Premature Ventricular Contraction Coupling Interval Variability Destabilizes Cardiac Neuronal and Electrophysiological Control: Insights From Simultaneous Cardioneural Mapping.

BACKGROUND: Variability in premature ventricular contraction (PVC) coupling interval (CI) increases the risk of cardiomyopathy and sudden death. The autonomic nervous system regulates cardiac electrical and mechanical indices, and its dysregulation plays an important role in cardiac disease pathogenesis. The impact of PVCs on the intrinsic cardiac nervous system, a neural network on the heart, remains unknown. The objective was to determine the effect of PVCs and CI on intrinsic cardiac nervous system function in generating cardiac neuronal and electric instability using a novel cardioneural mapping approach. METHODS AND RESULTS: In a porcine model (n=8), neuronal activity was recorded from a ventricular ganglion using a microelectrode array, and cardiac electrophysiological mapping was performed. Neurons were functionally classified based on their response to afferent and efferent cardiovascular stimuli, with neurons that responded to both defined as convergent (local reflex processors). Dynamic changes in neuronal activity were then evaluated in response to right ventricular outflow tract PVCs with fixed short, fixed long, and variable CI. PVC delivery elicited a greater neuronal response than all other stimuli (P<0.001). Compared with fixed short and long CI, PVCs with variable CI had a greater impact on neuronal response (P<0.05 versus short CI), particularly on convergent neurons (P<0.05), as well as neurons receiving sympathetic (P<0.05) and parasympathetic input (P<0.05). The greatest cardiac electric instability was also observed after variable (short) CI PVCs. CONCLUSIONS: Variable CI PVCs affect critical populations of intrinsic cardiac nervous system neurons and alter cardiac repolarization. These changes may be critical for arrhythmogenesis and remodeling, leading to cardiomyopathy.

Relationship between sinus rhythm late activation zones and critical sites for scar-related ventricular tachycardia: systematic analysis of isochronal late activation mapping.

BACKGROUND: It is not known whether the most delayed late potentials are functionally most specific for scar-related ventricular tachycardia (VT) circuits. METHODS AND RESULTS: Isochronal late activation maps were constructed to display ventricular activation during sinus rhythm over 8 isochrones. Analysis was performed at successful VT termination sites and prospectively tested. Thirty-three patients with 47 scar-related VTs where a critical site was demonstrated by termination of VT during ablation were retrospectively analyzed. In those who underwent mapping of multiple surfaces, 90% of critical sites were on the surface that contained the latest late potential. However, only 11% of critical sites were localized to the latest isochrone (87.5%-100%) of ventricular activation. The median percentage of latest activation at critical sites was 78% at a distance from the latest isochrone of 18 mm. Sites critical to reentry were harbored in regions with slow conduction velocity, where 3 isochrones were present within a 1-cm radius. Ten consecutive patients underwent ablation prospectively guided by isochronal late activation maps, targeting concentric isochrones outside of the latest isochrone. Elimination of the targeted VT was achieved in 90%. Termination of VT was achieved in 6 patients at a mean ventricular activation percentage of 78%, with only 1 requiring ablation in the latest isochrone. CONCLUSIONS: Late potentials identified in the latest isochrone of activation during sinus rhythm are infrequently correlated with successful ablation sites for VT. The targeting of slow conduction regions propagating into the latest zone of activation may be a novel and promising strategy for substrate modification.

A Case of Type 2 Amiodarone-Induced Thyrotoxicosis That Underwent Total Thyroidectomy under High-Dose Steroid Administration.

Amiodarone is used commonly and effectively in the treatment of arrhythmia; however, it may cause thyrotoxicosis categorized into two types: iodine-induced hyperthyroidism (type 1 amiodarone-induced thyrotoxicosis (AIT)) and destructive thyroiditis (type 2 AIT). We experienced a case of type 2 AIT, in which high-dose steroid was administered intravenously, and we finally decided to perform total thyroidectomy, resulting in a complete cure of the AIT. Even though steroid had been administered to the patient (maximum 80 mg of prednisolone), the operation was performed safely and no acute adrenal crisis as steroid withdrawal syndrome was found after the operation. Few cases of type 2 AIT that underwent total thyroidectomy with high-dose steroid administration have been reported. The current case suggests that total thyroidectomy should be taken into consideration for patients with AIT who cannot be controlled by medical treatment and even in those under high-dose steroid administration.

Pseudo-postpacing interval of diastolic potential after entrainment pacing of remote bystander pathway in reentrant ventricular tachycardia.

After entrainment pacing, the postpacing interval of a diastolic potential may be misinterpreted if the distal tip of the ablation catheter captures a remote bystander pathway adjacent to the critical isthmus of a complex reentrant circuit in a structurally diseased heart. We discuss this possible pitfall of entrainment mapping of reentrant ventricular tachycardia, observed after a healed myocardial infarction.

Electroanatomically estimated length of slow pathway in atrioventricular nodal reentrant tachycardia.

The length of the slow pathway (SP-L) in atrioventricular (AV) nodal reentrant tachycardia (NRT) has never been measured clinically. We studied the relationship among (a) SP-L, i.e., the distance between the most proximal His bundle (H) recording and the most posterior site of radiofrequency (RF) delivery associated with a junctional rhythm, (b) the length of Koch's triangle (Koch-L), (c) the conduction time over the slow pathway (SP-T), measured by the AH interval during AVNRT at baseline, and (d) the distance between H and the site of successful ablation (SucABL-L) in 26 women and 20 men (mean age 64.6 ± 11.6 years), using a stepwise approach and an electroanatomic mapping system (EAMS). SP-L (15.0 ± 5.8 mm) was correlated with Koch-L (18.6 ± 5.6 mm; R 2 = 0.1665, P < 0.005), SP-T (415 ± 100 ms; R 2 = 0.3425, P = 0.036), and SucABL-L (11.6 ± 4.7 mm; R 2 = 0.5243, P < 0.0001). The site of successful ablation was located within 10 mm of the posterior end of the SP in 38 patients (82.6 %). EAMS-guided RF ablation, using a stepwise approach, revealed individual variations in SP-L related to the size of Koch's triangle and AH interval during AVNRT. Since the site of successful ablation was also correlated with SP-L and was usually located near the posterior end of the SP, ablating anteriorly, away from the posterior end, is not a prerequisite for the success of ablation procedures.

Characteristics of systolic and diastolic potentials recorded in the left interventricular septum in verapamil-sensitive left ventricular tachycardia.

We studied the electrophysiological characteristics of systolic (SP) and diastolic (DP) potentials recorded during sinus rhythm (SR) in the left interventricular septum of a 27 year-old woman presenting with verapamil-sensitive idiopathic left ventricular tachycardia (VT). During SR, and during VT, SP was activated from ventricular base-to-apex, and DP from apex-to-base. SP and DP were both detected at the site of successful ablation during SR, whereas during VT, DP was detected away from the earliest activation site. Thus, SP apparently reflected a critical component of the reentrant circuit, while DP reflected the activation of a bystander pathway.

Typical atrial flutter with atypical flutter wave morphology due to abnormal interatrial conduction.

We report a case of typical counterclockwise atrial flutter (AFL) with conduction block from right to left atrium along the coronary sinus (CS) musculature, confirmed by discontinuous CS activation sequence during pacing near the ostium and differential right atrial pacing. AFL was associated with an atypical flutter wave morphology, due to the detour of the activation wavefront from right to left atrium via alternate interatrial electrical connections, such as Bachmann's bundle, the interatrial septum, or both.

Discrimination between His-bundle and the right bundle branch during electrophysiologic studies.

BACKGROUND: The purpose of this study was to identify the His-bundle (HB) versus right bundle branch (RBB) during electrophysiologic studies, using the V3 phenomenon, and to compare the timing of HB versus RBB potentials of sinus cycles (His-ventricular [H-V] interval). METHODS: The study enrolled 16 patients without structural heart disease, who underwent electrophysiologic studies during which the H-V interval was within normal limits and the V3 phenomenon was induced during recordings of the HB and the RBB potentials by a multi-electrode catheter. The recording site of the earliest HB potential just before the V3 phenomenon was defined as the branching portion of His bundle (HBBP), the site immediately proximal to the HBBP as the HB, and the site immediately distal to the HBBP as the RBB. RESULTS: The HBBP was identified in all patients. In all cases but one patient, the H-V interval measured at the HB adjacent to the HBBP was > or =35 ms. However, in 12 patients, the H-V interval measured at the RBB adjacent to the HBBP was also > or =35 ms. CONCLUSIONS: The electrophysiologic identification of HB versus RBB by simultaneous recordings of HB and RBB potentials during induction of the V3 phenomenon was feasible. When the discrimination between HB and RBB was based on the measurement of the H-V interval, the proximal portion of the RBB was frequently misidentified as the HB.