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Notes: Background: Transseptal (TS) catheterization is used for left atrial (LA) ablation procedures and a major risk is thromboembolism. The purpose of this study was to assess (1) the value of intracardiac ultrasound (ICUS) monitoring during LA ablation procedures, and (2) a new technique to reduce the risk of thrombus formation. Methods and Results: One hundred and eighty consecutive patients underwent TS catheterization under ICUS guidance with two sheaths for atrial fibrillation ablation and one for other LA procedures. Group I included the initial 90 patients in whom TS sheaths were flushed with a standard 2 U/cc concentration of heparin; group II consisted of the next 90 patients in whom sheaths were flushed with 1,000 U/cc concentration. All patients received bolus and infusion of heparin to maintain ACT between 250–300 seconds. ICUS was monitored throughout. In group I, echodense material at the tip of the sheath consistent with thrombus was observed on ICUS in 8 of 90 patients (9%) within 5–15 minutes of entering the LA. In group II, only 1 of 90 patient (1%) demonstrated thrombus (P 〈 0.001). There were no significant clinical differences in group I patients with and without thrombus. In all nine patients, the clot was removed with vigorous aspiration. No patients suffered a neurological event. Conclusion: Thrombus formation on TS sheath, detected by ICUS, may be more common than expected despite adequate anticoagulation. Using a higher concentration of heparin for the TS system before deployment reduced the risk. The thrombus was retrieved with aspiration without the need to abort the procedure.

Notes: Introduction: Atrial fibrillation (AF) is associated with increased ostial pulmonary vein (PV) diameter and commonly with hypertension. We sought to investigate ostial PV anatomy in patients with and without AF with the goal of characterizing the relationship to hypertension and cardiovascular disease. Methods and Results: Ostial PV diameter was assessed by preprocedural spiral computed tomography in 100 AF patients undergoing a PV isolation procedure and in 24 age- and sex-matched non-AF control patients. Ostial diameter of 392 PVs in 100 AF patients was increased compared to 106 PVs in 24 non-AF controls (1.50 ± 0.31 vs 1.20 ± 0.31 cm, P 〈 0.001) and diameters of individual PVs were uniformly affected (r = 0.45–0.62, P 〈 0.001). Left atrial dilation was associated with a larger PV diameter (1.56 ± 0.32 vs 1.44 ± 0.29 cm, P 〈 0.01). PV diameter in AF patients with hypertension (1.55 ± 0.32 cm), particularly if associated with left ventricular hypertrophy (1.66 ± 0.37 cm), was larger compared to AF patients without hypertension (1.43 ± 0.26 cm, P 〈 0.01). PV diameter in control patients with hypertension (n = 14) was larger than in those without hypertension (n = 10, P 〈 0.01). Patients with persistent AF had larger PV diameters (1.61 ± 0.34 cm) than patients with paroxysmal AF (1.47 ± 0.30 cm, P 〈 0.01). Male gender (P 〈 0.01), history of hypertension (P 〈 0.01), and persistent AF (P 〈 0.05) were identified as independent cofactors of increased ostial PV diameter. Conclusion: PV dilation affects all PVs uniformly in AF patients. Hypertension and hypertensive heart disease in patients with and without AF are associated with PV dilation, supporting theories that impaired left ventricular diastolic function is associated with a stretch-induced PV arrhythmia mechanism.

Notes: Unexplained Syncope in AVID. Introduction: A prospective registry and substudy were conducted in the Antiarrhythmics Versus Implantable Defibrillators (AVID) Study to clarify the prognosis and recurrent event rate, risk factors, and impact of implantable cardioverter defibrillator (ICD) therapy in patients with unexplained syncope, structural heart disease, and inducible ventricular tachyarrhythmias. Methods and Results: Included in the AVID registry were patients from all participating sites who had “out of hospital syncope with structural heart disease and EP-inducible VT/VF with symptoms.” In addition, 13 collaborating sites provided more in-depth clinical and electrophysiologic data as part of a formal prospective substudy. Patients in the substudy were followed by local investigators for recurrent arrhythmic events and mortality. Registry patients were tracked for fatal outcomes by the National Death Index. A total of 429 patients with syncope were entered in the AVID registry, of whom 80 participated in the substudy. Of the substudy patients, 21 patients (26%) had inducible polymorphic ventricular tachycardia/ventricular fibrillation (VT/VF), 11 patients (14%) had sustained monomorphic VT 〈 200 beats/min, and 48 patients (60%) had sustained monomorphic VT ≥200 beats/min. The ICD was used as sole therapy in 75% of the syncope substudy patients (and with antiarrhythmic drug in an additional 9%) and in 59% of the syncope registry patients. Survival rates at 1 and 3 years were 93% and 74% for the substudy patients and 90% and 74% for the registry patients, respectively. Survival of the syncope substudy patients (predominantly treated by ICD) was similar to the VT patients treated by ICD and superior to the VT patients treated by an antiarrhythmic drug (P = 0.05) in the randomized main trial. Mortality events in the substudy were marginally predicted by ejection fraction (P = 0.06) but not by electrophysiologic study-induced arrhythmia. The significant predictor of increased mortality in the registry was age (P = 0.003) and of reduced mortality was treatment with ICD (P = 0.006). Conclusion: The results of these analyses support the role of the ICD as primary antiarrhythmic therapy in patients with unexplained syncope, structural heart disease, and inducible VT/VF at electrophysiologic study.

Notes: Background: P wave signal-averaged electrocardiography (PW-SAECG) is a new method that is proving to be an accurate and independent noninvasive marker for the risk of developing atrial fibrillation. This article presents current data acquisition and analysis techniques for PW-SAECG. It also discusses in detail the interplay of inherent challenges present in the morphological attributes of the P wave, and how correct technique can play a large role in surmounting these challenges, thereby producing good results.Methods: Proper patient preparation and correct configuration of instrument settings ensure accurate P wave detection and alignment during the signal-averaging process. This in turn preserves waveform integrity of the resulting signal-averaged P wave data. Subsequent application of appropriate filtering schemes and signal processing methods permit the calculation and analysis of key PW-SAECG time-domain parameters.Conclusions: Judicious modification of established data acquisition protocols from R wave signal averaging, coupled with appropriate postprocessing and analysis techniques, are necessary precursors for arriving at acceptable time-domain PW-SAECG results.

Notes: Background: Atrial fibrillation (AF) is a commonly encountered arrhythmia following cardiac surgery and when sustained, may be associated with significant morbidity.Methods: This large prospective investigation examined a variety of clinical and P wave signal-averaged electrocardiogram (SAECG) parameters to identify independent predictors of AF following cardiac surgery. A total of 272 patients underwent P wave SAECG recording and analysis prior to surgery. Information on their clinical, surgical, and hemodynamic characteristics as well as hospital course was collected. Patients were followed during their postoperative course with telemetry and ECGs.Results: During an observation period of up to 14 days, 79 patients (29%) developed AF 2.5 ± 1.9 days after surgery. Patients who developed AF following cardiac surgery were more likely to be older, undergo valve surgery, to have ejection fraction (EF) 〈 40%, to have P wave duration on SAECG 〉140 ms (all P 〈 0.01), and to take digoxin preoperatively (P 〈 0.05). A multivariate analysis found that only P wave duration on SAECG 〉140 ms and EF 〈 40% were independent predictors of AF following cardiac surgery. The odds ratio of P wave duration on SAECG 〉140 ms and EF 〈 40% for the development of AF following cardiac surgery was 3.1 and 2.8, respectively, and 8.7 when combined.Conclusions: Thus, the presence of preexisting abnormal atrial substrate as detected by P wave prolongation on SAECG, and implicated by EF 〈 40%, clearly predicted a higher risk of AF following cardiac surgery and may provide clinicians with an effective means of identifying those at greatest risk.

Notes: BackgroundAtrial fibrillation is the most common arrhythmia encountered in clinical practice. Identification of factors predisposing to atrial fibrillation may have implications for its prevention and may facilitate the detection of patients most susceptible to atrial fibrillation and its sequelae. Prolongation of P wave duration representing intra-atrial conduction delay is inadequately visualized in a standard electrocardiogram. Accurate detection, alignment, amplification and filtering of P waves during the signal averaging process permits a better analysis of the P wave and thus atrial conduction. Signal averaged P wave electrocardiography is a noninvasive technique that has permitted the evaluation of patients at risk of developing atrial fibrillation. Several studies have correlated the abnormalities in signal averaged P wave with paroxysmal atrial fibrillation, and have demonstrated its utility in independently predicting patients at risk of developing atrial fibrillation following cardiac surgery. New uses are likely to evolve as the technique is used clinically and as the methodology is standardized. A.N.E. 1999;4(4):401–407

Notes: Background: The effect of Ml on the high frequency content of the QRS complex in the SAECG remains a matter of controversy. The purpose of this study was (1) to characterize the changes in the high frequency QRS energy that occur after experimental Ml in dogs, (2) to evaluate the change in QRS energy in a number of frequency bandwidths, and (3) to evaluate the relationship between the change in QRS energy and infarct size and location, as well as the inducibility of VT.Methods: MIs were created in 21 dogs by balloon occlusion of the left circumflex (n = 10) or left anterior descending (n = 11) coronary arteries. SAECGs, using three orthogonal leads (X, Y, Z), were obtained before and 4–6 days after the Ml. The vector magnitude was calculated. Using a spectral filter, we calculated the energy in û Vs) of the entire QRS as the integrated area of the signal voltage within a low frequency bandwidth (15–40Hz) and two high frequency bandwidths (40–80 Hz, 80–300 Hz). QRS energy was log transformed to achieve a normal distribution.Results: There was a significant decrease in QRS energy after Ml in the low and high frequency bandwidths in the 21 dogs that was primarily detected in the Y lead. This decrease in high frequency energy after Ml occurred primarily in the dogs with anterior infarction where there was a 13–21% drop in QRS energy in all three bandwidths in the vector magnitude as well as the Y and Z leads (all P 〉 0.05). This drop in QRS energy after anterior wall Ml was moderately correlated with increasing infarct size in all three bandwidths. There were no consistent changes in QRS energy in the dogs with posterior infarction. The drop in QRS energy after Ml was not associated with inducible VT. The change in QRS energy after Ml in all three bandwidths were highly correlated.Conclusions: The process of Ml produced a decrease in QRS energy, in both low and high frequency bandwidths, that was most consistent in dogs with anterior wall Ml. The decrease in QRS energy after Ml was not associated with inducible VT. Ml produced similar changes in QRS energy in low and high frequency bandwidths. A.N.E. 1999;4(1):72–82

Notes: Background: We have previously demonstrated that high frequency QRS energy decreases after experimental myocardial infarction (Ml) and is lower in patients who have had MI compared to controls. The mechanism for this decrease in high frequency QRS energy is unclear. The objective of this study was to evaluate the effect of slowed myocardial conduction on high frequency QRS energy measured on the signal-averaged SAECG. We hypothesized that slowed conduction in the infarcted ventricle may be responsible for the decrease in high frequency QRS energy. In order to test this hypothesis, we examined antiarrhythmic drug therapy known to slow conduction (propafenone) compared to drug therapy with minimal effects on conduction (sotalol).Methods: In patients with sustained ventricular tachyarrhythmias undergoing serial drug testing, SAECGs were obtained before and after antiarrhythmic therapy. After filtering the leads with a spectral band-pass (15–40 Hz, 40–80 Hz, and 80–300 Hz) filter, the vector magnitude was con structed, and the energy (in μV sec) was calculated for the entire QRS by integrating the area under the filtered QRS complex.Results: Propafenone significantly prolonged QRS duration (+17%, P 〉 0.001) and significantly reduced QRS energy (-16.1% to 21.8%, P 〉 0.0001) in all three band widths. Sotalol did not have either effect (P = ns). There was a strong correlation between the prolongation of the filtered QRS and the drop in QRS energy for all three band widths (r values ranging from 0.64–0.90, all P 〉 0.05). When the changes in QRS energy were corrected for QRS duration, the results did not change.Conclusion: The Class IC antiarrhythmic drug propafenone, known to decrease myocardial conduction velocity, significantly reduced QRS energy in all three band widths, whereas the Class III drug sotalol did not. These data are consistent with the hypothesis that decreases in low and high frequency QRS energy after Ml result in part from slowed conduction.

Notes: Chest CT and Amiodarone Pulmonary Toxicity. Introduction: Amiodarone pulmonary toxicity is a serious adverse effect that can be fatal. The diagnosis is difficult due to the nonspecificity of symptoms, clinical findings, and test results. Because of its high iodine content, amiodarone deposition can be detected by sensitive high-resolution computed tomographic (CT) scan techniques. We hypothesized that pulmonary toxicity can be diagnosed more readily when these scans indicate the presence of increased attenuation of either pleural or pulmonary densities representing high iodine amiodarone deposits. Methods and Results: This case control study included 16 patients taking chronic amiodarone. Eight cases presented with severe respiratory and other symptoms and were matched with 8 controls, 4 with mild or chronic respiratory symptoms. All patients underwent high-resolution CT of the chest. All cases had positive CT scan results demonstrating bilateral air-space disease, parenchymal bands, and thickened septal and bronchiolitis obliterans. All minimally or asymptomatic patients had negative scans with no area of high attenuation. All cases had ≤ 1 lesion with high-attenuation density. The cases were treated successfully by supportive care, discontinuation of amiodarone, and, rarely, corticosteroid therapy. Two cases had delayed diagnosis of amiodarone pulmonary toxicity and were managed successfully only ter CT. Conclusion: High-resolution CT may be a valuable noninvasive test to aid in the diagnosis of amiodarone pulmonary toxicity in symptomatic patients.