title: Ventricular fibrillation thresholds in Langendorff perfused rabbit hearts: all or none effect of low potassium concentration.
abstract: The median single pulse ventricular fibrillation threshold of 56 determinations in eight isolated rabbit hearts perfused with a Krebs-Henseleit solution was 36 mA, with a range from 12.5 to above 50 mA. The fibrillation threshold remained in the same range when the potassium concentration in the perfusing fluid was decreased from its normal 5.6 mmol.litre-1 to as low as 1.8 mmol.litre-1. A further decrease in potassium concentration reduced the fibrillation threshold to a median value of 1.6 mA in nine determinations on six hearts. With a 1.6 mmol.litre-1 potassium concentration, thresholds were in either the high or the low range depending on the individual heart. A pronounced shortening of refractory period and an earlier vulnerable period were associated with the sharp change in fibrillation threshold; the diastolic extrasystolic threshold, cycle length, and RT interval duration increased in a more linear manner as the potassium concentration was lowered.
mesh_terms: D000818:Animals; D006321:Heart / Q000503:physiopathology*; D066298:In Vitro Techniques; D010477:Perfusion; D011188:Potassium / Q000494:pharmacology*; D011817:Rabbits; D012684:Sensory Thresholds / Q000187:drug effects / Q000502:physiology*; D013997:Time Factors; D014693:Ventricular Fibrillation / Q000503:physiopathology*
chemical_list: D011188:Potassium