Intra-atrial conduction block along the mitral valve annulus during accessory pathway ablation: evidence for a left atrial "isthmus".

INTRODUCTION: We observed a change in the atrial activation sequence during radiofrequency (RF) energy application in patients undergoing left accessory pathway (AP) ablation. This occurred without damage to the AP and in the absence of a second AP or alternative arrhythmia mechanism. We hypothesized that block in a left atrial "isthmus" of tissue between the mitral annulus and a left inferior pulmonary vein was responsible for these findings. METHODS AND RESULTS: Electrophysiologic studies of 159 patients who underwent RF ablation of a left free-wall AP from 1995 to 1999 were reviewed. All studies with intra-atrial conduction block resulting from RF energy delivery were identified. Fluoroscopic catheter positions were reviewed. Intra-atrial conduction block was observed following RF delivery in 11 cases (6.9%). This was evidenced by a sudden change in retrograde left atrial activation sequence despite persistent and unaffected pathway conduction. In six patients, reversal of eccentric atrial excitation during orthodromic reciprocating tachycardia falsely suggested the presence of a second (septal) AP. A multipolar coronary sinus catheter in two patients directly demonstrated conduction block along the mitral annulus during tachycardia. CONCLUSION: An isthmus of conductive tissue is present in the low lateral left atrium of some individuals. Awareness of this structure may avoid misinterpretation of the electrogram during left AP ablation and may be useful in future therapies of atypical atrial flutter and fibrillation.

Syncope in the elderly: new trends in diagnostic approach and nonpharmacologic management.

Syncope in the elderly is an important health care issue because of the large patient population, challenging diagnostic and therapeutic approaches, and potentially devastating consequences. Significant comorbidity and atypical clinical presentations render a precise determination of the cause of syncope difficult. Recent studies suggest that noninvasive tests, such as carotid sinus massage or tilt-table testing, can be helpful in the diagnostic workup. It has been shown that permanent pacemaker therapy benefits elderly patients with carotid sinus hypersensitivity, and younger patients with recurrent vasovagal syncope. The implantable wireless loop recorder can be effective in documenting transient arrhythmias as causes of syncope in selected patients. Elderly patients with syncope and a low ejection fraction are at increased risk of sudden death due to malignant ventricular arrhythmia. Electrophysiologic study and electrophysiology-guided therapy should be considered in this segment of the population.

Electrophysiologic characteristics of diverse accessory pathway locations of antidromic reciprocating tachycardia.

This study assessed antidromic reciprocating tachycardia (ART) in patients with paraseptal accessory pathways (APs). Previous clinical experience suggests that paraseptal APs are unable to serve as the anterograde limb during ART. Based on the reentry wavelength concept, we hypothesized that anatomic location of a paraseptal AP may not preclude occurrence of ART. If wavelength criteria were met due to prolonged conduction time retrogradely in the atrioventricular node or anterogradely in the AP, ART may be sustained. All patients who had ART in the electrophysiologic laboratory at our institution (1991 to 1998) were studied. Based on fluoroscopically guided electrophysiologic mapping and radiofrequency ablation, AP location was classified as paraseptal, posterior, or lateral. Conduction time and refractoriness measurements were made for all components of the ART circuit. Of 24 patients with ART, 5 (21%) had ART utilizing a paraseptal AP. Anterograde conduction time through the AP and retrograde atrioventricular nodal conduction time were significantly longer in patients with paraseptal versus lateral pathways. Isoproterenol was required for ART induction in 38% of patients with a posterior AP, 36% with lateral AP location, but not in patients with a paraseptal AP. There were no significant differences in tachycardia cycle length or refractoriness of anterograde and/or retrograde components of the macroreentry circuit between the 3 pathway locations. Thus, ART can occur in patients with a paraseptal AP. Slower anterograde pathway conduction, or retrograde atrioventricular nodal conduction renders the wavelength critical for completion of the antidromic re-entrant circuit.

First evidence of premature ventricular complex-induced cardiomyopathy: a potentially reversible cause of heart failure.

Tachycardia-induced cardiomyopathy is a well-recognized and reversible condition, but left ventricular dysfunction due to frequent isolated premature ventricular complexes (PVCs) has not been reported. We observed resolution of dilated cardiomyopathy in a patient after a focal source of PVCs was eliminated by radiofrequency ablation. In a subset of patients with heart failure, PVC-induced cardiomyopathy may be a potentially reversible cause of left ventricular dysfunction.

Speed of visual acuity for vertical eye-movements with a change of accommodation.

Speed of visual acuity was measured for Landolt-C targets presented above and below the line of sight as the targets were moved from 2.4 m to 0.6 m from the observer. Target recognition was faster for a downward than an upward eye movement. There was no difference in response times for the up and down eye-movements when the fixation and target distances were the same.