The idea of single lead atrial synchronous ventricular pacing dates back to the early 1960s when the atrial triggered ventricular paced (VAT) mode was introduced.1 Its clinical use was only limited by the fact that an additional atrial lead had to be inserted, a rather difficult procedure with the available technology. However, after the development of specific atrial leads, dual chamber pacing (DDD) also became available and its clinical success made the concept of single lead AV synchronous pacing (VAT, VDD) obsolete.

It took another decade to learn that placement of atrial leads remained difficult, before Antonioli and coworkers re-introduced the concept of a single AV lead in the late 1970s. They observed that atrial depolarisation could reliably be detected through the blood stream by far-field sensing from a unipolar electrode floating in the mid-right atrium.2 The most important fact was that no direct wall contact was needed for sensing, which initiated the development of a variety of different leads. After years of experimental and clinical research, the first single AV leads with properly matched VDT pacemakers were implanted in 1980 by the same investigators.3 After an initially slow growing clinical experience with unipolar VDD pacemakers, the real breakthrough of VDD pacing took place, when the first bipolar VDD pulse generators with highly sensitive atrial sensing circuits for reliable P wave detection and avoidance of atrial oversensing became available.4-6

Today, multiple VDD pacing systems are on the market …