• Since 1967, three series of rechargeable single-cell silvermercuric oxide-zinc pacemakers have been implanted in dogs with complete heart block. The five nonhermetic units in series I failed after 18 months, primarily due to prototype cell deficiencies, although one cell functioned for eight years. The six units in series II contained improved cells, but failed due to gradual transepoxy fluid absorption after ≤ 31 months. All rechargeable cells were salvaged and dried, and, seven years after their manufacture, they continue to power pacing circuits. Series III now totals 20 doubly hermetically sealed units, tested for up to three years (total more than 300 months or 26 years), with no pacemaker failures. Accelerated tests indicate a minimum life of more than 50 years. A clinical trial is in progress.
(Arch Surg 111:1231-1234, 1976)