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PubMed1994

Some observations on the mechanism of pressure related atrial fibrillation.

In order to investigate the effect of atrial pressure on the propensity of the atria to fibrillate and the mechanism of this association, the right atrial pressure was changed acutely by transfusion-bleeding in 12 anaesthetized open-chest dogs. Under various atrial pressures the conduction time was measured between two pairs of hook electrodes positioned on the two atrial appendages respectively. The effective refractory period was measured by continuous pacing of the right atrium at a 250 ms cycle length at double threshold intensity and interpolating a progressively earlier stimulus after each eighth paced beat. The propensity of fibrillation was studied by rapid (450 min-1) pacing of the atria at double threshold intensity for 10 s at different atrial pressures. At a high (> or = 14 mmHg) atrial pressure the conduction time (45.7 +/- 14.2 ms) was significantly (P < 0.01) longer, the effective refractory period (157.9 +/- 15.2 ms) significantly (P < 0.01) longer and the atrial fibrillation (11/19 or 57.9%) significantly (chi 2 = 9.95, P < 0.001) more common than at a low (< or = 10 mmHg) pressure (35.2 +/- 11.6, 146.2 +/- 12.4, 3/24 or 12.5%, respectively). Analysis of variance showed that the probability of atrial fibrillation was significantly affected by the atrial pressure but not by either the conduction time or the effective refractory period. The findings suggest that an increase in right atrial pressure by acute volume overload prolongs the inter-atrial conduction time and right atrial refractoriness and increases the propensity of the atria to fibrillate by rapid atrial stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed2006

AVE0118, blocker of the transient outward current (I(to)) and ultrarapid delayed rectifier current (I(Kur)), fully restores atrial contractility after cardioversion of atrial fibrillation in the goat.

BACKGROUND: The loss of atrial contractile function after cardioversion of atrial fibrillation (AF) contributes to the thromboembolic risk associated with AF. The newly developed blocker of the transient outward current (I(to)) and ultrarapid delayed rectifier current (I(Kur)) AVE0118 prolongs atrial action potential duration and might therefore enhance atrial contractility. We compared the ability of AVE0118 to restore atrial contraction after cardioversion of AF with the efficacy of conventional positive inotropic compounds in the goat model of AF. METHODS AND RESULTS: Eighteen goats were chronically instrumented with epicardial electrodes, a pressure transducer in the right atrium, and piezoelectric crystals to measure right atrial diameter. Atrial contractility and refractoriness and QT duration were measured before and after 1 week (3 to 8 days) of AF induced by repetitive burst pacing. The measurements were repeated after administration of digoxin (0.02 mg/kg), dobutamine (5 microg x kg(-1) x min(-1)), the Ca2+ sensitizer EMD57033 (1 mg x kg(-1) x min(-1)), the L-type Ca2+ channel agonist BayY5959 (0.1 mg x kg(-1) x min(-1)), and AVE0118 (0.01 to 0.2 mg x kg(-1) x min(-1)). The effect of AVE0118 on the configuration of atrial monophasic action potentials was determined for comparison. After 1 week of AF, atrial contractility during sinus rhythm or slow atrial pacing was reduced to <10%. Digoxin and dobutamine failed to increase atrial contractility. EMD57033 restored 41% and BayY5959 restored 48% of atrial contractility at baseline. BayY5959 significantly prolonged QT duration by 24.7%. AVE0118 enhanced atrial contraction to 156% of the baseline value. The positive inotropic effect was accompanied by a pronounced prolongation of atrial action potential duration and refractoriness, whereas QT duration remained unchanged. CONCLUSIONS: Conventional positive inotropic drugs showed limited effect on atrial contractility after cardioversion of AF or produced QT prolongation. In contrast, the I(to)/I(Kur) blocker AVE0118 fully restored atrial contraction without proarrhythmic effects on the ventricle.

Action Potentials↗
PubMed1995

Atrial veins of the human heart.

Modern anatomical description divides the cardiac veins into two groups: tributaries of the greater cardiac vascular system (GCVS) and tributaries of the smaller cardiac vascular system (SCVS), consisting of the Thebesian vessels. Both systems intercommunicate extensively. With the exception of the oblique vein of the left atrium (Marshall's vein), veins draining the walls of both the left and right atrium have not been well illustrated or described in anatomical atlases and textbooks. Consequently, we do not know exactly to which of the two groups (GCVS or SCVS) the atrial veins belong. There are three groups of left atrial veins: (1) tributaries of the left coronary vein and the coronary sinus; (2) special veins draining the right-sided walls of the left atrium that terminate via intramural sinuses in the right atrium, which vessels occur in 92% of cases and belong to the GCVS; (3) in 81% of cases special veins drain the myocardium of the posterior and superior walls of the left atrium. In most cases they empty into the left atrium itself; in almost 40% of the cases they are connected with mediastinal veins. These veins, also belonging to tributaries of the GCVS, constitute a distinctly separate category of cardiac veins and should be designated proper veins of the left atrium. The veins draining the walls of the right atrium fall also into three groups: (1) In most cases there are short or large intramural tunnels or sinuses in the basic walls of the auricle and atrioventricular node area. The generally valveless openings of all the venous tunnels and sinuses are lined up on a circle just above the tricuspid valve and between the openings of both venae cavae. (2) There are also thin veins at the junction of the right atrium with both the superior and inferior vena cava. (3) In addition, there are numerous cardiac veins of the "smallest size" (real Thebesian veins).

Aged↗
PubMed1992

Virtual real-time digital processing of hemodynamic data.

At present, the majority of cardiac catheterization laboratories acquire and store hemodynamic data in analog form. To examine the possibility of performing complex analysis of digital data during the catheterization procedure, we examined whether virtual real-time digital (fast Fourier) analysis improves the accuracy of clinical data. We compared digital filtering of fluid manometry during the right heart catheterization with 10-Hz and 250-Hz analog filters. Using the simultaneously acquired micromanometry as the "gold standard," we found that analog filtering is associated with a greater error and time delay than digital filtering. This study demonstrates that digital hemodynamic data analysis performed during cardiac catheterization can improve the quality of data obtained during right heart catheterization, with the results available within seconds. More extensive use of computers in the cardiac catheterization laboratory may be useful for both clinical and research purposes.

Atrial Function, Right↗
PubMed1994

Evaluation of electrocardiographic criteria for right atrial enlargement by quantitative two-dimensional echocardiography.

OBJECTIVES: This study was conducted to evaluate the sensitivity and specificity of traditional electrocardiographic (ECG) criteria for right atrial enlargement and identify improve criteria, using quantitative two-dimensional echocardiography. BACKGROUND: Traditional ECG criteria for right atrial enlargement, such as P pulmonale, have been increasingly criticized as insensitive and nonspecific. Quantitative two-dimensional echo-cardiography has been shown to be a useful method for evaluating atrial size. METHODS: Hospitalized patients with mild, moderate and severe right atrial enlargement were selected from our laboratory's data base and compared with age- and gender-correlated hospitalized control subjects. After exclusions, 100 patients with right atrial enlargement and 25 control patients remained. Planimetric measurement of right atrial volumes was accomplished by two independent observers using the single-plane method of discs algorithm. Electrocardiograms were independently evaluated for current and newly proposed right atrial enlargement criteria. RESULTS: Fifty-two patients (52%) were in sinus rhythm, 41 were in atrial fibrillation, 5 were in atrial flutter, and 2 were in ectopic atrial rhythm. All control subjects were in sinus rhythm. The right atrial volume for the control group was 35.0 +/- 7.4 ml (mean +/- SD), with a narrow, roughly normal distribution. The right atrial volume for the patient group was 147.6 +/- 69.1 ml (median 127.2) in a wide, skewed distribution. The difference of mean values was highly significant (p = 0.0001). Right ventricular enlargement was found to some degree in all patients with right atrial enlargement. The most powerful predictors of right atrial enlargement were a QRS axis > 90 degrees, a P wave height in lead V2 > 1.5 mm and an R/S ratio > 1 in lead V1 in the absence of complete right bundle branch block. The combined sensitivity of these three criteria was 49%, with preservation of 100% specificity. P pulmonale detected only 6% of patients with right atrial enlargement. CONCLUSIONS: Using quantitative two-dimensional echocardiography, we found that most previously reported ECG criteria for right atrial enlargement have low predictive power. The best predictors of right atrial enlargement were a P wave height > 1.5 mm in lead V2 and, as new criteria, a QRS axis > 90 degrees and an R/S ratio > 1 in lead V1 in the absence of complete right bundle branch block. The combined sensitivity of these three criteria was 49%, with preservation of 100% specificity. Further studies are needed to prospectively validate these findings.

Atrial Function, Right↗
PubMed1997

[Right atrial thrombosis and pulmonary embolism: role of echocardiography].

The echocardiographic detection of a right thromboembolus, although rare, should be considered as a cardiological emergency that could lead to death for massive pulmonary embolism. The case of a 70 year-old man admitted to our Institution with the suspicion of pulmonary embolism is described. The echocardiogram performed showed a large mobile thrombus in the right atrium prolapsing through the tricuspid valve during diastole. After thrombolytic therapy with r-TPA, the patient faced a progressive hemodynamic deterioration and died of electromechanical dissociation.

Aged↗
PubMed1999

Atrial and ventricular pressures in atrial flutter.

The hemodynamic effects of atrial flutter (AF) are unknown. The purpose of the present study was to investigate the changes in atrial and ventricular pressures after induction of AF. In 23 patients with paroxysmal AF (age 59 +/- 9 years), a hemodynamic study was performed both during sinus rhythm and after induction of the tachyarrhythmia. During AF, 13 patients showed a fixed 2:1 AV conduction and 10 patients showed variable conduction. Mean right and left atrial pressures increased (P < 0.001) and right and left ventricular end-diastolic pressures decreased (P < 0.001) after induction of AF. Both the increase in mean atrial pressures and the decrease in ventricular end-diastolic pressures were present either in the patients with fixed 2:1 AV (heart rate: 133 +/- 15 beats/min) or in those with variable conduction (heart rate 96 +/- 15 beats/min), but were more marked in the former. AF produces an impairment of atrial function, as evidenced by the increase in mean atrial pressures and reduction in ventricular end-diastolic pressures in the absence of an elevated heart rate. The mechanisms responsible for the increase in mean atrial pressures are unknown; however, atrial contractions against closed AV valves seem to play an important role.

Atrial Flutter↗
PubMed1998

Optimization and mechanism of step-leap respiration exercise in treating of cor pulmonale.

The interaction between cardiovascular system and the respiratory system is complicated and may be used for the rehabilitation of the cor pulmonale disease. To study the effects of different breathing mode on the cardiac and pulmonary systems, a mathematical model is established based on the previous work. Using this model, computer simulation experiments are carried out for searching an optimal respiration mode in treating of cor pulmonale disease. Results indicate that the step-leap respiration mode could provide a better assistant to the rehabilitation of the cor pulmonale patients in the sense of increasing coronary flow, reducing pulmonary arterial pressure and reducing the working load for the right heart. This result is also proven by the clinical experiments. This work may suggest that a proper directed respiration exercise can be used in the treatment of cor pulmonale disease.

Algorithms↗
PubMed1996

Atrial flutter: lessons from surgical interventions (musing on atrial flutter mechanism).

We report our experience with seven patients who underwent direct surgical ablation of problematic common flutter. Intraoperative mapping was obtained in four patients. Surgical techniques varied over time. A circular incision of the right atrium was performed in the first patient. Two patients had epicardial cryoablation of the isthmus between the inferior vena cava and the tricuspid valve annulus. Four patients had extensive endocardial cryoablation of the isthmus. There were no immediate postoperative complications. One patient had atrial fibrillation 2 months postoperatively and underwent a corridor operation 1 year later. The other six patients are free of arrhythmias without antiarrhythmic drugs. Surgical ablation confirmed that the common form of atrial flutter is associated with a right atrial macroreentrant circuit. One of our intraoperative endocardial maps suggested that variant reentrant circuits can be associated with variant forms of flutter.

Adult↗
PubMed1998

Organized activation during atrial fibrillation in man: endocardial and electrocardiographic manifestations.

INTRODUCTION: Atrial fibrillation is not entirely random, but little is known about the spatiotemporal endocardial organization and its surface ECG manifestations. METHODS AND RESULTS: In 16 patients with atrial fibrillation (chronic, n = 14), endocardial mapping of the trabeculated, the posteroseptal smooth right atrium, and the coronary sinus was performed using multipolar catheters. The surface ECG was analyzed by determining "fibrillation wave" (F wave) amplitude, rate, and polarity. During 50 minutes of atrial fibrillation, an organized activation was present 72% +/- 32% of the analyzed time on the trabeculated, 19% +/- 15% on the smooth right atrium (P < 0.01), and 51% +/- 33% along the coronary sinus (P < 0.05). The direction of organized activation was craniocaudal in 72% +/- 16%, caudocranial in 10% +/- 9% (P < 0.01), and indeterminable in 18% +/- 11%. The mean surface F wave amplitude in lead V1 was 0.128 +/- 0.06 mV during 28 seconds of atrial fibrillation with a craniocaudal direction of activation and 0.065 +/- 0.02 mV during a disorganized activation (P < 0.01). A stable relation between surface F waves and organized trabeculated right atrial activation was observed, and the mean F wave cycle length (190 +/- 27 msec) was highly comparable to the simultaneously measured endocardial cycle length (191 +/- 27 msec, correlation coefficient 0.97). F wave polarity in V1 was positive in 12 of 14 patients during craniocaudal and negative in 11 of 14 patients during caudocranial right atrial free-wall activation. CONCLUSION: An organized activation during atrial fibrillation with a predominant craniocaudal direction on the trabeculated right atrium is frequently present and influences the appearance of "coarse" or "fine" atrial fibrillation as well as F wave polarity on the surface ECG.

Adult↗
PubMed1993

Influence of isosorbide dinitrate (ISDN) on compliance of the pulmonary venous system.

Irreversible poor pulmonary venous compliance can worsen the natural course of patients with high pulmonary capillary wedge pressure, especially those with mitral stenosis, but nitrates (isosorbide dinitrate--ISDN), which have venodilatory properties, could increase this compliance in most patients. The aim of this study was to assess the hemodynamic effects of ISDN in patients with mitral stenosis, with special emphasis on the pulmonary venous compliance. Pulmonary venous compliance was estimated according to the Hirakawa equation (dV/dp = 0.4 x k2 x sV/(v-d)) in 39 patients with mitral stenosis during preoperative right heart catheterization with Vygon 5155-180 thermodilution catheters at rest and during exercise (25 W) in the supine position. This procedure was repeated after the application of 3.75 mg of Iso-Mack spray. Overall, ISDN increased pulmonary venous compliance significantly both at rest and during exercise (6.0 to 7.5 ml/mmHg and 6.0 to 7.6 ml/mmHg, respectively). The patients were divided into two groups according to their level of ISDN response; those with a good response of an increase of 15% or more in pulmonary venous compliance (Group I), and those with an increase of less than 15% (Group II). There were significant differences between these two groups in stroke volume index and heart rate. In Group I, while the mean right atrial pressure, mean pulmonary artery pressure and mean pulmonary wedge pressure all decreased significantly, there was a simultaneous insignificant decrease in the stroke volume index and an also insignificant increase in the heart rate.(ABSTRACT TRUNCATED AT 250 WORDS)

Atrial Function, Right↗
PubMed1997

Hemodynamic changes after cardioversion of chronic atrial fibrillation.

After cardioversion of chronic atrial fibrillation to sinus rhythm, there is a gradual increase of 56% in cardiac output over 4 weeks. The increase is caused by the gradual return and increasing strength of left atrial mechanical activity as the atrial myopathy of chronic atrial fibrillation subsides. Cardiac output decreases after cardioversion of atrial fibrillation in more than a third of patients, and the decrease may last a week. Acute pulmonary edema is uncommon; 50% of cases occur within 3 hours of cardioversion, with a mortality of 18%. The reduced cardiac performance after cardioversion most likely results from the combination of heart disease and cardiac depressant effects of anesthetic drugs used. Pulmonary and/or coronary artery emboli and the resumption of right atrial mechanical activity before left atrial mechanical activity may be additional factors in the pathogenesis of pulmonary edema after cardioversion. Anticoagulant therapy should be continued for a month or longer after cardioversion in those patients who maintain sinus rhythm to prevent thromboembolism.

Anesthetics↗
PubMed1991

Cor triatriatum dexter: recognition and percutaneous transluminal correction.

Cor triatriatum dexter is a rare congenital anomaly in which an obstructive membrane is located in the right atrium. The detection usually occurs after the sequelae of systemic congestion, coagulopathy, and hepatic dysfunction have set in, leading up to a high surgical risk. A percutaneous balloon correction of cor triatriatum dexter in a patient with advanced right-sided congestive symptoms and hepatic dysfunction is presented. This efficacious method is an alternative to surgical correction and could be extended to the more common cor triatriatum sinistra.

Adult↗
PubMed2000

Right atrial pressure predicts hemodynamic response to apneic positive airway pressure.

OBJECTIVE: To evaluate if the preexistant filling state, assessed by right atrial pressure (RAP), pulmonary artery occlusion pressure (PAOP), and right ventricular end-diastolic volume index (EDVI), would define the subsequent hemodynamic effects of increases in airway pressure (Paw). DESIGN: Prospective open clinical study. SETTING: Postoperative intensive care unit, university hospital. PATIENTS: Twenty-two consecutive ventilator-dependent patients with mild to severe acute lung injury with Murray scores (scoring infiltrates on chest radiograph, oxygenation index, lung compliance, and the level of positive end-expiratory pressure) ranging from 0.5 to 3.0 without history of preexisting cardiopulmonary disease. INTERVENTIONS: Paw varied during apnea from 0 to 10, 20, and 30 cm H2O using inspiratory hold maneuvers of 15 secs. MEASUREMENTS AND MAIN RESULTS: Cardiac index and right ventricular ejection fraction were measured by the thermodilution technique. We made measurements in triplicate using manual injection of iced saline. Right ventricular volumes were calculated. Increasing Paw induced variable changes in cardiac index among subjects (+6% to -43% change from baseline 0 cm H2O Paw values), which correlated with percentage changes in both stroke index (r2 = .89) and right ventricular EDVI (r2 = .75), whereas heart rate and right ventricular ejection fraction did not change. The change in cardiac index from 0 to 30 cm H2O Paw correlated with baseline values for RAP, PAOP, and right ventricular EDVI (r2 = .68, .43, and .34, respectively, p < 0.01). Increases in RAP correlated with lung compliance if baseline RAP was >10 mm Hg but did not if it was < or =10 mm Hg. Similarly, patients with baseline RAP < or =10 mm Hg had a greater decrease in cardiac index than patients with a RAP >10 mm Hg (for 30 cm H2O Paw: -30% +/- 9% vs. -8% +/- 7%, p < .01). CONCLUSIONS: Apneic positive Paw decreased cardiac output mainly by reducing venous return. From the investigated filling variables, RAP was most sensitive in predicting the hemodynamic response, followed by PAOP and right ventricular EDVI. Patients with RAP < or =10 mm Hg, if subjected to aggressive positive pressure ventilation, are at risk of hemodynamic deterioration and organ hypoperfusion.

Adult↗
PubMed1991

Effects of rapid volume expansion on the right filling pressures after prosthetic valve surgery.

The effects of rapid intravascular volume expansion were studied in 12 patients, 4 to 14 years after single prosthetic heart valve replacement. The data observed showed a statistically significant mean difference before and after volume expansion of right atrial mean pressure and right ventricular end diastolic and pulmonary capillary pressures. However, right atrial and pulmonary capillary pressures equilibration was not detected. The right atrial pressure form showed abnormal variations during inspiration. Dip and plateau right ventricular diastolic pressure configuration was recorded in 6 patients after expansion, was absent in 2 and questionable in 4. A deep Y descent with an M-shaped right atrial pressure form was recorded in all 12 patients. The explanation for these phenomena is unclear. Thus, in the absence of pressure equilibration and clinical evidence of constriction, the abnormalities recorded during rapid volume expansion should be cautiously interpreted.

Adult↗
PubMed1994

Relation between cycle length, volume, and pressure in type I atrial flutter.

Assuming that type I atrial flutter is a macroreentrant circuit, its cycle length should vary with the atrial dimensions. In order to test this hypothesis, flutter cycle length was measured while inducing atrial volume and pressure changes by postural and pharmacological means in seven patients undergoing a therapeutic programmed stimulation for type I atrial flutter conversion. Right atrial volume was estimated from B-mode echocardiography data. Basal values were compared with those obtained during inspiration, expiration, Valsalva maneuver, negative tilt (head down), and positive tilt (head up) with 0.8-1.6 mg p.o. nitroglycerin. The right atrial size increased slightly from 17.8 to 18.3 cm2 (P = 0.04) during the pressure load induced by negative tilt (+3 mmHg), with a corresponding lengthening of the flutter cycle length from 228 to 233 msec (P = 0.02). Similarly, pressure unloading of -2 mmHg by positive tilting and nitrates was accompanied by a decrease in right atrial size to 16.6 cm2 (P = 0.04), with a corresponding decrease in cycle length from 228 to 219 msec (P = 0.03). Respiratory maneuver yielded similar results with an inspiratory cycle lengthening, expiratory shortening, and further shortening during Valsalva maneuver. These experiments demonstrate a direct relation between cycle length and atrial volume in human type I atrial flutter. They underline the importance of the right heart preload and atrial size for the electrophysiological characteristics of type I atrial flutter. Beside its fundamental interest, this finding is important for the understanding of the mechanism of maintenance and therapeutic responses of this common arrhythmia.

Atrial Flutter↗
PubMed2005

Regulation of cardiovascular functions during acute blood loss.

Sudden blood loss of moderate degree causes fall in blood pressure, which is compensated to certain extent by baroreceptor mediated rise in heart rate and vasoconstriction. In case of severe haemorrhage fall in blood pressure is accompanied by bradycardia indicating failure of baroreceptor mediated recovery in blood pressure. In such conditions partial recovery in the blood pressure with time is possible due to mechanisms other than baroreflex. Therefore, in the present study the regulation of cardiovascular functions on increasing severity of blood loss in the absence of any therapeutic intervention was examined to elucidate the mechanisms involved in the recovery of blood pressure under such conditions. Two groups of animals were studied: (a) In the first group (n = 10) 20% of the total blood volume loss was induced, (b) In the second group (n = 10) 35% of the total blood volume loss was induced. In both the groups cardiovascular parameters were evaluated for one hour after the induction of haemorrhage to record any recovery due to natural compensatory mechanisms. In both the groups there was a significant fall in mean arterial pressure, cardiac output, stroke volume, right atrial pressure and base deficit. A significant increase in heart rate and total peripheral resistance was produced after 1 min of haemorrhage in 20% blood loss while a fall in total peripheral resistance and no rise in heart rate was produced after 35% blood loss. There was a recovery in cardiac output and mean arterial pressure with time in both the cases of blood loss. While a rise in heart rate and stroke volume was produced in 20% blood loss however an initial increase in stroke volume alone and later rise in heart rate alone was produced during recovery phase in 35% blood loss. These finding suggest that 20% blood loss is compensated by baroreflex while 35% blood loss is not accompanied by tachycardia so mechanisms other than the baroreflex, like increase in the vagal tone, contribute to the initial recovery in blood pressure and cardiac output.

Animals↗
PubMed1998

Coronary blood flow changes during atrioventricular sequential pacing with different atrioventricular delays in normal individuals.

This study examined the effects of different atrioventricular (AV) intervals, during AV sequential pacing, on hemodynamics and coronary blood flow in individuals with normal hearts. Left anterior descending artery blood flow velocity was measured, using intracoronary Doppler, in 17 normal individuals. Five pacing tests were applied in random order for 5 min, at 15 beats/min above the sinus rate. Four tests using AV sequential pacing with AV intervals of 175, 150, 100, and 50 ms, and one using atrial pacing were applied. Mean flow velocity was 21 +/- 9 cm/s, 20 +/- 9 cm/s, 17 +/- 7 cm/s, 17 +/- 7 cm/s, and 22 +/- 10 cm/s, respectively (F = 8.87, p = .00001). The hemodynamic effects of these 5 pacing tests were assessed in 8 different normal subjects. Isovolumic relaxation time constant and left ventricular systolic pressure decreased, whereas right atrial pressure increased during AV sequential pacing with short AV intervals. Thus, during short-term AV sequential pacing at rest, coronary blood flow in a normal left anterior descending artery decreases with short AV intervals.

Atrial Function, Right↗