Medizinische Universität Graz Austria/Österreich - Forschungsportal - Medical University of Graz
Gewählte Publikation:
Shimwa, M.
Pharmacological therapy of cardiac arrhythmias
Humanmedizin; [ Diplomarbeit ] Medical University Graz; 2021. pp. 69
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- Autor*innen der Med Uni Graz:
- Betreuer*innen:
- Holzer Ulrike
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- Abstract:
- The need for treatment of arrhythmias depends on symptoms and seriousness of the arrhythmia. The treatment is directed at the causes. Although there have been important technological advances for the treatment of cardiac arrhythmias, antiarrhythmic drugs(AADs) remains the cornerstone treatment for patients with arrhythmias. AADs can modify impulse generation and conduction to prevent arrhythmias from occurring or re-occurring and reduce symptoms that come with them. In the past few decades, the understanding of the molecular and cellular basis of cardiac electrophysiology and mechanisms underlying cardiac arrhythmias has increased immensely. Research is needed to develop, subclassify, and identify new therapeutic targets aiming to provide mechanism-based therapy. Although they have been many attempts to provide a more mechanistic classification such as the Sicilian gambit in 1991, AADs remain most commonly classified according to Vaughan Williams. AADs are divided into 4 groups: sodium channel blockers (class I), beta-blockers (class II), potassium channel blockers (class III), and calcium channel blockers (class IV). There are also unclassified AADs such as adenosine, which do not belong to the above mentioned groups. Most of the current available AADs have different electrophysiological targets which may give an anti or pro-arrhythmic effect that means while trying to suppress arrhythmias with AADs, AADs themselves, can lead to other (potentially more dangerous) arrhythmias. For this reason, caution should be taken before, during, and after administering the medication. Regular re-evaluation of the drug is recommended. The clinical significance of the AADs lies in the type of arrhythmias that each drug or class can treat and the potential side effects of each overall classification or individual medication. Trials such as CAST and SWORD have shown that class I and class III AADs causes excess mortality in patients where benefits were expected. Beta-blockers have shown to prolong life compared to other AADs. They reduce sudden death and total mortality in patients with heart failure. Class IV AADs may be inappropriate in heart failure because they decrease conduction in AV node and shorten the cardiac action potential. They have not shown to reduce mortality and in case of nifedipine, may even increase mortality in patients after MI. Many cardiac medicines appear safe for use during pregnancy and the time mothers breastfeed their infants. However, the evidence is lacking for some drugs and many of them carry risks of adverse events. Shared decision making, considering the risks and benefits of each AAD is vital to help pregnant women weigh up potential risks to themselves and their unborn baby. In elderly patients, there are changes in pharmacokinetic and pharmacodynamic, not only for AADs but for every drug taken as well. Aging changes absorption, distribution, metabolism, and elimination of drugs. So the liver and kidney function should be regularly checked to avoid side effects and the dose may be needed to be adjusted. Furthermore, the choice of AADs in the elderly is complicated due to the presence of co-morbidities and polypharmacy, which may cause drug interactions. When the patient under current AAD remains symptomatic and his/her situation does not improve, there are other treatments which might relieve the symptoms or cure arrhythmias. These treatments include cardioversion, defibrillation, implantable cardioverter-defibrillators (ICDs), pacemakers, catheter ablation, and surgery.