Mechanical determinants of coronary blood flow during dynamic alterations in myocardial contractility

1993 ◽  
Vol 265 (4) ◽  
pp. H1112-H1118 ◽  
Author(s):  
L. J. Mulligan ◽  
D. Escobedo ◽  
G. L. Freeman
Keyword(s):  
Blood Flow ◽  
Coronary Blood Flow ◽  
Average Rate ◽  
Left Ventricular ◽  
Cardiac Contraction ◽  
Ventricular Elastance ◽  
Pulsus Alternans ◽  
Pressure Development ◽  
Maximal Pressure ◽  
And Control

Recently it has been proposed that the decrease in coronary blood flow (CBF) resulting from cardiac contraction referred to as systolic flow impediment (SFI) is dependent on the level of left ventricular elastance (Ees). The average rate of LV relaxation (Ravg) has been shown to be major determinant of diastolic flow development (DFD). We tested these hypotheses using the unique hemodynamic condition of pulsus alternans (PA) where end-systolic LV pressure and instantaneous Ees vary on beat-to-beat basis. In six mongrel dogs instrumented with LV and aortic manometers, ultrasonic dimension crystals, and Doppler coronary flow probes we measured phasic CBF and Ees during PA and control conditions. Maximal pressure development over time (dP/dtmax) and SFI were significantly different between weak (WB) and strong beats (SB) as were Ravg and DFD. Minimum CBF (Qmin) was not different between SB and WB; however, Qmin and peak Ees occurred nearly simultaneously in the WB. Qmin occurred much earlier than peak Ees in the strong and control beats. Plots of instantaneous LV elastance and CBF showed that for control beats and for the strong beats of PA CBF was similar during systole and diastole, suggesting elastance is a unique determinant of CBF. This was quantified as CBF at the time in either systole or diastole when elastance was half-maximal for that beat (E50). During the WB of PA, however, CBF at E50 was significantly higher during systole than during diastole. We conclude that while SFI and DFD are highly dependent on the dP/dt and Ravg, Ees is not a unique determinant of CBF under all conditions.

scholarly journals Quantitative analysis of exercise-induced enhancement of early- and late-systolic retrograde coronary blood flow

2010 ◽  
Vol 108 (3) ◽  
pp. 507-514 ◽  
Author(s):  
Shawn B. Bender ◽  
Marc J. van Houwelingen ◽  
Daphne Merkus ◽  
Dirk J. Duncker ◽  
M. Harold Laughlin
Keyword(s):  
Blood Flow ◽  
Coronary Blood Flow ◽  
Cardiac Cycle ◽  
Cardiac Contractility ◽  
Left Ventricular ◽  
Dynamic Exercise ◽  
Cardiac Contraction ◽  
Cycle Duration ◽  
Exercise Induced ◽  
Coronary Tone

Coronary blood flow (CBF) is reduced and transiently reversed during systole via cardiac contraction. Cardiac contractility, coronary tone, and arterial pressure each influence systolic CBF (CBFSYS), particularly by modulating the retrograde component of CBFSYS. The effect of concurrent changes in these factors on CBFSYS during dynamic exercise has not been examined. Using chronically instrumented swine, we hypothesized that dynamic exercise enhances retrograde CBFSYS. Phasic CBF was examined at rest and during treadmill exercise [2–5 miles/h (mph)]. Absolute values of mean CBF over the cardiac cycle (CBFCYCLE) as well as mean CBF in diastole (CBFDIAS) and mean CBFSYS were increased by exercise, while relative CBFDIAS and CBFSYS expressed as percentage of mean CBFCYCLE were principally unchanged. Early retrograde CBFSYS was present at rest and increased in magnitude (−33 ± 4 ml/min) and as a percent of CBFCYCLE (−0.6 ± 0.1%) at 5 mph. This reversal was transient, comprising 3.7 ± 0.3% of cardiac cycle duration at 5 mph. Our results also reveal that moderately intense exercise (>3 mph) induced a second CBF reversal in late systole before aortic valve closure. At 5 mph, late retrograde CBFSYS amounted to −53 ± 11 ml/min (−3.1 ± 0.7% of CBFCYCLE) while occupying 11.1 ± 0.3% of cardiac cycle duration. Wave-intensity analysis revealed that the second flow reversal coincided with an enhanced aortic forward-going decompression wave (vs. rest). Therefore, our data demonstrate a predictable increase in early-systolic CBF reversal during exercise and additionally that exercise induces a late-systolic CBF reversal related to the hemodynamic effects of left ventricular relaxation that is not predictable using current models of phasic CBF.

Desensitization of myocardial but not coronary VIP receptor-mediated responses in dogs

1988 ◽  
Vol 255 (3) ◽  
pp. H601-H607 ◽  
Author(s):  
F. L. Anderson ◽  
A. C. Kralios ◽  
R. Hershberger ◽  
M. R. Bristow
Keyword(s):  
Blood Flow ◽  
Coronary Blood Flow ◽  
Left Ventricular ◽  
Before And After ◽  
Pressure Development ◽  
Heterologous Desensitization ◽  
Group A ◽  
Homologous Desensitization ◽  
Isoproterenol Infusion ◽  
Canine Myocardium

Desensitization to the hemodynamic effects of vasoactive intestinal polypeptide (VIP) was examined in 12 anesthetized, open-chest dogs in which cardiac output, systemic arterial resistance, and heart rate were fixed. VIP was administered by intracoronary infusion, and the effects were compared with isoproterenol and forskolin. Measurements of left ventricular maximum rate of pressure development (dP/dt), coronary blood flow, and myocardial oxygen consumption were made before and after a 90-min infusion of either isoproterenol (6 dogs) or VIP (6 dogs). After isoproterenol infusion, there was a significant decrease in the effect of isoproterenol on left ventricular dP/dt and coronary blood flow. The effects of VIP and forskolin were not changed. After VIP infusion, there was a significant decrease in the effect of VIP on left ventricular dP/dt with no change in the effects of isoproterenol and forskolin. In this group, a significant increase in coronary blood flow with minimal change in myocardial oxygen could still be elicited by VIP injection after VIP infusion. The agonist infusion time to achieve a decrease in inotropic effect was less for VIP when compared with isoproterenol. Thus these data demonstrate acute homologous desensitization of myocardial VIP and beta-adrenergic receptors in canine myocardium with no development of heterologous desensitization, desensitization involving the catalytic subunit of adenylate cyclase, or desensitization of the VIP-mediated primary coronary vasodilator response.

Effects of Elevated Coronary Sinus Pressure on Coronary Blood Flow and Left Ventricular Function

Circulation ◽  
1995 ◽  
Vol 92 (9) ◽  
pp. 298-303 ◽  
Author(s):  
Takuya Miura ◽  
Takeshi Hiramatsu ◽  
Joseph M. Forbess ◽  
John E. Mayer
Keyword(s):  
Blood Flow ◽  
Left Ventricular Function ◽  
Ventricular Function ◽  
Coronary Blood Flow ◽  
Coronary Sinus ◽  
Left Ventricular ◽  
Sinus Pressure

Contribution of extravascular compression to reduction of maximal coronary blood flow

1992 ◽  
Vol 262 (1) ◽  
pp. H68-H77
Author(s):  
F. L. Abel ◽  
R. R. Zhao ◽  
R. F. Bond
Keyword(s):  
Blood Flow ◽  
Coronary Blood Flow ◽  
Coronary Flow ◽  
Perfusion Pressure ◽  
Left Ventricular Pressure ◽  
Coronary Perfusion Pressure ◽  
Left Ventricular ◽  
Ventricular Pressure ◽  
Coronary Perfusion ◽  
Storage Site

Effects of ventricular compression on maximally dilated left circumflex coronary blood flow were investigated in seven mongrel dogs under pentobarbital anesthesia. The left circumflex artery was perfused with the animals' own blood at a constant pressure (63 mmHg) while left ventricular pressure was experimentally altered. Adenosine was infused to produce maximal vasodilation, verified by the hyperemic response to coronary occlusion. Alterations of peak left ventricular pressure from 50 to 250 mmHg resulted in a linear decrease in total circumflex flow of 1.10 ml.min-1 x 100 g heart wt-1 for each 10 mmHg of peak ventricular to coronary perfusion pressure gradient; a 2.6% decrease from control levels. Similar slopes were obtained for systolic and diastolic flows as for total mean flow, implying equal compressive forces in systole as in diastole. Increases in left ventricular end-diastolic pressure accounted for 29% of the flow changes associated with an increase in peak ventricular pressure. Doubling circumferential wall tension had a minimal effect on total circumflex flow. When the slopes were extrapolated to zero, assuming linearity, a peak left ventricular pressure of 385 mmHg greater than coronary perfusion pressure would be required to reduce coronary flow to zero. The experiments were repeated in five additional animals but at different perfusion pressures from 40 to 160 mmHg. Higher perfusion pressures gave similar results but with even less effect of ventricular pressure on coronary flow or coronary conductance. These results argue for an active storage site for systolic arterial flow in the dilated coronary system.

alpha-Adrenergic control of oxygen delivery to myocardium during exercise in conscious dogs

1982 ◽  
Vol 242 (5) ◽  
pp. H805-H809 ◽  
Author(s):  
G. R. Heyndrickx ◽  
P. Muylaert ◽  
J. L. Pannier
Keyword(s):  
Heart Rate ◽  
Blood Flow ◽  
Oxygen Consumption ◽  
Coronary Blood Flow ◽  
Coronary Sinus ◽  
Oxygen Delivery ◽  
Left Ventricular ◽  
Conscious Dogs ◽  
Adrenergic Blockade ◽  
Adrenergic Control

alpha-Adrenergic control of the oxygen delivery to the myocardium during exercise was investigated in eight conscious dogs instrumented for chronic measurements of coronary blood flow, left ventricular (LV) pressure, aortic blood pressure, and heart rate and sampling of arterial and coronary sinus blood. After alpha-adrenergic receptor blockade a standard exercise load elicited a significantly greater increase in heart rate, rate of change of LV pressure (LV dP/dt), LV dP/dt/P, and coronary blood flow than was elicited in the unblocked state. In contrast to the response pattern during control exercise, there was no significant change in coronary sinus oxygen tension (PO2), myocardial arteriovenous oxygen difference, and myocardial oxygen delivery-to-oxygen consumption ratio. It is concluded that the normal relationship between myocardial oxygen supply and oxygen demand is modified during exercise after alpha-adrenergic blockade, whereby oxygen delivery is better matched to oxygen consumption. These results indicate that the increase in coronary blood flow and oxygen delivery to the myocardium during normal exercise is limited by alpha-adrenergic vasoconstriction.

Alteration in myocardial oxygen balance during exercise after beta-adrenergic blockade in dogs

1980 ◽  
Vol 49 (1) ◽  
pp. 28-33 ◽  
Author(s):  
G. R. Heyndrickx ◽  
J. L. Pannier ◽  
P. Muylaert ◽  
C. Mabilde ◽  
I. Leusen
Keyword(s):  
Heart Rate ◽  
Blood Flow ◽  
Oxygen Consumption ◽  
Myocardial Blood Flow ◽  
Coronary Blood Flow ◽  
Coronary Sinus ◽  
Myocardial Oxygen Consumption ◽  
Left Ventricular ◽  
Adrenergic Blockade ◽  
Oxygen Balance

The effects of beta-adrenergic blockade upon myocardial blood flow and oxygen balance during exercise were evaluated in eight conscious dogs, instrumented for chronic measurements of coronary blood flow, left ventricular pressure, aortic blood pressure, heart rate, and sampling of arterial and coronary sinus venous blood. The administration of propranolol (1.5 mg/kg iv) produced a decrease in heart rate, peak left ventricular (LV) dP/dt, LV (dP/dt/P, and an increase in LV end-diastolic pressure during exercise. Mean coronary blood flow and myocardial oxygen consumption were lower after propranolol than at the same exercise intensity in control conditions. The oxygen delivery-to-oxygen consumption ratio and the coronary sinus oxygen content were also significantly lower. It is concluded that the relationship between myocardial oxygen supply and demand is modified during exercise after propranolol, so that a given level of myocardial oxygen consumption is achieved with a proportionally lower myocardial blood flow and a higher oxygen extraction.

Role of site of microsphere injection and catheter position on systemic and regional hemodynamics in rat

1984 ◽  
Vol 247 (1) ◽  
pp. H35-H39 ◽  
Author(s):  
I. Kobrin ◽  
M. B. Kardon ◽  
W. Oigman ◽  
B. L. Pegram ◽  
E. D. Frohlich
Keyword(s):  
Blood Flow ◽  
Coronary Blood Flow ◽  
Coronary Flow ◽  
Left Ventricular ◽  
Ventricular Catheter ◽  
Catheter Position ◽  
Flow Measurements ◽  
Conscious Rats ◽  
Anesthetized Rats ◽  
Regional Hemodynamics

The influences of the site of microsphere injection (intra-atrial vs. intraventricular) and positioning of the left ventricular catheter (aortoventricular vs. atrioventricular) on systemic, renal, and coronary hemodynamics were evaluated in anesthetized rats. The effect of anesthesia on aortoventricular catheter positioning was also evaluated. In anesthetized and open-chest preparations, the systemic and renal hemodynamics were not affected by catheter position or site of microsphere injection; however, myocardial blood flow was dependent on these variables. Variations in coronary blood flow were significantly greater when the catheter was in the aortoventricular position (34 +/- 3%) than with an atrioventricular catheter (11 +/- 2%, P less than 0.01), irrespective of whether the microspheres were injected into the atrium or ventricle. Comparison of anesthetized and conscious rats with aortoventricular catheter indicated lesser variability in coronary blood flow in the conscious rats (P less than 0.01). Therefore, the greater variability of coronary flow measurements in anesthetized rats was caused by the position of the cardiac catheter in the aortoventricular route. However, the variability caused by the aortoventricular catheter was much less in conscious rats. Therefore, coronary flow hemodynamic measurements (microsphere technique) are less variable when they are made in conscious rats.

Coronary hyperperfusion and myocardial metabolism in isolated and intact hearts

1987 ◽  
Vol 253 (5) ◽  
pp. H1271-H1278 ◽  
Author(s):  
W. P. Miller ◽  
N. Shimamoto ◽  
S. H. Nellis ◽  
A. J. Liedtke
Keyword(s):  
Blood Flow ◽  
Fatty Acid ◽  
Coronary Blood Flow ◽  
Myocardial Metabolism ◽  
Left Ventricular ◽  
Coronary Perfusion ◽  
Rat Hearts ◽  
Heart Preparation ◽  
Significant Change ◽  
Lv Volume

We determined the independent influence of coronary hyperperfusion on myocardial metabolism in isolated and intact hearts. In an isovolumic blood-perfused rat heart preparation working against a left ventricular (LV) balloon, the effect of increasing coronary perfusion pressure from 100 to 150 mmHg was assessed. In three groups of rat hearts LV volume was fixed to obtain LV peak pressures of 42 +/- 3, 101 +/- 5, and 130 +/- 6 mmHg. With coronary hyperperfusion, LV pressure increased 27, 18, and 16%, LV maximum time derivative of pressure (dP/dt) increased 39, 20, and 22%, and myocardial O2 consumption (VO2) increased 16, 17, and 33%, respectively. In a fourth group, LV peak pressure was held constant at 92 +/- 4 mmHg during coronary hyperperfusion by decreasing LV volume. In this group, despite an increase in coronary blood flow of 48%, there was no significant difference in LV maximum dP/dt or myocardial VO2. Thus, in isolated rat hearts, coronary hyperperfusion was not an independent stimulus to myocardial VO2. To further test this, the effect of coronary hyperperfusion on myocardial metabolism was studied in an intact working swine heart preparation where the cardiac output was fixed with a right heart bypass circuit. Fatty acid oxidation in the left anterior descending bed was assessed by production of 14CO2 from [14C(U)]palmitate. A comparison of coronary perfusion 106 +/- 5 vs. 197 +/- 5 mmHg resulted in no significant change in global LV function, including LV internal diameter. Despite a 70% increase in coronary blood flow, there was no significant change in myocardial VO2 or fatty acid utilization.(ABSTRACT TRUNCATED AT 250 WORDS)

Ventricular remodeling induced by acute nonocclusive constriction of coronary artery in rats

1989 ◽  
Vol 257 (6) ◽  
pp. H1983-H1993 ◽  
Author(s):  
J. M. Capasso ◽  
M. W. Jeanty ◽  
T. Palackal ◽  
G. Olivetti ◽  
P. Anversa
Keyword(s):  
Blood Flow ◽  
Coronary Artery ◽  
Coronary Blood Flow ◽  
Wall Thickness ◽  
Ventricular Remodeling ◽  
Diastolic Pressure ◽  
Cell Damage ◽  
Left Ventricular ◽  
Consistent Difference ◽  
Luminal Diameter

To determine the consequence of acute nonocclusive constriction of the epicardial coronary artery on the adaptation of the left ventricle and its impact as a function of age, the left main coronary artery was narrowed in rats 4 and 12 mo of age, and the animals were killed 45 min later. Similar reductions in the luminal diameter, averaging 4%, were obtained in both groups of animals, and this change resulted in an increase in left ventricular end-diastolic pressure and a decrease in positive and negative change in pressure overtime (dP/dt) and in peak-developed ventricular pressure. Left ventricular volume increased by 66% and 56% at 4 and 12 mo because of increases in both the longitudinal and transverse chamber diameters. In contrast, wall thickness decreased by 27% and 35%, whereas sarcomere length increased only by 8.0% and 6.0%, respectively. These changes implied the occurrence of side-to-side slippage of myocytes within the wall to accommodate the larger chamber volume. The alterations in myocardial performance combined with the variations in ventricular size and wall thickness produced a marked elevation in diastolic and systolic wall stress. Moreover, myocyte cell damage in the form of contraction bands and disorganization of the intercalated disc region was seen. No consistent difference was found in any of the parameters measured as a function of age. Measurements of resting coronary blood flow across the left ventricular wall before coronary artery narrowing were comparable with those obtained 45 min after constriction. In conclusion, acute nonocclusive coronary artery stenosis has profound detrimental effects on the function and structure of the myocardium in the absence of an impairment of resting coronary blood flow.

Coronary smooth muscle reactivity to muscarinic stimulation after ischemia-reperfusion in porcine myocardial infarction

2003 ◽  
Vol 95 (1) ◽  
pp. 81-88 ◽  
Author(s):  
Antonio Rodríguez-Sinovas ◽  
Josep Bis ◽  
Inocencio Anivarro ◽  
Javier de la Torre ◽  
Antoni Bayés-Genís ◽  
...  
Keyword(s):  
Blood Flow ◽  
Smooth Muscle ◽  
Coronary Artery ◽  
Coronary Blood Flow ◽  
Ischemia Reperfusion ◽  
Left Ventricular ◽  
Severe Left Ventricular Dysfunction ◽  
Coronary Smooth Muscle

This study tested whether ischemia-reperfusion alters coronary smooth muscle reactivity to vasoconstrictor stimuli such as those elicited by an adventitial stimulation with methacholine. In vitro studies were performed to assess the reactivity of endothelium-denuded infarct-related coronary arteries to methacholine ( n = 18). In addition, the vasoconstrictor effects of adventitial application of methacholine to left anterior descending (LAD) coronary artery was assessed in vivo in pigs submitted to 2 h of LAD occlusion followed by reperfusion ( n = 12), LAD deendothelization ( n = 11), or a sham operation ( n = 6). Endothelial-dependent vasodilator capacity of infarct-related LAD was assessed by intracoronary injection of bradykinin ( n = 13). In vitro, smooth muscle reactivity to methacholine was unaffected by ischemia-reperfusion. In vivo, baseline methacholine administration induced a transient and reversible drop in coronary blood flow (9.6 ± 4.6 to 1.9 ± 2.6 ml/min, P < 0.01), accompanied by severe left ventricular dysfunction. After ischemia-reperfusion, methacholine induced a prolonged and severe coronary blood flow drop (9.7 ± 7.0 to 3.4 ± 3.9 ml/min), with a significant delay in recovery ( P < 0.001). Endothelial denudation mimics in part the effects of methacholine after ischemia-reperfusion, and intracoronary bradykinin confirmed the existence of endothelial dysfunction. Infarct-related epicardial coronary artery shows a delayed recovery after vasoconstrictor stimuli, because of appropriate smooth muscle reactivity and impairment of endothelial-dependent vasodilator capacity.

Sign in / Sign up

Export Citation Format

Share Document