Right Atrial Wall Research Articles

Evaluation of the cavotricuspid isthmus contractile kinetics within an interventional CMR environment

Abstract Background Cavotricuspid isthmus (CTI)-dependent flutter is a common arrhythmia with recurrences following ablation up to 50%. Previous static morphological analysis have shown that CTI anatomical variability has an impact on ablation time and procedural success. However, whether the contractile kinetics of the CTI affect procedural success remains unknown to date. Purpose Assessment of the contractile kinetics of the CTI in a cardiac magnetic resonance (CMR) environment for patients (pts) referred for typical flutter ablation. Method 32 consecutive pts with typical right atrial (RA) flutter from our Heart Center were included in this study. RA wall contours during a single cardiac cycle were delineated on CMR 2D-images using the Tomtec software. CTIs were divided in 5 segments for detailed motion analysis as shown in the figure 1A. CTI length and displacement were measured both in caudo-cranial and postero-anterior directions. Quantification of the CTI kinetics was performed in Python by computing the 2D-Euclidean distance (between two extreme temporal positions of CTI points). Results The mean CTI length of the study population (mean age 66±10 years, 29 males) was 32±13 mm during RA systole and 49±15 mm during RA diastole, resulting in a mean CTI change of 17±7 mm over one cardiac cycle (maximum – minimum length). Figure 1A shows representative MRI views of the CTI during RA systole and diastole. Figure 1B shows examples of hypo- and hyperkinetics CTI from 2 representative pts. Figure 2C shows a gradual increase in segment displacement postero-anteriorly (8.1±7.3 vs 17.2±8.1 mm, p<0.05) and caudo-cranially (1.6±0.8 vs 4.5±2.4 mm) from the Eustachian valve toward the Tricuspid valve. Figure 2D indicates that the 2D-Euclidean displacement of the 5 segments varied between 8±7.7 mm and 18±8.5 mm depending on their location. Interestingly, the overall CTI displacement was 4.5 times greater forward than upward. Conclusion To our knowledge, this is the first study investigating the kinetics properties of the CTI in sinus rhythm of patients with typical RA flutter. The CTI showed displacements both in postero-anterior and caudo-cranial directions, with a gradual increase from the Eustachian to the Tricuspid valves. CTI displacement appeared highly variable across patients. Whether the kinetics of the CTI correlate with ablation success will be investigated shortly.

Right atrial wall inflammation detected by 18F-FDG PET/CT may be significantly associated with persistent atrial fibrillation: a prospective case-control study

AimAtrial fibrillation (AF) is a progressive disease from paroxysmal to persistent, and persistent AF (PerAF) had worse prognosis. AF has potential link with inflammation, but it is not clear whether PerAF or paroxysmal AF (ParAF) is more closely related to inflammation. On the basis of inhibiting myocardial physiological uptake, 18F-fluorodeoxyglucosepositron emission tomography/computed tomography (18F-FDG PET/CT) is an established imaging modality to detect cardiac inflammation. We aimed to decipher the association between AF and atrial inflammatory activity by 18F-FDG PET/CT.MethodsThirty-five PerAF patients were compared to age and sex matched ParAF group with baseline 18F-FDG PET/CT scans prior to radiofrequency catheter ablation (RFCA) in the prospective case-control study. High-fat and low-carbohydrate diet and prolonged fast (HFLC+Fast) was applied to all AF patients before PET/CT. Then 22 AF patients with positive right atrial (RA) wall FDG uptake (HFLC+Fast) were randomly selected and underwent HFLC+Fast+heparin the next day. The CHA2DS2-VASc score was calculated to evaluate the risk of stroke. Clinical data, ECG, echocardiography, and atrial 18F-FDG uptake were compared.ResultsPerAF patients had significantly higher probability of RA wall positive FDG uptake and higher SUVmax than ParAF group [91.4% VS. 28.6%, P < 0.001; SUVmax: 4.10(3.20–4.90) VS. 2.60(2.40–3.10), P < 0.001]. Multivariate logistic regression analyses demonstrated that RA wall SUVmax was the independent influencing factor of PerAF (OR = 1.80, 95%CI 1.02–3.18, P = 0.04). In 22 AF patients with RA wall positive FDG uptake (HFLC+Fast), the “HFLC+Fast+Heparin” method did not significantly change RA wall FDG uptake evaluated by either quantitative analysis or visual analysis. High CHA2DS2-VASc score group had higher RA wall 18F-FDG uptake [3.35 (2.70, 4.50) vs, 2.8 (2.4, 3.1) P = 0.01].ConclusionsRA wall FDG positive uptake was present mainly in PerAF. A higher RA wall 18F-FDG uptake was an independent influencing factor of PerAF. RA wall FDG uptake based on 18F-FDG PET/CT may indicate pathological inflammation.Trial registrationhttp://www.chictr.org.cn, ChiCTR2000038288.

Right Atrial Phasic Function in Heart Failure with Preserved Ejection Fraction: Cardiac Magnetic Resonance Feature Tracking and Outcomes.

This study sought to investigate the prognostic impact of right atrial (RA) size and function in patients with heart failure with preserved ejection fraction (HFpEF) in sinus rhythm (SR) and atrial fibrillation (AF). Consecutive HFpEF patients were enrolled and indexed RA volumes and emptying fractions (RA-EF) were assessed by cardiac magnetic resonance imaging (CMR). For patients in SR, feature tracking of the RA wall was performed during CMR. In addition, all patients underwent right and left heart catheterization and 6 min walk distance (6MWD) and N-terminal prohormone of brain natriuretic peptide (NT-proBNP) evaluations. We prospectively followed patients and used Cox regression models to determine the association of RA size and function with a composite endpoint of heart failure hospitalization and cardiovascular death. A total of 188 patients (71% female patients, 70 ± 8 years old) were included. Ninety-two patients (49%) were in persistent AF. Eighty-five patients reached the combined endpoint during a follow-up of 69 (42-97) months. After a multivariate cox regression analysis, the impaired RA reservoir strain (HR 0.949; 95% CI [0.909-0.990], p = 0.016), the RA reservoir strain rate (HR 0.991; 95% CI [0.983-0.999], p = 0.028), the RA conduit strain (HR 0.932; 95% CI [0.879-0.988], p = 0.019), and the RA conduit strain rate (HR 0.989; 95% CI [0.881-0.997], p = 0.011) were significantly associated with a worse outcome for patients in SR. In persistent AF, no RA imaging parameter was related to outcome after a multivariate regression analysis. In HFpEF patients in SR, CMR parameters of impaired RA conduit and reservoir function are associated with dismal cardiovascular outcomes. In persistent AF, RA parameters lose their prognostic ability.

Abstract 13936: Increased Bone Morphogenetic Protein 10 in Pulmonary Hypertension

Introduction: Pulmonary Hypertension (PH) is characterized by increased right atrial (RA) stretch and pressure. The major genetic predisposing risk factor for PH involves mutations in the bone morphogenetic protein (BMP) receptor 2 (BMPR2), for which BMP9 and BMP10 are ligands. Although BMP9 is mostly produced by hepatocytes, BMP10 is predominantly produced by adult RA cardiomyocytes. Therefore, its role is of interest in PH despite an elusive BMP10 release mechanism. Hypothesis: Increased RA wall stress in PH may be a trigger for BMP10 secretion. Methods: We first investigated BMP10 gene and protein expressions, as well as BMP activity, in RA tissue samples from control (N=5) and PH-patients (N=4). We also quantified BMP10, BMP9, IL-6 and active TGF-β plasma levels in controls (N=16) and PH-patients (N=48) by ELISA. We studied BMP10 and BMP9 activities, using a BMP-inducible reporter assay. Last, we established correlations between BMP10 activity and PH clinical parameters. Results: BMP10 mRNA, protein and activity (pSMAD1/5/8 and ID3) were increased in RA tissue of PH-patients compared to controls (Figure1 A-E). BMP10, BMP9 and IL-6 plasma levels were also augmented (Figure1 F-H); while TGF-β plasma levels, and BMP10 and BMP9 activities between PH-patients and controls were preserved. Finally, we divided the PH cohort on median BMP10-activity (0.33 AU). Higher BMP10 activity in PH-patients was associated with diminished RA compliance, reduced right ventricular function, lower stroke volume and elevated NT-proBNP (Figure1 I). Conclusions: Although BMP10 plasma levels were increased, BMP10 activity was preserved in PH-patients, probably because of high inflammatory cytokines, such as IL-6. High BMP10 activity was associated with increased RA pressure and worse disease severity in PH-patients.

Right atrial function in HFpEF in sinus rhythm vs. atrial fibrillation

Abstract Aims We sought to study the prognostic impact of right atrial (RA) size and function in patients with heart failure with preserved ejection fraction (HFpEF) in sinus rhythm (SR) vs. atrial fibrillation (AF). Methods and results Consecutive HFpEF patients were enrolled and indexed RA volumes and emptying fractions (RA-EF) were assessed by cardiac magnetic resonance imaging (CMR). For patients in SR during CMR feature tracking of the RA wall was performed (Figure 1). In addition, all patients underwent right and left heart catheterization, 6 min walk test, and N-terminal prohormone of brain natriuretic peptide (NT-proBNP) evaluation. We prospectively followed patients and used Cox regression models to determine the association of RA size and function with a composite endpoint of heart failure hospitalization and cardiovascular death. A total of 188 patients (71% female patients, 70±8 years old) were included of whom 96 (51%) were in SR. Eighty-five patients reached the combined endpoint during a follow-up of 72 (33–101) months. After multivariate cox regression analysis adjusted for age, NT-proBNP level, right ventricular ejection fraction and HF functional class, impaired RA strain (Figure 1A) (HR 0.959; 95% CI [0.924–0.996], P=0.024), RA conduit strain (Figure 1A) (HR 0.944; 95% CI [0.898–0.993], P=0.027) and RA conduit strain rate (Figure 1B) (HR 0.990; 95% CI [0.883–0.998], P=0.013) were significantly associated with adverse outcome for patients in SR (Table 1). In persistent AF, no RA imaging parameter was related to outcome after multivariate regression analysis. Conclusions In HFpEF patients in SR, CMR parameters of impaired RA conduit function show the best association with adverse cardiovascular outcome. In persistent AF, RA parameters lose their prognostic ability. Funding Acknowledgement Type of funding sources: None.

Clinical and echocardiographic characteristics of patients with pathology proven right-sided papillary fibroelastomas

BackgroundPapillary fibroelastoma (PFE) are one of the most common primary cardiac neoplasms. They are most commonly found on cardiac valves especially on the left side of the heart and have been associated with an increased risk of embolization. To date, no large studies looked at the clinical significance of right-sided PFE (R-PFE). Therefore, we sought to better characterize patients with R-PFE and its clinical sequelae. MethodsWe retrospectively identified patients with pathology-proven PFEs at a single center between January 1995 and December 2018 (n = 279). Patients with R-PFE were analyzed. Medical records and echocardiograms were reviewed for clinical and PFE characteristics. ResultsTwenty-nine patients with R-PFE (mean age 70 ± 11 years; 62% women) were included in the analysis. PFEs were located on the right atrial (RA) wall in 31%, tricuspid valve in 34%, right ventricular (RV) wall in 7%, RV outflow tract in 4%, and pulmonary valve in 10% of patients. The remaining patients (14%) had multifocal PFEs. Around 38% of patients had cancer diagnosed before PFE diagnosis, and 34% had associated congenital heart disease. Seventeen (59%) patients had angina or dyspnea at the time of the presentation, and 3 (10%) had embolic symptoms. One patient with PFE located on the RA with associated patent foramen ovale had a stroke at time of presentation. Two patients, one with PFE on the RA wall and another patient with PFE at the tricuspid valve, had pulmonary embolism at the time of presentation. Median maximal length for PFE varied by location, ranging from a media of 8 mm to 16 mm. Of the 12 patients with follow up echocardiogram 1 year after PFE removal; 3/12 (25%) had documented PFE recurrence. ConclusionR-PFE can be present in patients thromboembolic events when there is a right-to-left shunt. They can be a rare cause of pulmonary embolism, and at least in those that had follow-up echocardiograms, had a significant recurrence rate.

Abstract 10462: Increased Bone Morphogenetic Protein 10 Activity is Associated with Increased Right Atrial Wall Stress and Disease Severity in Pulmonary Hypertension

Background: Pulmonary Hypertension (PH) is characterized by increased right atrial (RA) stretch and pressure. The major predisposing risk factor for PH involves mutations in bone morphogenetic protein (BMP) receptor 2 (BMPR2), for which BMP9 and BMP10 are ligands. In adults, BMP10 is produced by RA cardiomyocytes, however, the mechanism to BMP10 release is unknown. We hypothesize that RA wall stress may be a trigger for BMP10 secretion. Methods: We determined BMP10 and BMP9 levels in plasma samples from PH-patients (22 idiopathic pulmonary arterial hypertension (iPAH), 14 hereditary PAH (hPAH) and 11 chronic thromboembolic PH (CTEPH)) and 16 controls by ELISA. To study BMP10 and BMP9 activity, we exposed endothelial cells to 10% serum and analyzed BMP-activity as read out of the BRE-luciferase reporter assay. Serum was incubated with trap antibodies: anti-BMP9 to inhibit BMP9 ligand, and ALK1-Fc to inhibit both BMP9 and BMP10 ligands. BMP9 and BMP10 activity were deducted from the difference vs baseline and BMP9-activity, respectively. Results: Circulating BMP10 levels were higher in PH-patients: 16.5 [9.5-69.7] pg/mL in iPAH, 17.1 [1.4-113.4] pg/mL in hPAH and 37.8 [10.7-87.1] pg/mL in CTEPH, vs 6.1 [0-8.7] pg/mL in controls (A). No differences were observed in BMP9 levels (B). BMP10 and BMP9 activity appeared lower in iPAH, only a trend was seen in BMP9-activity in iPAH vs hPAH (C,D). Next, we divided the PH cohort on median BMP10-activity. Higher active BMP10 in PH was associated with an increase in RA volume and pressure, and reduced RA compliance (E). Further, higher BMP10-activity in PH-patients was associated with worse disease status, shown by worse right ventricular function, lower stroke volume and increased NTproBNP (F). Conclusions: BMP10 circulating levels were increased in PH, whereas no difference in circulating BMP10-activity was observed. High BMP10-activity was associated with increased RA wall stress and disease severity in PH-patients.

P1006Conduction disorders in patients with congenital heart disease and right atrial volume overload: an intraoperative epicardial mapping study

Abstract Background Various atrial regions may contribute to the arrhythmogenic substrate for atrial tachyarrhythmias, including atrial fibrillation (AF), in patients with right atrial (RA) volume overload in congenital heart disease (CHD). It is widely recognized that structural and electrical remodelling of the RA occurs, but a previous endovascular mapping study showed that the left atrium (LA) was also affected in patients with atrial septal defect (ASD). The role of Bachmann's bundle (BB) and posterior left atrium (PLA) is yet unknown. Purpose To quantify and compare prevalence and severity of conduction disorders during sinus rhythm between atrial regions in patients with CHD and RA volume overload, using intraoperative high-resolution epicardial mapping. Methods Thirty-one patients (female: n=18, age: 48.5±13.8 years, history of AF: n=5) undergoing cardiac surgery for secundum ASD (n=18), sinus venosus defect (n=11) or isolated partial abnormal pulmonary venous return (n=2) were included. Intra-operative epicardial mapping (N=128/192 electrodes, interelectrode distance: 2mm) of the RA, BB, LA and PLA was performed during sinus rhythm. Conduction delay (CD) and block (CB) were quantified per region as proportion (%), length of lines (mm) and maximum conduction time (Δ local activation time between two adjacent electrodes). Results Proportion of CD on BB was 3.9% (2.3–4.9), RA 3.1% (1.9–3.8), PLA 2.4% (1.2–3.6) and LA 2.3% (1–3) and was higher on BB compared to PLA (p=0.002) and LA (p&lt;0.001) but not RA (p=0.063). Proportion of CB on BB was 2.1% (1.2–5.4), RA 2.2% (1.1–3.4), PLA 0.8% (0.1–2.4) and LA 0.8% (0.3–1.6) and was smaller on LA compared to BB (p=0.001) and RA (p=0.004). There were no significant differences in length of CD/CB lines between regions, except that length of the longest CB line per patient was longer in the RA compared to LA (p=0.008). Maximum conduction time was highest in the RA (median 40ms) as opposed to BB (31ms), LA (21ms) and PLA (18ms; all p&lt;0.0083 with Bonferroni correction), suggesting conduction disorders were more severe in the RA. For sub analysis, the RA surface was divided into 1) the crista terminalis region and 2) the lateral RA wall. In the crista terminalis region, proportions of CD and CB were higher, CD/CB lines were longer and maximum conduction times were higher (all p&lt;0.05). Differences between patients with and without AF were solely observed on BB: patients with AF had a higher proportion and longer lines of CB (p&lt;0.05), though outcomes should be interpreted with caution due to the small number of patients with AF. Conclusions In adult patients with CHD and RA volume overload, both RA and BB were affected by conduction disorders. More specifically, conduction disorders in the RA were mainly concentrated in the crista terminalis region. These findings suggest that not only the RA but also BB may be involved in the arrhythmogenic substrate for atrial tachyarrhythmias in these patients. Acknowledgement/Funding Dutch Heart Foundation [no 2012T0046]; LSH-Impulse [no 40-43100-98-008]; CVON [no 914728] and VIDI [no 91717339] to N.M.S. de Groot.

Primary Cardiac Angiosarcoma with Spontaneous Ruptures of the Right Atrium and Right Coronary Artery

Primary tumors of the heart are rarely seen. Cardiac angiosarcomas are malignant tumors that almost always have a poor prognosis. Atrium rupture and coronary artery fistula are very rare complications of primary cardiac angiosarcoma. We describe a 57-year-old man suffering from primary cardiac angiosarcoma with spontaneous ruptures of the right atrium and right coronary artery (RCA). Theoretically, either of these ruptures invariably results in pericardial effusion and tamponade that is rare but potentially life threatening. In this instance, however, the patient might have developed fibrous adhesions resulted from previous bloody pericardial effusion. A massive pericardial effusion was localized, which consequently prevented cardiac tamponade and hemodynamic collapse. Echocardiography revealed the tumor progression leading to detectable infiltration of solid mass into the right atrial (RA) wall, which is close to RCA. And color Doppler displayed the flow into the pericardial cavity through a disrupted RA wall and perforated RCA. Echocardiography remains the primary method of choice for evaluation of cardiac masses.

Right atrial size and function assessed with three-dimensional and speckle-tracking echocardiography in 200 healthy volunteers

Right atrial (RA) size predicts the outcome in some pathological conditions but reference values for RA volumes and myocardial function remain to be defined. Thus, we used two-dimensional speckle-tracking echocardiography (2D-STE) and three-dimensional echocardiography (3DE) to define normative reference values of RA volumes and function. Two hundreds healthy volunteers (43 ± 15 years, range 18-75; 44% men) underwent two-dimensional echocardiography (2DE) to obtain RA volumes and longitudinal strain (LS) of RA wall using 2D-STE, and 3DE to measure maximal (Vmax), minimal, and preA volumes to calculate total, passive, and active emptying volumes (TotEV, PassEV, and ActEV) and emptying fractions (TotEF, PassEF, and ActEF). Three-dimensional echocardiography volumes (Vmax, 52 ± 15 mL vs. 41 ± 14 mL), EVs (TotEV, 33 ± 10 mL vs. 24 ± 9 mL), and EFs (TotEF, 63 ± 9 vs. 58 ± 9%) were larger than 2DE ones (all P < 0.0001). Indexed 3D volumes were significantly larger in men than in women. RA TotEF correlated with total LS (r = 0.24, P = 0.025) and PassEF with positive LS (LSpos; r = 0.34, P < 0.0001). Ageing was associated with a decrease in passive (LSpos, r = -041; PassEV, r = -0.26; PassEF, r = -0.38; all P < 0.0001) and an increase in active RA function (negative LS, r = 0.34; ActEV, r = 0.25; all P < 0.0001; and ActEF, r = 0.15; P = 0.035) in order to maintain TotEV (r = -0.14, P = 0.05). Our study provides normative values for RA volumes and function measured by 3DE and 2D-STE in a relatively large cohort of healthy subjects with a wide age range. These data will help clinicians to identify RA remodelling and dysfunction.

Effects of right low atrial septal vs. right atrial appendage pacing on atrial mechanical function and dyssynchrony in patients with sinus node dysfunction and paroxysmal atrial fibrillation

To study the effects of right low atrial septum (AS) and right atrial appendage (RAA) pacing on atrial mechanical function and dyssynchrony in patients with sinus node disease (SND) and paroxysmal atrial fibrillation (AF). Detailed echocardiographic examination was performed on 30 patients with SND and paroxysmal AF and a dual-chamber, dual sensing, dual response pacemaker with atrial lead implantation at AS(n= 15) or RAA(n= 15). Peak atrial velocities were recorded by pulsed tissue Doppler spectrum. The timing of atrial contractions (Ta) was measured at the middle of the left atrial (LA) and right atrial (RA) free wall. Intra-[standard deviation (SD) of time of Ta (Ta-SD)] and inter-atrial delay(Ta-RL) was measured as the SD of time interval among LA six segments and time difference between the LA and RA wall, respectively. The baseline clinical statuses were similar between groups. Indexes of LA function, and intra- or inter-atrial dyssynchrony were also similar during intrinsic sinus rhythm in both groups (all P> 0.05). During atrial pacing, LA ejection fraction (52 ± 16 vs. 39 ± 14%, P= 0.029) and LA active emptying fraction (34 ± 7 vs. 23 ± 15%, P= 0.012) were higher in patients with AS than RAA pacing. Atrial velocity was also higher at the RA free wall (14.3 ± 3.1 vs. 10.3 ± 4.4 cm/s, P= 0.009), LA septal (7.5 ± 2.1 vs. 5.2 ± 1.7 cm/s, P= 0.004) and lateral wall (8.6 ± 2.4 vs. 6.3 ± 3.0 cm/s, P= 0.024) during AS compared with RAA pacing. There was no difference in Ts-SD during atrial pacing, nevertheless Ta-RL was significantly prolonged in patients with RAA compared with those with AS pacing (42 ± 36 vs. 27 ± 25 ms, P= 0.011). In patients with SND and paroxysmal AF, right low AS pacing significantly improved global and regional atrial mechanical function and synchronized inter-atrial electromechanical contraction compared with RAA pacing.

Effects of Cardiac Glycosides on Atrial Contractile Dysfunction After Short-term Atrial Fibrillation

Despite a long history of use in the treatment of paroxysmal atrial fibrillation (AF), the efficacy of cardiac glycosides has not been established. If such drugs are beneficial in this condition, the general view is that the benefit must be related to their inotropic actions. To assess the effects of the rapid-acting cardiac glycoside, acetylstrophanthidin (AS), on AF and AF-induced right atrial (RA) "stunning," RA wall motion (with ultrasonic crystals), RA pressure, and peak first derivative of pressure (dp/dt) (with microtip transducers) were measured before and after 5 min of high-intensity rapid atrial stimulation (10 Hz; 10 mA; 1 ms) and after the cessation of poststimulation AF. Measurements were made in neurally intact and autonomically blockaded dogs both before and after the administration of AS (0.01 mg/kg IV bolus and 0.015 mg/kg/h IV infusion). AS prevented the post-AF reduction in RA peak dp/dt under neurally intact and autonomically blockaded conditions, and it prevented the post-AF increase in the RA end-systolic dimension and the decrease in the percentage of RA systolic shortening with autonomic blockade. AS was beneficial whether or not baseline inotropy was enhanced by AS. The duration of AF following atrial stimulation was the same before and after AS, but when compared to controls, AS treatment appeared to prolong AF. Cardiac glycosides exert a favorable effect on AF-induced RA stunning, but this action is unrelated to its effects on the duration of AF.

Implantable atrial defibrillator with a single-pass dual-electrode lead

OBJECTIVESWe examined the feasibility and efficacy of using a single-pass, dual-electrode (Solo) lead for atrial fibrillation (AF) detection and defibrillation.BACKGROUNDThe efficacy and safety of an implantable atrial defibrillator (IAD) has been extensively studied; however, separate right atrial (RA) and coronary sinus (CS) defibrillation leads are used for the present system.METHODSWe studied the use of the Solo lead for AF detection and defibrillation in 17 patients who underwent cardioversion of chronic AF. The Solo lead with a proximal 6-cm RA electrode and a distal 6-cm spiral-shaped CS electrode were positioned into the CS with the RA electrode against the anterolateral RA wall. The RA-CS electrogram signal amplitudes were measured and the efficacy of the Solo lead for AF detection and defibrillation was assessed by using an external version of the IAD.RESULTSThe leads were inserted in all patients without complication (mean fluoroscopy time: 13.3 ± 6.8 min). The mean RA-CS signal amplitude was 484 ± 229 μV during sinus rhythm and 274 ± 88 μV during AF (p < 0.05). All patients had satisfactory atrial signal amplitude to allow accurate detection of sinus rhythm. Successful cardioversion was achieved in 16/17 (94%) patients with an atrial defibrillation threshold of 320 ± 70 V (5.5 ± 2.7 J). Insufficient interelectrode spacing resulted in suboptimal electrode locations, associated with a lower atrial signal amplitude, a higher atrial defibrillation threshold and diaphragmatic stimulation.CONCLUSIONSThese results suggest a simplified lead configuration with optimal interelectrode spacing can be used with an IAD for AF detection and defibrillation.

Internal Cardiac Cooling Improves Atrial Preservation: Electrophysiological and Biochemical Assessment

This study was designed to determine if the improved hypothermia that can be achieved with cold perfusion of the right atrium is associated with improved atrial preservation. During 120 minutes of cardioplegic arrest, 7 dogs with occlusive caval cannulation underwent right atrial (RA) perfusion with cold blood and 7 dogs with a single atriocaval cannula served as controls. RA perfusion produced a lower atrial septal temperature than atriocaval cannulation, 96% less electrical activity during arrest, and a lesser prolongation of the A-H interval after reperfusion (40% versus 123%; p > 0.01). At the end of arrest, compared with atriocaval cannulation, RA perfusion was associated with improved preservation of creatine phosphate (71 ± 10% versus 40 ± 7% of control; p > 0.05) and a lower level of lactate in the RA wall (8 ± 1 μmol/gm versus 15 ± 2 μmol/gm; p > 0.01). We conclude that improved hypothermia reduces electrical activity and anaerobic metabolism in the atrial myocardium during cardioplegic arrest and improves atrioventricular conduction following arrest.

A New Technique of Internal Cardiac Cooling Improves Atrial Protection

We developed a technique for selectively cooling the right heart during cardioplegic arrest by intracavitary right atrial (RA) perfusion with cold blood. In dogs during hypothermic cardioplegic arrest, we compared the effects on myocardial temperature of RA perfusion and two snared caval cannulas with three methods of venous cannulation without perfusion: a two-stage atriocaval cannula, two caval cannulas and two snared caval cannulas. The mean atrioventricular (AV) node temperature with RA perfusion (16.5° ± 0.4°C) was significantly lower than with the atriocaval cannula (25.1° ± 0.2°C), two caval cannulas (25.2° ± 0.3°C) or two snared caval cannulas (21.6° ± 0.2°C) ( p > 0.01, RA perfusion versus other groups). The results for RA wall temperature showed a similar pattern. RA perfusion produced similar results in 6 patients undergoing coronary artery bypass grafting. We conclude that hypothermic protection of the right atrium and AV node is inadequate with conventional techniques of cannulation and cooling, and may be improved by the use of internal RA cooling.

Subcostal M-mode echocardiography of the right atrial wall in the diagnosis of cardiac arrhythmias

The M-mode echocardiogram of the right atrial (RA) wall can be easily recorded in each person from the subcostal location. In a normal RA wall motion pattern, atrial contraction is represented by a markedly prominent posterior motion. The presence or absence of atrial contractions in the subcostal RA wall echocardiogram, their amplitude, and their timing may help in the diagnosis of cardiac arrhythmias with the simultaneously recorded nondiagnostic electrocardiogram. Flat and hidden P waves can be accurately identified throughout the cardiac cycle. It is possible to distinguish between atrial, ventricular, and nodal premature beats and to recognize atrial fibrillation, atrial flutter, paroxysmal atrial tachycardia, paroxysmal atrial tachycardia with block, atrioventrlcular (AV) nodal tachycardia, and supraventricular tachycardias with aberrant ventricular conduction. The diagnosis of wandering pacemaker, AV dissociation, sinoatrial block, and AV block is facilitated. On the basis of study of 60 patients with various rhythm disturbances, it was concluded that analysis of the subcostal RA wall echocardiogram is a new, helpful noninvasive approach in the diagnosis of cardiac arrhythmias.

The sinus node electrogram in patients with and without sick sinus syndrome: techniques and correlation between directly measured and indirectly estimated sinoatrial conduction time.

SUMMARY Sinus node electrograms (SNEs) were recorded in 44 patients using a standard quadripolar electrode catheter (USCI #6) with 10-mm interelectrode distance. In 23 patients, the catheter was positioned at the junction of the superior vena cava (SVC) and right atrial (RA) wall so that the concave curve of the catheter was facing the concave surface of the RA wall. The distal poles of the catheter were close to but not in direct contact with the RA endocardium underlying the anatomic location of the sinus node (method 1). In 21 patients, the catheter was looped in the RA and advanced to the junction of the SVC-RA wall so that the distal poles of the catheter were in direct contact with the RA endocardium underlying the area of the sinus node (method 2). Stable SNEs could be obtained in 10 of 23 patients (43%) by method 1 and in 18 of 21 (86%) by method 2. SNEs by both methods showed two negatively directed deflections (diastolic and upstroke slope of the sinus node) of low frequency and amplitude occurring after the deflections of the T and U waves but before the P wave and intraatrial electrograms from various atrial sites. Unlike method 1, atrial activation by method 2 was characterized by an atrial injury potential. SNEs by method 2 were more stable and less prone to baseline drifts. Carotid sinus massage performed in 10 patients resulted in prolongation of the onset of the upstroke slope to atrial activation. In one patient, it resulted in marked first-degree sinoatrial block. SNEs were recorded in one patient during and after a run of spontaneous atrial flutter. After termination of atrial flutter, sinoatrial conduction time (SACT) prolonged for the first postflutter sinus beat and normalized by the third sinus beat. Direct SACTwas assessed on the SNE in all 28 patients, 12 of whom had sick sinus syndrome (SSS). SACT was also estimated indirectly by continuous pacing in 28 patients and by premature stimulation in 20 patients. Direct SACT was significantly (p < 0.001) longer in patients with SSS (135 30 msec, mean SD) than in patients without SSS (87 12 msec).There was a good correlation between direct SACT and SACT by continuous pacing (r = 0.843, n = 28) and direct SACT and SACT by premature stimulation (r = 0.778, n = 18). However, in certain patients, there were appreciable differences and direct SACTwas longer than estimated SACT by continuous pacing or premature stimulation. We conclude that (1) the success rate of stable SNEs with no appreciable baseline drift is increased with direct contact of the catheter with atrial endocardium underlying the sinus node area (method 2); (2) carotid sinus massage results in depression of sinus node automaticity and prolongation of SACT; (3) direct SACT is significantly longer in patients with SSS and can separate most patients with from those without SSS; and (4) there is a good correlation between direct SACT and indirectly estimated SACT, although the latter underestimates the actual SACT.

Transposition of great vessels

Venous inflow stenoses either pulmonary or systemic represents a major complication after Mustard's operation. In order to eliminate such stenoses two modified methods of atrial in version have been developed using no or a minimum of foreign material. The indication for each method is different. Both methods have the incorporation of the remaining atrial septum and of a part of the left atrial wall into the new septum in common. The midportion is completed using a small Dacron patch in cases with fragile atrial tissue (method I) or a flap of the rightatrial wall in cases with normal tissue (method II). The incorporation of growing tissue into the new atrial septum minimizes the risk of secondary stenoses, due to shrinkage or excessive apposition of fibrous pannus.