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ORIGINAL ARTICLE
Year : 2016  |  Volume : 29  |  Issue : 3  |  Page : 662-667

Surgical aortic valve replacement for severe stenosis with low ejection fraction and low transvalvular gradient


1 Cardiothoracic Surgery Department, Faculty of Medicine, Menoufia University, Menoufia, Egypt
2 Cardiothoracic Surgery Department, Faculty of Medicine, Cairo University, Cairo, Egypt

Date of Submission14-May-2015
Date of Acceptance22-Jun-2015
Date of Web Publication23-Jan-2017

Correspondence Address:
Mohamed G Hagag
60 E-Gomhoria Street, Quesna, Menoufia, 32631
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/1110-2098.198751

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  Abstract 

Objectives
Evaluation of early outcomes of surgical aortic valve replacement (AVR) for patients with isolated severe aortic stenosis (AS) associated with left ventricular (LV) dysfunction and low transvalvular gradient.
Background
AS is the most common valvular heart disease in elderly people, with an incidence of 2-7% in the population above 65 years. Sudden death may be the first presentation for severe AS. AVR is the effective treatment for AS. Benefits versus mortality of surgical AVR is still controversial in patients who presented with severe AS associated with LV dysfunction and low gradient.
Materials and methods
Between October 2012 and January 2015, this multicenter prospective observational study included 20 consecutive patients who presented with isolated severe AS (valve area <1 cm 2 ), associated with LV dysfunction (ejection fraction <40%), and a low mean gradient (<40 mmHg). All patients underwent conventional surgical AVR using cardiopulmonary bypass. LV function improvement was evaluated, 6 months postoperatively for all survivors, by transthoracic Echo.
Results
Our study included 14 male and six female patients with a mean age of 64.75 years and a mean EUROSCORE II of 1.62. All participants underwent conventional AVR with a cardiopulmonary bypass mean time of 113.3 min and a mean cross-clamp time of 69.6 min. The postoperative course involved a mean ICU stay of 3.6 days but, unfortunately, with two (10%) cases requiring reopening and mortality occurring in  two (10%) cases. Among the 18 survivors, we detect statistically significant improvements in LV dimensions and systolic function in the postoperative follow-up Echo after 6 months.
Conclusion
Despite the high mortality rate (10%), surgical AVR is still the gold standard management for severe AS even in the risky subgroup of patients with LV dysfunction and low gradient, due to its effect in the LV function improvement.

Keywords: aortic diseases, aortic valve stenosis, heart valve diseases


How to cite this article:
Dokhan AL, Gomaa MM, Abd El-Aziz ME, Hagag MG. Surgical aortic valve replacement for severe stenosis with low ejection fraction and low transvalvular gradient. Menoufia Med J 2016;29:662-7

How to cite this URL:
Dokhan AL, Gomaa MM, Abd El-Aziz ME, Hagag MG. Surgical aortic valve replacement for severe stenosis with low ejection fraction and low transvalvular gradient. Menoufia Med J [serial online] 2016 [cited 2020 Apr 8];29:662-7. Available from: http://www.mmj.eg.net/text.asp?2016/29/3/662/198751


  Introduction Top


Valvular heart disease presents often in older patients, frequently in association with multiple comorbidities and frailty, and the risks of intervention are  increasing [1] . Aortic stenosis (AS) is a common form of heart disease. The prevalence of AS has been estimated to be 0.3-0.5% in the general population and to be markedly higher in the elderly, with a prevalence estimate of 2-7% in individuals over 65 years of age [2] . Degenerative calcific AS is the most common cause of AS in industrialized nations, but in developing countries in Africa, Asia, and South America, rheumatic valve disease remains a common cause of  AS [3] .

For optimal clinical decision making, a comprehensive diagnostic evaluation of patients with aortic valve disease requires assessment of the morphology of the valve, severity of the valve lesion, size of the aorta, systemic arterial afterload, impact on left ventricular (LV) size and function, consequences of abnormal LV function and hemodynamics on pulmonary artery pressures, right ventricular size and function, and coexistent disorders. Echocardiographic data should be integrated with the clinical features of a patient, other imaging, and, when needed, catheterization findings in order to approach AS in a systematic manner [4] .

It is well recognized that severe AS carries a poor prognosis if left untreated. Despite this recognition, many patients are inappropriately denied surgery for its perceived risk [3] . In practice, a considerable number of patients with severe AS are managed medically for reasons such as advanced age, high procedural risk, and multiple comorbidities, although current guidelines give a class IA recommendation on surgical treatment in patients with symptomatic severe AS [5] .

The objective of our study was to evaluate the early outcome, including morbidities and mortalities, of surgical aortic valve replacement (AVR) for patients with isolated severe AS associated with LV dysfunction and low transvalvular gradient.


  Materials and methods Top


After approval of the study proposal by the Menoufia Ethics Committee, this prospective observational study was conducted between October 2012 and January 2015 in multiple centers including Cairo University Hospitals, New Kasr El Aini  Teaching Hospital, and Nasser Institute.

Twenty consecutive patients with isolated severe AS [aortic valve area (AVA) <1 cm 2 ], low ejection fraction (EF) (<40%), and low mean transvalvular gradient (<40 mmHg) were included in the study. Patients with coronary artery disease, mitral or tricuspid valve disease, and redo cases were excluded from the study. Each patient was subjected to full history taking, thorough clinical examination, preoperative laboratory and radiological investigations, and full transthoracic echocardiographic assessment including measurement of left ventricular end-diastolic diameter (LVEDD), left ventricular end-systolic diameter (LVESD), EF, AVA, and mean transvalvular pressure gradient.

The predicted operative mortality was calculated preoperatively using the online calculator of the European System for Cardiac Operative Risk Evaluation (EUROSCORE II). All patients were operated under general anesthesia, with conventional median sternotomy incision; cardiopulmonary bypass was instituted through aortoatrial cannulation and right superior pulmonary vein venting. After antegrade cardioplegia, aortotomy was performed, followed by excision of the calcified aortic valve and annular decalcification. In our study, nine mechanical valves and 11 biological valves were inserted with variable sizes as one valve was 19 size, eight valves were 21 size, and 11 valves were 23 size. The new aortic valve was implanted using interrupted nonabsorbable sutures. Closure of aortotomy, weaning from bypass, and closure of sternotomy were performed sequentially, and then the patient was transferred to ICU sedated and intubated.

We followed patients in the hospital until recovery of acceptable physical activity before being discharged home. Follow-up was carried out in the outpatient clinic at 1 week, 1 month, 3 months, and 6 months postoperatively, with transthoracic echocardiographic assessment at the 6-month visit to assess changes in LV dimensions and systolic function.

All preoperative, operative, postoperative, and outpatient follow-up data were collected. Quantitative variables were expressed as mean ± SD, whereas qualitative data were expressed as number (n), ratio, or percentage (%) according to relevance. Statistical significance was tested using an IBM-compatible computer and IBM SPSS statistics version 19 (California, USA).  The significance of quantitative variables was tested using the paired Student's t-test. We considered probability values less than 0.05 as statistically significant.


  Results Top


The studied group included 20 consecutive patients. [Table 1] illustrates the preoperative data. Classic demographics of severe AS patients were observed as the mean age was 64.75 ± 3.8 years. Fourteen patients were male, representing 70% of our patients. The mean BMI was 31.04 ± 3.7. Patients presented with other comorbidities as four (20%) cases were diabetic, 13 (65%) cases were hypertensive, four (20%) cases were dyslipidemic, and four (20%) cases were smokers.
Table 1 Preoperative characteristics


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The classic triad of AS symptoms of chest pain, dyspnea, and syncope was noted in our study as all study patients were symptomatic at the time of presentation to healthcare services with the predominant symptom being angina-like chest pain in 10 (50%) cases. Other symptoms included dyspnea in three (15%) cases, syncope in three (15%) cases, and atrial fibrillation (AF) in four (20%) cases. The mean EUROSCORE II value for our patients was 1.62 ± 1.35.

[Table 2] illustrates the preoperative Echo findings of our study patients. We found a mean LVEDD of 7.97 ± 0.93, a mean LVESD of 6.75 ± 0.82, a mean EF of 30.85 ± 6.12, and a mean AVA of 0.73 ± 0.13.
Table 2 Preoperative Echo


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[Table 3] demonstrates the operative and postoperative data. All patients underwent conventional surgical AVR with the important operative indicators being a cardiopulmonary total bypass mean time of 113.3 ± 30 min and an aortic cross-clamp mean time of 69.6 ± 16.3 min. [Table 2] includes the operative and postoperative findings of our study.
Table 3 Operative and postoperative data


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The postoperative ICU course was remarkable, with a mean postoperative ventilation time of 21.15 ± 24.15 min and a total ICU mean stay of 3.6 ± 1.4 days. During the ICU stay, four (20%) cases with a persistently low cardiac output required an intra-aortic balloon pump support for a period ranging from 30 to 63 h. Unfortunately, two (10%) cases required reopening for high drainage. Five (25%) patients manifested postoperative arrhythmias including AF and heart block, one of them required permanent pacemaker implantation, and three (15%) patients developed wound infection that responded well to antibiotics; however, one patient required vacuum suction for his gapped infected wound and two (10%) patients died postoperatively: one of them died on the first postoperative day after reopening for high drainage and the other one on the fifth postoperative day with a persistent low cardiac output despite maximum support.

The 6-month follow-up Echo for our 18 survivors was interesting, and showed improvement in LV dimensions and systolic function with a mean LVEDD of 7.57 ± 0.61 compared with a preoperative mean LVEDD of 7.93 ± 0.83, indicating a highly significant statistical relationship (P = 0.004). In addition, the relationship between the mean postoperative LVESD of 6.2 ± 0.51 and the preoperative LVESD of 6.68 ± 0.76 was  also statistically significant (P = 0.000). The most important finding with regard to all patients and investigators was the improvement in the mean postoperative EF of 36.22 ± 6.72 when compared with the mean preoperative EF of 31.6 ± 5.7; the relationship was found to be statistically significant (P = 0.008) as shown in [Table 4].
Table 4 Left ventricular response to aortic valve replacement


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  Discussion Top


Patients with severe AS and impairment of ventricular function constitute a high-risk group for AVR. They are also a challenging group because of their heterogeneous response. Ventricular hypertrophy is also a negative factor. The association of both factors may influence the surgical outcome [6] . Therefore, the question arises as to whether the LV can return to normal dimensions and how rapidly myocardial hypertrophy and LV dysfunction regress after AVR [7] .

Nearly a quarter of the severe AS patients have a reduced LVEF and a substantial subset have a low transvalvular gradient despite normal LVEF. Although the American College of Cardiology/American Heart Association guidelines recommend AVR for severe AS patients with LV dysfunction, the recommendations are not clear in those with a low transvalvular gradient [8] .

Hence, the management of patients with classical low-flow, low-gradient AS (valve area <1 cm 2 , EF <40%, mean gradient <40 mmHg) is more difficult. If depressed EF is predominantly caused by excessive afterload (afterload mismatch), LV function usually improves after surgery. Conversely, improvement in LV function after AVR is uncertain if the primary cause is scarring due to extensive myocardial infarction or cardiomyopathy [9] .

Our study aimed at evaluating the surgical AVR as the treatment option for the risky group of patients with severe AS associated with LV function and a low gradient. In addition, we need to evaluate whether patients will derive benefits that can outweigh the procedure's risks.

The mean age of the patients in our study was 64.75 ± 3.8 years. This is in agreement with Levy et al. [10] who reported, in their study on 217 consecutive patients with severe AS, low EF, and low gradient, a mean age of 71 ± 8 years. In addition, Tribouilloy et al. [11] reported, in their study on 81 patients, a mean age of 71 ± 10 years. This can be explained by the process of calcific degeneration of AS that progresses more with increasing age to reach the reported incidence of AS of 2-7% in the population above 65 years of age.

With regard to sex distribution of AS in our study, 14 patients were male, representing 70% of the study population. Again, this is similar to that reported by Levy et al. [10] and Tribouilloy et al. [11] , who reported 77 and 73% male patients, respectively. This agreement of studies upon male sex predominance of AS was the reason for many researchers to suggest that AS is similar to atherosclerosis as they share the same risk factors of old age, male sex predominance, and higher prevalence of diabetes mellitus and dyslipidemia.

The mean BMI in our study was 31.04 ± 3.7, which is higher than that in the study of Tribouilloy et al. [11] , who noted a mean BMI of 25 ± 3. This slight difference can be attributed to the cultural difference between eastern nations with low activity at old age in contrast to western nations with continued daily physical activity, keeping their BMI within normal ranges. In addition, this high BMI in our patients with impaired ventricular function shed some light on the effect of elevated BMI on cardiac functions. Abdelazez et al. [12] noted in their study on the effect of obesity on ventricular function that 'Impairment of cardiac function has been reported to be correlated with BMI and duration of obesity, with most studies reporting abnormal diastolic function without consistent association with systolic dysfunction'.

Comorbidities of patients was reported by Abe et al. [13] in their study on 130 patients with AS as 81% hypertensive, 31% diabetic, 62% dyslipidemic, and 28% smokers. In our study, we reported nearly similar data as 65% hypertensive, 20% diabetic, 20% dyslipidemic, and 20% smokers for their higher incidence of dyslipidemia in the study of Abe et al. [13] . In addition, Tribouilloy et al. [11] reported a lower incidence of hypertensive patients (24%), but similar incidence of diabetes (15%). These risk factors shared in the studies, further emphasize the degenerative theory of AS that in many ways resemble atherosclerosis but its distribution differs from region to region according to the quality of life, dietary habits, and daily physical activity.

Our patients' presentation was angina-like chest pain in 10 (50%) cases, dyspnea in three (15%) cases, syncope in three (15%) cases, and AF in four (20%) cases. Levy et al. [10] reported in their study 27% cases with AF. These symptoms represent the classic triad of AS symptoms of chest pain, dyspnea, and syncope, with arrhythmias occasionally being the main presentation or defining  pathophysiology in syncope.

Levy et al. [10] reported a mean EUROSCORE for their patients of 8.9 ± 2.7, which was higher than our patients' calculated mean EUROSCORE of 1.62 ± 1.35. This large difference may be attributed to our inclusion criteria of electively operated isolated AS in contrast to patients included in the study of Levy et al. [10] with other cardiac procedures including emergency operations and coronary artery bypass grafting.

Preoperative Echo confirmed our selection criteria of severe AS as mean AVA 0.73 ± 0.13 and low EF with mean 30.85 ± 6.12. In addition, LV hypertrophy and enlargement was noted, with mean LVEDD 7.97 ± 0.93 and mean LVESD 6.75 ± 0.82.

Conventional surgical AVR through median sternotomy was performed on all our patients with a mean total cardiopulmonary bypass time of 113.3 ± 30, which is similar to the mean time reported by Carrascal et al. [14] of 106 ± 34.5 and by Levy et al. [10] of 105 ± 56. Whereas the mean cross-clamp time was 69.6 ± 16.3, which is similar to that reported by Levy et al. [10] (73 ± 34), it was lower than that reported by Carrascal et al. [14] (80 ± 28). This increased cross-clamp time in other studies may be explained by concomitant procedures other than AVR performed to their patients. In addition, the total bypass time may be longer, indicating a longer reperfusion time to support the dysfunction myocardium and achieving better myocardial perfusion with a consequently better postoperative response.

Postoperatively, the mean ICU stay was 3.6 ± 1.4. Wang et al. [15] reported, in their study on 35 patients who AVR before 2011, a similar mean ICU stay of 3.6 ± 6, but in the same study, they reported 33 patients to have undergone AVR after 2011, with a mean ICU stay of 1.4 ± 0.8. This implies that with more experience in care for these critical patients and advances in medical technology, the ICU stay that we achieved in our study can decrease further as Wang et al. [15] reported this difference before and after  2011.

Wang et al. [15] noticed, in their study, an incidence of postoperative morbidity due to reopening in three (8.6%) cases: two (6.1%) cases before and one after 2011,   respectively. We obtained similar results of two (10%) cases of reopening. Concerning wound infection, Wang et al. [15] reported one (2.9%) case and no cases for patients operated before and after 2011, respectively. Unfortunately, we got three (15%) cases of wound infection, which is higher than Wang et al. [15] and even higher than Carrascal et al. [14] report of two (0.2%) wound infection cases, indicating that more care should be directed toward infection control policy in our centers and personal hygiene of our patients to get these rates back to comparable studies.

One (5%) patient required a permanent pacemaker out of five (25%) patients who manifested postoperative arrhythmias in our study. This is in agreement with Wang et al., [15] who reported two (5.7%) cases requiring a permanent pacemaker before and two (6.1%) cases after 2011,   respectively.

This can be claimed to be due to possible injury to the conductive system during the valve decalcification process, which surgeons usually perform with caution to minimize such incidences as much as  possible.

Mortality rate was 10% despite the low mean EUROSCORE of 1.62 ± 1.35 preoperatively in our study, which was similar to that of Carrascal et al. [14] who reported a rate of 8% and lower than that reported by Levy et al. [10] of 16%. This rate, despite its annoying effect for new patients being referred for surgery, is still an accepted outcome for the risky group of patients. The reported rate in previous studies as noted by Levy et al. [10] is 11-21%. In conclusion, mortality rates of AVR are improving with time as our study and that of the study of Carrascal et al. [14] reported lower rates in recent years. However, we noticed in our study a misleading underestimation of the EUROSCORE, which was much lower than the actual mortality rate, which makes this score questionable and requiring more justification.

The occurrence of previous comorbidities and a high mortality rate during the initial phase of our study led to dissatisfaction with the results of the study. This changed drastically after follow-up of survivors with improvement of their symptoms, increasing exercise tolerance, which was superadded by the 6-month follow-up Echo results, with documented improvement in LV dimensions and systolic function.

In our series, the mean LVEDD of 7.57 ± 0.61 compared with the preoperative mean LVEDD of 7.93 ± 0.83, showed a highly significant statistical relationship (P = 0.004). In addition, the mean postoperative LVESD of 6.2 ± 0.51 compared with the preoperative LVESD of 6.68 ± 0.76 yielded a highly significant statistical relationship (P = 0.000). The most important finding with regard to all patients and investigators was the improvement in EF as a mean postoperative EF of 36.22 ± 6.72 when compared with a mean preoperative EF of 31.6 ± 5.7, also yielding a statistically significant relationship (P = 0.008).


  Conclusion Top


Improvement in LV dimensions and systolic function outweigh the reported comorbidities for surgical AVR for isolated severe AS with low EF (<40) and a low gradient (<40 mmHg). The reported high mortality rate of 10%, despite the misleading calculated EUROSCORE, makes the use of these scores questionable and necessitates further larger studies to justify their use. A review of previous studies clarified that the high mortality rate in our study is lower than that of previous studies. This requires more attention in selecting patients and auditing for all operative and postoperative steps to achieve a lower mortality. At last, the improved quality of life and LV function postoperatively emphasize the fact that surgical AVR as the effective standard treatment for severe AS.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
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