Avoiding drug problems. The safety of drugs for supraventricular tachycardia

To minimize drug problems in the treatment of supraventricular tachycardias, it is important to understand the spectrum of adverse events and to identify patients at high risk for these problems. Adverse cardiac and non-cardiac effects are associated, to varying degrees, with currently available antiarrhythmics. Cardiac adverse events include the development of rhythm disturbances, such as ventricular tachycardia or torsades des pointes, may result in syncope or death. In a meta-analysis of six randomized trials of quinidine vs placebo for atrial fibrillation, 1.8% of quinidine-treated patients died as opposed to 0.3% of placebo-treated patients. This increase in mortality was also noted in patients enrolled in the Stroke Prevention in Atrial Fibrillation Trial who were treated with type I antiarrhythmics. This increase in mortality was confined primarily to patients with a history of congestive heart failure. In a randomized trial of propafenone and sotalol for the treatment of atrial fibrillation, two out of 50 patients receiving sotalol died suddenly, one of whom had hypokalaemia-associated torsades des pointes. No patient receiving propafenone died during this trial. In a meta-analysis of propafenone's effect in treating supraventricular tachyarrhythmias in over 3100 adult patients, overall mortality was extremely low at 0.3%. Structural heart disease may increase the risk of antiarrhythmic agents. During inpatient drug trials in patients treated for atrial fibrillation at Brigham and Women's Hospital, adverse cardiac events, primarily bradyarrhythmias, occurred in up to 15% of the patients. Older age and prior myocardial infarction were associated with an increased risk of adverse events. Adverse drug problems may be minimized by careful attention to electrolytes, medications, concomitant medical illnesses, and underlying conduction disease. Careful monitoring of patients during initiation of therapy, especially those patients with ischaemic heart disease, congestive heart failure, and who are older, may minimize drug-related problems.