Patients who develop acute, severe AI, most commonly from an acute type A aortic dissection or infective endocarditis, have a life-threatening condition as the LV cannot compensate for the abrupt onset of volume overload. Because patients with acute severe AI often present with LV deterioration, manifested by pulmonary edema and cardiogenic shock, urgent treatment is necessary. Intensive vasodilator therapy is beneficial when feasible, but urgent surgical intervention is required.

Patients with chronic AI, however, can ­tolerate the gradual onset of volume overload with compensatory eccentric hypertrophy of the LV. Asymptomatic patients with severe AI and ­normal LV function have a risk of sudden death of less that 0.2 % per year. However, the natural history of symptomatic patients with severe AI is poor with a risk of death greater than 10 % per year for patients with angina pectoris and greater than 20 % per year for patients with heart failure [3–5]. Studies in animals shows that long-standing chronic AI results in myocardial fibrosis with increased deposition of extracellular matrix [6]. The resulting myocardial fibrosis may be the pathologic basis of irreversible LV dysfunction and end-stage heart failure for patients with severe AI.

AVR for patients with AI and advanced heart failure (EF <25 %) can be associated with an operative mortality of up to 10 % and poor long-term survival [7]. Because of such poor outcomes, consideration of heart transplantation for these patients has been recommended in the past. However, results of AVR for AI with advanced heart failure (EF <30 %) have improved dramatically over time with operative mortality of 17 % before 1985 compared to 0 % after 1985 in a large surgical series (Fig. 5.4) [8]. Moreover, patients with advanced heart failure undergoing AVR after 1985 can have a long-term survival similar to patients without advanced heart failure (Fig. 5.5).

Recommendation from the 2008 American Heart Association/American College of Cardiology (AHA/ACC) and 2007 European Society of Cardiology (ESC) guidelines for chronic AI are similar [7, 9]. Class I indications for surgery for patients with severe AI include the presence of symptoms, LV dysfunction with EF <50 %. Class IIa indications include LV dilatation with LVESD >55 mm or LVEDD >75 mm and concomitant cardiac ­surgery including coronary artery bypass graft (CABG), other valvular surgery, or aortic aneurysm repair. Class IIb indications include LV dilatation with LVESD >50 mm or LVEDD >70 mm. No particular recommendations are made by either set of guidelines regarding patients with advanced heart failure. Although patients with recent onset of symptoms and patients that improve with intensive medical therapy including intensive vasodilators, diuretics, or inotropic support may demonstrate LV recovery after AVR, exactly which patients will demonstrate an improvement in LV function after a successful AVR is unknown. AVR is, nevertheless, a better alternative than the higher risk of long-term medical management alone for severe AI with advanced heart failure [10]. Therefore, it is reasonable to proceed with AVR in patients with severe AI and advanced heart failure in order to stop further decompensation and facilitate the chronic medical management of the patient’s heart failure, especially the use of beta-blockers which is contraindicated in patients with AI. If possible, the use of blood transfusion should be avoided in patients with advanced heart disease in case further deterioration occurs, resulting in candidacy for heart transplantation.

Aortic stenosis can be caused by senile, calcific aortic stenosis, which is the most common cause for patients older the 75 years; bicuspid aortic valve, which commonly manifest in younger patients between 65 and 75 years; or, less frequently, rheumatic heart disease. The diagnosis of severe aortic stenosis is made with echocardiography based on a combination of parameters. Peak jet velocity and mean pressure gradients can be reliably measured but are flow dependent and therefore affected by the left ventricular stroke volume and cardiac output. Aortic valve area, calculated using the continuity equation, is less dependent on stroke volume and cardiac output and most reliably identifies patients with severe AS in advanced heart failure. When peak jet velocity >4.0 m/s, mean valvular gradient >40 mmHg, or aortic valve area <1.0 cm², the AS is considered severe [7].

In advanced heart failure, the left ventricle is unable to generate either a significant peak jet velocity or mean pressure gradient despite an aortic valve area that is diagnostic for severe aortic stenosis. This condition, termed low-gradient aortic stenosis (LGAS), can present a diagnostic challenge for clinicians because patients with LGAS can have either truly severe aortic stenosis with resulting poor ejection fraction or primary cardiomyopathy with only moderate aortic stenosis. The latter condition, termed pseudo-severe AS, occurs because the calculated aortic valve area may not be a reliable measurement of the severity of AS. In advanced heart failure, the aortic valve may fail to open completely not as a result of a fixed stenosis but as a result of low stroke volume (Fig. 5.6). Patients with pseudo-severe AS, therefore, have a calculated aortic valve area which is falsely reduced.

In order to distinguish between fixed severe AS and pseudo-severe AS, a dobutamine stress study either with echocardiography (Fig. 5.7) or direct pressure measurements during cardiac catheterization (Fig. 5.8) can be performed in patients with LGAS. Doses of up to 20 mcg/kg/min of dobutamine are infused under physician surveillance, while the peak jet velocity, mean pressure gradient, and aortic valve area are measured. In patients with fixed aortic stenosis, the peak jet velocity and mean pressure gradient will increase while the valve area remains unchanged as stroke volume and ejection fraction increases. In patients with pseudo-severe AS, on the other hand, the valve area increases while the peak jet velocity and mean pressure gradient remain unchanged [11, 12].