QTVariability Index Scientific References

sQT Variability Index (2013) Craig P. Dobson, Andrew Kimb, Mark Haigney The aim of this article is to review the evidence behind this metric and how it is currently being used in cardiovascular risk stratification in research populations.

Conclusions and future directions: Since the first description of QTVI by Berger and colleagues in1997, its clinical application has been explored in a wide spectrum of patient groups and disease states. QTVI appears to be a marker for temporal lability of myocardial repolarization, a pathophysiologic substrate that is critical to the genesis of malignant ventricular arrhythmias. As such, QTVI has demonstrated potential clinical value in arrhythmic risk stratification in ischemic and non-ischemic cardiomyopathic patients with reduced LVEF. It has shown increasing promise in risk stratification of patients, such as with heart failure despite preserved ejection fraction, who fall outside absolute indications for ICD placement. Finally, QTVI combines measures of both QT and heart rate variability, and these factors can be evaluated independently to assess the relative contributions of electrical instability and heart failure to a subject’s overall mortality risk. QTVI measurement by Holter monitor may prove to be an attractive method to employ in clinical practice for non-invasive risk stratification. From this single recording, one can both assess the presence of significant arrhythmias and determine a QTVI value to predict their risk for malignant arrhythmias in the future. However, at present, there are significant limitations to clinical use of QTVI for risk stratification. Studies to date have used high resolution (i.e. 1000 Hz sampling frequency) recorders which may require an upgrade for some clinics. As yet, there is no commercially available, FDA-approved software that calculates QTVI using the established Berger methodology. QTVI in healthy subjects has been inadequately characterized. Most importantly, a prospective study randomizing subjects to ICD (or other therapy) based on the results of QTVI measurement needs to be performed before clinical decisions can be based on this metric.

QT Variability Index is Correlated with Autonomic Nerve Activity in Healthy Children

Hirofumi Kusuki,1 Yuka Tsuchiya,1 Yuri Mizutani,1 Miki Nishio,1 Shota Oikawa,2 Rina Nagata,2 Yumi Kiriyanagi,2 Kayo Horio,3 Arisa Kojima,4 Hidetoshi Uchida,4 Namiko Kojima,5 Kazuyoshi Saito,5 Tsuneaki Sadanaga,6 and Tadayoshi Hata 1


 QT interval variability index and QT interval duration during different sleep stages in patients with obstructive sleep apneahttps://pubmed.ncbi.nlm.nih.gov/28899529/#:~:text=Conclusions%3A%20OSA%20is%20associated%20with,abnormality%20than%20measures%20of%20QTc

Conclusions: OSA is associated with increased QT variability. REM sleep per se does not increase QTVI. In OSA patients, QTVI might be a more useful measure to detect ventricular repolarization abnormality than measures of QTc.

Obstructive Sleep Apnea in Patients with Congenital Long QT Syndrome: Implications for Increased Risk of Sudden Cardiac Death https://pubmed.ncbi.nlm.nih.gov/26118557/

Conclusions: The presence and severity of obstructive sleep apnea (OSA) in patients with congenital long QT syndrome (LQTS) is associated with increased QT prolongation corrected for heart rate, which is an important biomarker of sudden cardiac death (SCD). Treatment of OSA in LQTS patients may reduce QT prolongation, thus reducing the risk of LQT-triggered SCD.

Evaluation and Management of Athletes With Long QT Syndrome https://pubmed.ncbi.nlm.nih.gov/27480102/

Conclusion: Detection and management of LQTS in the athletic population is crucial   given the possibility of adverse outcomes with the stress of athletic participation. Preparticipation screening examinations should include a thorough clinical and family history. Screening electrocardiograms may display key findings consistent with LQTS while genetic testing can confirm the diagnosis.

Pseudo-colouring an ECG enables lay people to detect QT-interval prolongation regardless of heart rate


Conclusion: The study indicates that pseudo-colouring enables lay people to visually identify drug-induced QT-prolongation regardless of heart rate, with implications for the more rapid identification and management of diLQTS

Increased QT Interval Variability in 3 Recently Concussed Athletes: An Exploratory Observation


Conclusions: Vagal cardiac autonomic modulation, as quantified by the QTVI, appeared to be negatively affected in concussed athletes within 48 hours of injury, resolved within 1 week, and remained at control group levels 2 weeks later. Serial assessments of QTVI may be of clinical utility in identifying suspected cases of acute concussion and may provide helpful information for determining when an athlete can return to play safely.


Information in this article is worth acknowledgment in developing a business plan and market within the athletic sector.