Selective autonomic stimulation of the AV node fat pad to control rapid post-operative atrial arrhythmias.

Junctional ectopic tachycardia (JET) and atrial fibrillation (AF) occur in patients recovering from open-heart surgery (OHS). Pharmacologic treatment is used for the control of post-operative atrial arrhythmias (POAA), but is associated with side effects. There is a need for a reversible, modulated solution to rate control. We propose a non-pharmacologic technique that can modulate AV nodal conduction in a selective fashion. Ten mongrel dogs underwent OHS. Stimulation of the anterior right (AR) and inferior right (IR) fat pad (FP) was done using a 7-pole electrode. The IR was more effective in slowing the ventricular rate (VR) to AF (52 +/- 20 vs. 15 +/- 10%, p = 0.003) and JET (12 +/- 7 vs. 0 +/- 0%, p = 0.02). Selective site stimulation within a FP region could augment the effect of stimulation during AF (57 +/- 20% (maximum effect) vs. 0 +/- 0% (minimum effect),

Rate Control of Atrial Arrhythmias Can Be Achieved by Selective Cardiac Neurostimulation

Introduction: Atrial arrhythmias (AA) occur in up to 40% of patients recovering from open-heart surgery (OHS). Pharmacologic treatment has been the main strategy used for the control of post-operative AA, but is associated with hypotension, pro-arrhythmia and myocardial dysfunction. There is a need for a reversible, modulated solution to rate control. We demonstrated the efficacy of vagal stimulation at inferior right fat pad (FP) to slow the ventricular response (VR) of atrial fibrillation (AF) and junctional ectopic tachycardia (JET). We hypothesized that the VR response to AA could be improved by alterations in 1) the site of stimulation (anterior right FP vs. inferior right FP), 2) site within the two FP regions tested, and 3) whether there was a relationship between stimulation voltage (V) and electrophysiologic effect. Methods: Eight mongrel dogs, age 8.7 ± 3.9 months and weighing 21.5 ± 2.5 kg, underwent open heart surgery replicating Tetralogy of Fallot repair. Stimulation of the anterior right (AR) and inferior right (IR) fat pad was used to control the VR of AF and JET. A 7-pole electrode was sutured to the AR and IR FP and used to deliver stimulation therapy. Tested parameters included: 1) FP site, 2) stimulation pole configuration, and 3) stimulation (1-25) V on the VR to AF and JET. Stimulation frequency was 30 Hz, and pulse width was 0.15 msec. Results: 1). The inferior right FP was more effective in slowing the VR response to AF (-0.43 ± 0.18 vs. -0.18 ± 0.11 %, p =0.03) and JET (-0.16 ± 0.06 vs. 0.0 ±0.0, p =0.06.) 2). Selective site stimulation within a FP region could augment the effect of stimulation during AF (-0.48 ± 0.21 (maximum effect) vs. 0.0 ± 0.0 % (least effect), p=0.01). Stimulation of electrodes 2+3 produced the greatest reduction in HR with a maximum percent VR reduction of 34.8% 3). FP stimulation at increasing V demonstrated a voltage-dependent effect (-0.12 ± 0.19 (low V) vs. -0.63 ± 0.21 (high V) %, p=0.01)

Effects of glutaraldehyde concentration, pretreatment time, and type of tissue (porcine versus bovine) on postimplantation calcification

ObjectiveOur objective was to evaluate the effects of glutaraldehyde (GA) concentration, time of pretreatment, and type of tissue (porcine vs bovine) on quantitative and qualitative postimplant calcification of tissues.MethodsFreshly obtained porcine and bovine pericardial tissues were each treated with increasing concentrations of GA (controls, 0.3125%, 0.625%, and 1.2%) for a fixed time (15 minutes) or increasing exposure times (5, 10, 20, and 30 minutes) at a fixed concentration of GA (0.625%). Pretreated tissues were subcutaneously implanted in 10-week-old Sprague-Dawley rats for 45 days before explantation. Quantitative calcium analysis was performed by flame atomic spectrophotometry. Histologic examination of tissue samples with hematoxylin and eosin and von Kossa staining was performed for cellular and inflammatory response, autolysis, and calcification.ResultsTwo-way analysis of variance indicated significantly greater calcium levels at 1.2% compared with each lower concentration for both porcine and bovine samples (P < .01). Significantly lower calcium levels were detected with increased exposure time in porcine samples (F = 6.97; P < .001); however, no significant differences in calcium levels were observed between different exposure times for bovine samples (F = 1.46; P = .23). Histologic evidence of inflammatory response with infiltration with mononuclear cells, fibroblasts, and histiocytes was seen in all grafts; however, it varied from mild to severe without any pattern. There were no differences in degree or pattern of inflammatory response according to GA concentration or time of exposure. Estimation of amount of calcification by histologic examination correlated with the quantitative assay.ConclusionsIncreasing GA concentration leads to greater calcification with a sharp rise in calcium levels above a concentration of 0.625%, in both bovine and porcine pericardial tissues. At a concentration of 0.625%, increasing pretreatment time is inversely related to tissue calcification for porcine pericardium but not for bovine pericardium. Differences in the tissue composition in terms of cellular content and composition of the extracellular matrix could account for the observed findings

Intra/extracardiac fenestrated modification leads to lower incidence of arrhythmias after the Fontan operation

ObjectiveThe study objective was to compare the incidence of short- and intermediate-term arrhythmias among 3 different surgical modifications of the Fontan procedure.MethodsWe performed a retrospective review of all patients who underwent the Fontan operation at a single institution between January 2004 and May 2010 for preoperative, perioperative, and follow-up variables. Three surgical modifications were studied: intra/extracardiac conduit with limited atriotomy, standard extracardiac conduit, and lateral tunnel. Rhythm was classified as normal or abnormal. A rhythm dysfunction grading was devised and used to identify worsening of rhythm for patients with abnormal rhythm preoperatively. Multivariable logistic regression was used to determine predictors of abnormal rhythm. To eliminate confounding effects of transient immediate postoperative arrhythmias, data were analyzed for abnormal rhythm within the first 2 weeks and for more than 2 weeks after surgery.ResultsOf the 134 patients (n = 50 with intra/extracardiac conduit with limited atriotomy, n = 19 with standard extracardiac conduit, n = 65 with lateral tunnel) (median follow-up, 36 months; interquartile range, 22–50 months; 2 operative deaths and 6 late deaths), rhythm data for more than 2 weeks postoperatively were available in 88 (40 with lateral tunnel, 14 with standard extracardiac conduit, 34 with intra/extracardiac conduit with limited atriotomy). These patients constituted the study groups. Patients in the lateral tunnel group were relatively younger at the time of the Fontan operation (P < .001) and had a longer follow-up (P < .001). Multivariable logistic regression confirmed that greater than moderate atrioventricular valve regurgitation was the only independent predictor of abnormal rhythm during the first 2 postoperative weeks. Older age at Fontan (odds ratio, 1.20; 95% confidence interval, 1.05–1.38; P = .012) and higher preoperative mean pulmonary artery pressure (odds ratio, 1.2; 95% confidence interval, 1.03–1.44; P = .026) were predictors of abnormal rhythm more than 2 weeks postoperatively. Intra/extracardiac conduit with limited atriotomy Fontan modification was associated with a significantly lower incidence of abnormal rhythm after 2 weeks postoperatively compared with lateral tunnel modification (odds ratio, 0.28; 95% confidence interval, 0.10–0.84; P = .015).ConclusionsIntra/extracardiac conduit with limited atriotomy Fontan modification has a significantly lower risk of abnormal rhythm postoperatively in the short and intermediate term when compared with the lateral tunnel

Magnesium Lowers the Incidence of Postoperative Junctional Ectopic Tachycardia in Congenital Heart Surgical Patients: Is There a Relationship to Surgical Procedure Complexity?

Magnesium sulfate was given to pediatric cardiac surgical patients during cardiopulmonary bypass period in an attempt to reduce the occurrence of postoperative junctional ectopic tachycardia (PO JET). We reviewed our data to evaluate the effect of magnesium on the occurrence of JET and assess a possible relationship between PO JET and procedure complexity. A total of 1088 congenital heart surgeries (CHS), performed from 2005 to 2010, were reviewed. A total of 750 cases did not receive magnesium, and 338 cases received magnesium (25 mg/kg). All procedures were classified according to Aristotle score from 1 to 4. Overall, there was a statistically significant decrease in PO JET occurrence between the two groups regardless of the Aristotle score, 15.3 % (115/750) in non-magnesium group versus 7.1 % (24/338) in magnesium group, P < 0.001. In the absence of magnesium, the risk of JET increased with increasing Aristotle score, P = 0.01. Following magnesium administration and controlling for body weight, surgical and aortic cross-clamp times in the analyses, reduction in adjusted risk of JET was significantly greater with increasing Aristotle level of complexity (JET in non-magnesium vs. magnesium group, Aristotle level 1: 9.8 vs. 14.3 %, level 4: 11.5 vs. 3.2 %; odds ratio 0.54, 95 % CI 0.31–0.94, P = 0.028). Our data confirmed that intra-operative usage of magnesium reduced the occurrence of PO JET in a larger number and more diverse group of CHS patients than has previously been reported. Further, our data suggest that magnesium’s effect on PO JET occurrence seemed more effective in CHS with higher levels of Aristotle complexity