Posterior Free Wall Research Articles

Effect of right and left-sided programmed atrial extrasystoles on conduction across Bachmanns Bundle and initiation of atrial fibrillation

Abstract Funding Acknowledgements Type of funding sources: None. Background Atrial extrasystoles (AES) originating from the pulmonary veins are notorious for triggering episodes of atrial fibrillation (AF). However, non-pulmonary vein triggers, emerging from e.g. the superior vena cava, left atrial posterior free wall, left atrial appendage (LAA), terminal crest and interatrial septum, play also an important role in a significant part of AF patients. AES provoke conduction disorders due to (dispersion in) refractoriness and enhanced non-uniform anisotropy of atrial tissue, which are related to initiation and perpetuation of AF. Bachmann’s bundle (BB) is the main route for interatrial conduction and plays a key role in AF development. However, the exact mechanistic effects of AES on BB in AF initiation are still unknown. Purpose To examine the impact of programmed electrical stimulation (PES) from the left and right atrium on activation and electrophysiological features of BB. Methods Intra-operative high-resolution epicardial mapping of BB was performed during sinus rhythm (SR) in 30 patients (27 male, 64±10 years). PES included a S1 sequence of 400 ms followed by a S2 of 300, 250 and 200 ms provided from the left and right atrial appendage (LAA/RAA). Electrophysiological features included unipolar voltage, conduction velocity, potential type (single, short/long double and fractionated) and conduction delay/block (CDCB). Features of the shortest captured S2 were compared to the S1 sequence. Results The average cycle length during SR was 962 [869–1085] ms. Compared to SR, during S1 pacing from both the RAA and LAA, voltage (RAA: -0.49 [-1.25–0.06] mV; LAA: -0.17 [-0.97–0.42] mV, P<0.001) and conduction velocity (RAA: -2.72 [-6.85–0.36] cm/s; LAA: -1.28 [-12.37–0.85] cm/s, P<0.001) decreased, and the amount of fractionation increased. In addition, CDCB increased specifically during RAA S1 pacing (+1.8 [0.1–3.2]%, P<0.001), while total activation time increased during LAA pacing (+16 [-1–29] ms, P<0.001). Applying the maximal captured S2, 12 patients had a refractory period of 250 ms, 13 patients of 200 ms and 3 patients <200 ms. In 4 patients, AF was induced by a S2 of 250 or 200 ms from either RAA or LAA. During both RAA and LAA S2 pacing, voltage (RAA: -1.33 [-2.51–-0.64] mV; LAA: -0.91 [-1.64–-0.46] mV, P<0.001) and conduction velocity (RAA: -16.34 [-24.49–-6.70] cm/s; LAA: -8.63 [-19.95–-1.25] cm/s, P<0.001) decreased, while total activation time (RAA: +26 [11–59] ms; LAA: +21 [2–46] ms, P<0.001) and CDCB (RAA: +5.7 [3.5–11.7] %; LAA: +4.1 [0.4–6.5] %, P<0.001) increased. Specifically, the average length of CDCB lines increased remarkably during LAA S2 pacing (+22 [8–39] mm, P<0.001) and even more during RAA S2 pacing (+36 [19–80] mm, P<0.001). Conclusions Premature AES affect interatrial conduction via BB by enhancing conduction disorders. This indicates that BB is involved in AF initiation by ectopic beats, independently of their origin from the right or left atrium.

Contraction Patterns of Post-Fontan Single Right Ventricle Versus Normal Left and Right Ventricles in Children: Insights From Principal Strain Analysis

Principal strain (PS) analysis quantifies three-dimensional myocardial deformation using three-dimensional speckle-tracking echocardiography. It defines both the amplitude and direction of the principal myocardial contraction, expressed as PS, and a perpendicular secondary strain of lower intensity. The aims of this study were to apply PS analysis to describe the contractile pattern in the single right ventricle (SRV) functioning as a systemic chamber in hypoplastic left heart syndrome, compared with the normal left ventricle (LV) and right ventricle (RV), and to compare SRV function using conventional echocardiographic evaluations. Fifty-four post-Fontan patients with hypoplastic left heart syndrome and age-matched control subjects (normal LV, n=64; normal RV, n=48) underwent computation of PS lines, ejection fraction (EF), end-diastolic volume indexed to body surface area, PS, secondary strain, circumferential strain, and longitudinal strain. The PS lines were compared between groups. Linear regressions with coefficient determination (R2) of strains, fractional area change, and tricuspid annular plane systolic excursion with EF and end-diastolic volume index were assessed in SRV. Additionally, the hypoplastic left heart syndrome cohort was equally divided into two groups with higher and lower EFs, followed by comparison of all parameters. The pattern of PS lines demonstrated a left-handed direction in the anterior free wall, a right-handed direction in the posterior free wall, and a circumferential direction in the medial wall in SRV. In contrast, in the normal LV, the principal contraction is in the circumferential direction, whereas in the normal RV, it is predominantly longitudinal. The R2 values for PS, secondary strain, and circumferential strain on EF were high (0.88, 0.72, and 0.90, respectively), whereas the R2 value for longitudinal strain was comparable with that for fractional area change (0.56 and 0.55). All parameters were independent of end-diastolic volume index. PS lines in the higher EF group showed a more circumferential orientation than in the lower EF group in SRV. PS analysis provides a unique functional map of SRV contraction. This map differs from corresponding maps of the normal LV and RV. This may be helpful in understanding the mechanisms of SRV function, although future longitudinal studies are needed.

Thoracoscopic Trans-mitral Septal Myectomy for Hypertrophic Obstructive Cardiomyopathy in the Elderly

BackgroundThe thoracoscopic trans-mitral approach can not only facilitate exposure of the ventricular septum, mitral valve, and subvalvular apparatus, it also enables the surgeons to perform concomitant mitral valve intervention. This study aimed to determine the safety and efficacy of thoracoscopic trans-mitral septal myectomy in elderly patients with hypertrophic obstructive cardiomyopathy (HOCM).MethodsWe reviewed the demographic to clinical characteristics and outcomes of patients who underwent thoracoscopic trans-mitral septal myectomy in our center between April 2019 and April 2021. The population was divided into a younger group (<60 years) and an elderly group (≥60 years).ResultsThere were 46 and 20 patients in the younger and elderly groups, respectively. The majority of patients in the elderly group were female (39.1 vs. 80.0%, P < 0.01). Patients in the elderly group were more likely to be in New York Heart Association Class IV (2.2 vs. 80.0%, P < 0.01). The European System for Cardiac Operation Risk Evaluation II predicted mortality rates were significantly higher (3.97 ± 1.81 vs. 1.62 ± 0.86%, P < 0.01) in the elderly group. In the elderly group, a patient converted to median sternotomy due to left ventricular posterior free wall rupture following septal myectomy and mitral bioprosthetic valve replacement. The patient then underwent double-patch sandwich repair for rupture and mitral mechanical valve replacement and was eventually discharged. All patients in the elderly group were discharged, while one in the younger group died. No patient in the elderly group required permanent pacemaker implantation vs. one in the younger group. Patients in the elderly group were more likely to spend more time in the intensive care unit than those in the younger group (5.44 ± 5.80 days vs. 3.07 ± 2.72, P < 0.05). However, there was no significant intergroup difference in in-hospital mortality or complications. Importantly, the left ventricular outflow tract pressure gradient was significantly decreased from 96.15 ± 32.89 mmHg to 8.2 ± 3.42 mmHg with no residual obstruction in the elderly group. The interventricular septal thickness was significantly decreased from 19.73 ± 3.14 mm to 11.30 ± 2.23 mm. Postoperative mitral regurgitation severity was significantly improved in the elderly group.ConclusionThis study demonstrated that thoracoscopic trans-mitral septal myectomy is a feasible option for selected elderly patients with satisfactory outcomes similar to those of young patients.

Efficacy and safety of segmental radiofrequency ablation for isolation of the superior vena cava in patients with atrial fibrillation

Objective: To analyze the three-dimensional distribution of functional sinus node, right phrenic nerve and superior vena cava(SVC)-right atrial muscle sleeves by three-dimensional electrophysiological technique in patients with atrial fibrillation (AF), and to investigate the efficacy and safety of segmental radiofrequency catheter ablation (RFCA) for isolation of superior vena cava in these patients. Methods: In this retrospective study, we enrolled 136 AF patients who underwent first RFCA in the First Affiliated Hospital of Zhengzhou University from July 2018 to June 2019 and all patients underwent SVC isolation under sinus rhythm. Baseline clinical data of patients were collected. The functional sinus node was defined by activation mapping, pacing was guided by three-dimensional mapping (Carto) system, localization of the right phrenic nerve was defined by pacing map, the superior vena cava-right atrial muscle sleeves was determined according to the change of potential during SVC isolation, segmental RFCA was performed for SVC isolation, the three-dimensional distribution of functional sinus node, right phrenic nerve and superior vena cava(SVC)-right atrial muscle sleeves was determined by three-dimensional electrophysiological technique. Immediate SVC isolation was achieved in all patients. Patients were evaluated immediately after RFCA and patients were followed at 3, 6, 9, and 12 months after RFCA. Holter monitoring was performed every 3 months, the chest radiograph and the SVC ultrasonic examination were performed every 6 months after RFCA. Postoperative complications were assessed. Results: The mean age of the 136 patients with AF was (51.6±14.2) years, 86 (63.2%) were male, 98 cases (72.1%) were paroxysmal AF and 38 cases (27.9%) were persistent AF. Right atrium activation mapping revealed that 17 (12.5%) functional sinus node were located in the SVC, 78 (57.4%) were located at the SVC-right atrium junctions, 41 (30.1%) were located below the junction level. From the head to foot view, 83 (61.0%) functional sinus node were located at the anterior lateral segment of the SVC-right atrium three-dimensional reconstruction model, 34 (25.0%) located at the posterior lateral segment, 15 (11.0%) located at the anterior wall, 4 (2.9%) located at posterior wall or anterior septum. A total of 294 SVC muscle sleeves were detected among all patients, 94 (32.0%) SVC muscle sleeves were located at the anterior septum of the SVC-right atrium three-dimensional reconstruction model, 76 (25.9%) were located at the posterior septum, 21(7.1%) were located at the posterior free wall, 11 (3.7%) were located at the posterior lateral, 27 (9.2%) were located at anterior lateral wall and 65 (22.1%) were located at the anterior free wall. Right phrenic nerve positioned relatively fix, 133 (97.8%) were located at the lateral segment of the SVC-right atrium three-dimensional reconstruction model, 3 (2.2%) were located at the anterior free wall. Sinus rhythm and SVC isolation were successfully restored immediately after RFCA, no significant SVC stenosis, right phrenic nerve palsy and functional sinus node injury occurred immediately post procedure. All patients were followed up for (11.2±3.6) months and none had postoperative complication. Conclusions: Three-dimensional electrophysiological can determine the spatial location of functional sinus node, right phrenic nerve and SVC-right atrial sleeves. On this basis, segmental RFCA is a safe and effective method to achieve complete isolation of SVC.

Improving Prediction of Acute Right Ventricular Failure in Patients Undergoing Left Ventricular Assist Devices Using Novel Comprehensive Eighteen-Segment Echocardiographic Strain Analysis

<h3>Purpose</h3> The complex anatomy and different contraction patterns of the different right ventricular (RV) wall segments has made it challenging to predict acute RV failure (ARVF) in patients receiving a left ventricular assist device (LVAD). We sought to improve the prediction of ARVF after LVAD by performing a comprehensive 18-segment strain (ε) analysis of the RV. <h3>Methods</h3> Prospectively enrolled LVAD recipients had a right heart catheterization and echocardiogram prior to implant. From RV-focused views (Figure 1A), 18-segment ε was performed and indexed to pulmonary arterial elastance (Ea [PV]). ARVF was defined as need for RVAD, inotropes for >14 days or pulmonary vasodilator for >48 hours post-LVAD. Logistic regression was used to identify associations between specific parameters and ARVF. <h3>Results</h3> ARVF occurred in 15 of 30 patients enrolled. Lower pulmonary artery pulsatility index (PAPi), TAPSE and basal free wall (FW) (basal anterior, lateral and posterior FW) segmental ε/Ea (PV) were significantly associated with ARVF. Indexed basal FW segmental strain provided incremental predictive value over PAPi and TAPSE (Figure 1B). <h3>Conclusion</h3> Prediction of ARVF in LVAD candidates can be improved by adding comprehensive RV segmental strain analysis to traditional echocardiographic and hemodynamics parameters.

Diastolic dysfunction in patients with brucellosis despite the absence of infective endocarditis.

Brucellosis is an important systemic infectious disease, especially in developing countries. Every organ and system of the human body can be affected; however, cardiovascular complications of brucellosis are rare. To assess cardiac functions in patients with acute brucellosis without overt cardiac involvement and to answer the following question: Is there any cardiac dysfunction despite the absence of endocarditis in these patients? This cross-sectional study included 67 children with brucellosis and 40 healthy children. We performed a detailed echocardiographic examination in individuals at the beginning of the treatment. Patients with infective endocarditis were excluded from the study. Echocardiography revealed no difference of ejection fraction, mitral and tricuspid annular plane systolic excursion, pulsed-wave Doppler-derived early diastolic peak velocity (E)/late diastolic peak velocity (A) ratios in mitral and tricuspid valves between the two groups. The deceleration time of early mitral inflow was longer in patients with brucellosis. Early diastolic peak velocity of the mitral and tricuspid annuluses obtained by tissue Doppler imaging (Ea) was significantly lower in children with brucellosis. The peak velocity obtained by tissue Doppler imaging during late diastole (Aa), Ea and Ea/Aa ratios in the interventricular septum, left ventricle posterior wall and right ventricle free wall was lower in patients with brucellosis than in the control group. The E/Ea ratio, isovolumic relaxation time, right ventricle and left ventricle myocardial performance indices were higher in patients with brucellosis. Patients with acute brucellosis may have diastolic dysfunction without overt cardiac involvement and infective endocarditis.

Reference Values and Repeatability of B-Mode and M-Mode Echocardiographic Parameters in Healthy Donkey (Equus asinus)—The Guide to Assess Healthy Heart

Donkey (Equus asinus), the cheapest form of agricultural power in Egypt, is used principally as draught or pack animals and may also be ridden, or used for threshing, raising water, milling, and other work. The aim of the present study was to provide B-mode and M-mode echocardiographic reference ranges from a sample of population of donkeys (E. asinus) based on the probability theory and statistics. In the present study, B-mode and 2-dimensional guided M-mode echocardiography were performed on 44 clinically healthy donkeys (E. asinus) (22 males and 22 females), without any neither clinical nor echocardiographic evidence of cardiovascular diseases, aged 2–25 year old, and weighed 150–350 kg. The echocardiographic dimensions, including interventricular septum thickness at end diastole, interventricular septum thickness at end systole, left ventricular internal diameter at end diastole, left ventricular internal diameter at end systole, left ventricular posterior wall thickness at end diastole, and left ventricular posterior wall thickness at end systole were assessed. The cardiac function indices, including end diastolic volume, end systolic volume, stroke volume, ejection fraction, and fractional shortening were also measured. B-mode and guided M-mode echocardiographic examination of healthy donkeys revealed that both the interventricular septum thickness and the left ventricular posterior free wall were greater during systole than diastole. However, the left ventricular dimension during diastole was greater than systole. Furthermore, the recorded data of cardiac function indices, including end diastolic volume, end systolic volume, stroke volume, ejection fraction, and fractional shortening using B-mode echocardiography were closer to those recorded by guided M-mode echocardiography. To our knowledge, this is the first Egyptian study to report the echocardiographic reference ranges of donkeys (E. asinus) based on the probability theory and statistics, the coefficient of variation. The results of the present study can be used as standard and reference values for further echocardiographic studies in donkeys and represent a step in the identification, interpretation, and evaluation of cardiovascular disorders in such animals.

Interventricular septal hematoma complicating placement of a ventricular assist device in an infant and support with bi-atrial cannulation.

Interventricular septal hematoma complicating placement of a ventricular assist device in an infant and support with bi-atrial cannulation.

P251 Right ventricular free wall dissection clearly detected and recorded by echocardiography: a fatal complication after inferior myocardial infarction

Abstract An 81-year-old man was transferred to our institution by ambulance because of poor feeding, general fatigue and slight disorientation lasting for a week. On arrival, he was awake and able to speak, however, his blood pressure was low at 61/43 mmHg in spite of his medical history of hypertension. His ECG showed abnormal Q waves and ST elevation in II, III, aVF leads. The echo exam detected severe hypokinesis in the left ventricular inferior wall and reduced ejection fraction at 30%. Pericardial effusion was not observed in the first echo exam. The patient was diagnosed as cardiogenic shock due to recent inferior myocardial infarction. Coronary angiography was performed, which detected total occlusion of mid right coronary artery, followed by a successful percutaneous coronary intervention (PCI) with a drug-eluting stent under the support of intra-aortic balloon pumping. Nevertheless, his blood pressure remained low and intravenous adrenaline administration was necessary during and even after PCI. To detect the cause of prolonged low blood pressure, echo was performed again immediately after PCI. The echo exam detected new findings: right ventricular posterior free wall was dissected and abnormal shunt flows were obviously observed from left ventricle to right atrium through the dissection cavity during systole. An urgent surgical repair was considered as the only option for his survival, however, his family did not accept it because the operation itself was too risky. On the next day of his admission, he passed away. Right ventricular free wall dissection is a very rare but fatal complication after inferior myocardial infarction, nevertheless, we could detect it by echocardiography with clearly recorded images. Abstract P251 Figure.

Right ventricular free-wall scar: an exceptional source of post-infarction ventricular tachycardia. A case report.

Background In patients with coronary artery disease, ventricular tachycardia (VT) is usually related to left ventricular (LV) post-infarction scars.Case summaryA case of a 78-year-old man with post-infarction VT originating from the right ventricular (RV) free wall is described. Following recurrent episodes of VT with left bundle branch block morphology and left superior axis deviation, a patient with prior myocardial infarction was submitted to catheter ablation. Two areas of abnormal bipolar electrograms were observed at 3D electroanatomical mapping: one located at the basal aspect of the posterior and postero-septal LV, and the other one extending from the antero-lateral to the posterior mid-basal RV free wall. Ventricular late potentials (LPs) were recorded within both scars, but only pacing from those located in the RV resulted in long stimulus-to-QRS latency and optimal pace-mapping. Accordingly, this substrate was deemed the culprit of the clinical VT. Radiofrequency catheter ablation aimed at eliminating all LPs recorded from both scars was effective in preventing VT recurrences at follow-up.DiscussionA post-infarction RV free-wall scar may exceptionally be responsible of VT occurrence. Right ventricular mapping should be considered in selected cases based on 12-lead electrocardiogram VT morphology and prior RV infarct.

Application of nonlinear methods to discriminate fractionated electrograms in paroxysmal versus persistent atrial fibrillation

Background and ObjectiveComplex fractionated atrial electrograms (CFAE) may contain information concerning the electrophysiological substrate of atrial fibrillation (AF); therefore they are of interest to guide catheter ablation treatment of AF. Electrogram signals are shaped by activation events, which are dynamical in nature. This makes it difficult to establish those signal properties that can provide insight into the ablation site location. Nonlinear measures may improve information. To test this hypothesis, we used nonlinear measures to analyze CFAE. MethodsCFAE from several atrial sites, recorded for a duration of 16 s, were acquired from 10 patients with persistent and 9 patients with paroxysmal AF. These signals were appraised using non-overlapping windows of 1-, 2- and 4-s durations. The resulting data sets were analyzed with Recurrence Plots (RP) and Recurrence Quantification Analysis (RQA). The data was also quantified via entropy measures. ResultsRQA exhibited unique plots for persistent versus paroxysmal AF. Similar patterns were observed to be repeated throughout the RPs. Trends were consistent for signal segments of 1 and 2 s as well as 4 s in duration. This was suggestive that the underlying signal generation process is also repetitive, and that repetitiveness can be detected even in 1-s sequences. The results also showed that most entropy metrics exhibited higher measurement values (closer to equilibrium) for persistent AF data. It was also found that Determinism (DET), Trapping Time (TT), and Modified Multiscale Entropy (MMSE), extracted from signals that were acquired from locations at the posterior atrial free wall, are highly discriminative of persistent versus paroxysmal AF data. ConclusionsShort data sequences are sufficient to provide information to discern persistent versus paroxysmal AF data with a significant difference, and can be useful to detect repeating patterns of atrial activation.

Regional modulation of action potential duration and arrhythmias by ß1- and ß2-adrenergic receptor stimulation in the porcine right ventricle

The right ventricular outflow tract (RVOT) is the main origin of idiopathic ventricular tachycardia (IVTs). Sympathetic stimulation is involved in IVTs but mechanisms underlying this preferential origin remain unknown. To determine the role of ß1- and ß2-adrenergic receptors (ß1-AR, ß2-AR) in the regional modulation of right ventricular (RV) electrophysiological properties and arrhythmias. Porcine RVs were isolated and perfused via both right and left coronary arteries. Epicardial (EPI) electrical activity was optically mapped (di-4-ANEPPS 20 μM) and APD measured at 80% repolarization (APD80) in the RVOT and posterior RV free wall region (RVFW). Regional mRNA and protein expression for ß1-AR and ß2-AR was determined respectively by RT-PCR and Western-Blot. Combined ß1- and ß2-AR stimulation (50 nM isoprenaline, ISO) shortened APD80 EPI with a larger effect in the RVFW than the RVOT. Interestingly, isolated ß2-AR stimulation (10–25 μM salbutamol, SALBU with 4 μM metoprolol, METO) only decreased APD80 significantly in the RVOT EPI ( P < 0.05). ß2-AR stimulation did not affect APD80 in the RVOT endocardium leading to a larger transmural APD gradient in this region ( P < 0.01). ß1-AR expression was lower in the RVOT than in the RVFW EPI at the mRNA and protein levels. Conversely, ß2-AR protein expression was greater in the RVOT EPI ( P < 0.05). ISO (1.8 nM–1 μM) led to a significant increase in spontaneous arrhythmias while isolated ß2-AR did not (SALBU 10–50 μM). At higher concentrations (500nM-1 μM) ISO triggered VT episodes that originated from the RVOT or the anterior RV. ß2-AR blockade (ICI 118,551 100 nM) accelerated while ß1-AR blocker METO (4 μM) slowed or abolished VT. Conlcusion These results suggest a ß2-AR specific regulation of RVOT electrophysiology but its role in the triggering of arrhythmias in this region requires further studies.

Mitral annular disjunction in mitral valve prolapse: A Cardiac Magnetic Resonance study

Few data exist on cardiac magnetic resonance (CMR) prevalence of mitral annulus disjunction (MAD) in mitral valve prolapse (MVP) and its morphological characteristics. To assess the prevalence of MAD and its consequences on left ventricle (LV) morphology in MVP patients using CMR. 89 patients with MVP (63 women; mean age 64 ± 13) referred for CMR assessment of mitral regurgitation (MR) were evaluated. MVP etiology was either Myxomatous Mitral Valve Disease (MMVP) ( n = 40; 45%) or fibroelastic disease (FED) ( n = 49; 55%). In total, 26/89 (29%) patients underwent injected gadolinium contrast enhancement (GE). MR severity was calculated using the volumetric method with CMR. LV systolic diameter (LVSD), and mitral annulus end systolic (ES) and diastolic (ED) diameters were measured. MAD was defined as a separation between the left atrium-valve junction and the LV posterior free wall, diagnosed by CMR from long axis view in end-systole ( Fig. 1 ). Patients were classified in 2 groups according to presence (MAD+) or absence of MAD (MAD−). MAD was found in 35% (31/89) of MVP patients, measuring 8 ± 4 mm. MAD was more frequent in MMVP (24/40; 60%) than in FED (7/49; 14%; P < 0.0001). Presence of MAD was associated with ventricular arrhythmias (VA) ( P = 0.037), but not with MR severity (regurgitant volume in MAD+ was 47 ± 32 vs. 56 ± 23 ml/beat, P = 0.141). MAD+ showed enlarged basal LVSD (41 ± 9 vs. 37 ± 7 mm, P = 0.014) and mitral annulus, in both ES (49 ± 6 vs. 44 ± 5 mm, P < 0.0001) and ED (48 ± 5 vs. 44 ± 4 mm, P = 0.004). Among the 11/26 patients (42%) with late GE, 83% (5/6) of the patients with LV fibrosis at the level of papillary muscle (PM) had MAD. After adjustment on age and MR severity, MMVP (HR 5.04; 95% CI [1.66–15.31], P = 0.004) and dilated ES mitral annulus diameter (HR 1.17; 95% CI [1.05–1.30], P = 0.005) were independent predictors of MAD ( Table 1 ). MMVP, enlarged LVSD, enlarged mitral annular, VA and PM fibrosis were associated with MAD, independently of MR severity.

Regional β-adrenergic regulation of action potential duration and arrhythmias in the pig right ventricle

The right ventricular outflow tract (RVOT) is the main origin of idiopathic ventricular tachycardia (VT). Although these arrhythmias appear to be cAMP-dependent, the actual mechanisms leading to VT remain uncertain. Here we studied β-adrenergic regulation of action potential duration (APD) in the healthy pig right ventricle (RV). To determine regional β-adrenergic regulation of APD and arrhythmias in the RVOT. The RV of 4 pig hearts were isolated and perfused via both the coronary arteries. Epicardial electrical activity was optically mapped (di-4-ANEPPS 20 μM) and APD measured at 80% repolarization (APD80) in the RVOT and posterior RV free wall region (RVFW). Regional mRNA and protein expression of β-adrenergic receptors was determined respectively by RT-PCR and Western-Blot. The expression of β1-adrenergic receptor (β1-AR) was lower in the RVOT at the mRNA level ( P < 0.05) but remained unchanged at the protein level compared to the RVFW while β2-adrenergic receptor (β2-AR) expression remained similar in both regions. At lower concentrations (0.6–10 nM), isoprenaline (ISO) led to a prolongation of APD80 in the RVOT and the RVFW. Higher ISO concentrations (500 nM–1 μM) led to a larger APD80 shortening in the RVOT than in the RVFW and triggered VT episodes that originated from the RVOT or the anterior RV. β2-AR blockade (ICI 118,551 100 nM) accelerated while β1-AR blocker Metoprolol (4 μM) slowed or abolished VT. Similar ISO concentrations triggered bursts of Ca2+ transients in RVOT myocytes that stopped upon ISO washout while these events remained rare in RVFW myocytes. β-adrenergic stimulation differentially regulates APD80 in the RVOT and RVFW. Although β1-AR expression was similar in the 2 regions, ISO preferentially shortened APD and triggered arrhythmia in the RVOT. These results suggest the presence of a high sensitivity of RVOT electrophysiology to β-adrenergic stimulation.

Adaptation to acute pulmonary hypertension in pigs.

The extent of right ventricular compensation compared to the left ventricle is restricted and varies among individuals, which makes it difficult to define. While establishing a model of acute pulmonary hypertension in pigs we observed two different kinds of compensation in our animals. Looking deeper into the hemodynamic data we tried to delineate why some animals could compensate and others could not. Pulmonary hypertension (mean pressure 45 mmHg) was induced gradually by infusion of a stable thromboxane A2 analogue U46619 in a porcine model (n = 22). Hemodynamic data (pressure‐volume loops, strain‐analysis of echocardiographic data and coronary flow measurements) were evaluated retrospectively for the short‐term right ventricular compensatory mechanisms and limits (Roehl et al. [2012] Acta Anaesthesiol. Scand., 56:449–58) 10 animals showed stable arterial blood pressures, whereas 12 pigs exhibited a significant drop of 16.4 ± 9.9 mmHg. Cardiac output and heart rate were comparable in both groups. In contrast, right ventricular contractility and coronary flow only rose in the stable group. The unchanging values in the decrease group correlated with an increasing ST‐segment depression and a loss of ventricular synchronism and resulted in a larger septum bulging to the right ventricle. Simultaneously, a reduced left‐ventricular end‐diastolic volume and a missing improvement in contractility in the posterior septal and inferior free wall of the left ventricle have been observed. Our findings suggest that right ventricular compensation during acute pulmonary hypertension is strongly dependent on the individual capability to increase coronary flow. The cause for inter‐individual variability could be the dimension and reactivity of the coronary system.

Inferior ischemic ventricular septal defect: Atypical triple pericardial patch implantation technique

We presented the successful management of an inferior ischemic ventricular septal defect (VSD) associated with posterior left ventricular free wall rupture, following the occlusion of a dominant right coronary artery (RCA). The defect was approached through a longitudinal incision over the infarcted area, 1 cm parallel to the posterior descending coronary artery (PDA). The VSD was repaired using three pericardial patches and GRF (gelatin-resorcinol-formaldehyde) glue. ECMO and IABP were used in order to decrease the LV wall tension, the risk of recurrence of VSD and the risk of free wall rupture. The postoperative echocardiogram documented good biventricular geometry with a left ventricle ejection fraction (LVEF) of 55%. No left-to-right shunt was seen

The effect of electrode density on the interpretation of atrial activation patterns in epicardial mapping of human persistent atrial fibrillation

Mechanisms sustaining human persistent atrial fibrillation (AF) remain debated, with significant differences between high-density epicardial and global endocardial mapping studies. A key difference is the density of recording electrodes. We aimed to determine the differences in the prevalence of different atrial activation patterns, and specifically in the prevalence of rotational activations, with varying densities of bipolar electrodes. Epicardial mapping was performed in 10 patients undergoing cardiac surgery, with bipolar electrograms recorded using a triangular plaque (6.75 cm(2) area; 117 bipoles; 2.5-mm inter-bipole spacing) applied to the left atrial posterior wall or right atrial free wall. Dynamic wavefront mapping based on the timing of atrial electrograms was applied to 2 discrete 10-second AF segments. The spacing between bipolar electrode locations was increased from 2.5 × 3.5 mm in the horizontal and oblique directions to 5.0 × 3.5, 5.0 × 7.1, and 7.5 × 10.6 mm, with wavefront mapping repeated at each density. As density reduced, there was a significant change in relative proportions of the various activation patterns (F=3.69; P < .001). Simple broad wavefront activations became more prevalent (20% ± 8% to 54% ± 8%; P < .05) and complex patterns became less prevalent (48% ± 8% to 9% ± 8%; P < .05) with reducing density. The prevalence of rotational activity declined with bipole density, from median 5.0% (range 0.9%-12.1%) to 0% (range 0%-1.5%) (P = .03). The largest change occurred between inter-bipole spacings of 5.0 × 3.5 and 5.0 × 7.1 mm. Apparent activation patterns in persistent AF vary significantly with electrode density. Low density underestimates the prevalence of complex and rotational patterns. The largest difference occurs between an inter-bipole spacing of 5.0 × 3.5 and a spacing of 5.0 × 7.1 mm. This may have important implications for mapping technology design.

Histological evidence of inflammatory reaction associated with fibrosis in the atrial and ventricular walls in a case-control study of patients with history of atrial fibrillation.

Chronic inflammation in the atrial myocardium was shown to play an important role in the development of atrial fibrosis in patients with atrial fibrillation (AF). However, it is not clear to what extent atrial inflammatory reaction associated with AF extends on the ventricular myocardium. Our aim was to assess the extent of fibrosis and lymphomononuclear infiltration in human ventricular myocardium and explore its association with AF. Medical records from consecutive autopsies were checked for presence of AF. Heart specimens from 30 patients died from cardiovascular causes (64 ± 12 years, 17 men) were collected in three equal groups: no AF, paroxysmal AF, and permanent AF. Tissue samples were taken from the Bachmann's bundle, crista terminalis, posterior left atrium, left ventricle and right ventricle free walls and stained with Masson's trichrome for analysis of fibrosis extent. Immunohistochemistry was performed using antibodies against CD3- and CD45-antigens and quantified as number of antigen-positive cells per 1 mm2. Fibrosis extent, CD3+ and CD45+ cell counts were elevated in AF patients at all sites (P < 0.001 for all). Fibrosis extent demonstrated correlation with both CD3+ and CD45+ cell counts in the right (r = 0.781, P < 0.001 for CD45+ and r = 0.720, P < 0.001 for CD3+) and the left (r = 0.515, P = 0.004 for CD45+ and r = 0.573, P = 0.001 for CD3+) ventricles. Neither fibrosis nor inflammatory cell count showed association with either age or comorbidities. Histological signs of chronic inflammation affecting ventricular myocardium are strongly associated with AF and demonstrate significant correlation with fibrosis extent that cannot be explained by cardiovascular comorbidities otherwise.

Ultrastructural myocardial changes in seven cats with spontaneous hypertrophic cardiomyopathy

ObjectivesHypertrophic cardiomyopathy (HCM) is the most common heart disease in cats and shares clinical and pathological characteristics with human HCM. Little is known about the pathogenic mechanisms underlying development of spontaneous feline HCM. AnimalsThe study population consisted of seven cats diagnosed with HCM and eight age-matched cats with no evidence of cardiac disease. MethodsFresh myocardial biopsies taken from the middle of the left ventricular posterior free wall were obtained and examined with transmission electron microscopy. ResultsElectron microscopic examination showed ultrastructural aberrations of the myocardial cytoarchitecture and of the interstitium in the seven cats with HCM. In the most severely affected cats the myofibrils were disorganized and subsarcolemmal mitochondria were depleted. In control cats, contraction band artifacts were commonly seen. ConclusionsIn this preliminary study we show that ultrastructural changes of the myocardium in seven cats with HCM involve the cytoskeleton and mitochondria. We suggest that our findings are important for future research aiming at elucidating the pathogenic mechanisms underlying the phenotypic expression of feline HCM.The results of this study prompt for a larger scale study, including quantitative measurements of mitochondrial distribution and cytoskeletal derangements in feline HCM.

Repair of a simple total anomalous pulmonary venous connection coexisting with a persistent left superior vena cava.

A simple total anomalous pulmonary venous connection (TAPVC) coexisting with a persistent left superior vena cava (PLSVC) is extremely rare. Connection of the PLSVC with the coronary sinus behind the left atrium induces coronary sinus dilatation. This reduces the free posterior wall space to which the common pulmonary vein is anastomosed for repairing the anomalous connection. Postoperative recurrent pulmonary venous obstruction (PVO) is the most important complication. To prevent PVO, sufficient tension-free anastomosis is necessary. When dilated, the coronary sinus becomes an obstacle for obtaining sufficient incision length in the left atrial cavity. We encountered two cases of a simple TAPVC with a PLSVC in infants weighing 1.8 and 2.9 kg, respectively. To obtain sufficient incision length, we extended the incision line to the right atrium for an atypical supracardiac TAPVC and incised from the left atrium to the coronary sinus via the right atrium for an infracardiac TAPVC. Moreover, we recreated the atrial septum with a rightward shift using a tanned pericardium in both cases. The postoperative courses were uneventful, without recurrent PVO.