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Published on: April 5, 2011
Should an abnormal serum potassium concentration be considered a correctable cause of cardiac arrest?
G F Michaud1, S A Strickberger
1Brown University School of Medicine, Providence, Rhode Island, USA.
Insights
Electrolyte abnormalities like abnormal serum potassium levels can cause dangerous heart arrhythmias. Current guidelines suggest defibrillators may be ineffective, but new evidence supports their use in specific cardiac arrest patients.
Area of Science:
- Cardiology
- Electrophysiology
- Cardiac Arrest Research
Background:
- Electrolyte abnormalities, particularly abnormal serum potassium, are cited as correctable causes of life-threatening ventricular arrhythmias.
- Current guidelines (Class III indication) suggest ventricular defibrillator therapy is ineffective and potentially harmful in these cases, despite limited supporting data.
- Serum potassium levels fluctuate during cardiac arrest, and many patients have structural heart disease and take medications affecting potassium.
Purpose of the Study:
- To evaluate the effectiveness of implantable defibrillators in patients with structural heart disease and abnormal serum potassium concentrations experiencing ventricular arrhythmias.
- To challenge the existing guideline recommendation against defibrillator use in this specific patient population.
Main Methods:
- Analysis of data from the Antiarrhythmics Versus Implantable Defibrillators (AVID) registry, which followed patients with correctable causes of electrolyte imbalance.
- Review of a preliminary study involving 169 patients with sustained ventricular arrhythmia treated with an implantable defibrillator.
- Assessment of the relationship between initial serum potassium concentration and the probability of appropriate defibrillator therapy.
Main Results:
- Outcomes in the AVID registry were similar to those in the main trial, suggesting comparable effectiveness.
- In a preliminary study, freedom from appropriate defibrillator therapy was 18% at five years.
- The probability of receiving appropriate defibrillator therapy was independent of the initial serum potassium concentration.
Conclusions:
- Existing guidelines recommending against defibrillator use for ventricular arrhythmias associated with abnormal serum potassium may be overly restrictive.
- Implantable defibrillators may be a viable treatment option for initial episodes of sustained ventricular tachycardia or ventricular fibrillation in patients with structural heart disease and abnormal serum potassium.
- Further research is warranted to refine treatment strategies for ventricular arrhythmias in the context of electrolyte abnormalities.
Abstract:
According to American Heart Association/American College of Cardiology Practice Guidelines, electrolyte abnormalities, including abnormal serum potassium concentrations, are considered a correctable cause of a life-threatening ventricular arrhythmia. Ventricular defibrillator therapy in this situation is a class III indication, and thought to be ineffective and perhaps harmful, although there are minimal data to support this recommendation. The steady-state serum potassium concentration frequently changes during a cardiac arrest. Additionally, the vast majority of cardiac arrest patients have structural heart disease and are commonly treated with a variety of medications that can alter the serum potassium concentration. In the Antiarrhythmics Versus Implantable Defibrillators (AVID) trial, patients with a correctable cause of an electrolyte imbalance were excluded from study participation but were followed in the AVID registry. Similar outcomes were observed among patients in the AVID registry and the main trial. Spironolactone therapy in patients with congestive heart failure decreases all-cause mortality and sudden and nonsudden cardiac death. In a preliminary study of 169 patients with an episode of a sustained ventricular arrhythmia treated with an implantable defibrillator, freedom from appropriate defibrillator therapy was 18% after five years. The probability of appropriate defibrillator therapy was independent of the initial serum potassium concentration. For these reasons, our current clinical practice is to use an implantable defibrillator to treat an initial episode of sustained ventricular tachycardia or ventricular fibrillation that occurs in a patient with structural heart disease and an abnormal serum potassium concentration.
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