The Imaging Evaluation And Surgical Effect Analysis Of Enlarged Myocardial Resection For The Treatment Of Hypertrophic Obstructive Cardiomyopathy

Chapter 1The Efficacy of Image-based Evaluation for Performing the Extended Myectomy without Concomitant Mitral Procedure and the Assessment of Surgical OutcomesObjective:To analyze the efficacy of image-based evaluation for extended myectomy and the effectiveness of extended myectomy without the mitral procedure for abolishing mitral regurgitation in patients with hypertrophic obstructive cardiomyopathy(HOCM).Methods:Among the retrospected 431 consecutive HOCM patients who underwent surgical treatment and spared mitral procedure in our institution,done by one surgeon,image data,perioperative surgical results and follow-up data were collected to analyze and evaluate the surgical outcomes of mitral spared extended myectomy and the guidance of image data to surgical strategy.Results:The median resection length of patients with hypertrophic subaortic and midventricular septum(n=307,71.2%)was 45.0 mm(40,50),which was significantly longer than those with isolated basal septal hypertrophy(n=124,28.8%),35.0mm(34.3,40)(P=0.007);according to short axis of echo,the median resection width of patients with hypertrophy involving left ventricular anterior wall(n=219,50.8%)was significantly wider than those with isolated septal hypertrophy:[45.0 mm(40,45)vs 35.0 mm(30,40)](P=0.002).Fifty-three(12.3%)patients were found abnormal muscles directly inserted into anterior mitral leaflet.In this study,4(0.9%)died during a median follow-up time of 33 months,no one lost to follow-up.The median echocardiographic follow-up time was 6 months(3,12).The most recent evaluated echocardiographic data showed that the LVOT gradients was significantly decreased from(88.9±30.3)preoperatively to(12.1± 10.0)mmHg during follow-up(P<0.001);the number of patients with systolic anterior motion(SAM)of mitral leaflets decreased from 424(98.4%)preoperatively to 29(6.7%)during follow-up(P<0.001);and 300(67.3%)patients were combined with a moderate or severe mitral regurgitation before surgery,which decreased to 14(3.2%)at follow-up(P<0.001);The New York Heart Function level improved from 3.0±0.4 preoperatively to 1.1 ±0.4(P<0.001).Multivariate regression analysis showed that there was a high incidence of recurrence of moderate-to-severe mitral regurgitation during follow-up in patients with untreated anomalous muscles directly inserted into anterior mitral leaflet(odds ratio 40.453;95%confidence interval 8.533-191.777;P<0.001)and those with residual SAM during follow-up(odds ratio 14.643;95%confidence interval 2.071-103.528;P=0.007).Conclusions:Detailed preoperative echocardiographic and cardiac maganetic resonance evaluation help make surgical plan,determine the intraoperative resection extent of hypertrophic septal tissue,thereby eliminating LVOT obstruction.Sufficient resection to hypertrophied septal muscle and eliminating the potential anatomic factors that derive mitral regurgitation facilitate the abolition of LVOT obstruction and mitral regurgitation.Concomitant mitral procedures are rare necessary for patients without intrinsic mitral disease.Insufficient septal reduction therapy and the anomalous link nserted in the anterior mitral leaflet that cause centrally directed mitral regurgitation increase the incidence of posteropertive moderate-to-severe mitral regurgitation.Chapter 2Surgical Efficacy and Long-term Outcomes Analysis of the Extended Myectomy without a Concomitant Mitral Procedure for 221 Patients with Hypertrophic Obstructive CardiomyopathyObjective:This study aimed to provide the long-term outcomes of the extended myectomy without concomitant mitral procedure for patients with hypertrophic obstructive cardiomyopathy(HOCM),and predictors of the long-term outcomes.Methods:We retrospectively reviewed 221 consecutive HOCM patients who had undergone the extended myectomy with a spared mitral procedure by one surgeon in our institution.The primary endpoint was defined as hypertrophic cardiomyopathy(HCM)related death(sudden death,stroke related death,successful resuscitation and need for heart transplantation),the secondary endpoint was non-fatal stroke anecdote,syncope with unknown reason,rehospitalization for cardiac arrhythmia or congestive heart failure,the composite endpoint was the combination of primary and secondary endpoint.All patients were divided into 3 groups based on the morphological classification of left ventricular hypertrophy and their long-term outcomes were followed up by telephone questionnaire.Results:Hypertrophy limited to the basal septum,hypertrophy of the whole interventricular septum with and without an echocardiographic maximal septal thickness?3 0mm were respectively categorized as the "basal",the "whole ventricle<3 Omm"and the "whole ventricle>30mm" subtypes,which were presented in 79(35.7%),85(38.5%)and 57(25.8%)patients,respectively.There was no perioperative death.During the follow-up of 52.3±15.0 month after myectomy,6(2.8%)and 22(10.0%)patients met the primary end-point and secondary end-points,respectively.The maximal thickness of the ventricular septum,the left ventricular outflow tract pressure gradients,the patients with moderate-to-severe mitral regurgitation and with New York Heart Association functional classification III/IV were significantly improved:from 25.6±6.5mm to 17.5±5.5mm,92.1 ±37.4mmHg to 13.7±11.2mmHg,127(94.6%)to 5(2.3%)and from 196(88.7%)to 6(2.8%)respectively,P<0.001 respectively.Patients in subgroup "whole ventricle?30mm" showed a worse survival compared with the other two subtypes(P=0.029).A multivariable Cox proportional hazard model detected that preoperative non-sustained ventricular tachycardia(Hazard Ratio,8.390;95%confidential interval,1.132-62.206;P=0.037),iatrogenic ventricular septum defects after surgery(Hazard Ratio,13.958;95%confidence interval,2.551-76.367;P=0.002),moderate-to-severe mitral regurgitation found during follow up(Hazard Ratio,4.185;95%confidence interval,1.197-14.633;P=0.025)and postoperative atrial fibrillation(Hazard Ratio,7.293;95%confidence interval,2.760-19.274;P<0.001)were independent predictors of worse outcomes in HOCM patients undergoing extended myectomy without concomitant mitral procedure.Conclusion:Extended myectomy without concomitant mitral valve procedure is an effective and safe therapeutic alternative for HOCM patients with drug refractory symptoms,reaching an excellent long-term survival benefit.Patients with "whole ventricle?30mm" subtype showed worse survival compared with the other two subtypes.Preoperative non-sustained ventricular tachycardia,postoperative complete atrioventricular block,iatrogenic ventricular defect,moderate-to-severe mitral regurgitation and atrial fibrillation were independent predictors for composite endpoint events.Chapter 3The Surgical Strategy and Outcomes of Image-based Extended Myectomy for Midventricular ObstructionObjectives:Data on the efficacy of transaortic approach for patients with midventricular obstruction(MVO)was limited as it's considered out of reach for the lower level of obstruction.We sought to summarize reliable methods of preoperative echocardiographic evaluation and intraoperative surgical skills for MVO patients.Methods:Preoperative echocardiography images were read by echocardiographer and cardiac surgeon to detail and confirm the morphologic characteristics of hypertrophic septum.The distance between the aortic annulus and the distal part of disturbed flow,and the distance between the aortic annulus and the distal part of hypertrophic septum were respectively defined as the obstruction length(OL)and morphological hypertrophic length(MHL),which were firstly put forward and considered the minimal and maximal resection lengths during surgery to facilitate the preoperative evaluation process.The intra-observer variability of OL and MHL were remeasured on 2 separate occasions,and the interobserver variability of OL was remeasured by 2 readers.The surgical skill of en bloc resection was used to access the midventricular septum transaortically,and the surgical outcomes were analysed.Results:Three(7.5%)patients' MVO were caused by isolated hypertrophic posterior midventricular septum while the other 37(92.5%)by both the hypertrophic anterior and posterior midventricular septum.There was a median correlation between the OL and resection length,and a mild correlation between the MHL and resection length(r=0.532,P=0.002;r=0.365 P=0.007,respectively).The resection length was 7.23mm(-5.09,19.55)longer than OL to ensure a sufficient resection extent and 8.61mm(-22.5,4.82)shorter than MHL to avoid iatrogenic septal perforation.The intra-observer results of OL and MHL were both highly correlated(r=0.94,P<0.001;r=0.73,P<0.001,respectively),and no significant difference was found(p=0.136,P=0.073)as regard to the intra-observer variabilities;the interobserver results of OL were also highly correlated(r=0.91,P<0.001)and the variabilities were found no significant difference between 2 observers(P=0.092).Isolated transaortic myectomy was successfully conducted in 38(95.0%)patients,and another two(5.0%)with apical aneurysm and long OL(72mm)were treated by a combined transaortic and transapical myectomy.There were no early or late deaths,complete heart blocks or iatrogenic septal perforations in our study with a median follow-up time of 19 months(13,54).Instantaneous pressure gradients at the subaortic level decreased from 70.5 mmHg(51,89.5)preoperatively to 7.7 mmHg(6,11)(P<0.001)at the most recent evaluation,and at the midventricular level from 61.0 mmHg(42.8,85.5)to 8.5 mmHg(6.3,11.8)(P<0.001).In all patients,New York Heart Association functional classifications were improved,with a better haemodynamic status.Conclusions:Preoperative transthoracic echocardiogram helps make surgical strategy.The OL and MHL are objective parameters with low intra-and interobserver variability for determining resection length in surgery.The combination of preoperative echocardiographic evaluation and the en bloc resection skill make the transaortic myectomy reliable to eliminate the MVO,improving haemodynamic status and yielding satisfactory early outcomes in most MVO patients.Transapical myectomy should be considered for patients with long OL or apical aneurysm.