Toru Iwa

Time- and Frequency-Domain Analyses of the Signal-Averaged ECG in Patients With Arrhythmogenic Right Ventricular Dysplasia

BACKGROUND Arrhythmogenic right ventricular dysplasia (ARVD) is characterized by recurrent ventricular tachycardia of right ventricular origin and a cardiomyopathy with hypokinetic areas involving the free wall of the right ventricle. Subjects have a risk of sudden cardiac death, particularly during sports and strenuous exercise. Routine clinical examinations may be normal, but fragmented or delayed electrograms are usually recorded in the right ventricle of these patients. However, the frequency with which late potentials are detected by conventional time-domain analysis of the signal-averaged ECG (SAECG) is not high. This study evaluated the usefulness of the frequency-domain analysis of the SAECG in addition to the conventional time-domain analysis for a screening test to detect patients with ARVD. METHODS AND RESULTS SAECG was recorded by using a bipolar X, Y, and Z lead system in 28 patients with ARVD (mean age, 38 +/- 13 years) and 35 age-matched normal subjects (mean age, 35 +/- 11 years). The conventional time-domain analysis of the SAECG was performed at two different high-pass filter settings, 25 and 40 Hz, and the low-pass cutoff frequency was fixed at 250 Hz. The fast-Fourier transform analysis of SAECG was performed using a Blackman-Harris window. Area ratio 1 (area of 20 to 50 Hz)/(area of 0 to 20 Hz) and area ratio 2 (area of 40 to 100 Hz)/(area of 0 to 40 Hz) were calculated. In the conventional time-domain analysis, 20 (71%) and 18 (64%) patients had positive criteria at filter settings of 25 and 40 Hz, respectively. In the frequency-domain analysis, 18 (64%) and 20 (71%) patients had abnormal values in area ratios 1 and 2, respectively. Combining the time- and frequency-domain analyses, all patients were judged positive, with a sensitivity of 100% and a specificity of 94%. CONCLUSIONS Each result of the time- and frequency-domain analyses revealed that both methods had equivalent value. Combining the two domain analyses improved the sensitivity without reducing the specificity. These findings suggest that combining the time- and frequency-domain analyses of the SAECG may be useful as a screening test to detect patients with ARVD.

Frequency of supraventricular tachyarrhythmias in arrhythmogenic right ventricular dysplasia

Abstract The incidence of supraventricular tachyarrhythmias in patients with arrhythmogenic right ventricular dysplasia (ARVD) is unknown. 1–5 We report on 72 consecutive patients with the diagnosis of ARVD studied at Jean Rostand Hospital.

Arrhythmias in Centenarians

Background: Many studies have shown an increase in the prevalence of arrhythmias with advancing age. However, little is known about arrhythmias in centenarians. Method and Results: Thirty‐two Japanese centenarians aged 100–106 years (14 males, 18 females) were studied. All of them had 12‐lead EGGs, and 22 also had 24‐hour ambulatory monitoring. As controls, 89 healthy Japanese elderly from the same geographic area underwent 12‐lead ECG. Their mean age was 75 ± 6 years with a range of 63–93 years, and there were 28 males and 61 females. Twenty‐three of them also had Holter ECGs. On the 12‐lead ECG, the heart rate was slightly, but significantly, higher in the centenarians (76.8 ± 12.7 beats/min) than that in the elderly subjects (74.9 ± 5.9 beats/min, P < 0.005). PQ and QTC were significantly longer in the centenarians (174 ± 29 and 439 ± 33 msec, respectively) compared with the elderly subjects (158 ± 23 and 417 ± 31 msec, P < 0.005 and P < 0.001, respectively). Supraventricular premature beats (SVPBs) were observed in 31% of the centenarians and in 4% of the elderly subjects (P < 0.001). First‐ and second‐degree AV block was recorded in 25% of the centenarians and 1% of the elderly subjects (P < 0.001). Right bundle branch block was found in 19% of the centenarians and 7% of the elderly subjects (P < 0.05). There were no differences in the frequency of ventricular premature beats (VPBs) or QRS voltage. On the Holter ECG, there were no significant differences in average heart rate, maximum heart rate, minimum heart rate, or the longest RR interval. A subgroup of centenarians had frequent SVPBs. However, none of them had > 1,000 VPBs/day as opposed to four elderly subjects (P < 0.01). Atrial fibrillation was not observed in any records of the centenarians despite the presence of frequent SVPBs. Conclusion: These data suggest that conduction disturbances of the AV nodal—His‐Purkinje system and frequent SVPBs are common in centenarians, whereas very frequent VPBs and atrial fibrillation seem less common.

Role of Na+‐H+ Exchange on Reperfusion Related Myocardial Injury and Arrhythmias in an Open‐Chest Swine Model

The inhibition of Na+‐H+ exchange (NHE) with amiloride analogues in vitro has been shown to prevent reperfusion arrhythmias and additional cell necrosis. Inhibition of intracellular Ca2+ overload via NHE inhibition has been suggested as a mechanism of these protective effects. The aim of this study was to examine whether treatment with amiloride analogues reduces the incidence of reperfusion arrhythmias and limits infarct size in vivo. Open‐chest swine were exposed to a 30‐minute left anterior descending artery (LAD) occlusion and 180 minutes of reperfusion during atrial pacing at 150 ppm. Intravenous 5‐(N,N‐dimethyI)‐amiloride (AML, 5 μg/kg per min) was administered in the treatment group (n = 7) and intravenous saline in the control group (n = 7), starting 10 minutes before coronary occlusion. The infusion was continued during ischemia and reperfusion. The area at risk was defined by monastral blue dye and infarct size by triphenyltetrazolium chloride staining. Limb leads ECG and monophasic action potentials (MAPs) from the epicardium in the ischemic area were recorded. There was no significant difference in the size of the area at risk and hemodynamic parameters between the groups. However, the infarcted area was 0.4%± 1.0% of the area at risk in the treatment group, whereas it was 62%± 29% in the control group (P < 0.05). Pathological examination (Hematoxylin‐eosin and mallory s phosphotungstic acid‐hematoxylin staining) revealed that all of the infarcted area consisted of contraction band necrosis. MAP duration in both groups was significantly shortened during ischemia. After reperfusion, MAP duration in the treatment group recovered earlier than that of control group. However, there was no significant difference in the incidence of ventricular tachyarrhythmia between the groups. Inhibition of NHE with AML prevented reperfusion related cell necrosis in the in vivo swine model, but did not reduce the incidence of ventricular tachyarrhythmia.

Optimal High-Pass Filter Settings of the Signal-Averaged Electrocardiogram in Patients with Arrhythmogenic Right Ventricular Dysplasia

Signal-averaged electrocardiography has been used to detect late potentials in patients at risk of sustained ventricular tachycardia.t The reported prevalence of abnormal signals has ranged from 60% to 90% in patients with previously documented episodes of chronic sustained ventricular tachycardia after myocardial infarction. High-pass filter settings at 25 or 40 Hz are usually selected, although different high-pass filters can significantly change the criteria for identifying late potentials. The effect of the high-pass filter for signal averaging of the surface QRS complex to detect late potentials was assessed by Gomes2 and Carets and their associates. However, these studies depend on the data from patients with ventricular tachycardia who had coronary artery disease or idiopathic dilated cardiomyopathy. There are no widely accepted guidelines for the optimal high-pass filter settings in patients with arrhythmogenic right ventricular dysplasia (ARVD), who had ventricular tachycardia originating from the right ventricle, and had normal left ventricular function. The purpose of this study was to establish the optimal high-pass filter settings for the signal-averaged electrocardiogram (ECG) in patients with ARVD. The signal-averaged ECG was recorded in 30 patients (20 men and 10 women, mean age 37.8 f 13.3 years) with ARVD, who had clinically sustained ventricular tachycardia. Diagnosis of ARVD was achieved by ECGs during ventricular tachycardia and sinus rhythm, echocardiograms, right and left ventricular angiograms, and electrophysiologic studies. QRS morphologies during ventricular tachycardias were left bundle branch block pattern, and the origins of ventricular tachycardia were right ventricle in all. Patients with From the Center de Stimulation Cardiaque et de Rythmologie, HBpital Jean Rostand, Ivry-Sur-Seine, Ivry, France. Dr. Kinoshita’s address is: HBpital Jean Rostand, 39-41, rue Jean Le Galleu, 94200 Ivry&u-Seine,

Better Predictors of Successful His‐Bundle Ablation Analysis of First Shocks

IWA, T., ET AL.: Better Predictors of Successful His‐Bundle Ablation Analysis of First Shocks. We have reported here that a longer HV interval in asssociation with a larger His amplitude yields a high rate of success when used to position the ablating catheter for His‐bundle ablation. Additionally, we have shown that double discharge shocks are more effective than single discharge shocks, and that negative polarity is more effective than positive polarity. The use of bipolar or tripolar, and not quadripolar catheters, was also associated with a higher success rate. In our institution, using a bipolar catheter, we attempt to record an HV interval > 55 msec and a His amplitude > 0.35 mV. When both of these criteria are fulfilled, we use 3 to 4 joules per kg, and a single discharge shock. When one or the other of these criteria are not fulfilled, we use the double discharge shock method. Using these techniques, we have achieved successful His‐bundle ablation with only one shock in all but one of the most recent 21 consecutive patients.

The Prognosis of Patients who Received Automated External Defibrillator Treatment in Hospital

Introduction: Unlike cardiac arrest occurring out‐of‐hospital, the safety and efficacy of automated external defibrillators (AED) in the hospital has not been assessed. This study examined the conditions of AED use in hospital and the prognosis of these patients.

Use of Catheter Ablation in the Treatment of Ventricular Tachycardia Triggered by Premature Ventricular Contraction

A 50‐year‐old man who had suffered from old myocardial infarction presented with an episode of syncope. DC shock was required for the interruption of frequent pleomorphic ventricular tachycardia (VT). Although the treatment for heart failure decreased the frequency of VT attacks, hemodynamically unstable VT occurred several times. A 12‐lead Holter electrocardiogram was used to determine the triggering premature ventricular contraction (PVC) and catheter ablation was performed by targeting this PVC. The site of origin of the triggering PVC was considered to be located between damaged cardiac muscle and intact Purkinjes fiber. No episode of PVC and VT was observed after a few days of ablation. An implantable cardioverter defibrillator was implanted but VT did not recur for more than 20 months.

Concealed WPW Syndrome with Longitudinal Dissociation in the His Bundle Exhibiting Five Different Electrocardiographic Waveforms During Tachycardia

We examined a patient with concealed WPW syndrome who exhibited five different electrocardiographic waveforms during tachycardia.

Factors Predicting Success in DC Catheter Ablation of Accessory Pathways

In a series of 33 patients with accessory pathways, 26 had successful catheter ablation (fulguration [23 patients] or modification [3 patients]) of their accessory pathway conduction, and could be considered as a clinical success. One hundred thirteen single discharge or double discharge shocks were delivered, and each shock was studied to reveal which parameters were important to predict the success or failure of catheter ablation. Double discharge shocks resulted in successful accessory pathway modification or ablation twice as often as single discharge shocks (32% vs 16%). This effect was more pronounced in left lateral accessory pathways (48% vs 4%). Shocks in the electro physiologically defined ventricular zone were more likely to be successful (33%) than shocks delivered in the atrial zone (14%), irrespective of accessory pathway location. The presence of a probable Kent potential was the parameter most strongly associated with success. The parameter most strongly associated with failure, with a 100% negative predictive value, was the absence of earliest activation recorded on the ablating catheter prior to shock delivery. An AV interval of < 60 msec significantly divided the successful from the unsuccessful shocks (P = 0.01). The VA interval during orthodromic reciprocating tachycardia or right ventricular stimulation did not allow for significant division into successful and unsuccessful attempts in this relatively short series. VA intervals, when longer, were predictive of failure but, when shorter, had low positive predictive value. Mean follow‐up in 25 successful patients was 15 ± 6 months. All patients did well in the followup period. Neither those patients with ablation nor modification of the accessory pathway had recurrent episodes of tachycardia or required pharmacological treatment for control of arrhythmias.