Role of calcium and the calcium channel in the initiation and maintenance of ventricular fibrillation

J. C. Merillat, Edward Lakatta, O. Hano, T. Guarnieri

Research output: Contribution to journalArticle

Abstract

The cellular events during the initiation and maintenance of ventricular fibrillation (VF) are poorly understood. We developed a nonischemic, isolated, perfused rabbit Langendorff preparation in which sustained VF could be induced by alternating current (AC) and which allowed changes in perfusate composition. We also used Na+-K+ pump inhibition (10 μM ouabain or K+-free perfusate) to induce VF. AC stimulation or Na+-K+ pump inhibition always initiated VF. Calcium channel blockade by verapamil or nitrendipine uniformly inhibited the initiation of VF in both models. During Na+-K+ pump inhibition, 1) VF was prevented by calcium channel blockade, despite evidence of Ca2+ overload, and 2) abolition of spontaneous sacroplasmic reticulum-generated cytosolic Ca2+ oscillations by ryanodine or Na+ channel blockade with tetrodotoxin did not prevent VF initiation. Lowering extracellular [Ca2+] to 80 μM uniformly prevented the initiation of VF due to Na+-K+ pump inhibition but not that due to AC stimulation. VF maintenance also was studied using 1) reduction in perfusate [Ca2+], 2) blockade of Ca2+ channels, or 3) electrical defibrillation. Decreasing the perfusate [Ca2+] to 80 μM resulted in defibrillation during VF whether induced by AC or Na+-K+ pump inhibition. Verapamil or nitrendipine also resulted in defibrillation regardless of the initiation method. Electrical defibrillation was successful only in AC-induced VF. The results demonstrate that VF can be initiated and maintained in a nonischemic rabbit Langendorff preparation. The data suggest that increases in slow channel Ca2+ flux, as opposed to increases in cytosolic Ca2+ per se, were necessary for the initiation and maintenance of VF. The data, however, do not exclude an important role for cytosolic Ca2+ in the modulation of VF.

Original languageEnglish (US)
Pages (from-to)1115-1123
Number of pages9
JournalCirculation Research
Volume67
Issue number5
StatePublished - 1990

Fingerprint

Ventricular Fibrillation
Calcium Channels
Maintenance
Calcium
Nitrendipine
Verapamil
Rabbits
Ryanodine
Reticulum
Tetrodotoxin
Ouabain

Keywords

  • arrhythmia mechanism
  • calcium channels
  • calcium overload
  • defibrillation
  • glycoside toxicity
  • ventricular fibrillation

ASJC Scopus subject areas

  • Physiology
  • Cardiology and Cardiovascular Medicine

Cite this

Role of calcium and the calcium channel in the initiation and maintenance of ventricular fibrillation. / Merillat, J. C.; Lakatta, Edward; Hano, O.; Guarnieri, T.

In: Circulation Research, Vol. 67, No. 5, 1990, p. 1115-1123.

Research output: Contribution to journalArticle

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abstract = "The cellular events during the initiation and maintenance of ventricular fibrillation (VF) are poorly understood. We developed a nonischemic, isolated, perfused rabbit Langendorff preparation in which sustained VF could be induced by alternating current (AC) and which allowed changes in perfusate composition. We also used Na+-K+ pump inhibition (10 μM ouabain or K+-free perfusate) to induce VF. AC stimulation or Na+-K+ pump inhibition always initiated VF. Calcium channel blockade by verapamil or nitrendipine uniformly inhibited the initiation of VF in both models. During Na+-K+ pump inhibition, 1) VF was prevented by calcium channel blockade, despite evidence of Ca2+ overload, and 2) abolition of spontaneous sacroplasmic reticulum-generated cytosolic Ca2+ oscillations by ryanodine or Na+ channel blockade with tetrodotoxin did not prevent VF initiation. Lowering extracellular [Ca2+] to 80 μM uniformly prevented the initiation of VF due to Na+-K+ pump inhibition but not that due to AC stimulation. VF maintenance also was studied using 1) reduction in perfusate [Ca2+], 2) blockade of Ca2+ channels, or 3) electrical defibrillation. Decreasing the perfusate [Ca2+] to 80 μM resulted in defibrillation during VF whether induced by AC or Na+-K+ pump inhibition. Verapamil or nitrendipine also resulted in defibrillation regardless of the initiation method. Electrical defibrillation was successful only in AC-induced VF. The results demonstrate that VF can be initiated and maintained in a nonischemic rabbit Langendorff preparation. The data suggest that increases in slow channel Ca2+ flux, as opposed to increases in cytosolic Ca2+ per se, were necessary for the initiation and maintenance of VF. The data, however, do not exclude an important role for cytosolic Ca2+ in the modulation of VF.",
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