A Novel Method for Determining the Phase of T-Wave Alternans

Abstract

Background T-wave alternans (TWA) has been implicated in the pathogenesis of ventricular arrhythmias and sudden cardiac death (SCD). However, in order to effectively estimate and suppress TWA, the phase of TWA must be accurately determined. Methods and Results We developed a method that computes the beat-by-beat integral of the T-wave morphology, over time points within the T-wave with positive alternans. Then, we estimated the signed derivative of the T-wave integral sequence which allows the classification of each beat to a binary phase index. In animal studies, we found that this method was able to accurately identify the T-wave phase in artificially induced alternans (p<0.0001). The coherence of the phase increased consistently after acute ischemia induction in all body-surface and intracardiac leads (p<0.0001). Also, we developed a phase resetting detection algorithm that enhances the diagnostic utility of TWA. We further established an algorithm that employs the phase of TWA in order to deliver appropriate polarity pacing pulses (all interventions compared to baseline, p<0.0001 for alternans voltage; p<0.0001 for Kscore), to suppress TWA. Finally, we demonstrated that using the phase of TWA we can suppress spontaneous TWA during acute ischemia; 77.6% for alternans voltage (p<0.0001) and 92.5% for Kscore (p<0.0001). Conclusions We developed a method to quantify the temporal variability of the TWA phase. This method is expected to enhance the utility of TWA in predicting ventricular arrhythmias and SCD and raises the possibility of using upstream therapies to abort a ventricular tachyarrhythmia prior to its onset.

Utility of a Smartphone Based System (cvrPhone) to Predict Short-term Arrhythmia Susceptibility

“…Percutaneous techniques were used to induce coronary artery ischemia, in a closed-chest model 9,11–14 . Briefly, either the mid left circumflex or the mid left anterior descending coronary arteries were occluded with a balloon using standard angioplasty techniques.…”

Microvolt T-Wave Alternans Is Modulated by Acute Low-Level Tragus Stimulation in Patients With Ischemic Cardiomyopathy and Heart Failure

“…We have previously demonstrated the ability of microvolt TWA to predict short- (Weiss et al, 2011;Merchant and Armoundas, 2012;Merchant et al, 2013bMerchant et al, , 2020 and long-term (Merchant et al, , 2015Sohn et al, 2019) susceptibility to ventricular tachy-arrhythmias and sudden cardiac death, using an algorithm based on the spectral method (Smith et al, 1988;Merchant and Armoundas, 2012;Merchant et al, , 2013bMerchant et al, , 2015Sohn et al, 2019). Briefly, the alternans voltage was used as a direct measure of the presence of alternans and calculated based on the amplitude of the power spectrum at the alternans frequency (0.5 cycles/beat) (Armoundas et al, 2013;Sayadi et al, 2013;Merchant et al, 2014Merchant et al, , 2020. The alternans ratio, K score , was used as a statistical measure of alternans calculated as the alternans voltage relative to the background noise level (Armoundas et al, 2013;Sayadi et al, 2013;Merchant et al, 2014Merchant et al, , 2020.…”

“…Briefly, the alternans voltage was used as a direct measure of the presence of alternans and calculated based on the amplitude of the power spectrum at the alternans frequency (0.5 cycles/beat) (Armoundas et al, 2013;Sayadi et al, 2013;Merchant et al, 2014Merchant et al, , 2020. The alternans ratio, K score , was used as a statistical measure of alternans calculated as the alternans voltage relative to the background noise level (Armoundas et al, 2013;Sayadi et al, 2013;Merchant et al, 2014Merchant et al, , 2020. TWA voltage and K score was estimated using the spectral method for each moving window of 128-beat data sequence, advanced one beat at a time, using a 512-point power spectrum to improve frequencydomain resolution.…”

Clinical Potential of Beat‐to‐Beat Diastolic Interval Control in Preventing Cardiac Arrhythmias

“… 26 , 40 , 75 , 76 The real‐time control system is capable of recording and analyzing TWA from multiple intracardiac leads 11 and delivering stimuli at a fixed interval on a beat‐by‐beat basis on detection of the T wave. 77 In addition, the algorithm has the ability to identify and exclude/replace abnormal beats (ie, premature ventricular complexes and extrasystoles) based on a template matching technique. Any changes in alternans phase caused by abnormal beats are also addressed by an alternans‐phase detection algorithm.…”

“…Any changes in alternans phase caused by abnormal beats are also addressed by an alternans‐phase detection algorithm. 77 …”