Impaired T-wave amplitude adaptation to heart-rate induced by cardiac deconditioning after 5-days of head-down bed-rest

Weightlessness and Cardiac Rhythm Disorders: Current Knowledge from Space Flight and Bed-Rest Studies

“…Healthy subjects have been found characterized by a RR dependency of the T-wave amplitude (Haarmark et al, 2010), while a less pronounced dependency was present in patients with acute myocardial infarction (Johannesen et al, 2010), thus supporting the hypothesis that impairment of T-wave amplitude adaptation to RR could represent a new dynamic marker of increased risk for life-threatening arrhythmias. After 5-days HDBR, a marked loss in strength of the linear regression of T-wave amplitude (and area) with RR was observed, thus evidencing possible impaired T-wave amplitude adaptation to heart-rate induced by this condition (Caiani et al, 2013a).…”

“…In 19 male subjects undergoing 5-days HDBR while in control (CTRL) with no CM applied, computerized analysis of 24 h Holter ECG based on selective beat averaging applied to the night period showed a 10% decrease in SPV and a 28% increase in QRS-T angle parameters (Caiani et al, 2013a) compared to pre-HDBR values. As concerns SPV and QRS-T angle, the nature of the observed changes could underline augmented repolarization heterogeneity that has been associated with risk of lifethreatening arrhythmias, as functionally linked to dispersion of refractoriness, thus potentially facilitating ventricular tachycardia (Draisma et al, 2006).…”

“…Using the same selective beat averaging applied to the night period, compared to pre-HDBR, a significant reduction in T wave peak amplitude, was visible both in short-(−8%) (Caiani et al, 2013a), where standing exercise CM seemed able to partially reduce this decrease (−4%) (Caiani et al, 2013b), and mid-HDBR (−13%) (Caiani et al, 2014a). Also, dipolar T-wave voltage over the 12-leads was reduced (−6%) with 90-days HDBR (−6%) (Sakowski et al, 2011).…”

Index of T:wave Variation as a Predictor of Sudden Cardiac Death in Chronic Heart Failure Patients with Atrial Fibrillation

“…Selective beat averaging was used to obtain averages of P-QRS-T complexes preceded by similar RR intervals [8,9]. Based on this, we computed the RR interval series along the 24h Holter recording, the RR interval associated to beat i being defined as the difference between the i and Figure 1.…”

Changes in ventricular repolarization and cardiac function induced by head-down bed rest

“…Accordingly, our aim was to test if even short 5-days strict 6• HDBR maneuver could induce ECG signals were acquired using a high-resolution (fs=1000 Hz) 12-lead 24-hours Holter digital recorder (H12+, Mortara Instrument Inc., Milwaukee, WI) with beginning of the acquisition 6 days before the start of the HDBR (PRE), the fifth day of HDBR (HDT5) and five days after the end of HDBR (POST). To avoid potential interactions induced by other experiments conducted during the day, the nocturnal ECG (23:00-6:30) was analyzed as described in [4]. Briefly, inverse Dower matrix transformation [5] was applied to obtain the orthogonal leads X, Y, Z, from which the vectorcardiogram was computed.…”