ST-segment deviations during pacing-induced increased heart rate in patients without coronary artery disease

Authors: Häggmark, Sören¹; Haney, Michael F.²; Jensen, Steen M.³; Johansson, Göran²; Näslund, Ulf³

Source: Clinical Physiology and Functional Imaging, Volume 25, Number 4, July 2005 , pp. 246-252(7)

Publisher: Wiley-Blackwell

Abstract:

Summary 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 μV 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.

Keywords: electrocardiography; heart rate; myocardial ischemia; ST segment; tachycardia; vectorcardiography

Document Type: Research article

DOI: http://dx.doi.org/10.1111/j.1475-097X.2005.00613.x

Affiliations: 1: Cardiothoracic Surgery, Heart Centre, University Hospital, Umeå 2: Department of Surgical and Perioperative Science, Anaesthesiology and Intensive Care Medicine, Umeå University 3: Cardiology, Heart Centre, University Hospital and Department of Public Health and Clinical Medicine, Umeå University, Umeå, Sweden

Publication date: 2005-07-01

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• In this Subject: Anatomy & Physiology ,  Radiology & Imaging
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