Medicine:QT interval variability
QT interval variability (QTV) refers to the physiological phenomenon of beat-to-beat fluctuations in QT interval of electrocardiograms. Increased QTV appears to be a marker of arrhythmic and cardiovascular death; it may also play a role for noninvasive assessment of sympathetic nervous system activity.[1] Other terms used include: "QT variability", "beat-to-beat variability of ventricular repolarization (BRV)"
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QT interval measurement
Under normal resting conditions, beat-to-beat changes in QT interval are very small with a standard deviation typically below 5 ms. Digital high resolution ECG sampled at 300 Hz or higher and dedicated computer algorithms are required for QTV assessment.[2] Template-based algorithms that use parts of, or the entire ECG waveform usually deliver good results;[3] template stretching or warping techniques[4] perform comparably well in the presence of noise.
QTV Analysis
A number of metrics have been proposed for QTV quantification. The QT variability index (QTVi) has been most frequently reported in the literature: [math]\displaystyle{ QTVi = \log\frac{SDQT^2/(QT_{mean})^2}{SDHR^2/(HR_{mean})^2} }[/math], where [math]\displaystyle{ SDQT }[/math], [math]\displaystyle{ SDHR }[/math], [math]\displaystyle{ QT_{mean} }[/math], and [math]\displaystyle{ HR_{mean} }[/math] denote standard deviation and mean of QT interval and heart rate time series, respectively.[5]
More advanced approaches that take into account the relationship between QTV and heart rate variability include vector autoregressive process models[6] and information domain approaches.[7]
References
- ↑ Baumert, Mathias; Porta, Alberto; Vos, Marc A.; Malik, Marek; Couderc, Jean-Philippe; Laguna, Pablo; Piccirillo, Gianfranco; Smith, Godfrey L. et al. (June 2016). "QT interval variability in body surface ECG: measurement, physiological basis, and clinical value: position statement and consensus guidance endorsed by the European Heart Rhythm Association jointly with the ESC Working Group on Cardiac Cellular Electrophysiology". Europace 18 (6): 925–944. doi:10.1093/europace/euv405. PMID 26823389.
- ↑ Baumert, Mathias; Schmidt, Martin; Zaunseder, Sebastian; Porta, Alberto (2016-03-01). "Effects of ECG sampling rate on QT interval variability measurement". Biomedical Signal Processing and Control 25: 159–164. doi:10.1016/j.bspc.2015.11.011. ISSN 1746-8094.
- ↑ Baumert, Mathias; Starc, Vito; Porta, Alberto (2012-07-30). "Conventional QT Variability Measurement vs. Template Matching Techniques: Comparison of Performance Using Simulated and Real ECG". PLOS ONE 7 (7): e41920. doi:10.1371/journal.pone.0041920. ISSN 1932-6203. PMID 22860030.
- ↑ "2DSW – Two-Dimensional Signal Warping (2DSW)". http://2dsw.com/.
- ↑ Berger, Ronald D.; Kasper, Edward K.; Baughman, Kenneth L.; Marban, Eduardo; Calkins, Hugh; Tomaselli, Gordon F. (1997-09-02). "Beat-to-Beat QT Interval Variability: Novel Evidence for Repolarization Lability in Ischemic and Nonischemic Dilated Cardiomyopathy" (in en). Circulation 96 (5): 1557–1565. doi:10.1161/01.cir.96.5.1557. ISSN 0009-7322. PMID 9315547. http://circ.ahajournals.org/content/96/5/1557.
- ↑ Porta, A.; Baselli, G.; Caiani, E.; Malliani, A.; Lombardi, F.; Cerutti, S. (1998-01-01). "Quantifying electrocardiogram RT-RR variability interactions" (in en). Medical and Biological Engineering and Computing 36 (1): 27–34. doi:10.1007/bf02522854. ISSN 0140-0118. PMID 9614745.
- ↑ Porta, Alberto; Bari, Vlasta; Maria, Beatrice De; Baumert, Mathias (2017). "A network physiology approach to the assessment of the link between sinoatrial and ventricular cardiac controls". Physiological Measurement 38 (7): 1472–1489. doi:10.1088/1361-6579/aa6e95. PMID 28430108. http://stacks.iop.org/0967-3334/38/i=7/a=1472?key=crossref.cb8f5ee1a245ed5d09d7fd5841119e43.
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