Lipid-lowering therapy is associated with a surprisingly large reduction in rates of ventricular arrhythmia and death in heart disease patients with implantable defibrillators, according to an article in the July 2nd issue of the Journal of the American College of Cardiology.

"The magnitude of the apparent benefit on the recurrence of a ventricular tachyarrhythmia is dramatic. The effect size is greater than that of any standard antiarrhythmic drug," said lead author L. Brent Mitchell, MD.

Although results of earlier studies have suggested that drugs that reduce cholesterol are associated with lower rates of sudden cardiac death, the current study is the largest to look at patients with ventricular tachyarrhythmias, the typical cause of sudden cardiac death. The research was done as a substudy of the Antiarrhythmics Versus Implantable Defibrillator (AVID) Trial.

The probability of recurrent ventricular tachycardia/ventricular fibrillation was 40 percent lower for 83 patients who received early and consistent lipid-lowering drug therapy than for 279 patients who were not on lipid-lowering therapy. In addition, the risk of death among 149 patients on lipid-lowering drugs was 36 percent lower than that of 564 patients who did not take such drugs.

The researchers did not report any adverse effects of lipid-lowering therapy, even though the patients in this study were sicker than patients in most trials of lipid-lowering drugs. Although statin drugs are commonly used to lower cholesterol, this study did not collect information on the specific drug used by each patient.

The researchers emphasize that lipid-lowering drug use by patients in this study was neither randomized nor placebo-controlled and the results do not prove that the drugs caused the lower rates of arrhythmia and death. Nevertheless, Mitchell pointed out that lipid-lowering drugs are generally recommended for heart disease patients.

"The results of the large randomized trials of lipid-lowering drug therapy in patients with atherosclerotic heart disease clearly recommend such therapy to patients with the characteristics of those entered into this study, whether or not they have ventricular tachyarrhythmias. Whether or not patients without atherosclerotic coronary artery disease who have ventricular tachyarrhythmias should receive lipid-lowering therapy to take advantage of a direct antiarrhythmic effect must await further study," Mitchell said.

The current research did not explore a mechanism between lipid-lowering and suppression of arrhythmias. Mitchell said if the effect is real (namely, there is a cause-and-effect relation between the drug therapy and the observed outcomes), the drugs might alter ion channel function. It is also possible that lipid-lowering drugs might indirectly reduce arrhythmias by counteracting atherosclerotic disease.

In an editorial, Kelley P. Anderson, MD, said this study raises the possibility of using cholesterol-lowering therapies as an alternative method to prevent arrhythmias: "This is of major interest because currently available antiarrhythmic drugs have significant toxic effects including a substantial risk of fatal proarrhythmia. Most of the currently available lipid-lowering drugs have been shown to be very safe in most subjects. Therefore, if they were proven to have antiarrhythmic properties, they would be used widely."

Anderson pointed out several study limitations: The study was a retrospective analysis, and data did not include specific type or dose of lipid-lowering drug used or the effects of treatment on the cholesterol level. In addition, the editorial noted that being on a lipid-lowering drug prior to the study did not prevent the initial episode of ventricular tachycardia that led to defibrillator implantation.

"However, the most important contribution of Mitchell and colleagues is the strong suggestion that lipid-lowering therapy is relatively safe in this very high risk group of patients with severe coronary artery disease and left ventricular dysfunction, in addition to numerous serious comorbid conditions including kidney, lung, and other vital organ malfunction."