Scar architecture affects the electrophysiological characteristics of induced ventricular arrhythmias in hypertrophic cardiomyopathy

AIMS

Late gadolinium enhancement cardiac magnetic resonance (LGE-CMR) detects myocardial scarring, a risk factor for ventricular arrhythmias (VAs) in hypertrophic cardiomyopathy (HCM). The LGE-CMR distinguishes core, borderzone (BZ) fibrosis, and BZ channels, crucial components of re-entry circuits. We studied how scar architecture affects inducibility and electrophysiological traits of VA in HCM.

METHODS AND RESULTS

We correlated scar composition with programmed ventricular stimulation-inducible VA features using LGE intensity maps. Thirty consecutive patients were enrolled. Thirteen (43%) were non-inducible, 6 (20%) had inducible non-sustained, and 11 (37%) had inducible sustained mono (MMVT)- or polymorphic VT/VF (PVT/VF). Of 17 induced VA, 13 (76%) were MMVT that either ended spontaneously, persisted as sustained monomorphic, or degenerated into PVT/VF. Twenty-seven patients (90%) had LGE. Of these, 17 (57%) had non-sustained or sustained inducible VA. Scar mass significantly increased (P = 0.002) from non-inducible to inducible non-sustained and sustained VA patients in both the BZ and core components. Borderzone channels were found in 23%, 67%, and 91% of non-inducible, inducible non-sustained, and inducible sustained VA patients (P = 0.003). All 13 patients induced with MMVT or monomorphic-initiated PVT/VF had LGE. The origin of 10/13 of these VTs matched scar location, with 8/10 of these LGE regions showing BZ channels. During follow-up (20 months, interquartile range: 7-37), one patient with BZ channels and inducible PVT had an ICD shock for VF.

CONCLUSION

Scar architecture determines inducibility and electrophysiological traits of VA in HCM. Larger studies should explore the role of complex LGE patterns in refining risk assessment in HCM patients.

Assessing left atrial intramyocardial fat infiltration from computerized tomography angiography in patients with atrial fibrillation

AIMS

Epicardial adipose tissue might promote atrial fibrillation (AF) in several ways, including infiltrating the underlying atrial myocardium. However, the role of this potential mechanism has been poorly investigated. The aim of this study is to evaluate the presence of left atrial (LA) infiltrated adipose tissue (inFAT) by analysing multi-detector computer tomography (MDCT)-derived three-dimensional (3D) fat infiltration maps and to compare the extent of LA inFAT between patients without AF history, with paroxysmal, and with persistent AF.

METHODS AND RESULTS

Sixty consecutive patients with AF diagnosis (30 persistent and 30 paroxysmal) were enrolled and compared with 20 age-matched control; MDCT-derived images were post-processed to obtain 3D LA inFAT maps for all patients. Volume (mL) and mean signal intensities [(Hounsfield Units (HU)] of inFAT (HU -194; -5), dense inFAT (HU -194; -50), and fat-myocardial admixture (HU -50; -5) were automatically computed by the software. inFAT volume was significantly different across the three groups (P = 0.009), with post-hoc pairwise comparisons showing a significant increase in inFAT volume in persistent AF compared to controls (P = 0.006). Dense inFAT retained a significant difference also after correcting for body mass index (P = 0.028). In addition, more negative inFAT radiodensity values were found in AF patients. Regional distribution analysis showed a significantly higher regional distribution of LA inFAT at left and right superior pulmonary vein antra in AF patients.

CONCLUSION

Persistent forms of AF are associated with greater degree of LA intramyocardial adipose infiltration, independently of body mass index. Compared to controls, AF patients present higher LA inFAT volume at left and right superior pulmonary vein antra.

Clinical impact of aging on outcomes of cardioneuroablation for reflex syncope or functional bradycardia: Results from the cardionEuroabLation: patiEnt selection, imaGe integrAtioN and outComEs-The ELEGANCE multicenter study

BACKGROUND

Cardioneuroablation (CNA) is a novel treatment for reflex syncope. The effect of aging on CNA efficacy is not fully understood.

OBJECTIVE

The purpose of this study was to assess the impact of aging on candidacy and efficacy of CNA for treating vasovagal syncope (VVS), carotid sinus syndrome (CSS), and functional bradyarrhythmia.

METHODS

The ELEGANCE (cardionEuroabLation: patiEnt selection, imaGe integrAtioN and outComEs) multicenter study assessed CNA in patients with reflex syncope or severe functional bradyarrhythmia. Patients underwent pre-CNA Holter electrocardiography (ECG), head-up tilt testing (HUT), and electrophysiological study. CNA candidacy and efficacy was assessed in 14 young (18-40 years), 26 middle-aged (41-60 years), and 20 older (>60 years) patients.

RESULTS

Sixty patients (37 men; mean age 51 ± 16 years) underwent CNA. The majority (80%) had VVS, 8% had CSS, and 12% had functional bradycardia/atrioventricular block. Pre-CNA Holter ECG, HUT, and electrophysiological findings did not differ across age groups. Acute CNA success was 93%, without differences between age groups (P = .42). Post-CNA HUT response was negative in 53%, vasodepressor in 38%, cardioinhibitory in 7%, and mixed in 2%, without differences across age groups (P = .59). At follow-up (8 months, interquartile range 4-15), 53 patients (88%) were free of symptoms. Kaplan-Meier curves did not show differences in event-free survival between age groups (P = .29). The negative predictive value of a negative HUT was 91.7%.

CONCLUSION

CNA is a viable treatment for reflex syncope and functional bradyarrhythmia in all ages, and is highly effective in mixed VVS. HUT is a key step in postablation clinical assessment.

The critical isthmus of left atrial anterior wall flutter is mostly circumscribed into a small area immediately behind the aortic root. Implications for catheter ablation

Funding Acknowledgements

Type of funding sources: None.

Background

Left atrial flutters (LAFL) are typically observed in patients with previous ablation lines or surgery in the left atrium (LA). Less frequently, scar-related left atrial anterior wall (LAAW) flutters may occur. Although the presence of low-voltage areas (LVAs, a surrogate of scar) in the LA is considered an arrhythmogenic substrate and a marker of atrial cardiomyopathy, the pathophysiologic factors responsible for its formation remain unclear. We hypothesized that compression of the LAAW by the aortic root could be responsible of LVAs found in the LAAW, and therefore, be the substrate for the development of LAAW flutter.

Purpose

We aimed to describe: 1) the relationship between the aortic root and the presence of LVAs in the LAAW, which is the substrate for reentry; and 2) the clinical and electrophysiological characteristics of LAAW atrial flutter.

Methods

Consecutive patients referred for LAFL ablation between April 2019 and September 2022 in a single center were retrospectively collected. Among 55 patients with LAFL, 10 (18%) demonstrated a macroreentrant circuit with a critical isthmus identified in the LAAW, in the absence of previous ablation lines or surgery, and were included in the analysis. Previous pulmonary vein isolation (PVI) was not an exclusion criterion. All patients underwent a multidetector computerized tomography (MDCT) prior to the procedure and the images were analyzed using ADAS 3DTM imaging platform. Activation mapping was performed in all patients using a multielectrode mapping catheter and CARTO 3 navigation system.

Results

9 of 10 patients were male (mean age 74,3 ± 6,3 years). LA enlargement was present in all patients (48,3 ± 4,7 mm) and the mean aortic root diameter was 34,8 ± 3,4 mm. The mean LAAW flutter cycle length was 293,4 ± 68,3 ms. In 9 of the patients (90%), the LAAW flutter critical isthmus was just behind the aortic root, separated by < 1 mm according to the LA-aortic root fingerprinted isodistance map (mean fingerprinted isodistance area was 5,8 ± 2,5 cm2). The remaining patient had the critical isthmus just below the aortic root, between the area in contact with the latter and the mitral annulus. Furthermore, in all cases, the critical isthmus was immersed in LVAs. All but 1 LAAW flutter terminated during radiofrequency (RF) energy applications and rendered it non-inducible. After a median follow-up of 13,6 months (IQ range 5,3-21,6), 7 patients (70%) remained without recurrences.

Conclusion

In patients with LAAW atrial flutter, the presence of LVAs and the critical isthmus of the tachycardia are mostly circumscribed into small areas immediately behind the aortic root. Knowledge of this close relationship and the use of the isodistance map could be useful when mapping and ablating LAAW flutter, helping to straightforward the ablation procedure.

Adsorption of mycoplasma virus P1 to host cells

The adsorption of mycoplasma virus P1, a virus which infects some strains of Mycoplasma pulmonis, to host cells was examined. Mutants of M. pulmonis to which P1 virus did not adsorb were isolated. Proteins from the mutants and from wild-type cells were compared by two-dimensional polyacrylamide gel electrophoresis, and the only observed difference was in the surface antigen V-1. The electrophoretic properties of V-1 also correlated with the host range of the virus. These data strongly suggest that the V-1 antigen affects adsorption of P1 virus to host cells.

Transformation of Mycoplasma pulmonis and Mycoplasma hyorhinis: transposition of Tn916 and formation of cointegrate structures

A procedure for transformation of the murine pathogen Mycoplasma pulmonis with plasmid pAM120 was developed. This plasmid replicates in Escherichia coli and contains the gram-positive transposon Tn916. The transformation protocol also proved effective for the swine pathogen Mycoplasma hyorhinis. The tetracycline resistance determinant of Tn916 was expressed in transformed myocoplasma cells, and Tn916 was found inserted into numerous sites in the recipient chromosomes of M. pulmonis and M. hyorhinis, indicating that transposition had occurred. Interestingly, some transformants of M. pulmonis and M. hyorhinis contained cointegrate structures which apparently had a complete copy of the entire donor plasmid (pAM120) inserted into the recipient chromosome. Subsequent transposition of inserted Tn916 was observed in passaged clones of transformed M. pulmonis.

Isolation of a virus from Mycoplasma pulmonis

A virus designated mycoplasma virus P1 has been isolated from Mycoplasma pulmonis. The virus infects M. pulmonis strain UAB 6510, and a plaque-forming unit assay has been developed. P1 has a tailed, polyhedral morphology with a head diameter of about 28 nm. Nucleic acid isolated from crude preparations of P1 virus contains double-stranded RNA, suggesting that P1 may be the first example of an RNA-containing mycoplasma virus.

[Valve replacement using an artificial ball prosthesis manufactured in Mexico]

This report documents our early experience with a cage ball valve manufactured in Mexico. Between May 1985 and March, 1986, 25 consecutive replacements have been performed in 23 patients, 14 underwent aortic valve replacement, 9 received a mitral valve, and 2 received both aortic and mitral valves. Their mean age was 32 years. Most of the patients had rheumatic heart disease. Their functional class prior to operation was as follows: six patients fell into class II, 15 into class III and 2 into class IV. One case died in the operative period. All patients have been followed for a mean period of 5 months. Late mortality has not occurred in any patient. Valve-related complications were not present. The post-operative NYHA functional class was as follows: seventeen (80%) fell into class I and five (20%) fell into class II. The actuarial survival rate 10 months after operation was 96.0%. Our study suggests that the cage ball valve has a good performance, the clinical results justify continuing investigation of this prosthesis.