Table 10–4 outlines the 2014 guidelines for surgical intervention in aortic stenosis. Valve intervention is warranted in all patients who have symptomatic severe aortic stenosis. There are also times when asymptomatic aortic stenosis should undergo intervention. Asymptomatic patients with severe aortic stenosis (aortic valve area less than 1.0 cm2) should generally undergo intervention according to the following guidelines: (1) they are undergoing other cardiac surgery (ie, CABG), (2) there is evidence for a reduced LVEF (less than 50%), (3) when the mean gradient exceeds 55 mm Hg (peak velocity greater than 5 m/sec), (4) when there is failure of the BP to rise more than 20 mm Hg with exercise, (5) when there is severe valvular calcium, or (6) when there is evidence of a rapid increase in the peak aortic gradient (more than 0.3 m/sec/year). Following the onset of heart failure, angina, or syncope, the prognosis without surgery is poor (50% 3-year mortality rate). Medical treatment may stabilize patients in heart failure, but intervention is indicated for all symptomatic patients with evidence of significant aortic stenosis.
Table 10–4.2014 AHA/ACC guidelines for surgical indications in aortic stenosis. ||Download (.pdf) Table 10–4. 2014 AHA/ACC guidelines for surgical indications in aortic stenosis.
|Recommendations ||COR ||LOE |
|AVR is recommended in symptomatic patients with severe AS (stage D) ||I ||B |
|AVR is recommended for asymptomatic patients with severe AS (stage C2 or D) and LVEF < 50% ||I ||B |
|AVR is indicated for patients with severe AS (stage C or D) when undergoing other cardiac surgery ||I ||B |
|AVR is reasonable for asymptomatic patients with very severe AS (aortic velocity ≥ 5 m/s) (stage C2) and low surgical risk ||IIa ||B |
|AVR is reasonable in asymptomatic patients (stage C1) with severe AS and an abnormal exercise test ||IIa ||B |
|AVR is reasonable in symptomatic patients with low-flow/low-gradient severe AS with reduced LVEF (stage S1) with a low-dose dobutamine stress study that shows an aortic velocity ≥ 4 m/s (or mean gradient ≥ 40 mm Hg) with a valve area ≤ 1.0 cm2 at any dobutamine dose ||IIa ||B |
|AVR is reasonable for patients with moderate AS (stage B) (velocity 3.0–3.9 m/s) who are undergoing other cardiac surgery ||IIa ||C |
|AVR may be considered for asymptomatic patients with severe AS (stage C1) and rapid disease progression and low surgical risk ||IIb ||C |
|AVR may be considered in symptomatic patients who have low-flow/low-gradient severe AS (stage S2) who are normotensive and have an LVEF ≥ 50% if clinical, hemodynamic, and anatomic data support valve obstruction as the most likely cause of symptoms ||IIb ||C |
The surgical mortality rate for valve replacement is low, even in older adults, and ranges from 2% to 5%. This low risk is due to the dramatic hemodynamic improvement that occurs with relief of the increased afterload. Mortality rates are substantially higher when there is an associated ischemic cardiomyopathy. Severe coronary lesions are usually bypassed at the same time as aortic valve replacement (AVR), although there are few data to suggest this practice affects outcome. In some cases, a staged procedure with stenting of the coronaries prior to surgery may be considered, especially if a percutaneous AVR approach is being considered. Around one-third to one-half of all patients with aortic stenosis have significant CAD, so this is a common concern. With the success of transcatheter aortic valve replacement (TAVR), the treatment options have greatly expanded for many patients with severe aortic stenosis. For this reason, a Heart Valve Team approach bringing together invasive and noninvasive cardiologists, radiologists, anesthesiologists, and cardiac surgeons is mandatory; clinical factors (such as frailty) and anatomic features (such as a calcified aorta, vascular access, etc) can affect the decision making.
Medical therapy to reduce the progression of disease has not been effective to date. Statins have been assessed in four major clinical trials (SALTIRE [atorvastatin], SEAS [simvastatin plus ezetimibe], ASTRONOMER [rosuvastatin], and PROCAS [rosuvastatin]). None revealed any benefit on the the progression of aortic stenosis or on clinical outcomes despite the association of aortic stenosis with atherosclerosis. If patients with aortic stenosis have concomitant CAD, the guidelines for the use of statins should be followed. Efforts to reduce stenosis progression by blockage of the renin-angiotensin system have also been ineffective. Control of systemic hypertension, though, is an important adjunct, and inadequate systemic BP control is all too common due to unreasonable concerns about providing too much afterload reduction in patients with aortic stenosis. Normal systemic BP is important to maintain as the LV is affected by the total afterload (systemic BP plus the aortic valve gradient).
The interventional options in patients with aortic valve stenosis has expanded with the use of TAVR and depend on the patient’s lifestyle and age. The algorithm to decide when an AVR is appropriate in various situations is outlined in Figure 10–3. The 2017 ACC/AHA valvular guidelines modify this only in that surgical AVR can be considered for any of the indications outlined in the figure, whether asymptomatic or not. TAVR should be reserved only for those patients with symptoms. These newest guidelines point out that TAVR is equivalent to surgical AVR in all of the randomized trials of symptomatic patients. As of 2017, TAVR for aortic stenosis can be applied to all except the lowest risk (less than 4%). The lowest risk patients are being studied in trials randomizing between TAVR and surgical AVR.
Algorithm for the management of aortic valve stenosis. (Reproduced, with permission, from Nishimura RA et al. 2014 AHA/ACC Guideline for the Management of Patients With Valvular Heart Disease: A Report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines. Circulation. 2014 Jun 10; 129(23):e521–643. © 2014 American Heart Association, Inc.)
In young and adolescent patients, percutaneous balloon valvuloplasty still has a small role. Balloon valvuloplasty is associated with early restenosis in the elderly population, and thus is rarely used except as a temporizing measure. Data suggest aortic balloon valvuloplasty in elderly people has an advantage only in those with preserved LV function, and such patients are usually excellent candidates for surgical AVR. (VIDEO 10–11). The Ross procedure is generally still considered a viable option in younger patients, and it is performed by moving the patient’s own pulmonary valve to the aortic position and replacing the pulmonary valve with a homograft (or rarely a bioprosthetic valve). However, dilation of the pulmonary valve autograft and consequent aortic regurgitation, plus early stenosis of the pulmonary homograft in the pulmonary position, has reduced the enthusiasm for this approach in most institutions. Middle-aged adults generally can tolerate the anticoagulation therapy necessary for the use of mechanical aortic valves, so patients younger than 60 years generally undergo AVR with a bileaflet mechanical valve. If the aortic root is severely dilated as well (greater than 4.5 cm), then the valve may be housed in a Dacron sheath (Bentall procedure) and the root replaced along with the aortic valve. Alternatively, a human homograft root and valve replacement can be used. In patients older than 60 years, bioprosthetic (either porcine or bovine pericardial) valves with a life expectancy of about 10–15 years are routinely used instead of mechanical valves to avoid need for anticoagulation. Data favor the bovine pericardial valve over the porcine aortic valve (AUDIO 10–19). As it is becoming clearer that bioprosthetic valve degeneration in the larger valves can be potentially repaired by percutaneous valve-in-valve TAVR, it is likely that the use of mechanical valves will continue to decline. If the aortic annulus is small, a bioprosthetic valve with a short sheath can be sewn to the aortic wall (the stentless AVR) rather than sewing the prosthetic annulus to the aortic annulus. (Annulus is a relative term when speaking of the aortic valve, since there is no true annulus.) Another popular surgical option when the aorta is enlarged is the use of the Wheat procedure; it involves aortic root replacement above the coronary arteries and replacement of the aortic valve below the coronary arteries. The coronary arteries thus remain attached to the native aorta between the new graft and prosthetic valve rather than being reimplanted onto an artificial sheath or homograft.
Video 10–11: Percutaneous balloon valvuloplasty of calcific aortic stenosis.
Hemodynamic tracings of simultaneously recorded aortic and left ventricular pressure waveforms are depicted. The mean pressure gradient across the aortic valve is proportionate to the area between the pressure curves and is markedly reduced after valvuloplasty. (Used, with permission, from T Amidon and T Chou.)
Audio 10–19. Prosthetic aortic valve.
Note the crisp click of a prosthetic non-biological valve. A2 is the loudest portion of the second heart sound (S2), consistent with a prosthetic aortic valve. (Reproduced, with permission, from T. Anthony Don Michael, MD. Mastering Auscultation [CD-ROM], 2000.)
In patients with a bicuspid aortic valve, there is an associated ascending aortic aneurysm in about half. If the maximal dimension of the aortic root is greater than 5.5 cm, it is recommended to proceed with root replacement regardless of the severity of the aortic valve disease. It is also appropriate to intervene when the maximal aortic root size is greater than 5.0 cm in diameter if there is a family history of aortic dissection or the aortic root size increases by more than 0.5 cm in 1 year. The aortic valve may be replaced at the same time if at least moderate aortic stenosis is present or may be either left alone or repaired (valve sparing operation). If there is an indication for AVR and the root is greater than 4.5 cm in diameter, root replacement is also recommended.
The use of mechanical versus bioprosthetic AVR has changed over time. A bioprosthetic valve is acceptable for patients at any age for whom anticoagulant therapy is contraindicated, not desired, or cannot be managed, and is preferred in patients over the age of 70. An aortic mechanical valve should be used in patients younger than 50 years of age who can take warfarin (this recommendation is a decrease from age 60 in the recent updated guidelines). Either type of valve is acceptable between the ages of 50 and 70 years depending on patient preference and any issues with warfarin usage.
Anticoagulation is required with the use of mechanical aortic valves, and the international normalized ratio (INR) should be maintained between 2.0 and 3.0 for bileaflet valves. In general, mechanical aortic valves are less subject to thrombosis than mechanical mitral valves and do not need bridging with anticoagulation unless there are other thromboembolic risk factors or there is an older generation AVR. Low-dose aspirin is recommended as well. Some newer bileaflet mechanical valves (On-X) allow for a lower INR range from 1.5 to 2.0. Clopidogrel is recommended for the first 6 months after TAVR in combination with lifelong aspirin therapy. DOACs are not recommended for any mechanical valves but may be used in patients with a bioprosthetic AVR if treating atrial fibrillation or venous thrombosis.
The estimated use of TAVR has grown dramatically, with a gross estimate of over 500,000 implants worldwide. In the United States, the Food and Drug Administration (FDA) has granted approval for two devices, the Edwards SAPIEN and the Medtronic CoreValve, for use in patients with at least a 4% surgical risk (intermediate risk) as measured by the Society of Thoracic Surgeons. These devices are fundamentally stents with a trileaflet bioprosthetic valve constructed within them. There are a variety of implantation approaches, though most valves are placed via a femoral artery approach. Other options include an antegrade approach via transseptal across the atrial septum, via the LV apex with a small surgical incision, via the subclavian arteries, via the carotid, or via a minithoracotomy. The Edwards SAPIEN valve is a balloon-expandable valvular stent, while the CoreValve is a valvular stent that self-expands when pushed out of the catheter sheath. Multiple other devices are in trials, many with excellent early results. These devices will allow for a wider range of aortic valve sizes to be treated; can be delivered with smaller catheters, eliminating the need for femoral artery cutdowns; will allow for repositioning before permanent implantation; and appear to result in less paravalvular regurgitation and less injury to the conduction system. Cost remains a major issue. All of the professional societies stress the importance of a Heart Valve Team when considering aortic stenosis intervention. This is critically important because many patients referred for TAVR have serious comorbid conditions that will not improve with alleviation of the aortic stenosis. A 2017 consensus document from the ACC provides a decision pathway for the use of TAVR. This document summarizes background information and provides a checklist of items to consider when deciding between surgical AVR and TAVR. The importance of quality of life and frailty is emphasized because some of the most elderly or most debilitated patients may not benefit from any procedure. Frailty is a risk factor for death and disability following TAVR and surgical aortic valve replacement. A brief four-item scale encompassing lower-extremity weakness, cognitive impairment, anemia, and hypoalbuminemia outperformed other frailty scales.
Figure 10–4 outlines the suggested indications for TAVR based on the 2017 updated AHA/ACC guidelines. eTable 10–2 outlines the key clinical trials regarding TAVR and includes the risk categories of the patients, the trials associated with those patients, the mortality observed, and complications. As the patient risk has declined, so has the overall mortality. While the initial trials included only inoperable patients (Partner 1B) or those of very high risk (Partner 1A and CoreValve High Risk), positive results from the Partner 2A intermediate risk study and the NOTION registry in a low-risk population has encouraged application of TAVR to lower and lower risk aortic stenosis patients. The FDA has approved TAVR for use in the intermediate risk category. Ongoing randomized trials, SAPIEN 3 and Evolut R, are actively enrolling patients with the lowest risk to compare surgical AVR to TAVR. Enrollment is complete in these trials but results were not available by the end of 2018.
eTable 10–2.Key clinical trials regarding the use of transcatheter aortic valve replacement versus medical treatment and specific patient risk categories. ||Download (.pdf) eTable 10–2. Key clinical trials regarding the use of transcatheter aortic valve replacement versus medical treatment and specific patient risk categories.
|TRIAL ||STS SCORE ||MORTALITY ||STROKE ||>MILD AR ||PACEMAKER |
| ||TAVR ||MED ||TAVR ||MED ||TAVR ||MED ||TAVR ||MED ||TAVR ||MED |
|Partner 1B ||11.2 ||12.1 ||30.7 ||50.7 ||10.0 ||4.5 ||10.5 ||4.2 ||4.5 ||7.8 |
|Partner 1A ||11.8 ||11.7 ||24.2 ||26.8 ||6.0 ||3.1 ||6.8 ||1.9 ||5.7 ||7.8 |
|CoreValve ||7.3 ||7.5 ||14.2 ||19.1 ||8.8 ||12.6 ||7.1 ||1.4 ||22.3 ||11.3 |
|Partmer 2A ||5.8 ||5.8 ||10.1 ||11.3 ||6.2 ||6.4 ||8.0 ||0.6 ||8.5 ||6.9 |
|SURTAVI ||Corevalve Randomized Trial of Intermediate Risk Patients |
|NOTION ||2.9 ||3.1 ||4.9 ||7.5 ||2.9 ||4.6 ||15.7 ||0.9 ||38.0 ||2.4 |
|Partner 3 ||Sapien Randomized Trial of Low Risk Patients |
|Evolut R ||Corevalve Randomized Trial of Low Risk Patients |
Choice of TAVR versus surgical AVR in patients with severe symptomatic AS. (Reproduced, with permission, from Nishimura RA et al. 2017 AHA/ACC focused update of the 2014 AHA/ACC guideline for the management of patients with valvular heart disease: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines. Circulation. 2017 Jun 20;135(25):e1159–95. © 2017 American Heart Association, Inc.)
TAVR is also being used more frequently in “valve-in-valve” procedures to reduce the gradient in patients with prosthetic valve dysfunction (regardless of whether in the aortic, mitral, tricuspid, or pulmonary position). While the results of TAVR in patients with bicuspid aortic valves (as opposed to tricuspid) have been less impressive, newer modifications have improved the success rates in these anatomic situations as well.