Concomitant Septal Myectomy in Patients Undergoing Aortic Valve Replacement for Severe Aortic Stenosis

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1 Circulation Journal Official Journal of the Japanese Circulation Society ORIGINAL ARTICLE Cardiovascular Surgery Concomitant Septal Myectomy in Patients Undergoing Aortic Valve Replacement for Severe Aortic Stenosis Ju Yong Lim, MD; Jin Oh Choi, MD; Jae Kon Oh, MD; Zhou Li; Soon J. Park, MD Background: Patients with severe aortic stenosis (AS) are often found to have asymmetric septal hypertrophy (ASH). With low sensitivity of echocardiography for detecting dynamic left ventricular outflow tract (LVOT) obstruction in severe AS, we adopted a routine intraoperative inspection of LVOT strategy for aortic valve replacement (AVR), and performed concomitant septal myectomy (CSM) as necessary. We sought to (1) evaluate surgical outcomes of CSM, (2) suggest preoperative echocardiographic parameters that correlate with findings of ASH, and (3) determine the predictors of CSM. Methods and Results: A single surgeon performed AVR for moderate-to-severe AS in 301 patients from 2007 to CSM was performed in 35 (11.6%) patients, resulting in AVR vs. AVR+CSM groups. Echocardiographic parameters, including the ratio of LVOT to aortic annular diameter (LVOT/AA), were compared. Mortality rate was comparable between groups (P=0.37). There were no postoperative complications related to CSM. The AVR+CSM group had a smaller LVOT/AA ratio (P=0.0012). The predictor of CSM was implanted valve size 21 mm (odds ratio 3.2, confidence interval , P=0.002). Conclusions: CSM can be performed safely at the time of AVR. The preoperative echocardiographic LVOT/AA ratio may help in detecting ASH. As an implanted valve size 21 mm was the only risk factor for CSM, careful assessment of LVOT is important in patients with a small aortic annulus. (Circ J 2015; 79: ) Key Words: Aortic valve replacement; Hypertrophic cardiomyopathy; Septal myectomy Asymmetric septal hypertrophy (ASH) was previously reported to be present in approximately 10% of cases of hemodynamically significant valvular aortic stenosis (AS). 1 This type of hypertrophy combined with severe AS can be easily overlooked at the time of aortic valve replacement (AVR), which can lead to residual left ventricular outflow track (LVOT) obstruction following AVR and a deteriorating postoperative course. 2,3 Although the indication for concomitant septal myectomy (CSM) at the time of AVR remains controversial, there have been suggestions supporting the necessity of direct inspection of LVOT at the time of AVR to assess the severity of ASH, 4 6 because of the low sensitivity of echocardiography for detecting dynamic LVOT obstruction in the setting of severe AS. We adopted the strategy of performing a direct visual and manual inspection of the LVOT in the operation room in all patients at the time of AVR and performed CSM in patients who were found to have ASH at the time of AVR, irrespective of their echocardiographic findings. Thus the aims of the current study were to: (1) evaluate the surgical outcomes of CSM, (2) suggest preoperative echocardiographic parameters that could predict the intraoperative finding of ASH requiring CSM, and (3) determine the other predictors of CSM at the time of AVR. Methods Study Population We adopted our intraoperative inspection strategy to detect ASH at the time of AVR in 2007 and until June 2012, inspection was performed in 301 patients by a cardiac surgeon (S.J.P.). We excluded patients who were diagnosed with hypertrophic obstructive cardiomyopathy or had known septal hypertrophy. CSM was performed in 35 patients on the basis of the intraoperative inspection (AVR+CSM group) and the other patients were grouped as AVR alone (n=266). The Institutional Review Board of the Mayo clinic approved this study (IRB no ). Received June 22, 2014; revised manuscript received November 3, 2014; accepted November 19, 2014; released online December 15, 2014 Time for primary review: 15 days Division of Cardiovascular Surgery (J.Y.L., S.J.P.), Division of Cardiology (J.O.C.), Division of Biostatistics (Z.L.), Mayo Clinic, Rochester, MN; Division of Cardiovascular Surgery, Case Western Reserve University, Cleveland, OH (S.J.P.), USA; Division of Cardiovascular Surgery, Asan Medical Center, Seoul (J.Y.L.); and Division of Cardiology, Samsung Medical Center, Seoul (J.O.C., J.K.O.), Korea Mailing address: Soon J. Park, MD, Chief, Division of Cardiovascular Surgery, Co-director, Harrington Heart and Vascular Institute, Case Western Reserve University, Euclid Ave, Cleveland, OH 44106, USA. soon.park@uhhospitals.org ISSN doi: /circj.CJ All rights are reserved to the Japanese Circulation Society. For permissions, please cj@j-circ.or.jp

2 376 LIM JY et al. 2.3±1.6 years. Statistical Analysis Statistical analyses were performed using SAS 9.13 (SAS Institute, Cary, NC, USA). Data are expressed as mean ± standard deviation for continuous variables and as numbers and percentages for categorical variables. Preoperative and postoperative measurements were compared using Student s pairedt test. Chi-square test or Fisher s exact test was used to compare the categorical variables and to assess statistical significance between the 2 groups. P<0.05 was considered statistically significant for all comparisons. Multivariate analysis was performed for the overall patient group using a Cox proportional hazards model. Variables were included in multivariate analysis if univariate significance was <0.05. The survival rate was calculated using Kaplan-Meier analysis. The follow-up period for each patient was calculated from the date of operation to the date of death or last contact. Figure 1. Echocardiographic measurement of left ventricular outflow tract/aortic annulus (LVOT/AA). A, LVOT; B, AA; LVOT/ AA=A/B. Operative Technique Median sternotomy was performed in all patients. After establishing standard extracorporeal circulation, cardiac arrest was induced with cold blood cardioplegia. Calcified native aortic valve (AV) was excised through oblique aortotomy and the aortic annulus (AA) was debrided carefully. Next, the LVOT was inspected visually and manually. If prominent septal bulging was detected, we performed standard septal myectomy avoiding conduction tissue injury. Prosthetic AV was placed in the annulus using standard technique. Echocardiographic Evaluation The pathology of the AV was preoperatively confirmed by transthoracic echocardiography (TTE). Severe AS was diagnosed with TTE by measuring the AV peak transvalvular pressure gradient, mean transvalvular pressure gradient and the AV orifice area in the systolic phase. Combined aortic regurgitation was graded from trivial (+1) to severe (+4) based on the regurgitant flow acceleration. Ventricular septal diameter and posterior free wall diameter were also measured preoperatively in the parasternal long-axis view. If the septal-free wall ratio was greater than 1.3, ASH was considered to be present. LVOT diameter at the level of 1 2 cm below the AA at end-diastole in the parasternal long-axis view (Figure 1) were measured retrospectively by an echocardiographer who was unaware of the surgical procedures and the LVOT diameter to AA ratio (LVOT/AA ratio) was calculated. As the LVOT was inspected only through the AA in the operating room, we hypothesized that the LVOT/AA ratio on preoperative echocardiography would correlate with the finding on intraoperative inspection of ASH requiring CSM. Patient Follow-up Last follow-up was obtained by social security death index, postal questionnaire and review of medical records. Follow-up was completed in 100%. Mean follow-up duration was Results The preoperative baseline characteristics of the patients are summarized in Table 1. There were more female patients in the AVR+CSM group (P=0.0026) and body surface area (BSA) was significantly smaller in the AVR+CSM group (P=0.0049). Except for these characteristics, there were no significant differences in the baseline characteristics of the 2 groups. Etiology of AS was mostly degenerative valve disease in both groups. Moderate-to-severe aortic regurgitation was concomitant in 74 patients in the AVR group and in 10 in AVR+CSM group. As shown in Table 2, aortic cross-clamp and total bypass times were not different between groups. The mean mass of the resected septal muscle for the patients in the AVR+CSM group was 1.03±0.6 g. Patients in the AVR+CSM group tended to have a smaller prosthetic valve compared with the AVR group (P=0.002). Concomitant procedures were performed in 65% of the patients in both groups. The most common concomitant procedure was coronary artery bypass grafting. There were 6 in hospital deaths, only in the AVR group, and the overall survival rate was comparable between groups (P=0.68) (Figure 2). The postoperative complication rate was comparable between groups in terms of re-exploration for bleeding, stroke, atrial fibrillation and renal failure. Complete atrioventricular block requiring permanent pacemaker occurred in only 3 patients in the AVR group, which did not show any statistical significance (P=0.83). Postoperative data from the last echocardiographic followup are shown in Table 3. Different from the preoperative echocardiographic findings in which LV end-systolic and enddiastolic dimensions (LVESD, LVEDD) were significantly smaller in AVR+CSM group, these dimensions became comparable postoperatively. Preoperative TTE Parameter (LVOT/AA) and Intraoperative Findings The LVOT/AA ratio in the diastolic phase in the AVR+CSM group was 0.81±0.11, which was significantly smaller than in the AVR group (0.89±0.09, P<0.001). This corroborated the high correlation between intraoperative inspection of the LVOT and the LVOT/AA value on preoperative TTE. Univariate and Multivariate Analysis for Risk Factor of CSM at the Time of AVR To determine the risk factors contributing to ASH requiring CSM at the time of AVR, univariate and multivariate analyses

3 Septal Myectomy With AVR 377 Table 1. Preoperative Characteristics of Patients With Severe AS Variable AVR group AVR+CSM group (n=266) (n=35) P value Age (years) 71.4± ± Female, n (%) 90 (33.8) 21 (60) * Body surface area, m ± ± * Hypertension 205 (77.0) 27 (77.1) 0.99 Diabetes mellitus 67 (25.2) 11 (31.4) 0.43 Hypercholesterolemia 40 (15.1) 1 (2.8) 0.57 Chronic lung disease 53 (19.7) 8 (22.8) 0.24 Chronic renal insufficiency 6 (2.3) 1 (2.8) 0.82 Peripheral vascular disease 31 (11.6) 7 (20) 0.16 Cerebrovascular accident 18 (19.1) 3 (8.6) 0.84 NYHA class III, IV 172 (64.7) 23 (65.7) 0.90 Etiology, n (%) 0.42 Degenerative 180 (67.7) 28 (80) Rheumatic 10 (3.76) 1 (2.8) Bicuspid 55 (20.7) 4 (11.4) LVEF (%) 55.4± ±13.3 <0.001 Aortic regurgitation 0.97 Trivial to mild 150 (56.4) 20 (57.1) Moderate to severe 74 (27.8) 10 (28.6) AV mean PG (mmhg) 47.1± ± LV mass 263.3± ± LV mass index 132.8± ± LVESD 36.1± ± * LVEDD 52.1± ± * *P<0.05. AS, aortic stenosis; AV, aortic valve; LV, left ventricle; LVEF, left ventricular ejection fraction; LVEDD, left ventricular end-diastolic dimension; LVESD, left ventricular end-systolic dimension; NYHA, New York Heart Association; PG, pressure gradient. Table 2. Operative and Postoperative Data of Patients Undergoing Surgical Treatment of AS Variable AVR group (n=266) AVR+CSM group (n=35) P value Cardiopulmonary bypass time (min) 111.2± ± Aortic cross-clamp time (min) 81.7± ± Implant valve size 21 mm 92 (34.5) 22 (62.8) 0.002* Concomitant procedures, n (%) 175 (65.8) 23 (65.7) 1.0 CABG Ascending aorta replacement 18 1 Mitral repair or replacement 17 5 Tricuspid repair or replacement 6 1 Early death, n (%) 6 (2.26) Late death, n (%) 52 (19.5) 6 (17.1) 0.73 Cardiac death 11(4.1) 3 (8.6) 0.42 Postoperative complications, n (%) Re-exploration for bleeding 20 (7.5) 1 (2.8) 0.31 AVB requiring PPM 3 (1.1) Stroke 8 (3.0) 2 (5.7) 0.34 Atrial fibrillation 72 (27.1) 10 (28.6) 0.85 Renal failure 18 (6.8) 2 (5.7) 0.81 *P<0.05. AVB, atrioventricular block; CABG, coronary artery bypass grafting; PPM, permanent pacemaker. Other abbreviation as in Table 1. for CSM. For the multivariate analysis, we excluded the LVOT/AA ratio, which was the strongest risk factor from the univariate analysis, because this variable was obtained retrowere performed. In the univariate analysis, sex, BSA, implant valve size 21 mm, preoperative LVESD and LVEDD, and the LVOT/AA ratio were found to be significant risk factors

4 378 LIM JY et al. Figure 2. Overall survival curve. AVR, aortic valve replacement; CSM, concomitant septal myectomy. Table 3. Postoperative Echocardiographic Data of Patients Undergoing Surgical Treatment of AS Variable AVR group AVR+CSM group P value LVEF 55.3± ± LV mass 231.1± ± LV mass index 115.3± ± LVESD 35.0± ± LVEDD 50.7± ± AV mean PG 16.7± ± TTE follow-up duration 24± ± TTE, transthoracic echocardiography. Other abbreviations as in Table 1. spectively to determine the preoperative echocardiographic parameter that correlates with the intraoperative inspection findings and may represent the presence of ASH. Multivariate analysis demonstrated that small implant valve size ( 21 mm) was the only risk factor for CSM (odds ratio 3.2, confidence interval , P=0.002). These findings are summarized in Table 4. The best cutoff point for predicting CSM at the time of AVR was LVOT/AA <0.7. Discussion Significant ASH in patients with severe AS occurs in approximately 10% of cases. 4,7 In our study, it was 11.6% (35 of 301 patients), which is comparable. Considering that the incidence of valvular AS is increasing and most common among valvular heart disease, 8 ASH combined with severe AS is not a rare condition. The strategy for managing ASH at the time of AV surgery remains controversial because there has not been an evaluation in a large cohort or in a randomized controlled trial. Some studies recommend no routine resection of ASH at the time of AV surgery because of possible CSM-related complications such as the need for permanent pacemaker or septal perforation. 9 or suggest CSM only in the limited cases of dynamic LVOT obstruction with septal anterior motion. 4 However, there are several reasons to advocate CSM with AVR. First of all, CSM could eliminate any potential subaortic gradient unmasked after AVR. In the setting of combined ASH with severe AS, operative relief of AS only will unmask residual subaortic stenosis by ASH and this can lead to deleterious clinical outcomes in the early and late postoperative period Also, septal hypertrophy and small LV cavity diameter, as shown in the present AVR+CSM group, may be related to poor outcome in the long term if it remains. 13 CSM also could promote significant LV regression after surgery and it is a relatively safe procedure with an acceptable, low risk. 6,14,15 As shown in our study results, CSM did not add any postoperative complications or contribute to prolonged operation time. However, we failed to demonstrate differences between groups in the current study regarding the echocardiographic variables estimating regression of LV hypertrophy

5 Septal Myectomy With AVR 379 Table 4. Univariate and Multivariate Analyses for Risk Factors of ASH Requiring CSM in Patients Undergoing Surgical Treatment of AS Variable Odds ratio 95% CI P value Univariate analysis Age Sex * BSA * Diabetes Hypertension Renal failure NYHA III, IV Trans AV PG Implanted valve size 21 mm LVEF * LV mass index LVESD * LVEDD IVS LVOT/AA <0.001* Multivariate analysis Implanted valve size 21 mm * *P<0.05. ASH, asymmetric septal hypertrophy; BSA, body surface area; CI, confidence interval; CSM, concomitant septal myectomy; IVS, interventricular septum; LVOT/AA, left ventricular outflow tract/aortic annulus. Other abbreviations as in Table 1. after surgery. Regarding regression of LV hypertrophy, Seo et al insist that LV diastolic dysfunction persists for up to 5 years after uneventful AVR because of inadequate or incomplete regression of LV hypertrophy, 16 and Di Tommaso et al reported the benefit of CSM on LV regression. 4 The mean follow-up duration in the present study was 2.3±1.6 years, so longer follow-up might be necessary to clarify this issue. The remaining issue associated with this surgical approach is how the coexistence of ASH with severe AS can be diagnosed precisely before AV surgery. Pressure gradient itself is not reliable for detecting coexisting subaortic obstruction in the setting of severe AS. 17 Despite recent technical advances with 3D echocardiography, 18 transesophageal echocardiography as well as TTE may fail to detect ASH preoperatively. Therefore, some authors suggest that both visual and manual inspection of LVOT intraoperatively are important and the decision on whether to perform CSM at the time of AVR should be made by the operator based on the inspection after excision of the native AV. 4,6,14 We began a strategy of inspecting the LVOT to detect ASH at the time of AV surgery in all patients regardless of their preoperative echocardiographic findings from 2007 onward. Based on the intraoperative findings, we performed CSM. The inspection could be subjective, so we aimed to find some echocardiographic parameters that correlated and corroborated the surgeon s inspection findings. As shown in our study results, the preoperative LVOT/AA ratio strongly correlated with the intraoperative finding of a requirement for CSM. This suggests that the diagnostic acuity of TTE regarding ASH combined with severe AS may improve by using this parameter. Study Limitations First, this study was a retrospective observational study, not a randomized controlled study. So the comparison between groups could be biased with potential compounding factors. Second, the study population was relatively small, partly be- cause of strict inclusion criteria, which were adopted to improve the homogeneity of the study population and to verify the strategy of our surgical approach to ASH with severe AS. Also, the follow-up duration was relatively short because the intraoperative inspection strategy was introduced only 5 years prior. Longer follow-up with a larger population may provide enough statistical power to demonstrate differences in LV regression between CSM+AVR and AVR alone as previously reported. Conclusions Intraoperative findings of ASH in patients undergoing AVR for moderate-to-severe AS do not seem to be uncommon, and CSM for ASH can be performed without additional risks. Preoperative echocardiographic measurement of the LVOT/ AA ratio may be helpful in corroborating the intraoperative finding of ASH. As the implanted valve size 21 mm was the only risk factor for CSM, a careful assessment of the LVOT is important in patients with a small AA and small LVOT/AA ratio (LVOT/AA <0.7) at the time of AVR. None related to this study. Disclosures References 1. Maron BJ, Clark CE, Henry WL, Fukuda T, Edwards JE, Mathews EC, et al. Prevalence and characteristics of disproportionate ventricular septal thickening in patients with acquired or congenital heart diseases: Echocardiographic and morphologic findings. Circulation 1977; 55: Parker DP, Kaplan MA, Connolly JE. Coexistent aortic valvular and functional hypertrophic subaortic stenosis: Clinical, physiologic and angiographic aspects. Am J Cardiol 1969; 24: Wigle ED, Sasson Z, Henderson MA, Ruddy TD, Fulop J, Rakowski H, et al. Hypertrophic cardiomyopathy: The importance of the site and the extent of hypertrophy (Review). Prog Cardiovasc Dis 1985;

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