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Original Articles

Slow and Discontinuous Conduction Conspire in Brugada Syndrome

A Right Ventricular Mapping and Stimulation Study

Pieter G. Postema, MD; Pascal F.H.M. van Dessel, MD, PhD; Jacques M.T. de Bakker, PhD; Lukas R.C. Dekker, MD, PhD; Andre C. Linnenbank, PhD; Mark G. Hoogendijk, MD; Ruben Coronel, MD, PhD; Jan G.P. Tijssen, PhD; Arthur A.M. Wilde, MD, PhD and Hanno L. Tan, MD, PhD

From the Cardiology (P.G.P., P.F.H.M.v.D., L.R.C.D., J.G.P.T., A.A.M.W., H.L.T.) and Experimental Cardiology/Heart Failure Research Center (J.M.T.d.B., A.C.L., M.G.H., R.C., A.A.M.W., H.L.T.), Academic Medical Center, University of Amsterdam; and Interuniversity Cardiology Institute of the Netherlands (J.M.T.d.B.), Amsterdam, The Netherlands.

Correspondence to Hanno L. Tan, MD, PhD, Department of Cardiology, Academic Medical Center, Meibergdreef 9, 1105AZ Amsterdam, The Netherlands. E-mail h.l.tan{at}amc.nl

Received May 11, 2008; accepted October 6, 2008.

Background— Brugada syndrome (BrS) is associated with lethal arrhythmias, which are linked to specific ST-segment changes (type-1 BrS-ECG) and the right ventricle (RV). The pathophysiological basis of the arrhythmias and type-1 BrS-ECG is unresolved. We studied the electrophysiological characteristics of the RV endocardium in BrS.

Methods and Results— RV endocardial electroanatomical mapping and stimulation studies were performed in controls (n=12) and BrS patients with a type-1 (BrS-1, n=10) or type-2 BrS-ECG (BrS-2, n=12) during the studies. BrS-1 patients had prominent impairment of RV endocardial impulse propagation when compared with controls, as represented by: (1) prolonged activation-duration during sinus rhythm (86±4 versus 65±3 ms), (2) increased electrogram fractionation (1.36±0.04 versus 1.15±0.01 deflections per electrogram), (3) longer electrogram duration (83±3 versus 63±2 ms), (4) activation delays on premature stimulation (longitudinal: 160±26 versus 86±9 ms; transversal: 112±5 versus 58±6 ms), and (5) abnormal transversal conduction velocity restitution (42±8 versus 18±2 ms increase in delay at shortest coupling intervals). Wider and more fractionated electrograms were also found in BrS-2 patients. Repolarization was not different between groups.

Conclusions— BrS-1 and BrS-2 patients are characterized by wide and fractionated electrograms at the RV endocardium. BrS-1 patients display additional conduction slowing during sinus rhythm and premature stimulation along with abnormal transversal conduction velocity restitution. These patients may thus exhibit a substrate for slow and discontinuous conduction caused by abnormal active membrane processes and electric coupling. Our findings support the emerging notion that BrS is not solely attributable to abnormal electrophysiological properties but requires the conspiring effects of conduction slowing and tissue discontinuities.

Key Words: arrhythmia • electrophysiology • mapping • Brugada syndrome • sudden cardiac death

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