11.9.5 Indications and surgical results

 As long as the aortic insufficiency is paucisymptomatic and the ventricle remains compensated, the natural history is generally favourable: simple vasodilatory medical treatment gives a survival rate of 85% at 5 years and 58% at 10 years: Angiotensin converting enzyme inhibitors or angiotensin receptor blockers, dihydropyridine-type calcium blockers, low-dose beta-blockers to limit the risk of ventricular failure and dilatation of the ascending aorta (heart rate not less than 70 beats/min) [1,4,13]. This is true as long as there is no deterioration in function. However, once clinical manifestations or ventricular dysfunction become established, the situation deteriorates rapidly: without intervention, survival is only 4 years from the onset of angina and 2 years from the onset of heart failure [10]. Pharmacotherapy is not a substitute for surgery, which is the only curative option, but it has two applications: to restore balance before surgery, particularly in acute AI, and to manage the rare inoperable patient [14].

Surgery is indicated as soon as the patient becomes symptomatic or as soon as dysfunction becomes apparent on echocardiography, but before irreversible dilatation has occurred [1,6,13]. Aortic valve prosthesis (AVP) or replacement (AVR) is indicated in the following situations (Class I) [1,3,13,19].

  • Severe AI in symptomatic patients (stage D), regardless of left ventricular function and size;
  • Severe AI in asymptomatic patients (stage C2) if LV function is reduced (EF < 50%) or if the ventricle is dilated (Dts > 5.0 cm, Dtd > 7.0 cm);
  • Severe AI in patients undergoing concomitant surgery for other valvular disease or coronary artery bypass grafting.

Isolated AI, even severe AI, in asymptomatic patients without LV dysfunction, dilatation or ascending aortic aneurysm is not an indication for surgery; regular follow-up is preferable. Surgery is recommended when the LV diameter exceeds 2.5 cm/m2 in telesystole or 4.0 cm/m2 in telediastole [1,3,8,13]. The right time for surgery is not always easy to determine because LV dysfunction and dilatation begin before symptoms appear [2,11]. The longer the period of preoperative dysfunction, the less chance the ventricle has of returning to normal capacity. If it is not irreversibly dilated before AVR, the LV partially recovers from its eccentric hypertrophy and its mass decreases; its end-diastolic volume tends towards normal during the first month [5,17]. However, the majority of patients with preoperative dysfunction and dilatation (Dtd > 4.0 cm/m2 ) continue to suffer from long-term dysfunction after surgery and have a 20-year survival rate of less than 50% [3]. This proactive stance should be weighed against the natural history of asymptomatic AI (cardiac event rate: 4%/year) and the risks of the procedure (mortality 1-2%, 20-year survival 70%) [2,18].

A number of indicators are useful in defining the indication for surgery in asymptomatic patients [11].

  • Natriuretic peptides: BNP > 130 pg/mL, NT.proBNP > 600 pg/mL;
  • Mitral annular descent velocity (S') < 8 cm/s;
  • Worsening of longitudinal systolic shortening (strain and strain rate);
  • Presence of fibrosis on MRI (late gadolinium enhancement);
  • Occurrence of symptoms and/or impairment of EF on exercise testing (dobutamine stress echo);
  • LV dilatation (3D echo): Vts > 50 mL/m2, Vtd > 135 mL/m2 (volume measurements are more relevant than diameter measurements).

Operative mortality varies from <1% (NYHA I-II patients, simple surgery) to 7% (NYHA III-IV patients, combined aortic surgery), with an average of 2-3% [7,16,19]. If surgery is performed early in the course of the disease, survival beyond 20 years is 65%, compared with 45% if surgery is performed late [18]. In type I and II disease, repair is often possible but requires more experience than mitral repair and is not available in all centres. It is more physiological than a prosthesis, does not require anticoagulation as mechanical valves do, and has a better attrition curve than bioprostheses in young patients; the risk of endocarditis and thromboembolism is lower [15]. However, the 5-year risk of recurrent AI is 11% [12].

Acute failure is an indication for emergency surgery, which can only be delayed for the few hours required to stabilise haemodynamics with vasodilators and ventilatory support. Intra-aortic balloon pump is contraindicated as the diastolic increase would increase regurgitation. 
 
 
Bicuspid insufficiency is often associated with ascending aortic aneurysm, defined as an aorta with a diameter > 50% greater than normal. Surgery of the aortic valve and aortic root is indicated when the aortic diameter is > 4.5 cm or is increasing by > 0.5 cm/year (see Aortic bicuspidity) [2,19]. When the diameter of the aorta at the level of the sinuses of Valsalva reaches 6 cm, the annual mortality from rupture or dissection is 11% [9]. The size of the ascending aorta defined as the threshold for replacement is therefore lower in bicuspid disease (4.5 cm) than in tricuspid disease (5.5 cm) because it develops more rapidly and the risk of dissection is nine times higher in bicuspid disease [2].
 
 
 Indications and surgical results 
AVR is indicated when the patient becomes symptomatic or the LV begins to dilate (Dts > 2.5 cm/m2, Dtd > 4.0 cm/m2):
- Severe AI in symptomatic patients, regardless of LV function and size 
- Severe AI in asymptomatic patients when LV function is reduced or the LV is dilated
- Severe AI in patients undergoing other cardiac surgery 
- Severe AI and ascending aortic diameter > 5.5 cm (tricuspid) or > 4.5 cm (bicuspid) 
- Acute AI with cardiogenic shock: Emergency AVR
 
Long-term outcomes are all the better when surgery is performed earlier in the course of the disease. 
 
The average operative mortality rate is 2-3% (1.2% for NYHA I-II patients, 7% for NYHA IV patients).
 
 

 © CHASSOT PG, BETTEX D, August 2011, last update November 2019

 

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