Aigars Rubulis

Cardiac fatigue in long-distance runners is associated with ventricular repolarization abnormalities

BACKGROUND Prolonged exercise can induce cardiac fatigue, which is characterized by biomarker release and impaired myocardial function. The impact on ventricular electrophysiology is largely unknown. OBJECTIVE The objective of this study was to examine changes in ventricular repolarization after a 30-km cross-country race in runners aged >or=55 years. METHODS Fifteen healthy participants (62 +/- 5 years) were assessed using biomarkers (N-terminal pro-brain natriuretic peptide [NT-proBNP], troponin T [TnT]), tissue Doppler echocardiography, and vectorcardiography at baseline, within 1 hour postrace and on days 1 and 6 postrace. RESULTS During the race, NT-proBNP increased from 42 ng/L (interquartile range 25-117) to 187 ng/L (113-464), and TnT increased from undetectable levels to 0.03 microg/L (0.015-0.05). Global strain (19.1% +/- 2.2%) decreased on day 1 (17.2% +/- 1.8%) and day 6 (17.9% +/- 1.5%; P <.01). QT(c) increased from 431 +/- 15 ms prerace to 445 +/- 22 ms postrace and 445 +/- 15 ms on day 1 (P <.05), mainly because of an increased T(peak-end) interval (prerace 108 +/- 13 ms, postrace 127 +/- 43 ms, day 1 127 +/- 43 ms; P <.05). Postrace, T(area) (baseline 75 +/- 26 microVs) peaked on day 1 (105 +/- 42 microVs) and remained high on day 6 (89 +/- 37 microVs; P <.05). Runners with higher baseline NT-proBNP developed greater impairment of myocardial velocities (rho = -0.68 to -0.54; P <.05) and a larger increase in T(area) (rho = 0.73; P <.01). CONCLUSION Cardiac fatigue induced by prolonged exertion is associated with sustained abnormalities in ventricular repolarization. Runners with higher baseline NT-proBNP are especially liable to such alterations of cardiac function.

Prediction of cardiovascular death and myocardial infarction by the QRS-T angle and T vector loop morphology after angioplasty in stable angina pectoris: an 8-year follow-up ☆,☆☆

Reliable cardiovascular (CV) risk assessment by a noninvasive tool would be of great value for CV event prevention. The present study consists of 187 coronary artery disease patients with 8 years of follow-up. Eight vectorcardiographic parameters characterizing different aspects of ventricular repolarization were analyzed at baseline: (1) the ST-segment (ST-VM), (2) the T vector angles (QRS-T angle, Televation, and Tazimuth), (3) the T vector loop morphology (Tavplan and Teigenvalue), and (4) Tarea and Tpeak-end. Cardiovascular death, myocardial infarction (MI), and repeated revascularization were traced via national registries. There were 16 CV deaths and 19 MIs; 89 patients remained free from CV events and revascularization. Ventricular repolarization parameters independently predicted CV death (widened QRS-T angle) and new MI (increased Tavplan) during follow-up. CV mortality was associated with increased divergence between depolarization and repolarization waves (widened QRS-T angle). Increased Tavplan, presumably reflecting heterogeneous repolarization, predicted future MI, which is a novel finding.

Distorted T-vector loop and increased heart rate are associated with ventricular fibrillation in a porcine ischemia-reperfusion model

BACKGROUND The ventricular repolarization (VR) response to short-lasting coronary occlusion has been characterized by 3-dimensional vectorcardiography during angioplasty in humans; the T-vector loop becomes distorted (increased T(avplan)) and more circular (decreased T(eigenvalue)), but these changes have not been related to ventricular arrhythmias. PURPOSE The VR response was therefore explored in a porcine ischemia-reperfusion model and compared in pigs with (n = 16) vs without (n = 17) ventricular fibrillation (VF). METHODS Different aspects of VR were evaluated at baseline, at maximum ischemia, before reperfusion and at the subsequent ST maximum, after 1 hour of reperfusion, and before VF. Three aspects of the VR response were assessed: the ST-segment, the T-vector angles, and the T-vector loop morphology. RESULTS All parameters changed significantly from baseline during ischemia and/or reperfusion. The early changes were similar to those previously observed in humans during angioplasty. The VF episodes were preceded by a significantly exaggerated T-loop distortion (increased T(avplan)) and increased heart rate. CONCLUSION Aggravated T-loop distortion might, in this porcine ischemia-reperfusion model, reflect aspects of VR relevant to arrhythmogenesis.

Ischemia-induced repolarization response in relation to the size and location of the ischemic myocardium during short-lasting coronary occlusion in humans

BACKGROUND The ventricular repolarization (VR) response to short-lasting coronary occlusion has been characterized by 3-dimensional vectorcardiography (VCG) in humans; the T vector loop becomes distorted and more circular. The purpose of this study was to relate these changes to the size of the myocardium at risk (MAR) and its location. METHODS Continuous VCG was applied during transient coronary occlusion in 35 elective angioplasty patients, and the size of the MAR was estimated by single-photon emission computed tomography. Three VR aspects were assessed at baseline vs maximum ischemia: the ST segment, the T vector angles, and the T vector loop morphology. RESULTS The T loop morphology changes were significantly associated with MAR size, but also dependent of its location. In contrast, the early phase of VR reflected by the ST segment responded to acute ischemia in relation to the MAR size independent of location. CONCLUSION The VR changes were related both to the size and the location of the MAR and most pronounced during occlusion of the left anterior descending artery.