QT interval estimation in patients with right bundle branch block using validated formulas for left bundle branch block

Funding Acknowledgements

Type of funding sources: None.

BACKGROUND

Adequate measurement of the QT interval is of paramount importance in order to identify patients at higher risk for ventricular arrhythmias. Previous studies have described different methods to estimate baseline QT in patients with left bundle branch block (LBBB). However, the evidence regarding the assessment of QT interval in the setting of right bundle branch block (RBBB) is scarce. 

PURPOSE

We aimed to analyze the feasibility and accuracy of the different formulas described for LBBB in the estimation of the QT interval in RBBB. 

METHODS

We enrolled patients who underwent left sided electrophysiologic procedures. All patients were in sinus rhythm and had narrow QRS. Pacing was performed from the left atrial appendage for baseline measurements, and from the left aspect of the interventricular septum (selective capture of the left bundle was attempted) to measure RBBB QT and QRS. Pacing cycle length was 800 ms or slightly below patients´ intrinsic rhythm at both locations. Measurements were performed manually (using digital calipers) according to current recommendations and corrected using Bazett. Validated formulas for LBBB QT considered are described in table 1. 

RESULTS

50 patients (42 cryoballoon pulmonary veins isolation (PVI), 4 radiofrequency PVI, 4 concealed left accessory pathways). 70% were male. Mean age was 62 ± 11 years old. Left ventricle ejection fraction was 58 ± 10%. 66% and 60% of the patients were taking betablockers and antiarrhythmic drugs, respectively. Mean pacing cycle length was 707 ± 99 ms. Baseline measurements: QRS 95 ± 10, QT 391 ± 36, QTc 467 ± 39 ms. RBBB measurements: QRS 165 ± 21, QT 448 ± 46, QTc 531 ± 52 ms. Correlations between baseline and estimated QTc were good for all the formulas (table 1). Reliability analysis showed that both Yankelson and Wang methods had the highest intraclass correlation coefficients (ICC) when trying to estimate baseline QTc. 

CONCLUSIONS

Previously described formulas for LBBB exhibit marked differences regarding reliability in the estimation of QTc interval in the setting of RBBB. According to our results, Yankelson’s method shows the most consistent agreement when estimating baseline QTc interval in patients with RBBB. Table 1.LBBB METHODFormula to estimate baseline QTcPearson’s R correlation coefficientCI (95%)Intraclass correlation coefficientCI (95%)YankelsonQTc - QRS + 95 (m) or 88 (f)0.805(0.632-0.977)0.882(0.788-0.934)Bogossian**QT - (QRS/2)0.813(0.644-0.982)0.756(-0.127-0.919)Wang**QT - (0.86*QRS - 71)0.801(0.627-0.974)0.834(0.465-0.930)Tang-Rabkin0.945*QTcRabkin - 260.722(0.521-0.923)0.711(0.019-0.885)RautaharjuQT - 155*(60/heart rate - 1) - 0.93*(QRS - 139) - 22 (m) or - 34 (f)0.780(0.599-0.961)0.105(-0.017-0.381)**Bogossian and Wang required additional HR correction (Bazett).  Abstract Figure 1. Bland-Altman

Usefulness of strain imaging to determine prognosis in pulmonary hypertension

Introduction

Pulmonary hypertension (PH) is defined as mean pulmonary arterial pressure (mPAP) ≥25 mmHg at rest, measured by right heart catheterization (RHC).

Purpose

To describe classical and myocardial deformation echocardiographic parameters in patients with established PH and to identify prognostic variables

Methods

We prospectively enrolled 76 patients with mPAP ≥25 mmHg undergoing RHC between 2017 and 2018. All subjects underwent transthoracic echocardiography (TTE) according to the latest ASE/EACVI guidelines the same day of the RHC. Strain analysis was carried out by speckle-tracking echocardiography (QLAB 10.7, Philips). Clinical events during the follow-up were: acute heart failure hospitalization, cardiac transplant and all-cause mortality.

Results

Mean age was 59±12, 43.4% were women and 49 patients (64.5%) belonged to group 2 of PH. The median follow-up was 288 (ICR 92–534) days. Total number of events was 42 (55.3%, 9 deaths). Variables associated to events are shown in Table 1. All classic LV and RV systolic function and strain parameters were associated with a worse prognosis, being free-wall RV longitudinal strain (RVLS) the only one that remained as a prognostic factor in mutivariate analysis. Other variables associated with a worse prognosis were PCP>15 mmHg and NT-proBNP>1800, the latter being independent predictor of events. The attached figure shows event-free survival curves for the global population divided according to whether or not they belong to group II PH.

Conclusions

Our data highlight the prognostic value of free-wall RVLS and NT-proBNP in patients with established PH. NT-ProBNP was only useful in group II PH while free-wall RVLS identified patients with a higher risk of events in both groups, mainly in patients with heart disease

Free event survival Curves

Funding Acknowledgement

Type of funding source: None

p38 MAPK and NF-kappa B collaborate to induce interleukin-6 gene expression and release. Evidence for a cytoprotective autocrine signaling pathway in a cardiac myocyte model system

In cardiac myocytes, the stimulation of p38 MAPK by the MAPKK, MKK6, activates the transcription factor, NF-kappaB, and protects cells from apoptosis. In the present study in primary neonatal rat cardiac myocytes, constitutively active MKK6, MKK6(Glu), bound to IkappaB kinase (IKK)-beta and stimulated its abilities to phosphorylate IkappaB and to activate NF-kappaB. MKK6(Glu) induced NF-kappaB-dependent interleukin (IL)-6 transcription and IL-6 release in a p38-dependent manner. IL-6 protected myocardial cells against apoptosis. Like IL-6, TNF-alpha, which activates both NF-kappaB and p38, also induced p38-dependent IL-6 expression and release and protected myocytes from apoptotis. While TNF-alpha was relatively ineffective, IL-6 activated myocardial cell STAT3 by about 8-fold, indicating a probable role for this transcription factor in IL-6-mediated protection from apoptosis. TNF-alpha-mediated IL-6 induction was inhibited by a kinase-inactive form of the MAPKKK, TGF-beta activated protein kinase (Tak1), which is known to activate p38 and NF-kappaB in other cell types. Thus, by stimulating both p38 and NF-kappaB, Tak1-activating cytokines, like TNF-alpha, can induce IL-6 expression and release. Moreover, the myocyte-derived IL-6 may then function in an autocrine and/or paracrine fashion to augment myocardial cell survival during stresses that activate p38.

Vasotocin maintains multiple call types in the gray treefrog, Hyla versicolor

The neuropeptide arginine vasotocin (AVT) influences vocalizations in some anuran amphibians but it is unknown whether AVT alters all vocal behaviors of a species similarly. We first characterized the vocal repertoire of male gray treefrogs (Hyla versicolor). Three different call types were distinguished by unique sets of temporal and spectral features. Second, we examined the effects of AVT on each call type by injecting frogs with either AVT (100 microg; intraperitoneal) or saline and recording subsequent behavior. In the field, AVT maintained advertisement calling, whereas calling ceased in saline-injected animals. Advertisement call rate in AVT-injected males fell significantly and dominant frequency of the call was significantly higher. In the laboratory, AVT induced advertisement calling in males that were not initially vocalizing and dominant frequency was also significantly higher in these males. AVT maintained aggressive calling similarly but the characteristics of aggressive calls were not altered by AVT. There were no significant differences in release call behavior between AVT- and saline-injected groups; however, release call duration decreased significantly in AVT-injected animals, compared with preinjection values for the same animals. The effects of AVT on vocal behavior in this species are therefore not the same for each call type. AVT may act at more general motivational levels in the central nervous system and other neural or endocrine factors may control choice of call type and direct motor output.