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At least 505 records · Page 28Linked to original sources
PubMed1980

The descending septal artery. Its relation to the conduction system of the heart.

The blood supply to the upper ventricular septum in the region of the conduction system is more abundant than the literature suggests. I found a significant arterial contribution to the upper ventricular septum from the proximal segment of the right coronary artery (RCA), or one of its early branches, in 77% of 65 hearts examined. Descending septal arteries (DSAs) supplied the region of the proximal conduction system in 68% of the hearts, about half of which demonstrated severe coronary arteriosclerosis. The influence of the DSA on the pathogenesis and subsequent course of conduction defects due to occlusive coronary artery disease remains to be evaluated. My results indicate that the preexisting blood supply derived from proximal RCA, from one or more of its early branches, or directly from the aorta plays an important role in this respect.

Angiography↗
PubMedDate not supplied

Poor results in attempting to demonstrate the cause of death by examination of the conduction system of the heart in cases of sudden death.

A microscopic examination of the proximal part of the conduction system in the heart was undertaken in seven cases of sudden death due to coronary arteriosclerosis; the same technique was applied to 31 control cases. A few infiltrations of mononuclear cells were demonstrated in relation to the conduction system in cases of sudden death as well as in controls. In one case severe narrowing of the sinus node artery was found without particular arteriosclerosis of the coronary arteries.

Adult↗
PubMed1986

Direct effects of diltiazem, nifedipine and verapamil on peripheral sympathetic nerve function, cardiac impulse conduction and cardiovascular function in anesthetized dogs subjected to ganglionic blockade.

The Ca2+ entry blockers diltiazem, nifedipine and verapamil produced dose-dependent increases in atrioventricular conduction time (A-H interval), while decreasing heart rate and mean arterial pressure in anesthetized dogs previously subjected to ganglionic blockade to prevent hypotension-induced reflex changes in sympathetic tone. Nifedipine and verapamil, but not diltiazem, also reduced (P less than 0.05) the tachycardia produced by electrical stimulation of the cardioaccelerator nerve at doses which did not alter the heart rate response to direct beta-adrenoceptor stimulation by isoproterenol (0.1 microgram/kg i.v.). The lowest doses of nifedipine (0.03 mg/kg) and verapamil (0.3 mg/kg) that produced decreases in mean arterial blood pressure were the same as or greater than those which selectivity reduced the tachycardiac effects of low frequency (1 Hz, 25-35 V, 5 ms), but not high frequency (10 Hz, 25-35 V, 5 ms) cardiac nerve stimulation. These data suggest that threshold vasodilator doses of some Ca2+ blockers may selectively reduce low level (or basal) sympathetic neurotransmission and this additional pharmacologic action may contribute to the antihypertensive mechanism. The failure to inhibit the high frequency nerve response may also help to explain the relatively low incidence of orthostatic hypotension associated with the clinical use of Ca2+ blockers as compared to other direct-acting vasodilators.

Animals↗
PubMed1991

Surgical anatomy of the conduction system of the heart in anomalies of the membranous part of the ventricular septum with orifice in it.

Specific features of surgical anatomy of the atrioventricular conduction system (AVCS) in true and false aneurysms of the membranous part of the ventricular septum were studied on 126 heart specimens. The authors succeeded in localisation and dissection of the CS with the aid of an original method of anatomical microdissection which they prefer to the histologic method in studying the surgical anatomy of CS. The advantage of the authors' method consists in an objective anatomical identification of CS while preserving the integrity of adjacent structures.

Anthropometry↗
PubMed1979

Overview of cardiovascular reflexes in hypertension.

The problem of cardiovascular reflexes in hypertension poses several questions. The first is whether alterations in cardiovascular reflexes can initiate a persistent increase in arterial pressure. Another is whether it is an alteration in depressor or in pressor reflexes that matters in hypertension. Other questions concern the type and nature of the reflex alterations that actually occur in hypertension and the place of resetting of baroreflexes in the sequence of physiologic events leading to increased blood pressure.

Animals↗
PubMed1982

Polymorphous ventricular tachycardia associated with normal and long Q-T intervals.

Polymorphous ventricular tachycardia may occur in the setting of either a normal or a prolonged Q-T interval. Torsade de pointes is a form of polymorphous ventricular tachycardia in which the polarity of the QRS complex exhibits phasic alterations in both axis and rate. Traditionally, torsade de pointes has been described in association with a variety of congenital and acquired (including drug and metabolic) causes of Q-T prolongation. The distinction between torsade de pointes and those polymorphous ventricular tachycardias occurring in patients with a normal Q-T interval has important therapeutic implications. The former requires strict avoidance of all drugs that may potentially further delay repolarization, including class I antiarrhythmic agents; immediately, the initiation of cardiac pacing is often necessary for control of arrhythmia, and on a long-term basis, sympathetic nervous blockade is often efficacious. In contrast, the polymorphous ventricular tachycardias with a normal Q-T interval usually respond to conventional therapy, including administration of class I antiarrhythmic agents. Thus, the management of polymorphous ventricular tachycardia should be based on the presence of absence of associated repolarization rather than on the morphologic features of the tachycardia. Unfortunately, recent advances in basic and clinical electrophysiology have not yet elucidated the pathophysiologic basis for these arrhythmias, although this is an area of active investigative interest.

Adult↗
PubMed1988

Effect of changes in cardiac autonomic balance on blood pressure regulation in man.

The role of cardiac autonomic balance in fitness-related differences in blood pressure regulation was evaluated by comparing the cardiovascular responses to lower body negative pressure (LBNP) in 10 trained and 10 untrained men. Cardiac autonomic balance was quantified as the ratio of resting heart rate to intrinsic heart rate, and was significantly lower in the trained subjects (0.68 +/- 0.03) than the untrained subjects (0.81 +/- 0.03) indicating a greater parasympathetic dominance at rest in the trained subjects. Arterial pressure decreased significantly more during LBNP in the trained subjects and was due to lower chronotropic and vasoconstrictor responses in these trained subjects. 'Cardiac autonomic balance' was equilibrated between the groups by partial parasympathetic blockade with atropine sulfate in the trained subjects and partial sympathetic blockade with metoprolol tartrate in the untrained subjects. Equilibration of cardiac autonomic balance eliminated the group differences in blood pressure maintenance, and chronotropic and vasoconstrictor responsiveness during LBNP. It was hypothesized that the elevated tone of parasympathetic control of the heart rate of the trained subjects resulted in an attenuation of blood pressure regulation.

Adult↗
PubMed1991

The effect of pentobarbital anesthesia on the autonomic nervous system control of heart rate during baroreceptor activation.

This study determined the influence of pentobarbital anesthesia on the autonomic nervous system control of baroreceptor mediated reflex bradycardia in the rat. Reflex bradycardia was elicited by phenylephrine-induced hypertension in conscious and pentobarbital anesthetized (PA) rats before and after sympathetic blockade with the beta-1 receptor antagonist atenolol or parasympathetic blockade with the peripherally acting muscarinic receptor antagonist methyl-atropine. Reflex bradycardia was significantly decreased by pentobarbital anesthesia. Cardiosympathetic blockade produced equivalent relative decreases in baroreflex gain in conscious and PA rats. In contrast, parasympathetic nervous system blockade with methyl-atropine produced relatively less inhibition of baroreflex gain in the PA rat compared with the conscious rat. These results suggest that pentobarbital anesthesia decreases baroreflex gain by inhibiting vagally mediated reflex bradycardia.

Anesthesia, General↗
PubMed1985

Heart rate variability of chronic alcoholics in withdrawal and abstinence.

Measurement of heart rate variability was performed in 106 healthy volunteers and 31 alcoholics. The mean momentary arrhythmia (MMA) of normal individuals showed an exponential decrease with increasing age. Cardiac autonomic neuropathy was found in 5 of 31 alcoholics. In agreement with the concept of hyperexcitability the withdrawing alcoholics had a significant increase in heart rate and decrease in MMA compared to later measurements. The result suggests that the diagnosis of autonomic alcoholic neuropathy may be reliable only after at least a one week period of abstinence from alcohol.

Adolescent↗
PubMed2006

Autonomic changes during wake-sleep transition: a heart rate variability based approach.

Autonomic function during sleep and wakefulness has been extensively investigated, however information concerning autonomic changes during the wake to sleep transition is scarce. The objective of the present study was to non-invasively characterize autonomic function and additional physiologic changes during sleep onset in normal and abnormal sleep. The estimation of autonomic function was based on time-frequency analysis of the RR interval series, using the power components in the very-low-frequency range (0.005-0.04 Hz), low-frequency (0.04-0.15 Hz), and high-frequency range (0.15-0.5 Hz). The ratio of low to high frequency power represented the sympathovagal balance. Thirty-four subjects who underwent whole night polysomnography were divided into 3 groups according to their complaints and study results: normal subjects, apneic patients (OSAS), and subjects with various sleep disorders (VSD). The results indicated a significant increase in RR interval during sleep onset, although its variability decreased; respiratory rate did not change, yet respiration became more stable; EMG amplitude and its variability decreased with sleep onset. Very-low-frequency power started to decrease significantly 2 min before sleep onset in all groups; low-frequency power decreased and high-frequency power did not change significantly in all groups, accordingly their ratio decreased and reflected a shift towards parasympathetic predominance. Although autonomic function displayed similar behavior in all subjects, OSAS and VSD patients presented a higher sympathovagal balance reflecting enhanced sympathetic predominance in those groups compared to normal subjects, both before and after sleep onset. All parameters reached a nadir at a defined time point during the process of falling asleep. We conclude that the wake-sleep transition period represents a transitional process between two physiologically different states; this transition starts with a decrease in the very slow oscillations in heart rate that anticipates a step-change resetting of autonomic function, followed by a decrease in sympathovagal balance towards the end of the process.

Adolescent↗
PubMed1997

Autoregressive analysis of cardiac RR intervals in preterm and full-term infants.

For the purpose of obtaining information on the maturation process of the autonomic nervous system in pre- and full-term infants, polygraphs were recorded during sleep from a total of 52 appropriate-for-dates infants at a conceptional age of 28-41 weeks. The 104 RR interval time series was calculated by autoregressive (AR) and component analysis. Histograms of damping frequencies obtained were divided into two frequency bands: low frequency fluctuations (LF) of less the 0.1 cycle/beat (c/b) and high frequency fluctuations (HF) of more than 0.15 c/b. Total power and LF power decreased with increases in the conceptional age or postnatal age at a significance level of 0.01, respectively. In addition, the HF amount of bio-informing activity increased (P < 0.001) and the damping time of HF also increased (P < 0.01). From these results, it was speculated that the activity of the sympathetic system decreases with increases in conceptional or postnatal age. It was also speculated that increased regularity and oscillatory duration in HF might be caused by the development of the reciprocal response of respiration to heart rate variation.

Autonomic Nervous System↗