Heart rhythm : the official journal of the Heart Rhythm Society
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The main physiologic function of the AV junction is control of timing between atrial and ventricular excitation. However, under pathologic conditions, the AV junction may become the pacemaker of the heart. Unlike the well-characterized sinoatrial node (SAN), autonomic control of the AV junctional pacemaker has not been studied. ⋯ AV junctional rhythm can be autonomically modulated with subthreshold stimulation to produce junctional rates of 145 +/- 16 bpm (cycle length 412 +/- 29 ms), similar to sinus rates in rabbit. Unlike the SAN, the anatomic location of the AV junctional pacemaker is stable during autonomic modulation.
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Genetic testing in long QT syndrome (LQTS) is moving from research into clinical practice. We have recently piloted a molecular genetics program in a New Zealand research laboratory with a view to establishing a clinical diagnostic service. ⋯ The spectrum of New Zealand LQTS and Brugada mutations is similar to previous studies. The high proportion of novel mutations (40%) dictates a need to confirm pathogenicity for locally prevalent mutations. Careful screening selection criteria, cellular functional analysis of novel mutations, and development of locally relevant control sample cohorts will all be essential to establishing regional diagnostic services.