Ronald P. Oliver

Use of implantable cardioverter-defibrillators in the congenital long QT syndrome

We surveyed the use of implantable cardioverter-defibrillators in patients with congenital long QT syndrome. The implantable cardioverter-defibrillator was used primarily in high-risk persons and appeared safe and effective over a mean 31-month follow-up.

Optimal electrode position for transvenous defibrillation : a prospective randomized study

OBJECTIVES This study was performed to determine the optimal position for the proximal electrode in a two-electrode transvenous defibrillation system. BACKGROUND Minimizing the energy required to defibrillate the heart has several potential advantages. Despite the increased use of two-electrode transvenous defibrillation systems, the optimal position for the proximal electrode has not been systematically evaluated. METHODS Defibrillation thresholds were determined twice in random sequence in 16 patients undergoing implantation of a two-lead transvenous defibrillation system; once with the proximal electrode at the right atrial-superior vena cava junction (superior vena cava position) and once with the proximal electrode in the left subclavian-innominate vein (innominate vein position). RESULTS The mean (+/- SD) defibrillation threshold with the proximal electrode in the innominate vein position was significantly lower than with the electrode in the superior vena cava position (13.4 +/- 5.7 J vs. 16.3 +/- 6.6 J, p = 0.04). Defibrillation threshold with the proximal electrode in the innominate vein position was lower or equal to that achieved in the superior vena cava position in 75% of patients. In patients with normal heart size (cardiothoracic ratio < or = 0.55), the improvement in defibrillation threshold with the proximal electrode in the innominate vein position was more significant than in patients with an enlarged heart (innominate vein 13.0 +/- 6.5 J vs. superior vena cava 17.9 +/- 5.1 J, p < 0.01). In patients with an enlarged heart, no difference between the two sites was observed (innominate vein 13.9 +/- 4.5 J vs. superior vena cava 13.6 +/- 8.3 J, p = NS). CONCLUSIONS During implantation of a two-lead transvenous defibrillation system, positioning the proximal defibrillation electrode in the subclavian-innominate vein will lower defibrillation energy requirements in the majority of patients.

Analysis of Local Electrogram Characteristics Correlated with Successful Radiofrequency Catheter Ablation of Accessory Atrioventricular Pathways

Due to the limited myocardial lesions produced by radiofrequency current, the ablation of accessory pathways (AP) requires precise localization of such connections. The purpose of this study was to ascertain ivhich characteristicfs) of the local bipolar electrogram, recorded from the ablation and adjacent electrode immediately prior to the application of radio/requency current, correlated with precision in localization adequate to permit AP ablation. Signal analysis was performed for 326 sets of electrograms preceding the attempted ablation of 107 APs in 100 consecutive patients. For 80 antegrade APs, the following variables were evaluated: (1) the presence or absence of an AP potential; (2) the local atrial‐AP interval; (3) the local atrioventricular (AV) interval; and (4) the relationship between the onset of local ventricular depolarization and onset of delta wave of the surface electrocardiogram. For the 27 concealed APs, the following characteristics were evaluated; (1) the presence or absence of an AP potential; and (2) the local VA interval during reciprocating tachycardia or ventricular pacing. Results: Antegrade APs: By statistical analysis, the best correlate of successful ablation of an antegrade AP was a local AV interval < 40 msec (positive predictive value = 94%; 95% confidence intervals (CI) = 81%–100%), Local AV intervals ≤ 50 msec preceded 88% of successful AP ablations, compared to only 8% of failed radiofrequency current applications. The positive predictive value of the other variables were: presence of an AP potential: 35% (95% CI = 27%–40%); local atrial‐AP intervals < 40 msec: 54% (95% CI = 43%‐66%); and local ventricular depolarization preceding onset of the delta wave 43% (95% CI = 34%‐52%). For concealed APs, the positive predictive value of a VA interval < 60 msec was 71% (95% CI = 48%–88%); the positive predictive value for the presence of an AP potential was 58% (95% CI = 32%–81%). Conclusions: No single electrogram characteristic had a positive predictive value and a sensitivity > 90% for AP localization adequate for radiofrequency current ablation. For antegrade APs, the best correlate of adequate localization was a local AV interval < 40 msec; as a corollary, radiofrequency current applications at sites where the local AV was > 60 msec, were unlikely to be effective. Objective criteria for the localization of concealed APs were less certain. Electrogram analysis, as a guide to AP localization and ablation, requires careful analysis of multiple variables, with analysis of the local AV interval a salient objective factor.

Nonautomatic focal atrial tachycardia: characterization and ablation of a poorly understood arrhythmia in 38 patients.

KAMMERAAD, J.A.E., et al.: Nonautomatic Focal Atrial Tachycardia: Characterization and Ablation of a Poorly Understood Arrhythmia in 38 Patients. Nonautomatic focal atrial tachycardia (NAFAT) is a rare and poorly understood arrhythmia either due to microreentry or triggered mechanism. NAFAT was defined as a focal atrial tachycardia which was inducible with pacing maneuvers in the electrophysiology lab. We reviewed the charts and EP study reports of all 38 patients with NAFAT, who underwent an EP study at our center between April 1994 and September 2000. Patients were predominantly female (n = 31, 82%), aged 11–78 years (median 46). The mean age at presentation was 31 years (range 7–71 years). None of the patients had structural heart disease or had undergone prior heart surgery. Electroanatomic mapping (EAM) was performed in 22 patients and showed no scars in the atrium. A total of 45 foci were identified (range 1–3 foci/patient). Anatomically NAFAT foci were predominantly right atrial (n = 35) rather than left (n = 10) . The NAFAT cycle length ranged from 270 to 490 (mean ± SD; 380 ± 69 ms) and was significantly lower in patients younger than 24 years of age. Ablation, attempted for 42 foci was successful in 33 (79%). The success rate in the EAM group was 20/25 foci (80%) compared to 13/18 (72%) in the non‐EAM group. In conclusion, NAFAT is a rare arrhythmia which predominantly affects women with no other associated cardiac disease. It mainly occurs in the right atrium, affects all ages and is amenable to catheter ablation. (PACE 2003; 26:736–742)

Recipient to donor conduction of atrial tachycardia following orthotopic heart transplantation.

We report a case of atrial tachycardia in a 60‐year‐old male 8 years postorthotopic heart transplantation. At electrophysiology study, the clinical rhythm was found to arise from the remnant of the recipient atrium and was successfully terminated by delivery of radiofrequencv energy. Surgical scars formed at the anastomosis of the recipient and donor atrium during the time of orthotopic heart transplantation are thought to electrically isolate the two areas. Although rarely recognized, dysrhythmias originating from the recipient atrial remnant may occur more often than previously thought.

Early Changes in Defibrillation Threshold Following Implantation of a Nonthoracotomy System in Dogs

Background: Nonthoracotomy systems are rapidly becoming the preferred surgical method for implantation of cardioverter defibrillators. Testing is performed at the time of implantation to insure an adequate margin of safety for defibrillation. However, this safety margin may change with lead maturation. This study evaluated changes in defibrillation threshold following implantation of a nonthoracotomy system. Methods and Results: Ten dogs underwent implantation of a nonthoracotomy system consisting of a single catheter with a distal coil electrode in the right ventricular apex and a proximal coil electrode in the superior vena cava forming a common anode with a subcutaneous patch over tbe left tborax. Defibrillation threshold testing, using a biphasic waveform, was performed on each animal under general anesthesia at implantation (day 1) and subsequently on postoperative days 3, 7, 10, 17, 24, 31, 38, and 45. E50, the energy associated with a 50% likelihood of successful defibrillation, was determined at each setting. The mean E50 was 12.2 ± 1.1 J at the time of implantation, increasing 36% to 16.8 ± 2.0 J by day 38 (P < 0.01). Individual increases in E50 of 10–12 J were observed in four animals. Conclusions: Energy requirements for defibrillation with a nonthoracotomy system increase during the early postoperative period, with the highest defibrillation threshold observed at 38 days. This increase may be applicable to humans and should be considered when selecting an adequate energy safety margin for defibrillation at time of implantation.

Anomalous midline common ostium of the left and right inferior pulmonary veins: implications for pulmonary vein isolation in atrial fibrillation.

A 41-year-old man with a history of paroxysmal symptomatic atrial fibrillation refractory to antiarrhythmic drug therapy was referred for pulmonary vein (PV) isolation. Before the procedure, he underwent standard cardiac computed tomographic angiography to evaluate left atrium and PV anatomy, which revealed single right and left superior PVs, each with a moderate-sized ostium. However, the right and left inferior PVs originated from a common and unusually large ostium in the midpostero-inferior left atrium (Figure). Using a double trans-septal approach, an 8-mm tip deflectable ablation catheter and a 20-pole LASSO catheter were inserted …

Apparent Protective Effect of Increased Left Ventricular Wall Thickness in an ICD Population

BACKGROUND Expanding indications for the implantable cardioverter defibrillator (ICD) call for further enhancement of patient selection for optimization of use. Because a subgroup of patients who receive ICDs may not receive therapies, we sought to identify clinical predictors of therapy-free survival in ICD patients. METHODS We performed an analysis of a single-center, 13-year ICD implantation experience (1990-2002). The association between therapy-free survival and several clinical variables was evaluated. RESULTS From a total of 562 patients included in the database, 98 patients (17%) received no shock therapies or antitachycardia pacing (group A). When compared with a randomly selected sample of 131 patients who did receive ICD therapies (group B), there were no significant differences in age, gender, frequency of coronary artery disease, or extent of left ventricular (LV) dysfunction. However, left ventricular hypertrophy (LVH; increased wall thickness by echocardiography) was significantly more common in group A versus group B (30% versus 18%; Pearsons chi-square=4.69, P=.03). The odds of patients in group A having LVH were 1.98 times higher versus group B (95% confidence interval for odds ratio: 1.06-3.71). Comparisons of calculated mean LV mass between the 2 groups were not significantly different (group A 283+/-112 gm versus group B 271+/-108, P=.58). The overall mortality rate was 17% in group A and 22% in group B (P=.29). CONCLUSIONS Increased LV wall thickness was a significant, independent predictor of therapy-free survival in this ICD population. Because LV mass was unchanged, this finding may reflect the importance of LV dilation and wall thinning (ie, eccentric remodeling) as a risk factor for recurrent ventricular arrhythmia in ICD patients.

Design and clinical application of a low-pass input filter for the evaluation of intracardiac electrograms during radiofrequency catheter ablation.

Successful ablation of an accessory pathway using radiofrequency current may be defined by the elimination of ventricular preexcitation or the loss of eccentric retrograde atrial activation.1 Because of the low voltages of intracardiac electrograms (0.1 to 5.0 mV) compared with the high voltages applied during radiofrequency ablation (30 to 50 V), monitoring of local electrograms during ablation may not be feasible with conventional biopotential amplification and filtering systems2. However, given the fundamental differences in signal frequencies between intracardiac electrograms (10 to 230 Hz) and radiofrequency current (550 to 750 KHz), selective attenuation of high-frequency radiofrequency signals and amplification of the lower frequency intracardiac electrograms may allow continuous monitoring of intracardiac electrograms during ablation.3 The purpose of this study was to evaluate the feasibility and clinical use of an input bandpass filter, selective for frequencies < 1 KHz, which allowed continuous monitoring of intracardiac electrograms in patients undergoing radiofrequency catheter ablation of accessory pathways.