Timing of surgery in chronic aortic regurgitation

When deciding on therapy for aortic regurgitation (AR), it is imperative to distinguish between acute and chronic AR. Symptoms and echocardiographic findings are essential in distinguishing acute from chronic AR and in assessing the severity. Vasodilators have been shown to be helpful in treating patients with chronic severe AR. The timing of aortic valve replacement in chronic severe AR remains controversial. Symptoms, left ventricular function, and response to exercise have been shown to be the most important prognostic indicators.     

Timing of aortic valve surgery in chronic aortic stenosis and regurgitation

The correct timing of aortic valve replacement in chronic aortic stenosis or regurgitation is a very important and sometimes difficult task for physicians caring for patients with aortic valve disease. In this review, we will present the current available literature regarding the appropriate management of these patients.     

When to intervene in chronic aortic regurgitation

Symptomatic patients with chronic aortic regurgitation should undergo aortic valve replacement. Asymptomatic patients with normal left ventricular function are not surgical candidates, but aortic valve replacement should be performed in most patients with left ventricular dysfunction, even if symptoms are not yet present. The short-term administration of vasodilators is generally beneficial, but there is only meager evidence that the hemodynamic benefits are maintained; for this reason, the wide application of these agents should be postponed until well-designed clinical trials document a long-term benefit.     

Irreversible morphological changes contributing to depressed cardiac function after surgery for chronic aortic regurgitation.

The timing of surgery in chronic aortic regurgitation remains a difficult problem. To identify variables predictive of postoperative haemodynamic improvement, changes in left ventricular mass, volume, morphology, and histochemistry were analysed in 67 patients undergoing surgery for chronic aortic regurgitation. Patients were divided into two groups: those in whom the left ventricular echo diameters returned to normal after operation (51 patients, group A), and those with postoperative dilatation (16 patients, group B). A preoperative biopsy was obtained in all patients; postoperative tissue samples were available in 13 patients (five from group A, eight from group B). Data were correlated with the postoperative clinical, haemodynamic state over a follow-up period of three years. Regression of hypertrophy was usually incomplete. Echocardiographic and angiographic data could not define the type and degree of dysfunction which was irreversible. Massive fibre hypertrophy (mean 34.1 micrometers), moderately or severely increased interstitial fibrous tissue, reduced levels of the myofibrillar and mitochondrial enzymes adenosine triphosphates and succinate dehydrogenase in pre- and post-operative tissue samples correlated with persistent dilation, cardiac failure, and early death (group B). Irreversible morphological and functional changes contributed to a depressed cardiac function after operation. Preoperative ventricular biopsies are thus of prognostic importance in volume overload.     

Improved outcomes after aortic valve surgery for chronic aortic regurgitation with severe left ventricular dysfunction.

OBJECTIVES: Among patients undergoing aortic valve surgery for chronic aortic regurgitation (AR), we sought to: 1) compare survival among those with and without severe left ventricular dysfunction (LVD); 2) identify risk factors for death, including LVD and date of operation; and 3) estimate contemporary risk for cardiomyopathic patients. BACKGROUND: Patients with chronic AR and severe LVD have been considered high risk for aortic valve surgery, with limited prognosis. Transplantation is considered for some. METHODS: From 1972 to 1999, 724 patients underwent surgery for chronic AR; 88 (12%) had severe LVD. They were propensity matched to patients with nonsevere LVD to compare hospital mortality, interaction of operative date with severity of LVD, and late survival. Propensity score-adjusted multivariable analysis was performed for all 724 patients to identify risk factors for death. RESULTS: Survival was lower (p = 0.04) among patients with severe LVD than among matched patients with nonsevere LVD (30-day, 1-, 5-, and 25-year survival estimates were 91% vs. 96%, 81% vs. 92%, 68% vs. 81%, and 5% vs. 12%, respectively). However, survival of patients with severe LVD improved dramatically across the study time frame (p = 0.0004): hospital mortality decreased from 50% in 1975 to 0% after 1985, and time-related survival in patients with severe LVD operated on since 1985 became equivalent to that of matched patients with nonsevere LVD (p = 0.96). CONCLUSIONS: Neutralizing risk of severe LVD has improved early and late survival such that aortic valve surgery for chronic AR and cardiomyopathy is no longer a high-risk procedure for which transplantation is the best option.     

Impact of echocardiography on indications for surgery in chronic mitral and aortic regurgitation

Echocardiography is the key examination in the assessment of mitral and aortic regurgitation, as it is able to describe the etiology and mechanism of the disease and assess its severity and its repercussions on cardiac cavities and pulmonary pressures. Surgery now tends to be indicated at earlier stages, largely based on criteria drawn from echocardiography. In severe mitral regurgitation, surgery is not disputed in presence of left ventricular ejection fraction < 60% and/or end-systolic diameter > 45 mm. In a selected group of patients aged < 75 years, with a very high likelihood of successful repair and a low operative risk, surgery should be considered earlier (if ejection fraction is > 60% and end-systolic diameter < 45 mm) in degenerative regurgitation such as flail leaflets. In aortic regurgitation, surgery should be considered in presence of an acceptable operative risk as soon as end-systolic diameter exceeds 25 mm/m2 (and/or end-diastolic diameter > 70 mm) or resting ejection fraction < 55%. Surgery should be performed rapidly in dystrophic aortic regurgitation, independent of its severity, if the diameter of the ascending aorta exceeds 50 or 55 mm, or if it increases rapidly during follow-up. Echocardiography is therefore at the center of the strategic discussion concerning the indication for and timing of surgery.     

Management of chronic aortic regurgitation

Opinion statement Aortic regurgitation may be the most treacherous of the valvular lesions due to subtlety of symptoms and physical findings and due to difficulty in timing surgical intervention to prevent permanent cardiac dysfunction. Cardiac imaging (eg, echocardiography or magnetic resonance) is critical to quantify the degree of regurgitation and to detect significant left ventricular dysfunction or dilation. Stress testing can be useful in timing surgical intervention in borderline cases. Medical therapy consists of afterload reduction, diuresis, and inotrope administration. Surgical therapy today consists of aortic valve repair in a minority of cases or aortic valve replacement in the remainder. Percutaneous means to replace the aortic valve are in development. Cardiac decompensation may require cardiac transplantation.     

Hypertrophic and functional response to experimental chronic aortic regurgitation

Aortic regurgitation was induced by retrograde perforation of an aortic valve cusp under hemodynamic guidance in 12 New Zealand White rabbits. Regurgitant fraction was documented by electromagnetic flow probe and six sham-operated animals served as controls. Two-dimensional, M-mode and Doppler echocardiography was performed pre-operatively and serially post-operatively for 3 to 6 months. Animals with aortic regurgitation developed progressive left ventricular dilatation and eccentric hypertrophy. Left ventricular internal dimension at end-diastole and left ventricular mass were increased from baseline values by 41 and 94% (P less than 0.001), respectively; fractional shortening was stable while end-systolic stress increased 50% (P less than 0.01. Thus, acutely induced aortic regurgitation in rabbits results in a chronic model which may be appropriate for stimulation of the hypertrophic response to aortic regurgitation in humans.     

Indications for surgery for aortic regurgitation

Aortic valve replacement for isolated aortic regurgitation (AR) is usually not indicated unless the regurgitation is severe. However, not all patients with severe AR require aortic valve replacement. This review focuses on the causes of AR and the pathophysiology of acute versus chronic AR, and the attendant adaptive mechanisms of the left ventricle that ultimately determine their different natural histories. Aortic valve surgery must be performed in a timely manner to prevent cardiac death, ameliorate symptoms, and limit late postoperative excess mortality.     

Differences in left ventricular adaptation to chronic mitral and aortic regurgitation

For comparable volume load, impedance to ejection of the regurgitant volume in AR exceeds that in MR. To determine whether this load difference results in differences in PLVH and ejection performance, we studied consecutive, untreated, asymptomatic patients (11 in each group) by echocardiography and Doppler. Mean LVID, SBP, h, and FS were, respectively, in AR vs MR: 60.3 +/- 3.1 mm vs 62.0 +/- 2.3 mm (p = NS), 152 +/- 7.1 mm Hg vs 125 +/- 6.4 mm Hg (p less than 0.005), 12.1 +/- 0.4 mm vs 10.5 +/- 0.6 mm (p less than 0.04), and 0.38 +/- 0.02 vs 0.43 +/- 0.02 (p = NS). The h/R ratio reflects the PLVH-0.41 +/- 0.02 in AR and 0.34 +/- 0.02 in MR (p less than 0.02). The FS correlates positively with h/R in either lesion, but was higher in MR for any given h/R. The difference in loading conditions imposed by both lesions is associated with a difference in the PLVH as well as in ejection performance.     

Left ventricular remodeling in chronic aortic regurgitation

Left ventricular (LV) shape in chronic volume overload due to aortic regurgitation is commonly described as rounder than in normal subjects. This statement derives from observations of qualitative nature or based on the measure of eccentricity index. We analyzed LV shape and function in 16 normal subjects (N) and in 24 patients with chronicpure aortic regurgitation (AR), without coronary artery disease or associated mitral regurgitation. LV cavity geometry was quantitatively evaluated from end-diastolic and end-systolic outlines obtained in 30° RAO angiographic projection, by calculating: 1. the eccentricity and circularity indexes, 2. the regional curvature at 90 equidistant points using a windowed Fourier series approximation of contours, in which the number of harmonics and filter-window were locally chosen in order to minimize the reconstruction errors and to maximize the smoothness of the curve, 3. by measuring the length of the anterior and posterior hemi-perimeter of LV outlines and 4. by performing a Fourier analysis of LV contours.Neither eccentricity nor circularity indexes were adequate to differentiate shape abnormalities, whereas Fourier geometric analysis indicated abnormalities of shape in AR. Regional curvature showed that diastolic outline of AR had a greater curvature of the anterobasal, anterolateral and inferoapical regions and a lower curvature of the anteroapical one. Systolic outline showed a greater curvature of the inferoapical region and a lower curvature of the anteroapical one. The angiographic apex, i.e. the point of the greatest curvature, was shifted towards the mitral plane (at end-diastole from point 48.4 in N to 51.5 in AR; p < 0.001, at end-systole from point 46.3 in N to 49.1 in AR; p=0.007), owing to a greater length of the anterior hemi-perimeter in respect to N. The increase in anterior hemi-perimeter length was significantly related to the decrease in pump function (increase in end-systolic volume index and decrease in ejection fraction).Conclusion in respect to normal subjects LV shape in aortic regurgitation is not simply more globular, but it definitely appears to be asymmetric because of the prevailing elongation of the anterior hemi-perimeter from the aortic corner to the apex suggesting a remodeling of the left ventricle with a prevailing expansion of the anterolateral regions. These alterations in cavity geometry correlate to the decrease in pump function.     

Left ventricular function in chronic aortic regurgitation

Left ventricular performance was determined in 42 patients with moderate or severe aortic regurgitation during upright exercise by measuring left ventricular ejection fraction and volume with radionuclide ventriculography. Classification of the patients according to exercise tolerance showed that patients with normal exercise tolerance (greater than or equal to 7.0 minutes) had a significantly higher ejection fraction at rest (probability [p] = 0.02) and during exercise (p = 0.0002), higher cardiac index at exercise (p = 0.0008) and lower exercise end-systolic volume (p = 0.01) than did patients with limited exercise tolerance. Similar significant differences were noted in younger patients compared with older patients in ejection fraction at rest and exercise (both p = 0.001) and cardiac index at rest (p = 0.03) and exercise (p = 0.0005). The end-diastolic volume decreased during exercise in 60% of the patients. The patients with a decrease in volume were significantly younger and had better exercise tolerance and a larger end-diastolic volume at rest than did patients who showed an increase in volume. The mean corrected left ventricular end-diastolic radius/wall thickness ratio was significantly greater in patients with abnormal than in those with normal exercise reserve (mean +/- standard deviation 476 +/- 146 versus 377 +/- 92 mm Hg, p less than 0.05). Thus, in patients with chronic aortic regurgitation: 1) left ventricular systolic function during exercise was related to age, exercise tolerance and corrected left ventricular end-diastolic radius/wall thickness ratio, and 2) the end-diastolic volume decreased during exercise, especially in younger patients and patients with normal exercise tolerance or a large volume at rest.