HISTORICAL PERSPECTIVE

Cardiac catheterisation and coronary angiography

More than two decades have passed since Andreas Grüntzig (Fig. 1.1) first attempted the percutaneous relief of a coronary stenosis. This single event, representing the culmination of many years of experimentation, has now passed into legend. Percutaneous coronary revascularisation has emerged as a routine cardiac procedure, but the trials and tribulations of workers in the field of invasive cardiology, whose efforts led stepwise to that day in September 1977, are nevertheless worthy of review.

Figure 1.1 Andreas Grüntzig.

The era of invasive cardiac investigation and intervention began with the pioneering efforts of Forssman in 1929. The latter half of the previous century had seen Claude Bernard and later, Chaveau and Marey, develop the concept of ‘cardiac catheterisation’ in animal subjects employing intra-arterial or intravenous intubation in horses or dogs, but it was Forssman who demonstrated its feasibility and safety in humans. Taking advantage of his friendship with a nurse, Gerda Ditzen, he was able to cut down on his own cephalic vein and advance a rubber urethral catheter to his right atrium, documenting its progress with X-ray fluoroscopy. Right heart catheterisation was further developed with the work of Cournand and Ranges (1941), while investigation of the left heart proceeded via parasternal, subxiphoid, apical, suprasternal, transbronchial, papravertebral and transseptal approaches; until Zimmerman reported the results of retrograde left heart catheterisation in 1949.

Other developments also allowed cardiac catheterisation to progress to a stage recognisable in the present day. In 1953, Seldinger introduced his technique of entering arteries percutaneously. Serious peri-procedural cardiac arrhythmias could be addressed with closed chest cardiac compression (1960) and the introduction of direct current (DC) defibrillation by Lown in 1962. X-ray documentation had been limited to single plate exposures until the image intensifier coupled to film exposure at rapid frame rates resulted in the emergence of true cineangiography. Cardiac events could thereby be visualised in ‘real time’ incorporating less contrast volume and less radiation exposure to both patient and operator.

By the mid-1950s, visualisation of the coronary circulation had been achieved only by flush injection into the aortic root. A number of modifications to this technique were in use, including power injection into the sinus of Valsalva. It was during one such procedure in 1958, that an National Institute of Health (NIH) catheter inadvertently migrated into the right coronary artery and the subsequent injection of contrast opacified the vessel without the patient experiencing ill effects; Mason Sones had thereby demonstrated that selective coronary arteriography was possible. During the next few years, the first 1000 coronary angiograms were performed with only 2 deaths and a 2% incidence of ventricular fibrillation. Pre-formed polyethylene catheters were introduced in 1962 and were further modified by Judkins heralding the modern era of comprehensive percutaneous cardiac investigation.

TECHNOLOGICAL DEVELOPMENTS

The procedure of coronary angioplasty, although modified over the last 20 years by enhanced technology, still conforms to the original descriptions of the technique (Figs. 1.2 and 1.3). Under radiographic control and local anaesthesia, the coronary arterial ostium is engaged with a guiding catheter and the target lesion traversed with an atraumatic guidewire. A balloon-tipped catheter is then advanced over the guidewire until it reaches the site of atheromatous obstruction, at which point the balloon is inflated with diluted contrast medium. The size of balloon, inflation pressure and the number and duration of inflations, varies according to the lesion characteristics. When the angiographic appearances suggest adequate lesion dilatation, all the equipment is removed and the patient is returned to the ward.

Figure 1.2 Diagrammatic transverse cross section of coronary dilatation. Note the development of intimal fissuring as a result of balloon barotrauma.

Figure 1.3 Diagrammatic representation of the principles of balloon coronary angioplasty. The deflated balloon catheter is positioned across a coronary stenosis and inflated (middle). It is then deflated leaving the atheromatous lesion compressed and the stenosis relieved (bottom).

The original Grüntzig balloon material was PVC and of low compliance. It would rupture rather than exceed its designed maximal outer diameter. The catheter shaft incorporated a double lumen which allowed the balloon to be expanded and voided, and for pressure to be monitored at the catheter tip. Other than for a short-fixed guidewire, steerability was not possible. Balloon material limited inflation pressures to 5 atmospheres, the catheter shaft diameter was almost 5 French (F) (1.7 mm) and crossing profiles were high. The subsequent 15 years witnessed a rapid growth in technology resulting in marked improvements in guiding catheters and guidewires, as well as in balloon design.

WORLDWIDE ACTIVITY

Initial enthusiasm for PTCA resulted in an understandable rush to learn the technique. This prompted leaders in the field to convene a workshop in June 1979, in Bethesda, USA, under the auspices of the National Heart, Lung, and Blood Institute (NHLBI). Here it was decided to limit the availability of PTCA to centres with clearly defined and agreed protocols. Even the commercial provider of the equipment agreed to abide by these guidelines such that operators could not obtain balloon catheters without having undergone approved instruction in the technique. Results of procedures were pooled in a unified and systematic fashion so that many of the first insights into PTCA and its outcomes derived from this NHLBI registry.

Between 1977 and 1982 data on 3079 patients were entered into the registry from 106 institutions. Of these patients, 77% were male with a mean age of 54 years, two-thirds having Canadian Heart Class III or IV symptoms. Almost three-quarters had single vessel disease, the LAD artery being the most commonly addressed. Left main stem disease was attempted in 1% and bypass graft dilatation performed in 4%.

At this early stage several drawbacks were apparent when PTCA was compared with coronary artery surgery. First, the initial and long-term results were unpredicatable and the definition of a successful procedure was uncertain; a 20% reduction in stenosis severity was achieved in 67% of the original registry. Secondly, the risks of PTCA were not clearly superior to surgery (myocardial infarction: 5.5%, emergency CABG: 6.6%, death: 0.9%) acknowledging that the majority had single vessel disease. Thirdly, it became apparent that a relatively small volume of procedures was being undertaken by an increasingly large number of operators thus potentially diluting an initially small experience. Finally, technical factors like vessel angulation or tortuosity, distal disease and lesion calcification, eccentricity or chronic occlusion, were anticipated to limit PTCA to perhaps 10 or 15% of patients considered for surgical revascularisation.

The technical advances in PTCA described in this chapter resulted in greater applicability of the procedure and thereby an exponential increase in activity. Emory University in Atlanta, where Grüntzig had undertaken much of his later work, was in the vanguard of interventional research. Their experience, reported in 1985, indicated a learning curve for the technique and improving results associated with increasing experience and the new emerging technology. For example, the circumflex artery became more accessible with steerable systems rising from 7% to 16% of all procedures and enjoying similar success rates as with the other main arteries. Their experience in 3500 consecutive cases set a standard to which other interventional units could aspire with success in 89%, myocardial infarction in 2.6%, emergency CABG in 2.7% and death in 0.1% of patients.

The growth in activity has been seen worldwide, with the USA particularly generating large volumes. It is interesting to note that ten years after the first report of coronary artery bypass grafting in 1968, 100,000 operations had been performed in the USA. However this figure had been overtaken by the number of PTCA procedures (106000) undertaken within only seven years of its first reported series in 1978. Recent UK data suggest that CABG rates may now be on the decline as PTCA activity continues to increase (Fig. 1.4).

Figure 1.4 Comparison of rates of PCI and CABG in the UK.

Source: BCIS Audit Returns (2006) (www.bcis.org.uk)

In 1995, there were an estimated 350 000 PTCA cases performed in the USA, with almost 500 000 undertaken worldwide. In Europe, activity has been similarly increasing from approximately 250 000 in 1995, to almost 300 000 in 1997. Individual European countries differ in interventional activity and thus in the PTCA rates per million of the population (Fig. 1.5). Growth in activity in the UK, although substantial, nevertheless lags behind that of other European countries like France, Germany and Belgium. This discrepancy in the UK compared with other Western European nations is primarily a funding issue within the National Health Service (NHS). A lack of resources limits the number of patients coming forward for angiographic investigation, and thereby the number available for revascularisation with CABG as well as PTCA.

Figure 1.5 Comparison of time trends in European PCI activity.

Source: Euroheart Survey, 3^rd Report (www.escardio.org)

In the UK, data on PTCA activity is collected by the British Cardiovascular Intervention Society (BCIS) on an annual basis. Input from participating centres has been voluntary, but nevertheless the volumes recorded have always been in concordance with those suggested by industry sources when equipment sales have been examined. Thus in 1991, 52 centres in the UK undertook 9933 PTCA procedures representing 174 cases per million population. The annual growth in activity has varied between approximately 12% and 19%, the average since 1991 being 15% per year. In 2006, a total of 91 centres reported almost 74 000 procedures, giving a rate per million of 1216 (Fig. 1.6).

Figure 1.6 Annual PCI activity in the UK. Source: BCIS audit returns, 2006 (www.bcis.org.uk)