Spontaneous Ventricular Tachyarrhythmia Database

Published: May 2, 2007. Version: 1.0

Spontaneous Ventricular Tachyarrhythmia Database (May 2, 2007, midnight)

The Spontaneous Ventricular Tachyarrhythmia Database (Version 1.0 from Medtronic, Inc.) contains 135 pairs of RR interval time series, recorded by implanted cardioverter defibrillators in 78 subjects. One series of each pair includes a spontaneous episode of ventricular tachycardia or ventricular fibrillation, and the other is a sample of the intrinsic (usually sinus) rhythm.

Please include the standard citation for PhysioNet:

Goldberger, A., Amaral, L., Glass, L., Hausdorff, J., Ivanov, P. C., Mark, R., ... & Stanley, H. E. (2000). PhysioBank, PhysioToolkit, and PhysioNet: Components of a new research resource for complex physiologic signals. Circulation [Online]. 101 (23), pp. e215–e220.

Introduction

This database contains 135 pairs of RR interval time series, recorded by implanted cardioverter defibrillators (Medtronic Jewel PlusTM ICD 7218) in 78 subjects. Each series contains between 986 and 1022 RR intervals. One series of each pair includes a spontaneous episode of ventricular tachycardia (VT) or ventricular fibrillation (VF), and the other is a sample of the intrinsic (usually sinus) rhythm.

The ICD continuously digitizes and analyzes the patient's electrogram (EGM). Four EGM signals are digitized:

• HVA - HVB (Can - Coil)
• P-/S-P+/S (Tip - Ring)
• HVA-P+/S (Can - Ring)
• P-/S - HVB (Tip - Coil)

R-waves are detected in the EGM with an auto-adjusting sense amplifier. The automatic threshold adjustment can affect measured cycle lengths if the sensed R wave crosses the decaying threshold at different levels. RR interval measurements are always based on the P-/S-P+/S (Tip-Ring) EGM. Each interval is classified depending on the programmed tachycardia and fibrillation detection intervals (TDI and FDI, respectively).

The ICD maintains a buffer containing the 1024 most recently measured RR intervals. When a tachyarrhythmia is detected, the ICD delivers programmed pacing, cardioversion, or defibrillation therapy and records a snapshot of the RR interval buffer, thus capturing the sequence of 1024 RR intervals that immediately precede the detected event (ending at the time when the ICD first detected the event, not at the termination of the event). The stored intervals are truncated (not rounded) to a multiple of 10 ms (e.g., an interval of 457 ms is recorded in the snapshot as 450 ms). The most recent snapshot is stored in the ICD's memory until the patient returns for a checkup, at which time the ICD is interrogated using a Medtronic 9790 ICD programmer, the stored snapshot is downloaded, and the ICD may be reprogrammed as appropriate.

In addition to the stored snapshot of the most recently detected event, a snapshot of the RR interval buffer is also obtained when the ICD is interrogated; such snapshots thus contain the most recent RR intervals, which can be used as baseline (control) data to compare with the detected events. Varying numbers of the least recent intervals in these snapshots are lost during device interrogation, so these baseline sequences contain between 986 and 1022 intervals each.

The snapshots downloaded from the ICDs also include a few seconds of the high-resolution EGM, as illustrated below; EGM segments are not available for the records in this database, however.

Each RR interval sequence included in this database has a three-part file name of the form ssss.ttn, where ssss is a four-digit patient number, tt is either vf, vt, or mr, and n is a sequence number for each type of event. The files as provided by Medtronic can be found in the RRdata1 and mr directories. They are in plain text format, and each contains a column of numbers, which are the RR intervals in milliseconds. In addition, a set of PhysioBank-compatible annotation and header files has been created from the text files; these are in the data directory. These have record names of the form ssss_ttn, where the components are as described above.

• vf - intervals prior to detection of spontaneous VF
• vt - intervals prior to detection of spontaneous VT
• mr - intervals prior to ICD interrogation ("mr" = "most recent")

Each vf and vt sequence has a matching mr (baseline) sequence designated by the same numerals in the sequence names. For example, 8076.mr2 is the baseline sequence matching 8076.vt2. These matched pairs of RR interval sequences are referred to as sequence pairs below.

Several patients had multiple VT or VF episodes. The database was subdivided into 4 datasets:

Researchers should use care in combining these datasets to avoid bias due to any one patient with many sequence pairs.

Six patients had both VT and VF episodes. In five of these cases, the baseline sequence associated with the first VF has the suffix mra, to avoid conflicts with the baseline sequences associated with the first VT (with the standard suffix mr1). The names of the files in the sequence pairs for these six patients are given in the table below:

Data Collection

The episodes included in this database were recorded by Medtronic ICD 7218 defibrillators, from patients without pacemakers in the US and Canada on or before 3 January 1997. Episodes were retrieved from the implanted devices during the patients' scheduled follow-ups and during subsequent unscheduled visits. Each episode was classified manually using the criteria listed in the next section. The final database included all recorded episodes except for:

• spontaneous episodes that occurred immediately post-implant, or between the initial and final interrogation during a follow-up
• episodes for which the VT or VF EGM could not be compared with a sinus rhythm EGM from the same source
• VTs and VFs for which fewer than 1000 R-R intervals were recorded
• SVTs that were inappropriately detected as VT or VF.

In all, 142 patients were studied, and this database contains 135 episodes from 78 patients who experienced at least one VT or VF episode. Five patients had both a VT and a VF episode included here.

An accompanying Excel spreadsheet (phys.xls) contains information such as file names, date and time, ICD and manual classifications, prestorage status, EGM source, patient demographics, cardiac history, medications, NYHA classification, etc.

Rhythm Classification Criteria

Detected episodes were classified based on five morphologic characteristics: shape, number of baseline crossings, initial slope, largest component position, and notching. These compared with sinus rhythm EGMs to determine VT, VF, or SVT.

Description of the Excel Files

VT/VF episodes and Most Recent interval files were stored in text format and imported into Excel. VT/VF episodes have 1024 intervals. MR sequences have 986-1022 intervals due to lost data during interrogation.

Contributors

This database was contributed to PhysioNet by Medtronic, Inc., and originally described by Ann M. Pearson and Walter H. Olson of Medtronic.

Disclaimer

Errors might exist; users assume all responsibility for the use of this data.

References

Swarna US, Callans DJ, Schwartzman D, Gottlieb CD, Marchlinski, FE. The value of right ventricular endocardial electrogram recordings in discriminating different morphologies of ventricular tachycardia.

Address for copies: David Schwatzman, MD, Philadelphia Heart Institute, Philadelphia, PA 19104.