Is preoperative left ventricular function predictive of survival and functional results after aortic valve replacement for chronic aortic regurgitation?

Long-term survival and functional results after aortic valve replacement in asymptomatic patients with chronic severe aortic regurgitation and left ventricular dysfunction

OBJECTIVES

We examined the influence of medical treatment on the results of surgery in terms of long-term survival and functional results in patients with chronic, severe aortic regurgitation (AR).

BACKGROUND

Asymptomatic patients with AR and a reduced left ventricular ejection fraction (LVEF) are at high risk because of a higher-than-expected long-term mortality. The influence of preoperative medical therapy on the outcome after aortic valve replacement (AVR) is not well known.

METHODS

Surgery was indicated for the appearance of a reduced LVEF (<50%). At the time of AVR, there were 134 patients treated with nifedipine (group A), and 132 received no medication (group B).

RESULTS

Operative mortality was similar in the two groups (0.75% vs. 0.76%, p = NS). The LVEF normalized in all of group A, whereas it remained abnormal in 36 group B patients (28%). At 10-year follow-up, LVEF persisted higher in group A (62 +/- 5% vs. 48 +/- 4%, p < 0.001). Five-year survival was similar in the two groups (94 +/- 2% vs. 94 +/- 3%, p = NS). Group A showed a 10-year survival not different from expected and significantly higher than that in group B (85 +/- 4% vs. 78 +/- 5%, p < 0.001), which had a worse survival than expected.

CONCLUSIONS

Unloading treatment with nifedipine in AR allows one to indicate AVR at the appearance of a reduced LVEF with a low operative mortality and an optimal long-term outcome. The concept of surgical correction of AR indicated for reduced LVEF may not be applied to all patients. Indeed, in a large amount of untreated patients, a reduced LVEF preoperatively is not reversed by prompt surgery, indicating irreversible myocardial damage, and 10-year survival is worse than expected.

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.

Enhanced method for predicting left ventricular reverse remodeling after surgical repair of aortic regurgitation: application of ultrasonic tissue characterization

To predict left ventricular (LV) reverse remodeling after surgical repair of aortic regurgitation, we examined 30 patients with aortic regurgitation accompanying LV dilatation by myocardial tissue characterization with integrated backscatter method. Before and after operation, the magnitude of cyclic variation of integrated backscatter (CVIB) was obtained from anterior septum and posterior wall, and averaged value was calculated in each patient. Before operation, LV end-diastolic dimension, fractional shortening, and LV end-diastolic pressure were not significantly different between the patients with (group GR) and without (group PR) decreased LV end-diastolic dimension after operation. Under these conditions, CVIB, which was 9.6 +/- 1.0 dB from healthy volunteers, was significantly greater in group GR, 5.7 +/- 1.4 dB, than that in group PR, 3.8 +/- 0.8 dB (P =.0003). The patients with CVIB >/= 4 before operation were expected to have reverse remodeling after operation with a sensitivity of 79%, a specificity of 82%. These data indicate that preoperative CVIB from the left ventricle provides pivotal information for predicting reverse remodeling after operation for aortic regurgitation in addition to the conventional echocardiographic parameters.

Aortic insufficiency: Indications for surgery in children

The goals of surgery in children with chronic aortic insufficiency are to prevent irreversible left ventricular dysfunction and to provide for long-term survival. In the past, surgical options included placement of a mechanical valve, a porcine bioprosthesis, or an aortic valve homograft. Complications from these options include thromboembolism, prosthetic valve endocarditis, limited durability, and lack of growth potential. The increasing utilization of the Ross procedure to treat chronic aortic insufficiency has led to new interest in the question of when to operate on a regurgitant aortic valve. This review focuses on the pathophysiology of aortic insufficiency and the invasive and noninvasive preoperative indices that may indicate the optimal time for aortic valve surgery in the pediatric population. Copyright 1998 by W.B. Saunders Company

Reduced peak aerobic capacity in asymptomatic left ventricular systolic dysfunction. A substudy of the studies of left ventricular dysfunction (SOLVD). SOLVD Investigator. Studies of Left Ventricular Dysfunction

BACKGROUND

Peak oxygen consumption is reduced in patients with symptomatic congestive heart failure, but functional capacity of patients with asymptomatic left ventricular systolic dysfunction has not been assessed by measurement of peak oxygen consumption attained during graded exercise testing.

METHODS AND RESULTS

Peak oxygen consumption, that is, aerobic capacity (VO2, mL/kg per minute), was determined during graded treadmill exercise using the modified Naughton protocol in 40 patients with left ventricular systolic dysfunction (mean ejection fraction ranging from 14% to 35%; mean, 29%) who, while not receiving any cardiac medications, were totally asymptomatic, and in 41 age-matched normal subjects. Peak exercise duration and VO2 were significantly lower in patients with asymptomatic left ventricular systolic dysfunction than in normal subjects (948 +/- 273 versus 1239 +/- 372 seconds, P < .001, and 22.1 +/- 5.9 versus 29.8 +/- 7.7 mL/kg per minute, respectively, P < .001), while asymptomatic patients and normal subjects reached similar respiratory equivalents (1.14 +/- 0.11 versus 1.11 +/- 0.11 [NS]) and level of perceived exertion, using the modified Borg scale (7.4 +/- 2.6 versus 8.1 +/- 1.5 [NS]). Heart rate, systemic blood pressure, and oxygen pulse response to peak exercise were significantly lower in asymptomatic patients than in normal subjects.

CONCLUSIONS

Although patients with left ventricular systolic dysfunction can be totally asymptomatic in their daily activities, they have experienced a substantial reduction in peak aerobic capacity when compared with normal subjects of similar age.

Nifedipine in asymptomatic patients with severe aortic regurgitation and normal left ventricular function

BACKGROUND

Vasodilator therapy with nifedipine reduces left ventricular volume and mass and increases the ejection fraction in asymptomatic patients with severe aortic regurgitation.

METHODS

To assess whether vasodilator therapy reduces or delays the need for valve replacement, we randomly assigned 143 asymptomatic patients with isolated, severe aortic regurgitation and normal left ventricular systolic function to receive either nifedipine (20 mg twice daily, 69 patients) or digoxin (0.25 mg daily, 74 patients).

RESULTS

By actuarial analysis, we determined that after six years a mean (+/- SD) of 34 +/- 6 percent of the patients in the digoxin group had undergone valve replacement, as compared with only 15 +/- 3 percent of those in the nifedipine group (P < 0.001). In the digoxin group, valve replacement (in a total of 20 patients) was performed because of left ventricular dysfunction (ejection fraction < 50 percent) in 75 percent, left ventricular dysfunction plus symptoms in 10 percent, and symptoms alone in 15 percent. In the nifedipine group, all six patients who underwent valve replacement did so because of the development of left ventricular dysfunction. In addition, all the patients in both groups who underwent aortic-valve replacement had an increase of 15 percent or more in the left ventricular end-diastolic volume index. After aortic-valve replacement, 12 of the 16 patients (75 percent) in the digoxin group and all six patients in the nifedipine group who had had an abnormal left ventricular ejection fraction before surgery had a normal ejection fraction.

CONCLUSIONS

Long-term vasodilator therapy with nifedipine reduces or delays the need for aortic-valve replacement in asymptomatic patients with severe aortic regurgitation and normal left ventricular systolic function.

Maximal oxygen uptake in severe aortic regurgitation: a different view of left ventricular function

Respiratory gas exchange was used to assess left ventricular (LV) function in 22 patients with severe aortic regurgitation (19 men and three women, aged 18 and 70 years, mean 49 years). Anaerobic threshold and symptom-limited maximal oxygen consumption (VO2 max) were measured during treadmill exercise, and the results were compared with conventional echocardiographic and radionuclide indices of LV systolic function. The results were considered with respect to the patients' New York Heart Association functional class. Both rest and exercise LV ejection fractions were variable, but the mean results were similar in all classes. The echocardiographic indices of LV cavity dimensions, fractional shortening, radius/thickness ratio, and systolic wall stress also showed a wide range but with similar mean results in each class. In contrast, VO2 max and anaerobic threshold showed a relationship to functional class. VO2 max was 32.4 +/- 3.4 ml/kg/min in age-matched control subjects; in the patients it was 27.9 +/- 4.7 in class I, 24.7 +/- 5.7 in class II, and 14.2 +/- 2 in the combined class III/IV. Results in patients in classes I and II were similar, but both groups were significantly different from control subjects (p less than 0.05) and from patients in class III/IV (p less than 0.01). About half of the patients with moderate LV dysfunction (judged by reduced VO2 max) were asymptomatic, and LV function was impaired in 4 of 10 patients in class I. Thus, unlike conventional indices of LV function, VO2 max appeared capable of distinguishing patients with moderate-to-severe LV dysfunction from those with little or no LV dysfunction. Measurement of respiratory gas exchange appears to be a valid and useful supplementary means of assessing LV function in severe aortic regurgitation. Further long-term evaluation is required.

Chronic aortic regurgitation: indications for operation--1988

Timing of operation in a patient with severe aortic regurgitation is a difficult and controversial decision, especially when the patient is asymptomatic or minimally symptomatic. A rational decision can be made when the pathophysiologic features of aortic regurgitation and the natural history of medically treated patients are understood and the benefits and risks associated with aortic valve replacement are known. Proper interpretation of the literature involving echocardiography and nuclear cardiology is essential, as is consideration of the constantly changing surgical techniques and results. Aortic valve replacement should be recommended for those patients with chronic aortic regurgitation who are severely symptomatic (New York Heart Association Functional Class III or IV), in order to ameliorate symptoms and increase longevity. In asymptomatic or minimally symptomatic patients, close continued serial follow-up is necessary in order to detect the onset of resting left ventricular dysfunction and to recommend the optimal timing for surgical intervention.