Delayed improvement in exercise capacity with restoration of sinoatrial node response in patients after combined treatment with surgical repair for organic heart disease and the Maze procedure for atrial fibrillation

Sigmoidal heart rate response pattern during exercise in patients with chronic heart failure

Detailed heart rate (HR) response patterns during exercise in patients with heart failure (HF) and sinus rhythm remain uncertain. We screened consecutive patients with HF who underwent cardiopulmonary exercise tests at a large academic center from November 2013 to July 2023. HR response during exercise was statistically classified using logistic differential equation models. A total of 99 patients were included. Of them, 75 patients were assigned to "sigmoidal pattern" and the other 24 to "exponential pattern." Patients with the sigmoidal pattern were older and exhibited higher plasma B-type natriuretic peptide levels. Increases in HR and oxygen consumption (V̇o2)/kg up to the anaerobic threshold level were not different between both patterns. However, beyond the threshold, the sigmoidal pattern group showed no further increase in HR and significantly lower V̇o2/kg than their counterparts (interactions for P < 0.001). HR response during exercise in patients with heart failure and sinus rhythm was categorized into two unique groups: sigmoidal and exponential patterns. More detailed clarification of the sigmoidal pattern, potentially indicating sinus node dysfunction, should offer new clinical insights for chronotropic incompetence.NEW & NOTEWORTHY Heart rate response patterns can be classified into two groups among patients with chronic heart failure reaching maximal exertion: sigmoidal and exponential.

Sinus node function after cardiac surgery: is impairment specific for the maze procedure?

BACKGROUND

Maze surgery is a final solution for intractable atrial fibrillation (AF), but an adverse effect on postoperative sinus node function has been reported. Whether this also applies to other types of cardiac surgery is unclear.

METHODS

We assessed postoperative rhythm by means of repeated exercise tolerance testing, ambulatory electrocardiography, and non-invasive testing of autonomic function between 1 and 12 months after four types of cardiac surgery. Fourteen patients without structural cardiac disease and medically refractory AF underwent the maze III procedure, 11 patients with mitral valve disease and preoperative AF underwent valvar surgery combined with a (simplified) maze III procedure, and 8 patients with mitral valve disease in sinus rhythm (SR) underwent isolated valvar surgery. The control group consisted of eight patients with sinus rhythm who underwent coronary artery bypass surgery (CABG).

RESULTS

One month after surgery, the chronotropic response to exercise was depressed, mean heart rate was high, and heart rate variability (HRV) was low, especially after maze III, combined surgery, and isolated valvar surgery. Twelve months after surgery, moderate improvements were observed. After CABG, considerably fewer abnormalities were observed, and HRV parameters recovered to a large extent. Non-invasive testing of autonomic function indicated disturbed vagal modulation of heart rate in all three groups with atrial incision.

CONCLUSION

Thus, attenuation of HRV and vagal modulation of sinus node function are not confined to maze surgery but also apply to isolated mitral valve surgery. Atrial incision therefore appears to be crucial and presumably produces autonomic nervous damage followed by partial reinnervation. Nevertheless, cardiac surgery in general seems initially to impair sinus node function with partial recovery in the consecutive 12 months.

Electrophysiological Evaluation of the Sinus Node and the Cardiac Conduction System Following the Maze Procedure for Atrial Fibrillation

Transient sinus node dysfunction has been demonstrated by noninvasive methods following the maze procedure for atrial fibrillation (AF). However, extensive data from invasive electrophysiological studies have not been previously reported. Thirty-seven patients, mean age 54 +/- 10 years, underwent the maze (III) procedure. Electrophysiological studies with recordings of SNRT, CSNRT, AVN-ERP, point of Wenckebach block, AH, PA, and HV interval, were performed preoperatively and 6 and 15 months postoperatively. Induction of atrial flutter/AF was attempted postoperatively. Based on electrophysiological study evaluation, the maze (III) procedure did not cause permanent damage to the sinus node in any patient with a documented normal sinus node function preoperatively (CSNRT max 541 +/- 210 vs 587 +/- 437 ms, P = 0.26). Postoperative AV node function was normal in all patients with a documented normal AV node function before surgery. One patient had an iatrogenic third degree AV block. There was no difference in PA or HV interval after surgery. Sustained atrial tachyarrhythmias could be induced in 5 patients, of whom 4 developed permanent AF/atrial flutter late after surgery. At late follow-up, (mean 45 months), 27 (73%) patients were in sinus rhythm, 5 (13%) patients had permanent pacing, and 5 patients had recurrent AF requiring His bundle ablation (n = 2) or medical treatment (n = 3). Based on electrophysiological studies, the maze (III) procedure does not cause permanent damage to the sinus or AV nodes or to the right atrial and His-Purkinje conduction systems. Electrophysiological study evaluation may predict the need for postoperative pacemaker. Induction attempts of atrial arrhythmias may predict future recurrences and guide therapeutic efforts.

Mechanism of improvement in exercise capacity after the maze procedure combined with mitral valve surgery

OBJECTIVE

To clarify the mechanism of improvement in exercise capacity after the maze procedure.

DESIGN

Retrospective study.

SETTING

Tertiary referral centre.

PATIENTS

26 patients (mean (SD) age 57 (9) years) with atrial fibrillation (AF) and mitral valve disease were studied with echocardiography and cardiopulmonary exercise testing before and after the maze procedure combined with mitral valve surgery. Of these, eight had persistent AF and 18 had restored sinus rhythm (SR) by the surgery. Six patients (mean (SD) age 59 (12) years) with AF undergoing mitral valve surgery without the maze procedure who had cardiopulmonary exercise testing before and after the surgery formed the control group.

MAIN OUTCOME MEASURES

Echocardiographic parameters of atrial function were measured from transmitral flow recordings. Peak oxygen uptake (VO2) and the slope of the relation between VO2 and workload (ratio of DeltaVO2 to Delta work) were determined as indices of exercise capacity.

RESULTS

The degree of improvements in peak VO2 and the ratio of DeltaVO2 to Delta work after the mitral valve surgery was comparable between the maze and control group. It was also comparable between patients with and those without successfully restored SR after the maze procedure. The degree of the increase in peak VO2 correlated with the change in left atrial diameter (r = -0.40, p = 0.047) but atrial contraction did not correlate with the increase.

CONCLUSIONS

Improvement in exercise capacity may not be caused by restored SR and atrial contraction but may at least partly relate to the reduction of left atrial size and improvement of haemodynamic variables by the surgery.

Acute and chronic effects of surgical thromboendarterectomy on exercise capacity and ventilatory efficiency in patients with chronic thromboembolic pulmonary hypertension

OBJECTIVE

To assess acute and chronic effects of surgical thromboendarterectomy on exercise capacity and ventilatory efficiency in patients with chronic thromboembolic pulmonary hypertension (CTEPH).

DESIGN

Cardiopulmonary exercise testing was performed in 20 patients with CTEPH before thromboendarterectomy (baseline), one month after (early phase), and four months after (late phase). Peak oxygen uptake (peak VO(2)) and the ventilatory response to carbon dioxide production (VE-VCO(2) slope) were measured for assessment of exercise capacity and ventilatory efficiency. Right heart catheterisation was performed in all patients before and one month after surgery.

RESULTS

Baseline peak VO(2) decreased and VE-VCO(2) slope increased along with the increase in pulmonary vascular resistance in patients with CTEPH. After thromboendarterectomy, the VE-VCO(2) slope decreased greatly from baseline to the early phase (mean (SD), 50 (9) to 37 (7), p < 0.05) and reached a steady level thereafter. In contrast, a continued increase in peak VO(2) was noted from the early to the late phase (16.9 (4.1) to 21.1 (5.0) ml/kg/min, p < 0.05). The decrease in the VE-VCO(2) slope from baseline to the early phase, but not the increase in peak VO(2), correlated strongly with the decrease in pulmonary vascular resistance after surgery (r = 0.75, p < 0.01).

CONCLUSIONS

Thromboendarterectomy may cause an immediate improvement in ventilatory efficiency, possibly through its beneficial haemodynamic effects. In contrast, exercise capacity may continue to improve towards the late phase, reflecting peripheral adaptation to exercise.

Acute and chronic effects of surgical thromboendarterectomy on exercise capacity and ventilatory efficiency in patients with chronic thromboembolic pulmonary hypertension

OBJECTIVE

To assess acute and chronic effects of surgical thromboendarterectomy on exercise capacity and ventilatory efficiency in patients with chronic thromboembolic pulmonary hypertension (CTEPH).

DESIGN

Cardiopulmonary exercise testing was performed in 20 patients with CTEPH before thromboendarterectomy (baseline), one month after (early phase), and four months after (late phase). Peak oxygen uptake (peakV˙o2) and the ventilatory response to carbon dioxide production (V˙e-V˙co2 slope) were measured for assessment of exercise capacity and ventilatory efficiency. Right heart catheterisation was performed in all patients before and one month after surgery.

RESULTS

Baseline peakV˙o2 decreased andV˙e-V˙co2 slope increased along with the increase in pulmonary vascular resistance in patients with CTEPH. After thromboendarterectomy, theV˙e-V˙co2 slope decreased greatly from baseline to the early phase (mean (SD), 50 (9) to 37 (7), p < 0.05) and reached a steady level thereafter. In contrast, a continued increase in peak V˙o2 was noted from the early to the late phase (16.9 (4.1) to 21.1 (5.0) ml/kg/min, p < 0.05). The decrease in theV˙e-V˙co2 slope from baseline to the early phase, but not the increase in peakV˙o2, correlated strongly with the decrease in pulmonary vascular resistance after surgery (r = 0.75, p < 0.01).

CONCLUSIONS

Thromboendarterectomy may cause an immediate improvement in ventilatory efficiency, possibly through its beneficial haemodynamic effects. In contrast, exercise capacity may continue to improve towards the late phase, reflecting peripheral adaptation to exercise.

Open-heart endocardial radiofrequency ablation: an alternative to incisions in Maze surgery

BACKGROUND

Radiofrequency (RF) ablation produces transmural atrial lesions in vitro, and may provide advantages over incisions currently used in maze surgery. This study examines the feasibility, safety, and efficacy of open-heart endocardial RF ablation.

METHODS

Eighteen sheep (42.8 +/- 4.4 kg, age < 2 years) underwent left thoracotomy with placement of pacing leads on a pulmonary vein and the left atrial dome. On cardiopulmonary bypass, lesions were made using incision and suture or a novel RF ablation device in three sites: PVC = circle excluding pulmonary veins, IAB = line across the interatrial bundle, SVC = line from the superior to the inferior vena cava. Pacing across the PVC lesion was attempted to assess the completeness of each lesion. Preselected animals (incision n = 4, RF n = 5) were recovered and pacing attempts were repeated at 1 month. After sacrifice, hearts were sectioned and measured for lesion size and completeness.

RESULTS

RF ablation lesions took less time to create (total bypass time: RF 51.8 min vs incision 106 min, P < 0.001). No evidence of thromboembolism, atrial rupture, or coronary sinus thrombosis was seen. All PVC lesions were complete as demonstrated by the inability to pace across them. Stained sections demonstrated that acutely studied incision lesions were thinner than RF lesions; however, all lesions were transmural and similar in width at 1 month.

CONCLUSIONS

RF ablation consistently created transmural lesions more quickly than the incision and suture method and without additional complications. Endocardial RF ablation appears to be a simple and effective alternative to surgical incisions during open-heart atrial Maze procedures.

Effect of mitral valve surgery on exercise capacity, ventricular ejection fraction and neurohormonal activation in patients with severe mitral regurgitation

OBJECTIVES

The purpose of this study was to prospectively investigate the effects of surgical correction of mitral regurgitation (MR) on exercise performance, cardiac function and neurohormonal activation.

BACKGROUND

Little is known about the effect of surgical correction of MR on functional status or on neurohormonal activation.

METHODS

Cardiopulmonary exercise test, radionuclide angiography and blood samples for assessment of neurohormonal status were obtained in 40 patients with nonischemic MR before and within one year (216+/-80 days) after surgery. Twenty-four patients underwent mitral valve repair (MVr), and 16 underwent valve replacement (VR) with anterior chordal transection.

RESULTS

Despite an improvement in New York Heart Association functional class, exercise performance did not change (peak oxygen consumption: 19.3+/-6.1 to 18.5+/-5.6 ml/kg/min, percentage of maximal predicted oxygen consumption: 79.5+/-18.2% to 76.8+/-16.9%). After surgery, left ventricular (LV) ejection fraction (EF) decreased (64.2+/-10.3% to 59.9+/-11.4%, p = 0.003) while right ventricular (RV) EF increased (41.4+/-9.6% to 44.7+/-9.5%, p = 0.03). Left ventricular EF did not change after MVr (64.3+/-11.5% to 61.5+/-12.2%), but RVEF improved (40.4+/-9.2% to 46.0+/-10.0%, p = 0.02). In contrast, VR was associated with an impairment of LV function in the apicolateral area and a decrease in LVEF (64.1+/-8.5% to 57.4+/-10.0%, p = 0.01), whereas RVEF did not change (42.9+/-10.3% to 42.8+/-8.6%). Moreover, there was only a slight decrease in neurohormonal activation after surgery.

CONCLUSIONS

Despite an improvement in symptomatic status, exercise performance was not improved seven months after either MVr or VR for MR, and neurohormonal activation persisted. Compared with MVr, VR resulted in a significant impairment of cardiac function in this study.

The Maze operation for treatment of atrial fibrillation. Early clinical experience in a Scandinavian institution

The Maze operation is a potentially curative surgical option in patients with disabling atrial fibrillation (AF) refractory to conventional treatment. The aim of this study was to evaluate the initial 4-year Maze experience in our institution. The study included 26 patients (19 males, mean age 55 years) who had undergone the Maze (III) operation between 1994 and 1998. Nine patients had surgery for concomitant heart disease. Follow-up was 3-55 (median 18) months. No deaths or neurological complications occurred; 22 patients are at present in regular sinus-, or junctional rhythm, 2 patients have permanent atrial pacing for symptomatic sinus node dysfunction, and 2 patients have had persistent AF, post surgery. Sinus node dysfunctions were detected in five patients, though not requiring pacemakers. Out of the total 26 patients, 23 are free of anti-arrhythmic drugs. Echocardiographic signs of left atrial contraction were recorded in 50% of the patients. The Maze operation offers a safe alternative to conventional therapy, with attractive results justifying expansion in the use of this treatment for AF.

Clinical correlates and prognostic significance of six-minute walk test in patients with primary pulmonary hypertension. Comparison with cardiopulmonary exercise testing

The six-minute walk test is a submaximal exercise test that can be performed even by a patient with heart failure not tolerating maximal exercise testing. To elucidate the clinical significance and prognostic value of the six-minute walk test in patients with primary pulmonary hypertension (PPH), we sought (1) to assess the relation between distance walked during the six-minute walk test and exercise capacity determined by maximal cardiopulmonary exercise testing, and (2) to investigate the prognostic value of the six-minute walk test in comparison with other noninvasive parameters. The six-minute walk test was performed in 43 patients with PPH, together with echocardiography, right heart catheterization, and measurement of plasma epinephrine and norepinephrine. Symptom-limited cardiopulmonary exercise testing was performed in a subsample of patients (n = 27). Distance walked in 6 min was significantly shorter in patients with PPH than in age- and sex-matched healthy subjects (297 +/- 188 versus 655 +/- 91 m, p < 0. 001). The distance significantly decreased in proportion to the severity of New York Heart Association functional class. The distance walked correlated modestly with baseline cardiac output (r = 0.48, p < 0.05) and total pulmonary resistance (r = -0.49, p < 0. 05), but not significantly with mean pulmonary arterial pressure. In contrast, the distance walked correlated strongly with peak V O(2) (r = 0.70, p < 0.001), oxygen pulse (r = 0.57, p < 0.01), and V E-VCO(2) slope (r = -0.66, p < 0.001) determined by cardiopulmonary exercise testing. During a mean follow-up period of 21 +/- 16 mo, 12 patients died of cardiopulmonary causes. Among noninvasive parameters including clinical, echocardiographic, and neurohumoral parameters, only the distance walked in 6 min was independently related to mortality in PPH by multivariate analysis. Patients walking < 332 m had a significantly lower survival rate than those walking farther, assessed by Kaplan-Meier survival curves (log-rank test, p < 0.01). These results suggest that the six-minute walk test, a submaximal exercise test, reflects exercise capacity determined by maximal cardiopulmonary exercise testing in patients with PPH, and it is the distance walked in 6 min that has a strong, independent association with mortality.

Comparative efficacy of the maze procedure for restoration of atrial contraction in patients with and without giant left atrium associated with mitral valve disease

OBJECTIVES

We sought to determine the effectiveness of the maze procedure for restoring atrial contraction in patients with and without giant left atrium (GLA).

BACKGROUND

Although the maze procedure has been reported to be effective for refractory atrial fibrillation, it is unknown whether this procedure can restore effective atrial contraction in patients with GLA.

METHODS

Nineteen patients with and 32 patients without GLA were studied with Doppler echocardiography before and after the maze procedure. Peak velocity and the time-velocity integral of the left ventricular diastolic filling wave during atrial contraction (A wave) and the atrial filling fraction calculated as the ratio of the time-velocity integral of the A wave to that of total diastolic filling were compared between patients with and without GLA. A peak A wave velocity > or =10 cm/s was considered to indicate echocardiographic evidence of effective atrial contraction.

RESULTS

Regular rhythm with P waves was restored in 10 patients (53%) with and 26 (81%, p < 0.05) without GLA. Four patients (21%) with and 21 patients (66%, p < 0.01) without GLA showed effective atrial contraction by echocardiography. Once atrial contraction was resumed, the degree of atrial contraction was comparable between patients with and without GLA (17+/-5% vs. 17+/-4% for atrial filling fraction at 12 months, respectively).

CONCLUSIONS

Although most patients without GLA had restored atrial contraction by the maze procedure, it was resumed in fewer patients with GLA. However, once atrial contraction was resumed, the degree of atrial contraction was comparable between patients with and without GLA. Therefore, the maze procedure may be an option in selected patients with GLA.

Electrophysiologic changes in arrhythmogenic substrate following the maze procedure in patients with lone and paroxysmal atrial fibrillation

Although the Maze procedure is highly successful in restoring sinus rhythm in patients with atrial fibrillation (AF), the electrophysiologic changes that occur after the Maze procedure and its mechanism of action are still unclear. The aims of the present study were to examine the electrophysiologic changes that occur in the arrhythmogenic substrate after the Maze procedure and to evaluate the mechanism by which it prevents lone and paroxysmal AF. The modified Maze procedure was performed in 6 patients (6 men, mean age 47 +/- 7 years) with lone and paroxysmal AF. Electrophysiologic studies were performed before and 35 +/- 8 days after the Maze procedure. Atrial mapping during sinus rhythm revealed that atrial activation propagated smoothly in a concentric circle from the sinus node to other regions in the right atrium and into the coronary sinus before the Maze procedure. Following the Maze procedure, atrial activation propagated selectively through routes produced by incisions or cryoablations in all 6 patients. In addition, double and triple potentials were recorded in regions where conduction blocks were created by the Maze procedure. Neither sinus node function nor AV conduction was changed following the Maze procedure. The Maze procedure did not affect the atrial effective refractory period or the zone of fragmented atrial activity, although the conduction delay zone was increased significantly (p < 0.05). AF was inducible in all 6 patients before the Maze procedure, whereas it was not inducible in any patients after the Maze procedure. The Maze procedure is effective in preventing AF without affecting sinus node function and AV conduction. Intra-atrial conduction block produced by incisions or cryoablations contributes to the prevention of AF.

Delayed improvement of autonomic nervous abnormality after the Maze procedure: time and frequency domain analysis of heart rate variability using 24 hour Holter monitoring

OBJECTIVE

To analyse heart rate variability in patients with atrial fibrillation after the Maze procedure, to investigate whether the procedure damages the cardiac autonomic fibres supplying the sinus node.

DESIGN AND PATIENTS

Time and frequency domain analyses of RR variability were performed using 24 hour Holter monitoring one month after surgery in 12 patients with atrial fibrillation who underwent the Maze procedure (Maze group) and in seven patients who underwent cardiac surgery without the Maze procedure (control group). Mean RR intervals (mRR) and the standard deviation of successive RR intervals (SDRR) were determined by time domain analysis, and high frequency (HF), low frequency (LF), and total power (TP) spectral components of RR variability were calculated by frequency domain analysis. Holter monitoring was also performed at six and 12 months after cardiac surgery in the Maze group.

RESULTS

Circadian variation (mean (SD)) in mRR (daytime to night time difference: 119 (60) v 302 (143) ms), SDRR (daytime: 8.4 (3.3) v 37.0 (12.0) ms), TP (daytime: 46.7 (16.0) v 171.8 (30.4) ms), HF (daytime: 19.6 (9.9) v 36.7 (7.1) ms2), and LF/HF (daytime: 0.31 (0.07) v 1.18 (0.46)) was decreased in the Maze group at one month compared with the control group (p < 0.01), but showed improvement at six and 12 months (p < 0.05).

CONCLUSIONS

Surgery combined with the Maze procedure markedly suppressed the circadian variation of heart rate over a 24 hour period within one month after surgery, mainly because of damage to the innervation of the sinus node. However, at six and 12 months there was restoration of circadian variation, probably as the result of reinnervation of the sinus node.

Long-term follow-up of corridor operation for lone atrial fibrillation: evidence for progression of disease?

INTRODUCTION

Currently, surgery- and catheter-mediated ablation is applied when drug refractoriness of atrial fibrillation is evident, although little is known about the long-term incidence of new atrial arrhythmia and the preservation of sinus node function.

METHODS AND RESULTS

To address this issue, 30 patients with successful corridor surgery for lone paroxysmal atrial fibrillation and normal preoperative sinus node function were followed in a single outpatient department. Five years after surgery, the actuarial proportion of patients with recurrence of atrial fibrillation arising in the corridor was 8% +/- 5%, with new atrial arrhythmias consisting of atrial flutter and atrial tachycardia in the corridor 27% +/- 8%, and with incompetent sinus node requiring pacing therapy 13% +/- 6%. Right atrial transport was preserved in 69% of the patients without recurrence of atrial fibrillation and normal sinus node function. Stroke was documented in two patients.

CONCLUSIONS

Corridor surgery for atrial fibrillation is a transient or palliative treatment instead of a definitive therapy for drug refractory atrial fibrillation. This observation strongly affects patient selection for this intervention and constitutes a word of caution for other, nonpharmacologic interventions for drug refractory atrial fibrillation.

Electrocardiographic nature of restored sinus rhythm after Cox maze procedure in patients with chronic atrial fibrillation who also had other cardiac surgery

OBJECTIVE

To characterise heart rate variability and high frequency components of restored sinus rhythm after the maze procedure. The maze procedure for chronic atrial fibrillation may prevent thrombotic events and improve the quality of life. However, the electrocardiographic nature of restored sinus rhythm after the maze procedure has not been fully elucidated.

PATIENTS AND METHODS

Between March 1993 and August 1995, 104 consecutive patients undergoing the maze procedure in combination with other cardiac surgery were studied. There were 100 long-term survivors (78 with mitral valve disease, 9 with aortic valve disease, 8 with congenital heart disease, and 5 others). Twenty age-matched patients with mitral valve disease who were in normal sinus rhythm preoperatively were enrolled as a control group. 30 days after surgery, the presence of arrhythmias and the circadian changes of heart rate variability were estimated by ambulatory electrocardiographic monitoring and the filtered P duration was evaluated by signal-averaged electrocardiogram.

RESULTS

Restoration of sinus rhythm was observed in 73 of 100 cases. Subjects were classified into three groups according to their postoperative ambulatory electro-cardiographic monitoring findings: patients in group 1 (n = 73) (1a: 58 regular sinus rhythm; 1b: 15 sinus rhythm with frequent premature atrial contractions (> 1000/day); patients in group 2 (n = 21) still had persistent atrial fibrillation; and patients in group 3 (n = 6) required permanent pacemaker implantation because of sick sinus syndrome. The success rate of restoration of sinus rhythm was 88.3% if left atrial diameter was small (< 65 mm). Circadian changes in the low frequency to high frequency power ratio in group 1a were significantly diminished compared with control group (P < 0.01). Furthermore, the filtered P duration in group 1a (150 (20) ms) and group 1b (158 (23) ms) were longer than in the control group (122 (11) ms) (P < 0.01).

CONCLUSIONS

The maze procedure may result in a decreased sinus response and non-uniform transmission of impulses in the atrium.