Ann Thorac Surg 1998;65:1634-1638
© 1998 The Society of Thoracic Surgeons
Original articles: cardiovascular
Reversibility of Cardiac Dysfunction After Valve Replacement in Elderly Patients With Severe Aortic Stenosis
Masafumi Natsuaki, MDa,
Tsuyoshi Itoh, MDa,
Shinji Tomita, MDa,
Kozo Naito, MDa
a Department of Thoracic and Cardiovascular Surgery, Saga Medical School, Saga, Japan
Accepted for publication January 25, 1998.
Address reprint requests to Dr Natsuaki, Department of Thoracic and Cardiovascular Surgery, Saga Medical School, Nabeshima, 5-1-1 Nabeshima, Saga City, Saga 849, Japan
Background. The role of aortic valve replacement for aortic stenosis has not been fully defined in terms of the postoperative reversibility of cardiac dysfunction and pulmonary hypertension in elderly patients.
Methods. Cardiac function, assessed by radioisotope ventriculography and catheterization data, was evaluated before and after operation, and their results were compared between preoperative and postoperative data in each group of younger patients (<69 years, group I, n = 29) and elderly patients (70 years, group II, n = 21).
Results. One month postoperatively the peak ejection rate determined by radioisotope ventriculography improved significantly in comparison with the preoperative value in elderly patients (preoperatively, 228 ± 38 versus postoperatively, 319 ± 116% end-diastolic volume per second, p < 0.05), although their preoperative peak ejection rate was severely depressed. The postoperative peak filling rate of the elderly group was not completely reversible to almost normal value, whereas that of the younger group was completely reversible. Early diastolic peak filling rate (one-third peak filling rate) was not reversible in both two groups. Pulmonary hypertension in the elderly patients was reversible to postoperative almost normal pulmonary artery pressure despite the severity of aortic stenosis (systolic pulmonary artery pressure preoperatively, 37 ± 16 mm Hg versus postoperatively, 25 ± 5 mm Hg, p < 0.02; diastolic pulmonary artery pressure preoperatively, 15 ± 6 mm Hg versus postoperatively, 10 ± 4 mm Hg, p < 0.05).
Conclusions. Both cardiac dysfunction, reflected by reduction of peak ejection rate, and pulmonary hypertension in elderly patients with severe aortic stenosis were reversed, reaching almost normal values 1 month after operation.
Left ventricular (LV) hypertrophy in patients with aortic stenosis is an adaptive process that compensates for high intracavitary pressure and reduces systolic wall stress. After aortic valve replacement (AVR) for aortic stenosis, elderly patients with severe concentric hypertrophy appear to have more postoperative complications than younger patients. One cause of postoperative morbidity is thought to be postoperative LV dysfunction attributable to the presence of excessive LV hypertrophy and consequent depressed myocardial performance of the aging heart. The depressed ejection performance or diastolic dysfunction of the hypertrophied heart due to aortic stenosis is caused by an increased LV afterload or elevated LV stiffness. Previous studies demonstrated that elderly patients more than 70 years old with excessive LV hypertrophy suffered greater morbidity after AVR for aortic stenosis or regurgitation than younger patients . Such increased mortality and morbidity in elderly patients may be related to postoperative LV diastolic dysfunction due to excessive LV hypertrophy, inadequate myocardial protection during global ischemic arrest, and depressed myocardial performance of the aging heart. Recently, surgical results for elderly patients with aortic stenosis have been improving. However, the role of AVR for aortic stenosis has not been fully defined on postoperative reversibility of cardiac dysfunction or pulmonary hypertension. The evaluation of the postoperative reversibility of cardiac dysfunction may be useful in deciding the type of surgical indication for elderly patients with severe aortic stenosis.
The aim of this clinical study was to elucidate the reversibility of the postoperative LV function evaluated by radioisotope ventriculography in elderly patients with aortic stenosis, and examine whether cardiac dysfunction of the aging heart with pulmonary hypertension is reversible after AVR.
Patients and methods
The cardiac function of 50 patients who underwent AVR for aortic stenosis was evaluated using radioisotope ventriculography, catheterization data, and echocardiography. Patients with atrial fibrillation or other valvular disease were excluded from this study. During a period of 5 years 50 consecutive patients were classified into two groups according to their age at the time of operation. Those in the younger group (group I, n = 29) were aged 69 years or younger, and those in the elderly group (group II, n = 21) were aged 70 years and older. Cardiac function was evaluated pre- and postoperatively by gated equilibrium blood pool angiography performed with the patient at rest in a supine position. The data were processed using Scintipack 1200 (Shimadzu, Kyoto, Japan). Regions of interest were depicted over the left ventricle and background, and a time-activity curve obtained after background correction represented the relative LV volume changes with time. Several parameters of ejection fraction (EF), first third ejection fraction (1/3 EF), and first third filling fraction (1/3 FF) were measured from the time-activity curve. The peak ejection rate (PER) and peak filling rate (PFR) determined by calculating the first derivative of the time-activity curve were expressed as the change in LV counts per second at the peak ejection or peak filling, and the values were normalized for the number of LV counts at end-diastole (%EDV/s) . The early diastolic PFR was obtained during the first third diastole (1/3 PFR). Control data were obtained from subjects without cardiac disease (control data: EF, 0.64 ± 0.03; 1/3 EF, 0.25 ± 0.03; 1/3 FF, 0.65 ± 0.13; PER, 330 ± 31%EDV/s; PFR, 290 ± 42%EDV/s; 1/3 PFR, 289 ± 42%EDV/s; n = 10).
Left and right cardiac catheterization with fluid-filled catheters was performed, and cardiac output was determined using either the Fick principle or the thermodilution method. The preoperative pulmonary arterial pressure (PAP), PA wedge pressure (PAWP), right atrial and LV pressures were measured, and the peak pressure gradient between the left ventricle and ascending aorta was obtained from the catheterization data. The Gorlin equation was used to calculate the aortic valve area . The postoperative parameters of cardiac function, determined as described above, were compared retrospectively with the corresponding preoperative data of groups I and II, and the ratios of postoperative PAP to preoperative PAP were compared between the two groups.
M-mode, two-dimensional, and Doppler echocardiography were performed using commercially available equipment (Toshiba, Tokyo, Japan). The LV wall thickness and dimensions were obtained from the M-mode recordings and the LV mass was calculated using the formula of Devereux and colleagues [6, 7]. The pressure gradient between the left ventricle and the ascending aorta was obtained with Doppler echocardiography and the modified Bernoulli equation.
Aortic valve replacement was performed using a standard cardiopulmonary bypass technique and moderate systemic hypothermia. Cardioplegia was induced by multidose intermittent blood cardioplegic administration through the aortic root and directly into the coronary ostia, and a vent was used routinely to decompress the left ventricle. The aortic annulus was debrided carefully to remove all calcific debris. A mechanical valve (St. Jude Medical valve; St. Jude Medical, St. Paul, MN) was used for all the patients. Three patients underwent Nicks procedure for surgical annular enlargement. The mechanical valve sizes of groups I and II did not differ (Table 1), and interrupted mattress 2-0 Ethibond (Ethicon, Somerville, NJ) sutures with pledgets were used for valve implantation. No patients died during hospitalization.
Continuous variables are expressed as means ± standard deviation. Differences between continuous variables of the two groups were analyzed using Students unpaired t test, and the ratios of postoperative value to preoperative value were compared between the two groups using the unpaired t test. Comparisons of preoperative and postoperative data were performed using Students paired t test for paired samples in each group. Dichotomous variables were compared using 2 analysis. Differences with p values of less than 0.05 were considered significant.
There were no significant differences between groups I and II with respect to the preoperative catheterization data (cardiac index and PAWP). Preoperative aortic valve orifice area of group II was smaller than that of group I (Table 1). The pressure gradient between the left ventricle and the ascending aorta of group II (elderly patients) was steeper than that of group I (younger patients), although the peak pressure gradients of the two groups did not differ significantly. The systolic and diastolic PAPs of group II were slightly higher than those of group I (Table 2).
The echocardiographic preoperative data showed that there were no significant differences between the LV end-diastolic dimensions, LV end-systolic dimensions, thickness of the interventricular septum, thickness of the posterior wall, and LV mass of the two groups.
Of the preoperative parameters determined by radioisotope ventriculography, the EF and the PER of group II were significantly lower than those of group I (Table 3). There were no significant differences among the other parameters (PFR, 1/3 FF, and 1/3 PFR) in the two groups.
One month postoperatively, the PERs of groups I and II had improved strikingly in comparison with the preoperative values (Table 3 and Fig 1). The 1-month postoperative diastolic PFR of group II was not completely reversible to normal value, although the postoperative PFR of group I showed a complete reversibility after operation (Table 3). The postoperative early diastolic PFRs (1/3 PFRs) of both groups did not differ from the preoperative values, and remained low. The 1-month postoperative 1/3 FFs of both groups were significantly lower than the preoperative values, but neither the postoperative early diastolic PFRs nor the 1/3 FFs of the two groups differed significantly.
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Fig 1. Preoperative cardiac dysfunction in group I (n = 29) and group II (n = 21) was noticed in peak ejection rate (PER) as a systolic function. Postoperative peak ejection rate significantly improved in comparison with preoperative value, and was reversible to almost normal values in groups I and II (paired t test).|
Postoperative hemodynamic data were obtained immediately after the patient was admitted to the intensive care unit. The postoperative systolic and diastolic PAPs were lower than the preoperative values in the two groups, although the diastolic PAP of group II was higher than that of group I. Neither the postoperative cardiac indices nor the durations of mechanical ventilation support of the two groups differed significantly, and no patient died in the hospital in the two groups.
The catheterization data obtained 1 month after operation revealed that postoperative cardiac indices of the two groups slightly improved and the PAWPs of the two groups significantly decreased in comparison with preoperative values (Table 2). Postoperative systolic PAPs of groups I and II significantly decreased in comparison with preoperative values. Postoperative diastolic PAP of group II significantly decreased in comparison with preoperative value, and reached an almost normal value even in elderly patients (Fig 2). The ratios of postoperative PAP to preoperative PAP were not different between the two groups (Table 2).
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Fig 2. Preoperative systolic and diastolic pulmonary artery pressures (PAP) of group II (n = 21) were higher than those of group I (n = 29). Postoperative systolic pulmonary artery pressures of groups I and II significantly decreased in comparison with preoperative data (paired t test), and were reversible to almost normal values 1 month after operation. The postoperative diastolic pulmonary artery pressure of group II significantly decreased in comparison with preoperative value, and was reversible to almost normal value.|
The afterload mismatch in patients with aortic stenosis has been demonstrated to be responsible for the reduction in systolic ejection performance [8, 9]. One month after AVR for elderly patients, the PER of an ejection performance parameter improved in comparison with the preoperative value, and was reversible to almost normal value probably due to correction of the afterload mismatch despite the severity of their aortic stenosis and strikingly depressed PER before operation. In contrast, the EFs of the elderly and younger patients did not always improve in the early postoperative period. A previous study showed that the left ventricular ejection fraction had improved by the time of late follow up after operation in patients with impaired EF .
The preoperative and postoperative early diastolic PFRs of both the elderly and younger patients in our study were impaired. This impairment of early diastolic function may have been induced by prolonged relaxation of the hypertrophic myocardium. The reduction of early diastolic PFRs shows postoperative diastolic dysfunction that LV viscoelastic property in aortic stenosis had not improved at the early postoperative stage, although hypertrophy itself had regressed. Postoperative PFR during whole diastolic phase of the elderly patients did not return to normal values during the early period after AVR, whereas that of the younger patients did. Postoperatively, both the PFR and early diastolic PFR of the elderly patients were lower than those of the younger patients. A previous study showed that a reduced PFR and reduced early diastolic PFR, demonstrated by a radionuclide method, reflected diastolic dysfunction in hypertensive patients and in the aging heart . A reduced early diastolic PFR reflects a parameter of diastolic dysfunction due to impaired LV filling, which is affected by the extent of myocardial hypertrophy resulting from aortic stenosis or increased myocardial stiffness . In our study, postoperative PFR throughout diastole and the early diastolic PFR both remained lower in the elderly patients than in the younger patients. A low PFR associated with a high diastolic PAP in elderly patients may reflect diastolic dysfunction due to relatively increased interstitial fibrosis or the viscoelastic property with increased stiffness of the hypertrophic myocardium before and immediately after operation . This diastolic dysfunction may be normalized by the change of viscoelastic property late after valve replacement .
Diastolic dysfunction in patients with aortic stenosis is caused by increased diastolic stiffness and prolonged relaxation, and the PAP increases as a result of the elevation in the LV end-diastolic pressure and the impairment of LV filling. In our study, the preoperative diastolic PAP of elderly patients was elevated more strikingly than that of the younger patients. The postoperative diastolic PAP of the elderly patients in the intensive care unit was much more elevated than that of the younger patients. This finding suggests that a higher postoperative diastolic PAP in elderly patients is probably attributable to a relatively high degree of preoperative myocardial stiffness and postoperative myocardial edema. However, the pulmonary hypertension of the elderly patients was reversible about 1 month after operation, and the diastolic PAP was almost normal. Previous studies showed that pulmonary hypertension in patients with aortic stenosis had no measurable adverse effect on operative mortality . However, Tracy and colleagues  demonstrated that postoperative diastolic PAP in the intensive care unit slightly increased in comparison with preoperative values in patients with mild pulmonary hypertension, and was not reversible to almost normal diastolic PAP in patients with mild or severe pulmonary hypertension. This hemodynamic study by Tracy and colleagues  was examined in the intensive care unit, and was not examined as to the age of patients at operation and late follow-up study. Few reports have been published on the postoperative reversibility of pulmonary hypertension in elderly patients.
The significance of the predictors of operative mortality in patients with aortic stenosis may relate to complications of coronary heart disease, or the presence of a small mechanical valve [18, 19]. Concomitant coronary artery bypass grafting was found to be a significant predictor of surgical risk for aortic stenosis in previous reports [20, 21]. In our clinical study, good reversibility of cardiac dysfunction was obtained about 1 month after operation in our elderly patients, probably because few patients underwent concomitant coronary artery bypass grafting and the elderly patients who underwent AVR using a small mechanical prosthesis had a small body surface area.
Left ventricular hypertrophy accompanied by aortic stenosis or hypertension leads to diastolic dysfunction by abnormal LV relaxation and filling, and is associated with poor clinical outcome . The LV diastolic performance declines progressively with aging , and elderly patients with aortic stenosis are likely to be complicated by a depressed PFR. We found that the postoperative PFR was not completely reversible, failing to reach normal values in elderly patients after AVR.
In conclusion, cardiac dysfunction, reflected by a depressed PER, and pulmonary hypertension were almost completely reversible, even in elderly patients, about 1 month after AVR. However, diastolic dysfunction by depressed PFR or 1/3 PFR was not completely reversible after operation in elderly patients. Aortic valve replacement is indicated for elderly patients with severe aortic stenosis, because cardiac dysfunction was almost reversible after operation even in elderly patients.
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