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.

A counterpoint paper: Comments on the electrocardiographic part of the 2018 Fourth Universal Definition of Myocardial Infarction.

The Fourth Universal Definition of Myocardial Infarction (FUDMI) [published simultaneously in 2018 in numerous journals including Circulation, Journal of the American College of Cardiology and European Heart Journal] focuses mainly on the distinction between non-ischemic myocardial injury and myocardial infarction (MI), along with the role of cardiovascular magnetic resonance, in order to define the etiology of myocardial injury. As a consequence, there is less emphasis on updating the parts of the definition concerning the electrocardiographic (ECG) changes related to MI. Evidence of myocardial ischemia is a prerequisite for the diagnosis of MI and the ECG is the main available tool for i) detecting acute ischemia, ii) triage and iii) risk stratification upon presentation. This review focuses on multiple aspects of ECG interpretation that we firmly believe should be considered for incorporation in any future update to the Universal Definition of MI. Our counterpoint view is that: a) the use of the ECG following coronary artery bypass surgery should be better explored and defined; b) the emphasis in the FUDMI on convex versus concave ST-elevation, which is questionable, should be balanced by the fact that many patients with true ST-elevation MI (STEMI) present with a concave form of ST elevation; c) reciprocal ST-depression in STEMI caused by right coronary artery or left circumflex artery occlusion, should be set against the fact that not all anterior STEMIs present with reciprocal ST-depression which can also be seen in cardiomyopathy and left ventricular hypertrophy; d) the "posterior" leads V7-V9 should be placed on a horizontal line from V4, rather than follow the 5th intercostal space; e) ST-depression in V1-V3 is not a manifestation of ischemia of the basal inferior segment, placed horizontally; f) Interpreting ST-T changes in patients with conduction abnormalities and pacemakers should be further defined.

Bayés' syndrome: Time to consider early anticoagulation?

In the past few decades, extensive research has been conducted on atrial conduction disorders and their clinical relevance. An association between interatrial block (IAB) and supraventricular arrhythmias [most commonly atrial fibrillation (AF)] has been discovered and extensively investigated. We coined the term "Bayés Syndrome" to describe this association, and the medical community has accepted the eponym in recognition to the scientist who discovered most of the aspects associated with it. In this non-systematic review, we will focus on the association between IAB and AF, with special emphasis on the value of the surface 12-lead ECG as a valid tool to predict AF.

Reduced P-wave Voltage in Lead I is Associated with Development of Atrial Fibrillation in Patients with Coronary Artery Disease.

BACKGROUND: Reduced P-wave voltage in lead 1 (PVL1) has been associated with atrial fibrillation (AF) recurrence.This study sought to determine the association between reduced PVL1 and AF in the NSTEMI population and the correlation between reduced PVL1 and interatrial block (IAB)/coronary artery disease (CAD). METHODS: Data were recorded for clinical, echocardiographic, angiographic, electrocardiographic and outcome variables. Patients were followed for a minimum of one year. Chi-square tests, independent samples t-tests and one-way ANOVA were used for the analysis, which was done using IBM SPSSResults:: A total of 322 consecutive patients were included in the analysis. Patients with new-onset AF had a significantly lower PVL1 (0.085 ± 0.030mV vs. 0.103 ± 0.037mV; p=0.007). There was a significant difference in mean PVL1 between those with no IAB, partial IAB and advanced IAB (p = <0.001). Those with any type of IAB had a significantly lower mean PVL1 than those without (0.094 ± 0.032 mV vs. 0.106 ± 0.038 mV; p=0.005). Patients who developed AF had a significantly longer P-wave duration (126 ± 20ms vs. 119 ± 17ms; p=0.022). Patients with IAB were more likely to develop new-onset AF (15.4% versus 7.5%, p=0.025). There were significant co-linear associations between reduced PVL1 and IAB (p=0.005); reduced PVL1 and diffuse CAD (p=0.031) and IAB and diffuse CAD (p=0.022).

New methodologies for measuring Brugada ECG patterns cannot differentiate the ECG pattern of Brugada syndrome from Brugada phenocopy.

BACKGROUND: Brugada phenocopies (BrP) are clinical entities characterized by ECG patterns that are identical to true Brugada syndrome (BrS), but are elicited by various clinical circumstances. A recent study demonstrated that the patterns of BrP and BrS are indistinguishable under the naked eye, thereby validating the concept that the patterns are identical. OBJECTIVE: The aim of our study was to determine whether recently developed ECG criteria would allow for discrimination between type-2 BrS ECG pattern and type-2 BrP ECG pattern. METHODS: Ten ECGs from confirmed BrS (aborted sudden death, transformation into type 1 upon sodium channel blocking test and/or ventricular arrhythmias, positive genetics) cases and 9 ECGs from confirmed BrP were included in the study. Surface 12-lead ECGs were scanned, saved in JPEG format for blind measurement of two values: (i) ß-angle; and (ii) the base of the triangle. Cut-off values of ≥58° for the ß-angle and ≥4mm for the base of the triangle were used to determine the BrS ECG pattern. RESULTS: Mean values for the ß-angle in leads V1 and V2 were 66.7±25.5 and 55.4±28.1 for BrS and 54.1±26.5 and 43.1±16.1 for BrP respectively (p=NS). Mean values for the base of the triangle in V1 and V2 were 7.5±3.9 and 5.7±3.9 for BrS and 5.6±3.2 and 4.7±2.7 for BrP respectively (p=NS). The ß-angle had a sensitivity of 60%, specificity of 78% (LR+ 2.7, LR- 0.5). The base of the triangle had a sensitivity of 80%, specificity of 40% (LR+ 1.4, LR- 0.5). CONCLUSIONS: New ECG criteria presented relatively low sensitivity and specificity, positive and negative predictive values to discriminate between BrS and BrP ECG patterns, providing further evidence that the two patterns are identical.

Expert cardiologists cannot distinguish between Brugada phenocopy and Brugada syndrome electrocardiogram patterns.

AIMS: Brugada phenocopies (BrPs) are electrocardiogram (ECG) patterns that are identical to true Brugada syndrome (BrS) but are induced by various clinical conditions. The concept that both ECG patterns are visually identical has not been formally demonstrated. The aim of our study was to determine if experts on BrS were able to accurately distinguish between the BrS and BrP ECG patterns. METHODS AND RESULTS: Six ECGs from confirmed cases of BrS and six ECGs from previously published cases of BrP were included in the study. Surface 12-lead ECGs were scanned, saved in JPEG format, and sent to 10 international experts on BrS for evaluation (no clinical history provided). Evaluators were asked to label each case as a Brugada ECG pattern or non-Brugada ECG pattern by visual interpretation alone. The overall accuracy was 53 ± 33% for all cases. Within the BrS cases, the mean accuracy was 63 ± 34% and within the BrP cases, the mean accuracy was 43 ± 33%. Intra-observer repeatability was moderate (κ = 0.56) and inter-observer agreement was fair (κ = 0.36) while evaluator accuracy vs. the true diagnosis was only marginally better than chance (κ = 0.05). Similarly, diagnostic operating characteristics were poor (sensitivity 62%, specificity 43%, +LR 1.1, -LR 0.9). CONCLUSION: Our results provide strong evidence that BrP and BrS ECG patterns are visually identical and indistinguishable. These findings support the use of systematic diagnostic criteria for differentiating BrP vs. BrS as an erroneous diagnosis may have a negative impact on patient morbidity and mortality.

Reduced Irregularity of Ventricular Response During Atrial Fibrillation and Long-term Outcome in Patients With Heart Failure.

Reduced heart rate variability (HRV) is associated with poor outcome in patients with heart failure (HF). However, the data on predictive value of RR variability during atrial fibrillation (AF) are limited. Therefore, the aim of this study was to evaluate the association between ventricular response characteristics and long-term clinical outcome in the population of ambulatory patients with mild-to-moderate HF and AF at baseline. The study included 155 patients (mean age 69 ± 10 years) with AF at 20-minute Holter electrocardiographic (ECG) recordings at enrollment. HRV analysis included SDNN, rMSSD, and pNN50, whereas irregularity indexes included 2 nonlinear parameters: approximate entropy (ApEn) and Shannon entropy. After median 41 months of follow-up, 54 patients died, including 21 HF related and 16 sudden deaths. Patients with ApEn ≤1.68 (lower tertile) had 40% mortality versus 12% in others (p <0.001) at 2 years of follow-up. Only nonlinear HRV parameters (irregularity but not variability indexes) identified patients at higher risk during follow-up. Decreased ApEn ≤1.68 was an independent predictor of total mortality (hazard ratio [HR] 2.81, 95% confidence interval [CI] 1.61 to 4.89, p <0.001), sudden cardiac death (HR 3.83, 95% CI 1.31 to 11.25, p = 0.014), and HF death (HR 3.45, 95% CI 1.42 to 8.38, p = 0.006) in a multivariate Cox analysis. In conclusion, in a post hoc analysis of Muerte Subita en Insufficiencia Cardiaca study AF cohort, reduced irregularity of RR intervals during AF, likely caused by autonomic dysfunction, was an independent predictor of all-cause mortality and sudden death and HF progression in patients with mild-to-moderate HF, whereas traditional HRV indexes did not predict outcome.

Second-degree interatrial block in hemodialysis patients.

Interatrial conduction delays manifest as a prolonged P-wave duration on surface ECG and the term interatrial block (IAB) has been coined. They are usually fixed, but cases of intermittent IAB have been described, suggesting functional conduction block at the Bachmann bundle region. We report 2 cases of patients on chronic hemodialysis therapy presenting with intermittent IAB.

New-onset atrial fibrillation after cavotricuspid isthmus ablation: identification of advanced interatrial block is key.

AIMS: A significant proportion of patients develop atrial fibrillation (AF) following cavotricuspid isthmus (CTI) ablation for typical atrial flutter (AFl). The objective of this study was to assess whether the presence of advanced interatrial block (aIAB) was associated with an elevated risk of AF after CTI ablation in patients with typical AFl and no prior history of AF. METHODS AND RESULTS: This study included patients with typical AFl and no prior history of AF that were referred for CTI ablation. Patients were excluded when they had received repeat ablations or did not demonstrate a bidirectional block. In all patients, a post-ablation electrocardiogram (ECG) in sinus rhythm was evaluated for the presence of aIAB, defined as a P-wave duration ≥120 ms and biphasic morphology in the inferior leads. New-onset AF was identified from 12-lead ECGs, Holter monitoring, and device interrogations. The cohort comprised 187 patients (age 67 ± 10.7 years; ejection fraction 55.8 ± 11.2%). Advanced interatrial block was detected in 18.2% of patients, and left atrium was larger in patients with aIAB compared with those without aIAB (46.2 ± 5.9 vs. 43.1 ± 6.0 mm; P = 0.01). Over a median follow-up of 24.2 months, 67 patients (35.8%) developed new-onset AF. The incidence of new-onset AF was greater in patients with aIAB compared with those without aIAB (64.7 vs. 29.4%; P < 0.001). After a comprehensive multivariate analysis, aIAB emerged as the strongest predictor of new-onset AF [odds ratio (OR) 4.2, 95% confidence interval (CI): 1.9-9.3; P < 0.001]. CONCLUSION: Advanced interatrial block is a key predictor for high risk of new-onset AF after a successful CTI ablation in patients with typical AFl.