Cardiac monitoring system with supraventricular tachycardia (SVT) classifications
In one example, a cardiac monitoring system comprises a processor to receive a segment of an electrocardiogram (ECG) signal of a patient, and a memory to store the segment of the ECG. The processor is configured to identify QRS complexes in the segment of the ECG signal, generate a supraventricular (SV) template for SV complexes in the QRS complexes, identify SV complexes in the QRS complexes using the template, identify normal sinus rhythm (NSR) complexes in the segment of the ECG signal, obtain an atrial template for atrial waveforms in the NSR complexes, measure a range of a P-wave of the atrial waveforms from the NSR complexes, save the measured P-waves, and classify the identified SV complexes as either atrial fibrillation (AF) or supraventricular tachycardia (SVT) using the atrial template. Other examples and related methods are also disclosed herein.
1. A method to distinguish between atrial fibrillation (AF) and supraventricular tachycardia (SVT) with a cardiac monitoring system comprising electrocardiogram (ECG) electrodes, a processor configured to receive an (ECG) signal of a patient with the ECG electrodes, and a memory to store the ECG signal, the method comprising:
identifying QRS complexes in the ECG signal as supraventricular (SV) complexes by determining a correlation of the QRS complexes and an SV template to provide a correlation value, wherein the QRS complexes are identified as SV complexes when the correlation value between the QRS complexes and the SV template is greater than a threshold correlation value;
measuring RR intervals between consecutive pairs of the SV complexes in the received ECG signal to determine RR variability between the SV complexes;
for each R of the measured RR intervals, saving atrial waveforms comprising the QRS complex and its preceding P-wave in a window of time, wherein the window is sufficiently large to encompass the P-wave and the QRS complex of the SV complexes;
measuring a P-wave range of the P-waves of the saved atrial waveforms;
comparing the RR variability to a variability threshold;
generally classifying the SV complexes as being either one of AF or SVT when the RR variability is greater than the variability threshold; and
formulating an atrial template from the saved atrial waveforms;
wherein:
the SV complexes are specifically classified as AF when an amplitude of the atrial template is below a predetermined percentage of the P-wave range; and
the SV complexes are specifically classified as SVT when the amplitude of the atrial template is greater than the predetermined percentage of the P-wave range;
detecting a shockable event with the processor based at least in part on the classification of the SV complexes; and
causing a defibrillation voltage to be applied to a patient in response to the shockable event.
2. The method of claim 1 , comprising:
formulating the SV template from normally conducted QRS complexes in the ECG signal.
3. The method of claim 1 , comprising:
formulating the atrial template from normal sinus rhythm (NSR) complexes in the ECG signal.
4. The method of claim 1 , further comprising:
classifying the SV complexes as atrial flutter (AFL) when the RR intervals are integer multiples of a shortest one of the RR intervals.
5. The method of claim 1 , further comprising:
classifying the SV complexes as Wenckebach when the P-waves are similar.
6. The method of claim 1 , further comprising:
determining a heart rate (HR) of the patient based at least in part on the RR intervals; and
classifying the SV complexes as AF when the HR is greater than a predetermined heart rate.
7. The method of claim 1 , further comprising:
identifying a first group of the measured RR intervals having highest RR intervals in a threshold range;
wherein the saved atrial waveforms correspond to the first group of the measured RR intervals.