Percutaneous Transcatheter Aortic Valve Implantation: Past Accomplishments, Present Achievements and Applications, Future Perspectives

Transcatheter mitral valve implantation via transapical approach: an early experience

OBJECTIVES

As many as 50% of patients with severe symptomatic mitral valve regurgitation are denied surgical valve replacement or repair due to high operative risk. We describe an early series of cases of transcatheter implantation with a CardiAQ™ mitral valve via a transapical approach.

METHODS

Three consecutive patients with an Society of Thoracic Surgeons (STS) mortality score of >22% were selected for transcatheter mitral valve implantation (TMVI) on compassionate grounds. All patients were elderly, had severe mitral regurgitation (MR), were in Class IV heart failure and deemed unsuitable for the MitraClip. Two of the patients had functional MR in the setting of ischaemic cardiomyopathy with left ventricular ejection fraction (LVEF) <40%, deemed while the remaining patient had chordal rupture with extensive anterior leaflet flail (preserved LVEF). Comorbidities included previous coronary artery bypass surgery (n = 2), severe pulmonary hypertension (n = 1) and moderate to severe chronic renal failure (n = 3). A CardiAQ mitral valve was implanted using fluoroscopy and transoesophageal (TEE) guidance via a standard transapical approach.

RESULTS

Accurate prosthesis positioning and deployment with immediate elimination of the MR was achieved in all 3 cases. Two patients made full clinical recovery and were discharged home. Post-procedural TEE performed on Days 1, 30 and 60 days showed good valve function, stable valve position and minimal LVOT gradient. One patient expired on the postoperative day 9 due to pneumonia.

CONCLUSIONS

TMVI using the CardiAQ™ device via a transapical approach is feasible and effective.

Imaging in the context of replacement heart valve development: use of the Visible Heart(®) methodologies

In recent years huge strides have been made in the fields of interventional cardiology and cardiac surgery which now allow physicians and surgeons to repair or replace cardiac valves with greater success in a larger demographic of patients. Pivotal to these advances has been significant improvements in cardiac imaging and improved fundamental understanding of valvular anatomies and morphologies. We describe here a novel series of techniques utilized within the Visible Heart(®) laboratory by engineers, scientists, and/or anatomists to visualize and analyze the form and function of the four cardiac valves and to assess potential repair or replacement therapies. The study of reanimated large mammalian hearts (including human hearts) using various imaging modalities, as well as specially prepared anatomical specimens, has enhanced the design, development, and testing of novel cardiac therapies.

A review of most relevant complications of transcatheter aortic valve implantation

Transcatheter aortic valve implantation (TAVI) has emerged for treating aortic stenosis in patients who are poor candidates for surgical aortic valve replacement. Currently, the balloon-expandable Edwards Sapien valve—which is usually implanted via a transfemoral or transapical approach—and the self-expanding CoreValve ReValving system—which is designed for retrograde application—are the most widely implanted valves worldwide. Although a promising approach for high-risk patients, the indication may be expanded to intermediate- and eventually low-risk patients in the future; however, doing so will require a better understanding of potential complications, risk factors for these complications, and strategies to individualize each patient to a different access route and a specific valve. This paper reviews the most relevant complications that may occur in patients who undergo catheter-based aortic valve implantation.

CT and MR imaging of the aortic valve: radiologic-pathologic correlation

Valvular disease is estimated to account for as many as 20% of cardiac surgical procedures performed in the United States. It may be congenital in origin or secondary to another disease process. One congenital anomaly, bicuspid aortic valve, is associated with increased incidence of stenosis, regurgitation, endocarditis, and aneurysmal dilatation of the aorta. A bicuspid valve has two cusps instead of the normal three; resultant fusion or poor excursion of the valve leaflets may lead to aortic stenosis, the presence of which is signaled by dephasing jets on magnetic resonance (MR) images. Surgery is generally recommended for patients with severe stenosis who are symptomatic or who have significant ventricular dysfunction; transcatheter aortic valve implantation (TAVI) is an emerging therapeutic option for patients who are not eligible for surgical treatment. Computed tomography (CT) is an essential component of preoperative planning for TAVI; it is used to determine the aortic root dimensions, severity of peripheral vascular disease, and status of the coronary arteries. Aortic regurgitation, which is caused by incompetent closure of the aortic valve, likewise leads to the appearance of jets on MR images. The severity of regurgitation is graded on the basis of valvular morphologic parameters; qualitative assessment of dephasing jets at Doppler ultrasonography; or measurements of the regurgitant fraction, volume, and orifice area. Mild regurgitation is managed conservatively, whereas severe or symptomatic regurgitation usually leads to valve replacement surgery, especially in the presence of substantial left ventricular enlargement or dysfunction. Bacterial endocarditis, although less common than aortic stenosis and regurgitation, is associated with substantial morbidity and mortality. Electrocardiographically gated CT reliably demonstrates infectious vegetations and benign excrescences of 1 cm or more on the valve surface, allowing the assessment of any embolic complications.

Transcatheter aortic-valve implantation for aortic stenosis

BACKGROUND

Short-term results are presented from our first year of experience with transcatheter aortic-valve implantation [corrected] (TAVI) at the University Hospital of North Norway.

MATERIALS AND METHODS

TAVI was used to treat 25 patients with aortic stenosis [corrected] from September 2008 to August 2009. 25 patients operated with conventional aortic valve replacement (AVR) served as controls.

RESULTS

The TAVI group had a significantly higher EuroSCORE (p < 0.001) than the AVR group. No patients in the TAVI group were treated in the intensive care unit while those in the AVR group received 38 days of intensive care in total. The TAVI group had shorter operating times (p < 0.001), larger mean valve sizes (p < 0.001) and significantly fewer postoperative transfusions (p < 0.001) than the ACR group. Peri-operative stroke and myocardial infarction did not occur in the TAVI group while there was one incidence of stroke and one myocardial infarction in the AVR group. The postoperative transvalvular mean gradient decreased in both groups (p < 0.001) and was significantly lower in the TAVI group (p = 0.001). The NYHA class improved significantly in the TAVI group (p < 0.001). No patients needed implantation of a permanent pacemaker. 30-day mortality was four patients in the AVR group and one patient in the TAVI group. After discharge one patient died in each group.

INTERPRETATION

TAVI is safe and effective for selected patients with aortic stenosis [corrected] who are assessed as high risk for AVR. Long-term results are needed and will be decisive for use of this approach in the future.

Dosimetric data and radiation risk analysis for new procedures in interventional cardiology

The purpose of this study was to evaluate radiation doses to the patients and operators during interventional cardiology procedures, with a particular focus on the transcatheter aortic valve implantation (TAVI). Patient doses for 5549 diagnostic and therapeutic procedures and 76 TAVI were examined, as well as occupational doses to Cardiology Department operators. The average patient dose for TAVI was double that of PTCA and six times higher than a simple CA; statistically significant differences were shown in the average patient dose for both transfemoral and transapical access; the measurements show a corresponding increase in the average occupational dose for the cardiologist. Interventional cardiology could increase the collective dose and occupationally exposed worker doses; this increase could be significant if the use of certain procedures is extended to younger people; particular attention in the choice of procedure, optimisation and staff education and organisation is therefore suggested.