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PubMed2006

Effects of circumferential or segmental pulmonary vein ablation for paroxysmal atrial fibrillation on cardiac autonomic function.

BACKGROUND: Circumferential and segmental pulmonary vein ablations are two established treatment strategies for ablation of atrial fibrillation. Both techniques require the application of radiofrequency current at anatomical sites that are close to autonomic ganglia. However, the effects of current pulmonary vein ablation techniques on cardiac autonomic function are unknown. OBJECTIVE: The purpose of this study was to analyze the short- and long-term effects of circumferential and segmental pulmonary vein ablation on cardiac autonomic function. METHODS: One hundred patients with highly symptomatic atrial fibrillation were randomly assigned to undergo either circumferential or segmental pulmonary vein ablation. Holter recordings were recorded at baseline and at regular intervals for up to 1 year after ablation. Autonomic function was assessed by deceleration capacity and acceleration capacity of heart rate as well as by standard measures of heart rate variability. RESULTS: In the circumferential pulmonary vein ablation group, deceleration capacity and acceleration capacity decreased highly significantly from 5.7 +/- 2.1 ms and -8.0 +/- 1.9 ms at baseline to 3.3 +/- 1.8 ms and -5.5 +/- 2.3 ms directly after ablation, respectively (P<.00001). Impairment of deceleration capacity and acceleration capacity was present up to 1 year after ablation. In the segmental pulmonary vein ablation group, deceleration capacity and acceleration capacity decreased from 5.8 +/- 2.0 ms and -7.8 +/- 1.6 ms at baseline to 3.4 +/- 1.2 ms and -6.0 +/- 2.4 ms directly after ablation (P<.00001), respectively. However, deceleration capacity and acceleration capacity returned to baseline values within 1 month. CONCLUSIONS: Circumferential and segmental pulmonary vein ablations induce an immediate decrease of autonomic function. However, while this decrease is only transient with segmental pulmonary vein ablation, it persists with circumferential pulmonary vein ablation for at least 1 year.

Aged↗
PubMed2004

Left atrial conduit volume is generated by deviation from the constant-volume state of the left heart: a combined MRI-echocardiographic study.

Although modeling the four-chambered heart as a constant-volume pump successfully predicts causal physiological relationships between cardiac indexes previously deemed unrelated, the real four-chambered heart slightly deviates from the constant-volume state by ventricular end systole. This deviation has consequences that affect chamber function, specifically, left atrial (LA) function. LA attributes have been characterized as booster pump, reservoir, and conduit functions, yet characterization of their temporal occurrence or their causal relationship to global heart function has been lacking. We investigated LA function in the context of the constant-volume attribute of the left heart in 10 normal subjects using cardiac magnetic resonance imaging (MRI) and contemporaneous Doppler echocardiography synchronized via ECG. Left ventricular (LV) and LA volumes as a function of time were determined via MRI. Transmitral flow, pulmonary vein (PV) flow, and lateral mitral annular velocity were recorded via echocardiography. The relationship between the MRI-determined diastolic LA conduit-volume (LACV) filling rate and systolic LA filling rate correlate well with the relationship between the echocardiographically determined average flow rate during the early portion of the PV D wave and the average flow rate during the PV S wave (r = 0.76). We conclude that the end-systolic deviation from constant volume for the left heart requires the generation of the LACV during diastole. Because early rapid filling of the left ventricle is the driving force for LACV generation while the left atrium remains passive, it may be more appropriate to consider LACV to be a property of ventricular diastolic rather than atrial function.

Atrial Function, Left↗
PubMed1989

Transfer function analysis of autonomic regulation. I. Canine atrial rate response.

We present a useful technique for analyzing the various functional components that comprise the cardiovascular control network. Our approach entails the imposition of a signal with broad frequency content as an input excitation and the computation of a system transfer function using spectral estimation techniques. In this paper, we outline the analytical methods involved and demonstrate the utility of our approach in studying the dynamic behavior of the canine cardiac pacemaker. In particular, we applied frequency-modulated pulse trains to either the right vagus or the cardiac sympathetic nerve and computed transfer functions between nerve stimulation rate and the resulting atrial rate. We found that the sinoatrial node (and associated automatic tissue) responds as a low-pass filter to fluctuations in either sympathetic or parasympathetic tone. For sympathetic fluctuations, however, the filter has a much lower corner frequency than for vagal fluctuations and is coupled with a roughly 1.7-s pure delay. We further found that the filter characteristics, including the location of the corner frequency and rate of roll-off, depend significantly on the mean level of sympathetic or vagal tone imposed.

Algorithms↗
PubMed2003

Relationship between the frequency of paroxysmal episodes of atrial fibrillation and pulmonary venous flow pattern.

AIMS: Chronic atrial fibrillation causes mechanical remodelling of the atria, but it is uncertain whether self-terminating episodes of paroxysmal atrial fibrillation (PAF) alter atrial mechanical function during normal sinus rhythm. This study was designed to assess the relationship between the frequency of symptomatic arrhythmic episodes and pulmonary venous flow (PVF) pattern among patients with PAF. METHODS AND RESULTS: The effect of symptomatic arrhythmic episodes on PVF was studied in 85 patients with lone PAF (age 48+/-8 years, 66 men). PVF was measured with transthoracic echocardiography during sinus rhythm. Adequate recordings of PVF were achieved in 81 (95%) patients. Peak systolic PVF had an inverse correlation (r=-0.35, P=0.002) with the frequency of PAF episodes. The peak systolic PVF was 76+/-14 cm/s vs 62+/-12 cm/s (P=0.008) among the quartiles with the most and the least frequent episodes of PAF, respectively. There were no significant differences in the other echocardiographic measurements or demographic variables. CONCLUSIONS: Frequent arrhythmic episodes significantly diminished systolic PVF among patients with PAF, suggesting that PAF results in gradual mechanical remodelling of the atrium, which may favour recurrence and perpetuation of AF and/or formation of atrial thrombus.

Atrial Fibrillation↗
PubMed2001

Sinus pacemaker function after cardioversion of chronic atrial fibrillation: is sinus node remodeling related with recurrence?

INTRODUCTION: The objective of this study was to investigate the temporal changes in sinus node function in postcardioversion chronic atrial fibrillation (AF) patients and their possible relation with the recurrence rates of AF. METHODS AND RESULTS: In 37 chronic AF patients, internally cardioverted to sinus rhythm, corrected sinus node recovery time (CSNRT), and the pattern of corrected return cycle lengths were assessed 5 to 20 minutes and 24 hours after conversion. The last 20 consecutive patients also were evaluated after autonomic blockade. Twenty subjects with normal atrial structure and no history of AF served as the control group. Patients were followed-up for 1 month for recurrence, and the density of supraventricular ectopic beats per hour was obtained during the first 24 hours after conversion. Fifteen patients (40.5%) relapsed during follow-up. CSNRT values at 600 msec (371 +/- 182 msec) and 500 ms (445 +/- 338 msec) were significantly higher than those of control subjects (278 +/- 157 msec, P = 0.050, and 279 +/- 130 msec, P = 0.037, respectively). Significant temporal changes in CSNRT also were observed during the first 24 hours after conversion (600 msec: 308 +/- 120 msec, P = 0.034; 500 msec: 340 +/- 208 msec, P = 0.017). No significant interaction and temporal effects were observed with regard to corrected return cycle length pattern. Similar data regarding CSNRT and corrected return cycle length pattern were obtained after autonomic blockade. Patients with abnormal CSNRT after cardioversion had higher recurrence rates (50%) than those with normal function (37%; P = NS). Patients who relapsed had a higher density of supraventricular ectopic beats per hour (159 +/- 120) compared with those who did not (35 +/- 37; P = 0.001). CONCLUSION: Depressed sinus node function is observed after conversion of chronic AF. Recovery from this abnormality and its independence from autonomic function suggest that AF remodels the sinus node. Our data do not support a causative role of sinus node function in AF recurrence, but they do indicate such a role for the density of atrial ectopic beats.

Atrial Fibrillation↗
PubMed1994

Influence of the renin-angiotensin system and atrial natriuretic peptide on renal functional reserve.

We studied the renin-angiotensin system (RAS) and atrial natriuretic peptide (ANP) after amino acid loading in order to elucidate whether or not glomerular hyperfiltration is mediated by these hormones. Eight healthy controls without kidney disease (group 1), 8 renal graft recipients (group 2) and 8 patients after nephrectomy (group 3) were studied. Furthermore, we investigated the influence of amino acid loading on RAS and ANP and glomerular filtration during acute application of captopril in healthy controls. Clearances in insulin (CIn) and para-aminohippuric acid (CPAH) were determined during an infusion of 0.9% saline and during amino acid loading. CIn increased in healthy controls from 96.5 +/- 3.3 to 111.9 +/- 4.4 ml/min (p < 0.01), CPAH rose from 577 +/- 28.7 to 618.9 +/- 38 ml/min (p = NS). During the combined application of amino acid infusion and 25 mg captopril, CIN increased to 125.0 +/- 16.4 ml/min/1.73 m2 (p < 0.01) and there was no significant increase in CPAH which was 595 +/- 77 ml/min/1.73 m2. There was no significant change in renal vascular resistance, but filtration fraction increased from 17 +/- 1 to 19 +/- 1% under amino acid infusion and increased further under the application of captopril to 21 +/- 2% (p < 0.05). In renal graft recipients, CIn had a tendency to increase during amino acid infusion from 78.4 +/- 5.8 to 84.7 +/- 6.5 ml/min (p = NS). In patients after nephrectomy, CIn did not increase (84.5 +/- 6 ml/min) but CPAH did from 345.7 +/- 26.3 to 409 +/- 24.1 ml/min (p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Venous function of the leg during atrial arrhythmias.

Venous volume and venous outflow of the calf were studied with strain gauge plethysmography during atrial fibrillation or atrial flutter and after conversion to sinus rhythm in 28 patients. These parameters increased significantly after conversion to sinus rhythm and the increase was more pronounced in patients with organic heart disease compared to patients without. It is concluded that atrial arrhythmia is associated with an altered venous function, which may compensate for the fall in cardiac output induced by the arrhythmia and also may be a risk factor for deep vein thrombosis in patients with organic heart disease.

Aged↗
PubMed2005

Left atrial systolic reserve in idiopathic vs. ischaemic-dilated cardiomyopathy.

PURPOSE: There are studies indicating more pronounced left atrial (LA) systolic dysfunction at rest in idiopathic (IDDC) than in ischaemic-dilated cardiomyopathy (ISDC). It was hypothesized that the findings would be similar with regards LA systolic reserve. METHODS: Twenty-six patients with IDDC, 28 with ISDC and 25 normal controls underwent low-dose dobutamine stress echocardiography (5-10 microg kg(-1) min(-1) IV). Left atrial volumes were echocardiographically determined at rest and during stress at the mitral valve opening (maximal, Vmax), electrocardiographic P wave (onset of atrial systole, Vp) and mitral valve closure (minimal, Vmin) from the apical 4- and 2-chamber views (biplane area-length method). Left atrial systolic function was assessed with the LA-active emptying volume (ACTEV) = Vp-Vmin and fraction (ACTEF) = ACTEV/Vp. RESULTS: Vmax at rest was similar in IDDC and ISDC and greater than in the controls (54.2 +/- 12 vs. 48.5 +/- 18 vs. 27.1 +/- 6.3 cm(3) m(-2), respectively, P < 0.001) and did not change with stress (53.9 +/- 13.8 vs. 46.9 +/- 16.2 vs. 25.8 +/- 5.9 cm(3) m(-2), P < 0.001). The ACTEV at rest was similar in IDDC and ISDC and greater than in the controls (8.6 +/- 3.5 vs. 9.7 +/- 2.9 vs. 6.1 +/- 2.2 cm(3) m(-2) P < 0.01), whereas during the dobutamine infusion it remained unaltered in IDDC (10.8 +/- 4.6 cm(3) m(-2), P = NS vs. rest) and increased in ISDC (11.8 +/- 3.3 cm(3) m(-2), P < 0.05) and the controls (13.1 +/- 3.2 cm(3) m(-2), P < 0.01). The ACTEF was lower in IDDC than ISDC and the controls at rest (20 +/- 10% vs. 33 +/- 8% vs. 36 +/- 10%, P < 0.01). Dobutamine infusion was associated with no significant increase in ACTEF in IDDC (25 +/- 12%, P = NS vs. rest), and with an increase in this variable in ISDC (39 +/- 10%, P < 0.05) and the controls (49 +/- 12%, P < 0.01). CONCLUSIONS: Dobutamine infusion is associated with an increase in LA ACTEV and fraction in ISDC and no significant change in these indices in IDDC. These findings indicate a reduced LA systolic reserve in IDDC.

Adult↗
PubMed2003

[Left ventricular function in adult patients after the atrial switch operation for transposition of the great arteries].

OBJECTIVES: Right ventricular function may deteriorate after the atrial switch operation in patients with transposition of the great arteries, but the effect on left ventricular function is unknown. Chronic left ventricular function was evaluated in adult patients after the atrial switch operation for transposition of the great arteries. METHODS: Right and left ventricular functions were evaluated using data from cardiac catheterization performed in nine patients older than 17 years who had undergone the atrial switch operation for transposition of the great arteries. The mean age at operation was 19 +/- 16 months and the age at catheterization ranged from 17 to 32 years (mean age 23 +/- 5 years). Echocardiography was performed in all patients to evaluate tricuspid regurgitation. Myocardial perfusion studies using technetium-99 m-tetrofosmin were assessed in five patients. RESULTS: Mean right ventricular end-diastolic volume was slightly increased to 122 +/- 27% of the normal value and mean right ventricular ejection fraction was depressed to 44 +/- 5% of the normal value. Left ventricular ejection fraction ranged from 37% to 63% (mean 50 +/- 7%) and was under 50% in four of the nine (44%) patients. Right ventricular ejection fraction was positively correlated with left ventricular ejection fraction(r = 0.72, p < 0.05). All patients had tricuspid regurgitation, mild in four, moderate in four, and severe in one patient. Left ventricular ejection fraction was lower in patients with moderate or severe tricuspid regurgitation(54 +/- 4%) than in patients with mild tricuspid regurgitation(47 +/- 6%, p < 0.05). Mild or moderate perfusion abnormalities were observed in all patients (five of five) who underwent myocardial perfusion studies. Mean right and left ventricular ejection fractions were 43 +/- 3% and 50 +/- 3%, respectively, in patients who underwent myocardial perfusion study, which were under the normal levels. CONCLUSIONS: Left ventricular dysfunction is common in adult patients after the atrial switch operation for transposition of the great arteries. Some right ventricular abnormalities may correlate with the left ventricular dysfunction.

Adolescent↗
PubMed1999

[Left ventricle function after the reversion of atrial fibrillation].

INTRODUCTION: Atrial fibrillation could be a consequence of heart failure as well as arrhythmia may cause deterioration of left ventricle systolic function. There are also studies suggested that atrial fibrillation promote left ventricle diastolic dysfunction. AIM OF STUDY: Assessment of left ventricle diastolic function in patients with sustained sinus rhythm during six months observation after reversion of atrial fibrillation. MATERIAL AND METHODS: The study group comprised 30 patients, which had stabilized sinus rhythm at least six months after successful reversion of atrial fibrillation. Transthoracical and transesophageal echocardiography in all patients was performed during atrial fibrillation, immediately after reversion of arrhythmia and after six months observation without reoccurrence of atrial fibrillation. The transthoracical echocardiographic parameters characterising left ventricle diastolic function was measured: E ampl LV, E acct LV, E dcct LV, E time LV, E intg LV. Consequently TEE was performed with Doppler probe in left superior pulmonary vein and following parameters were recorded: PVD, PVD intg, PVD dcct. RESULTS: The E ampl LV immediately after sinus rhythm restoration significantly decreased and was similar to values recorded during atrial fibrillation. After six months observation further significant decreasing of this parameter was noted. The E intg LV was markedly smaller after arrhythmia reversion and did not changed during six months period of sustained sinus rhythm. The E acct LV remained almost the same in all points of study. Whereas the E dcct LV and E time LV were only slightly longer just after reversion the values recorded after six months observation were significantly greater compared to both values before and immediately after sinus rhythm restoration. PVD and PVD intg increased just after sinus rhythm restoration but not significantly. During six months observation their values markedly decreased compared to measurements during atrial fibrillation and were slightly smaller than at first hour of sinus rhythm. PVD dcct insignificantly decreased just after sinus rhythm restoration. Stabilization of sinus rhythm for six months has allowed for significant increasing of this parameter. CONCLUSIONS: Left ventricle diastolic parameters in patients with atrial fibrillation do not significantly change immediately after sinus rhythm restoration. Maximal mitral early diastolic flow velocity and maximal diastolic flow velocity in pulmonary veins markedly decrease at six months observation after reversion of atrial fibrillation, whereas both deceleration time of early diastolic mitral flow and deceleration time of diastolic pulmonary flow became longer and than this indices don't differ from control group without arrhythmia in anamnesis.

Aged↗
PubMed2001

The contribution of ionic currents to changes in refractoriness of human atrial myocytes associated with chronic atrial fibrillation.

OBJECTIVE: To investigate changes in human atrial single cell functional electrophysiological properties associated with chronic atrial fibrillation (AF), and the contribution to these of accompanying ion current changes. METHODS: The whole cell patch clamp technique was used to record action potentials, the effective refractory period (ERP) and ion currents, in the absence and presence of drugs, in enzymatically isolated myocytes from 11 patients with chronic (>6 months) AF and 39 patients in sinus rhythm. RESULTS: Stimulation at high rates (up to 600 beats/min) markedly shortened late repolarisation and the ERP in cells from patients in sinus rhythm, and depolarised the maximum diastolic potential (MDP). Chronic AF was associated with a reduction in the ERP at physiological rate (from 203+/-16 to 104+/-15 ms, P<0.05), and marked attenuation in rate effects on the ERP and repolarisation. The abbreviated terminal phase of repolarisation prevented fast rate-induced depolarisation of the MDP in cells from patients with AF. The density of L-type Ca(2+) (I(CaL)) and transient outward K(+) (I(TO)) currents was significantly reduced in cells from patients with AF (by 60-65%), whilst the inward rectifier K(+) current (I(K1)) was increased, and the sustained outward current (I(KSUS)) was unaltered. Superfusion of cells from patients in sinus rhythm with nifedipine (10 micromol/l) moderately shortened repolarisation, but had no effect on the ERP (228+/-12 vs. 225+/-11 ms). 4-Aminopyridine (2 mmol/l) markedly prolonged repolarisation and the ERP (by 35%, P<0.05). However, the combination of these drugs had no effect on late repolarisation or refractoriness. CONCLUSION: Chronic AF in humans is associated with attenuation in adaptation of the atrial single cell ERP and MDP to fast rates, which may not be explained fully by accompanying changes in I(CaL) and I(TO).

4-Aminopyridine↗
PubMed1988

Involvement of Ni protein in the functional coupling of the atrial natriuretic factor (ANF) receptor to adenylate cyclase in rat lung plasma membranes.

In the presence of 1 microM atrial natriuretic factor (ANF) and low (0.1 mM) Mg2+ concentrations, the initial rate of binding of [3H]guanosine 5'-[beta, gamma-imido)triphosphate [( 3H]p[NH]ppG) to rat lung plasma membranes was increased twofold to threefold. ANF-dependent stimulation of the initial rate of [3H]p[NH]ppG binding was reduced at high (5 mM) Mg2+ concentrations. Preincubation of membranes with p[NH]ppG (5 min at 37 degrees C) eliminated the ANF-dependent effect on [3H]p[NH]ppG binding whereas ANF-dependent [3H]p[NH]ppG binding was unaffected by similar pretreatment with guanosine 5'-[beta-thio]diphosphate (GDP[beta S]). An increase in ANF concentration from 10 pM to 1 microM caused a 40% decrease in forskolin-stimulated or isoproterenol-stimulated adenylate cyclase activities (IC50 5 nM) in rat lung plasma membranes. GTP (100 microM) was obligatory for the ANF-dependent inhibition of adenylate cyclase, which could be completely overcome by the presence of 100 microM GDP[beta S] or the addition of 10 mM Mn2+. Reduction of Na2+ concentration from 120 mM to 20 mM had the same effect. Pertussis toxin eliminated ANF-dependent inhibition of adenylate cyclase by catalyzing ADP-ribosylation of membrane-bound Ni protein (41-kDa alpha subunit of the inhibitory guanyl-nucleotide-binding protein of adenylate cyclase). The data support the notion that one of the ANF receptors in rat lung plasma membranes is negatively coupled to a hormone-sensitive adenylate cyclase complex via the GTP-binding Ni protein.

Adenosine Diphosphate Ribose↗
PubMed1999

Evaluation of the Left Atrial Performance Using Acoustic Quantification.

In most clinical studies, evaluation of left atrial (LA) function evolved from estimation of LA size on chest radiograph, electrocardiographic P wave abnormalities, LA diameter determined at fluoroscopy or by echocardiography, LA pressure recordings, blood flow velocity with Doppler echocardiography, and measurements of LA volume based on echocardiographic, cineangiographic, radionuclide, and magnetic resonance imaging techniques. The recent development of real-time two-dimensional echocardiographic acoustic quantification (AQ) suggests that LA dimensions can be measured instantaneously to provide online assessment of its systolic and diastolic functions. By means of AQ echocardiography and simultaneous recordings of LA pressure, the LA pressure-area relation can be obtained. LA pressure-area relation consisted of two loops: the A loop, representing the LA pump function, and the V loop, representing LA reservoir and passive emptying functions. The importance of LA function has been demonstrated in congestive heart failure, atrial fibrillation, hypertension, and ischemic heart disease and during pacing or dobutamine infusion.

Journal Article↗
PubMed1970

Abnormal left heart function after operation for atrial septal defect.

Post-operative data have been presented in seven patients with atrial septal defect. In five of them, residual patency of the atrial septum was found at cardiac catheterization, but in two the defect had been closed. All showed evidence of 'left-sided dysfunction', expressed either as an increase in the pulmonary arterial wedge pressure or the left ventricular end-diastolic pressure or both. The reasons for these findings are not clear, though in several there were indications of impaired right ventricular compliance and possible transmission of raised right-sided pressures to the left side of the heart through a still patent atrial septum. This could not, however, be the mechanism in all cases, and dysfunction of the left ventricle has been seen in two patients in whom the defect was securely closed. The cause of this phenomenon in these selected cases remains obscure.

Adult↗