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The first steps to percutaneous coronary intervention (PCI) with Grüntzig’s ground-breaking balloon catheter and the innovative separate use of guidewires and balloon catheters introduced by Martin Kaltenbach are well described in his letter to the editor in this issue of JACC: Cardiovascular Interventions (1). This development continued and evolved with the introduction of the monorail–balloon catheter system (including stenting) (2,3).
Our group started PCI at the University Hospital of Freiburg in 1980 after installing a new high-resolution x-ray system. It is important to remember that in the early years, the dilatation success was judged by the decrease of the trans-stenotic pressure gradient. Coronary images were insufficient because of limited radiographic systems and bulky PCI catheters hindering contrast flow through the guide catheter. Thin balloon-on-wire catheters without distal pressure measurement (described by Geoffrey Hartzler and Spencer King) improved contrast flow but had drawbacks in steerability and balloon exchange.
Therefore, the long-wire technique with the concept of “bare wire first” fulfilled many requirements for better PCI procedures. In my view, however, as in the view of others, the evolution of PCI still suffered from lack of ease and from long laboratory working hours. For maximum safety and larger patient numbers, procedures had to be simpler, safer, and shorter. After weeks of thoughts, I came up with a seemingly simple solution, the “sliding-rail system,” later called “monorail system.” This consisted of a newly designed balloon catheter with a short tube through the balloon segment and a single-lumen shaft, and a short separate guidewire. The relevant inventory step was to desert the long-standing tradition of coaxial catheters (Figure 1). The Schneider Medintag company (Zürich, Switzerland) produced a first version of my catheter to be tested on the kitchen table within 2 weeks!
The monorail catheter dispensed with distal pressure measurement, but could easily slide on any bare wire, also for rapid balloon exchange. To visualize the dilatation result, the thin shaft permitted high contrast flow through the guide catheter, and the balloon could also be pulled back out of the stenosis, whereas it had to stay there to measure the pressure gradient. The other major advantage was the rapid exchange of balloon catheters. The controversy “pressure gradient versus visualization” was debated in many PCI conferences for several years, mostly in the United States, where the acceptance of the monorail technique took longer than in Europe. I remember, at the 10th Anniversary of PTCA Conference in Atlanta in 1987, Richard Myler, in opposition to my arguments, vehemently defended trans-stenotic pressure measurements.
My first public presentation took place in Germany in 1986 at the annual meeting of the German Cardiac Society and in the United States in 1987 at the Annual Scientific Session of the American College of Cardiology. At the very first international symposium addressing PCI technology in Freiburg, Germany, in January 1987, a major session was dedicated to guidewire technology, including long-wire and monorail techniques. Also in 1987, self-expandable stents were introduced by Ulrich Sigwart, and safe guarded PCI results. In 1987, I visited Julio Palmaz in San Antonio and had the chance to participate in animal testing of balloon-expandable stents. These stents, carried by monorail catheters, in a few years evolved as an accepted treatment standard.
The monorail principle was used for a variety of therapeutic and diagnostic instruments to be advanced into coronary arteries, but also cerebral and distal limb arteries, for example, for transfusion, drug delivery, or ultrasound catheters. In acute coronary syndromes, the reliable combination of adequate guidewires and stent-carrying monorail balloon catheters is now well established. The best example for wire versatility is its use for fractional flow reserve measurement.
Considering the evolution of wire technology for PCI, we can draw a continuous line from Simpson’s moveable wire, to the separation of wire and balloon catheter by Kaltenbach, and to the monorail system, which added, together with stents, safety, ease of use, and versatility. Thus, in coronary artery disease (with a few exceptions), the combination of wire and monorail catheter technology has been the basis for instrumental treatment innovations and for the enormous propagation of PCI.
Please note: Prof. Bonzel has reported that he has no relationships relevant to the contents of this paper to disclose.
- 2017 American College of Cardiology Foundation
- Kaltenbach M.
- Bonzel T.,
- Wollschläger H.,
- Just H.
- Bonzel T.,
- Wollschläger H.,
- Kasper W.,
- Meinertz T.,
- Just H.