythmisation is desired, electrical cardioversion is the method of choice (external under short anesthesia or intra-atrial catheter; successes 70% to 90%).2,7,8

In the case of chronic atrial fibrillation, it is often sufficient to simply use the Control ventricular rate. The aim should be frequencies of 80 to 100 / min. At older Cardiac glycosides are the drug of choice for patients with concomitant heart failure. They are also suitable for rapid control of the ventricular rate in the event of unstable hemodynamics. The full effective dose (approx. 1 mg digoxin [LANICOR et al.] Or 1 mg digitoxin [DIGIMERCK et al.]) Can be fractionated over 24 hours. For an optimal effect, long-term serum levels in the upper therapeutic range are necessary. Frequency increases due to increased sympathetic tone, e.g. during physical exertion, cannot be adequately controlled with cardiac glycosides.1,2,5

At younger ones Patients are beta blockers of choice, especially if they have accompanying coronary artery disease or hypertension. With them, stress-related increases in frequency can be well controlled. Dosed gradually, they are also suitable for chronic heart failure. If the ventricular rate is reduced rapidly, the negative inotropy of beta blockers can become clinically relevant in the case of acute cardiac decompensation. A special indication exists for tachycardic atrial fibrillation in the context of hyperthyroidism. As an alternative to beta blockers, for example in the case of contraindications, verapamil can be considered in younger patients. Exercise-related frequency increases also respond well. However, due to negative inotropy, special care should be taken in heart failure. This also applies to diltiazem.2,11,12

If the ventricular rate cannot be controlled by monotherapy, beta blockers are combined with digitalis, in the case of intolerance or contraindications for beta blockers digitalis with verapamil. Combinations of cardiac glycosides and class I antiarrhythmics (such as quinidine, flecainide or propafenone) are also effective in controlling the frequency,1,12 are no longer justifiable, however, because more deaths are described in observational studies with long-term ingestion. The same applies to sotalol and the combination of quinidine plus verapamil (CORDICHIN; a-t 1991; No. 6: 50-1).13

The only drug that remains as a further alternative is digitalis plus amiodarone. Because of the high potential for interfering effects (cf. a-t 2000; 31: 2-4), amiodarone can only rarely be justified for this indication. Invasive procedures such as AV node modulation or ablation by electrocoagulation, possibly with subsequent pacemaker implantation, are often the better alternative.8,11,12

Atrial fibrillation prophylaxis: After rhythmization, the advantages and disadvantages of drug-based relapse prophylaxis must be weighed up. There are all reasons against it that make the rhythm itself more difficult. Long-term success is then unlikely, and disruptive effects from antiarrhythmics are more common, especially threatening arrhythmias. Sinus rhythm, on the other hand, improves left ventricular function and physical performance, and reduces the risk of embolism, progressive atrial enlargement, and cardiomyopathy. Long-term anticoagulation can be avoided. In paroxysmal atrial fibrillation with frequent symptomatic episodes, prophylaxis against recurrence is usually indicated.1,2,14

Without prophylaxis, one year after rhythmization in chronic atrial fibrillation, only every fourth patient is still in sinus rhythm. Beta blockers, verapamil, and diltiazem do not work any better than placebo.1-3 Contrary to common practice, cardiac glycosides are also unsuitable for preventing recurrences. They don't reduce the risk of relapse. In the case of paroxysmal atrial fibrillation, the data are contradictory, prophylactic effects at best marginal. Cardiac glycosides are unable to lower the ventricular rate when relapses occur.1,15

After one year with quinidine or sotalol, a maximum of every second patient is still in sinus rhythm. The success rates among the class Ic antiarrhythmics flecainide and propafenone seem to be 50% to 70% more favorable.9,12,14 For quinidine in particular, but also for the other remedies, indications of excess mortality are increasing despite the stabilization of the sinus rhythm.13,16 In two German studies, quinidine plus verapamil are currently being tested against sotalol or placebo in cases of paroxysmal or after rhythmization of chronic atrial fibrillation.17,18 Even their approach fails, since stabilization of the sinus rhythm and reduction of recurrences are being investigated. However, only valid data on morbidity and mortality are relevant.

For amiodarone, relapse rates of 50% to 80% have been reported for one year.10,12,14 According to a Canadian study, it works better than propafenone or sotalol (sinus rhythm after 16 months in 65% vs. 37%). Side effects are more common with amiodarone, treatment discontinuations due to ineffectiveness are less common. The study does not provide any relevant data on survival rates.19 So far, however, amiodarone has not been associated with an increase in rhythmogenic deaths and does not have a negative inotropic effect. In the case of previous cardiac damage, it could become the method of choice for compelling indications.

The optimal treatment strategy for atrial fibrillation is still being researched. Subjective complaints such as palpitations, dizziness and shortness of breath respond just as well to frequency control (diltiazem) as to rhythmization (cardioversion) and then amiodarone to prevent recurrence. If the frequency control is used alone, interference effects are less common.20 In a US American long-term study (over 5,000 patients, observation time over three years), both approaches are to be compared.21

Paroxysmal supraventricular tachycardia: The actual atrial tachycardias (approx. 15%) and reentry tachycardias with accessory pathways such as the WPW syndrome (approx. 10%) must be distinguished from AV node reentry tachycardias (approx. 75%) caused by circular excitation. Further differentiations require diagnostics in one center. Narrow QRS complexes are characteristic. Broadening reminiscent of ventricular tachycardia also occurs (accessory bundles, conduction blockages). They often occur in younger, otherwise heart-healthy patients. Treatment is often only necessary because of subjectively disturbing symptoms and impaired hemodynamics, less often for prognostic reasons. This forces a particularly critical indication to be given.3,11,22

At Atrial tachycardias Verapamil or beta blockers are suitable for seizure treatment, possibly combined with digitalis. Often the ventricular rate can be reduced without immediately restoring the sinus rhythm. In the case of special forms, the intravenous injection of adenosine (ADREKAR and others; ectopic stimulus center) or magnesium (CORMAGNESIN and others; multifocal stimulation) may be indicated. Relapse can rarely be effectively prevented with beta blockers or verapamil. Class Ia or Ic antiarrhythmics or amiodarone work better, but can only be justified in exceptional cases for long-term prophylaxis.3,11,22

AV nodal reentry tachycardias can often be suppressed by vagus maneuvers (carotid pressure, drinking cold water, coughing or pressing). Verapamil or adenosine (ADREKAR, etc.) are primarily considered medication. The ultra-short acting adenosine initially brings more. However, early recurrences are more common. The success rates are the same as for verapamil. Both adenosine (flush, bronchospasm, threatening ventricular arrhythmias) and verapamil (persistent bradycardia, drop in blood pressure) can lead to serious disruptive effects. Which means is best suited is controversially judged. In children and patients with heart failure, hypotension and prior treatment with beta blockers, adenosine is preferred. If atrial fibrillation or flutter or QT syndromes cannot be excluded, it is contraindicated.3,11,23

To prevent recurrence, an attempt with a beta blocker, verapamil or digitalis is indicated. If the treatment is unsuccessful and there is a compelling indication for treatment, a decision must be made between catheter ablation (high-frequency coagulation) or permanent antiarrhythmic therapy (class Ia or Ic antiarrhythmics, amiodarone).3,11,24

Also at Reentry tachycardias with an accessory pathway Vagus maneuvers are suitable for treating seizures. Verapamil, cardiac glycosides, and adenosine are contraindicated. They can trigger ventricular tachycardias and fibrillation. Ajmaline i.v. (GILURYTMAL et al.) Or a class Ic antiarrhythmic drug in question. Beta blockers are the means of choice for prophylaxis. In the case of resistance to therapy, the differential indication between catheter ablation procedures and long-term therapy with antiarrhythmics (class Ic, amiodarone) should be made in the case of severe disease.3,11,24

CONCLUSION: Optimal strategies for treating atrial fibrillation and its consequences are still being tested. If there is an increased risk of cerebral ischemic insults, the intake of acetylsalicylic acid (ASA; ASPIRIN, etc.) or oral anticoagulants is usually indicated (a-t 1996; No. 9: 87-8). Cardiac glycosides are used to control the ventricular rate in the elderly, beta blockers and verapamil (ISOPTIN, etc.) for younger people, possibly combined with a cardiac glycoside. Class Ic remedies are currently preferred for rhythmization. Amiodarone (CORDAREX etc.) remains in reserve. In the prevention of recurrence, all class I agents carry the risk of fatal arrhythmias. If there is a compelling indication, amiodarone seems to be the cheapest.

In all forms of paroxysmal supraventricular tachycardia, beta blockers are suitable for preventing recurrence. Ajmaline i.v. act acutely. (GILURYTMAL et al.) For pre-excitation syndromes, adenosine (ADREKAR et al.) And verapamil for AV nodal tachycardias. Differentiated diagnostics and therapy require assistance from a specialized center.