Buu-Khanh Lam

Point: Minimally invasive bipolar radiofrequency ablation of lone atrial fibrillation: Early multicenter results

OBJECTIVE The treatment of lone atrial fibrillation can be a minimally invasive procedure using bipolar radiofrequency ablation technologies. Our objectives were to report on the safety and early efficacy of this novel therapeutic modality. METHODS At 3 North American institutions between February 2005 and August 2007, 100 patients underwent minimally invasive bilateral pulmonary vein isolation, autonomic denervation, and left atrial appendage resection. The mean age was 65 +/- 11 years, and 70% were male. The median duration of atrial fibrillation was 5.0 years; atrial fibrillation was paroxysmal in 39 patients (39%), persistent in 29 patients (29%), and permanent in 32 patients (32%). Indications for surgery included failure of medical therapy or percutaneous ablation and severe symptoms. Mean follow-up was 13.6 +/- 8.2 months. RESULTS The mean operative time was 253 +/- 65 minutes, and the median hospital length of stay was 5 days. There were no intraoperative conversions and no mortality to report. Postoperative complications included pacemaker requirement in 5 patients (5%), phrenic nerve palsy in 3 patients (3%), hemothorax in 3 patients (3%), transient ischemic attack in 1 patient (1%), and pulmonary embolism in 1 patient (1%). At follow-up, 87% of patients were in normal sinus rhythm (paroxysmal 93%, persistent 96%, permanent 71%; P < .05); antiarrhythmic therapy was discontinued in 62% of patients, and anticoagulation therapy was discontinued in 65% of patients. CONCLUSION Minimally invasive bipolar radiofrequency ablation of lone atrial fibrillation is a safe and efficacious therapeutic option in selected patients. Further development is needed to reduce the rate of complications. Long-term prospective results are required to further validate this modality as a therapeutic option to treat lone atrial fibrillation.

A randomized evaluation of simulation training on performance of vascular anastomosis on a high-fidelity in vivo model: The role of deliberate practice

OBJECTIVES There is mounting evidence supporting the benefit of surgical skills practice in a simulated environment. However, the use of simulation in cardiac surgical training has been limited. The purpose of the current trial was to examine the effect of independent and deliberate simulator practice, during nonclinical time, on the performance of an end-to-side microvascular anastomosis in an in vivo model. METHODS This single-blinded, randomized controlled trial received institutional review board approval. Thirty-nine first- and second-year surgical trainees were randomized to an expert-guided tutorial on a procedural trainer or to the expert-guided tutorial combined with self-directed practice on the same procedural trainer. Self-directed practice consisted of 10 anastomoses performed on the procedural trainer: a low-fidelity, commercially available bench model using 4-mm polytetrafluoroethylene graft as simulated blood vessel. Two weeks after the tutorial, subjects performed an end-to-side anastomosis in a live porcine model, under realistic operating room conditions. Assessment of outcomes was performed by 2 blinded, expert observers, uings validated measurements of technical skill. The primary outcome was the score on the Objective Structured Assessment of Technical Skill (OSATS) scale. Secondary outcomes included an anastomosis-specific end-product evaluation and time to completion. Statistical analysis was conducted using nonparametric, univariate techniques. RESULTS Compared with residents who received expert-guided simulator training alone, those who in addition practiced on a simulator independently after hours scored significantly higher on the OSATS scale (23.7 ± 4.7 vs 18.5 ± 3.9, P = .003). Residents who practiced independently also scored significantly higher on the end-product evaluation (11.4 ± 3.2 vs 8.9 ± 2.1, P = .02) and performed the anastomosis significantly faster (777 seconds vs 977 seconds, P = .04). Interrater reliability was high between the expert observers (intraclass correlation coefficient = 0.8). CONCLUSIONS Residents who had the opportunity for self-directed simulator practice performed an end-to-side anastomosis more adeptly, more quickly, and with a higher quality end product. The results of this randomized trial suggest that independent training on a procedural trainer did transfer to improved performance in an operating room environment. Simulator training should be incorporated into cardiovascular surgical curricula and residents should have access to this modality for independent after-hours practice to improve operating room performance.

Atrioesophageal Fistula in the Era of Atrial Fibrillation Ablation: A Review

The purpose of this review is to understand the epidemiology, clinical features, etiopathogenesis, and management of atrioesophageal fistula (AEF) after atrial fibrillation (AF) ablation. The incidence of AEF after AF ablation is 0.015%-0.04%. The principal clinical features include fever, dysphagia, upper gastrointestinal bleeding, sepsis, and embolic strokes. The close proximity of the esophagus to the posterior left atrial wall is responsible for esophageal injury during ablation. Prophylactic proton pump inhibitors, esophageal temperature monitoring, visualization of the esophagus during catheter ablation, esophageal protection devices, and avoidance of energy delivery in close proximity to the esophagus play an important role in preventing esophageal injury. Early surgical repair or esophageal stenting are the mainstay of treatment. Eliminating esophageal injury during AF ablation is of utmost importance in preventing AEF. A high index of suspicion and early intervention is necessary to prevent fatal outcomes.

Current Use of Prophylactic Strategies for Postoperative Atrial Fibrillation: A Survey of Canadian Cardiac Surgeons

BACKGROUND Evidence from multiple trials demonstrates the efficacy of prophylactic beta-blocker, amiodarone, and corticosteroid administration in reducing the incidence of postoperative atrial fibrillation. Despite this information, these interventions remain infrequently or inappropriately utilized. This study was designed to assess the frequency with which these prophylactic strategies are currently being used and to identify concerns and barriers to more widespread application. METHODS A link to an online survey was e-mailed to all practicing cardiac surgeons in Canada. Each surgeon was given a unique log-in identification number to complete the survey online through a secure web page. RESULTS Surveys were sent to 166 surgeons; 119 completed surveys (72%) were returned. Only 58% of respondents routinely use beta-blockade for prophylaxis. For nonusers, 44% are unconvinced of the evidence for this practice. The routine use of amiodarone among surgeons was 19%. Of the remainder, 43% cited a perceived increased risk of complications as the reason for not using this therapy. An additional 29% considered the therapy was excessively complicated or time consuming. Corticosteroids were routinely used by only one surgeon. Major barriers to use of steroids were unconvincing evidence (76%), a perceived increased risk of wound infection (38%), and hyperglycemia (30%). CONCLUSIONS Despite level 1 evidence, the use of beta-blockers, amiodarone, and corticosteroids for prophylaxis of atrial fibrillation among Canadian surgeons remains less than expected. The results of this survey support the need for further clinical trials with robust and clinically relevant outcomes that may further influence surgeons to adopt this practice.

The impact of prosthesis–patient mismatch after aortic valve replacement varies according to age at operation

Objectives Age may modify the impact of prosthesis–patient mismatch (PPM) on outcomes after aortic valve replacement (AVR), as physical functioning decreases with age, and comorbidities become more prevalent. We hypothesised that the consequences of PPM in patients 70 years old or older may be less important than in younger patients. Methods In total, 707 aortic stenosis patients were followed for a maximum of 17.5 years after AVR. PPM was defined as an in vivo indexed effective orifice area ≤0.85 cm2/m2, and severe PPM as ≤0.65 cm2/m2. Results In patients less than 70 years of age with normal LV function, the presence of PPM did not significantly alter survival. However, in patients under 70 with LV dysfunction, PPM was associated with decreased survival (HR 2.2; p=0.046). In patients aged 70 years of age or older, PPM had no effect on survival, regardless of LV function. Similarly, PPM was predictive of postoperative congestive heart failure (CHF) in patients under 70 with LV dysfunction (HR 3.6; p=0.046) but not in older patients. Similar results were observed for the composite endpoint of death or CHF. Postoperative LV mass regression was impaired by increased age (p=0.019), and by PPM in patients aged 70 years of age or older with LV dysfunction (by 28.8 g/m2; p=0.026). Conclusions The impact of PPM on outcomes after AVR depends on age at operation. PPM in patients under age 70 years with LV dysfunction is associated with decreased survival and lower freedom from CHF. In patients 70 years of age or older, PPM does not impact mortality or symptoms, but impairs LV mass regression beyond that explained by age alone.

Paracrine Engineering of Human Explant‐Derived Cardiac Stem Cells to Over‐Express Stromal‐Cell Derived Factor 1α Enhances Myocardial Repair

First generation cardiac stem cell products provide indirect cardiac repair but variably produce key cardioprotective cytokines, such as stromal‐cell derived factor 1α, which opens the prospect of maximizing up‐front paracrine‐mediated repair. The mesenchymal subpopulation within explant derived human cardiac stem cells underwent lentiviral mediated gene transfer of stromal‐cell derived factor 1α. Unlike previous unsuccessful attempts to increase efficacy by boosting the paracrine signature of cardiac stem cells, cytokine profiling revealed that stromal‐cell derived factor 1α over‐expression prevented lv‐mediated “loss of cytokines” through autocrine stimulation of CXCR4+ cardiac stem cells. Stromal‐cell derived factor 1α enhanced angiogenesis and stem cell recruitment while priming cardiac stem cells to readily adopt a cardiac identity. As compared to injection with unmodified cardiac stem cells, transplant of stromal‐cell derived factor 1α enhanced cells into immunodeficient mice improved myocardial function and angiogenesis while reducing scarring. Increases in myocardial stromal‐cell derived factor 1α content paralleled reductions in myocyte apoptosis but did not influence long‐term engraftment or the fate of transplanted cells. Transplantation of stromal‐cell derived factor 1α transduced cardiac stem cells increased the generation of new myocytes, recruitment of bone marrow cells, new myocyte/vessel formation and the salvage of reversibly damaged myocardium to enhance cardiac repair after experimental infarction. Stem Cells 2016;34:1826–1835

Atrial fibrillation therapies: lest we forget surgery.

Atrial fibrillation (AF) is a disease that causes a significant burden in a patients life. It is a known risk factor for heart failure, stroke, and premature death. The classic therapeutic strategies include rate control, rhythm control, and prevention of stroke. Pharmacological rhythm control with antiarrhythmic drugs can only be achieved 50% of the time while simultaneously subjecting patients to deleterious adverse reactions. With recent advances in catheter ablation procedures, rhythm control can be safely attained anywhere from 57%-80% of the time, depending on the number of repeat catheter ablation procedures that are performed and concomitant use of antiarrhythmic drugs. The Cox-Maze procedure is a technically challenging cut-and-sew atrial lesion set with associated morbidity, yet is still considered the gold standard for rhythm control. Fortunately, this procedure has been modified in efforts to improve the safety profile (shorter cross clamp and cardiopulmonary bypass time), to simplify lesion set creation with newer energy sources, and to perform this operation in a minimally invasive setting. Minimally invasive surgical AF ablation techniques have excellent safety profiles and can achieve rhythm control in up to 90% of patients. In contrast, patients undergoing open heart surgery can undergo either concomitant endocardial or epicardial AF ablation procedures without jeopardizing the surgery along with success rates from 60% to 88%. Thus, there has been an increase in current surgical options for treating AF because of novel approaches and energy sources which yield effective long-term results in patient care and minimize perioperative complications and thereby optimize the risk/benefit ratio profile.

Prosthesis-patient mismatch is less frequent and more clinically indolent in patients operated for aortic insufficiency.

OBJECTIVE To date, no study has focused on the incidence and effects of prosthesis-patient mismatch in patients requiring aortic valve replacement for aortic insufficiency. We hypothesized that the incidence and implications of prosthesis-patient mismatch in patients with aortic insufficiency might be different than for aortic stenosis or mixed disease because the annulus is generally larger in aortic insufficiency and left ventricular remodeling might differ. METHODS Ninety-eight patients with lone aortic insufficiency (>or=3+ with a preoperative mean gradient <30 mm Hg) were followed over 7.7 +/- 4.3 years (maximum, 17.5 years) with clinical and echocardiographic assessments. They were compared with 707 patients who had aortic valve replacement for aortic stenosis or mixed disease. Prosthesis-patient mismatch was defined as an in vivo indexed effective orifice area of 0.85 cm(2)/m(2) or less. RESULTS Compared with patients with aortic stenosis/mixed disease, patients with aortic insufficiency had approximately half the incidence of prosthesis-patient mismatch (P = .003). Patients with prosthesis-patient mismatch had significantly higher transprosthesis gradients postoperatively. An independent detrimental effect of prosthesis-patient mismatch on survival was observed in patients with aortic stenosis/mixed disease who had preoperative left ventricular dysfunction (hazard ratio, 2.3; P = .03) but not in patients with aortic insufficiency, irrespective of left ventricular function (hazard ratio, 0.7; P = .7). In patients with aortic stenosis/mixed disease with left ventricular dysfunction, prosthesis-patient mismatch predicted heart failure symptoms by 3 years after aortic valve replacement (odds ratio, 6.0; P = .002), but there was no such effect in patients with aortic insufficiency (P = .8). Indexed left ventricular mass regression occurred to a greater extent in patients with aortic insufficiency than in patients with aortic stenosis/mixed disease (by an additional 29 +/- 5 g/m(2), P < .001), and there was a trend for prosthesis-patient mismatch to impair regression in patients with aortic insufficiency (by 30 +/- 17 g/m(2), P = .1). CONCLUSIONS The incidence and significance of prosthesis-patient mismatch differs in patients with aortic insufficiency compared with those with aortic stenosis or mixed disease. In patients with aortic insufficiency, prosthesis-patient mismatch is seen less frequently and has no significant effect on survival and freedom from heart failure but might have a negative effect on left ventricular mass regression.

Aortic root geometry in bicuspid aortic insufficiency versus stenosis: implications for valve repair

OBJECTIVES The contribution of aortic annular and root disease in bicuspid aortic valve (BAV) insufficiency remains unclear. We compared aortic root geometry between BAV stenosis and aortic insufficiency (AI), before and after repair. METHODS Patients presenting for surgery for BAV insufficiency (n = 58) were compared with patients with BAV stenosis (n = 58). Clinical and transoesophageal echocardiographic data were collected, including end-diastolic diameters of the ventriculo-aortic junction (VAJ), aortic root, sinotubular junction (STJ) and ascending aorta (AA). RESULTS AI patients were younger and more likely to be male compared with aortic stenosis (AS) patients. VAJ, aortic root and STJ diameters were significantly larger in AI compared with AS patients (30 ± 0.5 vs 25 ± 0.4 mm, P < 0.001; 41 ± 0.8 vs 34 ± 0.6 mm, P < 0.001; 36 ± 0.9 vs 30 ± 0.6 mm, P < 0.001, respectively). Following multivariable adjustment for age, sex, body surface area and ascending aortic diameter, these diameters remained larger in AI patients with a mean difference of 3, 6 and 4 mm, respectively (all P < 0.001). Mean AA diameter in the AI group was similar to the AS group (37 ± 1.0 vs 34 ± 0.8 mm, P = 0.06). Forty (69%) AI patients had BAV repair with a mean reduction in VAJ and STJ diameters of 5 and 9 mm compared with prerepair (P < 0.0001). CONCLUSIONS Despite the absence of aortic aneurysms, aortic annulus and root dimensions are significantly larger in patients with BAV insufficiency compared with stenosis. Alterations in aortic root geometry contribute to the pathophysiology of BAV insufficiency and require correction for a successful repair.

Impact of visualization on simulation training for vascular anastomosis

Objective: There is mounting evidence supporting the benefit of surgical simulation on the learning of skills independently and in a patient‐safe environment. The objective of this study was to examine the effect of visualization of surgical steps via instructional media on performance of an end‐to‐side microvascular anastomosis. Methods: Thirty‐two first‐ and second‐year surgical trainees from the University of Ottawa received an expert‐guided, didactic lecture on vascular anastomosis and performed an end‐to‐side anastomosis on a procedural model to assess baseline skills. Assessments were performed by 2 blinded, expert observers using validated measurements of skill. Subjects were then proctored to perform anastomoses using the model. Subjects were then randomized to watch an instructional video on performance of vascular anastomosis using visualization as the education strategy. One week later, subjects were again assessed for technical skill on the model. The primary outcome was the score achieved on the Objective Structured Assessment of Technical Skill (OSATS) scale. Secondary outcomes included an anastomosis‐specific End‐Product Rating Score and time to completion. Results: Compared with residents who received expert‐guided simulator training alone, those who used the supplementary multimedia scored significantly greater on OSATS (17.4 ± 2.9 vs 14.2 ± 3.2, P = .0013) and on End‐Product Rating Score (11.24 ± 3.0 vs 7.4 ± 4.1, P = .011). However, performance time did not differ between groups (15.7 vs 14.3 minutes, P = .79). Conclusions: Residents with supplemental instructional media performed an end‐to‐side anastomosis more proficiently as assessed by OSATS and with a greater quality end‐product. This suggests that both didactic simulation training as well as use of visualization multimedia improves learning and performance of vascular anastomosis and should be incorporated into surgical curricula.