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PubMed1983

[Cardiac effects of acetylcholine and its congeners].

Acetylcholine produced an elevation of the atrial pressure and decreased the systemic output dose-relatedly at 30 micrograms or more without producing any change in the heart rate. Negative chronotropic effects were observed only with doses of more than 600 micrograms. These effects of acetylcholine were enhanced by physostigmine and antagonized by atropine, while pindolol and 6-hydroxydopamine exerted no influence. Acetylcholine-induced elevation of atrial pressure and decrease of systemic output were similarly observed even when the heart was paced at a constant rate. Carbachol and methacholine produced qualitatively similar changes in the atrial pressure and systemic output. However, carbachol was unique in that it produced a dose-related negative chronotropic effect. Vagal stimulation induced an elevation of atrial pressure and a decrease of systemic output associated with bradycardia. Effects of vagal stimulation on atrial pressure and systemic output were abolished in the paced heart. These findings suggest that exogenous acetylcholine cannot reach the pacemaker site because of the abundant presence of cholinesterase in the region of the pacemaker, while acetylcholine released by vagal stimulation can reach the pacemaker site before being degraded by cholinesterase. The elevation of the atrial pressure and a decrease in the systemic output produced by exogenous acetylcholine can be ascribed to activation of the receptors in the ventricular myocardium, while the negative inotropic effects of vagal stimulation are due to an inhibition of atrial functions.

Acetylcholine↗
PubMedDate not supplied

Evaluation of the clinical electrophysiological effects of antianginal drugs without specific antiarrhythmic properties.

The authors have studied the electrophysiological effects of four antianginal drugs: oxyfedrine, nifedipine, dipyridamole and carbochromene. These drugs demonstrated different and sometimes contrasting effects on sinus node function, atrial refractoriness and atrioventricular conduction. These effects may constitute an indication or a contraindication in different clinical pictures and should be considered in the choice of treatment of patients with coronary artery disease.

Angina Pectoris↗
PubMed1994

Systemic and pulmonary haemodynamic effects of intravenous infusion of non-ionic isoosmolar dimeric contrast media. An investigation in the pig of two ratio 6 contrast media.

The systemic and pulmonary haemodynamic effects of i.v. infusion (1 ml/s) of high doses (4 ml/kg) of 2 non-ionic, isoosmolar dimeric contrast media (CM) were investigated in 17 female pigs. The 2 CM were iodixanol and iotrolan. Both CM induced a significant increase of the following parameters: mean arterial, mean right atrial, mean pulmonary arterial, mean pulmonary arterial occlusion pressure, cardiac output, stroke volume, and diuresis. The plasma concentration of atrial natriuretic peptide was significantly increased following infusion of the 2 CM. A significant decrease was seen in the systemic and pulmonary vascular resistance.

Animals↗
PubMed1994

Reducing effect of atrial natriuretic factor on Na, K-ATPase activity in rat kidney.

This study was designed to examine the effect of the rat atrial extract (RAE) and synthetic rat ANF123-150 (rANF) on the renal Na, K-ATPase activity in Wistar anesthetized rats. Na, K-ATPase activity was assayed by measuring the amount of inorganic phosphate liberated from ATP. RAE from 40.3, 80.6 mg of tissue and rANF in the following doses: 0.043, 0.087, 0.173, 0.260 nM/kg/min reduced Na, K-ATPase activity by 59, 64 and 11, 34, 37, 45% respectively in the renal medulla but not in the cortex. It was associated with the increase in diuresis and natriuresis. Five and ten minutes after the end of rANF administration, Na, K-ATPase activity was decreased by 78 and 57% respectively, diuresis and natriuresis were significantly higher than the control. After fifteen minutes enzyme activity returned to normal, diuresis and natriuresis were increased. After thirty minutes there was a 37% increase in Na, K-ATPase activity but diuresis and natriuresis were still higher than control values. We conclude that the inhibition of Na, K-ATPase in the medulla of the rat kidney is one of the mechanisms of ANF action.

Animals↗
PubMed1993

[Does effective cardioversion after surgery for valvular heart disease improve hemodynamic indicators?].

In 55 patients aged 47 +/- 6 years successful electrical cardioversion of atrial fibrillation was made. 24 hours before and after cardioversion, ekg and M-mode, 2-D and Doppler echocardiography was performed. Important improvement in ejection fraction (Simpson method), (p < 0.005) and in stroke index (Simpson method, p < 0.01; Doppler method, p < 0.005) was found in 64% of pts. Pts with haemodynamic improvement (HI) were significantly younger, had smaller, left atrial area in apical two-chamber view and left ventricular diastolic diameter and longer pulmonary acceleration time. In pts with HI the duration of AF was significantly shorter and closed mitral commissurotomy less frequent (p < 0.05). Restoration of mechanical atrial function (A-wave) was found in 44% of pts. In pts with A-wave HI was more often (p < 0.001). There was no correlation between maximal peak A-wave flow velocity and HI.

Adult↗
PubMed1993

Atrial natriuretic peptide response to postural changes and upright exercise in patients with venous valvular insufficiency.

To investigate the effects of postural changes and upright exercise on atrial natriuretic peptide release and renin-angiotensin-aldosterone system behavior in patients with venous valvular insufficiency, plasma ANP, plasma renin activity and aldosterone were measured in 11 patients with venous disease and in 11 age-matched controls. In patients with large varicose veins and venous valvular dysfunction, standing was associated with a greater fall in circulating ANP levels (p < 0.05) and upright exercise was accompanied by a smaller rise in ANP concentrations (p < 0.05) as compared with controls. A significant (p < 0.001) inverse relationship was found between the number of venous segments with reflux and both upright and exercise plasma ANP concentrations (r = -0.91; r = -0.84, respectively). In the two groups the response of the renin-angiotensin-aldosterone system to upright position and physical stress was similar. These results suggest that a decreased atrial stretch, due to a reduced venous return, could account for the blunted ANP response to erect posture and exercise in patients with venous valvular incompetency.

Adult↗
PubMed1996

Effect of age on stretch-induced secretion of atrial natriuretic factor.

Plasma atrial natriuretic factor (ANF) levels are known to be higher in aged rats and humans. Although this may be partially explained by a reduction in clearance from the circulation, it was not known whether the secretory nature of the atrial tissue also changes with age. We measured ANF release in response to atrial distention in young adult (2-3 months) and older retired breeder (4-6 months) male rats both in vivo (conscious instrumented animals) and in vitro (isolated perfused atria). Whereas increased intraluminal pressure caused a rise in ANF secretion when using atria derived from the younger rats, there was no such response when using atria derived from the older rats, i.e., stretch induced secretion was impaired. This appeared to be secondary to a reduction in atrial compliance in the older animals. Unlike previous studies, basal plasma ANF levels were lower in our retired breeders, although the response to volume loading was preserved. These results suggest that, already by about 6 months of age, the atrial tissue is less responsive to changes in atrial pressure. The increased plasma levels previously reported in senescent rats are therefore probably a result of reduced clearance rather than increased secretion.

Aging↗
PubMed1997

[Is reduced left ventricular volume related to mechanisms of dynamic mid-ventricular obstruction provoked by dobutamine infusion?].

Forty-seven patients with unexplained chest pain and normal resting echocardiograms were examined to see whether dynamic mid-ventricular obstruction (MVO) is induced by dobutamine infusion. Dynamic MVO was provoked in 17 patients (MVO group), but not in the other 30 patients (Non-MVO group). Before dobutamine infusion, the blood pressure in the MVO group was higher than that in the Non-MVO group (p < 0.05), but end-diastolic volume index (p < 0.001), end-systolic volume index (p < 0.01), stroke volume index (p < 0.001), cardiac index (p < 0.001), end-diastolic volume (p < 0.01) and end-systolic volume (p < 0.05) of the apical territory of the left ventricle in the MVO group were significantly less than those in the Non-MVO group. The left atrial function, left ventricular ejection fraction and ejection fraction of the apical territory of the left ventricle did not differ between the groups. Seven patients in the MVO group were re-examined by dobutamine stress echocardiography after beta-blocker administration, showing that the dynamic MVO was completely suppressed. The end-diastolic volume tended to increase after beta-blocker administration, but no significant difference was found in any other variables except heart rate. The results suggest that a smaller left ventricle and higher blood pressure are important characteristics in patients with dobutamine-induced dynamic MVO, and additionally, the difference in local myocardial contractility may be an important cause of the induction of dynamic MVO.

Adrenergic beta-Agonists↗
PubMedDate not supplied

What is "congested" in cardiac failure? A newer approach to plain film interpretation of cardiac failure.

The amount and location of intra- and extravascular fluids varies for the type and duration of heart failure. In some instances (acute LHF) pulmonary and systemic blood volume actually diminishes, and in others (chronic LHF) pulmonary blood volume diminishes at the bases while increasing in the upper lobes. It is only in right heart failure that clinically visible "congestion" occurs and the phrase congestive failure should be reserved for right heart failure. It is more valuable clinically for the film reader to analyze which compartments contain increased or diminished fluid and from this analysis, to decide whether the patient is in left, right or biventricular failure and whether this is acute or chronic. Upper lobe engorgement, (flow inversion) is not caused by basal edema, as previously hypothesized, but by reflex vasoconstriction secondary to chronic elevation of left atrial pressure. The mechanism is designed to improve left atrial function.

Acute Disease↗
PubMed2001

The effects of atrial fibrillation on functional recovery in post-stroke patients.

PURPOSE: This study evaluates the negative effects of atrial fibrillation (AF) on after stroke recovery and its relationship with age and other concomitant diseases. METHOD: One hundred and ninety-nine consecutive inpatients, after their first stroke, were enrolled and entered a rehabilitation program lasting 60 days. The mean interval since the stroke was 19 days. The disability, both at admission and at discharge, was assessed by Functional Independence Measure (FIM). Atrial fibrillation was diagnosed at admission on the basis of electrocardiographic recordings. Gender, age, blood pressure and blood sugar level were also taken into account. RESULTS: Stroke patients suffering from AF, when compared to those lacking AF, have higher disability at admission as well as at discharge and had a lesser gain in functional recovery. No statistical difference of the AF occurrence was found between male and female patients. The negative correlation between age and functional gain was found only in AF patients. There was also a significant association between AF and hypertension, but not between AF and diabetes. At the beginning and at the end of the study, the median FIM scores of all the patients with AF were quite similar irrespective of manifesting hypertension, diabetes or neither of these two. CONCLUSIONS: The presence of AF has a negative prognostic value on post stroke outcome, particularly in the elderly patients. The pattern of recovery of stroke subjects having AF is not influenced by concomitant diseases like hypertension or diabetes.

Animals↗
PubMed1994

Relation of left atrial volume and systolic function to the hormonal response in idiopathic dilated cardiomyopathy.

We studied the relation of left atrial mechanical function to the hormonal response in 14 patients with idiopathic dilated cardiomyopathy. Left atrial volumes were echocardiographically measured at mitral valve opening (maximal), at onset of atrial systole (onset of the P wave of the electrocardiogram) and at mitral valve closure (minimal) from the apical 2- and 4-chamber views using the biplane area-length method. Left atrial systolic function was assessed with the left atrial active emptying fraction ([volume at onset of atrial systole-minimal]/[volume at onset of atrial systole]). Plasma renin activity, aldosterone and atrial natriuretic peptide plasma levels were determined using commercially available kits. Left atrial maximal volume was directly, and left atrial active emptying fraction was inversely related to plasma renin activity (r = 0.60, P = 0.02 and r = -0.59, P = 0.026, respectively), aldosterone (r = 0.61, P = 0.02 and r = -0.53, P = 0.048) and atrial natriuretic factor (r = 0.79, P = 0.0009 and r = -0.62, P = 0.01) plasma levels. Thus, increased left atrial size and depressed left atrial contractile performance are associated with increased hormonal response in idiopathic dilated cardiomyopathy.

Adult↗
PubMed2000

Left ventricular function, cardiac dysrhythmias, atrial activation, and volumes in nondipper hypertensive individuals with left ventricular hypertrophy.

BACKGROUND: Arrhythmic patterns and left ventricular geometric adaptations to pressure overload were investigated in 76 patients with untreated borderline-to-moderate sustained essential hypertension studied by 2-dimensional and M-mode echocardiography, 12-lead, Holter, and signal-averaged electrocardiography, and ambulatory blood pressure monitoring. METHODS AND RESULTS: Sixty-two age- and sex-matched normal adults were chosen for data comparison. Hypertrophic hypertensive patients were subdivided into 2 subgroups: 44 patients with nocturnal blood pressure reduction (dippers) and 32 patients without it (nondippers). Common afterload and diastolic function indexes were found to be lower in combined nondipper and dipper groups, but only fractional shortening decreased in nondippers. The number of premature atrial and ventricular contractions per hour was high in dippers and nondippers, with no statistically significant differences between them; atrial and ventricular complex dysrhythmias were similar. Signal-averaged electrocardiography showed a prolonged P-wave duration in dipper and nondipper patients with high atrial volumes but no late ventricular potentials and no difference in quantitative P-wave analysis. Left atrial volumes, P-wave duration, and premature atrial contractions were found to be positively linked to left ventricular hypertrophy. In nondipper patients a linear correlation was observed between left atrial volume and P-wave duration, although supraventricular ectopic activity was connected to left atrial volume enlargement both in dipper and nondipper patients. CONCLUSIONS: These data suggest that the nondipper pattern is not linked to a worse arrhythmogenic substrate; only atrial volume increase may be related to significant supraventricular activity and prolonged atrial activation in nondipper patients, but late ventricular potentials are uncommon in hypertrophic hypertensive patients.

Arrhythmias, Cardiac↗
PubMed1991

Long-term functional integrity of atrial leads.

The effectiveness and reliability of atrial leads has been questioned. We studied retrospectively, all atrial leads implanted at our center (n = 494; 438 Medtronic Model 6957J, 56 Medtronic Model 4512) over a 5-year period ending December 31, 1987, to determine the frequency of atrial lead failure (pacing, sensing, or both) and the median duration of proper pacing and sensing function for each lead model studied. Eighty-eight percent of the polyurethane atrial leads continued to function satisfactorily at 5 years, results somewhat better than those reported heretofore in the literature, as well as our own past results with a variety of different lead types. There were 29 failures of pacing, sensing, or both (6% of implants). The cumulative survival of the atrial leads at 5 years was 88%. Pacing and sensing survival were 91% +/- 2.4% and 88% +/- 2.9%, respectively. We conclude that the choice of pacing mode for a new pacemaker should be based solely on the clinical indication and not on the concern that atrial pacing and sensing will be unreliable.

Electrodes, Implanted↗
PubMed1999

Radial approach: a new concept in surgical treatment for atrial fibrillation. II. Electrophysiologic effects and atrial contribution to ventricular filling.

BACKGROUND: In a previous study the atrial incisions that follow the concept of the radial approach were designed according to the activation sequence during sinus rhythm and the atrial coronary artery anatomy in normal dogs. The purpose of the present study was to determine whether the radial approach provides a more physiologic activation sequence and atrial transport function than the maze procedure. METHODS: Ten dogs that had undergone the radial approach (n = 5) or the maze procedure (n = 5) were studied 6 weeks postoperatively. Sinus node function and inducibility of atrial fibrillation were examined before and after operation. The atria were mapped endocardially with 212 electrodes, and atrial activation sequences during sinus rhythm and right atrial pacing were examined. Atrial transport function was assessed by transepicardial Doppler echocardiography. RESULTS: No dogs developed sinus node dysfunction postoperatively. Both the radial approach and the maze procedure equally prevented sustained atrial fibrillation. The atrial activation sequence was more synchronous after the radial approach than after the maze procedure. There was no electrically isolated region after the radial approach. The total activation time of the left atrium was significantly shorter after the radial approach than after the maze procedure (53.6+/-9.8 versus 70.5+/-9.6 ms, p<0.05). The ratio of peak flow velocity of the E wave to the A wave (peak E/A) of the transmitral Doppler flow was significantly smaller after the radial approach than after the maze procedure (1.7+/-0.4 versus 3.5+/-1.7, p<0.05). The atrial filling fraction of the transmitral Doppler flow was significantly larger after the radial approach than after the maze procedure (29.9%+/-7.3% versus 14.8%+/-5.0%, p<0.01). There was no significant difference in peak E/A and atrial filling fraction of the transtricuspid Doppler flow between the two procedures. CONCLUSIONS: The radial approach provides a more synchronous activation sequence and atrial transport function, and thus may represent a more physiologic alternative to the maze procedure as a surgical treatment for atrial fibrillation.

Atrial Fibrillation↗
PubMed1998

[Diastolic function parameters and atrial arrhythmias in patients with arterial hypertension].

OBJECTIVE: To investigate in patients with arterial hypertension (HT) the extent of left ventricular (LV) hypertrophy and diastolic function in relation to atrial arrhythmias. PATIENTS AND METHODS: In 112 hypertensive patients (40 women, 72 men; mean age 50 +/- 6.6 years) with a mean systolic blood pressure for the cohort of 170 +/- 5 mmHg, their first invasive coronary angiography was performed between July 1995 and October 1997 because of angina pectoris and/or an abnormal stress electrocardiogram. After excluding coronary heart disease LV dimensions and diastolic function were measured by echocardiography; in 59 of the 112 patients LV hypertrophy was demonstrated. In addition, long-term blood pressure monitoring, exercise and long-term electrocardiography, late-potential analysis and measurement of heart rate variability were undertaken. The control group consisted of 51 patients without arterial hypertension after exclusion of coronary heart disease. RESULTS: Even in the hypertensive patients without LV hypertrophy diastolic LV function and ergometric exercise capacity were reduced. The risk of LV arrhythmias was significantly higher in patients with LV hypertrophy than those without and in the control group, as measured by the complexity of atrial arrhythmias (P < 0.001), the incidence of abnormal late potentials (P < 0.001) and reduction in heart rate variability (29.3 +/- 5.3 ms vs 47.8 +/- 12.1 ms vs 60.7 +/- 6.6 ms; P < 0.001). There were similar results regarding severe complex atrial arrhythmias (38.5 vs 15.0 vs 0%; P < 0.001). The incidence of atrial arrhythmias correlated with the LV diameter (r = 0.68, P < 0.001), LV morphological dimensions and diastolic function (isovolumetric relaxation time r = 0.44, P < 0.001) and the ratio of early to late diastolic inflow (r = 0.46; P < 0.001). CONCLUSIONS: Hypertensive patients have a higher risk of atrial and ventricular arrhythmias, depending on the degree of LV hypertrophy. But atrial arrhythmias, in contrary to ventricular arrhythmias, are also closely related to abnormalities in LV diastolic function.

Adult↗