Influence of preoperative left ventricular function on results of homograft replacement of the aortic valve for aortic stenosis

Echocardiographic predictors of survival in low gradient aortic stenosis

Echocardiographic predictors of long-term survival for patients with low gradient aortic stenosis who undergo aortic valve replacement have not been previously reported. This study shows that patients with larger pre- and postoperative left ventricular volumes, a lower mean preoperative aortic pressure gradient, and failure of volumes to decrease and ejection fraction to increase postoperatively may have a poor prognosis.

Usefulness of left atrial size in predicting postoperative symptomatic improvement in patients with aortic stenosis

Although surgery is highly effective for symptomatic relief in patients with aortic stenosis, symptoms of congestive heart failure may be still present postoperatively. This group of patients with aortic stenosis is characterized by a wide range of left atrial size, which can predict postoperative symptomatic improvement.

Pulmonary autograft versus homograft replacement of the aortic valve: a prospective randomized trial

BACKGROUND

Pulmonary autografts offer many theoretical advantages. However, the operation is complex, may interfere with right ventricular and pulmonary outflow function, and requires a longer operative time than does the homograft operation. The effects of these potential disadvantages are unknown.

METHODS

To clarify these issues we randomized 70 patients undergoing aortic valve replacement to an aortic homograft group (group A = 37 patients; 53%; 34 male, 3 female) or a pulmonary autograft group (group B = 33 patients; 47%; 28 male, 5 female). Ages varied from 12 to 65 years (mean 39 +/- 15 years) for group A and from 3 to 54 years (mean 29 +/- 15 years) for group B (p = not significant). Eleven patients in group A (30%) and eight in group B (24%) had previous aortic valve surgery. All patients were operated on by the same surgeon. The mean cardiopulmonary bypass time was 113 +/- 29 minutes (range 66 to 175 minutes) for group A and 151 +/- 31 minutes (range 115 to 226 minutes) for group B (p < 0.002). Mean aortic crossclamp time was 85 +/- 19 minutes (range 45 to 140 minutes) for group A and 109 +/- 20 minutes (range 74 to 164 minutes) for group B (p = 0.02). In 32 patients (86.5%) the aortic homograft was implanted as a root with coronary reimplantation. All pulmonary autografts were implanted as a root.

RESULTS

No early or late deaths had occurred in this series at a mean follow-up time of 16 months (range 3 to 21 months). Two patients (one in each group) required reexploration for bleeding. No statistically significant differences were observed between the two groups with regard to ventilatory support (group A, mean 10 +/- 8.5 hours; group B, mean 29 +/- 85 hours), total blood loss (group A, mean 471 +/- 347 ml; group B, mean 543 +/- 404 ml), intensive care unit stay (group A, mean 1.2 +/- 0.6 days; group B, mean 2 +/- 3.7 days), and hospital stay (group A, mean 9.5 = 3.2 days; group B, mean 12 +/- 6 days). Postoperatively, all patients are in New York Heart Association class I (93%) or II (7%) (p = not significant). Ejection fraction for the two groups did not change significantly over the follow-up period. Left ventricular mass and diastolic diameter showed progressive regression, with no apparent difference between the two treatment groups to date. Echocardiographic evaluation of aortic valve function at 6 months showed good valve function in all patients with no evidence of aortic regurgitation in 80% of both groups. In group B the right ventricular outflow gradient was below 15 mm Hg over the follow-up period. Holter monitoring, available only in 44 patients (63%), showed most of the arrhythmias to be grade 0 to 1 of the modified Lown grading system.

CONCLUSION

Although the pulmonary autograft requires a significantly longer operating time, this does not seem to affect early and medium-term outcome when compared with results obtained with aortic homografts. Continued patient evaluation is warranted, particularly with regard to evidence of valve degeneration and right ventricular function and arrhythmias in the long term.

Cross-sectional area index of left ventricular myocardium as a risk factor influencing early and late postoperative survival in aortic regurgitation

Late cardiogenic death after aortic valve replacement in aortic regurgitation is still a most important unresolved problem. We studied how the extent of cross-sectional area index (CSAI) relates to early and late cardiogenic deaths after aortic valve replacement (AVR) in aortic regurgitation with normal coronary artery. Forty-one patients were classified into two groups: Group I having CSAI greater than 20 cm2/m2 (18 patients), and Group II, in whom CSAI was less than 20 cm2/m2 (23 patients). All preoperative factors in patients with CSAI greater than or equal to 20 cm2/m2 showed poor values compared with patients with CSAI less than 20 cm2/m2 with a statistical difference of 63 +/- 6 versus 56 +/- 4% in cardiothoracic ratio, 72 +/- 9 versus 64 +/- 8 mm in diastolic dimension, 54 +/- 9 versus 43 +/- 7 mm in systolic dimension, 25 +/- 7 versus 32 +/- 6% in fractional shortening, 326 +/- 60 versus 209 +/- 63 ml/m2 in end-diastolic volume index, 177 +/- 52 versus 81 +/- 29 ml/m2 in end-systolic volume index, and 47 +/- 14 versus 58 +/- 5% in ejection fraction (mean +/- SD). In Group II, there were no postoperative cardiac deaths and no patient was subjected to intra-aortic balloon pumping (IABP). In contrast, in Group I, 17% died from postoperative low output syndrome and 33% were subjected to IABP. Concerning late deaths, there was no cardiac death in any CSAI patient with less than 20 cm2/m2; however, 22% of the patients with CSAI greater than or equal to 20 cm2/m2 died from cardiac causes.(ABSTRACT TRUNCATED AT 250 WORDS)

Preoperative left ventricular wall stress, ejection fraction, and aortic valve gradient as prognostic indicators in aortic valve stenosis

Patients with aortic valve stenosis (AS) and left ventricular (LV) dysfunction may dramatically improve after aortic valve replacement, but operative risk is high. In an earlier study, all patients with low preoperative wall stress and low ejection fraction, or with low aortic valve gradient, died or had persistent heart failure after operation. Because wall stress is difficult to calculate, we reassessed its effect and the effect of other preoperative characteristics on outcome in 66 consecutive catheterization patients with predominant aortic stenosis referred for valve replacement. Despite ejection fraction that was inordinately low compared with afterloading wall stress in nine patients, seven patients improved with surgery. All three patients with ejection fraction less than 20% improved after surgery. Two of three patients with mean aortic valve gradients of less than 30 mm Hg improved. Mortality was 33% in patients with mean gradient less than 30 mm Hg and 19% with mean gradient less than 50 mm Hg. In the 54 patients with calculated aortic valve areas of less than or equal to 0.8 cm2, 1 (2%) had continuing heart failure, while 6 of 12 (50%, P less than .01) patients with aortic valve areas of 0.9-1.2 cm2 had continued symptoms of or died of heart failure. Patients who died or failed to improve after operation were older (71 +/- 9 years) than those who improved (65 +/- 9 years, P = .02). We conclude that wall stress calculations do not predict which patients with aortic stenosis will benefit from aortic valve replacement and that poor left ventricular function and low mean aortic valve gradient do not absolutely preclude operation. On the other hand, low gradient, non-critical valve area, and advanced age are all relative contraindications to aortic valve replacement in aortic stenosis.

Degree of reversibility of left ventricular systolic dysfunction after aortic valve replacement for isolated aortic valve stenosis

To determine whether a low preoperative left ventricular (LV) ejection fraction (EF) returns to normal late after aortic valve replacement for aortic stenosis, 42 patients with critical aortic stenosis (valve area 0.7 cm2 or less), LV systolic dysfunction (EF 0.45 or less), angiographically normal coronary arteries, and no other significant valvular disease were studied at 10 to 84 months (mean 41 +/- 21) postoperatively. All patients survived aortic valve replacement and were discharged clinically improved. There were 4 late deaths; these patients were older (79 +/- 6 vs 64 +/- 13 years, p = 0.007) and had lower preoperative mean valve gradients (51 +/- 6 vs 68 +/- 23 mm Hg, p = 0.003) than late survivors. Of 23 survivors who returned for follow-up radionuclide angiography and Doppler echocardiography, 21 were asymptomatic. EF returned to normal (0.50 or more) in 14 patients (group 1) and remained low in 9 patients (group 2). Doppler peak prosthetic valve gradient was 24 +/- 8 mm Hg in group 1 and 25 +/- 10 mm Hg in group 2 (difference not significant). Six of the 9 patients in group 2 underwent early postoperative radionuclide imaging, and LVEF was normal in 4 (0.65 +/- 0.14 early vs 0.41 +/- 0.06 late, p = 0.02). Of 77 preoperative and intraoperative variables analyzed, only paroxysmal nocturnal dyspnea (0 of 14 vs 4 of 9, p = 0.01) distinguished group 1 from group 2. Thus, LVEF does not always normalize after aortic valve replacement for AS, implying impaired myocardial contractility.(ABSTRACT TRUNCATED AT 250 WORDS)

Afterload mismatch in aortic and mitral valve disease: implications for surgical therapy

In the management of patients with valvular heart disease, an understanding of the effects of altered loading conditions on the left ventricle is important in reaching a proper decision concerning the timing of corrective operation. In acquired valvular aortic stenosis, concentric hypertrophy generally maintains left ventricular chamber size and ejection fraction within normal limits, but in late stage disease function can deteriorate as preload reserve is lost and aortic stenosis progresses. In this setting, even when the ejection fraction is markedly reduced (less than 25%), it can improve to normal after aortic valve replacement, suggesting that afterload mismatch rather than irreversibly depressed myocardial contractility was responsible for left ventricular failure. Therefore, patients with severe aortic stenosis and symptoms should not be denied operation because of impaired cardiac function. In chronic severe aortic and mitral regurgitation, operation is generally recommended when symptoms are present, but whether to recommend operation to prevent irreversible myocardial damage in patients with few or no symptoms has remained controversial. In aortic regurgitation, left ventricular function generally improves postoperatively, even if it is moderately impaired preoperatively, indicating correction of afterload mismatch. Most such patients can be carefully followed by echocardiography. However, in some patients, severe left ventricular dysfunction fails to improve postoperatively. Therefore, when echocardiographic studies in the patient with severe aortic regurgitation show an ejection fraction of less than 40% (fractional shortening less than 25%) plus enlarging left ventricular end-diastolic diameter (approaching 38 mm/m2 body surface area) and end-systolic diameter (approaching 50 mm or 26 mm/m2), confirmation of these findings by cardiac catheterization and consideration of operation are advisable even in patients with minimal symptoms. In chronic mitral regurgitation, maintenance of a normal ejection fraction can mask depressed myocardial contractility. Pre- and postoperative studies in such patients have shown a poor clinical result after mitral valve replacement, associated with a sharp decrease in the ejection fraction after operation. This response appears to reflect unmasking of decreased myocardial contractility by mitral valve replacement, with ejection of the total stroke volume into the high impedance of the aorta (afterload mismatch produced by operation).(ABSTRACT TRUNCATED AT 400 WORDS)

Severe left ventricular dysfunction in critical aortic stenosis--reversal following aortic valve replacement

A case of aortic valve stenosis is reported with progressive left ventricular dysfunction demonstrated by radionuclide angiography. A gradient of 120 mmHg was present across the aortic valve. At the time of surgery, the patient was in severe cardiac failure with a left ventricular ejection fraction of 22%. Two months postoperatively, the patient was asymptomatic, and repeat radionuclide angiography demonstrated an ejection fraction of 93%. The reversible nature of this patient's ventricular dysfunction suggests that the cardiac failure was related to 'afterload mismatch' caused by the stenotic valve, rather than due to depressed contractility. The encouraging result in this patient reinforces the view that surgical intervention is warranted in some patients with critical aortic stenosis and extreme impairment of left ventricular function, and that the close relation between ejection fraction and operative survival may not hold true in aortic stenosis.

Left ventricular ejection fraction during cardiac surgery: a two-dimensional echocardiographic study

Although long-term effects have been studied, the immediate effect of surgery for acquired heart disease on left ventricular function is not well defined. Accordingly, 44 adults with acquired heart disease underwent intraoperative two-dimensional echocardiography with a gas-sterilized transducer before and immediately after cardiopulmonary bypass. Ejection fraction was measured by short-axis area change at the maximum left ventricular cross section (SAAC-EF) and also by a method using multiple sections. Correction of both mitral and aortic regurgitation produced a significant intraoperative decrease in ejection fraction from 0.49 +/- 19 (SD) to 0.32 +/- 0.16 (p less than .02) and from 0.41 +/- 0.13 to 0.30 +/- 0.17 (p less than .0005), respectively. Relief of aortic stenosis and mitral stenosis resulted in an intraoperative increase in ejection fraction from 0.45 +/- 0.10 to 0.55 +/- 0.09 (p less than .02) and from 0.41 +/- 0.05 to 0.50 +/- 0.07 (p less than .05), respectively. Ejection fraction after coronary artery bypass grafting was unchanged. Preload (end-diastolic area) was significantly decreased after correction of aortic regurgitation (p less than .02) but unchanged in other lesions. We conclude that (1) correction of pure mitral and aortic valvular lesions produces characteristic alterations in ejection fraction in the immediate postoperative period; (2) with the possible exception of patients with aortic regurgitation, the observed change in ejection fraction does not appear to reflect changes in preload; (3) noninvasive assessment of left ventricular function by two-dimensional echocardiography during cardiac surgery appears feasible and could provide data important for clinical decision making in the early postoperative period.

Timing of operation for chronic aortic regurgitation

Left ventricular systolic function is an important determinant of long-term prognosis in patients with chronic aortic regurgitation. Data from several centers, using invasive and noninvasive assessment of left ventricular function, indicate that long-term postoperative survival is excellent, even in symptomatic patients, if preoperative left ventricular systolic function is normal. The long-term postoperative results are significantly worse in symptomatic patients with preoperative left ventricular systolic dysfunction, many of whom appear to have irreversible left ventricular failure before the onset of symptoms and are at a risk of late postoperative death from congestive heart failure. However, within this high risk subgroup long-term prognosis is excellent for patients, despite left ventricular dysfunction, if preoperative exercise capacity is preserved. In these patients, left ventricular dysfunction is likely to be reversible after operation. Hence, all patients with left ventricular dysfunction at rest should undergo aortic valve replacement, even if severe symptoms and deterioration in exercise tolerance have not developed. Once exercise tolerance becomes limited in such patients, the likelihood of irreversible left ventricular dysfunction is increased, and long-term postoperative survival is threatened.

Assessment of chronic aortic valve disease in adults

Chronic aortic valve disease is often tolerated for a long period of time with little in the way of symptoms, but once symptoms develop, the downhill course is often rapid. Medical therapy may alleviate symptoms of congestive heart failure and angina, but does not alter the natural history of the disease. The recent advances of cardiac surgery have, however, considerably improved the prognosis of most patients. Some patients with aortic regurgitation, though, will develop progressive congestive heart failure despite aortic valve replacement. Others with severe aortic stenosis will die suddenly while awaiting surgery as will a small number who previously had been asymptomatic. The information that comes from cardiac catheterization as well as the non-invasive investigation of cardiological disease, greatly enhanced by the introduction of the echocardiogram, has provided the physician with a better understanding of the particular problems in question and, therefore, the potential to solve them. This article aims to review the means by which high-risk groups can be identified, in order that their outlook may be improved especially with respect to the timing of surgical intervention.

Current status of radionuclide imaging in valvular heart disease

In valvular heart disease, there is a different radionuclide angiographic pattern in each of three left-sided valve abnormalities: pressure overload (aortic stenosis), volume overload (aortic or mitral regurgitation) and inflow obstruction (mitral stenosis). In pressure overload, the left ventricle is usually normal in size or minimally dilated. The ejection fraction may be normal, increased or decreased. In volume overload, there is left ventricular dilatation with a normal or reduced ejection fraction at rest. Scans may be performed during exercise to unmask abnormalities of ventricular function not evident at rest. In inflow obstruction, left ventricular function is usually normal but may be depressed. Right ventricular function may be abnormal secondary to pulmonary hypertension. Radionuclide angiography in valvular heart disease evaluates the impact of the valve abnormality on cardiac chamber size and function, which is useful in managing the patient, in determining the prognosis and in evaluating the success of valve surgery. Thallium-2-1 imaging evaluates regional myocardial blood flow and cell integrity and can be used to assess associated coronary artery disease.

Cardiac hypertrophy: useful adaptation or pathologic process?

An extensive body of evidence supports the concept that cardiac hypertrophy and normal cardiac growth develop in response to increased hemodynamic loading and abnormal systolic and diastolic stresses at the myocardial fiber level. The pattern of hypertrophy reflects the nature of the inciting stress. Experimental studies indicate that if the stress is moderate, gradually applied, and the animal young and healthy, physiologic hypertrophy of muscle with normal contractility develops. In this circumstance, cardiac hypertrophy may be regarded as a useful adaptation to increased hemodynamic loading. When the inciting stress is severe, abruptly applied, or the animal old or debilitated, pathologic hypertrophy develops: in this circumstance, the cardiac muscle produced is abnormal and exhibits depressed contractility. Of particular clinical relevance is the intermediate situation which seems to develop in many patients with chronic left ventricular pressure-overload and perhaps also in left ventricular volume-overload. In this situation, chronic left ventricular pressure or volume overload is initially matched by adequate hypertrophy in the appropriate pattern. Eventually, in some patients, hypertrophy fails to keep pace with the hemodynamic overload so that a systolic stress imbalance occurs at the myocardial fiber level and left ventricular pump failure ensues. If this situation persists uncorrected, it is possible that the increasingly high wall stresses will convert physiologic to pathologic hypertrophy. The task of the clinician is to identify this intermediate stage and to correct the abnormal hemodynamic loading before the transition to pathologic hypertrophy becomes complete.