QT Interval Instability and Variability in Dogs with Hyperadrenocorticism

Hyperadrenocorticism is one of the most common endocrine diseases in dogs. In humans, it is clearly associated with a higher risk of cardiovascular events, but studies in dogs are scarce. To investigate the arrhythmogenic risk of dogs with hyperadrenocorticism, indices of variability and instability of the QT interval were studied in 38 dogs with hyperadrenocorticism and in 12 healthy dogs: variance (QTv), total instability (TI), short-term (STI) and long-term (LTI), and mean (QTm). Except for QTm, all parameters studied were higher in the hyperadrenocorticism group than in the control group. In addition, STI and QTv showed moderate positive correlation with left ventricle wall thickness. To a better understanding on the effect of the hypothalamus-pituitary-adrenal axis on ventricular repolarization, the hyperadrenocorticism group was subdivided according to the percentage of variation in plasma cortisol concentration (<30.1%; 30.1-60%; >60%) 8 hours after low-dose administration of dexamethasone. There was statistical difference in QTv, TI and LTI indices between the control group and the <30.1% and >60% groups, and in STI index between the control group and the >60% group. There was no statistical difference between sex groups in any of the electrocardiographic parameters studied. This result may indicate that the etiology of hyperadrenocorticism, and its consequent influence on hypothalamus-pituitary-adrenal axis could interfere on the heterogeneity of ventricular repolarization parameters in different ways, especially in the short-term stability; however further studies are necessary to understand the role of cortisol on electrical instability in dogs.

ECG Predictors for New-Onset Atrial Fibrillation Within a Year After Radiofrequency Ablation of Counterclockwise-Rotating Atrial Flutter

Background: New-onset atrial fibrillation (AF) after ablation of typical atrial flutter (AFL) is not rare. This study aimed to investigate the predictive value of electrocardiographic parameters on new-onset AF post-typical AFL ablation.Methods: A total of 158 consecutive patients (79.1% males, mean age 57.8 ± 14.3 years) with typical AFL were enrolled between January 2012 and August 2017 in this single-center study. Patients with a history of AF before ablation were excluded. ECGs during sinus rhythm (SR) and AFL were collected. The duration of the negative component of flutter wave in lead II (DFNII), proportion of the DFNII of the total circle length of AFL (DFNII%), amplitude of the negative component of flutter wave in lead II (AFNII), duration (DPNV1), and amplitude (APNV1) of negative component of the P wave in lead V1, and P wave duration in lead II (DPII) during sinus rhythm were measured.Results: During a median follow-up of 26.9 ± 11.8 months, 22 cases (13.9%) developed new-onset AF. DFNII was significantly longer in patients with new-onset AF compared to patients without AF (114.7 ± 29.6 ms vs. 82.7 ± 12.8 ms, p &lt; 0.0001). AFNII was significantly lower (0.118 ± 0.034 mV vs. 0.168 ± 0.051 mV, p &lt; 0.0001), DPII (144.21 ± 23.77 ms vs. 111.46 ± 14.19 ms, p &lt; 0.0001), and DPNV1 was significantly longer (81.07 ± 16.87 ms vs. 59.86 ± 14.42 ms, p &lt; 0.0001) in patients with new-onset AF. In the multivariate analysis, DFNII [odds ratio (OR), 1.428; 95% CI, 1.039–1.962; p = 0.028] and DPII (OR, 1.429; 95% CI, 1.046–1.953; p = 0.025) were found to be independently associated with new-onset AF after typical AFL ablation.Conclusion: Parameters representing left atrial activation time under both the SR and AFL were independently associated with new-onset AF post-typical AFL ablation and may be useful in risk prediction, which needs to be confirmed by further prospective studies.

CONNECTION BETWEEN THE PARAMETERS OF ECG SUPRAVENTRICULAR COMPONENT AND BRONCHIAL HYPERREACTIVITY IN CHILDREN WITH BRONCHIAL ASTHMA

Uncontrolled course of bronchial asthma (BA) is associated with the risk of heart rhythm disturbances. Objective of the study: to analyze the electrocardiographic parameters of the atrial complex and atrioventricular conduction and to assess their relationship with changes in spirometric parameters in tests with dosed physical activity (PA), reflecting bronchial hyperreactivity (BHR) in children with BA. Materials and methods of research: assessment of the parameters of the supraventricular component of the ECG in comparison with changes in spirometric parameters in tests with dosed PA was performed in 55 children aged 6–17 years with atopic asthma. To level the effect of age on ECG indices, the «relative PQ» (rPQ) index was introduced, calculated as the ratio of the patient's PQ interval duration to the median PQ values characteristic of a given age and gender. Results: it was found that a decrease in the Tiffno index (TI) in tests with PA is accompanied by a statistically significant increase in the rPQ index, an increase in the PQ segment (sPQ) and an increase in the proportion of the PQ interval in the structure of the R–R interval (PQ/RR); similar patterns were obtained when comparing the variability instantaneous volumetric expiratory flow rate at the level of 25% of the vital capacity of the lungs (MOS25). Analysis of the available data indicates a statistically significant lengthening of the PQ and sPQ intervals, as well as an increase in the rPQ and PQ/R–R indices in children with BA as the afterload changes in the small bronchi, indirectly assessed by MOC25. Conclusion: children with asthma who have spirometric signs of BHR in the test with PA may have electrocardiographic signs of a slowdown in supraventricular conduction.

Non-invasive predictors for infranodal conduction delay in patients with left bundle branch block after TAVR

Aims Left bundle branch block (LBBB) is the most common conduction disorder after transcatheter aortic valve replacement (TAVR) with an increased risk of atrioventricular (AV) block. The aim of the current study was to identify non-invasive predictors for infranodal conduction delay in patients with LBBB. Methods We analyzed consecutive patients undergoing TAVR with pre-existing or new-onset LBBB between August 2014 and August 2020. His ventricular (HV) interval measurement was performed on day 1 after TAVR. Baseline, procedural, as well as surface and intracardiac electrocardiographic parameters were included. Infranodal conduction delay was defined as HV interval > 55 ms. Results Of 825 patients screened after TAVR, 151 patients (82 ± 6 years, 39% male) with LBBB were included. Among these, infranodal conduction delay was observed in 25%. ΔPR (difference in PR interval after and before TAVR), PR and QRS duration after TAVR were significantly longer in the group with HV prolongation. In a multivariate analysis in patients with sinus rhythm (n = 123), ΔPR (OR per 10 ms increase: 1.52; 95%CI: 1.19–2.01; p = 0.002) was the only independent factor associated with infranodal conduction delay. A change in PR interval by 20 ms yielded a specificity of 83% and a sensitivity of 46%, with a negative predictive value of 84% and a positive predictive value of 45% to predict HV prolongation. Conclusions Simple analysis of surface ECG and a calculated ΔPR < 20 ms can be used as predictor for the absence of infranodal conduction delay in post-TAVR patients with LBBB. Graphical abstract

Proarrhythmia assessment in treatment with hydroxychloroquine and azithromycin hospitalized elderly COVID-19 patients - our experience

The aim of our study was to characterize the repolarization disorders propensity induced by drug-drug interaction. In this observational retrospective study, we report our experience on all elderly patients with ascertained diagnosis of coronavirus disease 2019 through nasopharyngeal swab with real time-polymerase chain reaction at our Pugliese-Ciaccio hospital in Catanzaro, who received hydroxychloroquine (HCQ), with or without azithromycin (AZY). 33 hospitalized patients were examined. We calculated QT value, cQT, QT dispersion, and cQT dispersion and examined possible progression on the basal electrocardiogram (T0) and after the insertion of the drug (T1). The QT value is increased by T0 vs T1 (370±40.74 vs 420±36.91 ms; P=0.000), as well as the cQT value (408±25.40 vs 451.54±58.81; P=0.003), the QT dispersion (QTd: 36.36±14.53 vs 50.90±13.12 ms; P=0.000); the dispersion of cQTc (cQTd 46.27±18.72 vs 63.18±21.93 ms; P=0.001). The ΔQT was 37.44±44.09 while the ΔcQT was 32.01±56.47). The main determinant of QTc prolongation is the number of drug at risk of prolongation of the QT that could influence the ventricular repolarization phase. The use of HCQ in combination with AZY, in patients suffering from severe acute respiratory syndrome-related coronavirus-2, can favor the onset of serious side effects, even potentially fatal. Finally, the measures of QTd and cQTd confirmed additional electrocardiographic parameters useful in identifying patients being treated with drugs at risk of potential adverse arrhythmic events following drug interaction.

Diagnostic Performance of Selected Baseline Electrocardiographic Parameters for Prediction of Left Ventricular Remodeling in Patients with ST-Segment Elevation Myocardial Infarction

Objective: To evaluate the diagnostic performance of selected baseline electrocardiographic (ECG) parameters as predictors of left ventricular remodeling (LVR) in patients with a first ST-segment elevation myocardial infarction (STEMI) treated with primary percutaneous coronary intervention (PCI). Methods: The study was performed as a single-center cohort study, with 249 patients (74.7% males) included in the final analysis. Nine baseline ECG parameters were evaluated, with respect to occurrence of LVR 6 months after STEMI (defined as an echocardiography-assessed relative >20% increase in end-diastolic left ventricular volume compared with the value at discharge from hospital). Results: The baseline ECG predictors of LVR, identified in univariate analysis, included the number of leads with ST-segment elevation (odds ratio (OR) 1.19, 95% confidence interval (CI) 1.03–1.38, p = 0.0212), number of leads with Q-waves (OR 1.21, 95% CI 1.07–1.37, p = 0.0033), sum of ST-segment elevation (OR 1.04, 95% CI 1.00–1.08; p = 0.0253) and maximal ST-segment elevation (OR 1.14; 95% CI 1.00–1.29; p = 0.0446). When added to demographic, clinical and angiographic data, the number of leads with ST-segment elevation (OR 1.17, 95% CI 1.01–1.36; p = 0.0413), number of leads with Q-waves (OR 1.15, 95% CI 1.01–1.32; p = 0.0354) and the sum of ST-segment elevation (OR 1.04, 95% CI 1.00–1.08; p = 0.0331) successfully predicted development of LVR in multivariate logistic regression models. However, after inclusion of biochemical data in multivariate models, none of the electrocardiographic parameters, but increasing body weight, TIMI flow after PCI < 3 and higher maximal values of myocardial necrosis biomarker, was independently associated with the occurrence of LVR 6 months after STEMI. Conclusions: Our study demonstrates modest utility of pre-reperfusion ECG for the prediction of LVR occurrence after six months of STEMI.