[Dual chamber rate responsive pacing and chronotropic insufficiency. Comparison of double and respiratory sensors].

Late responsive DDD pacemakers are the most technically advanced devices presently available. These pacemakers are particularly useful in patients with chronotropic insufficiency when the sinus node is incapable of accelerating during exercise. The latest pacemakers have two sensors to reproduce optimal physiological sinus acceleration.

Tyrosine kinase and protein kinase C regulate L-type Ca(2+) current cooperatively in human atrial myocytes.

The effects of tyrosine protein kinases (TK) on the L-type Ca(2+) current (I(Ca)) were examined in whole cell patch-clamped human atrial myocytes. The TK inhibitors genistein (50 microM), lavendustin A (50 microM), and tyrphostin 23 (50 microM) stimulated I(Ca) by 132 +/- 18% (P < 0.001), 116 +/- 18% (P < 0.

Regulation of the transient outward K(+) current by Ca(2+)/calmodulin-dependent protein kinases II in human atrial myocytes.

Ca(2+)/calmodulin-dependent protein kinases II (CaMKII) have important functions in regulating cardiac excitability and contractility. In the present study, we examined whether CaMKII regulated the transient outward K(+) current (I(to)) in whole-cell patch-clamped human atrial myocytes. We found that a specific CaMKII inhibitor, KN-93 (20 micromol/L), but not its inactive analog, KN-92, accelerated the inactivation of I(to) (tau(fast): 66.