A simple electrocardiographic algorithm for detecting ventricular tachycardia.

The purpose of this study was to determine whether a simple ECG algorithm could be developed for predicting susceptibility to ventricular tachyarrhythmias (VT) as defined by sustained spontaneous or inducible VT. Two different QT dispersion algorithms were determined by the difference between the longest and shortest QT interval measured in three orthogonal leads (I, aVF, V1; QTD3), and at least 11 of 12 leads (QTD12) from the 12-lead ECG. These QT dispersion algorithms were investigated (with and without the QRS duration from the 12-lead ECG) and compared to the signal-averaged ECG (SAECG) in order to determine their sensitivity and specificity for detecting VT. Only patients who underwent SAECG and were referred for programmed electrical stimulation were included in this study. A positive SAECG was defined by filtered QRS duration > 114 ms, and/or low amplitude signal duration > 38 ms, and/or root mean square voltage in the last 40 ms of < 20 microV. Sixty patients were enrolled in this study with a mean age of 63 +/- 2 years. Fifty-five percent of the patients had coronary artery disease. A simple ECG algorithm consisting of the sum of QTD3 plus the QRS duration had a sensitivity and specificity of 90% and 63%, respectively, wheras the SAECG had a sensitivity and specificity of 60% and 63%, respectively (P = 0.022). We conclude that a simple ECG algorithm is more sensitive than the SAECG for predicting VT. This algorithm combines two easily measured variables obtained from the 12-lead ECG, and can easily be performed without expensive computer equipment.

Radiofrequency catheter ablation as primary therapy for supraventricular tachycardia.

BACKGROUND: Initial management of patients with supraventricular tachycardias has traditionally been with medications. More recently, radiofrequency catheter ablation offers curative therapy thus obviating the need for medications with potential side effects. The purpose of this study was to evaluate radiofrequency catheter ablation as an initial strategy to cure supraventricular tachycardias. METHODS: Radiofrequency catheter ablation was attempted as the initial therapy in 49 patients with supraventricular tachycardia, 25 with atrioventricular nodal reentrant tachycardia, 20 with atrioventricular reentrant tachycardia, two with both atrioventricular nodal reentrant tachycardia and atrioventricular reentrant tachycardia, and two with atrial tachycardia. RESULTS: Supraventricular tachycardia was rendered non-inducible in 48 of 49 (98%) patients undergoing radiofrequency catheter ablation. Thirteen of 14 patients returning for follow-up electrophysiologic study at 4.9 +/- 2.2 months had no evidence of recurrence. Three patients experienced documented recurrences of supraventricular tachycardia. One of these three patient's supraventricular tachycardia was rendered non-inducible after a final ablation session, and has had no recurrence after 24 months. The other two patients await repeat ablation. Two patients required treatment for atrial fibrillation which was documented prior to ablation. There were no complications or mortality from the procedure. CONCLUSIONS: Radiofrequency catheter ablation should be considered as first line therapy for symptomatic supraventricular tachycardia.

Clinical experience with transvenous implantable cardioverter-defibrillators for treatment of malignant ventricular arrhythmias.

The need for thoracotomy has previously limited the use of the implantable cardioverter-defibrillator. Prior investigators have shown the efficacy and reduced risk of the transvenous implantable cardioverter-defibrillator. In this study, we report our experience with the transvenous implantable cardioverter-defibrillator as a first-line system. Thirty-four patients with mean age 63.2 +/- 10.3 years and mean ejection fraction 32.6 +/- 11.4% underwent implantation of a transvenous cardioverter-defibrillator using an Endotak lead with or without a subcutaneous patch. Twenty-one patients received a biphasic device and the remainder a monophasic device. Thirty-three of 34 patients (97%) were successfully implanted. The mean defibrillation threshold was than < or = 15.3 +/- 3.6J. Overall, 25 of 34 (74%) patients were implanted with a single endocardial lead alone. In the group receiving a biphasic device 19 of 21 (90%) were successfully implanted with a single endocardial lead alone whereas in the group receiving a monophasic device only 6 of 12 (50%) were successfully implanted with single endocardial lead alone (p < 0.05). There were no serious complications. One postoperative death was a result of end-staged congestive heart failure. We conclude that the transvenous implantable cardioverter-defibrillator is safe and efficacious and that incorporation of biphasic waveform may lead to higher rates of implantation of single transvenous lead alone without the need for subcutaneous patch.

Right ventricular outflow tract ventricular tachycardia: detection of previously unrecognized anatomic abnormalities using cine magnetic resonance imaging.

OBJECTIVES: This study attempted to determine whether cine magnetic resonance imaging (MRI), because of its unique ability to image the right ventricle, detects abnormalities in patients with right ventricular outflow tract ventricular tachycardia. BACKGROUND: Right ventricular outflow tract ventricular tachycardia occurs in the absence of apparent structural heart disease. METHODS: We compared cine MRI scans in 22 patients with right ventricular outflow tract ventricular tachycardia, 16 subjects without structural heart disease and 44 patients with other cardiovascular diseases. Echocardiography was performed in 21 patients with ventricular tachycardia. RESULTS: All 22 patients with ventricular tachycardia had normal left ventricular function and no evidence of coronary artery disease. Cine MRI revealed right ventricular structural and wall motion abnormalities more often in patients with ventricular tachycardia (21 [95%] of 22) than in normal subjects (2 [12.5%] of 16, p < 0.0001) or patients without arrhythmia (17 [39%] of 44, p < 0.0001). The abnormalities in patients with ventricular tachycardia (fixed focal wall thinning, excavation, decreased systolic thickening) were located in the right ventricular outflow tract, whereas those in patients without arrhythmia were confined to the free wall. Cine MRI demonstrated abnormalities in patients with ventricular tachycardia more often than did echocardiography (21 [95%] of 22 vs. 2 [9%] of 21, respectively, p < 0.0001). CONCLUSIONS: Right ventricular outflow tract ventricular tachycardia was associated with focal structural and wall motion abnormalities of the right ventricular outflow tract that were detected more often by cine MRI than by other imaging modalities and were not present in patients without arrhythmia or in normal subjects.