Functional integrity of sympathetic efferent postganglionic axons in a region of stunned myocardium.
In order to investigate whether brief, repeated episodes of acute myocardial ischemia impair the function of the intrinsic sympathetic efferent post ganglionic cardiac nerves, 12 cycles of left anterior descending coronary artery occlusions (5 mins) and reperfusions (10 mins) were successfully performed in 10 dogs. Following each brief occlusion percentage systolic shortening in the ventral myocardium was reduced, consistent with myocardial stunning. Stellate ganglion stimulation increased intramyocardial pressures in the ventral and lateral regions of the left ventricle before and after each of the artery occlusions in which stimulations were performed. Isoproterenol and tyramine also augmented intramyocardial pressures in those regions. When the coronary artery was occluded permanently in seven of the dogs tested, stellate ganglion stimulation continued to augment intramyocardial pressure in the ventral region of the left ventricle for up to 35 mins. These results indicate that following repetitive episodes of brief occlusion of a coronary artery that are reported to 'stun' the involved myocardium in a transmural distribution, sympathetic efferent post ganglionic axons can augment inotropism in the affected zone. Furthermore, when a coronary artery is totally occluded thereafter for up to 35 mins these efferent sympathetic post ganglionic nerves continue to function. It is concluded that sympathetic efferent post ganglionic neurons innervating the ventricle can augment cardiac inotropism in a region of stunned myocardium.
Johnstone
D E
DE
Department of Medicine, Dalhousie University Halifax, Nova Scotia.
Janes
R D
RD
Klassen
G A
GA
Armour
J A
JA
D000818:Animals; D001338:Autonomic Fibers, Postganglionic / Q000502:physiology*; D001369:Axons / Q000502:physiology*; D004285:Dogs; D004525:Efferent Pathways / Q000503:physiopathology; D004558:Electric Stimulation; D005260:Female; D005728:Ganglia, Sympathetic / Q000503:physiopathology; D006321:Heart / Q000294:innervation*; D007545:Isoproterenol / Q000008:administration & dosage; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects; D009203:Myocardial Infarction / Q000503:physiopathology*; D013564:Sympathetic Nervous System / Q000503:physiopathology*; D014439:Tyramine / Q000008:administration & dosage; D014693:Ventricular Fibrillation / Q000503:physiopathology
D007545:Isoproterenol; D014439:Tyramine