Videodensitometry of the margins of the fluoroscopic image of the left ventricle (LV) was used to evaluate LV wall motion and differentiation of the wall motion signal reflected velocity of LV contraction (dV/dt) during various inotropic interventions in six anesthetized dogs. During these interventions heart rate, afterload and preload were maintained constant. Alterations in dV/dt were similar to changes in simultaneously measured LV peak dP/dt and the quotient of dP/dt and developed LV pressure, two widely accepted parameters of LV contractile state. Wide variations in preload and afterload caused no significant changes in dV/dt. Thus, the current study indicates that fluoroscopic videodensitometry provides a specific and reliable noninvasive method for evaluating LV contractile state.

Absorptiometry, Photon↗

PubMedDate not supplied

Comparative efficacy of coronary vasodilatory methods.

The relative efficacy and sequelae of several coronary vasodilator methods were compared in dogs. Maximal coronary vasodilation with least apparent side effect was achieved with infusion of adenosine triphosphate (ATP) at the rate of approximately 600 microng/minute (approximately 20 microng/kg/minute). This method increased conductance to 7 to 8 times control levels and may have fully depleted vasodilator reserve. Bolus injections of ATP or papaverine alone increased conductances three to four fold and approximated the effects of 15 seconds of occlusion of the circumflex coronary artery. Duration of effect was variable. Diatrizoate injections were somewhat less effective vasodilators and produced greater electrocardiographic and systemic effects. Bolus injections of mixtures of ATP and papaverine demonstrated additive effects, and increased conductance 5 to 6 times control levels. In further exploring the diagnostic value of vasodilatory redistribution of myocardial blood flow or appearance of collateral circulation as a sign of a hemodynamically significant stenosis, selective intracoronary infusion of ATP is a promising vasodilatory method.

Adenosine Triphosphate↗

PubMedDate not supplied

Comparative hemodynamic effects of coronary vasodilators and contrast material on the normal and ischemic canine myocardium: determination of the optimal agent for clinical augmentation of coronary blood flow.

The systemic hemodynamic and myocardial effects of potent vasodilators administered directly into the left coronary artery were determined and compared with the actions of contrast material in 10 anesthetized dogs in the normal state and in the presence of segmental myocardial ischemia. Contrast material (Renografin 76) caused systemic hypotension, rise in left ventricular diastolic pressure and decreases in LV dp/dt and dp/dt/LVP in both states. Doses of ATP (7.2 microgram/kg and 20 microgram/kg/min) which are maximally effective in augmenting coronary blood flow caused only mild arterial hypotension and minimal inotropic effects in both states. Nitroglycerin (3 microgram/kg and 10 microgram/kg/min) induced no inotropic effects but slightly greater arterial hypotension than ATP in both states. On the other hand, papaverine HCl (300 microgram/kg and 800 microgram/kg/min) induced profound increases in LV dp/dt and dp/dt/LVP, decreases in LVEDP and arterial hypotension in the non-ischemic state. In the presence of segmental ischemia, papaverine HCl caused significantly less increases in LV dp/dt and dp/dt/LVP, paradoxical increases in LVEDP in 5 dogs and ventricular fibrillation in 3 dogs. Thus, maximally effective vasodilatory doses of ATP causes only small alterations in hemodynamics and myocardial contractile state of the normal and ischemic heart. Similar doses of papaverine induce profound positive inotropic effects which are apparently deleterious to the ischemic heart.

Adenosine Triphosphate↗

PubMedDate not supplied

Effects of contrast material on dimensions and hemodynamics of the newborn heart: a study in conscious newborn lambs.

Injections of contrast material (Hypaque M-75%) and normal saline into the left ventricle (LV) of 1- to 3-month-old conscious lambs, during continuous monitoring of LV internal dimensions and pressures, revealed instaneous increases in LV end diastolic and end systolic volumes and LV end diastolic pressure. After contrast material, these alterations were sustained. Contrast injections were also accompanied by a mild depression in LV contractile state (dp/dt/P), systemic vasodilatation and persistent augmentation of cardiac output. The immediate effects on LV dimensions are primarily a consequence of acute volume expansion of the LV by the injection while the sustained changes likely reflect an expanded intravascular volume.

Animals↗

PubMedDate not supplied

Detection, quantitation and contrast enhancement of myocardial infarction utilizing computerized axial tomography: comparison with histochemical staining and 99mTc-pyrophosphate imaging.

The potential role of the CAT scan in detecting and quantitating acute myocardial infarctions was assessed in the excised hearts of 25 dogs with 48-hour-old myocardial infarctions. The CAT scan detected the infarct in every instance and distinguished subendocardial from transmural infarctions. While the CAT scan slightly underestimated the volume of infarcted tissue, this volume had a close linear relationship to the true volume determined by histochemical staining. On the other hand, the 99mTc-pyrophosphate scintiscans grossly overestimated the volume of infarcted tissue. Intravenous administration of contrast material prior to sacrifice produced contrast enhancement either of the rim or diffusely throughout the infarct. Thus CAT should have an important role not only in detecting but also in estimating the volume of acute myocardial infarctions.

Animals↗

PubMedDate not supplied

Direct and reflex myocardial effects of intracoronary administered contrast materials in the anesthetized and conscious dog: comparison of standard and newer contrast materials.

The direct and indirect actions on left ventricular dynamics of contrast material (sodium meglumine diatrizoate) currently used for coronary arteriography, modified ionic material (sodium meglumine calcium metrizoate) and non-ionic material (metrizamide) were assessed in conscious and anesthetized dogs. In both anesthetized and conscious animals, the diatrizoate compound caused an early (3--10 sec after injection) decrease in peak dp/dt and dp/dt/LVP40, followed by late (10--20 sec after injection) increases in these variables. The predominant early and later effects of the calcium metrizoate compound were increases in parameters of LV contractile state. Metrizamide produced no significant early alterations, but later induced a small increase in these variables. The positive inotropic actions of each of the contrast materials were attenuated by beta adrenergic blockade. The early effects of the contrast materials were similar in the presence of segmental ischemia. The late positive inotropic effects in response to the diatrizoate compound and metrizamide were not observed in the ischemic state, while the positive inotropic response induced by the calcium metrizoate compound was significantly reduced. Thus intracoronary administration of sodium meglumine diatrizoate produced direct myocardial depression, followed by adrenergically mediated myocardial stimulation. Calcium metrizoate caused prominent direct and adrenergically mediated augmentation in contractile state. Metrizamide induced the least alteration in LV contractile state.

Adrenergic beta-Antagonists↗

PubMedDate not supplied

Uptake of contrast materials by experimental acute myocardial infarctions: a preliminary report.

The concentration of iodine within infarcted and normal myocardium after intravenous administration of contrast material was determined by fluorescence excitation analysis in seven dogs at 48 hours after coronary arterial ligation. The iodine concentration of infarcted myocardial tissue was several times greater than normal myocardium after administration of meglumine/sodium diatrizoate, iodipamide, and an experimental polymer of iothalamic acid.

Acute Disease↗

PubMedDate not supplied

The effect of contrast media on the isolated perfused canine heart.

The intravascular injection of contrast medium produces a rise of ventricular filling pressure which may reflect blood volume expansion, a negative inotropic effect on the myocardium, and/or a decrease in ventricular diastolic compliance. This phenomenon was studied by randomly infusing three substances, Renografin-76, 1% saline and 38% sucrose, into the aortic root of the isolated perfused canine heart. The preparation was modified by having an inflated ballon within the left ventricular cavity so that the end diastolic ventricular volume and afterload were fixed. A dose-related depression of left ventricular systolic pressure and peak dP/dt due to contrast media occurred, without a significant change in the left ventricular diastolic pressure. This decrease in ventricular contractility due to Renografin-76 could not be attributed entirely to either a saline or an osmotic effect. No significant changes were observed in left ventricular diastolic compliance. Sucrose was found to exhibit a marked positive inotropic effect.

Animals↗

PubMedDate not supplied

Identification and evaluation of the contribution of the chemoreflex in the hemodynamic response to intracarotid administration of contrast materials in the conscious dog: comparison with the response to nicotine.

Intracarotid administration of ionic contrast material and nicotine in conscious, unsedated dogs caused similar biphasic reflex responses consisting of initial decreases followed by increases in heart rate and pressures. Both phases were characterized by increases in respiratory amplitude. The initial hypotension was not observed when heart rate was maintained constant. The initial bradycardia was absent after denervation of the carotid body and cholinergic blockade. The tachycardia was attenuated after ligation of the internal carotid artery and beta adrenergic blockade. Hwever, the hypertension persisted after denervation of the carotid body and ligation of the internal carotid artery but was attenuated after alpha adrenergic blockade. Nonionic contrast material caused almost no reflex hemodynamic effects. Like noxious substances such as nicotine, ionic contrast materials cause complex hemodynamic effects as a consequence of actions on the cardiovascular centers of the brain, carotid body chemoreceptors, and chemosensitive tissue in the external carotid circulation.

Animals↗

PubMedDate not supplied

Direct myocardial effects of intracoronary administration of new contrast materials with lost osmolality.

The effects of LV dynamics of the intracoronary administration of three new contrast materials with reduced osmolality were compared with those of a monomeric ionic material, sodium iothalamate, and the nonionic material, metrizamide. In eight anesthetized dogs, the monacid dimer, P286, caused increases in LV dimensions and decreases in LV systolic pressure and parameters of the contractile state. The changes were less than those caused by sodium iothalamte. The alterations in LV function tended to be greater, but not significantly so, during systemic hypoxemia compared to the normal state. The nonionic materials, P297 and iopamidol, like metrizamide, caused no deleterious effects on LV dynamics in either the normal or hypoxemic state. Nonionic materials actually caused a slight increase in parameters of the LV contractile state.

Animals↗

PubMedDate not supplied

Computerized tomographic appearance of evolving myocardial infarctions.

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Animals↗

PubMedDate not supplied

Effects of ionic and nonionic contrast agents on left ventricular and extracellular fluid dynamics during angiocardiography in an infant model.

Concern for side effects of contrast materials limits the volume that can be used for angiocardiography in infants; many of these effects are related to hyperosmolality. The effects of intracardiac injections of ionic (meglumine sodium diatrizoate) and nonionic (metrizamide) contrast agents on the left ventricle and body fluids were compared in an infant model. Immediately after injection, meglumine sodium diatrizoate (MSD) caused increases in left ventricular peak systolic pressure (LVPSP) (+26 +/- 5%) (control (C) = 92 mmHg), LV dp/dt (+21 +/- 6%) (C = 2610 mmHg/sec), left ventricular end-diastolic dimension (LVEDD) (+31 +/- 5%) (C = 10.5 mm), and left ventricular end-systolic dimension (LVESD) (+28 +/- 6%) (C = 7mm). Subsequently, LVPSP and dp/dt decreased to -16 +/- 6% and -23 4 +/- 6% of control, while LVEDD and LVESD rose. Dimension changes resolved by 15 minutes. Metrizamide caused immediate increases in LVPSP (+27 +/- 4%) (C = 86 mmHg) and LV dp/dt(+25 +/- 4%) (C = 2640 mmHg/sec). These parameters never declined significantly below control levels and were at control level at 15 seconds. Initial increases in LVEDD (+17 +/- 3%) (C = 10 mm) and LVESD (+6 less than 4%) (C = 6.5 mm) with metrizamide were significantly less than with MSD (P less than 0.008). MSD caused greater and more persistent elevations of serum osmolalities than metrizamide. Differences between the two agents were accentuated during systemic hypoxemia. Thus, ionic contrast agents appear to have a greater propensity for inducing toxic cardiovascular effects in infants than nonionic agents.

Angiocardiography↗

PubMedDate not supplied

The influence of hyperosmolality on left ventricular contractile state: disparate effects of nonionic and ionic solutions.

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Animals↗

PubMedDate not supplied

Role of iodinated contrast material in the evaluation of myocardial infarction by computerized transmission tomography.

In vivo and in vitro studies have shown that areas of myocardial infarctions can be delineated on CT scans after intravenous administration of iodinated contrast material to dogs with experimental myocardial infarctions. Within the first minute after intravenous administration of contrast material (initial myocardial perfusion phase), the infarct appears an as area of decreased x-ray attenuation (cold spot image). Studies using radiolabeled microspheres indicate that the relative attenuation numbers throughout the myocardium in this phase reflect myocardial perfusion (Hessel et al, 1978). Delayed scans obtained at 5 minutes and later showed a reversal in the attenuation values of normal and infarcted myocardium with the infarct appearing as an area of homogeneous or mottled increase in x-ray density compared to normal myocardium. (Siemers et al, 1978; Carlsson et al, 1977; Higgins et al, 1979). This phenomenon of delayed contrast enhancement of myocardial infarctions ensues as early as 8 hours after coronary occlusion (Higgins et al, 1979) and is present in evolved infarcts as old as 51 days (Newell et al, 1979). Direct measurements of iodine concentration in infarcts, normal myocardium, and organs surrounding the heart were performed in dogs with 48-hour-old myocardial infarctions using fluorescent excitation analysis (Higgins et al, 1978, 1979). These measurements of iodine concentration in tissue samples obtained at 10-180 minutes after intravenous administration of contrast material indicated that the highest iodine concentration in the infarct was at 10 minutes, but the highest ratio of iodine concentration of the infarct to normal myocardium was at 180 minutes. At all time intervals, the concentration of iodine within the infarct was fivefold greater than in the normal myocardium.

Animals↗