Conduction Velocity in the Tricuspid Valve-Inferior Vena Cava Isthmus is Slower in Patients With Type I Atrial Flutter Compared to Those Without a History of Atrial Flutter

Slower Conduction in the TV-IVC Isthmus. Introduction : In human type I atrial flutter, the electrophysiologic substrate is unclear. In order to determine if slow conduction is mechanistically important, we evaluated conduction velocity in the tricuspid valve-inferior vena cava (TV-IVC) isthmus, right atriai free wall, and interatrial septum in patients with and without a history of atrial flutter undergoing electrophysiologic study.
Methods and Results : Nine patients with (group 1) and nine without a history of type I atrial flutter (group 2) were studied. Conduction time (msec) in the right atrial free wall. TV-IVC isthmus (bidirectional), and interatrial septum was measured during pacing in sinus rhythm at cycle lengths of 600, 500, 400, and 300 msec from the low lateral right atrium and coronary sinus ostium. Conduction velocity (cm/sec) was calculated by dividing the distance between pacing electrodes and sensing electrodes (cm) by the conduction time (sec). Conduction velocity was slower in the TV-IVC isthmus in group 1 (range 37 ± 8 to 42 ± 8 cm/sec) versus group 2 (range 50 ± 8 to 55 ± 9 msec) at all pacing cycle lengths (P < 0.05). However, conduction velocity was not different in the right atrial free wall or interatrial septum between groups 1 and 2. Conduction velocity was also slower in the TV-IVC isthmus than in the right atrial free wall and interatrial septum in group 1 patients, at all pacing cycle lengths (P < 0.05). Atrial flutter cycle length correlated with total atrial conduction time (r ≥ 0.832, P < 0.05).
Conclusion : Slow conduction in the TV-IVC isthmus may be mechanistically important for the development of human type I atrial flutter.     

Ventricular Fibrillation with Prominent Early Repolarization Associated with a Rare Variant of KCNJ8/KATP Channel

Background: Early repolarization in the inferolateral leads has been recently recognized as a frequent syndrome associated with idiopathic ventricular fibrillation (VF). We report the case of a patient presenting dramatic changes in the ECG in association with recurrent VF in whom a novel genetic variant has been identified.
Case Report: This young female (14 years) was resuscitated in 2001 following an episode of sudden death due to VF. All examinations including coronary angiogram with ergonovine injection, MRI, and flecainide or isoproterenol infusion were normal. The patient had multiple (>100) recurrences of VF unresponsive to beta-blockers, lidocaine/mexiletine, verapamil, and amiodarone. Recurrences of VF were associated with massive accentuation of the early repolarization pattern at times mimicking acute myocardial ischemia. Coronary angiography during an episode with 1.2 mV J/ST elevation was normal. Isoproterenol infusion acutely suppressed electrical storms, while quinidine eliminated all recurrences of VF and restored a normal ECG over a follow-up of 65 months. Genomic DNA sequencing of K_ATP channel genes showed missense variant in exon 3 (NC_000012) of the KCNJ8 gene, a subunit of the K_ATP channel, conferring predisposition to dramatic repolarization changes and ventricular vulnerability.     

The Dynamic Behavior of the Diastolic Slope of Monophasic Action Potential Can be Related to the Occurrence and Maintenance of Delayed Afterdepolarization Dependent Arrhythmias

We have described the value of the diastolic slope of the MAP recording at the end of a pacing train as a qualifying marker for the induction of delayed afterdepolarization (DAD) dependent arrhythmias. In the present study (1) the behavior of the slope at different time points during a pacing train was quantified and related to the arrhythmogenic outcome (group A) and (2) termination of DAD dependent VT was related to changes in the slope steepness (group B). In dogs with chronic complete AV block, a MAP was recorded during (1) ventricular pacing, before and after ouabain administration (group A) and (2) 6 spontaneous and 6 lidocaine induced VT terminations (group B). During control (group A), the slope at the end of pacing train was 5 ± 3 mV/s (mean ± SD), independent of the pacing duration. During ouabain, this increased to 20 ± 15 mV/s (P < 0.05), varying with the duration of pacing. The slope was steeper after pacing for 4 seconds, compared to 20 seconds (26 ± 12 mV/s vs 16 ± 13 mV/s, P < 0.05) which corresponded with more frequent VT induction. In spontaneously terminating VTs (group B), CL increased from 353 ± 54 ms at the start to 434 ± 78 ms (P < 0.05) before VT termination. This corresponded with a decreasing steepness of the slope from 19 ± 10 mV/s to 6 ± 5 mV/s (P < 0.05). In lidocaine induced VT termination, the CL and the steepness of the slope showed an identical behavior. There is a dynamic variation in the steepness of the diastolic slope during pacing, which depends on the duration of pacing and predicts arrhythmogenic outcome. Furthermore, a decrease in steepness of the slope during DAD dependent VT can be used to predict VT termination.     

The Self-Rating of the Effects of Alcohol (SRE) form as a retrospective measure of the risk for alcoholism

Aims. A low level of response (LR) to alcohol is a characteristic of sons of alcoholics and predicts an elevated future alcoholism risk. A 12-question Self-Rating of the Effects (SRE) of alcohol form has been shown to correlate cross-sectionally with a designation of a low LR determined by alcohol challenges. Design. his study evaluates the potential usefulness of the SRE as a retrospective measure of both the response to alcohol and of subsequent alcoholism in two samples. Setting. All subjects were studied in the United States, most in California. Participants. First, 94 sons of alcoholics and controls completed the SRE 15 years after an alcohol challenge, and SRE values were compared to their prior LR results and their alcoholic outcomes. Secondly, the relationship between SRE results and alcoholic status was determined in 551 men and women alcoholics, their relatives, and controls. Measurements. Subjects were evaluated with face-to-face interviews. Findings. Despite the interval of 15 years, the correlation between the SRE and the subjective high feelings on the alcohol challenge was between -0.3 and -0.4. For those 94 subjects the full SRE correlated with a diagnosis of alcohol dependence at 0.5, a figure that remained at 0.3 even when only the estimates related to the earliest drinking experiences were considered. For the 551 men and women, the correlation between the SRE and alcohol dependence diagnoses was 0.6, including 0.3 for the estimates of the first five times of drinking. All major findings in both samples remained robust when the recent drinking history or the number of items endorsed was considered, or when the most severe alcohol problem, passing out, was deleted from the analysis. Conclusions. When alcohol challenges are not possible, these retrospective reports indicate that the SRE is a potentially useful surrogate for determining a subgroup of people who might carry a low level of response to alcohol and a subsequent elevated risk for alcoholism.     

Down to the Wire: Tricuspid Stenosis in the Setting of Multiple Pacing Leads

Tricuspid stenosis in the setting of endocardial pacing leads is a rare entity, attributed to infection or lead malposition. We report the case of a 37‐year‐old man without these risk factors, who presented with new onset severe tricuspid stenosis in the setting of multiple chronic pacing leads. (PACE 2010; e49–e52)     

Echocardiographic Assessment of the Interventricular Delay of Activation and Correlation to the QRS Width in Dilated Cardiomyopathy

The aim of the study was to define criteria for left ventricular pacing in dilated cardiomyopathy (DCM) using an echocardiographic evaluation of interventricular electromechanical delay (IMD) and a correlation of IMD to QRS duration. Standard 12-lead ECG and echocardiography with pulsed Doppler tissue imaging (DTI) were recorded in 35 DCM patients (mean age 58 +/- 11 years) with QRS duration from narrow (80 ms) to broad (222 ms) patterns. The timefor left ventricular activation was evaluated from the onset of QRS to the onset of aortic flow (Q-Ao) by standard pulsed Doppler (SP) or to the onset of mitral annulus systolic wave (Q-Mit) (DTI). The time for right ventricular activation was determinedfrom the onset of QRS to the onset of pulmonary flow (Q-Pulm) (SP) or to the onset of tricuspid annulus systolic wave (Q-Tri) (DTI). (Q-Ao)-(Q-Pulm) and (Q-Mit)-(Q-Tri) determined IMD for each method, respectively. QRS width and IMD showed correlation coefficients of r = 0.86 ([Q-Ao]-[Q-Pulm]) and r = 0.82 ([Q-Mit]-[Q-Tri]) (P < or = 0.001 ). Mean IMD of 77 +/- 15 ms (SP) and 88 +/- 26 ms (DTI) were noted for QRS width above 150 ms. Left ventricle delayed activation was positively correlated to QRS widening with both methods, (r = 0.90, [Q-Ao]), (r = 0.83, [Q-Mit]) (P < or = 0.001). In conclusion, QRS duration is a good marker of an interventricular mechanical asynchrony. According to IMD correction, left ventricular pacing may be mainly proposed to symptomatic DCM patients with QRS duration > 150 ms.