ishne

An ISHNE Holter ECG toolbox for Nelson.

ISHNE 1.0 is the binary interchange format for long-term (Holter)

It is designed to be a dependency of higher-level toolboxes (such as ecglab) rather than to interpret the signals itself.

Load

run('/path/to/ishne/loader.m')

Functions

All functions live in the ishne package (call them as ishne.read, ishne.write, ...).

Function	Purpose
ishne.read(file, ...)	Read a file into the neutral struct. Options: 'Physical', 'Leads', 'Data'.
ishne.write(file, r, ...) / ishne.write(file, samples, rate, ...)	Write the neutral struct, or a plain matrix. Options: 'Leads', 'Resolution', 'Physical'.
ishne.header(file)	Read only the header, no samples, fast.
ishne.info(file)	A compact human-readable summary (header only).
ishne.isishne(file)	Probe a file for the ISHNE1.0 magic, never throws.
ishne.validate(file)	Check the magic, the length, the lead count and the header CRC.
ishne.select(r, which)	Keep a subset of leads, by name or index, in the order asked.
ishne.crop(r, [t0 t1], ...)	Keep a time (or 'Samples') window of every lead.
ishne.frombytes(bytes)	Parse a recording already in memory.
ishne.tobytes(r)	Serialise a recording to a byte vector, the inverse of frombytes.

ishne.read options: 'Physical', true returns the samples in millivolts (raw * resolution / 1e6, the resolution being the nanovolts per step each lead stores) instead of the raw signed sixteen-bit integers the file holds (raw is the default, so a read followed by ishne.write is lossless, checksum included, with the resolution on the struct to scale with); 'Leads', which keeps a subset by name or index; and 'Data', false reads the header only.

The samples are raw int16 with a per-lead resolution in nanovolts per least significant bit, so physical millivolts are one scaling away. The fixed header carries a CRC-CCITT checksum that ishne.validate verifies. The module both reads and writes the signal file; ISHNE annotation files are not supported.

The neutral struct

ishne.read returns one struct with no domain assumptions:

r.kind          % 'ishne.record'
r.path
r.samples       % N x L, one column per lead (raw int16, or millivolts)
r.leadCount, r.leadCodes, r.leadNames
r.resolution    % nanovolts per least significant bit, one per lead
r.leadQuality
r.samplingRate  % Hz
r.version, r.sampleCount, r.checksum
r.header        % .firstName .lastName .id .sex .race .birthDate
                % .recordDate .fileDate .startTime .pacemaker .recorder
r.variableBlock, r.variableText

ishne.write accepts the same shape, or a plain matrix (one column per lead) with a rate; the lead names and resolution are used when present and defaulted when not.

Example

A ready-to-run tour is in examples/read_write_demo.m.

% Round-trip a two-lead Holter record and read it back in physical units.
rate = 200;
t = (0:5 * rate - 1)' / rate;
file = [tempname(), '.ecg'];
ishne.write(file, [sin(2*pi*1.2*t), 0.5*cos(2*pi*1.2*t)], rate, ...
  'Leads', {'I', 'II'}, 'Resolution', 1000, 'Physical', true);
r = ishne.read(file, 'Physical', true);

Dependencies

This module depends on no other Nelson module.

License

LGPL-3.0-or-later.