Isthmus characteristics in operated congenital heart disease with atrial tachycardias

Funding Acknowledgements

Type of funding sources: None.

Background

Patients with surgically repaired congenital heart disease (RCHD) present a high prevalence of atrial tachycardias (ATs). Although typical circuits dependent on the cavotricuspid isthmus (CTI-AFL) are the most frequent, intra-atrial re-entrant tachycardias (IART) are also common and a significant cause of recurrence.

Purpose

The aim of this observational study was to describe the characteristics of incisional isthmuses identified with ultrahigh-density electroanatomical mapping in patients with RCHD and to investigate their clinical significance.

Methods

The present investigation ambispectively examined 23 patients with RCHD. Mapping of index, induced and recurrent ATs was performed using a multipolar basket catheter and an ultra-high density mapping system. The conduction velocities (CV) and isthmus widths were calculated on isochronal and activation maps (Figure 1).

Results

Overall, 33 ATs in 23 patients were mapped in their entirety. 8 patients had no IART as index AT and no other zones of slow conduction. In the remaining 15 patients, 22 ATs were mapped (9 CTI-AFL/13 IART) and 27 zones of slow conduction were identified.

All identified critical and/or potential incisional isthmuses had a CV≤0.625 m/sec. By trichotomizing the predictor of CV, all isthmuses (9/9) of the middle third (CV 0.075-0.133 m/sec) were critical for an IART (either index or induced) and they were significantly more frequently associated with an IART (100%) compared with the isthmuses of the upper (44.4%) and lower third (66.7%) (p=0.034). Width of critical isthmuses was significantly narrower compared to width of non-critical isthmuses (10.1±3.1 mm versus 16.3±7.3 mm, p=0.049).

Among 9 induced/recurrent IARTs, critical incisional isthmus was visible at the activation map of the index AT in 6 patients (66.7%) and concealed (presented as line of block and/or collision of the wavefronts) in the remaining (33.3%). Index ATs with concealed isthmuses were significantly slower from index ATs without (U=6, p=0.047). During index ATs with cycle length <270 msec all critical isthmuses were visible (sensitivity 100%) (AUC=0.860, p=0.050).

Conclusions

The majority of isthmuses related to IARTs can be identified using ultrahigh-density activation mapping in patients with RCHD. A proportion can be overlooked due to functional block, especially during a slow index AT. CV and width of incisional isthmuses can be easily measured using novel mapping tools. Mid-range slow CV and narrow isthmus width may be predisposing factors of IART. Whether these features should promote ablation irrespective of stimulation protocol for AT induction needs further investigation.

Figure 1. Isthmus CV calculation using isochronal activation mapping.

Figure 2. An incisional isthmus, critical for an induced IART, was identified during a typical flutter. This isthmus had a narrow width (9.0 mm) and a mid-range slow CV (0.11 m/sec), features that may be predisposing factors for IARTs.

Intravenous lipid emulsion as an antidote in clinical toxicology: a systematic review

OBJECTIVE

Intravenous lipid emulsions (ILE) were developed many decades ago to supply nutritional requirements to patients unable to obtain adequate enteral nutrition. The utility of ILE was extended to therapeutics, facilitating the delivery of drugs. More recently, the potential for ILE to act as an antidote for inversion of drug toxicity has been recognized. This review aims to summarize the literature on ILE therapy as an antidote. Suggested mechanisms of action, safety profile, and recommendations on the administration of ILE in cases of drug intoxication are highlighted.

MATERIALS AND METHODS

A complete literature survey was performed using the PubMed database search to collect available information regarding mechanisms of ILE action as an antidote, ILE administration for drug toxicity, and presentation of adverse events.

RESULTS

A total of 102 studies met the selection criteria for inclusion in the review. Mainly used for local anesthetics toxicity, ILE therapy has been expanded in clinical toxicology involving overdose treatment of drugs other than local anesthetics. Partitioning in a lipid phase of fat droplets is a mechanism named the lipid sink phenomenon that has primarily been described to explain this action of ILE and remains the most widely accepted. At the same time, recent research has also revealed several molecular mechanisms that may contribute to ILE efficacy.

CONCLUSIONS

ILE therapy comprises a recognized approach in clinical toxicology. Due to the lack of randomized clinical trials, recommendations on administration are based on animal studies and published cases. Thus, the constantly increased knowledge about ILE therapy supports the need for a detailed appraisal.

Science and Orthodox Christianity: An Overview

This essay offers an overview of the history of the relations between science and Eastern Christianity based on Greek-language sources. The civilizations concerned are the Byzantine Empire, the Christian Orthodox communities of the Ottoman Empire, and modern Greece, as a case study of a national state. Beginning with the Greek Church Fathers, the essay investigates the ideas of theologians and scholars on nature. Neoplatonism, the theological debates of Iconoclasm and Hesychasm, the proposed union of the Eastern and Western Churches, and the complex relations with the Hellenic past all had notable impacts on the conception of science held by the Byzantine Orthodox. From the sixteenth through the eighteenth centuries, the Christian Orthodox world did not actively participate in the making of the new science that was developing in modern Europe. It had to deal with the assimilation of scientific ideas produced by Western Christianity, and its main concern was the “legitimacy” of knowledge that did not originate directly from its own spiritual tradition. Finally, with regard to the Greek state, beyond the specific points of contact between the sciences and Orthodox Christianity—pertaining, for example, to materialism, evolution, and the calendar—the essay presents the constant background engagement with religion visible in most public pronouncements of scientists and intellectuals.

Ambulatory Aortic Stiffness Is Associated With Narrow Retinal Arteriolar Caliber in Hypertensives: The SAFAR Study

BACKGROUND

Arterial stiffness measured under static conditions reclassifies significantly cardiovascular (CV) risk and associates with narrower retinal arterioles. However, arterial stiffness exhibits circadian variation, thus single static stiffness recordings do not correspond to the "usual" 24 hr, awake, and asleep average arterial stiffness. We aimed to test the hypothesis that ambulatory 24 hr, awake, and asleep aortic (a) pulse wave velocity (PWV) associate with retinal vessel calibers, independently of confounders and of static arterial stiffness, in hypertensive individuals free from diabetes and CV disease.

METHODS

Digital retinal images were obtained (181 individuals, age: 53.9±10.7 years, 55.2% men) and retinal vessel calibers were measured with validated software to determine central retinal arteriolar and venular equivalents (CRAE and CRVE, respectively); ambulatory (24 hr, awake, asleep) and static office aPWV were estimated by Mobil-O-Graph; and static office carotid to femoral (cf) PWV by SphygmoCor.

RESULTS

Regression analysis performed in 320 gradable retinal images showed that, after adjustment for confounders: (i) ambulatory aPWV was significantly associated with narrower retinal arterioles but not with venules; (ii) asleep aPWV had stronger associations with CRAE than awake aPWV; (iii) both ambulatory aPWV and cfPWV were associated mutually independently with narrower retinal arterioles; aPWV introduction in the model of cfPWV, improved model's R2 (P = 0.012). Similar discriminatory ability of 24 hr aPWV and of cfPWV to detect the presence of retinal arteriolar narrowing was found.

CONCLUSION

Ambulatory aPWV, estimated by an operator-independent method, provides additional information to cfPWV regarding the associations of arterial stiffness with the retinal vessel calibers.

Onwards facing backwards: the rhetoric of science in nineteenth-century Greece

The aim of this paper is to show how the Greek men of science negotiated a role for their enterprise within the Greek public sphere, from the institution of the modern Greek state in the early 1830s to the first decades of the twentieth century. By focusing on instances where they appeared in public in their official capacity as scientific experts, I describe the rhetorical schemata and the narrative strategies with which Greek science experts engaged the discourses prevalent in nineteenth- and early twentieth-century Greece. In the end, my goal is to show how they were neither zealots of modernization nor neutral actors struggling in isolated wastelands. Rather, they appear as energetic agents who used scientific expertise, national ideals and their privileged cultural positions to construct a rhetoric that would further all three. They engaged eagerly and consistently with emerging political views, scientific subjects and cultural and political events, without presenting themselves, or being seen, as doing anything qualitatively different from their peers abroad. Greek scientists cross-contextualized the scientific enterprise, situating it in the space in which they were active.