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Biomedical subjects

G R Heyndrickx

Publications and source records attributed to G R Heyndrickx.

At least 73 records · Page 4Linked to original sources
PubMed1986

Effects of long-term treatment with amiodarone on exercise hemodynamics and left ventricular relaxation in patients with hypertrophic cardiomyopathy.

The influence of long-term treatment with amiodarone on exercise hemodynamics and on left ventricular relaxation was studied prospectively in patients with hypertrophic cardiomyopathy. Rest-exercise hemodynamics (n = 9) and echocardiographic relaxation indexes (isovolumic relaxation time, dPW/dt) (n = 11) were measured in control conditions and after 5 weeks of oral amiodarone treatment (600 mg daily first week, 400 mg daily second week, 200 mg daily afterwards). Long-term amiodarone treatment in patients at rest caused a significant drop in heart rate from 80 +/- 11 to 75 +/- 11 beats/min (p less than .05), a rise in mean pulmonary artery pressure from 19 +/- 7 to 25 +/- 10 mm Hg (p less than .02), and a rise in mean pulmonary capillary wedge pressure from 11 +/- 4 to 17 +/- 8 mm Hg (p less than .05). Systemic arterial pressure, cardiac output, and systemic vascular resistance remained unaltered. Exercise tolerance assessed by serial supine bicycle stress testing was reduced in six of nine patients. Amiodarone treatment caused a significant rise in pulmonary capillary wedge pressure from 22 +/- 8 to 37 +/- 9 mm Hg (p less than .001) at the highest identical workloads and from 26 +/- 10 to 37 +/- 9 (p less than .005) at maximal symptom-limited workloads. Similarly, mean pulmonary artery pressure rose from 37 +/- 15 to 51 +/- 18 mm Hg (p less than .01) at highest identical workloads and from 42 +/- 19 to 51 +/- 18 mm Hg (p less than .01) at maximal symptom-limited workloads. There were no significant differences at maximal exercise level in heart rate, systemic arterial pressure, cardiac output, or exercise factor. Echocardiographic studies performed before and during long-term amiodarone treatment revealed no change in isovolumic relaxation time, end-diastolic or end-systolic posterior wall thickness, and peak posterior wall thinning rate. A negative inotropic action of amiodarone could explain the worsened rest and exercise hemodynamics observed during long-term treatment of patients with hypertrophic cardiomyopathy. Echocardiographic relaxation indexes remained unaltered despite the elevated left ventricular filling pressures. This finding could suggest a deleterious effect of amiodarone on myocardial inactivation, possibly similar in mechanism to the depressed myocardial inactivation observed in hypothyroidism.

Adult↗
PubMed1986

Effects of brief periods of myocardial ischemia on regional myocardial function and creatine kinase release in conscious dogs and baboons.

The effects of 15 min periods of coronary occlusion on global and regional myocardial function, plasma creatine kinase (CK) and isoenzyme MB CK activity and subsequent myocardial necrosis were studied in 15 conscious dogs and 9 conscious baboons. Overall left ventricular (LV) function was assessed with measurements of LV systolic and diastolic pressures, rate of change of LV pressure, LV dP/dt. Regional LV function was assessed with measurements of regional segment length and velocity of shortening and/or regional LV wall thickening. An implanted hydraulic occluder on either the left anterior descending or circumflex coronary artery was inflated for 15 min. This induced complete loss of segment length shortening and systolic wall thickening (ultrasonic transit time technique). With release of the occlusion and reperfusion, recovery of regional mechanical function was delayed, but did occur after 6 hrs. Serial plasma enzyme activity revealed a significant increase in total CK as well as MB CK. At autopsy, neither gross pathological evidence (TTC-technique) nor histological evidence of myocyte necrosis was observed. Thus, in the conscious dog as well as in the conscious baboon, short episodes of intense myocardial ischemia do not result in a permanent deficit of myocardial function or necrosis. However, during the early phase of reperfusion, significant depression of regional mechanical function is observed associated with significant appearance of total CK and MB CK in the blood.

Animals↗
PubMed1985

Creatine kinase release not associated with myocardial necrosis after short periods of coronary artery occlusion in conscious baboons.

The effects of 15 minute periods of coronary artery occlusion on plasma creatine kinase (CK) and CK-MB isoenzyme activity, regional myocardial function and subsequent myocardial necrosis were studied in six conscious baboons 2 to 3 weeks after recovery from instrumentation. Mid left anterior descending coronary artery occlusion induced complete loss of systolic wall thickening (ultrasound transit time technique) and decreases in epicardial (-93%) and endocardial (-96%) blood flows (microsphere technique). Reperfusion after 15 minutes resulted in complete recovery of regional function 24 hours later. Serial plasma enzyme activity revealed a significant increase in total CK from 71 +/- 11 to 976 +/- 158 U/liter and in CK-MB from levels that were too low to measure to 21.4 +/- 2.9 U/liter. At autopsy, neither gross pathologic evidence (triphenyltetrazolium chloride staining technique) nor histologic evidence of myocardial necrosis was observed. Thus, in the conscious baboon short episodes of myocardial ischemia are associated with a significant appearance of CK and CK-MB in the blood in the absence of cellular necrosis.

Animals↗
PubMed1985

Elective PTCA of totally occluded coronary arteries not associated with acute myocardial infarction; short-term and long-term results.

Of 652 consecutive patients referred for coronary angioplasty between September 1980 and March 1984, 49 patients presented with total or functional 'occlusion' of the involved vessel. Total vessel occlusion was defined as absent anterograde filling beyond the lesion. Functional occlusion was defined as faint, late anterograde opacification of the distal segment in the absence of a discernible luminal continuity. In 39 patients, the total or functional occlusion represented a progression, without acute myocardial infarction, of a previously diagnosed stenotic lesion. The maximal potential duration of occlusion was estimated to be 4 weeks or less in 21 patients, more than 4 to 8 weeks in 12, and more than 8 weeks in 16. Dilation of the occluded artery was attempted in the left anterior descending coronary artery in 30 patients, in the right coronary artery in 8, in the circumflex coronary in 7 and in 4 jumpgrafts. For the whole group, angioplasty was successful in 28 patients (57%). The primary success rate with the functionally occluded vessel (81%) was significantly higher than with the total occlusion (45%). In 33 patients with an occlusion estimated to be of 8 weeks or less, angioplasty was successful in 65%. In the 16 patients with an occlusion estimated to be of 8 weeks or less, angioplasty was successful in 65%. In the 16 patients with an occlusion estimated to be of more than 8 weeks duration, dilation was successful in 44%. Of the 21 patients in whom angioplasty was unsuccessful, 11 required surgery (1 urgent with persistent pain and ST elevation and 10 elective). Ten patients were maintained on medical treatment. Of the 28 patients in whom angioplasty was successful, 10 patients had recurrence of symptoms during follow-up (1-42 months). Four were kept on medical therapy, three required bypass surgery and three underwent repeat percutaneous transluminal coronary angioplasty (PTCA). After primary success, late angiographic studies obtained in 20 out of 28 patients showed reocclusion in 8. In conclusion, elective PTCA of totally occluded coronary arteries is feasible but the primary success rate is lower (57%) than that associated with conventional lesions. The long-term clinical results following successful angioplasty are satisfactory (64%), but the incidence of reocclusion is higher (40%).

Adult↗
PubMed1985

Cardiac imaging techniques in the diagnosis of angiosarcoma of the heart: report of two cases.

Angiosarcoma of the heart is a rare and highly malignant tumour. Most of the reported cases have been diagnosed post mortem. In a one year period two cases were diagnosed during life and surgically treated. The only possible hope for survival is early diagnosis and surgical removal. Our cases illustrate the contribution of cardiac imaging techniques to early diagnosis and the feasibility of radical excision of this tumour.

Adult↗
PubMed1985

Effects of altered site of electrical activation on myocardial performance during inotropic stimulation.

The effects of altering the site of electrical activation on responses to isoproterenol (ISO) and treadmill exercise were examined in mongrel dogs instrumented for long-term measurement of left ventricular pressure, left ventricular dP/dt, coronary blood flow, cardiac output, left ventricular diameters, and mean arterial pressure and O2 content in the coronary sinus and aorta. During spontaneous rhythm, 0.2 micrograms/kg/min ISO increased heart rate by 90 +/- 7 beats/min, left ventricular dP/dt by 2479 +/- 301 mm Hg/sec, cardiac output by 3.5 +/- 0.9 liters/min, coronary blood flow by 30.4 +/- 3.9 ml/min, and myocardial oxygen consumption (MVO2) by 3.91 +/- 0.84 ml/min. During right atrial pacing at 193 +/- 7 beats/min, the effects of ISO were not different from the effects during spontaneous rhythm, with the exception of a lesser increase in coronary blood flow and lesser reductions in coronary resistance and left ventricular end-diastolic diameter and pressure. During right ventricular pacing at an identical rate, ISO increased left ventricular dP/dt (1140 +/- 158 mm Hg/sec) and cardiac output (2.2 +/- 0.5 liters/min) significantly less (p less than .025) than during either sinus rhythm or right atrial pacing, while MVO2 rose to a higher value. During right ventricular pacing the changes in mean arterial pressure and left ventricular end-diastolic diameters with ISO were not significantly different from those during right atrial pacing. Treadmill exercise induced significantly smaller (p less than .025) increases in left ventricular dP/dt during right ventricular pacing as compared with during either right atrial pacing or sinus rhythm, while MVO2 rose to a higher value.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Effects of coronary artery reperfusion on regional myocardial blood flow and function in conscious baboons.

The effects of coronary artery reperfusion initiated 1 hr and 3 hr after coronary artery occlusion were evaluated on measurements of overall and regional left ventricular function and on regional myocardial blood flow. These experiments were conducted in conscious baboons 2 to 3 weeks after recovery from instrumentation with a solid state left ventricular pressure gauge, aortic and left atrial catheters, a hydraulic occluder around the mid left anterior descending coronary artery, and pairs of ultrasonic transducers implanted in the endocardium of the left ventricular free wall or across the free wall to measure endocardial segment shortening and wall thickening, respectively. Coronary artery occlusion induced similar effects in both groups. At 1 hr after occlusion, the ischemic zone was characterized by severe and equal reductions in both endocardial (-97 +/- 1%) and epicardial (-95 +/- 4%) blood flows and complete loss of regional systolic function, which was replaced by paradoxical wall motion. Reperfusion initiated after 1 hr of ischemia was associated with a marked transient increase in endocardial (+386 +/- 51%) and epicardial (+544 +/- 79%) blood flows. During the subsequent 4 weeks, segment shortening and wall thickening tended to improve. However, at 4 weeks after reperfusion, segment shortening was still depressed by 45 +/- 12% and wall thickening by 58 +/- 14%. In contrast, reperfusion initiated after 3 hr of ischemia was not associated with a significant hyperemic response, and systolic segment shortening and wall thickening did not recover during the subsequent 4 week period.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Role of prejunctional alpha 2-adrenergic receptors in the regulation of myocardial performance during exercise in conscious dogs.

We examined, in conscious dogs, the potential role of prejunctional alpha 2-adrenergic receptors for the regulation of heart rate and contractility response to exercise through modulation of the neurotransmitter release. Changes in heart rate and left ventricular pressure with time during comparable exercise levels, together with changes in norepinephrine concentration in the coronary sinus, were compared before and after the intravenous administration of: prazosin (0.5 mg/kg), a preferential postjunctional alpha 1-adrenergic receptor blocking agent; phentolamine (1 mg/kg), a nonselective alpha-adrenergic blocking agent; and yohimbine (0.3 mg/kg), a preferential prejunctional alpha 2-adrenergic receptor blocking agent. During exercise after phentolamine or yohimbine, changes in heart rate and left ventricular dP/dt were markedly potentiated compared to the control exercise, as well as to exercise after prazosin, whereas the norepinephrine concentration in the coronary sinus was substantially elevated. After intracoronary administration of phentolamine (0.1 mg/kg) or yohimbine (0.03 mg/kg), heart rate and contractility response to exercise were also potentiated, compared to the control exercise. These observations indicate that, in the intact conscious animal, prejunctional alpha 2-adrenoreceptors are stimulated during exercise, thereby modulating the norepinephrine release through a negative feedback inhibitory mechanism. Blocking these receptors by phentolamine or yohimbine results in an uncontrolled norepinephrine release during exercise associated with an augmented beta-adrenergic receptor-mediated end organ response, i.e., a potentiation in heart rate and contractility response.

Adrenergic alpha-Antagonists↗
PubMed1984

Influence of vagal nervous activity on blood pressure variability.

In our previous studies, it was shown that blood pressure variability was largely independent from the adrenergic nervous system. In the present work, vagal nervous influence on blood pressure variability was analysed both in dogs and in men. In eight chronically instrumented conscious dogs, striking fluctuations of blood pressure were observed when quietly resting; these fluctuations correlate well with fluctuation of heart rate. Atropine abolished all variations both of heart rate and of pressure. Reflex stimulation of vagal tone by neosynephrine increased variability of both parameters. Thus, in dogs, blood pressure variability is related to variability of heart rate which is largely influenced by vagal tone. The same question was approached in seven male volunteers; blood pressure and heart rate were measured automatically every 2 min, during 1 h, before and after atropine. In control conditions, no correlation between variability of heart rate and of blood pressure was observed. Atropine clearly decreased variability of heart rate and of diastolic blood pressure. These data confirm the animal results; however, the influence of vagal nerves on variability is less pronounced in man than in dogs.

Adult↗
PubMed1982

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

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.

Animals↗