First‐Degree AV Block—An Entirely Benign Finding or a Potentially Curable Cause of Cardiac Disease?

First‐degree atrioventricular (AV) block is a delay within the AV conduction system and is defined as a prolongation of the PR interval beyond the upper limit of what is considered normal (generally 0.20 s). Up until recently, first‐degree AV block was considered an entirely benign condition. In fact, some complain that it is a misnomer since there is only delay and no actual block in the AV conduction system (usually within the AV node). However, it has long been acknowledged that extreme forms of first‐degree AV block (typically a PR interval exceeding 0.30 s) can cause symptoms due to inadequate timing of atrial and ventricular contractions, similar to the so‐called pacemaker syndrome. Consequently, the current guidelines state that permanent pacemaker implantation is reasonable for first‐degree AV block with symptoms similar to those of pacemaker syndrome or with hemodynamic compromise, but also stresses that there is little evidence to suggest that pacemakers improve survival in patients with isolated first‐degree AV block. Recent reports suggest that it may be time to revisit the impact of first‐degree AV block. Also, several findings in post hoc analyses of randomized device trials give important insights in possible treatment options. The present review aims to provide an update on the current knowledge concerning the impact of first‐degree AV block and also to address the issue of pacing in patients with this condition.     

When Ventricular Safety Standby Does Not Work

Dual chamber pacemakers have inbuilt advanced safety systems such as ventricular safety standby (crosstalk detection) to prevent ventricular oversensing resulting in inappropriate pacing inhibition. We describe a case where this safety mechanism does not reliably work and the management required to rectify the situation in an educational format.     

EKG Pattern of Brugada Syndrome and Sudden Infant Death Syndrome—Is It Time to Review the Diagnostic Criteria? Case Report and Review of Literature

Brugada Syndrome (BrS) is a cardiac disorder characterized by incomplete right bundle‐branch block and ST elevations in the anterior precordial leads especially V₁–V₃, associated with an increased risk for sudden cardiac death (SCD) in young adults. Our case describes a patient with family history of sudden infant death syndrome (SIDS) who presented with a Brugada pattern unmasked by severe hyperkalemia and diabetic ketoacidosis. Several studies have concluded there may be a genetic link among SIDS, SDC, and BrS resulting from mutations in cardiac ion channel‐related genes. Recognizing SIDS as part of the diagnostic criteria for BrS would help us identifying a significant number of families susceptible to develop SCD (as well as SIDS).     

Reduction in Atrial Flutter Ablation Time by Targeting Maximum Voltage: Results of a Prospective Randomized Clinical Trial

Background: Radiofrequency ablation (RFA) of the cavotricuspid isthmus (CTI) is an established therapy for typical atrial flutter. Previous studies have demonstrated that the CTI is often composed of discrete muscle bundles, and evidence has suggested that these bundles correlate with high-voltage local electrograms in the tricuspid isthmus. This randomized, multicenter clinical trial was designed to prospectively compare the hypothesis that a maximum voltage-guided (MVG) technique targets critical conducting bundles in the isthmus, as reflected by a reduction in ablation requirements compared to the anatomical approach to atrial flutter ablation.
Methods: Bidirectional block was achieved in patients undergoing ablation for typical atrial flutter using 1 of 2 randomly assigned methods. The anatomical approach produced a contiguous line of ablation lesions from the inferior aspect of the tricuspid annulus to the inferior vena cava using a standard method. The MVG technique sequentially targeted the maximum voltage local electrograms in the CTI along a similar line.
Results: Sixty-nine patients were randomized, with mean age 63 ± 10 and 58 (84%) male. Among patients in the anatomic group (n = 34), mean ablation time was 11.2 ± 7.5 minutes compared to 5.9 ± 3.3 in the MVG group (n = 35) (P = 0.0026). A mean of 14.2 ± 9.7 ablation lesions were created in the anatomic group, and 7.9 ± 4.8 in the MVG group (P = 0.0042).
Conclusions: Ablation for atrial flutter using an MVG technique results in significantly less ablation requirements than the traditional approach, potentially by concentrating ablation lesions on the muscle bundles responsible for transisthmus conduction.     

Chronic rate dependent exit block after pulmonary vein isolation

Rate dependent exit block across the pulmonary veins has been previously described immediately following catheter ablation. We report a case of rate dependent pulmonary vein exit block seen at repeat ablation 7 years after the index procedure. To our knowledge, this is the first report of chronic rate dependent exit block discovered years after circumferential pulmonary vein antral isolation.