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PubMed1987

Fetal lamb ventricles respond differently to filling and arterial pressures and to in utero ventilation.

Right and left ventricular function were investigated in 12 fetal lambs (127-140 days gestation) instrumented with electromagnetic flow sensors on the ascending aorta and the main pulmonary artery, and with vascular catheters. Nine fetuses were equipped with a postductal aortic occluder and the trachea was cannulated in eight. Control arterial blood values were pH 7.36 +/- 0.02 (SD), PCO2 49.3 +/- 2.3 torr, PO2 18.4 +/- 1.7 torr, and hematocrit 37.3 +/- 4.4%. Biventricular function curves relating stroke volume to mean right and left atrial pressure were generated by rapid withdrawal and reinfusion of fetal blood. Both function curves were composed of steep ascending and plateau limbs that intersected at a breakpoint. Stroke volumes at the breakpoints were 0.94 +/- 0.19 ml.kg-1 and 0.63 +/- 0.15 ml.kg-1 for right and left ventricle, respectively (p less than 0.001). During postductal aortic occlusion, arterial pressure increased by 19.3 +/- 7.9 torr while right ventricular stroke volume decreased by approximately 48% and left ventricular stroke volume decreased by approximately 9%. In utero ventilation increased arterial pressure, heart rate, PO2, and oxygen content. Right atrial pressure increased from 3.9 +/- 1.3 to 5.8 +/- 2.9 torr (p less than 0.05); left atrial pressure from 3.5 +/- 1.5 to 10.0 +/- 4.4 torr (p less than 0.05). Aortic flow nearly doubled (112 +/- 29 to 211 +/- 35 ml.min-1.kg-1) (p less than 0.05), and the left ventricular function curve shifted upward. The right ventricular function curve was shifted downward during ventilation. We conclude that the fetal ventricles differ significantly in their outputs, response to changes in arterial pressure, and to the onset of in utero ventilation.

Animals↗
PubMed1989

[Right ventricular function in retrograde cardioplegia for myocardial protection--an experimental study].

Anterior cardiac veins which are the main drainage vessels of the right ventricle drain directly into the right atrium. Therefore, the right ventricular wall may not be perfused effectively during open heart surgery by the use of retrograde cardioplegic method resulting in postoperative right ventricular dysfunction. Seventeen mongrel dogs were subjected to this study and were placed on cardiopulmonary bypass using a conventional heart-lung machine. Total aortic cross-clamping time was 60 minutes in all dogs. In Group I (n = 6), 4 degrees C St. Thomas' Hospital solution (15 ml/kg body weight) was injected into the aortic root by the use of a syringe. Cardioplegic solution was replenished every 20 minutes with a half of the initial dose (7.5 ml/kg body weight). Group II (n = 6) were the dogs with the retrograde cardioplegia in which 4 degrees C St. Thomas' Hospital solution (15 ml/kg body weight) was given retrogradely from the coronary sinus by the drip method at the height of 60 cm, and the replenishing dose and interval of cardioplegia were the same as Group I. Group III (n = 5) was the dogs treated with retrograde cardioplegia identical to Group II and the combined use of topical cooling with ice-slush. The hearts were resuscitated after 60 minutes of aortic cross-clamping. Right ventricular functions such as cardiac output, right atrial pressure, right ventricular end-diastolic pressure, right ventricular max dp/dt, and shortening fraction of the right ventricle were measured 15, 30, 45, and 60 minutes after cardiac resuscitation respectively. In Group II, right atrial pressure was significantly elevated from the control value 15 and 30 minutes after cardiac resuscitation. On the other hand, all indices of right ventricular functions in Group III showed insignificant changes. The present experimental study demonstrated the retrograde cardioplegic method could produce right ventricular perfusion resulting in right ventricular dysfunction early after cardiac resuscitation. This deleterious effect however could be prevented by the combined use of topical cooling of the right ventricle with ice-slush.

Animals↗
PubMed2005

Volumetric cine CMR to quantify atrial structure and function in patients with atrial dysrhythmias.

PURPOSE: To implement a cardiac magnetic resonance (CMR)-based protocol to define atrial structure and function in individuals with paroxysmal atrial fibrillation (PAF), heritable cardiac conduction and myocardial disease with atrial dysrhtyhmias (HCCMD), and healthy controls. METHODS: Fifteen controls, 20 PAF, and 12 HCCMD subjects underwent CMR examination including: multislice short-axis cine, multislice horizontal long-axis cine, and gadolinium-enhanced coronal plane magnetic resonance angiography (MRA) for pulmonary vein analysis. We also assessed for ventricular myopathy with delayed myocardial enhancement (DME) acquisitions. RESULTS: Right and left ventricular measurements did not differ among the three groups. Seven heritable atrial dysrhythmia subjects and no control or PAF subjects demonstrated midmyocardial fibrosis of the basal interventricular septum by DME. Left atrial (LA) volume at the onset of atrial systole and minimal LA volume were significantly higher in PAF subjects compared to controls (p < 0.05 for both), LA percent emptying was significantly lower in PAF subjects (p < 0.01), and RA percent emptying was significantly lower in PAF subjects compared to controls (p < 0.01), though these differences were not significant when controlling for heart rate, age and gender. There was no significant difference in right atrial (RA) volumes among study groups. Atrial volumes and function did not differ significantly between heritable atrial dysrhtyhmia subjects and controls. PAF subjects had greater frequency of a right middle pulmonary vein (RMPV) than controls (6/20 vs. 3/15) that did not reach statistical significance. CONCLUSIONS: CMR can quantify atrial structure and function in patients with PAF compared to controls. This protocol could not detect abnormalities in atrial function in early affected patients with heritable cardiomyopathy and atrial premature beats.

Adult↗
PubMed1990

Chronic beta 1-adrenoceptor antagonist treatment sensitizes beta 2-adrenoceptors, but desensitizes M2-muscarinic receptors in the human right atrium.

1. In 64 patients undergoing coronary artery bypass grafting the effects of chronic beta 1-adrenoceptor antagonist (metoprolol, atenolol, bisoprolol) treatment on right atrial beta-adrenoceptor and muscarinic M2-receptor number and functional responsiveness were investigated. 2. The beta 1-adrenoceptor antagonists increased right atrial beta 1-adrenoceptor number, did not affect beta 2-adrenoceptor number, and decreased muscarinic M2-receptor number. 3. Concomitantly, activation of right atrial adenylate cyclase by 10 microM GTP, 10 microM isoprenaline and 1 microM forskolin was enhanced and inhibition by 100 microM carbachol was diminished. 4. On isolated, electrically driven right atria the beta 1-adrenoceptor-mediated positive inotropic effect of noradrenaline was - even with beta 1-adrenoceptor number increased - not altered, while the beta 2-adrenoceptor-mediated effect of procaterol was markedly enhanced. However, the carbachol-induced negative inotropic effect was decreased. 5. It is concluded that chronic beta 1-adrenoceptor antagonist treatment increases beta 1-adrenoceptor number and concomitantly sensitizes beta 2-adrenoceptor function, but desensitizes muscarinic M2-receptor function in the human heart.

Adenylyl Cyclase Inhibitors↗
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↗
PubMed1994

Response of right ventricular systolic function to exercise stress: effects of pulmonary vascular resistance on right ventricular systolic function.

To elucidate factors influencing responses of right ventricular systolic function to exercise stress, we evaluated the right ventricular ejection fraction and peak ejection rate with two different loading conditions, atrial septal defect and mitral stenosis, at rest and during exercise by means of gated equilibrium blood pool radionuclide ventriculography. In both atrial septal defect and mitral stenosis, strong correlations between changes in the right ventricular ejection fraction with exercise and pulmonary vascular resistance at rest (r = -0.97, p < 0.001; r = -0.86, p < 0.005: respectively) were found. Significant correlations between changes in the right ventricular peak ejection rate with exercise and pulmonary vascular resistance at rest (r = -0.85, p < 0.05; r = -0.75, p < 0.01: respectively) were found in atrial septal defect and mitral stenosis. Both the right ventricular ejection fraction and peak ejection rate were lower during exercise than at rest when pulmonary vascular resistance at rest was more than 200 dynes.sec.cm-5.m2 in both atrial septal defect and mitral stenosis. In conclusion, right ventricular systolic function responding to exercise stress was influenced by the pulmonary vascular resistance in both atrial septal defect and mitral stenosis.

Adult↗
PubMed1982

Effects of afterload and baroreceptors on cardiac function in fetal sheep.

The fetal cardiac function curve, the relationship between cardiac output and right atrial pressure, was studied in 17 chronically catheterized fetal sheep. Combined biventricular cardiac output was measured by thermodilution while right atrial pressure was either lowered by haemorrhage, or raised by infusion of 5% (w/v) glucose. Cardiac output rose as right atrial pressure increased from 2 to 6 mmHg, but at higher right atrial pressures (up to 15 mmHg) cardiac output reached a plateau and remained constant at approximately 500 ml/min per kg. The normal right atrial pressure of 4.6 +/- 0.6 mmHg (SEM) placed these fetuses near the plateau of their cardiac function curves. When aortic pressure was increased from 11 to 16 mmHg by a methoxamine infusion, the cardiac function curve was depressed, maximum cardiac output on the plateau averaging only about 340 ml/min per kg. Ganglionic blockade with hexamethonium did not alter the position of the cardiac function curve, suggesting baroreceptors did not affect cardiac function. The cardiac function curve was shifted upward significantly during an isoproterenol infusion, which kept descending aortic pressure in the normal range by dilating the peripheral vasculature. If cardiac function was represented by the relationship between stroke work and right atrial pressure, no physiologically significant differences could be detected among the four conditions. Therefore, fetal cardiac function is normally near maximum, very sensitive to afterload and uninfluenced by baroreceptors. Cardiac output, however, with volume loading during beta-receptor stimulation, can be increased provided arterial pressure does not increase.

Animals↗
PubMed1996

Age-related characterization of atrial adenosine A1 receptor activation: direct effects on chronotropic and inotropic function in the Fischer 344 rat.

Adenosine, an endogenously produced nucleoside, has direct negative chronotropic and inotropic effects on right and left atrial tissues, respectively. Age-related differences in the effects of A1 adenosine receptor activation on atrial rhythmic and contractile function were investigated in adult (6-8 months) and senescent (23-24 months) Fischer 344 (F344) rats. Senescent right atria (RA) were more sensitive to the negative chronotropic effects of R-phenylisopropyladenosine (R-PIA), a selective A1 receptor agonist, than adult RA (EC50: 4.8 +/- 0.7 vs 10.8 +/- 1.5 nM). However, senescent left atria (LA) were 15.4% less responsive to the maximal negative inotropic effects of R-PIA than adult LA. R-PIA did not significantly change resting force from basal values in either age group, but 90% relaxation time was prolonged threefold in senescent LA compared with adults. Radioligand binding experiments with 1,3-[3H]dipropyl-8-cyclopentylxanthine, a selective adenosine A1 receptor antagonist, showed a 56% greater density (Bmax) of adenosine A1 receptor in senescent than adult without differences in affinities (Kd). The increased sensitivity of senescent RA to the negative chronotropic effects of adenosine A1 receptor stimulation suggests a role for adenosine in abnormal sinus node function that occurs more frequently with age. Adenosine A1 receptor stimulation has more effect on relaxation than contraction in senescent LA compared with LA from adult F344 rats. However, the increase in density of adenosine A1 receptors suggests a functional dissociation between the availability of binding sites and receptor activation.

Adenosine↗
PubMed1988

Involvement of ANF in the acute antidiuresis during PEEP ventilation.

To investigate the potential role of natriuretic factor (ANF) on changes on renal excretory function in response to increased intrathoracic pressure, seven patients were studied during three successive 60-min periods of 1) mechanical ventilation (MV) and zero end-expiratory pressure (ZEEP), 2) MV with 12 cmH2O positive end-expiratory pressure (PEEP), and 3) MV with the same level of PEEP while lower-body positive pressure (LBPP) was applied to restore venous return and increase central blood volume without fluid loading. Hemodynamics, renal excretory function parameters, and plasma immunoreactive atrial natriuretic factor (irANF) levels were recorded at the end of each period. Compared with ZEEP, PEEP induced a significant reduction of diuresis (from 134 +/- 17 to 59 +/- 13 ml/h, P less than 0.01) and natriuresis (from 8.37 +/- 3.5 to 3.83 +/- 2 mmol/h, P less than 0.01), whereas plasma irANF fell from 520 +/- 292 to 155 +/- 40 pg/ml (P less than 0.01) and transmural right atrial pressure decreased from 3.9 +/- 0.5 to 2.4 +/- 0.3 mmHg (P less than 0.01). Opposite changes were observed during application of LBPP, which restored diuresis and plasma irANF to near control ZEEP values, despite continuation of PEEP. Changes in renal excretory function parameters thus paralleled changes in right atrial pressure and plasma irANF. We suggest that changes in plasma irANF in response to hemodynamic variations induced by changes in intrathoracic pressure may contribute to alterations of renal excretory function during PEEP.

Adult↗
PubMedDate not supplied

[Magnetocardiographic markers of functional hemodynamic overloading of the right atrium].

Functional hemodynamic overloading of the right atrium can be caused by some of the dynamic factors in aviation and space flight. Our purpose was to disclose markers of the right atrium functional overloading in 6 normal males during the Stange test and Valsalva maneuver. Computerized magnetocardiography was fulfilled before (resting subjects), during and after (resting subjects) the breathing tests. Testing on a background of the flight dynamic factors resulted in a trend toward a more superficial Z-coordinate of the myocardium signal along the whole or a greater part of the atrial complex as compared with baseline measurements at rest. A supposition has been made that this Z coordinate alteration can be a marker of functional hemodynamic overloading of the right atrium associated with the breathing tests.

Adult↗
PubMed1982

[Diagnosis of right atrial infarction by esophageal echocardiography].

Atrial infarction is rare and its ante mortem diagnosis is difficult by electrocardiography. There has been no report concerning the diagnosis of atrial infarction by echocardiography because it is difficult to observe atrial motion by conventional echocardiography. This report deals with a case of probable right atrial infarction diagnosed by esophageal echocardiography. A 50-year-old man was admitted to our hospital under the diagnosis of acute infero-posterior myocardial infarction. Swan-Ganz catheterization data revealed dip and plateau pattern with elevated right atrial pressure suggesting complicated right ventricular infarction. In the esophageal echocardiograms recorded one month later, the motion of the right atrial anterior wall was akinetic and right atrial dimension did not change during both atrial contraction phase and atrial filling phase. These findings suggest impairment of pump function and reservoir function of the right atrium. Amplitudes of the interatrial septum during atrial filling phase and atrial contraction phase were in the lower limit of normal range. Total occlusion of the right coronary artery was proven by coronary arteriography. Hypokinesis of the upper right atrial appendage was suspected by right atriography and maximal right atrial volume was as large as 116 ml. In the right atrial volume curve by cardiac scintigraphy, fractional emptying was as low as 28%. The patient had an uneventful recovery and returned to full-time works, so that pathological diagnosis was not obtained, but the clinical diagnosis of right atrial infarction was strongly suspected by the clinical findings mentioned above. It was concluded that the esophageal echocardiography is mandatory to observe atrial wall motion abnormality whenever atrial infarction is suspected.

Echocardiography↗
PubMed1995

Hemodynamics of different degrees of right heart bypass: experimental assessment.

BACKGROUND: Although their assessment could be of the utmost importance to determine the surgical treatment for patients with univentricular hearts, differences in ventricular performance between partial and complete right heart bypass remain to be defined. METHODS: Three different degrees of right heart bypass were investigated in 5 mongrel dogs: (1) superior vena cava to both pulmonary arteries shunt (SCP); (2) inferior vena cava to both pulmonary arteries shunt (ICP); and (3) both venae cavae to both pulmonary arteries shunt (BCP). Hemodynamic studies included evaluation of the cardiac index and left atrial pressure as a function of the degree of right heart bypass. RESULTS: By maintaining the mean left atrial pressure at 5 mm Hg, cardiac indexes were 1.98 +/- 0.25, 1.67 +/- 0.29, and 1.33 +/- 0.21 L.min-1.m-2 for SCP, ICP, and BCP shunts, respectively (p = 0.001). When keeping the cardiac index constant, mean left atrial pressures were 5.2 +/- 0.8, 5.5 +/- 0.9, and 7 +/- 0.7 mm Hg for SCP, ICP, and BCP shunts, respectively (p = 0.001). CONCLUSIONS: Increasing degrees of right heart bypass are associated with a significant decrease in ventricular performance in this experimental model.

Animals↗
PubMed1988

Cineangiographic spectrum of Ebstein's malformation: its relevance to clinical presentation and outcome.

Eight heart specimens were examined that had concordant connections of the cardiac segments and exhibited Ebstein's malformation. The displacement of the leaflets of the tricuspid valve from the atrioventricular junction varied from minimal and isolated involvement of the septal leaflet to involvement of the mural and anterosuperior leaflets as well. This resulted in a wide range of physiologic "atrialization" of the right ventricle. The distal insertion of the valve leaflets also exhibited a spectrum of malformation. At one end the insertion was the normal focal variety, allowing free communication between the atrialized and functional parts of the right ventricle. At the other end there was abnormal linear attachment of the anterosuperior and mural leaflets to an anomalous muscular shelf at the junction between the inlet and apical trabecular portions of the right ventricle. The anteromedial commissure between the anterosuperior and the displaced septal leaflets provided a "keyhole" communication between the two ventricular compartments. Between these extremes were cases in which hyphenations along a locus of linear attachment allowed additional communications between the ventricular compartments. In light of these anatomic observations, cineangiograms of 26 patients with Ebstein's malformation were reviewed retrospectively. It was possible to classify the patients into three groups with focal, hyphenated and linear attachment, respectively. Size, ejection and displacement indexes of the functional right ventricle measured from the angiograms suggested that the severity of the malformation increased from focal attachment through hyphenated to linear attachment. Clinical observations relative to symptoms (cyanosis at rest, reduced exercise tolerance) and outcome supported this morphologic-angiographic grading.

Child↗
PubMed1983

Functional characteristics of sinoatrial and subsidiary pacemaker activity in the canine right atrium.

A canine in vitro right atrial preparation was developed to study the functional characteristics of subsidiary atrial pacemaker (SAP) activity and to compare them with those of sinoatrial node (SAN) activity. Extracellular bipolar electrodes were used to estimate the site of earliest activation and monitor spontaneous rate. Ligation of the SAN artery at the midportion of the sulcus terminalis suppressed SAN activity and usually (73.5%) elicited SAP activity in a well-defined region of the inferior atrium. SAP activity in this region required a "threshold" concentration of norepinephrine (10(-8) M) in the Tyrode's perfusate. In response to all concentrations of norepinephrine tested, SAN activity attained a greater maximum spontaneous rate than SAP activity. Cholinergic stimulation with acetylcholine or eserine elicited a greater negative chronotropic response from SAP than SAN activity. Overdrive pacing suppressed SAP activity to a significantly greater extent than SAN activity. We conclude that this in vitro preparation can be useful for studying the pharmacology and electrophysiology of subsidiary atrial pacemakers that emerge after suppression of SAN activity. In contrast to SAN activity, SAP activity requires norepinephrine and is more sensitive than SAN activity to acetylcholine and overdrive pacing. Consequently, after loss of SAN function, autonomic modulation of SAP activity may result in atrial dysrhythmias and prolonged periods of overdrive suppression.

Acetylcholine↗
PubMed1988

Acute volume loading, atrial natriuretic peptide release and cardiac function in healthy men. Effects of beta-blockade.

Release of ANP is dependent on right atrial distension and pressure, which in turn are dependent on both venous return and left ventricular function. These two latter parameters are both modulated by beta-receptors. In the present study, the effects of selective beta-blockade vs non-selective beta-blockade on hypertonic volume expansion induced changes in ANP release and systemic hemodynamics were assessed in 8 healthy normotensive male volunteers. On placebo, infusion of hypertonic saline (1200 ml of 2.5% NaCl) caused an intravascular volume expansion of 10-11%, and small non-significant increases in cardiac performance (LVEDV, SV, or CI), but it provoked a 2-fold increase in plasma ANP. Beta-blockade by either atenolol or propranolol blunted the increase in cardiac volume load (reflected by LVEDV) as compared to placebo, but did not affect the ANP response to volume expansion. The increase in ANP correlated closely with the intravascular volume expansion on placebo and to a lesser extent on beta-blockade. In healthy men, therefore, intravascular volume expansion that caused only small changes in cardiac activity, resulted in clear increases in release of ANP. Inhibition of the increase in cardiac volume load by beta-blockade did not interfere with ANP increase, suggesting a role for extra-cardiac receptors in the release of ANP or a change in the pressure/volume relationship.

Adrenergic beta-Antagonists↗
PubMed1991

Vascular factors in isovolumic systemic and pulmonary circuit.

Experiments were conducted in 12 pentobarbital-anesthetized dogs with sinus denervation and vagotomy. The chest was opened, and the heart was replaced by a roller pump with two perfusion lines. The systemic and pulmonary circulations (SC and PC) were perfused with a constant and adjustable flow (Q). Venous outflows were directly driven by pumps without passing through a reservoir. In each closed circuit, the total blood volume remained constant because inflow and outflow were simultaneously and equally altered. In both SC and PC, arterial pressure (Pa), i.e., systemic arterial and pulmonary arterial pressures (SAP and PAP), was a positive function of Q, and venous pressure (Pv), i.e., right atrial and left atrial pressures (RAP and LAP), was a negative function of Q. The first series of experiments involved three equal step reductions in Q from baseline to zero flow. The venous-to-arterial compliance ratio (Cv/Ca) was calculated from delta Pa/delta Pv and vascular resistance (VR) from (Pa - Pv)/Q. The values of Cv/Ca in SC increased from 9.3 +/- 0.4 to 14.5 +/- 1.1 and 21.9 +/- 1.4 (P less than 0.001) in the three-step Q reduction. VR in the SC was not significantly dependent on Q. In the PC, the Cv/Ca was approximately 2.0 and VR was 0.16 mmHg.ml-1.min.kg, both values being independent of Q. Multiple-step reduction in Q for regression equations was carried out in 8 of the 12 dogs. We found that only the SAP was a linear function of Q (ml.min-1.kg-1): SAP = 18.458 + 0.953Q.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Effect of the pericardium on atrial systolic function.

The effect of pericardial constraint on atrial systolic function was investigated in nine acutely instrumented anesthetized dogs. Left and right atrial pressures were recorded by high-fidelity catheters; auricular diameters and free wall segment lengths were measured by sonomicrometry. Atrial function curves were constructed by relating atrial systolic dimensional shortening to atrial end-diastolic pressure during progressive volume loading. With the pericardium closed, the function curves were shifted markedly downward and rightward, such that atrial systolic shortening was reduced at any given pressure. There was a concomitant leftward and upward shift of the atrial end-diastolic pressure-dimension relationship. The relationship between atrial systolic shortening and atrial end-diastolic dimension was not shifted. These results suggest that the apparent depression of atrial systolic function with the pericardium closed is due to a restrictive effect of the pericardium on atrial filling. In conclusion, in the acutely dilated heart, the pericardium restricts atrial filling and thus causes a reduction in atrial systolic contribution to ventricular filling.

Animals↗
PubMed1985

The influence of streptozotocin-induced diabetes on myocardial contractile performance in vitro.

The influence of streptozotocin-induced diabetes has been studied on rabbit isolated cardiac muscle responses to noradrenaline and calcium. Seven weeks after treatment with streptozotocin (70 mg/kg i.v.), right atrial contractile rate was found to be depressed, whereas left ventricular papillary muscle function was markedly enhanced. Neither the atrial nor the ventricular (papillary) muscle strip exhibited a remarkable alteration in sensitivity to noradrenaline. Although sensitivity to calcium was not altered in the atrial muscle, papillary muscle strips obtained from diabetic rabbits were supersensitive to calcium. These results suggest that in diabetic animals, right atrial pacemaker function is depressed, while ventricular muscle activity is enhanced. In the diabetic state, this enhanced ventricular muscle function is likely to be associated with an alteration in calcium utilization.

Animals↗