Bimodal relationship between sinus node arterial distension and sinus nodal automaticity.
In the isolated buffer perfused canine sinus node the effect of either an increase or decrease in perfusion rate (PR), and hence sinus node (SN) arterial pressure (PSNA), on the frequency of sinus nodal depolarization (SDF) is bimodal. SDF decreased from 121.9 +/- 6.1 to 101.4 +/- 6.0 depolarizations/min as PR and PSNA increased from 1 to 4 ml/min and from 18.7 +/- 3.8 to 45.1 +/- 7.3 mmHg, respectively. Further increasing PR from 4 to 10 ml/mn (PSNA increasing from 45.1 +/- 7.3 to 94.0 +/- 14.1 mmHg) caused SDF to increase from 101.4 +/- 6.0 to 121.0 +/- 7.4 depolarizations/min. With respect to the PR, SDF is logarithmically related to the relative degree to which the SN artery is distended, the degree of SN arterial distension being determined by the change in SN arterial resistance (R) with respect to PR (dR/dPR). This relationship is defined by the equation: SDF = 9.23 1n(--dR/dPR) + 99.7. While these results support the existence of a mechanism for autoregulation of sinus nodal automaticity, they indicate that it is considerably more complex than previously envisioned.
D000818:Animals; D003326:Coronary Circulation; D004285:Dogs; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D008465:Mechanoreceptors / Q000502:physiology; D009200:Myocardial Contraction; D010477:Perfusion; D011312:Pressure; D012849:Sinoatrial Node / Q000502:physiology*