Patients were referred to AVR, if they suffered from isolated severe AS (peak velocity ≥4 m/s and mean pressure gradient ≥40 mmHg in the presence of normal left ventricular function, calculated valve area 2) and presented with symptoms (exertional dyspnea ≥ functional NYHA class II and/or exertional angina pectoris ≥ functional CCS class II and/or syncope) or with reduced left ventricular function (ejection fraction ≤50%) when asymptomatic. Patients with a need for additional coronary artery bypass grafting (CABG) at the time of aortic valve replacement were not excluded from the study. However, those who were primarily referred to surgery for CABG and additionally received an aortic prosthesis for non-severe AS were not enrolled. Patients with more than mild concomitant aortic regurgitation were also excluded.
In the present work, we evaluated the impact of patient- related parameters, such as aortic annulus diameter, left ventricular hypertrophy, body size, age and gender, as well as the influence of prosthesis type on the occurrence of PPM. In a cohort of consecutive patients referred to aortic valve replacement for isolated severe aortic stenosis (AS), PPM patients were older, more likely to be female and had smaller aortic annuli. However, only carriers of bioprosthetic valves and patients with smaller aortic root diameters were at increased risk for PPM in a multivariable regression analysis.
Conventional aortic valve replacement (AVR) surgery has been in clinical use since 1960. Results, particularly in high-risk populations such as the very elderly and frail, continue to improve in response to the challenges posed by this growing segment of the patient population. Transcatheter aortic valve implantation (TAVI) is a fairly recent development, performed for the first time in 2002. The last decade has seen an exponential growth in the application of this technology in higher-risk populations. Results of recent randomized prospective trials demonstrate both the future promise and current problems of the TAVI approach. Many patients deemed inoperable for AVR have been treated successfully by TAVI. However, elevated procedural and late mortality rates, excessive early and late stroke, and a significant incidence of periprosthetic aortic valve insufficiency and patient-prosthesis mismatch all suggest caution in extending this technology to patients able to undergo conventional AVR with a low risk of early or late complications.
The first successful surgical implantation of an aortic valve prosthesis was reported by Harken et al. in 1960. Many patients who had been terminally ill from aortic valve stenosis or insufficiency and unresponsive to medical therapy could now be restored to good health. Over the ensuing 50 years, numerous innovations and refinements of these early techniques and prostheses have been developed.
Throughout its history, however, TAVI has been associated with the risk of five persistent major complications: high perioperative and late mortality, elevated early and late stroke rates; major vascular complications; patient prosthesis mismatch; and the occurrence of significant and progressive post-implant periprosthetic insufficiency. Additionally, the long-term natural history after TAVI of the progressive proliferative disease that causes calcific AS is unknown.
At present, only biological prosthetic valves are available for TAVI. Mechanical valves are still considered the optimal choice in younger patients. While some patients who have experienced biological valve failure may have undergone “resleeving” procedures during a second TAVI procedure, it is currently not established as a standard therapy., Concurrent CAB was performed in 27% to 34% of our patients. Although angioplasty would be an option in some cases, many had diffusely calcified multivessel disease.
Ewe et al. reported on data from a multicenter study in which 165 patients were evaluated for PPM. Studies were performed at baseline, before hospital discharge, and 6 months after TAVI. They found that 30 patients (18.2%) had an indexed EOA of 2/m2. A substantially higher proportion of these patients with PPM did not show clinical improvement compared with those without PPM (36.7% vs. 1.5%, P 2 (P=.002); 10.2 mm & 11.5 mm (P=0.008). At 1 year, relief of symptoms was similar in both groups. The reported valve areas suggest that smaller prostheses were implanted in both groups. In addition to having no capability for aortic leaflet resection, TAVI has no capability for aortic root enlargement. Dacron patch graft angioplasty is commonly employed during AVR to enlarge small aortic roots at least one size to allow implantation of a larger conventional prosthesis.
In the natural history of untreated calcific aortic stenosis, the size of the obstructing calcific masses progressively increases. The extent of these changes is shown in and . The disease is characterized by the formation of large exophytic masses. This material is unstable, and it is relatively easy to break off small pieces. Since the untreated disease induces death as the stenosis becomes critical, the ultimate natural history of the compressed and displaced leaflets is unknown. Data from the PARTNER trial at 2 years shows stable aortic gradients and areas; for the critically ill patients approved for treatment by the FDA, this may not be an issue at this time. However, if use of TAVI is expanded to younger patients with the expectation of a long survival, close observation will be required for monitoring of restenosis, stroke, and more periprosthetic leaks due to the unstable nature of this calcified material
Ascending aortic aneurysm surgery may be required in conjunction with AVR most commonly because of atherosclerotic degeneration, Marfan’s syndrome, or aneurysmal disease from bicuspid aortic valve disease. The latter may be present in a significant proportion of these patients. Bicuspid aortic valve disease is currently considered to be a contraindication for TAVI because the single-slit opening may not conform to the circular shape of the deployed prosthesis. The aortic root and ascending aorta also tend to be larger in these patients.
Undoubtedly, this problem will eventually be solved with a prosthesis or prosthetic annulus that is more conforming. It is now well recognized that some patients are unsuitable for TAVI because of the pathoanatomy of their calcified aortic roots and leaflets (). Detailed preoperative CT studies of the aortic root are considered essential to avoid displacement into the coronary ostia of calcified masses ().
A comparison of the capabilities of TAVI vs. AVR is shown in . In our unselected total series of 1,514 AVR patients, only 44% had undergone an isolated AVR. The remainder have received concurrent CAB, ascending aortic aneurysm repair, or mitral or tricuspid valve surgery. While most patients had pure aortic stenosis, about one-third had some degree of aortic insufficiency, which is a contraindication to TAVI. AVR allows treatment of any size of aortic “annulus” because prosthetic valves are available up to a diameter of 33 mm.