Effect of coronary occlusion on arrhythmias and conduction in the ovine heart

1983 ◽  
Vol 245 (1) ◽  
pp. H82-H89 ◽  
Author(s):  
D. E. Euler ◽  
J. F. Spear ◽  
E. N. Moore
Keyword(s):  
Ventricular Tachycardia ◽  
Coronary Artery ◽  
Ventricular Fibrillation ◽  
Electrical Activity ◽  
Coronary Occlusion ◽  
Circumflex Coronary Artery ◽  
Pentobarbital Sodium ◽  
Normal Zone ◽  
Ventricular Tachycardia And Fibrillation ◽  
Observation Period

The proximal left circumflex coronary artery was occluded for 1 h in 16 open-chest sheep anesthetized with pentobarbital sodium. Epicardial conduction was monitored at three or four sites within the ischemic zone and one site in the normal zone. Eight of the sheep developed ventricular fibrillation within the first 15 min of occlusion; the remaining sheep survived the 1-h observation period. In the sheep that developed spontaneous ventricular fibrillation, the circumflex perfused a significantly greater amount of the left ventricle (44 +/- 3 vs. 39 +/- 3%; P = 0.008). The occurrence of spontaneous ventricular fibrillation was invariably preceded by a period of sustained (0.5-4 min) ventricular tachycardia. Six of the surviving sheep developed episodes of sustained (2-10 min) tachycardia that were self-terminating. The ischemic zone electrograms showed continuous fractionated electrical activity during both self-terminating tachycardias and tachycardias ending in fibrillation. The continuous epicardial electrical activity did not appear to cause the tachycardias but rather occurred as a result of the tachycardias. The genesis of ventricular tachycardia and fibrillation in this model may involve mechanisms different from ischemia-induced ventricular tachycardia and fibrillation in canine and porcine hearts.

Contrasting ischemic contraction patterns by zone and layer in canine myocardium

1982 ◽  
Vol 243 (6) ◽  
pp. H852-H855 ◽  
Author(s):  
S. Hattori ◽  
W. S. Weintraub ◽  
J. B. Agarwal ◽  
M. M. Bodenheimer ◽  
V. S. Banka ◽  
...  
Keyword(s):  
Coronary Artery ◽  
Left Ventricle ◽  
Fiber Orientation ◽  
Coronary Occlusion ◽  
Short Axis ◽  
Circumflex Coronary Artery ◽  
Left Circumflex Coronary Artery ◽  
Close Relationship ◽  
Canine Myocardium

The effect of graded coronary occlusion on myocardial shortening in different zones of the left ventricle is not clear. Therefore, in 15 dogs ultrasonic crystals were used to evaluate the effect of graded coronary occlusion on subendocardial and subepicardial contraction in both the left anterior descending coronary artery (LAD) and left circumflex coronary artery (Circ) distributions. Subepicardial shortening was evaluated along both the long and short axes. In the LAD zones, segment shortening decreased in parallel in the subendocardium and subepicardium. In the circumflex zone subendocardial and subepicardial long axis shortening fell off in parallel, while subepicardial short axis shortening fell off more rapidly. Thus there is a close relationship between endocardial and epicardial segment shortening following graded coronary occlusion. In the circumflex zone, however, fiber orientation may affect the measurement of segment motion.

Effect of arteriolar dilation on coronary artery diameter distal to coronary stenoses

1985 ◽  
Vol 249 (5) ◽  
pp. H981-H988 ◽  
Author(s):  
J. S. Schwartz ◽  
R. J. Bache
Keyword(s):  
Regression Analysis ◽  
Coronary Artery ◽  
Coronary Occlusion ◽  
Circumflex Coronary Artery ◽  
Intracoronary Injection ◽  
Open Chest ◽  
Close Relationship ◽  
Coronary Artery Diameter ◽  
Coronary Stenoses ◽  
Chronically Instrumented Dogs

Previous studies have suggested that worsening hemodynamic severity of coronary stenoses in response to distal arteriolar dilation may be related to dilation of the normal epicardial artery adjacent to the stenosis resulting in increasing percent stenosis. To test this hypothesis we used sonomicrometry to continuously measure external circumflex coronary artery diameter distal to snare stenoses of varying severity in 19 open-chest dogs and 5 awake, chronically instrumented dogs. Arteriolar dilation produced by release of a transient coronary occlusion or by intracoronary injection of adenosine caused a decrease in circumflex coronary diameter distal to the stenosis. Regression analysis showed that circumflex diameter and pressure distal to the stenosis were directly related (mean r: transient occlusion, 0.86 +/- 0.04; adenosine, 0.97 +/- 0.01). The close relationship between pressure and diameter suggests that the decrease in diameter in response to arteriolar dilation was a passive effect. Passive coronary narrowing distal to a stenosis suggests that a similar effect may occur within a compliant stenosis, thus partly explaining the increase in severity of compliant stenoses in response to arteriolar dilation.

Exercise training restores adenosine-induced relaxation in coronary arteries distal to chronic occlusion

2000 ◽  
Vol 278 (6) ◽  
pp. H1984-H1992 ◽  
Author(s):  
Cristine L. Heaps ◽  
Michael Sturek ◽  
Julie A. Rapps ◽  
M. Harold Laughlin ◽  
Janet L. Parker
Keyword(s):  
Coronary Artery ◽  
Exercise Training ◽  
Sodium Nitroprusside ◽  
Coronary Arteries ◽  
Coronary Occlusion ◽  
Circumflex Coronary Artery ◽  
Miniature Swine ◽  
Chronic Occlusion ◽  
Chronic Coronary Occlusion ◽  
Camp And Cgmp

We previously reported that canine collateral-dependent coronary arteries exhibit impaired relaxation to adenosine but not sodium nitroprusside. In contrast, exercise training enhances adenosine sensitivity of normal porcine coronary arteries. These results stimulated the hypothesis that chronic coronary occlusion and exercise training produce differential effects on cAMP- versus cGMP-mediated relaxation. To test this hypothesis, Ameroid occluders were surgically placed around the proximal left circumflex coronary artery (LCx) of female Yucatan miniature swine 8 wk before initiating sedentary or exercise training (treadmill run, 16 wk) protocols. Relaxation to the cAMP-dependent vasodilators adenosine (10− 7 to 10− 3 M) and isoproterenol (3 × 10− 8 to 3 × 10− 5 M) were impaired in collateral-dependent LCx versus nonoccluded left anterior descending (LAD) arterial rings isolated from sedentary but not exercise-trained pigs. Furthermore, adenosine-mediated reductions in simultaneous tension and myoplasmic free Ca2+ were impaired in LCx versus LAD arteries isolated from sedentary but not exercise-trained pigs. In contrast, relaxation in response to the cAMP-dependent vasodilator forskolin (10− 9 to 10− 5 M) and the cGMP-dependent vasodilator sodium nitroprusside (10− 9 to 10− 4 M) was not different in LCx versus LAD arteries of sedentary or exercise-trained animals. These data suggest that chronic occlusion impairs receptor-dependent, cAMP-mediated relaxation; receptor-independent cAMP- and cGMP-mediated relaxation were unimpaired. Importantly, exercise training restores cAMP-mediated relaxation of collateral-dependent coronary arteries.

Antifibrillatory effects of α1-adrenoceptor blocking drugs in experimental coronary artery occlusion and reperfusion

1993 ◽  
Vol 71 (2) ◽  
pp. 103-111 ◽  
Author(s):  
B. G. Benfey
Keyword(s):  
Coronary Artery ◽  
Ventricular Fibrillation ◽  
Guinea Pig ◽  
Ventricular Arrhythmias ◽  
Coronary Occlusion ◽  
Coronary Artery Occlusion ◽  
Artery Occlusion ◽  
Coronary Reperfusion ◽  
Isolated Hearts ◽  
Anesthetized Dogs

The myocardium of animals and man possesses α1-adrenoceptors in addition to β-adrenoceptors. Ischemia increases sympathetic tone, and ventricular arrhythmias can occur by β- and α1-adrenoceptor stimulation. I believe that α1-adrenoceptor blocking drugs have antifibrillatory effects and will review the data that support this condition. The effect of α1,-adrenoceptor blocking drugs on the incidence of ventricular fibrillation in acute coronary artery occlusion and (or) reperfusion has been determined in 24 studies in conscious and anesthetized dogs and rats, anesthetized cats and pigs, and rat and guinea-pig isolated hearts. The drugs reduced the incidence of fibrillation from 35 to 24% in coronary occlusion and from 61 to 29% in reperfusion.Key words: heart, coronary occlusion, coronary reperfusion, ventricular fibrillation, α1-adrenoceptor blocking drugs.

Purkinje involvement in arrhythmias after coronary artery reperfusion

2002 ◽  
Vol 282 (4) ◽  
pp. H1189-H1196 ◽  
Author(s):  
David O. Arnar ◽  
James B. Martins
Keyword(s):  
Ventricular Tachycardia ◽  
Coronary Artery ◽  
Ventricular Fibrillation ◽  
Cycle Length ◽  
Ischemic Myocardium ◽  
Risk Zone ◽  
Purkinje System ◽  
Mean Cycle

Previous studies have indicated that the endocardium may be responsible for a large portion of ventricular tachycardia (VT) seen with reperfusion of ischemic myocardium. To evaluate the role of the Purkinje system in nonreentrant VT arising from the endocardium after reperfusion, the anterior descending coronary artery was occluded for 20 min and then reperfused in 23 dogs after instrumentation of the risk zone with 21 multipolar plunge needles. VT with focal Purkinje origin was defined as a focal endocardial VT with Purkinje potentials recorded before the earliest endocardial myopotential. A total of 19 VTs (mean cycle length 214 ± 2 ms) were observed with 11 (58%) having focal Purkinje origin. Fifty-eight percent of the VTs degenerated to ventricular fibrillation, with occurrences of two or more independent foci per complex (seen in 7 of 11 compared with 1 of 8 nonsustained VTs). In conclusion, these data show that Purkinje tissue may be important in the genesis of reperfusion VT.

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