Third-degree atrioventricular block from metastatic poorly differentiated sarcoma suggestive of osteosarcoma in a dog.

ABSTRACT: Type I and type II second-degree AV block characterize block of a single sinus P wave:Type I block describes visible, varying and generally decremental AV conduction and type II block describes apparent all-or-none conduction without visible changes in AV conduction time before and after the blocked impulse. Absence of sinus slowing is an important criterion of type II block because a vagal surge (generally benign) can superficially resemble type II block. The diagnosis of type II block cannot be established if the first postblock P wave is followed by a shortened PR interval or is not discernible. All correctly defined type II blocks are infranodal. A pattern resembling narrow QRS Type II block together with an obvious type I structure in the same recording effectively rules out type II block because the co-existence of both types of narrow-QRS block is rare. Narrow QRS type I block is almost always AV nodal whereas type I block with bundle branch block outside acute myocardial infarction is infranodal in 60-70 % of cases. 2:1 AV block cannot be classified in terms of type I or II blocks and can be nodal or infranodal. Pacing is indicated in symptomatic marked first-degree AV block (>0.30 sec.), but patients with systolic heart failure might benefit more with biventricular pacing. Permanent pacing is almost never needed after inferior myocardial infarction and narrow QRS AV block. It should be considered only if second- or third-degree AV block persist for 14-16 days. Patients with bundle branch block and transient secondand third-degree AV block during anterior myocardial infarction have a high risk of sudden death after hospital discharge usually from ventricular tachyarrhythmias rather than AV block. They should receive an implantable cardioverter- defibrillator rather than a stand-alone pacemaker in the setting of severely depressed systolic left ventricular function. There are many causes of atrioventricular (AV) block but progressive idiopathic fibrosis of the conduction system related to an aging process of the cardiac skeleton is the most common cause of chronic acquired AV block. Barring congenital AV block, Lyme disease is the commonest cause of reversible third-degree AV block in young individuals and it is usually AV nodal. Before implantation of a permanent pacemaker, reversible causes of AV block such as Lyme disease, hypervagotonia, athletic heart, sleep apnea, ischemia, and drug, metabolic, or electrolytic imbalance must be excluded. Table 1 outlines the format used in the 2002 American College of Cardiology/American Heart Association/ North American Society of Pacing and Electrophysiology (ACC/AHA/NASPE) guidelines for pacemaker implantation [1]. The indications for permanent pacing in second- or third- degree AV block unlikely to regress are often straightforward in symptomatic patients but they are more difficult in asymptomatic patients. Some of the ACC/AHA/NASPE guidelines appear somewhat dogmatic. The final responsibility rests with the physician in terms of decisions, and the guidelines only represent a basic framework to start from.

The study tests the hypothesis that ablating all inputs to the atrioventricular (AV) node can result in complete heart block with stable junctional escape rhythm. We attempted atrionodal input ablation in 76 consecutive patients with uncontrolled atrial fibrillation. Fast and slow pathways were first ablated. If there was no AV block, additional energy applications were done between fast and slow pathway locations. The patients were followed for 42 +/- 11 months. Group I (n = 57) comprised patients with complete heart block and junctional escape rhythm (53 +/- 4 beats/min) at the end of the procedure. The escape rhythm remained stable throughout follow-up. Group II (n = 15) were patients who failed the stepwise atrionodal input ablation and required AV junctional ablation guided by His bundle potential to achieve complete heart block. Four patients showed a slow escape rhythm after ablation (33 +/- 4 beats/min). Others had no escape rhythm. All 15 pts remained pacemaker dependent. The total death rate of groups I and II was 18/57 (31.6%) vs 10/15 (66.7%), respectively (p < 0.02). These differences could not be explained by a difference of left ventricular ejection fraction (0.42 +/- 0.07 vs 0.41 +/- 0.04, respectively, p = NS). (1) In most patients, ablation of both fast and slow pathways did not result in complete heart block, indicating the presence of multiple atrionodal inputs. (2) Ablation of all atrionodal inputs may result in complete heart block with stable junctional escape rhythm. (3) As compared with AV junctional ablation, atrionodal input ablation was associated with a lower mortality rate on long-term follow up.

Percutaneous solution for a frequent complication after transcatheter aortic valve replacement: A case of atrioventricular leadless pacemaker implantation after transcatheter aortic valve replacement

Narrow QRS mobitz type II second-degree atrioventricular block in acute myocardial infarction: True or false?

Background Diabetes mellitus (DM) is a risk factor for cardiovascular disease and sudden cardiac death. Increasing evidence shows that DM may be associated with electric disturbances including arrhythmias and atrioventricular block (AVB). However, the association of DM and AVB has never been confirmed in large studies. Purpose The present study aims to determine the association of DM and third-degree AVB. Method A nationwide nested case-control study of patients &amp;gt;40 years with third-degree AVB between 1995 and end of 2017, matched 1:2 on age and gender with controls from the Danish background population. DM was defined if patients were prescribed oral antidiabetics or insulin, or if they were diagnosed with an ICD10 code of DM type I or II. Data on medication, comorbidity, and outcomes were collected from Danish nationwide registries. Conditional logistic regression was used to estimate hazard ratio (HR) and 95% confidence intervals (95% CI) of third degree AVB. Results Out of a total population of 8,964,086, we located a total of 32,722 cases with third degree AVB, that were matched 1:2 with 65,422 controls, with a mean age of 75.3 years and 59.1% males. The case group had more DM 18,5% vs 13,3%, acute myocardial infarction 27,0% vs 16.0%, stroke 18.5% vs 16.2%, heart failure 20.0% vs 8.5% and chronic kidney disease 4.7% vs 2.5% compared to the control group. In multivariable analysis adjusted for comorbidities DM remained significantly associated with third degree AVB [HR 1.30 (95% CI: 1.25–1.35)] (Figure) Conclusion In this nationwide population study, DM was associated with a higher risk of third degree AVB compared to matched controls without DM. This suggests a low threshold for use of ECG evaluation in case of dizziness or syncope in DM patients, and further, that ECG should be a part of routine controls of DM patients. Risk of third degree AV block Funding Acknowledgement Type of funding source: None

Shortening of the atrial refractory period is the key feature of atrial electrical remodeling during atrial fibrillation (AF). During sinus rhythm (SR), assessment of the atrial refractoriness is hampered by the fact that the atrial repolarization wave (Ta wave) is largely obscured by the following QRST complex. The purpose of this study was to study the Ta wave in subjects with paroxysmal AF during SR with third-degree atrioventricular (AV) block, and in matched controls. Fifteen patients (mean age 70 +/- 10 years, five males) with paroxysmal AF undergoing AV-nodal ablation were studied. Fifteen age- and gender-matched subjects (mean age 71 +/- 9 years, five males) with third-degree AV block, without a history of heart disease, were used as controls. Standard 12-lead electrocardiograms (ECGs) were recorded and transformed to orthogonal leads and studied using P-wave signal averaging technique. The P to Ta interval was shorter (408 +/- 47 ms vs 451 +/- 53 ms, P = 0.017) and in Lead Y the Ta peak location was earlier (156 +/- 31 ms vs 187 +/- 34 ms, P = 0.002) in subjects with paroxysmal AF than in the controls. The P-wave duration (126 +/- 15 ms vs 129 +/- 17 ms, P = 0.59) and morphology was similar in AF patients and controls. In this study, the ECG signs of shorter atrial refractoriness associated with a history of AF are visualized for the first time during SR. The finding of the earlier location of the PTa peak in AF subjects implies that a possible indicator of increased arrhythmia susceptibility may be visible already in the unprocessed ECG.

Transvenous pacemaker placement in a dog with atrioventricular block and persistent left cranial vena cava

Diastolic mitral and tricuspid regurgitation by Doppler echocardiography in patients with atrioventricular block: New insight into the mechanism of atrioventricular valve closure

Late recovery of atrioventricular conduction after postsurgical chronic atrioventricular block is not exceptional

Atrioventricular (AV) blocks are of concern with the use of beta blockers in inferior wall myocardial infarction (MI). Ivabradine lowers heart rate with a lesser risk of AV blocks. To compare ivabradine with metoprolol in acute inferior wall MI in terms of feasibility, tolerability, and efficacy. It was a prospective double-blind single-center randomized controlled study. Of 1032 patients with acute inferior wall MI, 468 eligible patients were randomized in 1:1 manner to ivabradine (group A) and metoprolol (group B). Intention to treat analysis of 426 patients (group A-232 and group B-232) was performed. The primary endpoint was 30-day incidence of major adverse cardiovascular events including death, reinfarction, complete heart block (CHB), and heart failure. Secondary endpoints included 30days incidence of recurrent angina, readmission, first- or second-degree AV block, and tachyarrhythmias. Both the drugs decreased the mean heart rate to 62.22±2.95 (group A) vs 62.53±3.59 (group B) beats per minute (P=0.33). Ejection fraction improved in both the groups (5.15±1.93% in group A vs 5.52±2.18% in group B, P=0.065). The two groups did not differ significantly in their primary endpoints in terms of death (group A=1.72% vs group B=1.72%, OR=1.00, 95% CI=0.25-4.05, P=1.00), reinfarction (group A=0.86% vs group B=0.86%, OR=1.00, 95% CI=0.14-7.16, P=1.00), heart failure (group A=4.31% vs group B=2.59%, OR=1.70, 95% CI=0.61-4.75, P=0.31), or CHB (0% vs 2.59%, OR=0.07, 95% CI=0.00-1.34, P=0.08). There were no significant differences in the secondary endpoints of recurrent angina, readmission, and tachyarrhythmias except for more first- and second-degree AV blocks with metoprolol (12.93% vs 2.59%, OR=5.59, 95% CI=2.28-13.72, P=0.0002). Ivabradine is well tolerated and equally effective as metoprolol in acute inferior wall ST elevation myocardial infarction patients for lowering the heart rate with lesser risk of AV blocks.

Repeat accessory pathway ablation: Challenges, surprises, and lessons learned

Introduction Paediatric complete heart blocks are predominantly congenital with cases often diagnosed in utero, at birth or usually within the first 1 month of life. This is secondary to immune mediated injury of the conduction system due to transplacental passage of maternal anti-SSA/Ro-SSB/La antibodies. Childhood AV (atrioventricular) block is one which is diagnosed between 1 month and 18 years of age, which could be due to maternal antibodies, congenital heart defect, iatrogenic or due to underlying genetic causes. Idiopathic complete heart block of childhood is a rare entity with scarce case reports. Case Report We report a case of 13 month old previously fit boy diagnosed with idiopathic complete AV block. He was admitted at 13 months of age with an episode of febrile convulsion secondary to throat infection. He was noted to have a low heart rate of around 50 beats per minute. There was no family history of cardiac problems or need for pacemakers. An ECG (electrocardiogram) done showed evidence of complete heart block with QTc of 500 ms. He was otherwise hemodynamically stable with normal blood parameters. His echocardiography showed mild dilatation of both ventricles with overall good function & structurally normal arrangements. His blood tests showed normal thyroid function, kidney function, iron levels, vitamin D levels, creatine kinase levels and auto-antibody screen. The anti Ro-La antibodies were negative in both the child and his mother. The genetic screening for inherited causes of complete heart block was also negative. He remains stable with close monitoring by the cardiac team with no evidence of arrhythmia or current need for pacemaker at 2 years of age. He has a sibling who was also screened and investigations were normal. Discussion This case currently falls in the idiopathic AV block of childhood of which there are only scarce case reports worldwide. We currently do not know about the etiology or clinical course of these cases. Future genetic studies might reveal an underlying genetic cause in these cases. Further similar case reports and linear studies would help us to forecast clinical prognosis in these cases.

Background: Around 10% of patients need a permanent pacemaker due to conduction issues in heart post-valvular interventions. The transvenous pacemaker has many complications compared to novel Leadless pacemaker(LPM) implantation. Objective: The main aim of this review is to compare the outcomes between conventional transvenous pacemakers and leadless pacemaker implantation after valvular intervention. Method: We conducted a comprehensive search of PubMed and ScienceDirect databases for relevant studies published between 2019 and 2024 using the keywords- pacemaker implantation and valvular intervention. Studies available in full text and in English language were included. After removing duplicates using the Rayyan tool, the remaining studies were screened and selected based on predefined inclusion criteria. Eligible studies included retrospective analyses of patients aged over 40 years, with indications for leadless pacemaker implantation such as atrial fibrillation, sick sinus syndrome, complete heart block, or complications following pacemaker implantation. Patients who had previously undergone implantations were excluded. We performed a qualitative synthesis of data to note the comparisons. Result: A total of 9 studies were included, comprising 10,776 patients, of whom 1121 underwent LPM implantation and 9655 received conventional transvenous pacemakers. Indications for LPM following valvular interventions included atrial fibrillation(n=24), complete heart block(n=20), bradycardia(n=26), high-degree atrioventricular (AV) block(n=30), and left bundle branch block(n=9). For conventional transvenous pacemakers, complete heart block(n=24) and high-degree AV block(n=7) were the primary indications. Compared to LPM, patients with conventional pacemakers reported more complications like pocket formation, pericardial effusion, pneumothorax, and infections, along with increased hospital stay duration. A few patients with LPM suffered from device-related complications like device dislodgement and device thrombus formation. Conclusion: The above findings suggest that while both the devices showed some device related risks, LPMs presented with fewer overall adverse outcomes, and thus, may be a safer alternative than conventional pacemakers. There is insufficient data on the use of LPM after valvular interventions. Further studies are required to fully assess the risks and benefits of LPM and their usage in patients of conduction abnormalities after valvular interventions.

Aim: In this study, our aim was to determine clinical factors related to the recovery of the conduction system in patients presenting with atrioventricular (AV) block. Materials & methods: A total of 178 patients who were hospitalized at a tertiary center due to second- or third-degree AV block were retrospectively analyzed. Results: During hospital follow-up, 19.1% of patients had fully recovered from AV block. According to a logistic regression analysis; younger age (odds ratio [OR]: 0.950; 95%CI: 0.932-0.967; p<0.001), presenting with acute coronary syndrome(OR: 18.863; 95%CI: 3.776-94.222; p<0.001), β-blocker usage (OR: 12.081; 95%CI: 3.498-41.726; p<0.001), high serum creatinine levels (OR: 4.338; 95%CI: 2.110-8.918; p<0.001) and no calcification at the aortic valve (OR: 0.189; 95%CI: 0.050-0.679; p=0.011) were found to be related to resolution of AV block. Conclusion: It is crucial to know the reversible causes of AV block to prevent unnecessary permanent pacemaker implantation.

Reversible Complete Heart Block in a Pregnant Woman Related to Sertraline Treatment