Luigi De Ambroggi

Prospective Assessment of Late Conduction Recurrence Across Radiofrequency Lesions Producing Electrical Disconnection at the Pulmonary Vein Ostium in Patients With Atrial Fibrillation

Background—In patients with atrial fibrillation (AF) undergoing radiofrequency (RF) electrical disconnection of multiple pulmonary veins (PVs), the incidence of late conduction recurrences has not been systematically determined. Methods and Results—Using a prospectively designed, multistep approach, we aimed at assessing the correlation between acute achievement and chronic maintenance of electrical conduction block across RF lesions disconnecting the distal tract of the PV in 43 patients (52.3±8.2 years) with AF. Forty-one left superior (LS), 42 right superior (RS), 25 left inferior (LI), and 9 right inferior (RI) PVs were targeted during 108 EP procedures (2.6±0.5 per patient). Seventeen patients underwent 2 procedures, 23 patients underwent 3 procedures, and 3 patients underwent 4 procedures. During the first attempt, electrical disconnection was achieved in 112 PVs (95.7%). During a next procedure (time interval, 4.6±1.9 months), conduction recurrence was observed in 32 of 39 LSPVs (82.1%), 29 of 40 RSPVs (72.5%), 20 of 24 LIPVs (83.3%), and 7 of 9 RIPV (77.8%). After reablation at gap sites, a later procedure (time interval, 5.1±2.4 months) revealed a second recurrence in 13 of 22 LSPVs (59.1%) and 14 of 19 RSPVs (73.7%). Conclusions—Conduction recurrence across disconnecting RF lesions can be observed in ≈80% of cases 4 months after ablation. After reablation, similar recurrence rates are observed 5 months later. This high rate of late conduction recurrence may contribute significantly to AF recurrence in patients undergoing catheter ablation aiming at disconnection of multiple PVs.

Mapping of Ventricular Repolarization Potentials in Patients With Arrhythmogenic Right Ventricular Dysplasia Principal Component Analysis of the ST-T Waves

BACKGROUND Nonuniform recovery of ventricular excitability has been demonstrated to facilitate the reentry circuits leading to the development of ventricular tachyarrhythmias. This can also occur in arrhythmogenic right ventricular dysplasia (ARVD). In fact, in patients with ARVD, abnormalities of ventricular repolarization are often observed on 12-lead ECGs, but their predictive value for the occurrence of malignant arrhythmias is yet to be established. Because body-surface potential mapping has been proved to be useful for the detection of heterogeneities in ventricular recovery even though they are not revealed by conventional 12-lead ECGs, we attempted to analyze repolarization potentials on the entire chest surface to find abnormalities that can be predictive of ventricular arrhythmias. METHODS AND RESULTS Body-surface potential maps were recorded from 62 anterior and posterior thoracic leads in 22 patients affected by ARVD, 9 with episodes of sustained ventricular tachycardias (VT) and 13 without. Thirty-five healthy subjects were also studied as control subjects. The 62 chest ECGs were simultaneously recorded, digitally converted at a rate of 2000 Hz, and stored on a hard disk of a body-surface mapping computer system. In each subject, the QRST integral map was obtained by calculating at each lead point the algebraic sum of all instantaneous potentials, from the QRS onset to the T-wave end, multiplied by the sampling interval. In most ARVD patients, we observed a larger-than-normal area of negative values on the right anterior thorax. This abnormal pattern could be explained by a delayed repolarization of the right ventricle. Nevertheless, it was not related to the occurrence of VT in our patient population. To detect minor heterogeneities of ventricular repolarization, the principal component analysis was applied to the 62 ST-T waves recorded in each subject. We assumed that a low value of the first or of the first three components (components 1, 2, and 3) indicates a greater-than-normal variety of the ST-T waves, a likely expression of a more complex recovery process. The mean values of the first three components were not significantly different in ARVD patients and control subjects. Nevertheless, considering the two subsets of patients with and without VT, the values of component 1, components 1 + 2, and component 1 + 2 + 3 were significantly lower in the group of ARVD patients with VT. Values of component 1 < 69% (equal to 1 SD below the mean value for control subjects) were found in 6 of 9 VT patients and in 1 patient without VT (sensitivity, 67%; specificity, 92%). A low value of component 1 was the only variable significantly associated with the occurrence of VT. CONCLUSIONS Principal component analysis provides a better quantitative assessment of the complexity of repolarization than other ECG measurements. When applied to ARVD patients, principal component analysis of the ST-T waves recorded from the entire chest surface revealed abnormalities not detected by conventional ECG that can be considered indexes of arrhythmia vulnerability.

Clinical efficacy of ivabradine in patients with inappropriate sinus tachycardia: a prospective, randomized, placebo-controlled, double-blind, crossover evaluation.

OBJECTIVES The purpose of this study was to investigate the role of ivabradine in the treatment of symptomatic inappropriate sinus tachycardia using a double-blind, placebo-controlled, crossover design. BACKGROUND Due to its I(f) blocking properties, ivabradine can selectively attenuate the high discharge rate from sinus node cells, causing inappropriate sinus tachycardia. METHODS Twenty-one patients were randomized to receive placebo (n=10) or ivabradine 5 mg twice daily (n=11) for 6 weeks. After a washout period, patients crossed over for an additional 6 weeks. Each patient underwent symptom evaluation and heart rate assessment at the start and finish of each phase. RESULTS After taking ivabradine, patients reported elimination of >70% of symptoms (relative risk: 0.25; 95% CI: 0.18 to 0.34; p<0.001), with 47% of them experiencing complete elimination. These effects were associated with a significant reduction of heart rate at rest (from 88±11 beats/min to 76±11 beats/min, p=0.011), on standing (from 108±12 beats/min to 92±11 beats/min, p<0.0001), during 24 h (from 88±5 beats/min to 77±9 beats/min, p=0.001), and during effort (from 176±17 beats/min to 158±16 beats/min, p=0.001). Ivabradine administration was also associated with a significant increase in exercise performance. No cardiovascular side effects were observed in any patients while taking ivabradine. CONCLUSIONS In this cohort, ivabradine significantly improved symptoms associated with inappropriate sinus tachycardia and completely eliminated them in approximately half of the patients. These findings suggest that ivabradine may be an important agent for improving symptoms in patients with inappropriate sinus tachycardia.

J wave, QRS slurring, and ST elevation in athletes with cardiac arrest in the absence of heart disease marker of risk or innocent bystander?

Background—QRS-ST changes in the inferior and lateral ECG leads are frequently observed in athletes. Recent studies have suggested a potential arrhythmogenic significance of these findings in the general population. The aim of our study was to investigate whether QRS-ST changes are markers of cardiac arrest (CA) of unexplained cause or sudden death in athletes. Methods and Results—In 21 athletes (mean age, 27 years; 5 women) with cardiac arrest or sudden death, the ECG recorded before or immediately after the clinical event was compared with the ECG of 365 healthy athletes eligible for competitive sport activity. We measured the height of the J wave and ST elevation and searched for the presence of QRS slurring in the terminal portion of QRS. QRS slurring in any lead was present in 28.6% of cases and in 7.6% of control athletes (P=0.006). A J wave and/or QRS slurring without ST elevation in the inferior (II, III, and aVF) and lateral leads (V4 to V6) were more frequently recorded in cases than in control athletes (28.6% versus 7.9%, P=0.007). Among those with cardiac arrest, arrhythmia recurrences did not differ between the subgroups with and without J wave or QRS slurring during a median 36-month follow-up of sport discontinuation. Conclusions—J wave and/or QRS slurring was found more frequently among athletes with cardiac arrest/sudden death than in control athletes. Nevertheless, the presence of this ECG pattern appears not to confer a higher risk for recurrent malignant ventricular arrhythmias.

Illicit drugs and cardiac arrhythmias in athletes.

The current management of athletes with cardiac arrhythmias has become complicated by the widespread use of illicit drugs, which can be arrhythmogenic. The World Anti-Doping Agency annually updates a list of prohibited substances and methods banned by the International Olympic Committee that includes different classes of substances namely, anabolic androgenic steroids, hormones and related substances, β2-agonists, diuretics, stimulants, narcotics, cannabinoids, glucocorticosteroids, alcohol, β-blockers and others. Almost all illicit drugs may cause, through a direct or indirect arrhythmogenic effect, a wide range of cardiac arrhythmias (focal or reentry type, supraventricular and/or ventricular) that can even be lethal and which are frequently sport activity related. A large use of illicit drugs has been documented in competitive athletes, but the arrhythmogenic effect of specific substances is not precisely known. Precipitation of cardiac arrhythmias, particularly in the presence of a latent electrophysiologic substrate including some inherited cardiomyopathies, at risk of sudden death or due to long-term consumption of the substances, should raise the suspicion that illicit drugs may be a possible cause and lead cardiologists to investigate carefully this relationship and appropriately prevent the clinical consequences.

Chest maps of heart potentials in right bundle branch block

Summary Instantaneous distribution of heart potentials on the chest surface at various stages of the cardiac cycle was recorded in subjects whose electrocardiograms revealed signs of complete or incomplete right bundle branch block. The subjects were divided into three groups, according to the behavior of surface potentials during the first half of ventricular activation time. In the final stages of invasion, all the maps showed very similar signs of delayed excitation of the right ventricle. It is likely that the differences seen during the first stages of activation were due at least in part to the variety of ways in which the excitation fronts propagated through the ventricular walls in each group of subjects. As was previously reported for normal subjects, chest maps recorded from patients with right bundle branch block provided more information on the electrical activity of the heart than could be obtained from conventional electrocardiograms. In particular, separate signs of simultaneous left and right ventricular activity, and the overlapping of excitation and recovery potentials could be detected in many cases.

Diagnostic value of body surface potential mapping in old anterior non-Q myocardial infarction☆

Body surface potential maps (BSM) were recorded from 140 chest leads in 30 healthy control subjects (C) and in 20 patients who had had an acute non-Q wave myocardial infarction (MI) 1-82 months before the study, to identify reliable indices of necrosis. In 12 MI patients the QRS complex was within normal limits on standard 12-lead ECG (group A), and in 8 patients no pathologic Q waves were present but the R waves were small and did not normally increase from V1 to V4 (group B). In each subject instantaneous potential distributions throughout the QRS interval were examined. Moreover, the potential--time integrals relating to three intervals (first 40 msec, mid-third, and last third of QRS) were calculated at each lead point and displayed as integral (I) maps. For each time interval, deviation index maps (DI), indicating the standardized differences from normal values, were calculated. An area where the integral values differed at least 2 SD from normal mean was considered abnormal. In most group A patients the inspection of instantaneous potential maps did not reveal definitively abnormal patterns. In group B patients a greater variety of patterns was found and in four cases the characteristic features of the anterior Q wave MI were observed. The DI maps of the first 40 msec of QRS provided the best diagnostic accuracy: areas of negative values 2 SD lower than normal were present in all group B patients (100%), in 8 group A patients (67%), and in 4 group C subjects (13%).(ABSTRACT TRUNCATED AT 250 WORDS)

Body surface potential maps in old inferior myocardial infarction. Assessment of diagnostic criteria

We assessed the accuracy of criteria for diagnosing an inferior myocardial infarction from body potential maps. Body surface potential maps were recorded from 140 lead points on the entire chest surface in three groups of subjects: group A consisted of 15 patients with an old inferior myocardial infarction and typical electrocardiographic signs of necrosis; group B consisted of 15 patients with an old inferior myocardial infarction, but without electrocardiographic signs of necrosis (inferior myocardial infarction was documented during the acute phase); group C consisted of 30 healthy controls. In each subject body surface potential distributions were examined every 2 msec of the QRS complex. Moreover, the potential-time integrals relating to three intervals (QRS, the first 20 and the first 40 msec of the QRS complex) were calculated at each lead point and transferred to diagrams representing the thoracic surface explored (isointegral maps). For each time interval, the mean isointegral map obtained from group C subjects was subtracted from the isointegral map of each patient. The value obtained at each lead point was then divided by the standard deviation of the normal values for that point; the resulting values indicating the standardized differences from normal values were transferred to another map (deviation index isointegral map, DI map). We considered a reliable index of inferior myocardial infarction an area where the time-integral values were at least 2 SD lower than normal, in the inferior half of the thorax. A number of variables relative to instantaneous potential distribution and to isointegral maps were considered. The DI maps of the first 40 msec of QRS gave the most accurate criteria; in fact, an area of negative values 2 SD lower than normal was found in all group A patients and in 11 out of 15 group B patients (sensitivity 100% in group A, 73% in group B and specificity, 83%). Thus our results indicate that body surface potential maps have greater diagnostic information content than the 12 standard electrocardiographic leads and demonstrate the usefulness of the time integral analysis of body surface potentials for diagnostic interpretation.

Current and potential fields generated by two dipoles.

The distribution of currents and potentials in a circular conducting medium surrounding two eccentric dipoles was studied to establish how much information on the number, location, and orientation of the dipoles could be deduced from measurements of potential in the medium at various distances from the generators. When a single, eccentric dipole was active, the curve illustrating the distribution of potentials along the boundary exhibited different kinds of asymmetry, which revealed that the dipole was eccentric and gave some information about its orientation. When both dipoles were active, two maxima and two minima, revealing the presence of two generators, appeared along the boundary when the angle between dipole moments was 150° or more. Along internal circumferences two maxima and two minima appeared at smaller angles between dipole moments and the location of the maxima was closely related to that of the dipole anodes. When the dipoles lay on the same diameter and had opposite polarity, the presence of two generators was clearly detectable from boundary measurements, whereas vector representation was zero. These data improve our understanding of electrical signals recorded from the body surface, whether in the form of electrocardiograms, vectorcardiograms, or equipotential contour maps.

In vivo assessment of coronary stents with 64-row multidetector computed tomography: analysis of metal artifacts.

Objective: To evaluate stent-induced artifacts by 64-row multidetector computed tomography (MDCT). Methods: We studied 26 stented patients with MDCT before conventional coronary angiography (CCA). The CT values were measured. Stents were classified as occluded, with significant stenosis, with nonsignificant stenosis, or patent. For the patent stents, mean in-stent and out-stent CT values were compared; stents 3 mm or smaller were compared with stents larger than 3 mm. Multidetector CT was compared with CCA. Results: We analyzed 42 stents. At CCA, 34 stents were patent, 5 were nonsignificantly stenosed, 1 was significantly stenosed, and 2 were occluded. At MDCT, 33 of 34 patent stents, 2 occluded stents, and 1 stent with significant stenosis were correctly diagnosed; nonsignificant stenoses were undetected, 1 patent stent was misdiagnosed as occluded (&kgr; = 0.727). The out-stent CT value was lower than in-stent CT value both in stents 3 mm or smaller (P = 0.001) and stents larger than 3 mm (P < 0.001). The in-stent CT value of stents 3 mm or smaller was higher (P = 0.011) than that of stents larger than 3 mm. Conclusions: Metal artifacts cause overlooking of nonsignificant stenosis.