Electrocardiographic measurements of regional atrial fibrillation cycle length.

BACKGROUND: Differences in atrial fibrillation (AF) cycle length (CL) between the left (LA) and right (RA) atrium and coronary sinus (CS) may help separate paroxysmal from persistent AF and identify patients most likely to respond to pulmonary vein isolation, but has not been measured noninvasively. METHODS AND RESULTS: We developed methods to estimate regional intraatrial AF CL from the surface electrocardiogram (ECG) in 20 patients with persistent AF and 10 patients with paroxysmal AF prior to ablation. Intraatrial AF CL was measured near the LA appendage, mid-CS, and lateral RA. In simultaneous filtered ECG, AF CL was estimated using autocorrelation. The mean of ECG-derived AF CL in leads V5, I, and aVL was used to estimate LA CL; leads aVF, II, and III for CS CL; and V1, V2, and aVR for RA CL. ECG CL estimates for the LA, CS, and RA had R(2) > 0.91 versus measured CL (all P < 0.001). Though magnitudes of left-versus-right AF CL gradients were small in this series, the ECG predicted the direction of gradients in 62% of measurements (P < 0.05). When the gradient was >10 ms, the direction was accurately predicted in eight of 11 patients. The accuracy of AF CL estimates was not adversely affected by AF type or LA dilatation (< or =40 or >40 mm). The ECG-estimated AF-CL showed high 5-minute temporal stability (P < 0.001 each chamber). CONCLUSIONS: Left and right atrial AF CL, and their gradients, can be accurately determined from the ECG using autocorrelation analysis. This approach may be a helpful guide prior to ablation procedures.

The clinical presentation and impact of diagnostic delays on emergency department patients with spinal epidural abscess.

Previous reports have recommended the use of a "classic triad" of fever, spine pain, and neurologic deficits to diagnose spinal epidural abscess (SEA); however, the prognosis for complete recovery is poor once these deficits are present. This retrospective case-control study investigates the impact of diagnostic delays on outcome and explores the use of risk factor screening for early identification of SEA in a population of ED patients. Inpatients with a discharge diagnosis of SEA and a related ED visit before the admission were identified over a 10-year time period. In addition, a pool of ED patients presenting with a chief complaint of spine pain was generated; controls were hand-matched 2:1 to each SEA patient based on age and gender. Data regarding demographics, presence of risk factors, physical examination findings, laboratory and radiographic results, and clinical outcome were abstracted from medical records and entered into a database for further analysis. Patients with SEA were compared to matched controls with regard to the prevalence of risk factors and the "classic triad." We also explored the impact on outcome of diagnostic delays, defined as either: 1) multiple ED visits before diagnosis, or 2) admission without a diagnosis of SEA and >24 h to a definitive study. A total of 63 SEA patients were hand-matched to 126 controls with spine pain. Diagnostic delays were present in 75% of SEA patients. Residual motor weakness was present in 45% of these patients vs. only 13% of patients without diagnostic delays (odds ratio 5.65, 95% C.I. 1.15-27.71, p < 0.05). The "classic triad" of spine pain, fever, and neurologic abnormalities was present in 13% of SEA patients and 1% of controls during the initial visit (p < 0.01); one or more risk factors were present in 98% of SEA patients and 21% of controls (p < 0.01). The erythrocyte sedimentation rate (ESR) was more sensitive and specific than total white blood cell (WBC) count as a screen for SEA. In conclusion, diagnostic delays are common in patients with SEA, often leading to irreversible neurologic deficits. The use of risk factor assessment is more sensitive than the use of the classic diagnostic triad to screen ED patients with spine pain for SEA. The ESR may be a useful screening test before magnetic resonance imaging in selected patients.