Biomedical subjects
Publications and source records attributed to David Keane.
Laser-assisted intracardiac lead extraction is associated with a 1%-2% incidence of pericardial tamponade. Because of this risk, many of these procedures are being performed in an operating room with a cardiac surgeon immediately available. Transesophageal echocardiography is a useful intraoperative monitor during these procedures.
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Although established as the current standard in catheter ablation, radiofrequency energy has significant limitations. To produce a continuous line of conduction block, radiofrequency energy requires contact between the electrode and endocardium throughout and produces a lesion limited in depth and prone to endocardial disruption. As the predominant case mix of catheter ablation shifts from supraventricular tachycardias towards atrial fibrillation and ventricular tachycardia, interest has grown in alternative energy sources. Cryothermy offers the advantages of low risk of endocardial disruption and thrombus formation with extensive previous surgical experience in the treatment of cardiac arrhythmias. Ultrasound and microwave have the advantages of being contact forgiving and having excellent depth of penetration without an apparent higher risk of endocardial disruption than radiofrequency. Diode laser produces controlled low energy ablation and can be delivered through a range of optical fiber configurations including loops and balloons to produce thin continuous lesions. The use of optical fibers for laser delivery also provides an option for reflectance spectroscopy as a feedback mechanism on both contact as well as lesion progression in real time. Each of the above energy sources have potential clinical advantages in epicardial as well as endocardial ablation.
Ectopic beats triggering atrial fibrillation may arise from atrial myocardial extensions in the pulmonary veins, superior vena cava, coronary sinus, and vein of Marshall. We report two patients with paroxysmal atrial fibrillation initiated by ectopic beats originating from the inferior vena cava. The foci responsible for the ectopic beats were located and ablated, resulting in elimination of atrial fibrillation. Ectopic beats originating from the os of the inferior vena cava can result in atrial fibrillation. This finding may explain the recurrence of atrial fibrillation in some patients after pulmonary vein isolation.
Nonpharmacological treatment for atrial fibrillation (AF) has evolved dramatically over the past 20 years. Pulmonary vein isolation, a catheter ablation technique developed in the last decade, prevents focal triggers in the pulmonary veins from initiating episodes of AF. Although the procedure initially involved focal ablation with a catheter directly in the pulmonary veins, investigators subsequently found that isolating the pulmonary veins by applying ablation energy at their junction with the left atrium is more effective. After the procedure is performed once or twice, it is 70% to 80% successful in preventing recurrence of AF episodes in the first year of follow-up. The pulmonary vein isolation procedure is most suitable for patients whose recurring symptomatic episodes of AF have not been suppressed by antiarrhythmic drugs or who do not wish to take long-term antiarrhythmic or anticoagulation medications. The procedure is more successful in patients with intermittent (paroxysmal) AF than in those with long-standing, continuous (chronic) AF.