Anatomical Variations in the Sinoatrial Nodal Artery: A Meta-Analysis and Clinical Considerations

Temporary sinus node dysfunction following ablation of atrial fibrillation in patients with aberrancy of the sinus node artery: a case series

OBJECTIVES

Our goal was to investigate sinus node dysfunction (SND) as a rare complication following surgical and catheter atrial fibrillation (AF) ablation in patients with an aberrant sinus node artery (SNA).

METHODS

We used a retrospective analysis of 3 patients with an aberrant SNA who underwent different AF ablation procedures: 1 concomitant to aortic valve replacement, 1 thoracoscopic hybrid AF ablation and 1 catheter AF ablation.

RESULTS

All patients experienced temporary SND perioperatively. In the first patient, sinus rhythm (SR) recovered by postoperative day 6. In the second patient, SR returned by postoperative day 14. The third patient had a sinus arrest during ablation that restored to SR immediately post-procedure. All patients had normal SR at the 3-month follow-up.

CONCLUSIONS

Awareness of SNA anatomy can help to prevent iatrogenic SND during AF ablation. If SND occurs, a wait-and-see approach is recommended, given that sinus node function seems to recover. Because SND recovers, the benefits of posterior wall isolation could outweigh the disadvantages of temporary SND.

Rare origin of the sinoatrial node artery: an anatomic report and a brief review of the literature

Several studies reported anatomical variations in the sinoatrial node artery (SANa). Here, we report a rare variation in the origin of the SANa on a human adult male cadaver. During dissection, we identified the SANa originating from a large atrial branch of the right coronary artery (RCA). This branch originates at the level of the inferior border of the heart and courses upwards. The initial part of this vessel is tortuous, and then it follows a straight path parallel to the RCA along the anterior surface of the right atrium. After this part, the artery curves posteriorly and to the left until it reaches the lower border of the right auricle, where it closely approaches the RCA. Finally, the artery runs posteriorly and to the right to follow a course along the medial wall of the right auricle and right atrium to reach a location close to the region of the junction of the superior vena cava and right atrium, where it follows its path buried in the myocardium. After perforating the myocardium, this vessel gives rise to branches that are distributed to both atria in addition to the SANa. The SANa runs to the sinoatrial node in a precaval (anterior to the superior vena cava) course. We also tried to characterize the vessels radiologically. The knowledge of the anatomical variations of the SANa is of the utmost importance for cardiologists and heart surgeons to better understand cardiac disease and accurately plan and execute cardiac interventions and surgical procedures.

Associations Between Coronary Artery Calcium Score and Exacerbation Risk in BLOCK-COPD

Introduction

In 2019, the Beta-Blockers for the Prevention of Acute Exacerbations of Chronic Obstructive Pulmonary Disease study (BLOCK-COPD) evaluated the effect of metoprolol on exacerbation risk and mortality in a COPD population without indications for beta-blocker use. We hypothesized that an imaging metric of coronary artery disease (CAD), the coronary artery calcium (CAC) score, would predict exacerbation risk and identify a differential response to metoprolol treatment.

Methods

The study population includes participants in the BLOCK-COPD study from multiple study sites. Participants underwent clinically indicated thoracic computed tomography (CT) scans ± 12 months from enrollment. The Weston scoring system quantified CAC. Adjusted Cox proportional hazards models evaluated for associations between CAC and time to exacerbation.

Results

Data is included for 109 participants. The mean CAC score was 5.1±3.7, and 92 participants (84%) had CAC scores greater than 0. Over a median (interquartile range) follow-up time of 350 (280 to 352) days, there were 61 mild exacerbations and 19 severe/very severe exacerbations. No associations were found between exacerbations of any severity and CAC>0 or total CAC. Associations were observed between total CAC and CAC>0 in the left circumflex (LCx) and time to exacerbation of any severity (adjusted hazard ratio [aHR]=1.39, confidence interval [CI]: 1.08-1.79, p=0.01) and (aHR=1.96, 95% CI: 1.04-3.70, p=0.04), respectively.

Conclusions

CAD is a prevalent comorbidity in COPD accounting for significant mortality. Our study confirms the high prevalence of CAD using the CAC score; however, we did not discover an association between CAC and exacerbation risk. We did find novel associations between CAC in the LCx and exacerbation risk which warrant further investigation in larger cohorts.

Incidence of and risk factors for pacemaker implantation after the modified Cryo-Maze procedure for atrial fibrillation

OBJECTIVES

The Maze procedure is a well-established treatment for atrial fibrillation. However, it is sometimes associated with bradycardia requiring pacemaker implantation. We assessed the rates of in-hospital and late-onset pacemaker implantation after the modified Cryo-Maze procedure and explored the risk factors for pacemaker implantation.

METHODS

This study enrolled a series of 751 patients who underwent the modified Cryo-Maze procedure at our institution between 2001 and 2020. Multivariable Fine-Gray regression was used to analyze the risk factors for late-onset pacemaker implantation.

RESULTS

Twelve patients (1.6%) underwent in-hospital pacemaker implantation, and 55 patients (7.3%) underwent late-onset pacemaker implantation during a median follow-up of 4.5 years (interquartile range, 1.4-10.0). The most common primary indication for pacemaker implantation was sick sinus syndrome (56 patients [7.5%]), followed by complete atrioventricular block (11 patients [1.5%]). The cumulative incidence of late-onset pacemaker implantation with death as a competing risk was 2.8% at 1 year, 7.7% at 5 years, and 10.8% at 10 years. Risk factors for late-onset pacemaker implantation included a longer preoperative atrial fibrillation duration (hazard ratio, 1.14; P < .001) and an older age (hazard ratio, 1.05; P = .001). The mortality, cumulative incidence of cerebrovascular accidents, and rate of atrial fibrillation recurrence were not significantly different between patients with and without pacemaker implantation.

CONCLUSIONS

Longer preoperative atrial fibrillation duration and older age are risk factors for late-onset pacemaker implantation after the modified Cryo-Maze procedure. However, the incidence of pacemaker implantation is not associated with increased morbidity or atrial fibrillation recurrence.

The right coronary artery in the heart of chinchilla (Chinchilla laniger Molina)

The pattern of normal coronary vascularization in a mammalian heart includes the presence of both right and left coronary arteries. According to the literature data, the presence of single major coronary arteries is mainly related to cardiac abnormalities. Previously it has been reported that the right coronary artery is absent in the coronary vascularization of the heart in the chinchilla. Our research was carried out on thirty chinchillas (Chinchilla laniger Molina). The coronary vessels were filled with colored latex to render them visible. The examinations were supplemented additionally with the use of microcomputed tomography with arterial contrast. Our study demonstrates its undoubtedly presence of the right coronary artery. In all subjects the right coronary artery was present, as was the left coronary artery. Two types of right coronary artery were found. Our results indicate that the normal pattern of coronary vascularization of heart in chinchilla includes both the right and left coronary arteries. An open question remains the presence of single coronary artery is a normal pattern of cardiac arterial vascularization in chinchilla.

The Critical Appraisal Tool for Anatomical Meta-analysis (CATAM): A framework for critically appraising anatomical meta-analyses

The hallmark of evidence-based medicine is the meta-analysis (MA). For much of its rich history, the field of anatomy has been dominated by descriptive, cadaveric studies. In the last two decades, quantitative measurements and statistical analyses have frequently accompanied such studies. These studies have directly led to the publication of anatomical MAs, which have ushered in the exciting field of evidence-based anatomy. Although critical appraisal tools exist for clinical MAs, none of them are specifically tailored for anatomical MAs. Therefore, the purpose of this paper is to provide a framework by which clinical anatomists and others can critically appraise anatomical MAs using the Critical Appraisal Tool for Anatomical Meta-analysis (CATAM). Using a running example from a recently published MA, we show how to use the CATAM rubric in a step-by-step fashion. Each scored section of the CATAM rubric is summated into a total score (maximum 50 points). This score is then referenced to a conversion chart, which assigns a qualitative value to the MA in a range from "very good" to "poor." Future studies can investigate the interrater reliability of the instrument, and possibly subject the CATAM rubric to a Delphi panel. As anatomical MAs become more commonplace at surgical grand rounds and journal clubs in academic medical centers throughout the world, we hope that the CATAM rubric can help facilitate meaningful discussions about the quality and clinical relevance of anatomical MAs. This article is protected by copyright. All rights reserved.

Rhythm disorders after isolated mitral valve surgery: Consideration of the variations of the sinoatrial nodal artery in choice of atriotomy

Background: This study aims to investigate the effect of atriotomy approaches applied in mitral valve surgery and variations of the sinoatrial nodal artery on postoperative arrhythmias and the need for a temporary or permanent pacemaker.

Methods: Data of 241 patients (108 males, 133 females, mean age: 53.7±12.3 years; range, 18 to 82 years) who underwent isolated mitral valve surgery with a median sternotomy between January 2009 and December 2019 were retrospectively analyzed. The patients were divided into three groups according to the surgical approach for mitral valve exploration as left atriotomy (n=47), transseptal (n=131), and superior transseptal (n=63). By scanning the hospital records, the origin of the sinoatrial nodal artery was determined in the coronary angiography images obtained before surgery. Postoperative rhythm changes were analyzed based on electrocardiography and telemetry recordings.

Results: Temporary pacing was required in 31 (49.2%) patients in the superior transseptal group, 40 (30.5%) patients in the transseptal group, and 12 (25.5%) patients in the left atriotomy group, indicating a statistically significantly higher rate in the superior transseptal group (p=0.013). Permanent pacemaker implantation was required in only one patient (superior transseptal), indicating no significant difference among the groups. The first-degree atrioventricular block was seen in 28 (44.4%) patients in the superior transseptal group, 42 (32.1%) patients in the transseptal group, and 13 (27.7%) patients in the left atriotomy group (p=0.130). The PR interval in the postoperative period was longer in the superior transseptal group than in the left atriotomy group in patients with the sinoatrial nodal artery originating from the right coronary artery (p=0.049). No significant difference was observed among the surgical approaches regarding the PR interval in patients with the sinoatrial nodal artery originating from the left circumflex coronary artery after surgery.

Conclusion: We believe that the choice of atriotomy in isolated mitral valve surgery and sinoatrial nodal artery variations do not affect permanent arrhythmia alone. Still, the superior transseptal approach causes the electrical conduction to slow down temporarily more than the left atriotomy and transseptal method.

The Organization of the Sinoatrial Node Microvasculature Varies Regionally to Match Local Myocyte Excitability

The cardiac cycle starts when an action potential is produced by pacemaking cells in the sinoatrial node. This cycle is repeated approximately 100 000 times in humans and 1 million times in mice per day, imposing a monumental metabolic demand on the heart, requiring efficient blood supply via the coronary vasculature to maintain cardiac function. Although the ventricular coronary circulation has been extensively studied, the relationship between vascularization and cellular pacemaking modalities in the sinoatrial node is poorly understood. Here, we tested the hypothesis that the organization of the sinoatrial node microvasculature varies regionally, reflecting local myocyte firing properties. We show that vessel densities are higher in the superior versus inferior sinoatrial node. Accordingly, sinoatrial node myocytes are closer to vessels in the superior versus inferior regions. Superior and inferior sinoatrial node myocytes produce stochastic subthreshold voltage fluctuations and action potentials. However, the intrinsic action potential firing rate of sinoatrial node myocytes is higher in the superior versus inferior node. Our data support a model in which the microvascular densities vary regionally within the sinoatrial node to match the electrical and Ca²⁺ dynamics of nearby myocytes, effectively determining the dominant pacemaking site within the node. In this model, the high vascular density in the superior sinoatrial node places myocytes with metabolically demanding, high-frequency action potentials near vessels. The lower vascularization and electrical activity of inferior sinoatrial node myocytes could limit these cells to function to support sinoatrial node periodicity with sporadic voltage fluctuations via a stochastic resonance mechanism.

A case of atrial septal defect associated with anomalous sinoatrial node artery in pulmonary atresia with intact ventricular septum

An 11‐year‐old boy affected by pulmonary atresia with intact ventricular septum (AP‐IVS) was listed for percutaneous pulmonary valvuloplasty and closure of multi‐fenestrated atrial septal defect (ASD). Intra‐procedural transesophageal echocardiography arose the suspect of abnormal coronary artery pattern while selective angiography documented a single sinoatrial node artery (SANa) with an unusual retro‐aortic course. As consequence, we proceeded to effectively close the defects with a not self‐centering device placed in the most central side hole. This case supports the hypothesis that sometimes arrhythmic complication during ASD closure procedures might be due to unrecognized injury of the SANa.

Conduction Disorders in the Setting of Acute STEMI

ST-elevation myocardial (STEMI) is frequently associated with conduction disorders. Regional myocardial ischemia or injury may affect the cardiac conduction system at various locations, and neural reflexes or changes in the balance of the autonomous nervous system may be involved. Sinoatrial and atrioventricular blocks are more frequent in inferior than anterior STEMI, while new left anterior fascicular block and right bundle branch block indicate proximal occlusion of the left anterior descending coronary artery. New left bundle branch block is associated with multi-vessel disease. Most conduction disorders associated with STEMI are reversible with reperfusion therapy, but they may still impair prognosis because they indicate a large area at risk, extensive myocardial infarction or severe coronary artery disease. Acute STEMI recognition is possible in patients with a fascicular or right bundle branch block, but future studies need to define the cut-off values for ST depression in the leads V1-V3 in inferolateral MI and for ST elevation in the same leads in anterior STEMI. In the left bundle branch block, concordant ST elevation is a specific sign of acute coronary artery occlusion, but the ECG feature has low sensitivity.

Sinoatrial nodal artery injury in thoracoscopic epicardial ablation for atrial fibrillation

OBJECTIVES

This study aimed to clarify the incidence of sinoatrial nodal artery (SANa) injury in thoracoscopic epicardial surgical ablation for atrial fibrillation (AF) and its impact on postoperative outcomes, which have not been previously elucidated.

METHODS

We enrolled 103 consecutively patients with AF who underwent thoracoscopic epicardial ablation at our institution. In these patients, we evaluated the postoperative incidence of SANa injury by using enhanced cardiac computed tomography. For patients with confirmed SANa injury, 3-day continuous electrocardiographic monitoring and exercise stress tests were performed to assess the sinus rhythm maintenance and sinus node function.

RESULTS

Thirteen patients (12.6%) had a confirmed SANa injury (left anterior type in 6 patients, left posterior type in 2 patients and double-branch type in 5 patients). After a median follow-up of 24 months, the patients with SANa injury were not found to be associated with lower sinus rhythm maintenance (hazard ratio 1.09, 95% confidential interval 0.36-3.31) as compared with those without SANa injury after adjustment for patient characteristics. Sinus node function was evaluated in 7 patients with SANa injury who remained in sinus rhythm after the procedure, and no sinus node dysfunction was confirmed in the 3-day electrocardiographic monitoring and exercise stress tests at a median follow-up of 12 months.

CONCLUSIONS

The prevalence of SANa injury in the patients who underwent thoracoscopic epicardial ablation for AF was relatively low, and the incidence of SANa injury was not associated with postoperative restoration of sinus rhythm and sinoatrial node dysfunction. More studies are required to better understand SANa injury.

Clinical course of sinus node dysfunction after thoracoscopic surgery for atrial fibrillation-analysis of the Atrial Fibrillation Ablation and Autonomic Modulation via Thoracoscopic Surgery (AFACT) study

PURPOSE

Sinus node dysfunction (SND) may complicate thoracoscopic surgical atrial fibrillation (AF) ablation. Identifying patients at risk is important, as SND may require temporary or permanent pacing. To determine the incidence of postoperative SND and duration of symptoms in patients who underwent thoracoscopic surgical ablation.

METHODS

Patients with paroxysmal or persistent AF included in the Atrial Fibrillation Ablation and Autonomic Modulation via Thoracoscopic Surgery (AFACT) study underwent pulmonary vein isolation and additional left atrial ablations on indication. Patients were randomized to ganglion plexus ablation or control. SND was defined as symptomatic or asymptomatic junctional rhythm exceeding sinus rate within 30 days postoperatively. The SND risk was assessed by using a univariable logistic regression model. The rate of pacemaker implantation was determined.

RESULTS

The AFACT study included 240 patients. SND developed in 17 (7.1%) patients, not affected by randomized treatment, p = 0.18. SND patients more often had persistent AF (88.2%) than patients without SND (57.4%), p = 0.01. After univariable testing, persistent AF (OR 5.57 CI 1.52-35.90, p = 0.02) and additional left atrial ablations (OR 12.10 CI 2.40-220.20, p = 0.02) were associated with postoperative SND. Six (35.3%) patients needed temporary pacing for 1-7 days; permanent pacemakers (PMs) were implanted for SND in five (29.4%) patients.

CONCLUSION

Additional left atrial ablations strongly increase the SND risk. The majority of SND was temporary, and sinus rhythm resolved within days, which indicates that a conservative approach with regard to pacemaker implantation should be considered.

A novel method with which to visualize the human sinuatrial node: Application for a better understanding of the gross anatomy of this part of the conduction system

For various clinical/surgical procedures, it is important to accurately understand the location of the sinuatrial node (SAN). Therefore, this study's goal was to develop a new and simple method to visualize the SAN in human hearts. A total of 16 formalin-fixed human hearts were used in the study. After the epicardium was removed, the fat tissue on the myocardium's surface was brushed and removed in a solution of 40°C water with a surfactant to show the SAN's location. Once the structure considered to be the SAN was observed, histological observation was conducted with Masson's trichrome staining to confirm its identity. The working myocardium, SAN branch of the coronary artery, and the structure believed to be the SAN were observed in all specimens. Histological analysis confirmed this structure to be the SAN. We believe that the method described herein might contribute to a better understanding of the SAN's morphologic features and serve as an improved teaching aide. Clin. Anat. 33:232-236, 2020. © 2019 Wiley Periodicals, Inc.

Permanent pacemaker insertion postmitral surgery: Do the atrial access and the origin of the sinoatrial node artery matter?

BACKGROUND AND AIM OF THE STUDY

To determine whether the type of atrial access to the mitral valve (left atriotomy, superior trans-septal, or limited trans-septal) influenced postoperative permanent pacemaker implantation and to investigate the effect of the sinoatrial (SA) node artery origin (right coronary or circumflex arteries) on the rate of pacemaker insertion.

METHODS

We retrospectively reviewed consecutive cases of patients who had mitral valve surgery at the Trent Cardiac Centre (2008-2016). The primary outcome was the incidence of permanent pacemaker insertion. The data were analyzed using univariate then binary multivariate regression analysis.

RESULT

Four hundred sixty nine patients had mitral valve surgery. The mean age was 66.5 ± 12.3 years and 47.5% were female. One hundred fifty patients (32%) had mitral valve surgery via the standard left atriotomy approach, while 226 (48.2%) and 93 (19.8%) cases were performed using the limited trans-septal and superior trans-septal approaches, respectively. Concomitant tricuspid valve surgery was carried out in 33 cases (7%). The overall rate of pacemaker implantation was 5.3%. On univariate analysis, only age (≥70 years old) and concomitant tricuspid valve surgery were significant predictors of postoperative pacemaker insertion, while on multivariate analysis only age (≥70 years old) remained as a predictor. The type of atrial incision and the origin of the SA node artery did not affect the rate of pacemaker implantation.

CONCLUSION

The type of atrial approach to the mitral valve and the origin of the SA node artery did not influence the incidence of postoperative permanent pacemaker insertion.