Sustained regional dysfunction produced by prolonged coronary stenosis: gradual recovery after reperfusion.

Abstract

Prolonged nontransmural ischemia was produced and the early and late effects of reperfusion were studied in 10 conscious dogs instrumented over the long term. Five hours of partial circumflex coronary artery-stenosis was produced with a hydraulic occluder, followed by gradual release over 20 min, with measurements of left ventricular pressure, regional myocardial function (systolic wall thickening by sonomicrometry), coronary blood flow velocity (pulsed Doppler), and myocardial blood flow (microspheres). During coronary stenosis the occluder was adjusted frequently to maintain a reduction of systolic wall thickening to 50% to 75% of control (average 62.6% of control). Myocardial blood flow in the ischemic area at 4 hr of partial coronary stenosis was reduced in the inner layers of the myocardium (subendocardium, from 0. 170-182, 1983. WITH the advent of surgical and nonsurgical revascularization of ischemic myocardium in man, coronary artery reperfusion has become an important therapeutic intervention. Many investigators" have reported the effects of reperfusion on ischemic myocardium after various periods of total coronary occlusion, but the value of this intervention remains controversial. The question of whether or not prolonged but revers- 170ible myocardial ischemic dysfunction can occur without coronary occlusion has also remained unexamined. In addition, despite recent clinical experience with coronary artery reperfusion by clot lysis or surgical means after acute myocardial infarction,9-there is little information on recovery of contractile function in zones that are partially perfused and exhibit nontransmural myocardial ischemia. In this study we investigated the effects of reperfusion on myocardial function and blood flow distribution over a 7 day period after 5 hr of partial coronary stenosis in conscious dogs instrumented over the long term. MethodsTen adult mongrel dogs weighing 22.1 to 39.6 kg (mean 28.4) were premedicated with acepromazine maleate (0.5 mg/ CIRCULATION

Changes in the response of hibernated myocardium to inotropic stimulation after angioplasty: A doppler myocardial imaging study

“…In the other studies, slight improvement following revascularization was noticed even months after the procedure. [20][21][22] Similar observations concerning contractility at rest were made based on the analysis of systolic velocity in CDMI studies. A detected mild increase of velocities directly after angioplasty without any further improvement parallels the observed relatively small improvement of global contractility at rest.…”

Medical and Cellular Implications of Stunning, Hibernation, and Preconditioning

“…Stunning generally ensues on the relief of the ischemia, complicating the interpretation of the recovery time course. 158 Such acute compensation to low-grade ischemia is not universally observed and, when it does occur, appears to be operative over a very limited perfusion range. 105 Nevertheless, the pathophysiology of such acute low-flow ischemia is consistent with the teleological notion that hibernating myocardium can downregulate its function (and thus its energy demand) so as to offset the otherwise lethal consequences of limited perfusion (Fig 2A).…”

Effect of the combination of diltiazem and atenolol on exercise-induced regional myocardial ischemia in conscious dogs.

“…The heart was removed, the left and right coronary arteries were flushed gently with saline followed by formalin, and the heart was placed in 10% formalin for 3 to 5 days to facilitate sectioning by techniques previously described. 23 . On the first evaluation day (7 days after surgery), brief coronary occlusion caused severe dysfunction in the ischemic area, but as time passed dysfunction of the ischemic wall during coronary occlusion gradually diminished and reactive hyperemia also decreased progressively, indicating collateral development.…”