Left ventricular systolic dysfunction precipitated by verapamil in cardiac amyloidosis.

Cardiac amyloidosis produces a restrictive cardiomyopathy with impaired diastolic function. We report a case in which low-dose verapamil resulted in marked worsening of congestive heart failure, as a result of a profound negative inotropic effect. Withdrawal of verapamil therapy demonstrated a return of systolic function to normal with improvement in heart failure. We postulate that patients with cardiac amyloidosis may be exceptionally sensitive to the negative inotropic effects of calcium-channel blockers either because of abnormal binding to amyloid fibrils or because their usual vasodilator effects are blunted.