Clinical Protocol for Selecting Intracardiac or Transesophageal Echocardiography-Guided Left Atrial Appendage Occlusion.

Intracardiac echocardiography (ICE) has emerged as an alternative to transesophageal echo (TEE) to guide left atrial appendage occlusion (LAAO). We established a protocol to select patients appropriate for ICE guidance. Patients who underwent LAAO with the Watchman or Watchman FLX device (Boston Scientific, Marlborough, Massachusetts) from January 2018 to March 2022 at a large United States center were included. The novel protocol prospectively selected TEE or ICE guidance beginning in January 2020; previous LAAO procedures were retrospectively included. ICE was selected for patients with uninterrupted anticoagulation and appropriate LAA anatomy, renal function, and moderate sedation tolerance. In-hospital outcomes with successful implantation without conversion to TEE guidance, no peridevice leak, and no procedural complications were compared. Composite 1-year outcome included freedom from peridevice leak, device-related thrombus, stroke, and all-cause mortality. A total of 234 patients were included; the mean age was 76.1 ± 8.3 years old, and 42.3% were female. ICE guidance was used for 63 procedures; TEE guidance was used for 171 procedures. For the composite outcome, ICE-guided LAAO was superior to TEE-guided LAAO (risk difference 0.102, 96.8% vs 86.5%, 95% confidence interval 0.003 to 0.203, p = 0.029). In comparison to the TEE-guided group, ICE-guided procedures were shorter (89.1 ± 26.3 vs 99.8 ± 30.0 min, p = 0.0087) with less general anesthesia (26.6% vs 98.8%, p <0.0001). One-year composite adverse outcomes did not differ significantly (80.7% vs 88.9%, p = 0.17). In conclusion, the protocol to select appropriate patients for ICE versus TEE guidance for LAAO is safe and effective. Larger studies are indicated to validate this approach to improve outcomes, shorten procedures, and avoid general anesthesia.

Laser Lead Extraction Complicated by Avulsed Tricuspid Subvalvular Apparatus with Severe Tricuspid Regurgitation.

The use of laser lead extraction (LLE) to remove pacemaker or implantable cardioverter-defibrillator leads has become increasingly prevalent. This advanced technique has been shown to be highly effective and safe. We report a rare case of severe traumatic tricuspid regurgitation after LLE that led to death.

Physiological phenotyping of the adult zebrafish heart.

The zebrafish has proven to be an excellent organism for manipulation of its genome from a long history of transcript down-regulation using morpholino oligimers to more recent genome editing tools such as CRISPR-Cas9. Early forward and reverse genetic screens significantly benefited from the transparency of zebrafish embryos, allowing cardiac development as a function of genetics to be directly observed. However, gradual loss of transparency with subsequent maturation limited many of these approaches to the first several days post-fertilization. As many genes are developmentally regulated, the immature phenotype is not entirely indicative of that of the mature zebrafish. For accurate phenotyping, subsequent developmental stages including full maturation must also be considered. In adult zebrafish, cardiac function can now be studied in great detail due both to the size of the hearts as well as recent technological improvements. Because of their small size, zebrafish are particularly amenable to high frequency echocardiography for detailed functional recordings. Although relatively small, the hearts are easily excised and contractile parameters can be measured from whole hearts, heart slices, individual cardiomyocytes and even single myofibrils. Similarly, electrical activity can also be measured using a variety of techniques, including in vivo and ex vivo electrocardiograms, optical mapping and traditional microelectrode techniques. In this report, the major advantages and technical considerations of these physiological tools are discussed.

Zebrafish as a model of mammalian cardiac function: Optically mapping the interplay of temperature and rate on voltage and calcium dynamics.

The zebrafish (Danio rerio) heart is a viable model of mammalian cardiovascular function due to similarities in heart rate, ultrastructure, and action potential morphology. Zebrafish are able to tolerate a wide range of naturally occurring temperatures through altering chronotropic and inotropic properties of the heart. Optical mapping of cannulated zebrafish hearts can be used to assess the effect of temperature on excitation-contraction (EC) coupling and to explore the mechanisms underlying voltage (Vm) and calcium (Ca2+) transients. Applicability of zebrafish as a model of mammalian cardiac physiology should be understood in the context of numerous subtle differences in structure, ion channel expression, and Ca2+ handling. In contrast to mammalian systems, Ca2+ release from the sarcoplasmic reticulum (SR) plays a relatively small role in activating the contractile apparatus in teleosts, which may contribute to differences in restitution. The contractile function of the zebrafish heart is closely tied to extracellular Ca2+ which enters cardiomyocytes through L-type Ca2+ channel (LTCC), T-type Ca2+ channel (TTCC), and the sodium-calcium exchanger (NCX). Novel data found that despite large temperature effects on heart rate, Vm, and Ca2+ durations, the relationship between Vm and Ca2+ signals was only minimally altered in the face of acute temperature change. This suggests that zebrafish Vm and Ca2+ kinetics are largely rate-independent. In comparison to mammalian systems, zebrafish Ca2+ cycling is inherently more dependent on transsarcolemmal Ca2+ transport and less reliant on SR Ca2+ release. However, the compensatory actions of various components of the Ca2+ cycling machinery of the zebrafish cardiomyocytes, allow for maintenance of EC coupling over a wide range of environmental temperatures.

Construction and use of a zebrafish heart voltage and calcium optical mapping system, with integrated electrocardiogram and programmable electrical stimulation.

Zebrafish are increasingly being used as a model of vertebrate cardiology due to mammalian-like cardiac properties in many respects. The size and fecundity of zebrafish make them suitable for large-scale genetic and pharmacological screening. In larger mammalian hearts, optical mapping is often used to investigate the interplay between voltage and calcium dynamics and to investigate their respective roles in arrhythmogenesis. This report outlines the construction of an optical mapping system for use with zebrafish hearts, using the voltage-sensitive dye RH 237 and the calcium indicator dye Rhod-2 using two industrial-level CCD cameras. With the use of economical cameras and a common 532-nm diode laser for excitation, the rate dependence of voltage and calcium dynamics within the atrial and ventricular compartments can be simultaneously determined. At 140 beats/min, the atrial action potential duration was 36 ms and the transient duration was 53 ms. With the use of a programmable electrical stimulator, a shallow rate dependence of 3 and 4 ms per 100 beats/min was observed, respectively. In the ventricle the action potential duration was 109 ms and the transient duration was 124 ms, with a steeper rate dependence of 12 and 16 ms per 100 beats/min. Synchronous electrocardiograms and optical mapping recordings were recorded, in which the P-wave aligns with the atrial voltage peak and R-wave aligns with the ventricular peak. A simple optical pathway and imaging chamber are detailed along with schematics for the in-house construction of the electrocardiogram amplifier and electrical stimulator. Laboratory procedures necessary for zebrafish heart isolation, cannulation, and loading are also presented.