Propofol cardioprotection for on-pump aortocoronary bypass surgery in patients with type 2 diabetes mellitus (PRO-TECT II): a phase 2 randomized-controlled trial.

PURPOSE: The efficacy of myocardial conditioning strategies is compromised in patients with advanced age, diabetes, or low ejection fraction. We conducted a single-centre parallel-arm blinded randomized-controlled trial to determine whether propofol provides perioperative myocardial protection. METHODS: Patients enrolled in this study were scheduled for primary aortocoronary bypass surgery utilizing normothermic cardiopulmonary bypass (CPB) with blood cardioplegia. The participants were stratified by diabetic status and left ventricular ejection fraction and randomly assigned to receive either an elevated dose of propofol -previously associated with experimental cardioprotection- or an isoflurane preconditioning regime. The primary endpoint was the coronary sinus (CS) concentration of 15-F2t-isoprostane (isoP). Secondary endpoints included in-hospital low cardiac output syndrome (LCOS) and major adverse cardiac events, 12- and 24-hr CS cardiac troponin I (cTnI) release, and myocardial B-cell lymphoma 2 (Bcl-2) protein expression. RESULTS: Data were analyzed from 125 of 137 randomized participants. Participants receiving propofol experienced a greater mean (SD) increase from baseline in CS 15-F2t-isoP levels compared with those receiving isoflurane [26.9 (10.9) pg·mL(-1) vs 12.1 (10.4) pg·mL(-1), respectively; mean difference, 14.8; 95% confidence interval (CI), 11.0 to 18.6; P < 0.001] but a decreased incidence of LCOS (20.9% vs 57.1%, respectively; relative risk [RR],0.37; 95% CI, 0.22 to 0.62; P < 0.001). The incidence of LCOS was similar between groups in participants without type 2 diabetes mellitus (DM2) (P = 0.382) but significantly decreased in the propofol DM2 subgroup compared with the isoflurane DM2 subgroup (17.9% vs 70.3%, respectively; RR, 0.26; 95% CI, 0.13 to 0.52; P < 0.001). Propofol was associated with an increase in myocardial Bcl-2 protein expression (P = 0.005), a lower incidence of a CS cTnI threshold for myocardial infarction (P = 0.014), and fewer heart failure events (P < 0.001). CONCLUSION: Propofol may be a preemptive intraoperative cardioprotectant for patients with DM2 under conditions of normothermic CPB and blood cardioplegic arrest. The study is registered at www.clinicaltrials.gov (NCT00734383) and www.controlled-trials.com (ISRCTN70879185).

Regional Anesthesia With Paravertebral Blockade Is Associated With Improved Outcomes in Patients Undergoing Minithoracotomy Cardiac Surgery.

OBJECTIVE: Severe postoperative pain has been shown to affect many patients following minimally invasive cardiac surgeries (MICS). Multimodal pain management with regional anesthesia, particularly by delivery of local anesthetics using a paravertebral catheter (PVC), has been shown to reduce pain in operations involving thoracotomy incisions. However, few studies have reported high-quality safety and efficacy outcomes of PVCs following MICS. METHODS: Patients who underwent MICS at Vancouver General Hospital between 2016 and 2019 (N = 123) were reviewed for perioperative opioid-narcotic use. Primary outcomes were postoperative opioid use and hospital length of stay (LOS). Statistical analyses were performed using univariate and multivariable regression models to determine independent risk factors. RESULTS: A total of 54 patients received routine systemic analgesia (control), 53 patients received a paravertebral catheter (PVC), and 16 patients received another mode of regional analgesia (non-PVC). The mean hospital LOS was significantly different in patients in the PVC group at 5.8 ± 2.0 days versus 8.3 ± 7.1 days in the control and 6.6 ± 2.3 days in the non-PVC group (P = 0.033). The percentage of patients who did not require postoperative oxycodone was significantly higher in the PVC group (48.1%), compared with the control (24.5%) and non-PVC (37.5%; P = 0.043) groups. CONCLUSIONS: The administration of regional anesthesia using PVCs was associated with reduced need for opioids and a shorter LOS. The reduction in postoperative opioids may reduce the risk of potential opioid dependency in this population. Future studies should involve randomized controlled trials with systematic evaluation of pain scores to verify current study results.

Histoplasma capsulatum culture-negative prosthetic valve endocarditis presenting as a cystic mass.

A 58-year-old immunocompetent patient with previous prosthetic valve presented with chest pain, constitutional symptoms and septic shock. Blood cultures and transthoracic echocardiogram were negative, but the patient was initiated on broad spectrum antibiotics due to high clinical suspicions of infective endocarditis. The patient received a transoesophageal echocardiogram revealing a cystic bioprosthetic valve lesion. Culture-negative endocarditis workup identified active disseminated histoplasmosis with likely Histoplasma endocarditis. A multidisciplinary discussion was held, and the patient was deemed high-risk for a third re-do open heart surgery. He was treated medically with anti-fungal treatment with good clinical recovery.

Differences in myocardial PTEN expression and Akt signalling in type 2 diabetic and nondiabetic patients undergoing coronary bypass surgery.

OBJECTIVE: Patients with diabetes experience increased cardiovascular complications after cardiac surgery. Hyperglycaemia predicts increased mortality after myocardial infarction and may influence cardiovascular risk in humans. Impaired prosurvival phosphatase and tensin homologue on chromosome 10 (PTEN)-Akt signalling could be an important feature of the diabetic heart rendering it resistant to preconditioning. This study was designed to evaluate for differences and relationships of myocardial PTEN-Akt-related signalling and baseline glycaemic control marker in type 2 diabetic and nondiabetic patients undergoing coronary artery bypass surgery. METHODS: Right atrial biopsies and coronary sinus blood were obtained from 18 type 2 diabetic and 18 nondiabetic patients intraoperatively. Expression and phosphorylation of Akt, endothelial nitric oxide synthase (eNOS), Bcl-2 and PTEN were evaluated by Western blot. Plasma 15-F(2t) -isoprostane concentrations were evaluated by liquid chromatography-mass spectrometry. RESULTS: PTEN expression and 15-F(2t) -isoprostane concentrations were significantly higher in diabetic patients. Increased fasting blood glucose levels correlated with increased coronary sinus plasma 15-F(2t) -isoprostane concentrations. Increased cardiac 15-F(2t) -isoprostane generation was highly correlated with myocardial PTEN expression. Bcl-2 expression and eNOS phosphorylation were significantly lower in diabetic compared with nondiabetic patients. Akt phosphorylation tended to be lower in diabetic patients; however, this tendency failed to reach statistical significance. CONCLUSION: The current results suggest that prosurvival PTEN-Akt signalling is impaired in the diseased diabetic myocardium. Hyperglycaemia and increased oxidative stress may contribute to this phenomenon. These findings strengthen the understanding of the underlying biologic mechanisms of cardiac injury in diabetic patients, which could facilitate development of new treatments to prevent cardiovascular complications in this high-risk population.

Prophylactic intravenous magnesium sulphate in addition to oral {beta}-blockade does not prevent atrial arrhythmias after coronary artery or valvular heart surgery: a randomized, controlled trial.

BACKGROUND: Atrial arrhythmias (AA) are an important cause of morbidity after cardiac surgery. Efforts at prevention of postoperative AA have been suboptimal. Perioperative beta-blocker administration is the standard of care at many centers. Although prophylactic administration of magnesium sulfate (MgSO(4)) has been recommended, review of all previously published trials of MgSO(4) reveals conflicting results. This study was designed to address methodological shortcomings from previous studies and is the largest randomized, placebo-controlled trial of intravenous (IV) MgSO(4) for the prevention of AA after coronary artery bypass grafting or cardiac valvular surgery. METHODS AND RESULTS: A total of 927 nonemergent cardiac surgery patients were stratified into 2 groups: isolated coronary artery bypass grafting (n=694), or valve surgery with or without coronary artery bypass grafting (n=233), and randomized to receive either 5g IV MgSO(4) or placebo on removal of the cross-clamp, followed by daily 4-hour infusions, from postoperative day 1 until postoperative day 4. All patients were treated according to an established oral beta-blocker protocol. Postoperative serum Mg levels were checked and standard of care was to administer IV MgSO(4) for low serum levels. The primary end point was AA lasting > or =30 minutes or requiring treatment for hemodynamic compromise. There were no differences in the incidence of AA between patients who received IV MgSO(4) or placebo (26.4% versus 24.3%, respectively). The results were similar when broken down according to stratified groups. CONCLUSIONS: In patients treated with a protocol for postoperative oral beta-blocker after nonemergent cardiac surgery, the addition of prophylactic IV MgSO(4) did not reduce the incidence of AA.

Functional analysis of the chromosome 9p21.3 coronary artery disease risk locus.

OBJECTIVE: We have investigated the functional significance of conserved sequences within the 9p21.3 risk locus for coronary artery disease (CAD) and determined the relationship of 9p21.3 to expression of ANRIL and to whole genome gene expression. METHODS AND RESULTS: We demonstrate that a conserved sequence within the 9p21.3 locus has enhancer activity and that the risk variant significantly increases reporter gene expression in primary aortic smooth muscle cells. Whole blood RNA expression of the short variants of ANRIL was increased by 2.2-fold whereas expression of the long ANRIL variant was decreased by 1.2-fold in healthy subjects homozygous for the risk allele. Expression levels of the long and short ANRIL variants were positively correlated with that of the cyclin-dependent kinase inhibitor, CDKN2B (p15) and TDGF1 (Cripto), respectively. Relevant to atherosclerosis, genome-wide expression profiling demonstrated upregulation of gene sets modulating cellular proliferation in carriers of the risk allele. CONCLUSIONS: These findings are consistent with the hypothesis that the 9p21.3 risk allele contains a functional enhancer, the activity of which is altered in carriers of the risk allele. 9p21.3 may promote atherosclerosis by regulating expression of ANRIL, which in turn is associated with altered expression of genes controlling cellular proliferation pathways.

Novel Percutaneous Treatment of Cerebral Malperfusion Before Surgery for Acute Type A Dissection.

We present the first known application of preoperative percutaneous management of cerebral malperfusion in a patient with acute near-total occlusion of the right common carotid artery with left hemiplegia complicating an acute Stanford type A aortic dissection.

A Novel Approach Using Computed Tomography Angiograms to Predict Sternotomy or Complicated Anastomosis in Patients Undergoing Robotically Assisted Minimally Invasive Direct Coronary Artery Bypass.

OBJECTIVE: Robotically assisted minimally invasive direct coronary artery bypass is an alternative to sternotomy-based surgery in properly selected patients. Identifying the left anterior descending artery when it is deep in the epicardial fat can be particularly challenging through a 5- to 6-cm mini-thoracotomy incision. The objective of this study was to evaluate a technique for predicting conversion to sternotomy or complicated left anterior descending artery anastomosis using preoperative cardiac-gated computed tomography angiograms. METHODS: Retrospective review of 75 patients who underwent robotically assisted minimally invasive direct coronary artery bypass for whom a preoperative computed tomography angiogram was available. The distance from the left anterior descending artery to the myocardium was measured on a standardized "5-chamber" axial computed tomography view. The relative risk of sternotomy or complicated anastomosis was compared between patients whose left anterior descending artery was resting directly on the myocardium (left anterior descending artery to the myocardium distance = 0 mm) with those whose left anterior descending artery was resting above (left anterior descending artery to the myocardium distance > 0 mm). RESULTS: The average left anterior descending artery to the myocardium distance was 3.2 ± 2.6 mm (range = 0-11.5 mm). Fourteen patients (18.7%) had an left anterior descending artery to the myocardium distance of 0 mm. Of the entire group of 75 patients, 6 (8.0%) required conversion to sternotomy. Four others (5.3%) were reported to have a complication with the anastomosis intraoperatively. For patients with left anterior descending artery to the myocardium distance of 0 mm, the relative risk of sternotomy or complicated anastomosis was 18.0 (95% confidence interval = 4.3-75.6, P = 0.0001). CONCLUSIONS: In our experience, patients with left anterior descending artery to the myocardium distance of 0 mm were at significantly higher risk of either conversion to sternotomy or technically challenging anastomosis, with 8 (57.1%) of 14 patients in this group experiencing either end point. This novel measurement may be useful to identify patients who may have anatomy, which is not well suited to the robotically assisted minimally invasive direct coronary artery bypass approach.

Is the Future of Coronary Arterial Revascularization a Hybrid Approach?: The Canadian Experience Across Three Centers.

OBJECTIVE: Hybrid coronary revascularization offers and combines the advantages of both surgical and percutaneous revascularization and eliminates at the same time the disadvantages of both procedures. The objective of this study was to assess graft and stent patency at 6 months, rate of bleeding, intensive care unit and hospital stay, rate of reintervention, and long-term clinical follow-up. METHODS: From March 2004 to November 2015, a total of 203 patients underwent robotic-assisted minimally invasive direct coronary artery bypass graft of the left internal thoracic artery to the left anterior descending artery and PCI of a non-left anterior descending vessel in a single or two stage, at three different centers. Patients underwent 6-month angiographic follow-up. The mean ± SD clinical follow-up was 77.82 ± 41.4 months. RESULTS: Successful hybrid coronary revascularization occurred in 196 of the 203 patients. One hundred forty-six patients underwent simultaneous surgical and percutaneous intervention. Nineteen patients underwent PCI before surgery, and 38 patient underwent PCI after surgery. No in-hospital mortality occurred. The mean ± SD ICU stay was 1 ± 1 days and the mean ± SD hospital stay was 5 ± 2 days. Only 13.3% of the patients required a blood transfusion. Six-month angiographic follow-up has been performed in the 95 patients, and it demonstrated a left internal thoracic artery anastomotic patency of 97.9% and stent patency of 92.6%. A total of 77.8 ± 41.4-month clinical follow-up demonstrated 95.1% survival, 92.6% freedom from angina, and 90.7% freedom from any form of coronary revascularization. CONCLUSIONS: Hybrid coronary revascularization seems to be a promising and safe revascularization strategy. It provides selected patients with an alternative, functionally complete revascularization with minimal surgical trauma and good long-term clinical outcomes.

Echocardiographic measurements alone do not provide accurate non-invasive selection of annuloplasty band size for robotic mitral valve repair.

BACKGROUND AND AIM OF THE STUDY: Successful mitral valve repair (MVP) is dependent on accurate annuloplasty band sizing. This is difficult and time-consuming when performed via port-access, or through a 4-cm minithoracotomy used in robotically assisted MVP. With the goal of moving toward a less-invasive approach and minimizing cross-clamp time, an attempt was made to determine annuloplasty band size using transesophageal echocardiography (TEE) alone. METHODS: The intertrigonal distance (ITD) was determined by dividing the left ventricular outflow tract diameter (LVOT: measured on standard midesophageal aortic valve long-axis view) by 0.8. The ITD was compared to a nomogram developed to select the best Cosgrove-Edwards annuloplasty band size. RESULTS: Between July and October, 2004, 11 patients (mean age 52.6 +/- 17.9 years; four Barlow's valves with bileaflet prolapse, four posterior leaflet prolapses, one anterior leaflet prolapse, one rheumatic, one dilated annulus) undergoing robotically assisted MVP had the annuloplasty band chosen using TEE alone. Seven patients (63.6%) had no or mild mitral regurgitation (MR) on postoperative TEE. Three patients (27.2%) had some systolic anterior motion (SAM), with one (Barlow's valve) requiring a second repair (same operation). One patient (9.1%, rheumatic) had grade 2+ MR on postoperative TEE. CONCLUSION: In this small case series, a substantial proportion of patients had suboptimal immediate postoperative results. This suggests that selection of the annuloplasty band should not be based on a single echocardiographic variable as it depends on the etiology of the MR, and other dimensions of the mitral valve. Further studies are ongoing to develop a non-invasive method for the selection of annuloplasty band size.

Extracorporeal membrane oxygenation after protracted ventricular fibrillation cardiac arrest: case report and discussion.

Extracorporeal membrane oxygenation (ECMO) is a method to provide temporary cardiac and respiratory support to critically ill patients. In recent years, the role of ECMO in emergency departments (EDs) for select adults has increased. We present the dramatic case of a 29-year-old man who was placed on venoarterial ECMO for cardiogenic shock and respiratory failure following collapse and protracted ventricular fibrillation cardiac arrest in our ED. Resuscitation efforts prior to ECMO commencement included 49 minutes of virtually continuous cardiopulmonary resuscitation (CPR), 11 defibrillations, administration of numerous medications, including a thrombolytic agent, while CPR was ongoing, percutaneous coronary intervention and stenting for a mid-left anterior descending coronary artery dissection and thrombotic occlusion, inotropic support, and intra-aortic balloon pump counterpulsation. Over the next 48 hours following ECMO commencement, the patient's cardiorespiratory function rapidly improved, and he was discharged home 9 days after admission with no neurologic sequelae. The history, indications, and increasing role of ECMO in a range of conditions, including cardiac arrest, are reviewed.

Traction injury during minimally invasive harvesting of the saphenous vein is associated with impaired endothelial function.

OBJECTIVE: Many methods of minimally invasive surgical harvesting of the great saphenous vein have been developed because of the morbidity related to the long skin incision after traditional (open) great saphenous vein harvesting. One such method involves the use of multiple small incisions separated by 10- to 15-cm skin bridges through which the saphenous vein is harvested. We hypothesized that this method of saphenous vein harvesting might subject the saphenous vein to considerable traction forces, resulting in impaired endothelial cell function. METHODS: Four-millimeter great saphenous vein segments were obtained from patients undergoing elective coronary artery bypass graft surgery. Group A (minimally invasive surgery) consisted of 23 rings from 20 patients (age, 65.8 +/- 11.1 years, mean +/- SD). Group B (open harvesting) consisted of 33 rings from 8 patients (age, 69.8 +/- 8.6 years). All great saphenous vein segments were undistended and were used within 24 hours of harvesting. Isometric tension experiments were performed on each ring of the great saphenous vein by using a force-displacement transducer to measure the force of contraction in grams. Measurements included developed force after exposure to high-potassium depolarizing solution and 50 micromol/L phenylephrine and decrease in force of contraction (relaxation) after exposure to 1 and 10 micromol/L acetylcholine. RESULTS: There were no differences between the minimally invasive surgery and open harvesting groups in their responses to high-potassium depolarizing solution or phenylephrine: high-potassium depolarizing solution, contractions of 4.26 +/- 0.72 g (mean +/- SEM) and 3.95 +/- 0.38 g, respectively (P =.70); phenylephrine, contractions of 3.49 +/- 0.63 g and 2.73 +/- 0.39 g, respectively (P =.41). There was no net relaxation in segments from the minimally invasive surgery group after exposure to 1.0 or 10 micromol/L acetylcholine. In contrast, rings from the open harvesting group demonstrated relaxation of -0.41 +/- 0.07 g and -0.32 +/- 0.09 g after exposure to 1.0 and 10 micromol/L acetylcholine, respectively. CONCLUSIONS: In undistended saphenous vein segments isolated from patients undergoing minimally invasive surgical and open techniques of harvesting, there was no acetylcholine-mediated endothelium-dependent relaxation in the minimally invasive surgery group. Therefore harvesting of the great saphenous vein through multiple small incisions might result in endothelial dysfunction, possibly caused by traction injury.

Effect of moderate pressure distention on the human saphenous vein vasomotor function.

BACKGROUND: Manual pressure distension, which is commonly applied to the human saphenous vein graft for coronary artery bypass, is believed to have detrimental consequences for the graft patency. The vasomotor function of the vein after distention during surgical preparation for grafting and after distention in laboratory conditions at pressure of 50 to 600 mm Hg was studied. The effect of a combination of vasodilative agents to prevent vasospasm was also tested. METHODS: The contractile and dilatory responses of distended and undistended human saphenous veins and those after drug treatment were examined in organ baths under isometric conditions. RESULTS: Distention at the pressure range 100 to 300 mm Hg resulted in an increased contractile response of the saphenous vein to both alpha-adrenergic activation with 50 micromol/L phenylephrine (153.73% +/- 15.69%) and depolarization with 80 mmol/L K(+) (141.03% +/- 15.13%) in comparison with the undistended vein and did not impair the relaxation. In contrast manual distention during surgical preparation abolished the contractile response and impaired the relaxation. The application of a combination of vasodilative drugs (alpha-adrenergic antagonist phenoxybenzamine, 10 micromol/L, Rho-kinase inhibitor HA-1077, 50 micromol/L, and calcium blocker nicardipine, 1 micromol/L) eliminated the contractile response of the vein to phenylephrine and 80 mmol/L K(+). This effect was sustained more than 20 hours after the washout of the drugs. CONCLUSIONS: The distention of the human saphenous vein at moderate pressure combined with the application of the effective combination of vasodilative drugs before grafting into the arterial circulation could be a beneficial alternative to the current practice of uncontrolled pressure distension.

A debate on the value and necessity of clinical trials in surgery.

In the current era of evidence-based medicine there is increasing demand for randomized clinical trials (RCTs) in surgery. Unfortunately, many unique aspects of surgery make RCTs difficult to implement. This article is a debate that explores the motion that clinical trials in surgery are both useful and necessary.

Noninvasive investigations for the early detection of chronic airways dysfunction following lung transplantation.

BACKGROUND: The diagnosis of chronic rejection after lung transplantation is limited by the lack of a reliable test to detect airways disease early. OBJECTIVES: To determine whether maximum midexpiratory flow (MMEF), or changes on high resolution computed tomography (HRCT) or ventilation/perfusion lung (V/Q) scans are sensitive and specific for early detection of bronchiolitis obliterans syndrome (BOS; forced expiratory volume in 1 s [FEV1] less than 80% post-transplant baseline) by evaluating long term survivors of lung transplantation at two sequential time points. METHODS: Twenty-two stable lung transplant recipients underwent spirometry, HRCT scanning and V/Q scanning 1.6 +/- 0.9 years and 3.1 +/- 1.1 years post-transplant (time points 1 and 2, respectively; mean +/- SD). RESULTS: Although HRCT was sensitive for the detection of BOS, it lacked specificity, and hence, there were no significant relationships between the presence of BOS and any of the HRCT parameters evaluated at time 1 or time 2. Of the V/Q parameters studied, the presence of heterogeneous perfusion (P=0.04, sensitivity 100%, specificity 33%) and segmental perfusion defects (P=0.04, sensitivity 60%, specificity 83%) were significantly related to BOS, but only at time 2. MMEF less than or equal to 75% post-transplant baseline was significantly related to the presence BOS at time 1 only (P=0.05, sensitivity 100%, specificity 47%). MMEF less than or equal to 75% post-transplant baseline at time 1 was sensitive for the development of BOS at time 2, but was limited by low specificity. CONCLUSIONS: In this group of lung transplant recipients, HRCT and V/Q scanning, as well as analysis of MMEF, did not add information that was clinically more useful than FEV1 for the early identification of chronic rejection.

Prophylactic magnesium does not prevent atrial fibrillation after cardiac surgery: a meta-analysis.

BACKGROUND: Atrial fibrillation (AF) is a common complication after cardiac surgery. Previous meta-analyses have concluded prophylactic magnesium (Mg) prevents postoperative AF, although with a significant degree of heterogeneity among included studies. Recently, the largest randomized, controlled trial published to date (but not included in prior published meta-analyses) concluded that Mg sulfate is not protective against AF after cardiac surgery. The objective of this study was to conduct a new meta-analysis including the results of new Mg trials not included in previous meta-analyses, and to investigate the potential causes and effects of significant heterogeneity observed in previously published meta-analyses. METHODS: The MEDLINE, EMBASE, and CENTRAL databases were searched for relevant studies published up to March 31, 2012. Pooled odds ratios of occurrence of AF were calculated using random-effects models. Heterogeneity was assessed as significant using the I(2) statistic. RESULTS: Egger's and funnel plots demonstrated biases toward stronger and more positive effects of Mg in smaller studies. When the analysis was restricted to the five double-blind, intention-to-treat studies in which AF was the primary outcome (Mg arm, n = 710; control arm, n = 713), Mg did not prevent postoperative AF (odds ratio, 0.94; p = 0.77), and heterogeneity was no longer significant (I(2) = 40%; p = 0.15). CONCLUSIONS: This meta-analysis, restricted to well-conducted trials, does not support the prophylactic use of Mg to prevent AF after cardiac surgery. Prior meta-analyses have drawn conclusions from simple random-effects models with significant heterogeneity. However, this approach leaves important residual heterogeneity and overemphasizes the strongly positive effects of smaller studies.

A novel shape memory alloy annuloplasty ring for minimally invasive surgery: design, fabrication, and evaluation.

A novel annuloplasty ring with a shape memory alloy core has been developed to facilitate minimally invasive mitral valve repair. In its activated (austenitic) phase, this prototype ring has comparable mechanical properties to commercial semi-rigid rings. In its pre-activated (martensitic) phase, this ring is flexible enough to be introduced through an 8-mm trocar and easily manipulated with robotic instruments within the confines of a left atrial model. The core is constructed of 0.50 mm diameter NiTi, which is maintained below its martensitic transition temperature (24 °C) during deployment and suturing. After suturing, the ring is heated above its austenitic transition temperature (37 °C, normal human body temperature) enabling the NiTi core to attain its optimal geometry and stiffness characteristics indefinitely. This article summarizes the design, fabrication, and evaluation of this prototype ring. Experimental results suggest that the NiTi core ring could be a viable alternative to flexible bands in robot-assisted minimally invasive mitral valve repair.

A dynamic heart system to facilitate the development of mitral valve repair techniques.

OBJECTIVE: The development of a novel surgical tool or technique for mitral valve repair can be hampered by cost, complexity, and time associated with performing animal trials. A dynamically pressurized model was developed to control pressure and flowrate profiles in intact porcine hearts in order to quantify mitral regurgitation and evaluate the quality of mitral valve repair. METHODS: A pulse duplication system was designed to replicate physiological conditions in explanted hearts. To test the capabilities of this system in measuring varying degrees of mitral regurgitation, the output of eight porcine hearts was measured for two different pressure waveforms before and after induced mitral valve failure. Four hearts were further repaired and tested. Measurements were compared with echocardiographic images. RESULTS: For all trials, cardiac output decreased as left ventricular pressure was increased. After induction of mitral valve insufficiencies, cardiac output decreased, with a peak regurgitant fraction of 71.8%. Echocardiography clearly showed increases in regurgitant severity from post-valve failure and with increased pressure. CONCLUSIONS: The dynamic heart model consistently and reliably quantifies mitral regurgitation across a range of severities. Advantages include low experimental cost and time associated with each trial, while still allowing for surgical evaluations in an intact heart.