Chronic instrumentation and its lack of effect on the hemodynamics and regional myocardial blood flow of conscious dogs

Brief Report: Role of Parent-Reported Executive Functioning and Anxiety in Insistence on Sameness in Individuals with Germline PTEN Mutations

This study aimed to characterize the relationship between insistence on sameness (IS), executive functioning (EF) and anxiety among individuals with PTEN mutations and individuals with macrocephalic ASD. The sample included 38 individuals with PTEN mutation and ASD diagnosis (PTEN-ASD; M_age = 8.93 years, SD_age = 4.75), 23 with PTEN mutation without ASD (PTEN-no ASD; M_age = 8.94 years; SD_age = 4.85) and 25 with ASD and macrocephaly but with no PTEN mutation (Macro-ASD; M_age = 11.99 years; SD_age = 5.15). The final model accounted for 45.7% of variance in IS, with Set-Shifting EF subdomain as a unique independent predictor (t = 4.12, p < 0.001). This investigation provides the first preliminary evidence for the EF-anxiety-IS interrelationship in individuals with PTEN mutations and with macrocephalic ASD.

Cardiac and hemodynamic effects of the selective bradycardic agent KC 8857 during exercise-induced myocardial ischemia

The effects of an in vitro bradycardic agent without negative inotropism, KC 8857 (3,7-di-(cyclopropylmethyl)-9,9-tetramethylene-3,7-diazabicyclo-[3.3.1]- nonane dihydrochloride), were tested in chronically instrumented dogs in a model of exercise-induced myocardial ischemia. KC 8857 was i.v. infused during critical stenosis of the circumflex branch of the left coronary artery which led to exercise-induced myocardial dysfunction. KC 8857 caused a decrease in heart rate, left ventricular dp/dtmax and calculated myocardial oxygen demand at rest and during exercise. Since positive dp/dtmax values at a given heart rate were not altered by KC 8857 it may be assumed that myocardial function was restored mainly by the decrease in heart rate.

The effects of nitroglycerin on regional myocardial contractile dysfunction produced by treadmill exercise or isoprenaline stimulation in dogs

1. To compare different methods of cardiac stress testing that are clinically applied in the management of coronary heart disease, 2 groups of dogs each were chronically instrumented and subjected to treadmill exercise or isoprenaline infusion in the presence of coronary stenosis. 2. It was of interest to determine differences in haemodynamic and regional myocardial contractile parameters, the response to antianginal therapy (nitroglycerin 15 micrograms kg-1 15 min-1, i.v.), and, in particular, whether this response differed according to the mode of cardiac stimulation, i.e. treadmill exercise or isoprenaline infusion. 3. After stenosis of the circumflex branch of the left coronary artery which affected resting myocardial function only minimally, treadmill exercise or isoprenaline infusion induced transient regional contractile dysfunction. Heart rate, arterial blood pressure, left ventricular end-diastolic pressure and left ventricular dp/dtmax were registered and myocardial oxygen demand was calculated. Regional contractile performance was assessed by ultrasonic distance measurement in the underperfused and in a normally perfused area. 4. Treadmill exercise led to an increase in systolic arterial and left ventricular end-diastolic pressure. In contrast, isoprenaline-induced stimulation led to a decrease in diastolic arterial and left ventricular end-diastolic pressure. Regional contractile function in the critically underperfused area showed a deterioration during both modes of stress. Nitroglycerin completely abolished stress-induced contractile dysfunction only in the group where treadmill exercise was employed for stimulation. 5. The inability of nitroglycerin to prevent myocardial dysfunction in the isoprenaline group may be due to exhaustion of the arterial and/or venous vasodilator potency of nitroglycerin in the presence of adrenoceptor vasodilatation induced by isoprenaline. 6. These findings indicate that clinical antianginal drug testing and the evaluation of the course of disease in patients with coronary heart disease may be highly dependent on the test method chosen.

Coronary distending pressure and delayed myocardial ischemia

The role of blood pressure alterations in the delayed onset of myocardial ischemia following sympathetic stimulation was studied in seven anesthetized dogs. In the presence of coronary stenosis, stimulation of the left stellate ganglion produced significant increases in heart rate and mean aortic pressure, but not in mean coronary blood flow or intracoronary pressure. Following cessation of stimulation, heart rate and aortic pressure returned to control levels over a 1- to 2-minute period. During this time, there was a progressive coronary vasoconstriction, as indicated by a significant fall in coronary arterial flow and intracoronary pressure. When the hypertensive response to stellate stimulation was prevented by controlled exsanguination, the coronary vasoconstriction was not delayed but occurred during stimulation. In the second phase of experiments, the aorta was constricted so as to raise systemic pressure to the peak level achieved during stimulation. Elevation of systemic pressure consistently restored coronary arterial blood flow and intracoronary pressure to the control values. By contrast, induction of hypertension by restimulation of the stellate ganglion failed to reverse the delayed coronary vasoconstriction. We conclude that delayed myocardial ischemia results from the imbalance between coronary distending pressure and an alpha-adrenergically mediated vasoconstrictor activity that persists following cessation of sympathetic nervous system stimulation.

Delayed myocardial ischemia following the cessation of sympathetic stimulation

A phenomenon entitled "delayed myocardial ischemia" has been described, in which there is a significant degree of coronary malperfusion following the cessation of behavioral stress. The primary objective of the present study was to develop a model for the delayed ischemic response in anesthetized animals to gain insights into the underlying mechanisms. In 15 morphine and chloralose-anesthetized dogs, a moderate degree of stenosis was applied to the left circumflex coronary artery by means of a toroidal balloon occluder. The pulsed Doppler technique was used to monitor coronary flow. After baseline data were obtained, the left stellate ganglion was stimulated for 30 seconds. Heart rate increased (63%), as did systemic blood pressure (41%) and flow in the left circumflex artery (47%). These parameters rapidly returned to control levels when stimulation was terminated. Forty-five to 90 seconds later, coronary flow decreased by 65% and coronary vascular resistance increased by 45%. These hemodynamic changes were accompanied by ECG abnormalities indicative of regional myocardial ischemia. The delayed ischemic response could be prevented by pretreatment with either nifedipine (20 micrograms/kg) or prazosin (0.3 mg/kg). These data indicate that the primary mechanism for the delayed ischemic response is alpha-adrenergically mediated contraction of the smooth muscle in the coronary artery wall.