Changes in the occurrence of mechanical alternans after long-term beta-blocker therapy in patients with chronic heart failure.

Mechanical alternans has been observed in patients with severe congestive heart failure, and the phenomenon is considered to be a terminal sign. Therapeutic strategies for chronic heart failure have significantly developed, but it is uncertain whether patients with mechanical alternans can be effectively treated or not. Seventeen consecutive patients with dilated cardiomyopathy were enrolled: 11 were treated with beta-blockers on conventional therapeutic regimens and 6 patients were not indicated for or were unable to continue beta-blockade. Mechanical alternans was detected during cardiac catheterization in the patients under physiologic tachycardia (110 beats/min) and stepwise dobutamine loading. In the initial study, mechanical alternans occurred in 70.6% of the patients: 8 of the 11 being treated with beta-blockers and 4 of the 6 without beta-blockade therapy. In the second study, none of the patients taking beta-blockers showed mechanical alternans under the same protocol; the occurrence of mechanical alternans did not change in the patients who were not being treated with beta-blockers. The left ventricular ejection fraction increased in patients whose mechanical alternans could not be induced during the follow up, but decreased in the patients in whom mechanical alternans was repeatedly inducible. It is concluded that mechanical alternans is associated with the failing myocardium and may be potentially correctable.