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Europace Advance Access originally published online on October 7, 2009
Europace 2009 11(11):1529-1535; doi:10.1093/europace/eup295
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Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2009. For permissions please email: journals.permissions@oxfordjournals.org.

Electrocardiography and Risk Stratification

Adrenergic stimulation increases repolarization dispersion and reduces activation–repolarization coupling along the RV endocardium of patients with cardiomyopathy

Raja J. Selvaraj, Adrian M. Suszko, Anandaraja Subramanian, Kumaraswamy Nanthakumar and Vijay S. Chauhan*

Division of Cardiology, University Health Network, Toronto, Canada

Aims: Dispersion of repolarization (DOR) in the human heart is minimized by activation–repolarization coupling. Adrenergic stimulation can be proarrhythmic in patients with impaired left-ventricular function and its effect on repolarization dispersion has not been systematically investigated. Our objective was to study the effect of dobutamine on repolarization dispersion and activation–repolarization coupling in patients with cardiomyopathy.

Methods and results: Activation recovery intervals (ARI) and activation times (AT) were measured from unipolar electrograms at 10 sites along the apicobasal right ventricle (RV) in 14 patients with cardiomyopathy (LVEF < 40%). These measurements were made during control, dobutamine 2.5–5.0 µg/kg/min, and a recontrol phase while maintaining constant heart rates with atrial pacing. Dispersion of repolarization was calculated from the total recovery time (TRT, AT+ARI). Activation–repolarization coupling was assessed by linear regression of ARI and AT. Dispersion of repolarization across all 10 sites and between adjacent sites increased with dobutamine compared with control (whole DOR: range 15 ± 2 vs. 12 ± 2 ms, P = 0.06 and standard deviation 5.5 ± 0.9 vs. 4.3 ± 0.9 ms, P = 0.04; adjacent DOR: 5.9 ± 0.8 vs. 4.5 ± 0.6 ms, P = 0.04). This was associated with shallower ARI/AT slopes (–0.3 ± 0.2 vs. –0.8 ± 0.2, P = 0.05) and a decrease in ARI–AT correlation (R2 0.4 ± 0.1 vs. 0.6 ± 0.1, P = 0.05) with dobutamine compared with control.

Conclusion: Adrenergic stimulation increases apicobasal RV DOR and reduces coupling between activation and repolarization in patients with cardiomyopathy. This may provide a mechanism for the proarrhythmic potential of heightened adrenergic states in these patients.

Key Words: Repolarization dispersion, Activation repolarization coupling, Adrenergic stimulation, Cardiomyopathy

* Corresponding author. Tel: +1 416 340 3172, Fax: +1 416 340 4710, Email: vijay.chauhan{at}uhn.on.ca

Manuscript submitted 20 May 2009. Accepted after revision 7 September 2009.


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