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PubMed1993

Preload dependency of left atrial pump function in hypertrophic cardiomyopathy.

In our previous study, we reported that the left atrial contribution to left ventricular filling was decreased to a greater extent in patients with hypertrophic cardiomyopathy than in those with myocardial infarction or normal subjects during lower body negative pressure (LBNP)-induced preload reduction. To clarify the factors responsible for this difference in response, we examined changes in left atrial hemodynamic and M-mode echocardiographic indices during LBNP in patients with hypertrophic cardiomyopathy and myocardial infarction. The same degree of decrease in left atrial preload and afterload was found in both groups. Moreover, we detected no change in the left atrial fractional shortening during left atrial systole (%LAFS) in patients with hypertrophic cardiomyopathy, in contrast to a significant increase found in patients with myocardial infarction. These results showed that the greater decrease in the left atrial contribution in hypertrophic cardiomyopathy during LBNP could not result from differences in changes in left atrial preload or afterload, suggesting that it may be closely related to limitations in the compensatory augmentation of left atrial contractility.

Atrial Function, Left↗
PubMed2003

Color Doppler tissue imaging to evaluate left atrial appendage function in mitral stenosis.

Two-dimensional color Doppler tissue imaging (CDTI) has so far been used, in general, to evaluate ventricular function. This study examined if the left atrial appendage tissue velocity could reproducibly be measured with CDTI and if they have any predictive value for left atrial appendage (LAA) function and former thromboembolism. Thirty-six patients (24 women, 12 men; mean age 45 +/- 12 years; 18 AF; 11 former thromboembolic stroke) with mitral stenosis undergoing transesophageal echocardiography were examined with CDTI. Peak systolic tissue velocity (m/sec, peak systolic velocity [PSV]) was measured at the tip of the LAA in the basal short-axis view. LAA flow emptying (LAAEV) and filling (LAAFV) velocities (m/sec) were also recorded 1 cm immediately below the orifice of the appendage. Interobserver and intraobserver variabilities were determined for the PSV. LAA ejection fraction was measured by Simpson's method. Mitral regurgitation, AF, transmitral mean gradient, left ventricular ejection fraction, mitral valve area, and left atrial diameter were used as a covariant for adjustment. The intraobserver and interobserver correlation coefficients for the PSV using CDTI was 0.64 and 0.60, respectively (bothP = 0.01). LAAEV(0.29 +/- 0.09 vs 0.19 +/- 0.04, P = 0.001)and LAA ejection fraction(44 +/- 12 vs 29 +/- 14, P = 0.004)were found to be significantly decreased in the patients with decreased PSV (<0.05 m/sec), even after adjustment. The decreased PSV was positively correlated with the low LAAEV (<0.25 m/sec) and history of thromboembolism (r = 0.59, r = 0.38, respectively), and remained a significant determinant of the low LAAEV (OR 50.03, CI 1.46-1738.11,P = 0.02), but not of history of thromboembolism (OR 4.29, CI 0.52-35.01,P = 0.08) after adjustment. In conclusion, these results suggest that CDTI provides a reproducible method for quantification of contraction at the tip of the LAA. Decreased PSV may be predictive of poor LAA function.

Adult↗
PubMed2003

Determinants of LV diastolic function during atrial fibrillation: beat-to-beat analysis in acute dog experiments.

Left ventricular (LV) diastolic function during atrial fibrillation (AF) remains poorly understood due to the complex interaction of factors and beat-to-beat variability. The purpose of the present study was to elucidate the physiological determinants of beat-to-beat changes in LV diastolic function during AF. The RR intervals preceding a given cardiac beat were measured from the right ventricular electrogram in 12 healthy open-chest mongrel dogs during AF. Doppler echocardiography and LV pressure and volume beat-to-beat analyses were performed. The LV filling time (FT) and early diastolic mitral inflow velocity-time integral (E(vti)) were measured using the pulsed Doppler method. The LV end-diastolic volume (EDV), peak systolic LV pressure (LVP), minimum value of the first derivative of LV pressure curve (dP/dt(min)), and the time constant of LV pressure decay (tau) were evaluated with the use of a conductance catheter for 100 consecutive cardiac cycles. Beat-to-beat analysis revealed a cascade of important causal relations. LV-FT showed a significant positive linear relationship with E(vti) (r = 0.87). Importantly, there was a significant positive linear relationship between the RR interval and LV-EDV in the same cardiac beat (r = 0.53). Consequently, there was a positive linear relationship between LV-EDV and subsequent peak systolic LVP (r = 0.82). Furthermore, there were significant positive linear and negative curvilinear relationships between peak systolic LVP and dP/dt(min) (r = 0.95) and tau (r = -0.85), respectively, in the same cardiac beat. In addition, there was a significant negative curvilinear relationship between dP/dt(min) and tau (r = -0.86). We have concluded that the determinants of LV diastolic function in individual beats during AF depend strongly on the peak systolic LVP. This suggests that the major benefit of slower ventricular rate appears related to lengthening of LV filling interval, promoting subsequent higher peak systolic LVP and greater LV relaxation.

Animals↗
PubMed1994

Clinical implications of left atrial appendage function: its influence on thrombus formation.

This study evaluated the relation between left atrial appendage (LAA) function and LAA spontaneous echo contrast (SEC) or thrombus formation. Seventy-five patients (45 men and 30 women, aged 14-79 years) referred for transesophageal echocardiography (TEE) were examined for LAA area (maximal and minimal), LAA ejection fraction ([LAA maximal area--LAA minimal area]/LAA maximal area), LAA peak emptying velocity, and these patients were classified into three groups by different LAA blood flow patterns: Group 1--25 patients with well-defined biphasic configuration of LAA flow; Group 2--28 patients with multiphasic configuration of LAA flow; Group 3--22 patients with very low LAA blood flow and, sometimes, barely detected Doppler signal. All the 25 patients in Group 1 had a sinus rhythm during TEE study, while the other 50 patients in Groups 2 and 3 were in atrial fibrillation. The patients in Group 3 had the lowest LAA ejection fraction and the lowest peak emptying velocity of these three groups. LAA SEC was present in five of 28 patients in Group 2 and 14 of 22 patients in Group 3, but in none of 25 patients in Group 1 (P < 0.001). LAA thrombus was present in one of 25 patients in Group 1, two of 28 patients in Group 2, and seven of 22 patients in Group 3 (P < 0.05). In conclusion, this study found that patients with poor LAA function, which was represented by lower LAA ejection fraction and lower peak emptying velocity, had higher incidence of LAA SEC or thrombus formation.

Adolescent↗
PubMed1995

Left atrial spontaneous echo contrast in patients with rheumatic mitral valve disease in sinus rhythm. Implication of an altered left atrial appendage function in its formation.

Thirty-nine patients who had rheumatic mitral valve disease in sinus rhythm were studied to compare echocardiographic and hemodynamic characteristics between those with and without left atrial (LA) spontaneous echo contrast. Patients were divided into two groups according to the presence (group 1, n = 17) or absence (group 2, n = 22) of the echo contrast. Transthoracic echocardiography and transesophageal echocardiography were performed in all patients within 1 week of cardiac catheterization study. Group 1 patients (5 men and 12 women; mean age, 47.7 +/- 13.1 years) showed smaller mitral valve area, greater transmitral valve pressure gradient, and absence of moderate to severe mitral regurgitation compared with group 2 patients (7 men and 15 women; mean age, 47.8 +/- 14.3 years). There was no significant difference in LA dimension, left ventricular end-systolic and end-diastolic dimensions, or in left ventricular ejection fraction between the two groups of patients. Left atrial appendage function was studied with Doppler in 26 patients. Patients (n = 10) with LA spontaneous echo contrast had significantly lower LA appendage ejection fraction (20.34 +/- 10.76% vs 34.16 +/- 13.13%; p < 0.05) and lower LA appendage peak emptying velocity (0.17 +/- 0.09 m/s vs 0.27 +/- 0.12 m/s; p < 0.05) than those (n = 16) without echo contrast. It is concluded that obstruction to mitral flow and altered LA appendage contractile function, not the LA size, are likely to be more important factors for the development of LA and LA appendage spontaneous echo contrast in patients with rheumatic mitral valve disease (predominant mitral stenosis) who are in sinus rhythm. These findings further substantiate that blood stasis in the LA cavity and the LA appendage is the mechanism fundamental to the formation of such spontaneous echo contrast.

Adult↗
PubMed1983

Function of atrial preferential conduction routes under normal and abnormal conditions.

The function of the atrial preferential conduction routes was examined by the microelectrode technique under normal and abnormal conditions in excised rabbit hearts. The sinus impulse during normal conditions traveled faster along the left and the right branch of the crista terminalis (anterior and posterior preferential routes, respectively) in the atrium toward the A-V node. Cutting of either route caused a delay of the impulse arrival in the zone beyond the lesion. The internodal conduction time was delayed 12 msec upon cutting of the posterior route, but there was no conduction delay after cutting the anterior route. This indicates that the posterior path is the dominant conduction route under normal conditions. When both routes were cut, the internodal conduction time was delayed 33 msec from the control value. During abnormal conditions, an ectopic pacemaker was found to occur mainly in the regions of two routes, as well as in the coronary sinus region. The cutting of either route, combined with the application of acetylcholine or high external K+, resulted in easier provocation of re-entrant arrhythmias in response to premature-stimuli than before the cutting.

Animals↗
PubMed1997

[The influence of electrical cardioversion on left ventricular systolic function, left atrial size, ANP levels and enzymatic activity of CPK and CD-MB in serum of patients with paroxysmal atrial fibrillation].

OBJECTIVE: To estimate the influence of electrical cardioversion on the left ventricular systolic function, left atrial size, the plasma activity of creatinine phosphokinase (CPK) and its myocardial fraction (CK-MB) and plasma level of atrial natriuretic peptide (ANP) in patients with paroxysmal atrial fibrillation caused by coronary artery disease, hypertension or mitral valve disease. PATIENTS: The study underwent 36 patients with paroxysmal atrial fibrillation of mean duration 24.5 hours in which sinus rhythm was restored by electrical cardioversion. METHODS: Plasma activity of creatinine phosphokinase (CPK) and its myocardial fraction (CK-MB), plasma level of atrial natriuretic peptide (ANP) and echocardiographic examination were obtained before and 24 hour after electrical cardioversion. During echocardiographic examination were measured left ventricular end diastolic diameter (LVEDD), left ventricular ejection fraction (LVEF), left atrial size (LA) and early diastolic velocity(E) and velocity with atrial contraction (A) of left ventricular inflow. Electrical cardioversion was initiated with impulse of 100 J. If it failed to convert atrial fibrillation to sinus rhythm next impulse of 200 J and 360 J were consequently applied. RESULTS: In all subgroups of patients formed dependently on a number of electrical shocks, 24 hour after cardioversion significant increase in left ventricular ejection fraction (LVEF) and decrease in plasma level of ANP were noted. In subgroup of patients treated with 1 (100 J) and 2 (100 + 200 J) impulse significant decrease in left atrial size was found out. The increase in plasma activity of creatinine phosphokinase (CPK) and its myocardial fraction (CK-MB) was confined to the subgroup treated with 3 (100 + 200 + 360 J) impulses. No changes in left ventricular end diastolic diameter (LVEDD) and early velocity (E) of left ventricular inflow 24 hours after cardioversion were observed. In all patients electrical cardioversion brought about the appearance of atrial wave of left ventricular inflow. No differences in estimated parameters between patients with coronary artery disease, hypertension and mitral valve disease were observed. Significant positive correlation between plasma level of ANP and left atrial size before (r = 0.69, p < 0.001) and after cardioversion (r = 0.68, p < 0.0001) were found. CONCLUSIONS: Restoration of the sinus rhythm in patients with paroxysmal atrial fibrillation leads to the increase in left ventricular ejection fraction (LVEF) and to the decrease in left atrial size (LA) and the plasma level of atrial natriuretic peptide. Left atrial size and plasma level of ANP are related. The cardioversion with impulses of high energy increases the plasma activity of creatinine phosphokinase and its myocardial fraction.

Adult↗
PubMed1995

Aggravation of postcardioversion atrial dysfunction by sotalol.

OBJECTIVES: This study determined the effect of sotalol on atrial function after electrical cardioversion of atrial fibrillation. BACKGROUND: After electrical cardioversion of atrial fibrillation, the Doppler mitral A wave is often diminished, representing impaired atrial contractile function. Sotalol is an effective atrial antiarrhythmic drug with class III and beta-adrenergic blocking properties. Although the negative inotropic effect of sotalol on the ventricle is minimal in patients with normal ventricular function, it may manifest negative inotropy when ventricular function is impaired. We postulated that after cardioversion, when intrinsic atrial function is impaired, sotalol may have an adverse effect on the atrium. METHODS: Thirty-seven patients enrolled in a randomized, double-blind study of sotalol for maintenance of sinus rhythm were studied by quantitative Doppler echocardiography within 24 h of electrical cardioversion and, for those still in sinus rhythm, again at 1 month. Doppler variables (E and A wave velocities and integrals) in patients receiving sotalol were compared with those in patients receiving placebo. RESULTS: After electrical cardioversion, peak A wave velocity and A wave time-velocity integral in the 20 patients receiving placebo were reduced compared with normal values. In the 17 patients receiving sotalol (median dose 320 mg twice daily) these variables were further reduced (mean [+/- SD] peak A wave velocity 19.4 +/- 5.5 vs. 38.4 +/- 14.7 cm/s, p < 0.001 and mean A wave time-velocity integral 1.7 +/- 0.6 vs. 3.4 +/- 1.4 cm, p < 0.001, in sotalol- vs. placebo-treated patients, respectively). Early diastolic filling (E wave variables) did not differ between sotalol- and placebo-treated groups. At 1 month, five sotalol- and six placebo-treated patients remained in sinus rhythm, and A wave variables had increased for the whole group, with a greater increase in sotalol-treated patients. CONCLUSIONS: After electrical cardioversion, when atrial stunning is prominent, sotalol has a negative atrial inotropic effect. This effect may be temporary, as suggested by resolution at 1 month. Negative inotropic effects of antiarrhythmic drugs on the atrium should be considered in assessing Doppler variables of left ventricular filling.

Adult↗
PubMed1999

Left atrial systolic function is depressed in idiopathic and preserved in ischemic dilated cardiomyopathy.

BACKGROUND: Left atrial systolic dysfunction, unexplained by altered loading conditions, has been reported in idiopathic dilated cardiomyopathy suggesting left atrial involvement in the myopathic process. MATERIALS AND METHODS: Seventeen patients with idiopathic dilated cardiomyopathy, 16 with ischemic dilated cardiomyopathy and 18 normal controls were studied with transthoracic echocardiography and cardiac catheterization. Transmitral diastolic flow was evaluated with pulsed Doppler. Left atrial volume (cm3/m2) at mitral valve opening (maximal, Vmax.), onset of atrial systole (P wave of the electrocardiogram, Vp), and mitral valve closure (minimal, Vmin. ) was determined with two-dimensional echocardiography using the biplane area-length method. The left atrial active emptying fraction (ACTEF = [Vp-Vmin.] x 100/Vp) served as an index of systolic function. RESULTS: The peak early diastolic transmitral flow velocity (cm/sec) was similar in the three groups (idiopathic: 60 +/- 16, ischemic: 58 +/- 20, control: 56 +/- 22; P = NS), whereas the late diastolic transmitral flow velocity was lower but not significantly different in idiopathic compared to ischemic cardiomyopathy, and in both was lower than control (26 +/- 12 vs. 34 +/- 13 vs. 44 +/- 14, respectively; P < 0.05). Vmax. and Vp were similar in idiopathic and ischemic cardiomyopathy and greater than control (44.6 +/- 13.6 vs. 48.2 +/- 18.3 vs. 26.9 +/- 6.2; P < 0.05, and 34.6 +/- 13.4 vs. 30.8 +/- 10.9 vs. 16.7 +/- 3.7, respectively; P < 0.05). ACTEF was lower in idiopathic than in ischemic cardiomyopathy and in the latter it was similar to control (18 +/- 10% vs. 32 +/- 10% vs. 36 +/- 10%, respectively; P < 0.05). Moreover, ACTEF was inversely related to left atrial tension at end-of atrial systole both in idiopathic and in ischemic cardiomyopathy (r2 = 0.52, P = 0.001 and r2 = 0.57, P = 0.0007, respectively). However, at any given level of left atrial tension at end of atrial systole, ACTEF was lower in idiopathic than ischemic cardiomyopathy. CONCLUSION: Left atrial systolic function is depressed in idiopathic and preserved in ischemic dilated cardiomyopathy despite similar left atrial loading conditions. This finding suggests left atrial myopathy in the former, and may be related to the differences in the response to medical treatment and clinical outcome observed between the two conditions.

Atrial Function, Left↗
PubMed2001

Assessment of LV systolic function in atrial fibrillation using an index of preceding cardiac cycles.

The clinical assessment of left ventricular (LV) systolic function during atrial fibrillation (AF) is unreliable and difficult because of beat-to-beat variability. We evaluated an index for the estimation of LV systolic function in AF that is based on the relationship between the preceding (R-R1) and prepreceding (R-R2) R-R intervals. LV Doppler stroke volume (SV), ejection fraction (EF), peak aortic flow rate (AoF) and the maximum value of the first derivative of the LV pressure curve (dP/dt(max)) were evaluated in 13 healthy open-chest dogs during triggered AF. All parameters showed a significantly strong positive linear relationship with the ratio of R-R1/R-R2 (r = 0.65, 0.74, 0.75, and 0.70 for SV, EF, AoF, and dP/dt(max), respectively). The calculated value of LV systolic parameters at R-R1/R-R2 = 1 in the linear regression line showed a good relationship and an agreement with the measured average value of the parameter over all cardiac cycles (SV, 12.1 vs. 12.8 ml; EF, 49.6 vs. 51.2%; AoF, 1.37 vs. 1.48 l/min; and dP/dt(max), 2,323 vs. 2,454 mmHg/s). Using the LV systolic parameters estimated at R-R1/R-R2 = 1 in the linear regression line allows the LV contractile function to be accurately and reproducibly evaluated during AF and obviates the less-reliable process of averaging multiple cardiac cycles.

Animals↗
PubMed2000

Prognostic value of left atrial appendage function in patients with dilated cardiomyopathy.

The purpose of the present study was to determine whether parameters of left atrial appendage (LAA) function, assessed by transesophageal echocardiography (TEE), could predict the clinical outcome in patients with dilated cardiomyopathy (DCM). Fifty-five patients (20 had ischemic cardiomyopathy; mean age, 56+/-14 years) who underwent TEE to evaluate LAA function from 1992 to 1996 were studied. After a mean follow-up period of 34+/-13 months, 16 patients died; the cause was cardiac in 14 and noncardiac in 2. Patients who died of cardiac cause had a lower LAA emptying velocity than survivors (38+/-18 vs 54+/-18 cm/s, p=0.01). There were, however, no significant differences between survivors and nonsurvivors with regard to the maximal LAA area (4.3+/-1.3 vs 4.5+/-0.9 cm2, p=0.55), minimal LAA area (2.4+/-1.1 vs 2.9+1.1 cm2, p=0.13), and LAA ejection fraction (46+/-16 vs 36+/-18%, p=0.05). On the Cox proportional hazards model analysis, LAA emptying velocity <50 cm/s (chi-square 5.9, p=0.02), LAA ejection fraction <43% (chi-square 5.6, p=0.02), female gender (chi-square 5.2, p=0.02), pulmonary artery wedge pressure > or =14 mmHg (chi-square 4.8, p=0.03), E/A ratio > or =1.3 (chi-square 4.6, p=0.03), deceleration time <148 ms (chi-square 4.6, p=0.03), and cardiothoracic ratio > or =54% (chi-square 4.3, p=0.04) were significantly related to cardiac death. The stepwise multivariate analysis revealed that LAA emptying velocity (chi-square 6.1, p=0.01) and gender (chi-square 5.4, p=0.02) were the independent predictors for outcome. In conclusion, the parameters of LAA function may be useful predictors of the clinical outcome in patients with DCM.

Adult↗
PubMed1998

Left atrial appendage function in mitral stenosis: is a group in sinus rhythm at risk of thromboembolism?

OBJECTIVE: To study the left atrial appendage (LAA) function and potential for embolization in severe mitral stenosis (MS). BACKGROUND: Patients with MS and atrial fibrillation or in sinus rhythm develop systemic emboli. LAA function has not been well studied in sinus rhythm. METHODS: Forty consecutive patients with MS (valve area < or =0.7 cm2/m2) were studied. LAA ejection fraction and peak emptying velocity were measured along with other data. RESULTS: Patients were subgrouped according to LAA Doppler flow pattern. Group I (n=13) in sinus rhythm had biphasic high velocity > or =25 cm/s. Group II (n=13) in sinus rhythm had biphasic low velocity <25 cm/s. Group III (n=14) in atrial fibrillation had multiphasic irregular flow <25 cm/s or no definite flow. The LAA ejection fraction and peak emptying velocity were strikingly different in all groups. They were lower in group II when compared to group I. Group II had intermediate risk for thromboembolism compared to Group I and III as judged by systemic embolization, spontaneous echo contrast, thrombus in left atrium and LAA. CONCLUSION: A subset of mitral stenosis in sinus rhythm at increased risk of embolization can be suspected by Doppler transesophageal echocardiographic LAA flow profile.

Adolescent↗
PubMed2004

Response of B-type natriuretic peptide to exercise in hypertensive patients with suspected diastolic heart failure: correlation with cardiac function, hemodynamics, and workload.

BACKGROUND: Diastolic heart failure (DHF) is characterized by dyspnea due to increased left ventricular (LV) filling pressures during stress. We sought the relationship of exercise-induced increases in B-type natriuretic peptide (BNP) to LV filling pressures and parameters of cardiovascular performance in suspected DHF. METHODS: Twenty-six treated hypertensive patients with suspected DHF (exertional dyspnea, LV ejection fraction >50%, and diastolic dysfunction) underwent maximal exercise echocardiography using the Bruce protocol. BNP, transmitral Doppler, and tissue Doppler for systolic (Sa) and early (Ea) and late (Aa) diastolic mitral annular velocities were obtained at rest and peak stress. LV filling pressures were estimated with E/Ea ratios. RESULTS: Resting BNP correlated with resting pulse pressure (r=0.45, P=0.02). Maximal exercise performance (4.6 +/- 2.5min) was limited by dyspnea. Blood pressure increased with exercise (from 143 +/- 19/88 +/- 8 to 191 +/- 22/ 90 +/- 10 mm Hg); 13 patients (50%) had a hypertensive response. Peak exercise BNP correlated with peak transmitral E velocity (r = 0.41, P <.05) and peak heart rate (r = -0.40, P <.05). BNP increased with exercise (from 48 +/- 57 to 74 +/- 97 pg/mL, P =.007), and the increment of BNP with exercise was associated with maximal workload and peak exercise Sa, Ea, and Aa (P <.01 for all). Filling pressures, approximated by lateral E/Ea ratio, increased with exercise (7.7 +/- 2.0 to 10.0 +/- 4.8, P <.01). BNP was higher in patients with possibly elevated filling pressures at peak exercise (E/Ea >10) compared to those with normal pressures (123 +/- 124 vs 45 +/- 71 pg/mL, P =.027). CONCLUSIONS: Augmentation of BNP with exercise in hypertensive patients with suspected DHF is associated with better exercise capacity, LV systolic and diastolic function, and left atrial function. Peak exercise BNP levels may identify exercise-induced elevation of filling pressures in DHF.

Atrial Function, Left↗
PubMed2003

Intraoperative microwave ablation in patients undergoing valvular surgery: midterm results.

AIM OF THE STUDY: To assess the safety and efficacy of intraoperative microwave ablation to restore sinus rhythm and systolic atrial function in patients undergoing valvular surgery. METHODS: Forty-one patients with atrial fibrillation (AF) underwent operations. The mean age was 61 years (range, 45- 76 years). AF was permanent in 30 patients and paroxysmal in 11. Associated cardiac procedures were mitral valve repair in 10 patients, mitral valve replacement in 12, and mitro-aortic valve replacement in 19. The microwave procedure (FLEX, AFx inc.) was performed to create an endocardial bilateral encircling isolation of the ostia of the pulmonary veins. RESULTS: There was no hospital mortality or morbidity. The mean follow-up period was 14.2 months. At follow-up, sinus rhythm was found in 34 patients (82.9%). Echocardiography results at follow-up showed no major or minor left atrial thrombosis and only a mild impairment of the systolic left atrial function. CONCLUSION: Intraoperative microwave ablation is a safe and effective treatment to restore sinus rhythm and a mildly impaired left atrial function in patients with AF undergoing cardiac surgery.

Aged↗
PubMed2001

Effects of rhythm regularization and rate control in improving left ventricular function in atrial fibrillation patients undergoing atrioventricular nodal ablation.

OBJECTIVES: To assess the relative contributions of rate control and rhythm regularization to left ventricular function in atrial fibrillation (AF) patients undergoing atrioventricular nodal ablation. This was performed by assessing the effect of ventricular rhythm regularization on left ventricular function during AF, and the effect of varying heart rate on left ventricular function after ablation. PATIENTS AND METHODS: Eleven patients with continuous AF and V/VI-R pacemakers undergoing therapeutic atrioventricular nodal ablation were studied. Preablation patients underwent two 30 min observation periods in a randomized, blinded fashion during which they were either in baseline AF (pacer set to default V/VI 50/min) or being paced using a rhythm stabilizing algorithm (RSA) designed to regularize rhythm without changing baseline ventricular rate. Six weeks after ablation, patients were again observed during the two following 30 min periods: pacing at a low clinically indicated rate (69+/-9 beats/min), and pacing at the rapid, mean preablation rate. During all observation periods, left ventricular function was measured continuously using a nuclear vest that provided validated measures of heart rate, ejection fraction, and normalized end-systolic volume (ESV) and end-diastolic (EDV) volume. RESULTS: Before ablation, RSA successfully regularized rhythm, decreasing the coefficient of variation of interbeat intervals 20+/-5% to 10+/-4% (P<0.001). The heart rate with RSA (105+/-19 beats/min) was not significantly different from the baseline AF rate (102+/-21 beats/min). Increased rhythm regularity achieved by RSA significantly improved left ventricular function, decreasing ESV from 62+/-12 units to 57+/-11 units (P=0.03), and increasing the ejection fraction from 31+/-11% to 36+/-11% (P=0.03). After ablation, at the clinically indicated low pacing rate of 69+/-9 beats/min, a much greater improvement in ejection fraction was observed, increasing to 44+/-13% (P=0.005 compared with preablation). However, rapid regular pacing at the mean preablation rate of 110+/-18 beats/min eradicated this improvement, decreasing the ejection fraction to 31+/-8% (P=0.003), and increasing ESV from 53+/-13 units to 62+/-8 units (P=0.006). CONCLUSIONS: Rhythm regularity achieved by a regularizing pacing algorithm can significantly, albeit modestly, improve left ventricular function in AF. However, more marked improvements in left ventricular function seen after ablation are primarily due to rate reduction alone.

Aged↗