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ST-segment deviations during pacing-induced increased heart rate in patients without coronary artery disease.
Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Anaesthesiology.
Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Anaesthesiology.
Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine.
Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Anaesthesiology.ORCID iD: 0000-0002-5325-2688
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2005 (English)In: Clinical Physiology and Functional Imaging, ISSN 1475-0961, E-ISSN 1475-097X, Vol. 25, no 4, 246-522 p.Article in journal (Refereed) Published
Abstract [en]

INTRODUCTION: In order to interpret ST-segment changes as an indicator of ischemia in patients with higher heart rates (HRs), the relation between ST-segment levels and HR needs to be well defined in subjects without coronary artery disease. METHODS: Eighteen patients with normal ECGs in the catheterization laboratory, after radiofrequency ablation of AV nodal re-entry tachycardia or an accessory pathway were included. Computerized online vectorcardiography (VCG) was performed during step-wise atrial pacing-induced increases in HR up to 150 beats min(-1) (bpm). The ST-vector magnitude (ST-VM) and the relative ST change vector magnitude (STC-VM) were analysed at the J point, J + 20 and J + 60 ms. RESULTS: There was no divergence in the course of ST-VM or STC-VM based on J point + 0, 20, or 60 ms during increasing HR. The STC-VM mean values increased progressively during increases in HR above 100 bpm, with an average increase in STC-VM of 15-20 microV per 10 bpm increases in HR. The ST-VM response during HR increases showed a heterogeneous and unpredictable pattern. CONCLUSION: The STC-VM increases linearly with rising HRs above 100 bpm. The STC-VM can exceed widely recognized ischemic thresholds during higher HRs in the absence of ischemia. The choice of J point time to ST-VM measurements as tested here is not important for the STC-VM relation to HR at these HR levels. Further clinical testing is needed to improve the diagnostic specificity of STC-VM measurements during increased HRs.

Place, publisher, year, edition, pages
2005. Vol. 25, no 4, 246-522 p.
Keyword [en]
Adult, Arrhythmias; Cardiac/*diagnosis/*physiopathology/therapy, Cardiac Pacing; Artificial/*methods, Coronary Disease/diagnosis/physiopathology/therapy, Female, Heart Rate, Humans, Male, Middle Aged, Statistics as Topic, Vectorcardiography/*methods
URN: urn:nbn:se:umu:diva-6814DOI: 10.1111/j.1475-097X.2005.00613.xPubMedID: 15972028OAI: diva2:146484
Available from: 2007-12-18 Created: 2007-12-18 Last updated: 2015-09-15Bibliographically approved
In thesis
1. Detection of myocardial ischemia: clinical and experimental studies with focus on vectorcardiography, heart rate and perioperative conditions.
Open this publication in new window or tab >>Detection of myocardial ischemia: clinical and experimental studies with focus on vectorcardiography, heart rate and perioperative conditions.
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Introduction. Multiple clinical methods for detecting myocardial ischemia are utilised in the hospital setting each day, but there is uncertainty about their diagnostic accuracy. In the operating room, multiple methods may be employed, while in the CCU advanced electrophysiological (ECG) techniques for myocardial ischemia detection, and in particular, ST segment analysis, are common. Vectorcardiography (VCG) is one form of ECG.

Several conditions other than ischemia may cause marked ST changes, which can impair the process of diagnosis of clinical ischemia. Elevated HR is one of these factors, which is studied here. The hypotheses were about concordance of different methods to detect ischemia, and relation of ECG ST levels to HR with and without myocardial ischemia.

Methods. Study I. Anesthetised vascular surgical patients with coronary artery disease were studied during the start of anesthesia and surgery: ECG, hemodynamic, mechanical, and metabolic parameters were measured and categorised as positive or negative with reference to a specific definition of myocardial ischemia. Study II. Awake patients with no ischemic heart disease were paced in graded steps, and VCG ST analyses were performed.

Study III. Anesthetised pigs were studied for local metabolic and VCG ST changes related to controlled HR levels and transient coronary occlusion. Study IV. Thirty five anesthetised coronary artery disease (CAD) patients and ten non-CAD patients were paced at controlled levels, and great coronary artery vein (GCV) lactate measurement was used to determine presence or absence of myocardial ischemia. The CAD patients were paced up to HR levels where myocardial ischemia could be confirmed. The relation of HR-related VCG ST levels to presence or absence of ischemia was analysed. In Studies II,, III, and IV the ST vector magnitude (ST-VM), the change from baseline in ST-VM (STC-VM), and the vector angle change from baseline (STC-VA) were analysed for each step.

Results. Study I. Poor concordance was demonstrated for positive events (presumed myocardial ischemia) between the hemodynamic, ECG, mechanical, and metabolic detection methods. Study II. STC-VM but not ST-VM levels demonstrated HR-related increases in the presumed absence of myocardial ischemia in 18 awake subjects. J point time to ST measurement did not affect the response of VCG ST to HR. Study III. STC-VM levels showed HR-related increases in the absence of ischemia (tested by local metabolic observations). VCG ST parameters responded positively to transient regional ischemia. Study IV. CAD patients, which demonstrated a clear pattern of onset and progress of ischemia during pacing, were further analysed for the relation of VCG ST level to ischemia. Sensitivity and specificity of STC-VM levels were described by ROC analysis for a range of STC-VM levels.

Conclusions. Concordance of different measures for detection of onset of myocardial ischemia is difficult to assess in the absence of a very reliable reference method. The contribution of HR and ischemia to VCG ST levels were estimated in study subjects. HR-related increases in STC-VM occur in the absence of ischemia. HR levels need to be considered when interpreting STC-VM as a diagnostic test for ischemia. Further study is needed to establish criteria that take into account multiple clinical factors in order to improve the predictive value of our tests for myocardial ischemia.

Place, publisher, year, edition, pages
Umeå: Kirurgisk och perioperativ vetenskap, 2005. 69 p.
Umeå University medical dissertations, ISSN 0346-6612 ; 982
Anaesthesiology and intensive care, myocardial ischemia, pacing, vectorcardiography, electrocardiography, heart rate, myocardial lactate, Anestesiologi och intensivvård
National Category
Anesthesiology and Intensive Care
Research subject
urn:nbn:se:umu:diva-598 (URN)91-7305-942-0 (ISBN)
Public defence
2005-10-15, Hörsal BETULA, 6M, NUS, Norrlands Universitetssjukhus, Umeå, 09:00 (English)
Available from: 2005-09-23 Created: 2005-09-23 Last updated: 2009-11-16Bibliographically approved

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