A Pilot Study Using Machine Learning Algorithms and Wearable Technology for the Early Detection of Postoperative Complications After Cardiothoracic Surgery.

OBJECTIVE: To evaluate whether a machine learning algorithm (i.e. the "NightSignal" algorithm) can be used for the detection of postoperative complications prior to symptom onset after cardiothoracic surgery. SUMMARY BACKGROUND DATA: Methods that enable the early detection of postoperative complications after cardiothoracic surgery are needed. METHODS: This was a prospective observational cohort study conducted from July 2021 to February 2023 at a single academic tertiary care hospital. Patients aged 18 years or older scheduled to undergo cardiothoracic surgery were recruited. Study participants wore a Fitbit watch continuously for at least 1 week preoperatively and up to 90-days postoperatively. The ability of the NightSignal algorithm-which was previously developed for the early detection of Covid-19-to detect postoperative complications was evaluated. The primary outcomes were algorithm sensitivity and specificity for postoperative event detection. RESULTS: A total of 56 patients undergoing cardiothoracic surgery met inclusion criteria, of which 24 (42.9%) underwent thoracic operations and 32 (57.1%) underwent cardiac operations. The median age was 62 (IQR: 51-68) years and 30 (53.6%) patients were female. The NightSignal algorithm detected 17 of the 21 postoperative events a median of 2 (IQR: 1-3) days prior to symptom onset, representing a sensitivity of 81%. The specificity, negative predictive value, and positive predictive value of the algorithm for the detection of postoperative events were 75%, 97%, and 28%, respectively. CONCLUSIONS: Machine learning analysis of biometric data collected from wearable devices has the potential to detect postoperative complications-prior to symptom onset-after cardiothoracic surgery.

Rationale and Design of the Randomized Controlled Trial of New Oral Anticoagulants Versus Warfarin for Post Cardiac Surgery Atrial Fibrillation: The NEW-AF Trial.

OBJECTIVE: This manuscript describes the rationale and design of a randomized, controlled trial comparing outcomes with Warfarin vs Novel Oral Anticoagulant (NOAC) therapy in patients with new onset atrial fibrillation after cardiac surgery. BACKGROUND: New onset atrial fibrillation commonly occurs after cardiac surgery and is associated with increased rates of stroke and mortality. in nonsurgical patients with atrial fibrillation, NOACs have been shown to confer equivalent benefits for stroke prevention with less bleeding risk and less tedious monitoring requirements compared with Warfarin. However, NOAC use has yet to be adopted widely in cardiac surgery patients. METHODS: The NEW-AF study has been designed as a pragmatic, prospective, randomized controlled trial that will compare financial, convenience and safety outcomes for patients with new onset atrial fibrillation after cardiac surgery that are treated with NOACs versus Warfarin. RESULTS: Study results may contribute to optimizing the options for stroke prophylaxis in cardiac surgery patients and catalyze more widespread application of NOAC therapy in this patient population. CONCLUSIONS: The study is ongoing and actively enrolling at the time of the publication. The trial is registered with clinicaltrials.gov under registration number NCT03702582.

Risk factors for ischemic gastrointestinal complications in patients undergoing open cardiac surgical procedures: A single-center retrospective experience.

BACKGROUND: Ischemic gastrointestinal complications (IGIC) following cardiac surgery are associated with high morbidity and mortality and remain difficult to predict. We evaluated perioperative risk factors for IGIC in patients undergoing open cardiac surgery. METHODS: All patients that underwent an open cardiac surgical procedure at a tertiary academic center between 2011 and 2017 were included. The primary outcome was IGIC, defined as acute mesenteric ischemia necessitating a surgical intervention or postoperative gastrointestinal bleeding that was proven to be of ischemic etiology and necessitated blood product transfusion. A backward stepwise regression model was constructed to identify perioperative predictors of IGIC. RESULTS: Of 6862 patients who underwent cardiac surgery during the study period, 52(0.8%) developed IGIC. The highest incidence of IGIC (1.9%) was noted in patients undergoing concomitant coronary artery, valvular, and aortic procedures. The multivariable regression identified hypertension (odds ratio [OR] = 5.74), preoperative renal failure requiring dialysis (OR = 3.62), immunocompromised status (OR = 2.64), chronic lung disease (OR = 2.61), and history of heart failure (OR = 2.03) as independent predictors for postoperative IGIC. Pre- or intraoperative utilization of intra-aortic balloon pump or catheter-based assist devices (OR = 4.54), intraoperative transfusion requirement of >4 RBC units(OR = 2.47), and cardiopulmonary bypass > 180 min (OR = 2.28) were also identified as independent predictors for the development of IGIC. CONCLUSIONS: We identified preoperative and intraoperative risk factors that independently increase the risk of developing postoperative IGIC after cardiac surgery. A high index of suspicion must be maintained and any deviation from the expected recovery course in patients with the above-identified risk factors should trigger an immediate evaluation with the involvement of the acute care surgical team.

Concomitant carotid endarterectomy and cardiac surgery does not decrease postoperative stroke rates.

OBJECTIVE: The timing of operative revascularization for patients with concomitant carotid artery stenosis and coronary artery disease remains controversial. We examined the Society of Thoracic Surgeons (STS) Adult Cardiac Surgery Database to evaluate the association of combined carotid endarterectomy (CEA) and coronary artery bypass grafting (CABG) with postoperative outcomes. METHODS: All patients undergoing CABG with known carotid stenosis of >80% were identified from 2011 to 2016. Individuals were stratified by use of cardiopulmonary bypass and whether a concomitant CEA was performed at the time of CABG. Multivariate logistic regression was used to model the probability of combined CABG and CEA. The resulting propensity scores were used to match individuals on the basis of clinical and operative characteristics to evaluate primary (30-day mortality and in-hospital transient ischemic attack and stroke) and secondary (STS morbidity composite events and length of stay) end points, with P < .05 required to declare statistical significance. RESULTS: After propensity score matching, 994 off-pump CABG patients (497 CABG only and 497 CABG-CEA) and 5952 on-pump CABG patients (2976 CABG only and 2976 CABG-CEA) were identified. For patients who received on-pump operations, those undergoing CABG-CEA had no observed difference in rate of in-hospital stroke (odds ratio [OR], 0.93; 95% confidence interval [CI], 0.72-1.21; P = .6), higher incidence of STS morbidity composite events (OR, 1.15, 95% CI, 1.01-1.31; P = .03), longer length of stay (7.0 [interquartile range, 5.0-9.0] days vs 6.0 [interquartile range, 5.0-9.0] days; P < .005), and no observed difference in 30-day mortality (OR, 1.28; 95% CI, 0.97-1.69; P = .08) compared with those undergoing CABG only. For off-pump procedures, CABG-CEA patients had no observed difference in rate of in-hospital stroke (OR, 0.80; 95% CI, 0.37-1.69; P = .56) compared with those undergoing CABG only. CONCLUSIONS: Whereas the differences are relatively small, these data suggest that a combined CABG-CEA approach is unlikely to provide significant stroke reduction benefit compared with CABG only. However, comparison with staged approaches merits further investigation.

Preoperative penicillin allergy testing in patients undergoing cardiac surgery.

BACKGROUND: Cefazolin is a first-line prophylactic antibiotic used to prevent surgical site infections (SSIs) in cardiac surgery. Patients with a history of penicillin allergy often receive less effective second-line antibiotics, which is associated with an increased SSI risk. OBJECTIVE: To describe the impact of preoperative penicillin allergy evaluation on perioperative cefazolin use in patients undergoing cardiac surgery. METHODS: We performed a retrospective cohort study of patients with a documented penicillin allergy who underwent cardiac surgery at the Massachusetts General Hospital from September 2015 to December 2018. We describe penicillin allergy evaluation assessment and outcomes. We evaluated the association between preoperative penicillin allergy evaluation and first-line perioperative antibiotic use using a multivariable logistic regression model. RESULTS: Of 3802 cardiac surgical patients, 510 (13%) had a documented penicillin allergy; 165 (33%) were referred to allergy and immunology practitioners. Of 160 patients (31%) who underwent penicillin allergy evaluation (ie, penicillin skin testing and, if results were negative, an amoxicillin challenge), 154 (97%) were found not to have a penicillin allergy. Patients who underwent preoperative penicillin allergy evaluation were more likely to receive the first-line perioperative antibiotic (92% vs 38%, P < .001). After adjusting for potential confounders, patients who underwent preoperative penicillin allergy evaluation had higher odds of first-line perioperative antibiotic use (adjusted odds ratio, 26.6; 95% CI, 12.8-55.2). CONCLUSION: Integrating penicillin allergy evaluation into routine preoperative care ensured that almost all evaluated patients undergoing cardiac surgery received first-line antibiotic prophylaxis, a critical component of SSI risk reduction. Further efforts are needed to increase access to preoperative allergy evaluation.

Increasing donor sequence number is not associated with inferior outcomes in lung transplantation.

BACKGROUND: Donor sequence number (DSN) represents the number of recipients to whom an organ has been offered. The impact of seeing numerous prior refusals may potentially influence the decision to accept an organ. We sought to determine if DSN was associated with inferior posttransplant outcomes. METHODS: Using the United Network for Organ Sharing database, a retrospective analysis was performed on 22 361 patients who received a lung transplant between 2005 and 2017. Patients were grouped into low DSN (1-24, n = 16 860) and high DSN (>24, n = 5501) categories. Baseline characteristics and posttransplant outcomes were analyzed. An institutional subgroup was also analyzed to compare rates of primary graft dysfunction (PGD) posttransplant. RESULTS: The DSN ranged from 1 to 1735 (median, 7; interquartile range, 2-24). A total of 18 507 recipients received an organ with at least one prior refusal. Recipients of donors with a higher DSN were older (58 vs 55 years; P < .01) but had lower lung allocation scores (43.5 vs 47.5; P < .01). On adjusted analysis, high DSN was not associated with increased mortality (hazard ratio, 0.99; 95% confidence interval, 0.94-1.04; P = .77). There was no difference in the incidence of graft failure (P = .37) or retransplantation (P = .24). Recipient subgroups who received donors with an increasing DSN >50 and >75 also demonstrated no difference in mortality when compared with a low DSN (P = .86 and P = .97). There was no difference in PGD for patients with a low vs a high DSN at any time posttransplant. CONCLUSIONS: DSN is not associated with increased mortality in patients undergoing lung transplantation and should not negatively influence the decision to accept a lung for transplant.

Description and Impact of a Comprehensive Multispecialty Multidisciplinary Intervention to Decrease Opioid Prescribing in Surgery.

INTRODUCTION: Diversion of excess prescription opioids contributes to the opioid epidemic. We sought to describe and study the impact of a comprehensive departmental initiative to decrease opioid prescribing in surgery. METHODS: A multispecialty multidisciplinary initiative was designed to change the culture of postoperative opioid prescribing, including: consensus-built opioid guidelines for 42 procedures from 11 specialties, provider-focused posters displayed in all surgical units, patient opioid/pain brochures setting expectations, and educational seminars to residents, advanced practice providers, residents and nurses. Pre- (April 2016-March 2017) versu post-initiative (April 2017-May 2018) analyses of opioid prescribing at discharge [median oral morphine equivalent (OME)] were performed at the specialty, prescriber, patient, and procedure levels. Refill prescriptions within 3 months were also studied. RESULTS: A total of 23,298 patients were included (11,983 pre-; 11,315 post-initiative). Post-initiative, the median OME significantly decreased for 10 specialties (all P values < 0.001), the percentage of patients discharged without opioids increased from 35.7% to 52.5% (P < 0.001), and there was no change in opioids refills (0.07% vs 0.08%, P = 0.9). Similar significant decreases in OME were observed when the analyses were performed at the provider and individual procedure levels. Patient-level analyses showed that the preinitiative race/sex disparities in opioid-prescribing disappeared post-initiative. CONCLUSION: We describe a comprehensive multi-specialty intervention that successfully reduced prescribed opioids without increase in refills and decreased sex/race prescription disparities.

Pain management and safety profiles after preoperative vs postoperative thoracic epidural insertion for bilateral lung transplantation.

OBJECTIVE: Thoracic epidural analgesia provides effective pain control after lung transplantation; however, the optimal timing of placement is controversial. We sought to compare pain control and pulmonary and epidural morbidity between patients receiving preoperative vs postoperative epidurals. METHODS: Institutional records were reviewed for patients undergoing a bilateral lung transplant via a bilateral anterior thoracotomy with transverse sternotomy incision between January 2014 and January 2017. Pain control was measured using visual analog scale pain scores (0-10). Pulmonary complications included a composite of pneumonia, prolonged intubation, and reintubation/tracheostomy. RESULTS: Among 103 patients, 72 (70%) had an epidural placed preoperatively and 31 (30%) had an epidural placed within 72 hours posttransplant. There were no differences in the rates of cardiopulmonary bypass (3% vs 0%, P = 0.59); however, patients with a preoperative epidural were less likely to be placed on extracorporeal membrane oxygenation intraoperatively (25% vs 52%, P = 0.01). Pain control was similar at 24 hours (1.2 vs 1.7, P = 0.05); however, patients with a preoperative epidural reported lower pain scores at 48 (1.2 vs 2.1, P = 0.02) and 72 hours posttransplant (0.8 vs 1.7, P = 0.02). There were no differences in primary graft dysfunction (42% vs 56%, P = 0.28), length of mechanical ventilation (19.5 vs 24 hours, P = 0.18), or adverse pulmonary events (33% vs 52%, P = 0.12). No adverse events including epidural hematoma, paralysis, or infection resulted from epidural placement. CONCLUSION: Preoperative thoracic epidural placement provides improved analgesia without increased morbidity following lung transplantation.

Early structural valve deterioration and reoperation associated with the mitroflow aortic valve.

BACKGROUND: Structural valve deterioration (SVD) is a known limitation of bioprosthetic valves. Recent reports have suggested a concerning rate of early SVD in patients receiving a Mitroflow aortic bioprosthesis. We therefore compared the incidence of SVD and SVD requiring reoperation among patients receiving a Mitroflow versus a common contemporary bioprosthesis. METHODS: A retrospective cohort analysis was performed on 592 patients receiving a Mitroflow aortic bioprosthesis at our institution between 2010 and 2014. Patients were matched 1:1 using a coarsened exact matching algorithm with patients receiving a Carpentier-Edwards Magna Ease aortic bioprosthesis (Edwards Lifesciences, Irvine, CA) during the same period. The incidence of SVD (defined as a mean transprosthetic gradient ≥30 mmHg or moderate to severe intraprosthetic regurgitation), reoperation for SVD, and cumulative survival were compared between prosthesis types. RESULTS: The cumulative incidence of SVD at 5 years for all patients receiving a Mitroflow aortic bioprosthesis was 16% (13-21%) and 5% underwent reoperation for SVD. Implantation of a Mitroflow valve was associated with an increased risk of SVD compared to the comparator valve (hazard ratio [HR] 2.59 [1.69-3.98], P < 0.01). Older age had a protective effect against SVD (HR 0.95 [0.93-0.96], P < 0.01). Patients who received a Mitroflow valve had reduced long-term survival compared to those who received a comparator valve (P = 0.03). CONCLUSION: The Mitroflow aortic bioprosthesis is associated with increased rates of early SVD and reoperation for valvular dysfunction as well as reduced survival compared to a contemporary valve. Enhanced clinical and echocardiographic follow-up is advisable after Mitroflow implantation.

Impact of Left Ventricular to Mitral Valve Ring Mismatch on Recurrent Ischemic Mitral Regurgitation After Ring Annuloplasty.

BACKGROUND: In ischemic mitral regurgitation (IMR), ring annuloplasty is associated with a significant rate of recurrent MR. Ring size is based on intertrigonal distance without consideration of left ventricular (LV) size. However, LV size is an important determinant of mitral valve (MV) leaflet tethering before and after repair. We aimed to determine whether LV-MV ring mismatch (mismatch of LV size relative to ring size) is associated with recurrent MR in patients with IMR after restrictive ring annuloplasty. METHODS: Patients with moderate or severe IMR from the 2 Cardiothoracic Surgical Trials Network IMR trials who received MV repair were examined at 1 year after surgery. Baseline LV size was assessed by LV end-diastolic dimension and LV end-systolic dimension (LVESd). LV-MV ring mismatch was calculated as the ratio of LV to ring size (LV end-diastolic dimension/ring size and LVESd/ring size). RESULTS: At 1 year after ring annuloplasty, 45 of 214 patients with MV repair (21%) had moderate or greater MR. In univariable logistic regression analysis, larger LVESd (P=0.02) and LVESd/ring size (P=0.007) were associated with recurrent MR. In multivariable models adjusted for age, sex, baseline LV ejection fraction, and severe IMR, only LVESd/ring size (odd ratio per 0.5 increase, 2.20; 95% confidence interval, 1.05-4.62; P=0.038) remained significantly associated with 1-year MR recurrence. CONCLUSIONS: LV-MV ring size mismatch is associated with increased risk of MR recurrence. This finding may be helpful in guiding choice of ring size to prevent recurrent MR in patients undergoing MV repair and in identifying patients who may benefit from MV repair with additional subvalvular intervention or MV replacement rather than repair alone. CLINICAL TRIAL REGISTRATION: URL:http://clinicaltrials.gov. Unique identifiers: NCT00806988 and NCT00807040.

Combined papillary muscle sling and ring annuloplasty for moderate-to-severe secondary mitral regurgitation.

BACKGROUND: There is a 30-60% incidence of recurrent mitral regurgitation (MR) after mitral valve annuloplasty (Ring) for secondary MR. A concomitant papillary muscle sling (Ring+Sling) may improve valve repair by providing a more physiologic geometry of the mitral apparatus. METHODS: We retrospectively identified 58 consecutive patients with moderate-to-severe secondary MR who underwent a Ring+Sling repair, between March 2008 and May 2015. A Ring+Sling consisted of combined annuloplasty and papillary muscle approximation, utilizing a 4-mm polytetrafluoroethylene graft placed around the base of each muscle. Comparison of echocardiographic variables with patients who underwent a Ring only was performed utilizing 2:1 propensity-score matching (Ring+Sling = 34; Ring = 17). RESULTS: The baseline demographics were similar between the groups. The mean time to follow-up echocardiogram was 10.1 months (range 0.25-42 months). At follow-up, a Ring+Sling repair was associated with a lower mitral valve tenting height (p = 0.005), mitral valve tenting area (p = 0.009), and interpapillary muscle distance (p = 0.001); a smaller posterior leaflet tethering angle (p = 0.003); and a greater leaflet coaptation length (p = 0.002), when compared with Ring only. Recurrence of moderate or greater MR occurred significantly less in the Ring+Sling group (14.7%), as compared with Ring only (35.3%) (p < 0.001). Finally, actuarial survival at three years was 87% for Ring+Sling, and 82% for Ring only (p = 0.49). CONCLUSIONS: A Ring+Sling for secondary MR results in favorable changes in the mitral valve apparatus geometry, and is associated with less MR recurrence in the early postoperative period. Longer-term follow-up is needed to assess its durability and effects on left ventricular remodeling and survival.

Blending three repair techniques in a case of complex mitral valve endocarditis.

In a 39-year-old male with mitral valve endocarditis, after 6 weeks of intravenous antibiotics, echocardiography confirmed multiple vegetations on both leaflets, a flail posterior leaflet flail and contained perforation of the anterior leaflet in a windsock-like morphology. All vegetations, diseased and ruptured chords and the windsock-like contained rupture of the anterior leaflet were carefully resected via a right minithoracotomy and with femoral cannulation. Three repair techniques were blended to reconstruct the valve: (1) A large, infected portion of the prolapsing posterior leaflet was resected in a triangular fashion, and the edges were re-approximated using continuous 5-0 polypropylene sutures. (2) The anterior leaflet defect was repaired with a circular autologous pericardial patch that had been soaked in glutaraldehyde. (3) A set of artificial chords for P2 was created using CV-4 polytetrafluoroethylene sutures and adjusted under repeated saline inflation. A 38-mm Edwards Physio-I annuloplasty ring was implanted. The artificial chords were adjusted again after annuloplasty and then tied. Transoesophageal echocardiography (TEE) confirmed the absence of residual mitral regurgitation and systolic anterior motion and a mean pressure gradient of 3 mmHg. The patient was discharged after 5 days with a peripherally inserted central catheter to complete an additional 4 weeks of intravenous antibiotics and had an uneventful recovery.

Neochordal Goldilocks: Analyzing the biomechanics of neochord length on papillary muscle forces suggests higher tolerance to shorter neochordae.

OBJECTIVE: Estimating neochord lengths during mitral valve repair is challenging, because approximation must be performed largely based on intuition and surgical experience. Little data exist on quantifying the effects of neochord length misestimation. We aimed to evaluate the impact of neochord length on papillary muscle forces and mitral valve hemodynamics, which is especially pertinent because increased forces have been linked to aberrant mitral valve biomechanics. METHODS: Porcine mitral valves (n = 8) were mounted in an ex vivo heart simulator, and papillary muscles were fixed to high-resolution strain gauges while hemodynamic data were recorded. We used an adjustable system to modulate neochord lengths. Optimal length was qualitatively verified by a single experienced operator, and neochordae were randomly lengthened or shortened in 1-mm increments up to ±5 mm from the optimal length. RESULTS: Optimal length neochordae resulted in the lowest peak composite papillary muscle forces (6.94 ± 0.29 N), significantly different from all lengths greater than ±1 mm. Both longer and shorter neochordae increased forces linearly according to difference from optimal length. Both peak papillary muscle forces and mitral regurgitation scaled more aggressively for longer versus shorter neochordae by factors of 1.6 and 6.9, respectively. CONCLUSIONS: Leveraging precision ex vivo heart simulation, we found that millimeter-level neochord length differences can result in significant differences in papillary muscle forces and mitral regurgitation, thereby altering valvular biomechanics. Differences in lengthened versus shortened neochordae scaling of forces and mitral regurgitation may indicate different levels of biomechanical tolerance toward longer and shorter neochordae. Our findings highlight the need for more thorough biomechanical understanding of neochordal mitral valve repair.

Building a successful minimally invasive mitral valve repair program before introducing the robotic approach: The Massachusetts General Hospital experience.

Background: Patients with mitral valve prolapse (MVP) requiring surgical repair (MVr) are increasingly operated using minimally invasive strategies. Skill acquisition may be facilitated by a dedicated MVr program. We present here our institutional experience in establishing minimally invasive MVr (starting in 2014), laying the foundation to introduce robotic MVr. Methods: We reviewed all patients that had undergone MVr for MVP via sternotomy or mini-thoracotomy between January 2013 and December 2020 at our institution. In addition, all cases of robotic MVr between January 2021 and August 2022 were analyzed. Case complexity, repair techniques, and outcomes are presented for the conventional sternotomy, right mini-thoracotomy and robotic approaches. A subgroup analysis comparing only isolated MVr cases via sternotomy vs. right mini-thoracotomy was conducted using propensity score matching. Results: Between 2013 and 2020, 799 patients were operated for native MVP at our institution, of which 761 (95.2%) received planned MVr (263 [34.6%] via mini-thoracotomy) and 38 (4.8%) received planned MV replacement. With increasing proportions of minimally invasive procedures (2014: 14.8%, 2020: 46.5%), we observed a continuous growth in overall institutional volume of MVP (n = 69 in 2013; n = 127 in 2020) and markedly improved institutional rates of successful MVr, with 95.4% in 2013 vs. 99.2% in 2020. Over this period, a higher complexity of cases were treated minimally-invasively and increased use of neochord implantation ± limited leaflet resection was observed. Patients operated minimally invasively had longer aortic cross-clamp times (94 vs. 88 min, p = 0.001) but shorter ventilation times (4.4 vs. 4.8 h, p = 0.002) and hospital stays (5 vs. 6 days, p < 0.001) than those operated via sternotomy, with no significant differences in other outcome variables. A total of 16 patients underwent robotically assisted MVr with successful repair in all cases. Conclusion: A focused approach towards minimally invasive MVr has transformed the overall MVr strategy (incision; repair techniques) at our institution, leading to a growth in MVr volume and improved repair rates without significant complications. On this foundation, robotic MVr was first introduced at our institution in 2021 with excellent outcomes. This emphasizes the importance of building a competent team to perform these challenging operations, especially during the initial learning curve.

Utilization of Engineering Advances for Detailed Biomechanical Characterization of the Mitral-Ventricular Relationship to Optimize Repair Strategies: A Comprehensive Review.

The geometrical details and biomechanical relationships of the mitral valve-left ventricular apparatus are very complex and have posed as an area of research interest for decades. These characteristics play a major role in identifying and perfecting the optimal approaches to treat diseases of this system when the restoration of biomechanical and mechano-biological conditions becomes the main target. Over the years, engineering approaches have helped to revolutionize the field in this regard. Furthermore, advanced modelling modalities have contributed greatly to the development of novel devices and less invasive strategies. This article provides an overview and narrative of the evolution of mitral valve therapy with special focus on two diseases frequently encountered by cardiac surgeons and interventional cardiologists: ischemic and degenerative mitral regurgitation.

Left atrial function and not volume predicts mid-to-late atrial fibrillation after mitral valve repair.

OBJECTIVES: Patients undergoing surgical mitral valve repair (MVr) for degenerative mitral regurgitation are at risk of even late postoperative atrial fibrillation (AF). Left atrial (LA) function has been shown superior to LA volume in evaluating the risk of AF in diverse cardiac conditions. We therefore investigated the prognostic value of LA function and volume in predicting mid-to-late postoperative AF after MVr (>30 days postoperatively). METHODS: We retrospectively identified all patients who underwent MVr for degenerative mitral regurgitation between 2012 and 2019 at our institution. Exclusion criteria were preoperative AF, concomitant procedures, re-operations, missing or insufficiently processable preoperative echocardiograms and missing follow-up. LA function and volume measurements were conducted using speckle-tracking strain echocardiographic analysis. Postoperative LA function was measured in a subgroup with sufficient postoperative echocardiograms. RESULTS: We included 251 patients, of whom 39 (15.5%) experienced AF in the mid-to-late postoperative period. Reduced LA strain parameters and more than mild preoperative tricuspid regurgitation were independently associated with mid-to-late postoperative AF. LA volume index had no association with mid-to-late postoperative AF in univariable analysis and did not improve the performance of multivariable models. Patients with mid-to-late AF exhibited diminished improvement in LA function after surgery. CONCLUSIONS: In MVr patients, LA function (but not volume) showed independent predictive value for mid-to-late postoperative AF. Including LA function into surgical decision-making and approach may identify patients who will benefit from earlier intervention with the aim to prevent irreversible LA damage with consequent risk of postoperative AF.

Histopathological insights into mitral valve prolapse-induced fibrosis.

Mitral valve prolapse (MVP) is a cardiac valve disease that not only affects the mitral valve (MV), provoking mitral regurgitation, but also leads to maladaptive structural changes in the heart. Such structural changes include the formation of left ventricular (LV) regionalized fibrosis, especially affecting the papillary muscles and inferobasal LV wall. The occurrence of regional fibrosis in MVP patients is hypothesized to be a consequence of increased mechanical stress on the papillary muscles and surrounding myocardium during systole and altered mitral annular motion. These mechanisms appear to induce fibrosis in valve-linked regions, independent of volume-overload remodeling effects of mitral regurgitation. In clinical practice, quantification of myocardial fibrosis is performed with cardiovascular magnetic resonance (CMR) imaging, even though CMR has sensitivity limitations in detecting myocardial fibrosis, especially in detecting interstitial fibrosis. Regional LV fibrosis is clinically relevant because even in the absence of mitral regurgitation, it has been associated with ventricular arrhythmias and sudden cardiac death in MVP patients. Myocardial fibrosis may also be associated with LV dysfunction following MV surgery. The current article provides an overview of current histopathological studies investigating LV fibrosis and remodeling in MVP patients. In addition, we elucidate the ability of histopathological studies to quantify fibrotic remodeling in MVP and gain deeper understanding of the pathophysiological processes. Furthermore, molecular changes such as alterations in collagen expression in MVP patients are reviewed.

Recruited macrophages elicit atrial fibrillation.

Atrial fibrillation disrupts contraction of the atria, leading to stroke and heart failure. We deciphered how immune and stromal cells contribute to atrial fibrillation. Single-cell transcriptomes from human atria documented inflammatory monocyte and SPP1+ macrophage expansion in atrial fibrillation. Combining hypertension, obesity, and mitral valve regurgitation (HOMER) in mice elicited enlarged, fibrosed, and fibrillation-prone atria. Single-cell transcriptomes from HOMER mouse atria recapitulated cell composition and transcriptome changes observed in patients. Inhibiting monocyte migration reduced arrhythmia in Ccr2-∕- HOMER mice. Cell-cell interaction analysis identified SPP1 as a pleiotropic signal that promotes atrial fibrillation through cross-talk with local immune and stromal cells. Deleting Spp1 reduced atrial fibrillation in HOMER mice. These results identify SPP1+ macrophages as targets for immunotherapy in atrial fibrillation.

Abnormal Mechanics Relate to Myocardial Fibrosis and Ventricular Arrhythmias in Patients With Mitral Valve Prolapse.

BACKGROUND: The relation between ventricular arrhythmia and fibrosis in mitral valve prolapse (MVP) is reported, but underlying valve-induced mechanisms remain unknown. We evaluated the association between abnormal MVP-related mechanics and myocardial fibrosis, and their association with arrhythmia. METHODS: We studied 113 patients with MVP with both echocardiogram and gadolinium cardiac magnetic resonance imaging for myocardial fibrosis. Two-dimensional and speckle-tracking echocardiography evaluated mitral regurgitation, superior leaflet and papillary muscle displacement with associated exaggerated basal myocardial systolic curling, and myocardial longitudinal strain. Follow-up assessed arrhythmic events (nonsustained or sustained ventricular tachycardia or ventricular fibrillation). RESULTS: Myocardial fibrosis was observed in 43 patients with MVP, predominantly in the basal-midventricular inferior-lateral wall and papillary muscles. Patients with MVP with fibrosis had greater mitral regurgitation, prolapse, and superior papillary muscle displacement with basal curling and more impaired inferior-posterior basal strain than those without fibrosis (P<0.001). An abnormal strain pattern with distinct peaks pre-end-systole and post-end-systole in inferior-lateral wall was frequent in patients with fibrosis (81 versus 26%, P<0.001) but absent in patients without MVP with basal inferior-lateral wall fibrosis (n=20). During median follow-up of 1008 days, 36 of 87 patients with MVP with >6-month follow-up developed ventricular arrhythmias associated (univariable) with fibrosis, greater prolapse, mitral annular disjunction, and double-peak strain. In multivariable analysis, double-peak strain showed incremental risk of arrhythmia over fibrosis. CONCLUSIONS: Basal inferior-posterior myocardial fibrosis in MVP is associated with abnormal MVP-related myocardial mechanics, which are potentially associated with ventricular arrhythmia. These associations suggest pathophysiological links between MVP-related mechanical abnormalities and myocardial fibrosis, which also may relate to ventricular arrhythmia and offer potential imaging markers of increased arrhythmic risk.

Native and Post-Repair Residual Mitral Valve Prolapse Increases Forces Exerted on the Papillary Muscles: A Possible Mechanism for Localized Fibrosis?

BACKGROUND: Recent studies have linked mitral valve prolapse to localized myocardial fibrosis, ventricular arrhythmia, and even sudden cardiac death independent of mitral regurgitation or hemodynamic dysfunction. The primary mechanistic theory is rooted in increased papillary muscle traction and forces due to prolapse, yet no biomechanical evidence exists showing increased forces. Our objective was to evaluate the biomechanical relationship between prolapse and papillary muscle forces, leveraging advances in ex vivo modeling and technologies. We hypothesized that mitral valve prolapse with limited hemodynamic dysfunction leads to significantly higher papillary muscle forces, which could be a possible trigger for cellular and electrophysiological changes in the papillary muscles and adjacent myocardium. METHODS: We developed an ex vivo papillary muscle force transduction and novel neochord length adjustment system capable of modeling targeted prolapse. Using 3 unique ovine models of mitral valve prolapse (bileaflet or posterior leaflet prolapse), we directly measured hemodynamics and forces, comparing physiologic and prolapsing valves. RESULTS: We found that bileaflet prolapse significantly increases papillary muscle forces by 5% to 15% compared with an optimally coapting valve, which are correlated with statistically significant decreases in coaptation length. Moreover, we observed significant changes in the force profiles for prolapsing valves when compared with normal controls. CONCLUSIONS: We discovered that bileaflet prolapse with the absence of hemodynamic dysfunction results in significantly elevated forces and altered dynamics on the papillary muscles. Our work suggests that the sole reduction of mitral regurgitation without addressing reduced coaptation lengths and thus increased leaflet surface area exposed to ventricular pressure gradients (ie, billowing leaflets) is insufficient for an optimal repair.