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Address reprint requests and correspondence: Dr Konstantinos N. Aronis, Section of Electrophysiology, Division of Cardiology, Heart and Vascular Institute, University of Pittsburgh Medical Center, 200 Lothrop St, South Tower E352.4, Pittsburgh, PA 15213.
Section of Electrophysiology, Division of Cardiology, Johns Hopkins Hospital, Johns Hopkins School of Medicine, Baltimore, MarylandSection of Electrophysiology, Heart and Vascular Institute, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania
Section of Electrophysiology, Division of Cardiology, Johns Hopkins Hospital, Johns Hopkins School of Medicine, Baltimore, MarylandArrhythmia Division, Inova Heart and Vascular Institute, Fairfax, Virginia
Section of Electrophysiology, Division of Cardiology, Johns Hopkins Hospital, Johns Hopkins School of Medicine, Baltimore, MarylandDivision of Pediatric Cardiology, Johns Hopkins Hospital, Johns Hopkins School of Medicine, Baltimore, Maryland
Atrial standstill is a rare clinical entity characterized by the absence of atrial electrical and mechanical activity and can occur in patients with extensive cardiac surgical history.
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In patients with suspicion of atrial standstill, electroanatomical mapping and echocardiography can be used at the time of pacemaker implantation to assess for the presence of any electrically functional atrial tissue.
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In patients with atrial standstill, even in the presence of islands of electrically functional atrial tissue, interatrial conduction block may result in the absence of atrial mechanical function and atrioventricular conduction.
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Left bundle pacing is feasible in patients with atrial standstill and bradycardia; it can result in improvement of cardiac output by correction of bradycardia without the potential deleterious effects of right ventricular apical pacing.
Introduction
Atrial standstill was first documented in a case report by Chavez and colleagues
in 1946, and constitutes a rare clinical condition defined by the absence of atrial electrical and mechanical activity. Atrial standstill is characterized by fibroelastosis and fatty infiltration in the atrium,
Right ventricular pacing has been traditionally the only method of pacing in patients presenting with symptomatic bradycardia in the setting of atrial standstill, but in limited case series, this commonly results in deterioration of ventricular function and poor outcomes.
In this case report, we present a patient with atrioventricular (AV) canal defect and an extensive cardiac surgical history who developed recurrent episodes of acute decompensated heart failure in the presence of junctional bradycardia with chronotropic incompetence. Our initial plans were to proceed with implantation of a dual-chamber pacemaker, but we had a high index of suspicion for the presence of atrial standstill in the setting of her extensive cardiac surgical history. Our aim in reporting these findings is 2-fold: (1) to demonstrate how electroanatomic mapping can be used intraoperatively to evaluate for the feasibility of atrial lead implantation in patients with atrial standstill; and (2) how left bundle branch (LBB) pacing may be a viable alternative for individuals with atrial standstill.
Case report
Patient history
Our patient is a 37-year-old woman who was born with incomplete AV canal defect (2 separate AV valves, no ventricular septal defect), with complete absence of the interatrial septum, cleft left AV valve, and a persistent left superior vena cava (SVC) anomalously connected to the left atrium. She did not have any heterotaxy or isomerism syndrome. The coexistence of complete absence of interatrial septum, persistent left SVC, and AV canal defect is an unusual constellation of defects but has been described in limited series.
She underwent primum atrial septal defect closure and rerouting of the left SVC to the right atrium at the age of 1 year. She had repeat atrial septal defect patch closure 1 year later. At the age of 20 years, she developed severe left AV valve regurgitation and underwent left AV valve cleft repair, annuloplasty, and surgical closure of a residual atrial septal defect. Two years later she developed atrial flutter and underwent ablation of typical cavotricuspid isthmus atrial flutter. At the age of 35 years, she developed left AV valve stenosis and atrial fibrillation, for which she underwent left AV valve replacement with a 25 mm bioprosthetic Mosaic valve (Medtronic, Minneapolis, MN) and biatrial maze procedure. Her postsurgical course was further complicated by development of constrictive pericarditis for which she underwent pericardial stripping 7 months after left AV valve replacement. Her medical history is also notable for morbid obesity (body mass index of 38 kg/m2), heart failure with preserved ejection fraction, asthma, chronic pain with opioid use disorder, and bipolar disorder. A year before her current presentation, she had recurrent episodes of acute decompensated heart failure that were attributed to medication nonadherence. Review of her electrocardiograms revealed episodes of sinus rhythm with marked first-degree AV conduction delay and junctional bradycardia.
At the age of 37 she was admitted to the cardiac intensive care unit of the Johns Hopkins Hospital with acute decompensated heart failure and hypotension requiring norepinephrine support. Her echocardiogram showed normal left ventricular (LV) size and function with an ejection fraction of 65%–70%, moderate pulmonary hypertension (estimated right ventricular systolic pressure of 54 mm Hg), and mild bioprosthetic left AV (mitral) valve stenosis with a mean gradient of 8 mm Hg and estimated left AV valve orifice of 1.5 cm2 by the pressure half-time method. Despite her normal LV ejection fraction, her stroke volume indexed to her body surface area was 38 mL/m2 and at a heart rate of 69 beats per minute (bpm) her cardiac index was 2.6 L/min/m2, which is borderline low. Her electrocardiogram (ECG) showed a junctional rhythm with rates between 50 and 60 bpm (Figure 1). She was not on any AV nodal blocking agents and thus her heart rate, in the setting of decompensated heart failure, was thought to represent chronotropic incompetence. No evidence of atrial activity or idioventricular escape rhythm was noted for the period that the patient was on electrocardiographic monitoring. She was diuresed using intravenous furosemide and norepinephrine was weaned off 24 hours after her admission. A right heart catheterization was performed when patient was felt to be clinically euvolemic and showed a pulmonary capillary wedge pressure of 19 mm Hg, cardiac index of 2.74 L/m/m2, systemic vascular resistance index of 1821 dyn/s/cm-5/m2, and pulmonary vascular resistance index of 643 dyn/s/cm-5/m2. In view of her recurrent hospitalizations for acute decompensated heart failure in the setting of borderline cardiac indices and junctional rhythm/bradycardia with chronotropic incompetence, a multidisciplinary meeting between adult congenital heart disease teams (A.C.), pediatric cardiology/electrophysiology (C.U.), and adult electrophysiology (K.A., A.B.) was held. The prevailing hypothesis was that her junctional rhythm and chronotropic incompetence contributed to her recurrent episodes of acute decompensated heart failure.
Figure 1Patient’s electrocardiogram upon her admission. Junctional bradycardia at a rate of 60 beats/min. Incomplete right bundle branch block with left axis deviation and poor precordial R-wave progression suggesting left anterior fascicular block.
A decision was made to proceed with implantation of a dual-chamber pacemaker with physiologic pacing. The patient was anticipated to have a very high percentage of ventricular pacing, given the previously documented significant prolongation of the PR interval, and thus the rationale behind pursuing physiologic pacing was the desire to avoid right ventricular apical pacing that has the potential to result in a decline in LV systolic function and worsen heart failure. Furthermore, given the extensive surgical and ablation history involving the patient’s atria, it was anticipated that her right atrium would be severely fibrosed and intra-atrial conduction block might be present. Periprocedural electroanatomic mapping was therefore arranged to guide placement of the right atrial lead.
Electroanatomic mapping of the right atrium and implantation of permanent pacemaker at the left bundle branch procedure
The patient was brought to the electrophysiology laboratory and 2 venous vascular sheaths (8.5F SR-0 and 9) were inserted in the right femoral vein. Next, a multielectrode electrophysiology mapping catheter (PentaRay; Biosense Webster, Irvine, CA) was advanced under fluoroscopic guidance to the right atrium via the SR-0 sheath. An intracardiac echocardiography catheter was advanced into the right atrium via the long 9F sheath and assisted with delineation of critical anatomic structures such as the interatrial septum, the tricuspid valve annulus, and the aortic valve cusps. Using an electroanatomic mapping system (CARTO; Biosense Webster), a detailed map of the right atrium extending up to the right and left SVC was made (Figure 2A). The entire right atrium was severely fibrosed. There were 3 isolated islands of surviving atrial tissue. The first was in the anterolateral right atrium / right atrial appendage; the second was located in the superior septal aspect of the right atrium, close to the junction with the left SVC; and the third was located distal in the left SVC, that likely constituted the posterior wall of the left atrium. Atrial rate was bradycardic in these islands. Pacing from all 3 locations confirmed local atrial capture by the electrograms of the adjacent PentaRay electrodes (Figure 2B). However, there was no evidence of global atrial capture (no P wave on surface ECG) and simultaneous transthoracic echocardiogram performed by the pediatric cardiology team during atrial pacing demonstrated no mechanical atrial contraction during atrial pacing. Furthermore, the local atrial capture did not result in ventricular activation, likely owing to intra-atrial conduction block from the prior surgeries. Given the lack of atrial mechanical contraction in response to atrial pacing and the bradycardic native rate of the nonfibrotic atrial islands, a decision was made to abandon atrial lead placement and proceed with single-chamber physiologic pacing. A 5F multipurpose diagnostic angiography catheter was introduced from the SR 0 sheath into the right subclavian vein and contrast venography was performed, showing normal right-sided vein anatomy and patent veins. The sheaths were removed from the body and hemostasis was achieved with a figure-of-8 hemostatic suture.
Figure 2A: Electroanatomical mapping of the right atrium and superior vena cava. The left superior vena cava has been surgically connected to the right atrium. There were 3 “islands” of electrically active atrial myocardium: (a) at the anterolateral right atrium/right atrial appendage; (b) at the superior septal aspect of the right atrium, close to the junction with the left superior vena cava; and (c) distal in the left superior vena cava (likely constituting the posterior wall of the left atrium). B: Example of pacing from the multielectrode mapping catheter in location (a). There is local atrial capture, as demonstrated by the atrial electrograms in the neighboring electrodes. However, there is no global atrial capture, as demonstrated by the lack of P wave on electrocardiogram, lack of mechanical capture demonstrated by Doppler echocardiography (not shown), and lack of atrioventricular (AV) conduction owing to interatrial block. Local capture without global capture, mechanical atrial contraction, and AV conduction was demonstrated in all 3 locations, (a) through (c).
Following infiltration with 1% lidocaine, a right infraclavicular prepectoral pocket was created. Under direct fluoroscopic guidance, the axillary vein was entered once. A 9F sheath was inserted into the vein using the modified Seldinger technique. A deflectable sheath (SelectSite C304-His; Medtronic) was inserted over a guidewire to the right ventricular apex. Using orthogonal fluoroscopic views, this sheath was withdrawn back approximately to a distance one-third from the tricuspid valve plane and was rotated septally. A fixed-helix lumenless lead (3830; Medtronic) was then deployed in the septum. The initial pacing QRS morphology had the “W sign” on lead V1. The lead continued to be rotated, with periodic assessment of the QRS morphology during pacing and the pacing impedance, until there was a slight decrease in the pacing impedance. At the final lead position, the pacing QRS morphology had a qR morphology in V1 and time from pacing stimulus to peak R wave in lead V5 was 80 ms (Figure 3A).
Figure 3A: Patient’s electrocardiogram after implantation of the left bundle branch pacing lead. Ventricularly paced rhythm with narrow QRS complex, qR complex in lead V1, and lead aVR/aVL discordance. Time from pacing stimulus to peak of QRS complex in lead V5 is 80 ms. B: Anterior-posterior chest radiograph showing the final position of the left bundle branch pacing lead in the proximal interventricular septum.
Patients with AV canal defect usually have a posteriorly and inferiorly displaced AV node with a long nonbranching bundle and manifest with a leftward axis on the ECG, as noted in the patient’s junctional rhythm. Criteria for successful LBB capture have not been developed in this patient population. A pacing stimulus to peak R wave in the lateral precordial leads of <74 ms in patients without LBB disease and <80 ms in patients with LBB disease have 100% specificity for LBB capture. A pacing stimulus to peak R wave in the lateral precordial leads of <83 ms and <101 ms in patients without and with LBB disease have a balanced sensitivity and specificity for LBB capture, with areas under the receiver operating characteristic curve of 93.1% and 88.8%, respectively.
For this reason, it was felt that a pacing stimulus to peak R wave in V5 of 80 ms was consistent with LBB capture in this patient.
Intraoperative echocardiographic assessment showed that during junctional rhythm her stroke volume index was 43.8 mL/m2 and with a heart rate of 57 bpm corresponded to a cardiac index of 2.5 L/min/m2, when the patient was paced VVI at 75 bpm her stroke volume index remained 45.2 mL/m2 and her cardiac index increased to 3.4 L/min/m2. Stimulation and sensing thresholds were found to be satisfactory. The lead was then checked at 10 V output, and no diaphragm stimulation was noted. After the lead was placed into the connector, the generator was inserted into the pocket and the pocket was then closed in multiple layers of absorbable suture. The final lead parameters were impendence 532 ohms, R wave 7.3 mV, capture threshold 0.5 V at 0.4 ms. The device was programmed as VVIR 60–120 bpm. The patient was discharged home the following day (Figure 3B).
Patient follow-up
The patient has not had any additional admissions for acute decompensated heart failure in the 1 year following implantation of conduction system pacing. She had 1 admission 6 months after implantation for community-acquired pneumonia (treated with antibiotics) and a second admission 1 month later for COVID-19 pneumonia. Her baseline functional status is improved. Her lead parameters have been stable with capture 0.75 V @ 0.4 ms, sensing at 11.4 mV, and impedance of 418 ohms.
Discussion
Atrial standstill is a rare condition defined by the lack of atrial electrical activity and mechanical function, and it may be intermittent or permanent, partial or total, and congenital or acquired (myocardial disease or metabolic/toxic).
cardiac sarcoidosis, mitral valve stenosis, rheumatic heart disease, and muscular dystrophy. Histologically, atrial standstill is characterized by fibroelastosis and fatty infiltration in the atrium.
In limited studies it is suggested that the disease starts at the high lateral right atrium and progresses toward the lower right atrium to finally involve the tricuspid valve annulus.
In the case that we present here, atrial standstill was likely caused by her extensive prior cardiac surgery and biatrial maze procedure and likely contributed to recurrent admissions for acute decompensated heart failure.
Given the rarity of this condition, currently there are no guidelines or consensus statements to guide treatment of patients with atrial standstill. It is generally accepted that systemic oral anticoagulation is warranted to minimize the risk of thromboembolic complications. In cases of symptomatic bradycardia, implantation of a permanent pacemaker is indicated. In limited case reports of patients with partial atrial standstill, identification of a site that allows atrial capture and AV conduction has been helpful to guide atrial lead placement.
In these patients a dual-chamber pacemaker was implanted. However, given the potentially progressive nature of the disease, frequent evaluation of atrial capture and AV conduction is warranted. In the case that we present here, although our patient had some islands of electrically active myocardium, local capture of this myocardium did not result in AV conduction, owing to interatrial conduction block, and thus implantation of an atrial lead was not pursued.
Right ventricular pacing has been used in patients with atrial standstill and inability to place an atrial lead. However, in limited studies, right ventricular pacing in patients with atrial standstill has resulted in deterioration of ventricular function and poor outcomes.
Thus, physiologic LBB pacing has the potential to preserve LV systolic function in cases of adult congenital heart disease where the underlying anatomy precludes or complicates placement of a coronary sinus lead (eg, persistent left SVC). Single-chamber LBB pacing has been used in a case report of a 46-year-old man who presented with syncope from atrial standstill and bradycardia-induced torsades de pointes, in the setting of a giant right atrium.
In this case, the operators macroscopically mapped the right atrium during the permanent pacemaker implantation procedure and did not identify any viable atrial tissue. Prospective follow-up of the patient was not reported in the previous case report.
After implantation, our patient did not have any readmissions for acute decompensated heart failure, which represents a marked improvement of her heart failure status, considering that the year prior to the implant she had multiple admissions for acute decompensated heart failure. The most likely explanation for the improvement of her clinical status is the correction of chronotropic incompetence without a compromise in stroke volume or a decline in LV systolic function with LBB pacing. Her elevated filling pressures in the presence of a borderline cardiac output most likely represent diastolic dysfunction. There is always a fine balance when treating chronotropic incompetence in a patient with diastolic dysfunction, as faster rates can contribute to worsening of AV dyssynchrony. In our patient, there was no atrial mechanical contraction, so optimization of the AV synchrony was not an option. A baseline heart rate of 60 with default rate response settings was adequate to improve her clinical status, and no further adjustments of the rate response parameters have been required to date.
Last, this case report gives us the opportunity to review 2 important considerations relevant to device implantation in patients with corrected AV canal defects. First, to avoid penetrating trauma to the AV node with the sutures, the primum atrial septal defect is often corrected in such a way that the ostium of the coronary sinus is “excluded” on the left of the atrial septum. This renders the coronary sinus inaccessible and implantation of a coronary sinus lead impossible. It is thus critical to review the operative report before considering implantation of a lead in the coronary sinus. Second, although our patient did not have a ventricular septal defect, many patients with AV canal defects do have one. Usually, patients have the ventricular septal defect closed with a patch. The presence of a patch in the proximal interventricular septal area may pose additional technical difficulties in the implantation of an LBB pacing lead.
To summarize, we present a case report of LBB pacemaker implantation in a 37-year-old woman with atrial standstill, likely as a sequala to an extensive cardiac surgery history, and recurrent admissions for acute decompensated heart failure in the setting of junctional bradycardia. By implanting an LBB pacemaker and increasing her heart rate without introducing interventricular dyssynchrony, we were able to acutely improve her hemodynamics and cardiac output in the short term, as well as in long-term follow-up, with no additional admissions for acute heart failure decompensation following device placement.
References
Chavez I.
Brumlik J.
Sodi Pallares D.
About an extraordinary case of permanent atrial palsy with Keith and Flack node degeneration.
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