"On-Off" phenomenon in a case of concealed left lateral atrio-ventricular accessory pathway - What is the mechanism?

We report a case of symptomatic supraventricular tachycardia who had absent VA conduction during electrophysiology study. The interesting finding was appearance of VA conduction only at a specific cycle length of ventricular pacing which reproducibly induced a sustained orthodromic re-entrant tachycardia (ORT). We review the literature and conclude that supernormal AP conduction can explain such phenomenon.

Absent ventriculo-atrial conduction during right ventricular apical pacing but nodal response during para-Hisian pacing - What is the mechanism?

A 13-year-old-girl presented with one episode of pre-syncope while standing in a train. Her ECG was suggestive of preexcitation. Echocardiography revealed structurally normal heart without any ventricular hypertrophy. During electrophysiology study, her ventriculo-atrial (VA) conduction was absent even on isoprenaline. However, a para-Hisian pacing maneuver (PHP) revealed consistent VA conduction with a nodal response. This finding indicated that the VA dissociation at baseline was at infra-Hisian (VH) level and conduction at HA level was intact. In addition, this finding is coherent with a speculation of a fasciculo-ventricular pathway (FVP) resulting in such an ECG pattern in her. Pacing from various atrial sites (right atrium, coronary sinus) exhibited nearly fixed preexcitation and short non-varying HV interval confirmatory of FVP. Testing for a PRKAG mutation was advised for her.

Retrograde ventriculoatrial jump-What is the mechanism?

During ventricular extra stimuli(VES) protocol a VA jump was noted. In upper panel with VES @ 500/270 ms (Fig A) the His signal appeared after the A-EGM, ruling out pure nodal VA conduction and confirming presence of an accessory pathway (AP). The H signal was delayed due to probable retrograde RBBB. The atrium was already depolarised via AP and the VA traversing via left bundle-His-node got blocked with a H signal. In the lower panel with VES of 500/260 ms the retrograde AP conduction reached the effective refractory period and pure nodal VA conduction took place along with retrograde RBBB. The retrograde VA jump was hence due to a jump from AP to AV node.

Effect of nutritional parameters on microbial production of L-Asparaginase by novel Brevibacillus borstelensis ML12.

L-Asparaginase owes considerable significance in food and pharmaceutical applications. L-Asparaginase is an antineoplastic enzyme that finds application in the treatment of Acute Lymphoblastic Leukemia (ALL) and in mitigating acrylamide (a potent carcinogen) production during baking. In this study, we aimed to optimize nutritional parameters that are significant in initiating and regulating a bioprocess system in order to maximize enzyme production from a novel isolated bacterial species Brevibacillus borstelensis ML12 so the high-yielding enzyme producers can be selected and utilized for better efficacy of this commercially viable enzyme in pharmaceutical field, food industry, in biosensors and as an antioxidant growth kinetics study of the organism was performed and the maximum specific growth rate µo (min-1) and Monod half saturation constant Ks for L-Asparagine came out to be µo = 0.0189 min-1 and Ks = 2.44 mM, respectively at 0.04 M asparagine concentration and 37 °C. Effect of different nutritional parameters like carbohydrates, organic and inorganic nitrogen sources, L-Asparagine, minerals, surfactants and bile were performed. Maximum L-Asparaginase production occurred at 0.01% dextrose, 20 g L-1 L-Asparagine, 10 mM cobalt chloride, 0.1% Tween 80 and 1% bile concentrations (237.319 IU mL-1).

Inappropriate ventricular fibrillation annotation and defibrillator discharge despite the same tachycardia cycle length in ventricular tachycardia-1 zone in an Abbott defibrillator - What is the mechanism?

Newer devices incorporate advanced algorithms to have more accurate delivery of implantable cardioverter-defibrillator (ICD) therapy. Newer models of Abbott Implantable cardioverter-defibrillators like Gallant and Entrant have a new ventricular fibrillation (VF) therapy assurance algorithm. This algorithm has a proven role in avoiding under-detection of VF where some of the smaller electrograms are under-sensed. We report a case of ventricular fibrillation therapy assurance (VFTA) algorithm malfunction in a 48-year-old lady having single chamber Entrant Implantable cardioverter-defibrillator, where the patient received inappropriate therapies. The VFTA algorithm eventually had to be turned off.

An Unusual Genetic Observation in a Case of Short-Coupled PVC-Triggered Ventricular Fibrillation.

Ventricular fibrillation induced by short-coupled premature ventricular complex is an uncommon cause of cardiac arrest in young individuals with no structural heart disease. The genetic substrate of this condition is heterogeneous and remains incompletely defined. We describe a case of short-coupled premature ventricular complex-triggered ventricular fibrillation with a likely pathogenic variant in the titin (TTN) gene. (Level of Difficulty: Advanced.).

Normal pacing function with normal impedance trends despite evident lead fracture in an implantable defibrillator - What is the mechanism?

A 63-year-old lady with a high-grade atrioventricular (AV) block and a structurally normal heart underwent permanent pacemaker implantation (dual chamber, Medtronic Ltd) 8 years back. On follow up, she had a recurrence of syncope after 3 years. The device interrogation at that time had revealed ventricular tachycardia (VT) for which she underwent implantable cardioverter defibrillator (ICD, Medtronic Ltd, Egida DR, DF1) upgradation at another center (electrograms not available). Now, she presents with episodes of presyncope after another 5 years. The Echocardiography was unremarkable. The ICD was interrogated & there was a stored ventricular fibrillation (VF) episode. But the electrograms suggested noise over a true VF electrogram noted in both near and far-field. In all probability, the VF was not a true one which might have arisen from some lead noise or from an electromagnetic interference (EMI). Fluoroscopy revealed an evident lead fracture near the superior vena cava (SVC) coil. The stored electrogram (EGM) characteristics also suggested possible lead noise rather than a true VF. She was advised for lead revision. Interestingly, all pacing parameters were normal along with normal impedance despite the evident lead fracture. This happened due to the ICD lead arrangements as there are separate electrodes for the SVC/RV coil and pacing. While the SVC coil was damaged, the pacing electrodes remained unaffected. Since the patient has no episode of true VT/NSVT and the echocardiography was normal, she was managed temporarily by changing the pacemaker to asynchronous (DOO) mode.

Antiobesity, Antihyperglycemic, and Antidepressive Potentiality of Rice Fermented Food Through Modulation of Intestinal Microbiota.

The present study has been aimed at evaluating the antiobesity, antihyperglycemic, and antidepressive potentials of Asparagus racemosus starter-based rice fermented foods. High-throughput NGS technology has revealed a number of bacterial genera in the prepared fermented rice, such as Lactobacillus (29.44%), Brevundimonas (16.21%), Stenotrophomonas (6.18%), Pseudomonas (3.11%), Bacillus (2.88%), and others (<2%). Eight-week administration of rice fermented food has increased food intake, whole-body weight, organ weight, different fat masses, serum lipid profiles, and histology of liver and adipose tissues in HFD-induced obese mice. In addition, upregulation of fatty acid oxidation and downregulation of adipocytogenesis- and lypogenesis-related genes along with the expression of their regulatory nuclear factors such as PPARα, PPARγ, PPARδ, and SREBP-1c have also been noted. Moreover, fermented food decreases fasting blood glucose level and improves glucose and insulin tolerance as well as the expression of GLUT4 receptor. Antiobesity and antihyperglycemic effects are also supported by the changes in insulin, leptin, and adiponectin hormone levels. The real-time polymerase chain reaction (RT-PCR) and denaturing gradient gel electrophoresis (DGGE) analyses have clearly demonstrated the intense colonization of Bacteroides, Lactobacillus, and Bifidobacterium, as well as the suppressed growth rate of γ- and δ-Proteobacteria and Firmicutes in the gut after fermented food intake. In the intestine, the latter group of microorganisms possibly modulate short-chain fatty acid (SCFA) levels such as acetate, butyrate, and propionate more than twofold. The impairment of memory-learning and anxiety-like obesity-associated cognitive phenotypes is mitigated significantly (p < 0.01) by fermented food as well. Thus, the formulated fermented food could be used as a natural therapeutic to alleviate obesity and its associated psychological and pathophysiological ailments.

Railroad Pattern of Atrial Intervals in a Dual-chamber Pacemaker Patient-What Is the Mechanism and How to Manage?

A 55-year-old woman with a dual-chamber pacemaker presented with brief episodes of rapid palpitation. The device recorded several stored atrial high-rate and ventricular high-rate episodes. The atrial intervals showed an interesting railroad track pattern during a non-sustained episode of ventricular tachycardia. We discussed the differential diagnosis of railroad track patterns on the atrial channel. In our case, it was related to far-field R-wave oversensing.

Change in the H-V Interval Without a Change in QRS Morphology During Atrial Pacing in a Case of Wolff-Parkinson-White Syndrome-What is the Mechanism?

In the background of an accessory pathway (AP), the H-V interval can vary during atrial/coronary sinus pacing, but only with a concomitant change in the QRS morphology and the degree of pre-excitation. In an interesting case of a 62-year-old woman, the H-V interval varied during coronary sinus pacing despite a fixed pre-excitation. This appears to have happened due to infra-Hisian complete atrioventricular dissociation, which resulted from iatrogenic mechanical bumping of the left anterior fascicle in the background of right bundle branch block and left posterior hemiblock.